A FISH AND TETRAPOD FAUNA FROM ROMER’S GAP
PRESERVED IN SCOTTISH TOURNAISIAN
FLOODPLAIN DEPOSITS
by BENJAMIN K. A. OTOO1,5 ,* , JENNIFER A. CLACK1,*, TIMOTHY R.
SMITHSON1, CARYS E. BENNETT2, TIMOTHY I. KEARSEY3 and MICHAEL I.
COATES4
1University Museum of Zoology Cambridge, Downing Street, Cambridge, CB2 3EJ, UK; jac18@cam.ac.uk, ts556@cam.ac.uk
2Department of Geology, University of Leicester, Leicester, LE1 7RH, UK; ceb28@leicester.ac.uk
3British Geological Survey, The Lyell Centre, Research Avenue South, Edinburgh, EH14 4AP, UK; timk1@bgs.ac.uk
4Committee on Evolutionary Biology, University of Chicago, Culver Hall, 1025 East 57th Street, Chicago, IL 60637, USA; mcoates@uchicago.edu
5Current address: Committee on Evolutionary Biology, University of Chicago, Culver Hall, 1025 East 57th Street, Chicago, IL 60637, USA; botoo@uchicago.edu
*Corresponding authors
Typescript received 15 December 2017; accepted in revised form 20 July 2018
Abstract: The end-Devonian mass extinction has been
framed as a turning point in vertebrate evolution, enabling
the radiation of tetrapods, chondrichthyans and
actinopterygians. Until very recently ‘Romer’s Gap’ ren-
dered the Early Carboniferous a black box standing
between the Devonian and the later Carboniferous, but
now new Tournaisian localities are filling this interval.
Recent work has recovered unexpected tetrapod and lung-
fish diversity. However, the composition of Tournaisian
faunas remains poorly understood. Here we report on a
Tournaisian vertebrate fauna from a well-characterized, nar-
row stratigraphic interval from the Ballagan Formation
exposed at Burnmouth, Scotland. Microfossils suggest
brackish conditions and the sedimentology indicates a low-
energy debris flow on a vegetated floodplain. A range of
vertebrate bone sizes are preserved. Rhizodonts are repre-
sented by the most material, which can be assigned to two
taxa. Lungfish are represented by several species, almost all
of which are currently endemic to the Ballagan Formation.
There are two named tetrapods, Aytonerpeton and Diplo-
radus, with at least two others also represented. Gyracanths,
holocephalans, and actinopterygian fishes are represented by
rarer fossils. This material compares well with vertebrate
fossils from other Ballagan deposits. Faunal similarity analy-
sis using an updated dataset of Devonian–Carboniferous
(Givetian–Serpukhovian) sites corroborates a persistent
Devonian/Carboniferous split. Separation of the data into
marine and non-marine partitions indicates more Devo-
nian–Carboniferous faunal continuity in non-marine set-
tings compared to marine settings. These results agree with
the latest fossil discoveries and suggest that the Devonian–
Carboniferous transition proceeded differently in different
environments and among different taxonomic groups.
Key words: Romer’s Gap, Tournaisian, tetrapod, flood-
plain, Carboniferous, rhizodont.
ROMER’s Gap (Romer 1956; Coates & Clack 1995) is a
hiatus in the non-marine fossil record that currently
spans the Tournaisian stage of the Carboniferous (~359–
345 Ma). Named for the paucity of tetrapod fossils
throughout this interval, the gap has long obscured clado-
genic events and ecological transitions implied by differ-
ences between the few, mostly aquatic, limbed forms
present at the end of the Devonian and the diverse and
disparate tetrapods known from the Visean (Wellstead
1982; Clarkson et al. 1994; Pardo et al. 2017). What little
we know of Tournaisian tetrapods is drawn from not
much more than isolated bones and fragments from
localities such as Blue Beach in Canada (Anderson et al.
2015), but with the notable exception of the unique, sub-
stantial and partly articulated skeleton of Pederpes from
Scotland (Clack & Finney 2005). However, the challenge
presented by Romer’s Gap extends beyond tetrapods. Few
Tournaisian fish localities have been known until recently
(Clarkson 1985; Long 1989; Sallan & Coates 2010; Man-
sky & Lucas 2013; Sallan & Galimberti 2015; Mickle 2017,
Richards et al. 2018), and these, too, appear impoverished
relative to subsequent Visean faunas.
It follows that all three major living vertebrate divi-
sions, actinopterygians (Sallan 2014; Giles et al. 2017),-
chondrichthyans (Coates et al. 2017, 2018), and tetrapods
(Clack et al. 2016; Pardo et al. 2017) underwent major
© 2018 The Authors.
Palaeontology published by John Wiley & Sons Ltd on behalf of The Palaeontological Association.
doi: 10.1111/pala.12395 1
This is an open access article under the terms of the Creative Commons Attribution License,
which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
[Palaeontology, 2018, pp. 1–29]
radiations within this key interval. Moreover, it seems
likely that these radiations occurred opportunistically, to
refill ecological space in the aftermath of serial extinction
events that occurred close to end of the Devonian (Sallan
& Coates 2010; Sallan & Galimberti 2015). But the
absence of a substantial record of Tournaisian fossil verte-
brates obscures the timing and true phylogenetic pattern
of the Devonian–Carboniferous transition. It remains
unclear whether these large-scale post-extinction diversifi-
cations arose from short (Tournaisian) or long (Devo-
nian) fuses. We have almost no perspective on the
multiple ecological transitions that took place at this time,
especially the ongoing vertebrate invasions of non-marine
environments including the likely multiple episodes of
terrestrialization within the Tetrapoda. Moreover, the
hypothesized abruptness of the end-Devonian mass
extinction (Hangenberg event) (Sallan & Coates 2010)
and an inferred Lilliput effect (Sallan & Galimberti 2015)
deserve to be tested. Already, Tournaisian tetrapod dis-
coveries include a mix of morphologies (Anderson et al.
2015) that are distributed across multiple nodes in recent
phylogenetic analyses (Clack et al. 2016) and a recently-
recognized Tournaisian radiation in lungfish (Smithson
et al. 2015) contradicts a historical narrative of post-
Devonian decline and stasis.
These various observations raise the possibility that the
Devonian–Carboniferous divide recovered by Sallan &
Coates (2010) might not be expressed in the same way
across all environments, particularly given the uneven dis-
tribution of end-Devonian diversity loss among taxo-
nomic groups (Sallan & Coates 2010). Thus, there may be
discernable time/environment associations, with different
levels of taxonomic/ecological continuity across the Devo-
nian–Carboniferous boundary. However, widespread
euryhalinity among Devonian–Carboniferous vertebrates
(
O Gog
ain et al. 2016; Goedert et al. 2018) may support
the hypothesis of a cosmopolitan post-extinction fauna in
the Tournaisian (Friedman & Sallan 2012).
Here we describe the vertebrate fossil fauna from the
Tournaisian-age Ballagan Formation exposed on the
beach at Burnmouth, Scotland. The fossils come from a
1 m stratigraphic interval. These new data, along with
those from the Blue Beach locality (Anderson et al. 2015),
are added to the dataset of Sallan & Coates (2010) to test
their conclusions of a Devonian/Carboniferous faunal
divide against new Tournaisian data.
GEOLOGICAL CONTEXT
The Ballagan Formation crops out in northern England
and the Midland Valley of Scotland. It has previously
been referred to as the Cementstone Group in England
and the lower part of the Calciferous Sandstone Measures
in Scotland (Greig 1988), and probably spans the whole
of the Tournaisian (Smithson et al. 2012). The Ballagan is
characterized by alternating dolostones (‘cementstones’),
palaeosols, sandstones and siltstones. The last of these
have been identified as an important facies for preserving
fossils both in the Ballagan and elsewhere in the Car-
boniferous (Bennett et al. 2016; Kearsey et al. 2016). The
Ballagan has produced isolated (macro)fossils in the past
(Clack 2002) but its full fossiliferous potential has only
been realized recently via the TW:eed project (http://tetra
pods.org/), which has also increased our sedimentological
and palaeoenvironmental knowledge of the formation
(Smithson et al. 2012, 2015; Bennett et al. 2016, 2017;
Clack et al. 2016; Kearsey et al. 2016).
The entire Ballagan Formation is exposed at Burn-
mouth, Scotland (Fig. 1), as just over 500 m of vertically
dipping beds. Most of the tetrapod fossils at Burnmouth
occur from 332–383 m, though there are isolated bones
known from lower horizons (see Clack et al. 2016, fig.
6a). The greatest concentration comes from a ~50 cm
span within a highly-sampled 1 m interval at 340.5 m
originally discovered by TRS. This 1 m interval contains
the Ossirarus and Aytonerpeton beds (Clack et al. 2016)
and is here designated the Tetrapod Interval Metre, or
TIM (Fig. 2).
The Ballagan Formation comprises 10 facies and three
facies associations, each of which occur throughout the
formation: (1) fluvial facies association; (2) overbank
facies association; and (3) saline-hypersaline lake facies
association (Bennett et al. 2016). The sandy siltstone
facies occurs within the overbank facies association, and
is characterized as matrix-supported, ungraded siltstones,
with millimetre-sized siltstone and very fine sandstone
lithic clasts. This facies is a key characteristic of the Balla-
gan Formation, with 71 beds reported from the Burn-
mouth succession. Beds are randomly distributed through
the succession, laterally variable, and range in thickness
from 0.2 to 140 cm (Bennett et al. 2016). 71% of beds
overlie palaeosols or desiccation cracks and often occur in
stacked sequences with palaeosols. The palaeosols are
rooted red, green or grey siltstones and only rarely con-
tain small carbonate nodules (Kearsey et al. 2016). They
represent a range of floodplain environments including
woodland (vertisols), scrubby vegetation (entisols, incepti-
sols) and saline marshes (gleyed inceptisols).
The sandy siltstone beds are interpreted as having
formed as a cohesive flow resulting from monsoonal-type
flood events, picking up sediment clasts and fossil mate-
rial from desiccated floodplain lakes and vegetated
ground as the flood travelled (Bennett et al. 2016). The
beds either deposited material in depressions on a dry
vegetated floodplain, or into existing floodplain lakes or
pools. The high degree of vertebrate and invertebrate fos-
sil articulation within these units indicates a local origin
2 PALAEONTOLOGY
and minimal transport of the fossil components (Bennett
et al. 2016).
MATERIAL AND METHOD
Collection and preparation
A detailed sedimentary log of the section in the cliff expo-
sure was drawn in October 2012 and enhanced by addi-
tional observations gathered from summer fieldwork in
2013–2016. Samples were taken approximately every
20 cm through the studied interval and their fossil con-
tent was examined under a Leica binocular microscope at
the University of Leicester. Initial fossil observations from
all sandy siltstone beds identified at Burnmouth (includ-
ing those in this interval) are recorded in Bennett et al.
(2016, appendix 1). To obtain a high-resolution sedimen-
tological and palaeontological data set, the TIM was sam-
pled by removing a 1 m 9 1 m 9 30 cm block from the
foreshore. This was recovered in June 2013, with permis-
sion from Crown Estate Scotland and Scotland Natural
Heritage. This sample, was divided into four equal units
25 9 25 9 30 cm long-wide-deep, named A–D from left
to right and 1–3 from top to bottom. From here the fossil
content was recorded. Macrofossil material presented here
includes samples collected from the TIM by S. P. Wood
in 2007, TRS in 2006–2008, and by the TW:eed team in
2012–2013, and material prepared from the metre-square
block in 2014–2015 by SPW, TRS, JAC and BKAO. Much
of this collecting was done approximately 18 m laterally
seaward from the metre square.
The fossils of the TIM were initially revealed using a
200 g hammer and cold chisel. These were then prepared
using a mounted tungsten-carbide needle, under binocu-
lar microscopes with up to 950 objectives. Dilute Par-
aloid B72 was used as a specimen consolidant during
preparation. Specimen photography was carried out using
a Panasonic Lumix DMC-LZ5 and a Sony Cyber-shot
DSC-RX100 III digital camera and a Dino-Lite Pro/Pro2
AD4000 AM4000 digital microscope. Image processing
was carried out in Adobe Photoshop CS6. Select speci-
mens were CT scanned using a Nikon Metrology XT H
225 ST High Resolution CT Scanner at the University of
Cambridge Biotomography Centre. The following param-
eters were used: isotropic voxel size 0.0609 mm, 1080
projections, no filter, X-ray 120 kV, 125 lA, 1789 slices,
1000 ms per slice exposure, 24 dB gain. 3-D sectioning
was carried out in Mimics Innovation Suite (Materialise,
Leuven, Belgium; https://www.materialise.com/en/medica
l/software/mimics). Additional rendering and manipula-
tion of objects was done in Meshlab (Visual Computing
Lab-ISTI-CNR; http://www.meshlab.net/).
Micopalaeontological analysis
Three beds from the TIM were selected for micropalaeon-
tological processing from three different facies (Fig. 3):
(1) palaeosol facies, a gleyed inceptisol that occurs just
below the main fossil-bearing unit; (2) sandy siltstone
facies, within the tetrapod-bearing unit; (3) laminated
grey siltstone facies, with desiccation cracks containing
sandy siltstone, above the tetrapod-bearing unit. All three
facies are part of the overbank facies association (Bennett
et al. 2016). Approximately 15–20 g of each sample was
processed overnight in a 5% solution of hydrogen perox-
ide, then wet sieved at 1000, 425, 250, 125, 65 lm frac-
tions and oven dried at 40°C. All fossil specimens present
F IG . 1 . A, map showing English/Scottish border. B, the
detailed location of the study area at Burnmouth. Modified from
Kearsey et al. (2016).
OTOO ET AL . : SCOTTISH TOURNAIS IAN VERTEBRATE FAUNA 3
4 PALAEONTOLOGY
were picked from the 1000, 425, 250 and 125 lm frac-
tions and total counts recorded (Otoo et al. 2018,
micropalaeontology data). Three standard-sized, polished
thin sections (20 lm thick) of these beds were examined
on a Leica petrographic microscope at the University of
Leicester.
Faunal analyses
Sallan & Coates (2010) compiled a large dataset of
gnathostome vertebrate fossil occurrences from the Mid-
dle Devonian (Givetian stage) through to the end of the
Early Carboniferous (Serpukhovian stage). This dataset
was updated to include new data from the Burnmouth
TIM fauna (named ‘Burnmouth-TIM’ in the analyses),
Blue Beach (Brazeau 2005; Mansky & Lucas 2013;
Anderson et al. 2015) and Mill Hole (Carpenter et al.
2014), as well as revisions of rhizodont taxonomy (Johan-
son & Ahlberg 2001; Jeffery 2006). Localities were charac-
terized as marine, marginal or non-marine, with more
specific environmental categories based on descriptions in
the original dataset and literature. Both raw diversity
(number of species in each taxonomic group) and relative
diversity (taxon diversity relative to locality diversity)
were analysed. This accounted for the effects of assem-
blage size and provided comparability with the Sallan &
Coates (2010) analyses.
All faunal analyses were run in PAST (Hammer
2015). In each analysis, sites were not grouped a priori
by stage or environment. Correspondence analysis (CA)
was used to recover any time–environment faunal asso-
ciations and investigate which taxa were driving similari-
ties and differences between faunas. Diversity datasets
F IG . 3 . Tetrapod-bearing bed exposure at Burnmouth. A, photograph of the cliff section, with position of the Ossirarus, Aytonerpeton
and microfossil sample beds (1–3). B, the Ossirarus-bed exposed on the foreshore at Burnmouth. 1–3, thin section scans of beds that
were processed for microfossils: 1, palaeosol; 2, sandy siltstone; 3, laminated grey siltstone. Scale bars represent: 10 cm (A); 5 cm (B);
5 mm (1–3). Colour online.
F IG . 2 . Sedimentary log of the tetrapod-bearing beds at Burnmouth. The 250 cm-height log represents the exposure on the fore-
shore, while the detailed log covers part of the sampled metre square. Fossil symbols illustrated on the metre square relate to those
identified in hand specimen and from microfossil samples.
OTOO ET AL . : SCOTTISH TOURNAIS IAN VERTEBRATE FAUNA 5
are presented in Otoo et al. (2018). Non-parametric
multidimensional scaling (NMDS) was used to charac-
terize faunal similarity quantitatively and graphically
using Bray–Curtis distance, a faunal similarity metric
(Bray & Curtis 1957).
Institutional abbreviations. UMZC, University of Cambridge
Museum of Zoology, UK; NMS, National Museums Scotland,
Edinburgh, Scotland, UK; GLAHM, Hunterian Museum, Glas-
gow, Scotland, UK; YMP, Yale Peabody Museum of Natural His-
tory, New Haven, Connecticut, USA; NSM, Nova Scotia
Museum of Natural History, Halifax, Nova Scotia, Canada;
NBMG, New Brunswick Museum (Geology), Saint John, New
Brunswick, Canada.
SYSTEMATIC PALAEONTOLOGY
Macrofossil distribution
The greatest portion of macrofossils from the TIM come
from section C (Fig. 2). The microfossil assemblage of
Sample 3 (see Microfossil results) occurs within the same
lithology as the TIM and has similar microfossil content
to the TIM macrofossil content. However, macrofossils
have been found elsewhere within the TIM, including the
palaeosol/Ossirarus bed (a lungfish body fossil) and the
laminated grey siltstone (eurypterid fossils; Smithson
et al. 2012).
Faunal list
A full list of vertebrate taxa represented within the TIM is
presented in Table 1. The following taxa and material have
been described elsewhere and will not be included here:
Aytonerepeton microps (Clack et al. 2016), Diploradus
austiumensis (Clack et al. 2016), Ballagadus rossi (Smithson
et al. 2015). The indeterminate tetrapod material is figured
in the supplement to Clack et al. (2016) and, based on
tooth morphology, probably represents at least two differ-
ent taxa but is not described here.
Class CHONDRICHTHYES Huxley, 1880
Family GYRACANTHIDAE sensu Warren et al., 2000
GYRACANTHIDAE indet
Material. Numerous fin spines, as well as UMZC 2017.2.584
and UMZC 2017.2.582, two scapulocoracoids (Fig. 4).
Diagnosis. Large, broad-based paired fin spines having a
distinct longitudinal curvature; fin spines inserted deep
into the body, their exserted portions with ornament
ridges oblique to the long axis of the spine. Fin spine
ridges bearing tubercular ornament. Large triangular
scapulocoracoid forms part of pectoral girdle.
Description. The spines thus far collected from the TIM have
the distinctive curvature of gyracanthid pectoral spines, as
opposed to the straightness of spines from other parts of the
body (Warren et al. 2000). Consistent with Warren et al.’s diag-
nosis (see above) at least 20 oblique ridges intersect the bound-
ary of the insertion area. Unlike Gyracanthides murrayi (Warren
et al. 2000), the insertion area is smooth to gently striated.
Tubercles on the oblique ridges are triangular with a median
ridge. Oblique ridges closest to the leading edge of spine inser-
tion have 2 tubercles each; moving towards the trailing edge, this
number increases to a maximum of approximately 13 before
decreasing to 6 or less. Tubercles of oblique ridges absent or
indistinct, perhaps as a result of wear and/or abrasion.
The scapulocoracoids are more complete than those of Gyra-
canthides murrayi figured by Warren et al. (2000), though they
are smaller in size. They have the same ridged bone texture and
TABLE 1 . Summary list of vertebrate taxa from the TIM at
Burnmouth.
Class ACANTHODII
Family GYRACANTHIDAE
Gyracanthidae indet.
Class CHONDRICHTHYES
Chondrichthyes indet.
Superorder HOLOCEPHALI
Order MENASPIFORMES
aff. Menaspiformes
Class OSTEICHTHYES
Subclass SARCOPTERYGII
Order RHIZODONTIDA
cf. Strepsodus sauroides
aff. Archichthys portlocki
Order DIPNOI
Dipnoi indet.
Uronemus splendens
Ctenodus roberti
Xylognathus macrustenus
Ballagadus rossi (Smithson et al. 2015)
Superclass TETRAPODA
Aytonerpeton microps (Otoo, Clack & Smithson in Clack et al.,
2016)
Diploradus austiumensis (Clack & Smithson in Clack et al.,
2016)
aff. Pederpes and Whatcheeria
Tetrapoda indet. (at least two taxa, Clack et al. 2016)
Class ACTINOPTERYGII Cope 1887
Actinopterygii indet.
Taxa with material that has been described elsewhere are listed
with the appropriate reference.
6 PALAEONTOLOGY
triangular shape, with the proximal portion showing a distinct
tapering.
Remarks. Gyracanth spines are common in Devonian–
Carboniferous non-marine settings (Turner et al. 2005;
Snyder 2011). Turner et al. (2005) referred a number of
Early Carboniferous records of Gyracanthus to Gyracan-
thides. However, both genera have been identified in
Tournaisian collections from Blue Beach (Mansky &
Lucas 2013). The two scapulocoracoids are identifiable as
gyracanth on the basis of the presence of ridges and striae
on both the internal and external surfaces (TRS pers.
obs.) as well as their resemblance to the scapulocoracoids
of Gyracanthides (Turner et al. 2005), though they are
not diagnostic to the generic level. The gyracanth material
is thus here only referred to Gyracanthidae indet.
Superorder HOLOCEPHALI Bonaparte, 1831
Order MENASPIFORMES? Obruchev, 1953 cf. Stahl 1999
MENASPIFORMES indet.
Figure 4A, B
Material. Two specimens, UMZC 2017.2.583 and UMZC
2017.2.526, each of one spine.
Diagnosis. Strongly asymmetric tuberculated dermal spine
dividing into two major prongs, each subtriangular; larger,
leading prong with prominent elliptic tubercles distributed
distally, long axes oriented towards the probable leading edge.
Description. The leading spine is slightly convex along the pre-
sumed leading edge. The trailing spine is straight and subconical.
The tuberculated surfaces are characteristic of menaspiform
mandibular spines, most clearly described and depicted by Pat-
terson (1965). The spines most closely resemble the mandibular
spines of Deltoptychius (Patterson 1965, fig. 28C). However, they
lack the spines on the distal tip. The broken area of UMZC
2017.2.583 is more completely preserved in UMZC 2017.2.526.
Remarks. Menaspiform holocephalans are a Permo-Carbo-
niferous group known from, among other places, the Visean
of Scotland and Illinois (Stahl 1999). The taxonomy of the
group is in need of revision. The specimens are not diagnos-
tic to a lower level, and lack associated toothplates to aid
identification. If they are correctly identified as menaspi-
form, they represent the earliest occurrence of the group.
Class OSTEICHTHYES Huxley, 1880
Subclass SARCOPTERYGII Romer, 1955
Order DIPNOI M€uller, 1845
cf. Uronemus splendens Traquair, 1873
Figure 5A
Material. UMZC 2017.2.588, a single isolated tooth plate.
Diagnosis. Tooth plate with linearly arranged conical
cusps, elongate ovoid base.
Description. UMZC 2017.2.588 is approximately 0.5 cm in length.
There are three conical cusps arranged linearly along one side of an
ovoid base.
Remarks. Specimen UMZC 2017.2.588 strongly resembles
the vomerine tooth plate of Uronemus splendens as described
and figured by Smith et al. (1987, fig. 20) in both size and
morphology, differing chiefly in having three cusps per ridge
instead of four. However, recent study of Tournaisian lung-
fish has found similar tooth plates in multiple taxa (TRS
unpub. data), and it is not clear whether the marginal tooth-
plates of Uronemus are unique or general.
A
E
C
D
F
B
F IG . 4 . Selected chondrichthyan bones. A, UMZC 2017.2.583,
menaspiform holocephalan mandibular spine. B, UMZC
2017.2.526, menaspiform holocephalan mandibular spine in
multiple views, with lighting changed to make morphology more
easily visible. C, UMZC 2017.2.481, fin spine showing insertion
area and tubercles on ridges. D, UMZC 2017.2.579, gyracanth
spine showing ridges. E, UMZC 2017.2.582, partial scapulocora-
coid. F, UMZC 2017.2.584, partial scapulocoracoid. All scale
bars represent 1 cm. Colour online.
OTOO ET AL . : SCOTTISH TOURNAIS IAN VERTEBRATE FAUNA 7
cf. Ctenodus roberti Smithson et al., 2015
Figure 5C
Material. A (partial?) pterygoid tooth plate only visible in CT
scan from UMZC 2015.46b.
Diagnosis. Oval tooth plate with six tooth ridges without
individual teeth.
Description. Oval-shaped tooth plate with six or seven slightly
diverging tooth ridges lacking teeth. The tooth plate is flat,
gently convex along the anterior edge and straight along the
medial side. It is incomplete medially and posteriorly. Maximum
length 4 mm; length to width ratio 3:1.
Remarks. This tooth plate resembles the holotype for
Ctenodus roberti (Smithson et al. 2015, figs 3D, 4H). It is
approximately seven times smaller than the C. roberti
holotype. It is possible that it is incomplete laterally, but
even allowing for this, it is much smaller than the
C. roberti holotype.
cf. Ballagadus caustrimi Smithson et al., 2015
Figures 5E–F, 6
Material. An incomplete skeleton represented by disarticulated
cranial dermal bones, articulated ribs and fin ray supports
together with two (partial?) pterygoid tooth plates only visible in
CT scan (Fig. 5E, F) from 2015.46b, and two sets of cranial der-
mal bones (Fig. 6A, B).
Diagnosis. Toothplate with four tooth ridges. More com-
plete specimen (Fig. 5F) shows two teeth on the pterygoid
ridge and four or five on the other ridges. Ridge angle
approximately 100–120°.
Description. Both tooth plates are incomplete and appear to be
lacking at least one tooth ridge. The largest specimen is c. 5 mm
long, the other is 3 mm long. As preserved, the length to width
ratio is c. 2.5:1. The largest specimen has four intact tooth ridges
with the remains of a fifth. The smaller specimen has four par-
tial tooth ridges. The tooth ridge angle on the largest specimen
is c. 60° and c. 90° on the smaller specimen.
The skeleton (Fig. 6C–H) also appears to belong to
B. caustrimi. The overall body length of the animal represented
is approximately 8–9 cm, much smaller than Ctenodus spp. Fin
supports are present dorsally and ventrally. Unlike Xylognathus
macrustenus, the dorsal and anal fins do not seem to be separate.
The head plates resemble those of a lungfish recovered from the
surface of the palaeosol below the Ossirarus bed (Fig. 6A, B).
While not much morphology is visible, the tail fin appears to be
continuous dorsally and ventrally. The headplates are thick and
subcircular, with very fine small tubercles.
Remarks. The tooth plates in the CT scan are similar to
those of Ballagadus caustrimi (which is in turn highly
A
B
C E
F H
D G I
F IG . 5 . Lungfish toothplates with reconstructions. A, UMZC 2017.2.588, vomerine toothplate resembling that of Uronemus splendens.
B, reconstruction of Uronemus dorsal dentition modified from Smith et al. (1987). C, CT scan of toothplate assigned to Ctenodus
roberti. D, reconstruction of C. roberti dorsal dentition from Smithson et al. (2015). E–F, CT scans of toothplates assigned to Balla-
gadus caustrimi. G, reconstruction of B. caustrimi dorsal dentiton from Smithson et al. (2015). H, CT scan of partial toothplate
assigned to Xylognathus macrustenus in multiple views. I, reconstruction of X. macrustenus dorsal and ventral dentition. CT scans are
from UMZC 2015.46b. Scale bars represent: 1 cm (A, D, G, I); 0.8 cm (B); 0.5 cm (C, E, F, H).
8 PALAEONTOLOGY
similar to B. rossi), particularly if they are assumed to be
damaged. These tooth plates are half the size of the
B. caustrimi tooth plate figured by Smithson et al. (2015),
but are similar in size to those present on the referred
specimen UMZC 2014.1.6a collected by Stan Wood
(Smithson et al. 2015, p. 43). The skeleton (Fig. 6C–H)
represents an animal with an overall length of approxi-
mately 8–9 cm, one of the smallest lungfish from the Bal-
lagan Formation, and is probably similar in size to
Coccovedus celatus (Smithson et al. 2015). Dorsoventral
continuity of the tail fin has been considered characteris-
tic of post-Devonian lungfish in contrast to Devonian
forms, but has recently been recognized in Late Devonian
lungfish (JAC pers. obs.).
cf. Xylognathus macrustenus Smithson et al., 2015
Figure 5H
Material. The posterior portion of a pterygoid toothplate only
visible in CT scan from UMZC 2015.46b.
Diagnosis. Narrow, flattened toothplate with two promi-
nent teeth and (possibly) two more smaller teeth.
Description. This toothplate is clearly incomplete and corre-
sponds to the posterior portion of the Xylognathus tooth
plate. It is flat and slightly curved along the long axis at an
approximately 90° angle. Apart from damage/wear to the
specimen, the surface appears to be smooth and lacking indi-
vidual denticles.
Remarks. While the anterior portion of the toothplate is
missing, the remaining posterior portion is a strong
match for Xylognathus, particularly in preserving the dis-
tinctive two rows of teeth. It is also of comparable size to
the pterygoid toothplate for Xylognathus as reconstructed
by Smithson et al. (2015).
Order RHIZODONTIDA Andrews & Westoll, 1970
cf. Strepsodus sauroides Binney, 1841 sensu Jeffery 2006
Figure 7
Material. Incomplete and fragmentary skull bones, scales, a ser-
ies of articulated vertebrae, numerous partial and complete clei-
thra and clavicles.
Diagnosis. Cleithrum with anastomosing ridged ornament.
Clavicle with tuberculate ornament and rounded anterior
tip. Simple, cylindrical vertebrae. Subcircular scales with
ridged exterior surface and central boss in internal view.
Description. Cleithra range from almost complete specimens to
fragments. When preserved on the cleithra, the dorsal laminae
all have a slight ridge running down the external ascending blade
with a slight prominence at the top (Z. Johanson pers. comm.
November 2017) This differentiates the cleithrum of Strepsodus
from the cleithrum of Screbinodus (Andrews 1985).
The vertebrae are articulated and exposed in probable ventral
or ventrolateral view. The vertebrae (Fig. 7A) are smooth, mas-
sive, and broad-waisted. They are extremely similar to the Strep-
sodus vertebrae figured by Andrews & Westoll (1970, pl. 13a).
This morphology contrasts with the more pleisiomorphic rha-
chitimous vertebrae of more basal rhizodonts such as Barameda
(Garvey et al. 2005), and they are much more robust than those
of Hongyu (Zhu et al. 2017).
Remarks. While rhizodont cleithra are often preserved due
to their robustness, even in juveniles (Andrews & Westoll
1970; Andrews 1985; Davis et al. 2001), they are highly
variable within species due to age and individual variation.
The dermal bone fragments are united in having either a
tuberculate or ridged ornament. The quality of the preser-
vation of the ornament varies but the ornamentation pat-
terns are consistent. This suggests that the varied material
can be assigned to Strepsodus despite its being isolated.
A
B
C E
F H
G
D
F IG . 6 . Fossils attributed to Ballagadus caustrimi. A–B, uncatalogued skull bones from the Ossirarus bed. C–H, body fossils from the
Aytonerpeton bed arranged anterior–posterior from C/D to G/H; C, E, G, UMZC 2015.46a, b, e; D, F, H: UMZC 2015.46d, c, e. All
scale bars represent 1 cm. Colour online.
OTOO ET AL . : SCOTTISH TOURNAIS IAN VERTEBRATE FAUNA 9
aff. Archichthys portlocki sensu Jeffery, 2006
Figure 8
Possible synonyms. ‘cf. Archichthys portlocki’, GLAHM 152115,
GLAHM 152121, GLAHM 152252 (Carpenter et al. 2014);
‘Archichthys portlocki’ YPM VPPU 019334, NSM008GF040.063
(Carpenter et al. 2015); ‘Archichthys portlocki’ NBMG 15799,
15818, 19972 (
O Gog
ain et al. 2016).
Material. UMZC 2017.2.465 and UMZC 2017.2.458 from Burn-
mouth, UMZC 2017.2.551 and UMZC 2017.12.2 from Coldstream.
Diagnosis. Recurved, robust teeth with short, anastomosing
striae. Striae form a ‘collar’ around the circumference of the
tooth and are absent from the tip. Twelve basal plications.
Description. The teeth include both insolated singletons, teeth
attached to jaw fragments, and a possible vomer, UMZC
A
B
C
D E
F
G
H
I
J
K L M
N
O
F IG . 7 . Various rhizodont bones assigned to Strepsodus. A, UMZC 2017.2.578, vertebrae in articulation. B, UMZC 2017.2.520, scales.
C, UMZC 2017.2.447, opercular or subopercular in internal and external views. D–H, cleithra showing growth series: D, UMZC
2017.2.537; E, UMZC 2017.2.541; F, UMZC 2017.2.571; G, UMZC 2017.2.539; H, UMZC 2017.2.515a. I, UMZC 2017.2.672, smallest
cleithrum in internal view. J, UMZC 2017.2.534, partial left clavicle showing dermal ornament. K, UMZC 2017.2.535 partial right clav-
icle. L, UMZC 2017.2.531, partial left clavicle. M, UMZC 2017.2.532, partial left clavicle. N, UMZC 2017.2.538, partial humeral head.
O, UMZC 2017.2.538, radius. All scale bars represent 1 cm. Colour online.
10 PALAEONTOLOGY
2017.2.458. UMZC 2017.2.458 is heavily damaged, but the bone
is approximately teardrop-shaped in occlusal view. A wall of
bone brackets approximately half the circumference of the tooth
and extends straight posteriorly.
The teeth are circular to oval in cross-section. Where preserved,
the bases appear to have 12 plications. The teeth vary in size, sug-
gesting that the striation pattern is present on teeth across the jaw.
None of the teeth preserve the sigmoid tip characteristic of Strep-
sodus dentary fangs. Apart from the striation pattern they are
otherwise like the teeth of Archichthys, robust as opposed to the
slender teeth of Letognathus which share a similar striation pattern
(Brazeau 2005). The presence of striae distinguishes them from
the smooth teeth of Rhizodus and Screbinodus (Andrews 1985).
The striation pattern differs from that of Strepsodus, which is
composed of larger parallel striae (Jeffery 2006).
Remarks. These teeth are difficult to distinguish from
those of Archichthys given the similarity in striation pat-
tern, and teeth from the Ballagan on the Isle of Bute
have been assigned to Archichthys previously (Carpenter
et al. 2014). The situation is not helped by the current
limits of reliably-assigned Archichthys material (Jeffery
2006). However, the presence of these teeth in the TIM,
elsewhere at Burnmouth, and at Coldstream, another
Ballagan locality (see Smithson et al. 2012 for more
A B
C D
E F
G H
F IG . 8 . Rhizodont teeth showing
unusual striation pattern. A–B,
UMZC 2017.2.465, vomer with
tooth in: A, medial; B, occlusal
view. C, UMZC 2017.2.465,
enlarged view of tooth showing stri-
ation pattern. D, UMZC 2017.2.458,
teeth in ?medial view showing stria-
tion pattern. E–F, UMZC
2017.2.551, tooth from Bed 1 at
Burnmouth, 383 m in the section
(approximately 45 m above the
TIM). G–H, UMZC 2017.12.2,
tooth from the Coldstream locality
showing striation pattern. Scale bars
represent: 1 cm (A, B, E–H); 0.5 cm
(C, D). Colour online.
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 11
locality information) suggests that genuine variation is
being sampled. Given the confounding effects of tooth
and scale taxonomy on our understanding of rhizodonts
(Andrews 1985; Jeffery 2006) and the state of ongoing
work, we are hesitant to erect a new taxon at this time.
Superclass TETRAPODA Goodrich, 1930
aff. Pederpes Clack, 2002 and Whatcheeria Lombard & Bolt,
1995
Material. UMZC 2016.8, two incomplete possible frontal and pre-
frontal bones, possibly with partial nasal (Fig. 9A, B; Clack et al.
2016, fig. 6F, G), UMZC 2017.2.569, a cleithrum (Fig. 9C), UMZC
2016.9, partial maxilla with teeth (Fig. 9D), UMZC 2017.2.611, a
radius (Fig. 9E), digit bones (e.g. UMZC 2017.2.577, Fig. 9F), and
UMZC 2017.3.576, an intercentrum (Fig. 9G).
Diagnosis. Ornament on skull roof bones subcircular at
the centre of the bone and more ovoid toward the
margin. Teeth anteroposteriorly compressed in cross-sec-
tion. Maxilla and cleithrum with fine ornament texture.
Description. The ornament of the frontals contrasts with that of
Pederpes, which has a pattern of pits with ridges and grooves;
ornament in Whatcheeria is limited to very light pitting. The
proportions of the bones suggest suggest that they are more
similar to the relatively short and narrow frontals of Whatcheeria
and Pederpes than the longer frontals of Greererpeton. The shape
of the right frontal implies a broad, triangular prefrontal as in
Whatcheeria.
The stem of the cleithrum is narrow and straight, more simi-
lar to that of Whatcheeria than Pederpes. However, the dorsal
expansion, though incomplete, does not seem to have the char-
acteristic notch of Whatcheeria. Among the jaw material
(Fig. 9D), there is both a ‘large’ size fraction (approximately
9 cm) and a ‘small’ size fraction (approximately 1 cm). How-
ever, all of these preserve teeth with the same anteroposteriorly
compressed cross-section. The toe bones are longer than broad,
are clearly waisted, asymmetrical, and strongly concave on the
flexor surface. In this they resemble the proximal foot bones of
A B
C
D
E F G
F IG . 9 . Selection of TIM ‘whatch-
eeriid’ material. A–B, UMZC
2016.8, paired frontals; B, CT scan;
the lower frontal is exposed in the
specimen. C, UMZC2017.2.569, clei-
thrum. D, UMZC 2016.9, left max-
illa in multiple views. E, UMZC
2017.2.611, radius in external and
internal view. F, UMZC 2017.2.577,
digit in dorsal and ventral view. G,
UMZC 2017.3.576, intercentrum in
external (left) and internal (right)
views. All scale bars represent 1 cm.
Colour online.
12 PALAEONTOLOGY
Pederpes but contrast with those of Whatcheeria, which are much
flatter and broader than long (BKAO pers. obs.)
Remarks. The skull bones are most like those of Pederpes
and Whatcheeria. However, confirmation must await more
complete specimens. The other specimens are not associ-
ated with the skull bones, but resemble Whatcheeria/Peder-
pes in some respects, contrast with the colosteid-like
morphology of Aytonerpeton and are too large to be
assigned to Diploradus. The jaw material is particularly
interesting; the distinctive tooth morphology seems to be
unique and allows for the unification of specimens of mul-
tiple sizes. UMZC 2014.14, a maxilla collected from Heads
of Ayr by JAC in 2014 (see Clack et al. 2016, suppl. data),
appears to have a similar tooth morphology. Though there
is not sufficient material for a formal diagnosis, we suspect
this represents a new taxon.
cf. Aytonerepeton microps Otoo, Clack & Smithson
in Clack et al., 2016
Figure 10
Material. UMZC 2016.7, a partial skull table, and UMZC
2016.6b, a parasphenoid.
Diagnosis. Tetrapod skull table with colosteid-type dermal
ornament, curved posterior orbital margin, and circular
parietal opening without thickened margin. Parapshenoid
with short dorsum sellae and extensively denticulated
posterior plate.
Description. The skull table is exposed in internal view
(Fig. 10A). The pattern of dermal ornament is extremely similar
to that of Aytonerpeton, if not identical. Exposures of the lateral
line are visible on the postfrontals and postorbital. The pattern
of lateral line exposure is nearly identical to that of Greererpeton
in the same region (Smithson 1982). The parietal opening is rel-
atively much larger.
A lower-resolution image of the parapshenoid was included
in the supplement to Clack et al. (2016). In Figure 10D–H the
sculpturing on the ventral surface of the cultriform process and
denticulation on the posterior plate are more clearly visible.
Clack et al. (2016) pointed out the short dorsum sellae, compar-
ing it to later temnospondyls, as well as noting the unique extent
of posterior plate denticulation. The morphology of the paras-
phenoid contrasts strongly with that of Greererpeton, having a
broader posterior plate and a relatively shorter, broader cultri-
form process. This is suggestive of a broader, less elongate skull.
Remarks. The size of both the parasphenoid and skull
table are consistent with them belonging to Aytonerpeton.
The proportions of the parasphenoid are consistent with
the skull proportions of Aytonerpeton, which has a much
shorter skull than Greererpeton. The colosteid-like lateral
line exposure on the skull roof and the great similarity in
dermal ornament to Aytonerpeton suggest that it belongs
to that taxon. However, definitive assignment must await
the discovery of more complete Aytonerpeton specimens
against which these can be compared.
Class ACTINOPTERYGII Cope, 1887
ACTINOPTERYGII indet.
Figure 11
Material. Isolated scales (e.g. UMZC 2017.2.719 and UMZC
2017.2.718, Fig. 11B, C), rarer squamation (Fig. 11A), UMZC
2017.2.717, an isolated dermal bone (Fig. 11D), and UMZC
2017.2.668, a partial skull roof (Fig. 11E).
Diagnosis. Ornament-covered scales with either diamond
shape or elongate trapezoidal shape. Diamond-shaped
A B
D
G
H
E F
C
F IG . 10 . Tetrapod material cf.
Aytonerpeton. A, UMZC 2016.7,
skull table exposed in interior view
with mould of dermal ornament. B–
C, CT scan of the same specimen
in: B, external; C, internal view. D–
F, UMZC 2016.6b, parasphenoid in:
D, ventral; E, dorsal; F, right lateral;
G, posterior; H, antero-dorsal view.
Abbreviations: BPP, basipterygoid
process; CF, cultriform process; DS,
dorsum sellae; FR, frontal; LL, lat-
eral line; PAR, parietal; PF, pineal
foramen; PFR, postfrontal; PO, pos-
torbital. All scale bars represent
1 cm.
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 13
scales have anterodorsal process and dorsal peg. Dermal
bones ornamented with either smooth elongate tubercles
or ridges.
Description. Two different actinopterygian scale morphologies
are present: smaller, more equidimensional scales that occur as
hash (Fig. 11A) and larger, dorsoventrally elongate scales that
are found in isolation (Fig. 11B, C). The former are shiny,
whereas specimens of the latter exhibit variable amounts of lus-
tre. The morphology of the smaller scales is consistent with their
being from the caudal lobe of the tail; the larger scales probably
come from the flank.
UMZC 2017.2.717 appears to come from the roof of the skull.
It is possible that instead of being a single bone it is a set of paired
bones. UMZC 2017.2.668 is a partial skull roof, encompassing
parts of the frontals and parietals. The ridged ornament pattern is
common to many early actinopterygian genera (Daeschler 2000;
Friedman & Blom 2006; Mickle 2011, 2017; Sallan & Coates 2013).
The orbital margin is long. The frontals are more than twice as
long as the parietals and incomplete anteriorly. The posterior mar-
gin of the parietals is indented at the midline. The growth centre
of the right frontal is visible, marked by the central whorl of orna-
ment. The pits of the surpraorbital canal are also discernable,
crossing over the centre of the right frontal and curving laterally
near the parietal. The right parietal shows the three pit lines char-
acteristic of actinopterygians.
Remarks. Though there are actinopterygian fossils present
in numerous samples from the TIM, in absolute terms
the amount of material is small and mostly consists of
scales. The proportions of the frontals and parietals com-
pares favourably with that of Limnomis (Daeschler 2000)
and Cuneognathus (Friedman & Blom 2006) from the
Famennian, both of which are small-bodied. However,
they contrast with Avonichthys from the Tournaisian
(Wilson et al. 2018). Interestingly, the elongation of the
frontals relative to the parietals has been considered a
derived character. None of the taxa appear to have an
indented posterior parietal margin, but such an indent
appears in Rhabdolepis macropterus from the Permian
(Schindler 2018).
The phylogenetic analysis of Friedman & Blom (2006)
recovered Limnomis and Cuneognathus as the sister taxa
to Kentuckia from the Visean. While there is not enough
material for a phylogenetic analysis or taxonomic
assignment, the morphology of UMZC 2017.2.668 sug-
gests that it may be part of this Devonian–Carboniferous
group.
RESULTS
Sedimentology results
The fossil-rich interval represents a change in sedimentary
environment from permanently wet and marshy
conditions to seasonally wet conditions (Clack et al.
2016). The 250 cm thick section that contains the TIM
illustrates this transition in detail (Fig. 2). The lower half
of the section (up to 1.4 m height) includes a dolostone
bed at the base, which contains ostracods and fish debris
A
B
D
E
C
F
F IG . 11 . Overview of actinopterygian material. A, scale hash
from 2015.46. B, UMZC 2017.2.719, isolated scale. C, UMZC
2017.2.718, isolated scale. D, UMZC 2017.2.717, dermal bone(s).
E–F, UMZC 2017.2.668, partial skull roof, anterior is at the top
of the image; F, interpretive drawing at same scale. Abbrevia-
tions: FR, frontal; PAR, parietal; PPL, parietal pit lines; SOC,
supraorbital canal. All scale bars represent 1 cm.
14 PALAEONTOLOGY
and has a brecciated top. This is overlain by a sequence
of two 40–50 cm-thick gleyed inceptisols (cf. Kearsey
et al. 2016), interbedded with mottled siltstones and
sandy siltstones. Desiccation cracks occur in three hori-
zons and are infilled with sandy siltstone. Dolostone nod-
ules are associated with the lower gleyed inceptisol but
are localized, and only present on the foreshore. The
upper half of the section contains a complex sequence of
fossil-rich sandy siltstones (Fig. 2, Detailed Log). Overly-
ing this is a sequence of interbedded laminated grey silt-
stones and red siltstones (inceptisols), which have
numerous desiccation cracks. At the top of the section a
vertisol red siltstone bed contains green drab root haloes.
For full description of palaeosol facies, see Kearsey et al.
(2016).
The detailed log illustrates the complexity of the fossil-
rich interval (Fig. 2). At the base is a thin gleyed Inceptisol,
the top of which is brecciated and infilled by the overlying
sandy siltstone. In thin section this bed is light grey, mot-
tled, with fish scales, plant and ostracod fragments at ran-
dom orientations within a coarse siltstone matrix (Fig. 3,
thin section 1). The top of the gleyed inceptisol has an
irregular surface, attributed to erosion by the overlying
sandy siltstone bed (Fig. 3A). This sandy siltstone bed is
laterally variable in thickness and in the metre-square sec-
tion it has desiccation cracks in the centre and at the top
(Fig. 2) indicating that it is a composite of two event beds
(Fig. 12). This is overlain by a thin laminated grey siltstone
bed which is localized to the foreshore (not present in the
cliff exposure). Above this is the first tetrapod-bearing bed,
containing Ossirarus, an organic-rich, structureless, black
sandy siltstone (Fig. 3A, B). Overlying this dark sandy silt-
stone bed are two very fine sandstone beds, with asymmet-
ric ripple lamination, that fine upwards into siltstone.
Their thickness on the foreshore is 2–4 cm, with thinner
beds observed in the cliff section (Figs 2, 3).
The second tetrapod-bearing bed, with Aytonerpeton, is
a 9 cm, structureless, dark grey sandy siltstone. In thin-
section this bed is characterized by a fine-grained siltstone
matrix with sub-millimetre sized clasts of siltstone, sand-
stone and bioclasts (Fig. 3, thin section 2), while in the
metre-square section, larger light green siltstone clasts up
to 5 mm in size are present, which are of a similar lithol-
ogy to the underlying gleyed inceptisol. Plant material is
abundant and plant fossils are sometimes flow-aligned to
produce a wavy fabric. Overlying this bed is a sequence
of laminated grey siltstone, with millimetre-thick sand-
stone lenses. Within this bed is a thin sandy siltstone
inter-bed that infills desiccation cracks (Fig. 3, thin sec-
tion 3). Above the laminated bed is another sandy silt-
stone, containing a green siltstone lens, which is the last
sandy siltstone in the sequence. At the top of the detailed
log sequence are further laminated grey siltstones, with
sparse desiccation cracks.
Microfossil results
The purpose of this microfossil study is to characterize
the microfossil assemblages in terms of palaeoenivron-
ments, not to describe the taxonomy of fossil specimens.
Each sample has a unique microfossil assemblage
(Fig. 13). Microfossils are generally well preserved, with
minimal wear, abrasion, or cracks observed.
Sample 1: palaeosol. The assemblage is dominated by
ostracods, with a minor component of actinopterygian
scales, one actinopterygian tooth, one rhizodont scale and
plant fragments (Fig. 13). The majority of ostracods pre-
sent are poorly preserved; the following were identified to
genus level: Beyrichiopsis, Cavellina, Glyptolichvinella,
Paraparchites, Shemonaella, Silenites, Sulcella (Fig. 14A–
D). This assemblage is typical of the fine-grained clastic
lithologies of the Ballagan Formation (Williams et al.
2005). Of these, Cavellina, Shemonaella and Glyp-
tolichvinella are most numerous within the sample (Otoo
et al. 2018, micropalaeontology data). The 1 mm and
425 lm fractions have a ratio 1:3 carapaces:single valves,
while the 250 and 125 lm fractions contain mostly bro-
ken single valves, which is probably an artefact resulting
from breakage during sieving. Ostracod juveniles with the
full instar size range are present and there is no apparent
size sorting of the assemblage. The actinopterygian tooth
(Fig. 14E) lacks the apical cap but preserves the character-
istic cross-hatched surface texture (Carpenter et al. 2011).
Sample 2: sandy siltstone. This sample has the highest
number of fossil specimens, at 98.7 fossils/g, which is
twice as many as sample 1 and five times more than sam-
ple 3 (Otoo et al. 2018, micropalaeontology data). The
assemblage is dominated by plant material (fibrous frag-
ments, probably from plant stems) and rhizodont scale
F IG . 12 . CT scan of UMZC 2017.2.483 before preparation,
showing the internal stratigraphy of the fossil-rich layer captured
by the TIM. This specimen does not come from within the TIM
itself but was laterally adjacent to it. Note the two event beds
marked by the fossil concentrations at the top and bottom of
the specimen. Scale bar represents 1 cm.
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 15
and bone fragments (Fig. 13). Rhizodonts are also domi-
nant in the underlying Ossirarus bed that was sieved and
picked for microfossils as a pilot study, but not quantita-
tively picked (Fig. 14F–H). The exterior surface of the
scales has a fibrous structure, and shiny, silver colour.
When broken, the interior layers have a range of struc-
tural elements characteristic of rhizodonts (Andrews
1985) including sheets of either tubercules and pits or
grooves and ridges that interlock together. These struc-
tures were identified by the examination of broken rhi-
zodont scale macrofossils from the TIM interval. Also
present are indeterminate megaspores (with a smooth
external surface, no visible trilete marks; Fig. 14I),
actinopterygian scales and teeth. Actinopterygian scales
have a rhombic shape with a smooth interior surface with
keel, and sculpted exterior surface with transverse ridges
or grooves (Fig. 14J–K). Small rows of curved unorna-
mented actinopterygian teeth, probably pharyngeal in ori-
gin, occur solely within the 125 lm fraction (Fig. 14M–
N). Indeterminate brown or black cuticle occurs within
all size fractions, and in sample 3. One fragment of semi-
lunate shaped eurypterid scale occurs in the underlying
Ossirarus sandy siltstone bed (Fig. 14L). Dipnoan and tet-
rapod microfossils have not been recorded from this bed,
because of the difficulties of scale and bone fragment
identification and their relative rarity compared to the
other vertebrates. The amount of unidentified vertebrate
bone and scale material varies per sample (sample 1:
0.5%; sample 2: 3.4%; sample 3: 15.2%; Otoo et al. 2018,
micropalaeontology data).
Sample 3: laminated grey siltstone. The sample has a lower
number of specimens in each size fraction compared to
the other two samples. Plant fragments, Spirorbis and
actinopterygian bone and scale fragments dominate the
assemblage (Fig. 13). Spirorbis specimens are fragmented
and pyritized (Fig. 14O). Ostracod fragments, indetermi-
nate cuticle and one rhizodont scale fragment are also
present. The125 lm fraction contains a higher number of
actinopterygian fragments than the other size fractions,
consisting of small scale and bone debris.
Faunal similarity analyses
In all analyses, Devonian and Carboniferous localities plot
on opposite sides of the origin along the x-axis (Figs 15–
18). The convex hulls for each stage overlap within their
F IG . 13 . Microfossil assemblages. Percentage counts of total assemblage microfossil counts for three samples. A, sample 1 (palaeosol,
n = 777 specimens). B, sample 2 (sandy siltstone, n = 1470). C, sample 3 (laminated grey siltstone, n = 262). The full data table of
counts for all size fractions and microfossils per gramme is presented in Otoo et al. (2018). Abbreviations: actin., actinopterygian;
indet., indeterminate; rhizo., rhizodont. Colour online.
F IG . 14 . Selected microfossil specimens. A, Glyptolichvinella, juvenile, left valve, partially broken, lateral view, microfossil sample 1.
B, Shemonaella, juvenile, left valve, lateral view, microfossil sample 1. C, Beyrichiopsis, adult, left valve, lateral view, broken specimen
with a single costa, microfossil sample 1. D, Cavellina, adult, carapace, right lateral view, microfossil sample 1. E, actinopterygian
tooth, broken cap, lateral view, microfossil sample 1. F, rhizodont dermal bone, view of the exterior surface with pustular ornamenta-
tion, from the Ossirarus sandy siltstone bed. G–H, rhizodont scales, with two different internal structures, Ossirarus bed. I, megaspore,
indeterminate, with smooth external surface, broken specimen, microfossil sample 2. J–K, actinopterygian scale fragments, microfossil
sample 2: J, interior; K, exterior surfaces. L, single scale, broken, from eurypterid cuticle, Ossirarus bed. M–N, pharangeal actinoptery-
gian teeth, lateral view, microfossil sample 2. O, pyritized Spirorbis tube fragment, microfossil sample 3. Scale bars represent: 100 lm
(A–E, J, M, N); 500 lm (F, G); 250 lm (H, I, K, L, O).
16 PALAEONTOLOGY
respective period, but there is no Devonian/Carboniferous
overlap. Attempted analyses using environmental sub-
categories proved unsuitable within the constraints of the
methods used here and are not included.
Correspondence analysis. When the total dataset is anal-
ysed using correspondence analysis (CA), marine sites
generally plot below 0 on the y-axis and non-marine
(= marginal + continental) sites plot above 0 (Fig. 15).
A B C
D E F
G H I
J K L
M N
O
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 17
F IG . 15 . Correspondence analysis results, full dataset. A, raw diversity. B, relative diversity.
18 PALAEONTOLOGY
Thus four broad time-setting associations emerge when
the entire raw diversity dataset (Fig. 15A) is analysed:
1. Devonian marine: Onychodontida, Ischnacanthida,
Arthrodira, Ptyctodontida, other placoderms.
2. Devonian non-marine: Phyllolepida, Dipnoi, Acan-
thodida, Climatiida, Porolepiformes, Osteolepididae,
Antiarcha, Tristichopteridae.
3. Carboniferous marine: Elasmobranchii, Actinistia,
Symmoriiformes, Holocephali, Actinopterygii.
4. Carboniferous non-marine: Tetrapoda, Rhizodontida,
Megalichthyidae, Gyracanthida.
Analysis of the entire relative diversity dataset returns
the same broad associations, except acanthodians move to
the Carboniferous non-marine association (Fig. 15B). In
both the raw and relative diversity analyses Burnmouth-
TIM emerges closest to Mill Hole (Fig. 15).
When only the non-marine sites are analysed, marginal
sites do not plot separately from continental sites in any
recognizable pattern, though the relative Devonian/Car-
boniferous positions are maintained (Fig. 16). The Give-
tian convex hull overlaps less with the Frasnian and
Famennian hulls, and the Serpukhovian hull no longer
overlaps with the Tournaisian and Visean hulls. Burn-
mouth-TIM plots roughly equidistant from Mill Hole,
Gilmerton, and Niddrie. When raw diversity (Fig. 16A) is
analysed the following associations are recovered:
• Devonian: Climatiida, Onychodontida, Acanthodida,
Ptyctodontida, Ischnacanthida, Osteolepididae,
Arthrodira, Phyllolepida, Actinistia, other placoderms.
• Devonian: Dipnoi, Antaircha, Porolepiformes, Tristi-
chopteridae, Phyllolepida.
• Carboniferous: Actinopterygii, Megalichthyidae, Sym-
moriiformes, Elasmobranchi.
• Carboniferous: Tetrapoda, Rhizodontida, Gyracan-
thida, Holocephali.
When relative diversity is analysed (Fig. 16B), actinis-
tians join the actinopterygian-megalichthyid-elasmo-
branch-symmoriiform association, and phyllolepids join
the other Devonian association.
Non-parametric multidimensional scaling. As with the
correspondence analysis results, in the NMDS results
Devonian and Carboniferous sites are separated along the
x-axis (co-ordinate 2) and marine and non-marine sites
are separate along the y-axis (co-ordinate 1; Fig. 17). The
relative positions of the individual sites are similar to
those in the correspondence analysis (CA) results. In
analyses of both the total raw diversity dataset (Fig. 17A)
and the total relative diversity dataset (Fig. 17B), Burn-
mouth-TIM emerges closest to Mill Hole and nearby
Gilmerton, Niddrie and Dora. When only non-marine
sites are analysed (Fig. 18), as with the CA results the
overlap between the Givetian and Serpukhovian hulls and
those of the other Devonian and Carboniferous stages,
respectively, decreases, more so for raw (Fig. 18A) than
relative diversity (Fig. 18B). Burnmouth-TIM maintains
its relative position.
DISCUSSION
Sedimentology interpretation
The depositional environments represented in the
250 cm-thick section (Fig. 2) are diverse. The basal dolo-
stone represents deposition in a saline–alkaline lake, with
a marine influx onto the floodplain attributed to storm
activity (Bennett et al. 2017). The mottled grey siltstones
and green palaeosols represent deposition within a flood-
plain lake, then the growth of vegetation. Although peri-
ods of desiccation occurred in the lower part of the
section, in general the soils were waterlogged and the
environment was probably a saline (brackish) marsh
(Kearsey et al. 2016). Sandy siltstones were deposited as
cohesive debris flows in flooding events after periods of
desiccation (Bennett et al. 2016). In the 40 cm-thick fos-
sil-rich interval numerous flooding events deposited a
sequence of six sandy siltstone beds, some of which over-
lie desiccation cracks. Lateral variability in the thickness
and internal structure of sandy siltstones and very fine
sandstones between the cliff and foreshore exposures
highlight the localized origin of these deposits.
A modern analogue for the dry/wet alternations seen in
the palaeosol/sandy siltstone association are mud aggre-
gates in dryland river floodplains (Rust & Nanson 1989;
Wakelin-King & Webb 2007a, b). However, the climate of
the Ballagan Formation is interpreted as tropical, with
seasonal monsoonal rainfall (Falcon-Lang 1999; Kearsey
et al. 2016). Sandy siltstone deposits have not been
reported from other sites in the geological record, and
have probably been reported as massive siltstone beds,
due to the small size of their clasts. However, a similar
facies occurs in the Early Cretaceous Wessex Formation,
Isle of Wight. Here plant debris beds contain a similar
fauna and are also interpreted to have formed as debris
flow deposits during flooding events in a tropical climate
(Sweetman & Insole 2010). These plant debris beds infill
local depressions on the floodplain and also contain sedi-
ment clasts and fossils within a siltstone matrix. They dif-
fer from sandy siltstones in having larger-sized clasts and
fossils (including dinosaur bones) but are otherwise inter-
preted to have formed by a similar mechanism. Overbank
deposits preserve tetrapod fossils at the Famennian site of
Red Hill, Pennsylvania, but further study is needed to
determine whether the standing water taphofacies
described as ‘green-grey siltstones with abundant plant
material and an occasional occurrence of arthropod and
vertebrate remains’ (Cressler et al. 2010, p. 117) are
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 19
F IG . 16 . Correspondence analysis results, non-marine sites only. A, raw diversity. B, relative diversity.
20 PALAEONTOLOGY
F IG . 17 . Non-parametric multidimensional scaling results, full dataset. A, raw diversity. B, relative diversity.
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 21
F IG . 18 . Non-parametric multidimensional scaling results, non-marine sites only. A, raw diversity. B, relative diversity.
22 PALAEONTOLOGY
analogous to sandy siltstones. This emphasizes the ecolog-
ical and preservational importance of these environments
in the Devonian–Carboniferous.
Between flood episodes, laminated grey siltstones were
deposited from suspension within shallow floodplain
lakes. After the last sandy siltstone bed, lacustrine condi-
tions were re-established with clastic input of siltstones
and thin sand beds, perhaps derived from small sheet-
floods into the lake. Inceptisols and large desiccation
cracks formed by sub-aerial exposure of the lake and
scrubby vegetation growth on the floodplain. Finally, the
vertisol represents the formation of a more established
soil, due either to the growth of vegetation under rela-
tively dry, long-lived conditions or to a drop in the local
water table/infilling of the water body by sediment. Roots
recorded from vertisols in the Ballagan Formation can be
up to 1 m in depth and are interpreted as having been
formed by isolated stands of lycopsid trees (Kearsey et al.
2016).
Micropalaeontology interpretation
The variation within the microfossil assemblages illus-
trates the different palaeoenvironmental and taphonomic
histories of each of the beds. Taking into account the
breakage of some ostracod specimens during pedogenesis,
the ostracod assemblage within the palaeosol is indicative
of an autochthonous deposit due to the presence of juve-
niles, adults and carapaces (Boomer et al. 2003). The
ostracods represent one of the oldest brackish-water
floodplain assemblages of this group (Williams et al.
2005, 2006), although solely freshwater genera such as
Carbonita that occur in the Visean (Bennett et al. 2012)
are absent. A brackish salinity for this bed is consistent
with the formation of the gleyed inceptisol under water-
logged brackish conditions (Kearsey et al. 2016). The
habitat of the ostracods may have been a saline marsh or
pool on the floodplain.
The dominance of rhizodont microfossils within the
Aytonerpeton bed is unusual for Ballagan Formation sandy
siltstone beds, in which actinopterygian (macro)fossils are
more common than rhizodonts (Bennett et al. 2016).
This is the most rhizodont-rich bed observed within the
Burnmouth succession to date. The evidence of clasts and
flow-aligned plant debris within the bed indicates the
transport of all fossil material, although the articulated
nature of some specimens (e.g. the Aytonerpeton holotype,
rhizodont vertebral series, lungfish skeleton) indicates
local transportation distances. The original habitat of the
fauna within this bed was likely to have been floodplain
pools, lakes or land surfaces, where animals may have
died in periods of drought. The abundance of plant mate-
rial within the sandy siltstone beds indicates vegetated
floodplains, and rooting structures indicate scrubby vege-
tation to forested landscapes (Kearsey et al. 2016). Heavy
rainfall on the floodplain then transported the fossil and
plant material in a mud-supported debris flow, to be
deposited within a floodplain lake. The microfossil sample
3 assemblage represents quieter deposition within a flood-
plain lake, affected by desiccation, then subject to one
small flood event that infilled the desiccation cracks.
In the Carboniferous, many groups of actinopterygians,
as well as rhizodonts, have been found in palaeoenviron-
ments that span salinity gradients, suggesting that they
were euryhaline or brackish–freshwater tolerant at this
time (Carpenter et al. 2014, 2015; 
O Gog
ain et al. 2016).
Early Carboniferous eurypterids are mostly restricted to
brackish or freshwater environments (Braddy 2001; Lams-
dell & Braddy 2010). A brackish habit was recently con-
firmed for the Famennian East Greenland tetrapods, long
considered to have been part of a freshwater fauna
(Goedert et al. 2018). The microfossil content of the three
samples is different from that identified from two dolo-
stone beds from the Ballagan Formation on the Isle of
Bute, which contain actinopterygians, sarcopterygians,
dipnoans, elasmobranchs and non-gyracanth acanthodians
(Carpenter et al. 2014). The latter two groups are absent
from the TIM, as are Chondrites and Phycosiphon-like
burrows, which are common within the dolostones (Ben-
nett et al. 2017). The dolostones are thought to form in
saline, coastal lakes subject to periodic influx of marine
waters in storms. Burrows are not commonly identified
within sandy siltstones in this formation (Bennett et al.
2016), however some fossils do indicate a marine influ-
ence. Palaeozoic Spirorbis has been interpreted to be of a
marine origin, with a mechanism of larval transport onto
coastal floodplains attributed to transport during storms
or by tides (Gierlowski-Kordesch & Cassle 2015). It is
likely that the laminated grey siltstone deposit was formed
in a floodplain lake that was influenced by a relatively
minor marine input.
Palaeoecology
The TIM fauna lived on a vegetated floodplain, centred
in and around water bodies. The vertebrates were
actinopterygians, holocephalan and gyracanth chon-
drichthyans, and several kinds of sarcopterygians: rhi-
zodonts, lungfish and tetrapods (Table 1; Fig. 19). Living
alongside them were eurypterids and myriapods (Smith-
son et al. 2012), as well as various microinvertebrates.
Rhizodonts would have been the apex predators, presum-
ably feeding on other taxa as well as each other. It is
likely that gyracanths fed on small prey in the water col-
umn, whereas tetrapods were probably demersal fauni-
vores, and possibly semiaquatic as well. Lungfish and
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 23
holocephalans would have taken a range of prey, probably
overlapping in their consumption with the sediment-
mining eurypterids. Myriapods lived on land, consuming
plants and available organic detritus.
The ecological relationships that are emerging from
within the Ballagan Formation (CEB unpub. data)
emphasize the role of diversifying non-marine inverte-
brates in providing a wider base for Carboniferous biotas
relative to Devonian ones. Several lines of evidence are
consistent with this hypothesis. The taxonomic diversifi-
cation of holocephalans (Sallan et al. 2011; Richards et al.
2018) and lungfish (Smithson et al. 2015) during the
Tournaisian and Visean has been noted previously. In this
context it is worth noting that toothplates are highly
effective in immobilizing elusive, soft-bodied prey through
massive trauma (MIC pers. obs.) and that on examination,
multiple Early Carboniferous holocephalans have previ-
ously neglected marginal dentition. These suggest that
multiple taxa took advantage of an increasing abundance
and diversity of small invertebrate prey. This hypothesis
should be explored further as more fossils are described
from the Ballagan and other Tournaisian deposits.
The consistency in taxonomic identities and numerical
proportions in the micro- and macrofossil samples (Otoo
et al. 2018, micropalaeontology data) suggests that there
is a common signal being captured by both. In particular,
the low number of actinopterygian specimens and large
number of rhizodont specimens probably at least some-
what reflect genuine paucity and abundance rather than
solely preservation bias. Both a single actinopterygian and
a single rhizodont will produce numerous scales with
high preservation potential, and that the TIM rhizodonts
are so much more in evidence than the actinopterygians
is striking. However, low relative abundance and diversity
of actinopterygians is a common feature of both Devo-
nian and Carboniferous non-marine settings (Cressler
et al. 2010; Sallan & Coates 2010; Carpenter et al. 2015;

O Gog
ain et al. 2016); at least through the early part of
the Late Carboniferous, the increasing taxonomic, mor-
phological and ecological diversity of actinopterygians is
considered to be largely a brackish and, in particular,
marine phenomenon (Sallan & Coates 2010, 2013). More
abundant and morphologically diverse actinopterygians
have been reported from Blue Beach, where the succes-
sion preserves multiple marine incursions (Mansky &
Lucas 2013).
The rhizodont occurences in the TIM fit a broader pat-
tern. Rhizodonts are often represented by two species in
Carboniferous localities (Sallan & Coates 2010; Carpenter
et al. 2014, 2015; 
O Gog
ain et al. 2016). Common associa-
tions are Archichthys/Strepsodus and Screbinodus/Rhizodus,
which has long had a confounding effect on the taxonomy
of these genera (Andrews 1985; Jeffery 2006). Screbinodus is
a small rhizodont, with a length of 1.5–2 m; Strepsodus and
Rhizodus are both large rhizodonts, with length estimates of
3–5 and 5–7 m, respectively (Jeffery 2012). Given the lim-
ited material, size estimates have not been produced for
Archichthys. The TIM Strepsodus material indicates individ-
uals across a range of sizes, the largest probably about 1 m
in length. This parallels the rhizodonts of the Foulden
locality, where Andrews (1985) identified multiple ‘small
form’ individuals that she suggested were juveniles of the
‘large form’ that lived elsewhere; all these were later referred
to Strepsodus by Jeffery (2006). This suggests that size was
an important ecological discriminant both within and
between rhizodont species.
The small size of the referred lungfish toothplates
might appear to support Sallan & Galimberti’s (2015)
F IG . 19 . Reconstruction of the
Burnmouth TIM fauna. From left to
right: rhizodont, gyracanth, tetra-
pod, actinopterygian, myriapod
(lower), and eurypterid (upper).
Artwork by Yasmin Yonan (Univer-
sity of Leicester, 2015).
24 PALAEONTOLOGY
conclusion of a post-Devonian size reduction. However,
35 m above the Devonian/Carboniferous boundary at
Burnmouth there is evidence of both very small and very
large lungfish, with very large lungfish also occurring
20 m above the TIM (TRS pers. obs.; T. Challands
unpub. data; Clack et al. 2018). There are also gyracanth
and rhizodont fossils from outside the TIM that represent
larger individuals (BKAO pers. obs.) Therefore, it does
not seem likely that organisms experienced concerted
size reduction at the extinction or in its aftermath. Fur-
ther sampling will allow greater examination of this
hypothesis.
Faunal analyses
The diversity and taxonomic composition of the Mill Hole
fauna is most similar to that of the TIM (Carpenter et al.
2014), including at least one shared species of rhizodont
(Strepsodus sauroides). Mill Hole is also in the Ballagan For-
mation and roughly coeval with the TIM, and these quali-
tative observations indicate that these assemblages sample a
coherent ‘Ballagan fauna’ (this study; CEB unpub. data)
However, unlike the TIM, the Mill Hole fauna is derived
from a dolostone as opposed to a siltstone. The fauna also
contains the elasmobranch Ageleodus and the sarcoptery-
gian Megalichthys (Carpenter et al. 2014); while the
actinopterygian material is similar in terms of content
(mostly scales and lepidotrichia) it is the most abundant
material at the locality (JAC pers. obs.) These details indi-
cate that Mill Hole is taxonomically and geologically sam-
pling a more marine signal than the TIM.
The persistent recovery of a Devonian/Carboniferous
split when the entire dataset is analysed with both CA
and NMDS supports the conclusion of Sallan & Coates
(2010). The persistence of this split when the marine sites
are removed suggests that the end-Devonian extinction
has a diversity signal in both marine and non-marine set-
tings. However, the losses were not evenly distributed
among groups; placoderms account for four of the taxo-
nomic divisions within this dataset and were eliminated
completely at the end of the Devonian. The Carbonifer-
ous non-marine gyracanth–rhizodont–tetrapod associa-
tion recovered by the correspondence analysis was
already in place in the Late Devonian, there often accom-
panied by tristichopterids and lungfish (Cressler et al.
2010), and usually porolepiformes and antiarchs as well.
In non-marine settings the end-Devonian extinction left
behind a faunal subset which does not seem to have been
greatly disturbed. On either side of the Devonian–Car-
boniferous boundary, rhizodonts are generally represented
by the same number of species per locality and tetrapods
greatly increase in diversity relative to the Devonian. The
fact that, when marine sites are removed, holocephalans
are associated with gyracanths, rhizodonts and tetrapods
(as is the case in the TIM) as opposed to the more
marine-inclined actinopterygians, elasmobranchs and
symmoriiformes, is interesting and may suggest different
environmental trajectories for elasmobranchs and holo-
cephalans in the Early Carboniferous.
The TIM and Devonian–Carboniferous faunal assembly
The TIM (vertebrate) fauna is very similar to that of the
Famennian Red Hill locality, as are their respective environ-
ments: both are coastal alluvial plains at low palaeolatitude,
though Burnmouth experienced greater rainfall (Retallack
et al. 2009; Kearsey et al. 2016). Indeed, the only major ver-
tebrate division not represented in similar numbers in the
TIM as at Red Hill are elasmobranchs (ctenacanths) and pla-
coderms (Cressler et al. 2010). Conversely, holocephalans
are absent from Red Hill. The rest of the fauna in both cases
is composed of gyracanths, tetrapods, actinopterygians,
lungfish and large predatory sarcopterygians (including rhi-
zodonts). The Famennian vertebrate fauna from East Green-
land, famous for Acanthostega and Ichthyostega, also has a
similar composition (Blom et al. 2007). It appears that the
TIM is sampling a faunal-environmental association that
apparently passed through the end-Devonian extinction
without extensive modification.
Much of this fauna is held in common with ‘typical’
Carboniferous coal swamp faunas such as Dora and Nid-
drie, and floodplain localities such as Gilmerton (Sallan &
Coates 2010), their qualitative affinities supported by the
results of the faunal analyses. The only characteristic coal
swamp taxon missing from the TIM are xenacanths,
which first appear in the Visean with Diplodoselache at
Wardie (this may be superseded by Tournaisian occur-
rences at Burnmouth; Clack et al. 2018) It would be
interesting to know the extent to which the apparent
transition of the more or less Devonian-type floodplain
fauna (as seen at Red Hill, East Greenland and, with
minor changes, in the TIM at Burnmouth) to the coal
swamp setting represents a physical move inland toward
fresher water or if the swamps developed on top of the
existing alluvial plains (the two scenarios are not mutually
exclusive). With the addition of xenacanths, the key dif-
ference between the floodplain faunal association and the
coal swamp association seems to be the increased abun-
dance and diversity of tetrapods (and arthropods), at least
in part driven by the increased resources and complexity
of terrestrial habitats. But overall, much of the non-mar-
ine faunal order in the Carboniferous can be described as
expansion of a discernable, pre-existing subset of Devo-
nian diversity. This contrasts with marine environments,
where, following the extinction of placoderms, the fauna
diversified greatly with the addition of large clades/
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 25
taxonomic divisions (Coates et al. 2017, 2018; Giles et al.
2017) to create very differently-composed marine faunas
compared to those that existed in the Devonian.
Yao et al. (2015) recovered isotope excursions in car-
bon and nitrogen from which they infer sea level fluctua-
tions with a net drop through the Tournaisian,
particularly in the second half of the stage. These changes
begin in the mid-Tournaisian and do not stabilize until
the early Visean. Further investigation of Tournaisian
environments preserved at Burnmouth and elsewhere is
needed to determine the environmental and biological
impact of these sea level changes. The presence of macro-
fossil assemblages throughout the Ballagan at Burnmouth,
starting from very near the Devonian–Carboniferous
boundary, indicates that floodplain biotas were able to
persist through these continued post-extinction environ-
mental changes. The physical and physiological ability to
move between different salinity regimes would doubtless
have been useful, and this interval may be responsible for
encouraging the apparent retention of euryhalinity in
many vertebrates throughout the Carboniferous.
It is not obvious to what extent these faunal transitions
were accompanied by ecological restructuring. Placoderms
were extremely numerous at Red Hill, East Greenland
and other Late Devonian localities, and had a diversity of
morphologies and feeding ecologies; their extinction at
the end of the Devonian must have had ecological
impacts, but what those were is currently unclear. Also
unknown are the impacts of the increased diversity and
terrestrialization of tetrapods and arthropods during the
Carboniferous. Future comparative ecological work will
be valuable for understanding these issues.
CONCLUSIONS
Despite post-dating the end-Devonian mass extinction by
only a few million years, the TIM fauna contains multiple
invertebrate and vertebrate taxa across different ecological
roles. As in environmentally similar Late Devonian assem-
blages, actinopterygians are low in diversity and abun-
dance, with the assemblage dominated numerically and
taxonomically by sarcopterygians. The TIM lacks the pla-
coderms of the Devonian and the tetrapod diversity and
xenacanths found in later Carboniferous biotas, but other-
wise seems to represent a floodplain faunal association that
persisted from the Late Devonian into the Carboniferous.
Either ecologically or evolutionarily, this floodplain associ-
ation may have formed the basis of the coal swamp faunas
that characterize many Carboniferous localities. Insofar as
the Carboniferous is marked by a diversification of
actinopterygians and elasmobranchs, during the Tour-
naisian these events may have been happening in different
environmental or faunal contexts (Mansky & Lucas 2013).
This study and other work (Mansky & Lucas 2013;
Carpenter et al. 2014; Anderson et al. 2015; Clack et al.
2016) have focused primarily on taxonomic and phyloge-
netic changes through the Devonian–Carboniferous tran-
sition and Romer’s Gap. These data are providing a basis
for future work linking taxonomy and phylogeny to ecol-
ogy, which will provide an enhanced perspective on the
biological and environmental changes through this
important period in Earth history.
Acknowledgements. This work was funded by NERC consortium
grants NEJ021067/1 (BGS), NE/J022713/1 (Cambridge), NE/
J020729/1 (Leicester), NE/J020621/1 (NMS), and NE/J021091/1
(Southampton), as well as an Evan Carroll Commager Fellowship
for Graduate Study in Paleontology from Amherst College. Most
of this research was conducted by BKAO in 2014–2015 for an
MPhil project under the supervision of JAC at the University of
Cambridge. We thank Anne Brown and Colin MacFadyen at Scot-
tish Natural Heritage for permission to collect at Site of Special
Scientific Interest under their care, Paul Bancks from the Edin-
burgh office of The Crown Estate for permission to collect from
the foreshore at Burnmouth, members of the TW:eed Project team
for help and support during the excavation of the Burnmouth site,
Sarah Finney and the Department of Earth Sciences, University of
Cambridge, for help and guidance and the use of lab facilities dur-
ing the preparation of the bulk samples recovered from Burn-
mouth, Keturah Smithson for scanning the specimens and help
with preparing the rendered images, Nick Fraser and Stig Walsh
(NMS) and Matt Lowe (UMZC) for collections access, and the
community of Burnmouth for their support and interest during
the TW:eed Project. Yasmin Yonan (University of Leicester) pro-
vided the reconstruction of the Burnmouth fauna. Graham Slater
provided valuable advice on computational methods. TIK pub-
lishes with the permission of the Executive Director, British Geo-
logical Survey (NERC). Two anonymous referees commented on
an earlier version of the manuscript.
DATA ARCHIVING STATEMENT
Data for this study, including faunal diversity datasets and
micropalaeontological data, are available in the Dryad Digital Repos-
itory: https://doi.org/10.5061/dryad.j5t58j4
Editor. Marcello Ruta
REFERENCES
ANDERSON, J. S., SMITHSON, T. R., MANSKY, C.
F., MEYER, T. and CLACK, J. A. 2015. A diverse
tetrapod fauna at the base of ‘Romer’s Gap’. PLoS One, 10,
1–27.
ANDREWS, S. M. 1985. Rhizodont crossopterygian fish from
the Dinantian of Foulden, Berwickshire, Scotland, with a re-
evaluation of this group. Transactions of the Royal Society of
Edinburgh: Earth Sciences, 76, 67–95.
26 PALAEONTOLOGY
-and WESTOLL, T. S. 1970. XII.—The postcranial skeleton
of Rhipidistian fishes excluding Eusthenopteron. Transactions of
the Royal Society of Edinburgh: Earth Sciences, 68, 391–489.
BENNETT, C. E., S IVETER, D. J., DAVIES , S. J., WIL-
LIAMS, M., WILKINSON, I. P., BROWNE, M. A. E.
and MILLER, C. G. 2012. Ostracods from freshwater and
brackish environments of the Carboniferous of the Midland
Valley of Scotland: the early colonization of terrestrial water
bodies. Geological Magazine, 149, 366–396.
-KEARSEY, T. I., DAVIES, S. J., MILLWARD, D.,
CLACK, J. A., SMITHSON, T. R. and MARSHALL, J.
E. A. 2016. Early Mississippian sandy siltstones preserve rare
vertebrate fossils in seasonal flooding episodes. Sedimentology,
63, 1677–1700.
-HOWARD, A. S., DAVIES, S. J., KEARSEY, T. I.,
MILLWARD, D., BRAND, P. J., BROWNE, M. A. E.,
REEVES , E. J. and MARSHALL, J. E. A. 2017. Ichnofauna
record cryptic marine incursions onto a coastal floodplain at a
key Lower Mississippian tetrapod site. Palaeogeography,
Palaeoclimatology, Palaeoecology, 468, 287–300.
BINNEY, E. W. 1841. On the fossil fishes of the Pendleton
coal field. Transactions of the Manchester Geological Society, 1,
153–178.
BLOM, H., CLACK, J. A., AHLBERG, P. E. and FRIED-
MAN, M. 2007. Devonian vertebrates from East Greenland: a
review of faunal composition and distribution. Geodiversitas,
29, 119–141.
BONAPARTE, C. L. 1831. Saggio di una distribuzione metod-
ica degli animali vertebrati. Giornale Arcadico di Scienze, 49,
1–77.
BOOMER, I., HORNE, D. J. and SLIPPER, I. J. 2003. The
use of ostracods in palaeoenvironmental studies, or what can
you do with an ostracod shell? 153–179. In PARK, L. E. and
SMITH, A. J. (eds). Bridging the gap: Trends in the ostracode
biological and geological sciences. The Paleontological Society
Papers, 9.
BRADDY, S. J. 2001. Eurypterid palaeoecology: palaeobiologi-
cal, ichnological and comparative evidence for a ‘mass-moult-
mate’ hypothesis. Palaeogeography, Palaeoclimatology, Palaeoe-
cology, 172, 115–132.
BRAY, J. R. and CURTIS , J. T. 1957. An ordination of the
Upland Forest communities of Southern Wisconsin. Ecological
Monographs, 27, 325–349.
BRAZEAU, M. D. 2005. A new genus of rhizodontid (Sar-
copterygii, Tetrapodomorpha) from the Lower Carboniferous
Horton Bluff Formation of Nova Scotia, and the evolution of
the lower jaws in this group. Canadian Journal of Earth
Sciences, 42, 1481–1499.
CARPENTER, D., FALCON-LANG, H. J., BENTON, M.
J. and NELSON, W. J. 2011. Fishes and tetrapods in the
Upper Pennsylvanian (Kasimovian) Cohn Coal Member of
the Mattoon Formation of Illinois, United States: systemat-
ics, paleoecology, and paleoenvironments. Palaios, 26, 639–
657.
CARPENTER, D. K., FALCON-LANG, H. J., BENTON,
M. J. and HENDERSON, E. 2014. Carboniferous (Tour-
naisian) fish assemblages from the Isle of Bute, Scotland: sys-
tematics and palaeoecology. Palaeontology, 57, 1215–1240.
---and GREY M. 2015. Early Pennsylvanian
(Langsettian) fish assemblages from the Joggins Formation,
Canada, and their implications for palaeoecology and palaeo-
geography. Palaeontology, 58, 661–690.
CLACK, J. A. 2002. An early tetrapod from ‘Romer’s Gap’.
Nature, 418, 72–76.
-and FINNEY, S. M. 2005. Pederpes finneyae, an articu-
lated tetrapod from the Tournaisian of Western Scotland.
Journal of Systematic Palaeontology, 2, 311–346.
-BENNETT, C. E., CARPENTER, D. K., DAVIES , S.
J., FRASER, N. C., KEARSEY, T. I., MARSHALL, J. E.
A., MILLWARD, D., OTOO, B. K. A., REEVES, E. J.,
ROSS , A. J., RUTA, M., SMITHSON, K. Z., SMITH-
SON, T. R. and WALSH, S. A. 2016. Phylogenetic and
environmental context of a Tournaisian tetrapod fauna. Nat-
ure Ecology & Evolution, 1, 1–11.
--DAVIES , S. J., SCOTT, A. C., SHERWIN, J.
and SMITHSON, T. R. 2018. A Tournaisian (earliest Car-
boniferous) conglomerate-preserved non-marine faunal assem-
blage and its environmental and sedimentological context.
PeerJ Preprints, 6, e27102v1. https://doi.org/10.7287/peerj.pre
prints.27102v1
CLARKSON, E. N. K. 1985. Palaeoecology of the Dinantian of
Foulden, Berwickshire, Scotland. Transactions of the Royal
Society of Edinburgh: Earth Sciences, 76, 97–100.
-MILNER, A. R. and COATES , M. I. 1994. Palaeoecol-
ogy of the Vis
ean of East Kirkton, West Lothian, Scotland.
Transactions of the Royal Society of Edinburgh: Earth Sciences,
84, 417–425.
COATES , M. I. and CLACK, J. A. 1995. Romer’s Gap: tetra-
pod origins and terrestriality. Bulletin du Mus
eum national
d’Histoire naturelle C, 17, 373–388.
-GESS, R. W., F INARELLI , J. A., CRISWELL, K. E.
and TIETJEN, K. 2017. A symmoriiform chondrichthyan
braincase and the origin of chimaeroid fishes. Nature, 541,
208–211.
-FINARELLI , J. A., SANSOM, I. J., ANDREEV, P. S.,
CRISWELL, K. E., T IETJEN, K., RIVERS , M. L. and
LA RIVIERE, P. J. 2018. An early chondrichthyan and the
evolutionary assembly of a shark body plan. Proceedings of the
Royal Society B, 285, 20172418.
COPE, E. D. 1887. The origin of the fittest. Appleton, New
York, 536 pp.
CRESSLER, W. L., DAESCHLER, E. B., SLINGER-
LAND, R. and PETERSON, D. A. 2010. Terrestrialization
in the Late Devonian: a palaeoecological overview of the Red
Hill site, Pennsylvania, USA. Geological Society, London, Special
Publications, 339, 111–128.
DAESCHLER, E. B. 2000. An early actinopterygian fish from
the Catskill formation (Late Devonian, Famennian) in Penn-
sylvania, USA. Proceedings of the Academy of Natural Sciences
of Philadelphia, 150, 181–192.
DAVIS , M. C., SHUBIN, N. H. and DAESCHLER, E. B.
2001. Immature rhizodontids from the Devonian of North
America. Bulletin of the Museum of Comparative Zoology, 156,
173–187.
FALCON-LANG, H. J. 1999. The Early Carboniferous
(Courceyan–Arundian) monsoonal climate of the British Isles:
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 27
evidence from growth rings in fossil woods. Geological Maga-
zine, 136, 177–187.
FRIEDMAN, M. and BLOM, H. 2006. A new actinoptery-
gian from the Famennian of East Greenland and the interrela-
tionships of Devonian ray-finned fishes. Journal of
Paleontology, 80, 1186–1204.
-and SALLAN, L. C. 2012. Five hundred million years of
extinction and recovery: a Phanerozoic survey of large-scale
diversity patterns in fishes. Palaeontology, 55, 707–742.
GARVEY, J. M., JOHANSON, Z. and WARREN, A. 2005.
Redescription of the pectoral fin and vertebral column of the rhi-
zodontid fish Barameda decipiens from the Lower Carboniferous
of Australia. Journal of Vertebrate Paleontology, 25, 8–18.
GIERLOWSKI-KORDESCH, E. H. and CASSLE , C. F.
2015. The ‘Spirorbis’ problem revisited: sedimentology and
biology of microconchids in marine-nonmarine transitions.
Earth-Science Reviews, 148, 209–227.
GILES, S., XU, G. H., NEAR, T. J. and FRIEDMAN, M.
2017. Early members of ‘living fossil’ lineage imply later origin
of modern ray-finned fishes. Nature, 549, 265–268.
GOEDERT, J., L
ECUYER, C., AMIOT, R., ARNAUD-
GODET, F., WANG, X., CUI , L., CUNY, G., DOUAY,
G., FOUREL, F., PANCZER, G., S IMON, L., STEYER,
J. and ZHU, M. 2018. Euryhaline ecology of early tetrapods
revealed by stable isotopes. Nature, 558, 68–72.
GOODRICH, E. S. 1930. Studies on the structure and develop-
ment of vertebrates. Macmillan, London, 873 pp.
GREIG, D. C. 1988. Geology of the Eyemouth district. Memoir
of the British Geological Survey, Sheet 34.
HAMMER, Ø. 2015. Palaeontological community and diversity
analysis – brief notes. Pal€aontologisches Institut und Museum,
Z€urich, 1–36.
HUXLEY, T. H. 1880. On the application of the laws of evolu-
tion to the arrangement of the Vertebrata and more particular
the Mammalia. Proceedings of the Zoological Society of London,
1880, 649–662.
JEFFERY, J. E. 2006. The Carboniferous fish genera Strepsodus
and Archichthys (Sarcopterygii: Rhizodontida): clarifying
150 years of confusion. Palaeontology, 49, 112–132.
-2012. Cranial morphology of the Carboniferous rhizodon-
tid Screbinodus ornatus (Osteichthyes: Sarcopterygii). Journal
of Systematic Palaeontology, 10, 475–519.
JOHANSON, Z. and AHLBERG, P. E. 2001. Devonian
rhizodontids and tristichopterids (Sarcopterygii;
Tetrapodomorpha) from East Gondwana. Earth & Environ-
mental Science Transactions of the Royal Society of Edinburgh,
92, 43–74.
KEARSEY, T. I., BENNETT, C. E., MILLWARD, D.,
DAVIES , S. J., GOWING, C. J. B., KEMP, S. J., LENG,
M. J., MARSHALL, J. E. A. and BROWNE, M. A. E.
2016. The terrestrial landscapes of tetrapod evolution in earli-
est Carboniferous seasonal wetlands of SE Scotland. Palaeo-
geography, Palaeoclimatology, Palaeoecology, 457, 52–69.
LAMSDELL, J. C. and BRADDY, S. J. 2010. Cope’s Rule
and Romer’s theory: patterns of diversity and gigantism in
eurypterids and Palaeozoic vertebrates. Biology Letters, 6, 265–
269.
LOMBARD, R. E. and BOLT, J. R. 1995. A new primitive
tetrapod, Whatcheeria deltae, from the Lower Carboniferous of
Iowa. Palaeontology, 38, 471–494.
LONG, J. A. 1989. A new rhizodontiform fish from the Early
Carboniferous of Victoria, Australia, with remarks on the phy-
logenetic position of the group. Journal of Vertebrate Paleon-
tology, 9, 1–17.
MANSKY, C. F. and LUCAS, S. G. 2013. Romer’s Gap revis-
ited: continental assemblages and ichno-assemblages from the
basal Carboniferous of Blue Beach, Nova Scotia, Canada. New
Mexico Museum of Natural History & Science Bulletin, 60,
244–273.
MICKLE, K. E. 2011. The Early Actinopterygian fauna of the
Manning Canyon Shale Formation (Upper Mississippian,
Lower Pennsylvanian) of Utah, U.S.A. Journal of Vertebrate
Paleontology, 31, 962–980.
-2017. The lower actinopterygian fauna from the Lower
Carboniferous Albert shale formation of New Brunswick,
Canada – a review of previously described taxa and a descrip-
tion of a new genus and species. Fossil Record, 20, 47–67.
M €ULLER, J. 1845. €Uber den Bau und die Grenzen der Ganoi-
den, und €uber dat nat€urliche System der Fishe. Abhandlungen
der K€oniglichen Akademie der Wissenschafen zu Berlin, 1844,
117–216.

O GOG 
AIN, A., FALCON-LANG, H. J., CARPENTER,
D. K., MILLER, R. F., BENTON, M. J., PUFAHL, P. K.,
RUTA, M., DAVIES , T. G., HINDS, S. J. and STIM-
SON, M. R. 2016. Fish and tetrapod communities across a
marine to brackish salinity gradient in the Pennsylvanian
(early Moscovian) Minto Formation of New Brunswick,
Canada, and their palaeoecological and palaeogeographical
implications. Palaeontology, 59, 689–724.
OBRUCHEV, D. V. 1953. Studies on edestids and the works
of A. P. Karpinski. U.S.S.R. Academy of Sciences, Works of the
Palaeontological Institute, 45, 1–86.
OTOO, B. K. A., CLACK, J. A., SMITHSON, T. R.,
BENNETT, C. E., KEARSEY, T. I. and COATES , M.
I. 2018. Data from: A fish and tetrapod fauna from
Romer’s Gap preserved in Scottish Tournaisian floodplain
deposits. Dryad Digital Repository. https://doi.org/10.5061/
dryad.j5t58j4
PARDO, J. D., SZOSTAKIWSKYJ , M., AHLBERG, P. E.
and ANDERSON, J. S. 2017. Hidden morphological diver-
sity among early tetrapods. Nature, 546, 642–645.
PATTERSON, C. 1965. The phylogeny of the chimaeroids.
Philosophical Transactions of the Royal Society B, 249, 109–219.
RETALLACK, G. J., HUNT, R. R. and WHITE, T. S. 2009.
Late Devonian tetrapod habitats indicated by palaeosols in
Pennsylvania. Journal of the Geological Society, 166, 1143–1156.
RICHARDS, K., SHERWIN, J., SMITHSON, T. R.,
BENNION, R., DAVIES , S. J., MARSHALL, J. and
CLACK, J. A. 2018. Diverse and durophagous: early Car-
boniferous chondrichthyans from the Scottish Borders. Earth
& Environmental Science Transactions of the Royal Society of
Edinburgh, 108, 67–87.
ROMER, A. S. 1955. Herpetichthyes, Amphibioidei, Choa-
nichthyes or Sarcopterygii? Nature, 176, 126.
28 PALAEONTOLOGY
-1956. The early evolution of land vertebrates. Proceedings of
the American Philosophical Society, 100, 157–167.
RUST, B. R. and NANSON, G. C. 1989. Bedload transport of
mud as pedogenic aggregates in modern and ancient rivers.
Sedimentology, 36, 291–306.
SALLAN, L. C. 2014. Major issues in the origins of ray-finned
fish (Actinopterygii) biodiversity. Biological Reviews, 89, 950–971.
-and COATES , M. I. 2010. End-Devonian extinction and
a bottleneck in the early evolution of modern jawed verte-
brates. Science, 107, 10131–10135.
--2013. Styracopterid (Actinopterygii) ontogeny and
the multiple origins of post-Hangenberg deep-bodied fishes.
Zoological Journal of the Linnean Society, 169, 156–199.
SALLAN, L. and GALIMBERTI , A. K. 2015. Body-size
reduction in vertebrates following the end-Devonian mass
extinction. Science, 350, 812–815.
SALLAN, L. C., KAMMER, T. W., AUSICH, W. I. and
COOK, L. A. 2011. Persistent predator–prey dynamics
revealed by mass extinction. Proceedings of the National Acad-
emy of Sciences, 108, 8335–8338.
SCHINDLER, T. 2018. Revision of Rhabdolepis macropterus
(Bronn, 1829) (Osteichthyes, lower Actinopterygii; Lower Per-
mian, SW Germany). PalZ, 10 pp. https://doi.org/10.1007/
s12542-018-0410-z
SMITH, M. M., SMITHSON, T. R. and CAMPBELL, K.
S. W. 1987. The relationships of Uronemus: a carboniferous
dipnoan with highly modified tooth plates. Philosophical
Transactions of the Royal Society B, 317, 299–327.
SMITHSON, T. R. 1982. The cranial morphology of
Greererpeton burkemorani Romer (Amphibia: Tem-
nospondyli). Journal of the Linnean Society of London, Zool-
ogy, 76, 29–90.
-WOOD, S. P., MARSHALL, J. E. A. and CLACK, J.
A. 2012. Earliest Carboniferous tetrapod and arthropod faunas
from Scotland populate Romer’s Gap. Proceedings of the
National Academy of Sciences, 109, 4532–4537.
-RICHARDS, K. R. and CLACK, J. A. 2015. Lungfish
diversity in Romer’s Gap: reaction to the end-Devonian
extinction. Palaeontology, 59, 29–44.
SNYDER, D. 2011. Gyracanthid gnathostome remains from
the Carboniferous of Illinois. Journal of Vertebrate Paleontol-
ogy, 31, 902–906.
STAHL, B. J. 1999. Chondrichthyes III: Holocephali. 1–164. In
SCHULTZE, H.-P. (ed.) Handbook of Paleoichthyology. Vol.
4. Friedrich Pfeil, Munich, 164 pp.
SWEETMAN, S. C. and INSOLE, A. N. 2010. The plant
debris beds of the Early Cretaceous (Barremian) Wessex
Formation of the Isle of Wight, southern England: their gene-
sis and palaeontological significance. Palaeogeography, Palaeo-
climatology, Palaeoecology, 292, 409–424.
TRAQUAIR, R. H. 1873. On Phaneropleuron andersoni Huxley
and Uronemus lobatus Agassiz. Journal of the Royal Geological
Society of Ireland, 3, 41–47.
TURNER, S., BURROW, C. J. and WARREN, A. 2005.
Gyracanthides hawkinsi sp. nov. (Acanthodii, Gyracanthidae)
from the Lower Carboniferous of Queensland, Australia, with
a review of gyracanthid taxa. Palaeontology, 48, 963–1006.
WAKELIN-KING, G. A. and WEBB, J. A. 2007a. Upper-
flow- regime mud floodplains, lower-flow-regime sand chan-
nels: sediment transport and deposition in a drylands mud-
aggregate river. Journal of Sedimentary Research, 77, 702–712.
--2007b. Threshold- dominated fluvial styles in an arid-
zone mud-aggregate river: the uplands of Fowlers Creek, Aus-
tralia. Geomorphology, 85, 114–127.
WARREN, A., CURRIE , B. P., BURROW, C. J. and
TURNER, S. 2000. A redescription and reinterpretation of Gyra-
canthides murrayi Woodward 1906 (Acanthodii, Gyracanthidae)
from the Lower Carboniferous of the Mansfield Basin, Victoria,
Australia. Journal of Vertebrate Paleontology, 20, 225–242.
WELLSTEAD, C. F. 1982. A Lower Carboniferous a€ıstopod
amphibian from Scotland. Palaeontology, 25, 193–208.
WILLIAMS, M., STEPHENSON, M., WILKINSON, I. A.
N. P., LENG, M. J. and MILLER, C. G. 2005. Early Car-
boniferous (Late Tournaisian–Early Vis
ean) ostracods from
the Ballagan Formation, central Scotland, UK. Journal of
Micropalaeontology, 24, 77–94.
-LENG, M. J., STEPHENSON, M. H., ANDREWS, J.
E., WILKINSON, I. P., S IVETER, D. J., HORNE, D. J.
and VANNIER, J. M. C. 2006. Evidence that Early Carbonif-
erous ostracods colonised coastal flood plain brackish water
environments. Palaeogeography, Palaeoclimatology, Palaeoecol-
ogy, 230, 299–318.
WILSON, C. D., PARDO, J. D. and ANDERSON, J. S.
2018. A primitive actinopterygian braincase from the Tournaisian
of Nova Scotia. Proceedings of the Royal Society B, 5, 171727.
YAO, L., QIE , W., LUO, G., LIU, J., ALGEO, T. J., BAI ,
X., YANG, B. and WANG, X. 2015. The TICE event: per-
turbation of carbon–nitrogen cycles during the mid-Tournai-
sian (Early Carboniferous) greenhouse–icehouse transition.
Chemical Geology, 401, 1–14.
ZHU, M., AHLBERG, P. E., ZHAO, W. J. and J IA, L. T.
2017. A Devonian tetrapod-like fish reveals substantial paral-
lelism in stem tetrapod evolution. Nature Ecology & Evolution,
1, 1470–1476.
OTOO ET AL . : SCOTT ISH TOURNAIS IAN VERTEBRATE FAUNA 29