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Zoological Journal of the Linnean Society, 2024, XX, 1–31
hps://doi.org/10.1093/zoolinnean/zlae065
Advance access publication 18 June 2024
Original Article
Received 18 August 2023; revised 21 March 2024; accepted 29 April 2024
Original Article
Micro-CT data reveal new information on the
craniomandibular and neuroanatomy of the dicynodont
Gordonia (erapsida: Anomodontia)
from the late Permian of Scotland
Hady George1,2,*, Christian F. Kammerer3–5, Davide Foa6–8, Neil D. L. Clark9,
Stephen L. Brusae2
1School of Earth Sciences, Life Sciences Building, University of Bristol, Tyndall Avenue, Bristol, BS8 1TQ, United Kingdom
2School of GeoSciences, University of Edinburgh, Grant Institute, James Huon Road, Edinburgh, Scotland EH9 3FE, United Kingdom
3North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601, United States
4Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, United States
5Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 2050, South Africa
6Department of Geosciences, Virginia Tech, Derring Hall 926 West Campus Drive, Blacksburg 24061, VA, United States
7School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2, United Kingdom
8National Museums Scotland, Chambers Street, Edinburgh, Scotland EH1 1JF, United Kingdom
9e Hunterian, University of Glasgow, University Avenue, Glasgow, Scotland G12 8QQ, United Kingdom
*Corresponding author. School of Earth Sciences, Life Sciences Building, University of Bristol, Tyndall Avenue, Bristol, BS8 1TQ, United Kingdom. E-mail:
houdzgeorge@gmail.com or xk23822@bristol.ac.uk
ABSTRACT
Dicynodontia was an abundant, globally widespread clade of Permo-Triassic synapsids on the stem lineage of mammals. Although there is an
extensive body of literature on dicynodont craniomandibular anatomy, only recently has the power of computed tomographic (CT) scanning
been applied to this system. CT-assisted research on dicynodonts has focused on the smallest members of the clade, while larger dicynodonts
(particularly the members of the diverse, long-ranging subclade Bidentalia) have received comparatively lile aention. Here, we work towards
lling that gap by presenting a µCT-assisted reconstruction of ‘e Elgin Marvel’, a bidentalian specimen consisting of a complete cranium and
mandible from late Permian deposits near Elgin, Scotland, which historically has been dicult to study because of its unusual preservation as
void space in sandstone. is specimen can be referred to Gordonia, which is solely represented by moulds of void specimens. e µCT data
reveal new information on the palate and endocranium of this taxon that could not previously be gleaned from physical moulds made from the
void specimens. A phylogenetic analysis indicates that Gordonia and the Chinese Jimusaria form a clade of bidentalians characterized by narrow
pterygoid medial plates, expanding our understanding of late Permian biogeography. e endocast of Gordonia is similar to that of other non-
cynodont therapsids, and has a remarkably enlarged pineal body, probably related to exaggeration of the sagial crest. Comparisons of enceph-
alization quotients (EQ), a measure of brain size relative to body size, reveal Gordonia has a similar EQ to most other non-cynodont therapsids.
Keywords: Dicynodontia; endocast; phylogeny; Permian; Scotland; Synapsida; erapsida; µCT
INTRODUCTION
Dicynodontia is one of the major subclades of Synapsida, the
clade containing mammals and their extinct relatives. e di-
cynodont lineage lasted for tens of millions of years, from the
middle Permian to the end of the Triassic, surviving the end-
Permian mass extinction, and included an ecologically diverse
set of species ranging from mole-sized burrowers to elephant-
sized browsers (Cox 1972, Barry 1974, Hoon 1986, King 1988,
1990, Angielczyk and Kammerer 2018, Sulej and Niedźwiedzki
2018). Dicynodonts have been found on every continent and
are oen the most abundant fossil tetrapods in the assemblages
where they occur (King 1990, Fröbisch 2009, Smith et al. 2012).
© 2024 e Linnean Society of London.
is is an Open Access article distributed under the terms of the Creative Commons Aribution License (hps://creativecommons.org/licenses/by/4.0/), which permits
unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
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2 • George et al.
Generally, if there is a terrestrial vertebrate-bearing assemblage
of middle Permian to Early Triassic age, it probably includes di-
cynodonts.
A case in point is the Permian tetrapod record from the north
of Scotland. late Permian continental sandstones are exposed in
the area surrounding Elgin, Moray, which have long been quar-
ried for building stone (Benton and Walker 1985) (Fig. 1A).
Body fossils in these deposits are exceedingly rare and dicult to
nd (although ichnofossils are locally abundant; Sarjeant 1974,
Benton and Walker 1985). Nonetheless, dicynodont skeletal re-
mains have been known there since the 19th century (Newton
1893). e paucity of body fossil discoveries can be aributed
in part to the unusual local preservation, which consists of three-
dimensional void spaces (moulds) within aeolian sandstone,
formed by the dissolution of the bone (Benton and Walker 1985,
Benton and Spencer 1995). Such fossils can be hard to recognize
in situ (appearing only as empty cavities in the rock) and even
once collected, their study has historically been a complicated
process. Sandstone blocks containing the moulds were generally
broken apart in the process of creating physical casts made of
rubbery materials [like gua-percha (natural latex) and silicone]
for study (Benton and Walker 1985). is process is detrimental
to the original fossils, hindering future research from being car-
ried out on them, and has contributed to the limited information
available on the morphology of the Permian and Triassic ‘Elgin
Reptiles’ (see: Rowe 1980, Cruickshank et al. 2005, Benton and
Walker 2011, Foa et al. 2020, 2022).
Newton (1893) originally described six species of Permian
‘Elgin Reptiles’ from the Cuies Hillock quarry west of Elgin:
the pareiasaur Elginia mirabilis, the cryptodont dicynodont
Geikia elginensis, and four species of the dicynodontoid dicyno-
dont Gordonia: the type species G. traquairi plus G. huxleyana,
G. duana, and G. juddiana. ese species were represented by
skulls and some postcranial material that were recovered from
the Cuies Hillock Formation, which is believed to be roughly
of Changhsingian age based on faunal similarities with the latest
Elgin
N
1mk2
0
Clashach quarry
Cutties Hillocks quarry
Cutties Hillocks
Formation
Hopeman Sandstone
Formation
AB
CD
Figure 1. Location of Elgin and surrounding area within the British Isles (A), location of the quarries and latest Permian formation outcrop
near Elgin (B), ELGNM 1999.5.1 (‘e Elgin Marvel’) (C), and GLAHM 114914; a stereolithograph of ELGNM 1999.5.1 and .2 that was
presented by Clark et al. (2004) and described by Cruickshank et al. (2005) (D).
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Any update • 3
Permian Daptocephalus Assemblage Zone of the South African
Karoo Basin (King 1988, Groenewald and Kitching 1995,
Rubidge 1995, Vigliei et al. 2016, Lucas 2018).
Since Newton’s (1893) original description, there have been
various aempts to revise the taxonomy of Gordonia and its
four component species. Von Huene (1940) synonymized the
genus with Dicynodon, but retained all four species as valid.
Although some subsequent workers (Janensch 1952, Anderson
and Cruickshank 1978) listed Gordonia as a distinct genus, King
(1988) also considered it synonymous with Dicynodon, and fur-
thermore synonymized all of its species, leaving D. traquairi as
the only valid taxon. e most recent revision came as part of
the comprehensive reassessment of the taxonomy of Dicynodon
by Kammerer et al. (2011), who found that D. traquairi and
D. lacerticeps Owen, 1845 (the type species of Dicynodon) did
not form a monophyletic group. As a result, this revision resur-
rected Gordonia, but maintained synonymy of the four Cuies
Hillock species. Kammerer et al. (2011) considered G. traquairi
to be a valid species based on the combination of the following
characteristics: an anterodorsally angled, rod-like lateral dentary
shelf (autapomorphy); long and narrow intertemporal bar with
narrow exposure of parietals; vertical orientation of the post-
orbitals in the intertemporal bar forming sagial crest; short
snout; and short and steep mandibular symphysis.
Amalitzky (1922) described two additional species of
Gordonia from Russia: G. annae and G. rossica. Referral to
Gordonia was based mainly on the large temporal fenestrae of
these specimens, similar to those of the Elgin Gordonia skulls,
but this morphology is widely present in bidentalian dicyno-
donts. Both species are currently considered synonyms of the
Russian endemic dicynodontoid Vivaxosaurus trautscholdi
Amalitzky, 1922, as they share an autapomorphic narrow,
anteroventrally directed caniniform process with a lobe anterior
to the caniniform (Kammerer et al. 2011).
e phylogenetic analysis of Kammerer et al. (2011) re-
covered G. traquairi as a basal dicynodontoid. Relationships
within Dicynodontoidea are unstable [see discussion in
Angielczyk and Kammerer (2017)], and the exact position of G.
traquairi has been mutable in updated versions of this phylogen-
etic analysis run by other authors (e.g. Angielczyk et al. 2021, Liu
2021, Macungo et al. 2022, Shi and Liu 2023). Although a var-
iety of factors, including rampant homoplasy, underlie instability
in this part of the tree, for G. traquairi, part of the problem is
the large number of unknown character states for this taxon
[119/213 characters, representing 55.87% of characters coded
in the recently published phylogenetic analysis by Macungo et al.
(2022)]. Notably, currently missing character information for G.
traquairi includes many features of the palate and endocranium,
which have been shown to be to be phylogenetically important
(Surkov and Benton 2004).
An additional specimen currently aributed to G. traquairi
was discovered by quarrymen in 1997 in the Hopeman
Sandstone Formation, at the Clashach quarry north of Elgin
(Clark 1999, Hopkins and Clark 2000) (Fig. 1B). Initially iden-
tied as an unusual mould, local expert Carol Hopkins recog-
nized its importance as the remains of an extinct animal. Aer
extraction, the block was delivered to the Hunterian Museum
of the University of Glasgow to be studied with non-destructive
imaging techniques (Clark 1999). Clark et al. (2004) described
these methods and nicknamed this fossil ‘e Elgin Marvel’
(Fig. 1C). CT scanning and magnetic resonance imaging (MRI)
were used to generate digital models of the fossil using a Philips
Easivision workstation, revealing that the fossil was of a skull of
a dicynodont. A stereolithograph was then created through the
rapid prototyping process outlined by Birch (1993) to create
a 3D replica (catalogued as GLAHM 114914) of the fossil
skull (Fig. 1D). Later, Cruickshank et al. (2005) described this
specimen and aributed it to the taxon Dicynodon traquairi,
supporting equivalency between the Hopeman Sandstone
Formation and the Cuies Hillock Formation based on tetrapod
fauna. Cruickshank et al. (2005) used the new digital data to
describe aspects of the anatomy previously unavailable for the
taxon, such as the palatal exposure of the palatines and the an-
terior border of the interpterygoid vacuity joining the vomerine
crest [see table 2 in Cruickshank et al. (2005) for more]. While
the new data gathered from this research have been important
for building our knowledge of the anatomy and relationships of
G. traquairi (e.g. Kammerer et al. 2011), computerized imaging
of fossils was at the time somewhat rudimentary. e subse-
quent two decades have witnessed a huge increase in the cap-
acity and power of computed tomography, w ith associated major
advances in understanding the morphology of fossils.
Dicynodont research has greatly beneed from the recent
advancements in computed tomography and related techniques.
Multiple studies have used these technologies to improve our
understanding of dicynodont cranial anatomy and internal
neuroanatomy (Castanhinha et al. 2013, Laaß 2014, 2015, Laaß
and Kaestner 2017, Araújo et al. 2018, 2022, Benoit et al. 2018,
Angielczyk et al. 2019, Simão-Oliveira et al. 2019, Macungo et
al. 2022, 2023). Despite this growing interest in studying di-
cynodonts with CT data, there are still unexplored avenues of
research. Most relevant to this study is the paucity of CT data
available to study the endocranial anatomy of bidentalian di-
cynodonts (Clark et al. 2004, Benoit et al. 2018). is work aims
to address this bias using Gordonia, a relatively small bidentalian
(basal skull length <20cm). e µCT data presented herein re-
veals never-before-seen aspects of the external and internal
cranial anatomy of this taxon and provides the rst digitally re-
constructed brain endocast of a bidentalian.
Additionally, this work contributes to the growing number of
modern studies on the ‘Elgin Reptiles’. Research on the Triassic
reptiles Erpetosuchus granti Newton, 1894 and Scleromochlus
taylori Woodward, 1907 using µCT data has substantially
changed our understanding of the anatomy and phylogenetic
anities of both these taxa, highlighting the importance of re-
visiting historic taxa using modern techniques (Benton and
Walker 2011, Foa et al. 2020, 2022). Moreover, Fle et al.
2024 have recently investigated the taphonomy of tetrapod
tracks in the Hopeman Sandstone Formation and the Cuies
Hillock Formation. Herein, we provide the rst study of one of
the Permian representatives of the Elgin tetrapod assemblage
using µCT data.
MATERIALS AND METHODS
Specimens examined
e focus of this study is ELGNM 1999.5.1 (‘e Elgin
Marvel’), a block of reddish aeolian sandstone containing a
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4 • George et al.
natural mould of a cranium and mandible from the Hopeman
Sandstone Formation (Fig. 1C). e specimen was collected
from the west face of the Clashach quarry at Hopeman near
Elgin, Moray, Scotland (Cruickshank et al. 2005) (Fig. 1A, B).
e Hopeman Sandstone Formation has been interpreted to
have been deposited under aeolian conditions as part of either a
large transverse dune system or star and crescent dunes (Glennie
and Buller 1983, Clemmensen 1987, Glennie 2002). A typical
outcrop of the Hopeman Sandstone in the Clashach quarry also
contains several pebbly layers and rippled surfaces, indicative of
ash-ood deposits (Williams 1973). ELGNM 1999.5.1 was
found at the extreme top of the quarry, within a larger block of
sandstone that had no internal bedding structures. e interface
between the sandstone matrix and the mould within is heavily
stained with dark brown material, which is probably a mixture
of numerous metals, including iron and cobalt (Newton 1893,
Cruickshank et al. 2005). ELGNM 1999.5.1 is associated with
another block, ELGNM 1999.5.2, which contains some of the
right squamosal, the right quadrate, the right quadratojugal, and
a minor part of the postorbital bar of this dicynodont specimen
(Cruickshank et al. 2005). is second block was not scanned
for this study, which focuses only on the ELGNM 1999.5.1
block containing the bulk of the cranium and a complete man-
dible. ELGNM 1999.5.1 is also associated with a fossil mould of
a humerus (ELGNM 1999.22) (Cruickshank et al. 2005).
e digital model of ELGNM 1999.5.1 was compared with other
specimens of G. traquairi and other dicynodontoids examined by
the authors (see Supporting Information, Table S1; Figs S1–S28).
Institutional abbreviations
AM, Albany Museum, Makhanda, South Africa; AMNH,
American Museum of Natural History, New York, USA;
BGS, British Geological Survey, Keyworth, England,
UK; BP, Evolutionary Studies Institute, University of the
Witwatersrand, Johannesburg, South Africa; ELGNM,
Elgin Museum, Elgin, Scotland, UK; GLAHM, Hunterian
Museum, University of Glasgow, Glasgow, Scotland, UK;
GPIT, Paläontologische Sammlung, Eberhard Karls Universität
Tübingen, Germany; IVPP, Institute for Vertebrate Paleontology
and Paleoanthropology, Beijing, China; MB.R, Museum für
Naturkunde Berlin, Germany; MVP, Museu Vicente Palloti, Santa
Maria, Brazil; NHMUK, e Natural History Museum, London,
England, UK; NMQR, National Museum, Bloemfontein, South
Africa; PIN, Paleontological Institute of the Russian Academy of
Sciences, Moscow, Russia; PPN, Projecto PalNiassa Collection,
Museum Nacional de Geologia, Maputo, Mozambique; SAM,
Iziko South African Museum, Cape Town, South Africa; TMM,
Texas Science & Natural History Museum, Austin, USA; UCMP,
University of California Museum of Paleontology, Berkeley,
USA; UFRGS, Universidade Federal do Rio Grande do Sul,
Porto Alegre, Brazil; UMZC, University Museum of Zoology,
Cambridge, England, UK; UNIPAMPA, Universidade Federal
do Pampa, São Gabriel, Brazil; ZPAL, Institute of Paleobiology
of the Polish Academy of Sciences, Warsaw, Poland.
Micro-computed tomography scanning and processing
ELGNM 1999.5.1 was µCT scanned using a Nikon XT H 225
µCT scanner by Dr Elizabeth Martin-Silverstone with the aid
of DF at the University of Bristol Palaeobiology Laboratories
in August of 2021. e scanning generated 1999 CT slices with
an isometric resolution (voxel size) of 0.126 mm. e µCT
dataset was processed using the MATERIALISE MIMICS
INNOVATION SUITE 24 (hps://www.materialise.com/
en/healthcare/mimics-innovation-suite/mimics). e surface
data (STL les containing the digital 3D models) are available
in the Supporting Information (Files S2-S6). e µCT dataset
and associated surface data are freely available at hps://
www.morphosource.org/projects/000586798?locale=en. A
stereolithograph of a humerus associated w ith ELGNM 1999.5.1
[GLAHM 114108 (see Supporting Information, Fig. S29); cast
of the mouldic fossil ELGNM 1999.22) was also used in this
study for body mass calculations (Cruickshank et al. 2005).
ere are important limitations to the data that must be con-
sidered: (i) the mouldic nature of the fossil generally does not
permit sutures to be discerned between bones, which prevents
precise identication of the morphology of many skeletal elem-
ents; (ii) the surface texture of the original bone, which is also
phylogenetically important and provides insight into palaeo-
biology, cannot be visualized in this mouldic fossil (though it
may be visible in other mouldic specimens from the Elgin area,
such as for Elginia mirabilis); and (iii) the large size of the block,
which approaches the maximum size and weight capacity of
the µCT scanner, aected the resolution and clarity of the µCT
scan by aenuating and scaering the X-ray beam [an issue also
encountered by Clark et al. (2004) to a substantially greater ex-
tent]. Due to this issue, several anatomical details observed (or
not observed) in the model should be cautiously interpreted.
Out of caution, any uncertain feature was le as a ‘?’ in the phylo-
genetic dataset.
Phylogenetic analysis
Previously, data used for Gordonia in phylogenetic analyses were
gathered from physical casts created through destructive tech-
niques and the low-resolution digital models made by Clark
et al. (2004). e objectives of our phylogenetic analysis were
to test the referral of ELGNM 1999.5.1 to Gordonia traquairi,
and to test the impact of our new data on the relationships be-
tween G. traquairi and other species. We ran a phylogenetic ana-
lysis with two operational taxonomic units (OTUs): ‘Gordonia
traquairi’ [scores based only on the holotype (coded using the
cast NHMUK PV R 2106)] and ‘e Elgin Marvel’ (scores
based only on ELGNM 1999.5.1). e data matrix and char-
acter list used are those provided by Macungo et al. (2022), with
data for Kunpania scopulusa Sun, 1978 based on Angielczyk et al.
(2021) and data for Jimusaria sinkianensis Yuan and Young, 1934
and Jimusaria monanensis Shi and Liu, 2023 based on Shi and Liu
(2023). e dataset includes 23 continuous characters, 190 dis-
crete characters, and 122 operational taxonomic units (OTUs).
e character list and dierences between the scores of each of the
two Gordonia OTUs are available in the Supporting Information
(File 7). e TNT script and data matrix for the phylogenetic
analysis are included in the Supporting Information (File).
e updated data matrix was used to conduct a ma ximum par-
simony analysis in TNT v.1.5 (Golobo et al. 2008). We rst ana-
lysed it with a new technology search using the sectorial search,
ratchet, dri, and tree fusing tools with default seings. en,
we subjected the shortest trees to an additional round of tree‐bi-
section‐and‐reconnection (TBR) branch swapping (traditional
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Any update • 5
search), to more broadly sample tree space. Jackknife resampling
(with removal probability of 36) and Bremer supports were used
to determine clade support. e ‘list’ and ‘map common synapo-
morphies’ functions were used to identify synapomorphies of
relevant clades.
Calculation of the body mass and encephalization
quotient of Gordonia
Encephalization quotient (EQ), a measure of brain size relative
to body mass, is commonly used as a rough estimate of intelli-
gence of extinct taxa ( Jerison 1973, Evans et al. 2009, Bertrand
et al. 2022). Castanhinha et al. (2013), Laaß (2015), Laaß and
Kaestner (2017), and Simão-Oliveira et al. (2019) previously
listed EQ values for the dicynodonts Niassodon mfumukasi
Castanhinha et al., 2013, Pristerodon mackayi Huxley, 1868,
Kawingasaurus fossilis Cox, 1972, and Rastodon procurvidens Boos
et al., 2016 gathered using digital data, and for Lystrosaurus Cope
1870 gathered using traditional methods. Additionally, Simão-
Oliveira et al. (2019) listed EQ values for many other synapsids.
Here, we calculate the EQ of Gordonia to make comparisons
with all these synapsids.
For simplicity, the EQ and body mass of ELGNM 1999.5.1
will also be referred to as the EQ and body mass of G. traquairi,
as these are the only values available for this taxon. To calculate
the EQ, the endocranial volume was digitally measured using
Mimics from the mask of the endocast. Most of the endocast
was reconstructed, but the olfactory bulbs and most of the olfac-
tory tract could not be reconstructed. e measured endocranial
volume probably represents a slight underestimate, because of
incompleteness (see above), taphonomic distortion, and the ab-
sence of some ossied boundaries of the braincase (e.g. ventral
oor and anterior boundary).
A variety of equations have been used to calculate dicyno-
dont body mass. We performed calculations using a total of
six equations listed by Simão-Oliveira et al. (2019) and Laaß
and Kaestner (2017), which rely on skull length and hu-
merus measurements. We opted to use multiple equations,
as it is currently unclear which of the equations most accur-
ately predicts dicynodont body mass values in the absence
of complete skeletons [see Romano and Manucci (2019) for
discussion of the pitfalls in applying standard regression for-
mulae to calculations of dicynodont body mass]. Skull meas-
urements were taken using Mimics tools on our new digital
model and manually checked on a 1 : 1 scaled 3D print of the
data from Clark et al. (2004). The humerus measurements
were taken from a 1 : 1 scaled 3D print of the humerus mould
[GLAHM 114108, preserved in two parts (anterior and pos-
terior sides) that are a perfect fit] associated with ELGNM
1999.5.1, which is not distorted in any way that would nega-
tively impact the measurements. A photograph of GLAHM
114108 and a full list of the six equations and the reasoning
behind why each is used are available in the Supporting
Information (Fig. S29 in File 1 for the photograph, and File
9 for the equations). The average of the estimates (with one
exclusion) was used as a body mass value in the EQ calcula-
tions. We excluded the value calculated through Equation 4,
because it is far greater than any other calculated value (about
3.8 times larger than the next greatest estimate) and likely
represents an overestimation.
Jerison (1973) performed a regression analysis using data
from a wide range of extant mammals (the closest living rela-
tives of dicynodonts) to nd a correlation between body mass
and brain size. Later, Manger (2006) built upon this work by
performing a regression analysis with an updated version of the
dataset of extant mammals that includes more taxa, but also ex-
cludes cetaceans and primates since they have remarkably large
brains for their body size. We calculated the EQ of Gordonia
using the following equation expressing the regression found by
Manger (2006):
EQ
=
EV ÷0.0535 ×BM0.7294
e EQ values of Gordonia with and without the pineal body
were calculated due to the majority of the pineal body observ-
able in the endocast probably being glandular tissue instead of
neural tissue; the pineal body occupies 9.87% of the endocast
volume (see Results). ese values were compared with those
of other taxa, which were retrieved from Simão-Oliveira et al.
(2019). A table including the Manger values and error margins
for each taxon used in this study can be found in the Supporting
Information (File 10).
RESULTS
Systematic palaeontology
Synapsida Osborn, 1903
erapsida Broom, 1905
Anomodontia Owen, 1860
Dicynodontia Owen, 1859
Dicynodontoidea Olson, 1944
Gordonia Newton, 1893
Diagnosis: As for the type species.
Type species: Gordonia traquairi Newton, 1893
Gordonia traquairi Newton 1893:436.
Gordonia huxleyana Newton 1893:445.
Gordonia duana Newton 1893:450.
Gordonia juddiana Newton 1893:462.
Dicynodon traquairi von Huene 1940:280.
Dicynodon duanus von Huene 1940:280.
Dicynodon huxleyanus von Huene 1940:280.
Dicynodon juddianus von Huene 1940:280.
Type locality: Cuies Hillock Quarry, Elgin, Scotland.
Horizon: Cuies Hillock Formation [probable equivalent of the
Changhsingian Daptocephalus Assemblage Zone of South Africa
(Rubidge 1995, Vigliei et al. 2016)].
Holotype: BGS GSE 4805 [incorrectly listed as BGS GSE 11703
by King (1988) and subsequent sources: Benton and Spencer
1995, Cruickshank et al. 2005, Szczygielski and Sulej 2023;
Kammerer et al. 2011].
Referred material: From the type locality: BGS GSE 11703, BGS
GSE 11704 (holotype of G. huxleyana), ELGNM 1890.3 (holo-
type of G. juddiana), ELGNM 1978.550 [specimen labelled
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6 • George et al.
‘Gordonia Traquairi?’ by Newton (1893); previously incor-
rectly reported as a specimen of the pareisaur Elginia mirabilis
by Benton and Spencer (1995) and Cruickshank et al. (2005)],
ELGNM 1978.559.1a,b (holotype of G. duana); from the
Hopeman Sandstone Formation deposits of the Clashach
quarry, Hopeman, Elgin, Morayshire (National Grid Reference
NJ 163702): ELGNM 1999.5.1, ELGNM 1999.5.2, ELGNM
1999.22.
Emended diagnosis: A small (basal skull length approximately
16 cm) dicynodontoid characterized by the following combin-
ation of character states (+ indicates an autapomorphy, * indi-
cates a newly recognized diagnostic character state based on
µCT data described herein): + an anterodorsally angled lateral
dentary shelf with a rod-like morphology (dorsal and lateral
extensions of the shelf are roughly equal in size) that does not
expand into a rounded anterior boss nor a diuse muscle scar,
does not have a transverse ridge on its dorsal surface, and does
not have a fossa present near its posterior end; long, narrow
intertemporal bar with narrow exposure of parietals; vertical
orientation of the postorbitals in the intertemporal bar forming
sagial crest; short snout (with anteroposteriorly short premax-
illary region); proportionally large orbits*; dorsoventrally thin
suborbital zygoma*; hooked snout tip*; narrow snout in palatal
view, probably resulting from mediolaterally narrow maxilla and
premaxilla*; median pterygoid plate anteroposteriorly elongate
and mediolaterally narrow in palatal view*; anterior pterygoid
close to sagial plane*, and short, steep mandibular symphysis.
Description
e new 3D reconstructions of the cranium and mandible of
ELGNM 1999.5.1 (Fig. 2) generally accord with those made
by Clark et al. (2004). However, we were able to more com-
pletely reconstruct the palate of this specimen, as well as for
the rst time provide information on its endocranial anatomy.
roughout the following description, comparisons are made to
casts of the other G. traquairi specimens (e.g. NHMUK PV R
2106), listed in the Supporting Information, Table S1 with ac-
companying photographs.
Cranium As in all dicynodonts, the premaxilla of ELGNM
1999.5.1 forms the beak at the anterior end of the cranium,
which would probably have been covered in a rhamphotheca
in life (Jasinoski and Chinsamy-Turan 2012, Benoit et al. 2018)
(Fig. 3). e premaxillary region (the bone anterior to the ex-
ternal nares) is anteroposteriorly short in lateral view. e snout
of ELGNM 1999.5.1 is neither deected nor dorsoventrally
elongate, unlike that of Lystrosaurus. In lateral view (Fig. 3A), the
premaxilla has a prominent ‘hooked’ tip, as can also be observed
in NHMUK PV R 2106 (G. traquairi holotype). is condition
in these Gordonia specimens approaches that of Dinanomodon
gilli Broom, 1932, a taxon in which the hooked premaxillary trip
is particularly exaggerated (Kammerer et al. 2011). is morph-
ology cannot be observed in other G. traquairi specimens, and
it is unclear whether this is reective of biological or tapho-
nomic variation. e external nares of ELGNM 1999.5.1 are
anteroposteriorly longer than they are dorsoventrally tall (Fig.
3A, C), which is also the case in ELGNM 1893.6 ("G. juddiana").
NHMUK PV R 2106 (G. traquairi holotype) and NHMUK PV
R 2109 ("G. huxleyana") instead have external nares that are
dorsoventrally taller than they are anteroposteriorly long.
Most of the palate of ELGNM 1999.5.1 can be visualized, pro-
viding substantially more information on this part of the skull
than in any other known Gordonia specimen (Fig. 4). e anterior
tip of the snout is rounded in ventral view. e anterior palatal
ridges of the secondary palate can tentatively be identied as pro-
portionally small compared to most other dicynodontoids, but
appear to be present, unlike in Kunpania scopulusa (Angielczyk
et al. 2021). It is unclear whether the proportionally small size
of the anterior palatal ridges is a true biological character or a re-
sult of taphonomic factors. A median palatal ridge can be iden-
tied along the posterior end of the palatal surface of ELGNM
1999.5.1 (Fig. 4) and is conuent with the vomer. ere are no
longitudinal depressions along the secondary palate (Fig. 4).
e lateral surfaces of the caniniform processes of ELGNM
1999.5.1 are convex laterally and do not have any clear depres-
sions or protrusions (Fig. 3). ey are interpreted as being
formed by the maxillae, as is the case in all other dicynodonts.
e caniniform processes of NHMUK PV R 2106 (G. traquairi
holotype), NHMUK PV R 2109 ("G. huxleyana"), and ELGNM
1893.6 ("G. juddiana") also have this morphology. Unlike the
maxillae of closely related taxa, this region in ELGNM 1999.5.1
seems to be proportionally mediolaterally narrow (Kammerer
et al. 2011). A similar morphology is observed in Jimusaria
sinkianensis, but in most other dicynodontoids this region is
widened, with a greater degree of ‘splay’ of the caniniforms
(Kammerer et al. 2011). As in most dicynodontoids, the only
dentition present in G. traquairi is the caniniforms, which erupt
from the maxillae (Kammerer et al. 2011). e caniniforms of
ELGNM 1999.5.1 are directed ventrally, like those of the other G.
traquairi specimens in which they are preserved [NHMUK PV
R 2106 (G. traquairi holotype), ELGNM 1893.6 ("G. juddiana"),
NHMUK PV R 2109 ("G. huxleyana"), and NHMUK PV R
2107 (referred to G. traquairi)].
A nasal boss is present in ELGNM 1999.5.1, and is best seen
in lateral view (Fig. 3A, C). It is a single, slightly raised expan-
sion of the nasals, which is continuous between both bones,
like that of other Permian dicynodontoids. A boss is also pre-
sent in NHMUK PV R 2106 (G. traquairi holotype). A nasal
boss cannot be clearly identied in NHMUK PV R 2109 ("G.
huxleyana"), ELGNM 1893.6 ("G. juddiana"), or NHMUK PV
R 2107 (referred to G. traquairi), but this more likely represents
taphonomic artefact than biological variation.
ere is a slight circumorbital rim extending across the or-
bital margins of what is probably the prefrontal through the
postorbital in ELGNM 1999.5.1 (Kammerer et al. 2011) (Fig.
3D, E). A similar circumorbital rim is present in NHMUK PV
R 2106 (G. traquairi holotype) but is not as well developed
in other specimens. A weakly-developed rim is visible at the
anterodorsal corner of the orbit (probably corresponding to the
prefrontal margin) of NHMUK PV R 2109 ("G. huxleyana") and
ELGNM 1893.6 ("G. juddiana"), but it does not appear to con-
tinue posteriorly. Kammerer et al. (2011) noted that G. traquairi
has relatively large orbits compared to other dicynodonts, and
this is supported by the new data presented herein (Fig. 3).
In dorsal view, the postorbitals converge posterior to the
pineal foramen, which is located near the anterior end of the
intertemporal bar (Fig. 3D–F). An interorbital depression can
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Any update • 7
be identied anterior to the pineal foramen, which probably cor-
responds to the region occupied by the preparietal. e pineal
foramen is anteroposteriorly longer than it is mediolaterally
wide and it is similar in shape to that of ELGNM 1893.6 ("G.
juddiana"). NHMUK PV R 2109 ("G. huxleyana") also has a
preserved pineal foramen, but it is proportionally larger than
AB
C
EF
D
Figure 2. Skull of ELGNM 1999.5.1 in anterior (A), posterior (B), le lateral (A), right lateral (B), dorsal (E), and ventral (F) views. Scale
bars = 4 cm.
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8 • George et al.
that of ELGNM 1999.5.1. e pineal foramen of "G. duana"
(ELGNM 1978.559.1) is less elongated than that of ELGNM
1999.5.1 and shows greater exposure in the intertemporal bar,
not being overlapped by the postorbitals (Newton 1893). e
adductor fossa of the right postorbital of ELGNM 1999.5.1 is
medial to the posterior margin of the right orbit. Much of the
postorbitals are dorsal to the rest of the skull roof as they form
the lateral surfaces of the sagial crest (Fig. 5). As noted by
Kammerer et al. (2011), the sagial crest of NHMUK PV R
2106 (G. traquairi holotype) is proportionally large (unusually
so for a dicynodont of its size), mediolaterally narrow (providing
only slight dorsal exposure of the parietals), and formed by verti-
cally oriented postorbitals, and this mostly matches what is seen
in the new data presented herein. e intertemporal portion of
the postorbitals shows more horizontal orientation in ELGNM
1999.5.1 than in the holotype, particularly anteriorly, although
the postorbital surface is near-vertical at the apex of the crest. In
dorsal view, the crest can be seen to be thinnest at its mediodorsal
edge and expands in length lateroventrally (Fig. 5). e crest is
also laterally thicker anteriorly than posteriorly. In lateral view,
the sagial crest increases in height posteriorly from the pineal
foramen, before decreasing in height at the posterior end of the
Figure 3. Anterior half of the cranium of ELGNM 1999.5.1 in le lateral (A), anterior (B), right lateral (C), and the anterior half of the cranium
with focus on other anatomical elements in anterior (D), tilted anterodorsal (E), and dorsal view (F). Abbreviations: afp, adductor fossa of
postorbital; ap, anterior plate of the orbitosphenoid–mesethmoid; cr, circumorbital rim; fr, frontal; ju, jugal; la, lacrimal; mx, maxilla; na, nasal;
nare, external nare; nb, nasal boss; or, orbit; pf, pineal foramen; pm, premaxilla; po, postorbital; prf, prefrontal; pt, pterygoid; sc, sagial crest;
t, tusk. Scale bars = 1 cm.
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Any update • 9
skull. Similar to ELGNM 1999.5.1, the crest of NHMUK PV R
2106 (G. traquairi holotype) gradually increases in dorsoven-
tral height posteriorly from the anterior origin of the crest and
maintains a similar height for the majority of the crest until it de-
creases in height at its posterior end. e crest of NHMUK PV R
2109 ("G. huxleyana") is not as tall as that of ELGNM 1999.5.1
and NHMUK PV R 2106 (G. traquairi holotype) but has similar
changes in dorsoventral height throughout the crest to those of
the other two specimens. e crests of NHMUK PV R 2107 (re-
ferred to G. traquairi) and ELGNM 1893.6 ("G. juddiana") are
considerably less tall than those of the previously mentioned G.
traquairi specimens and are instead the same height as the rest
of the dorsal surface of the skull roof. Such variation in crest
shape between specimens, where smaller, skeletally immature
ar?
pm
mx
pr
vo
lp
in
iv
ju
aptr
qptr
qd
qd
aptr
mpp
mpp
ic ic
ps bs
bt bt
co co
t
AB
Figure 4. Palatal (A) and tilted palatal (B) view of ELGNM 1999.5.1. Abbreviations: aptr, anterior ramus of pterygoid; ar, anterior ridges of
premaxilla; bs, basisphenoid; bt; basal tuber; co, crista oesophagea; ic, opening for internal carotid artery; in, internal nare; iv, interpterygoid
vacuity; ju, jugal; lp, lateral palatal fenestra; mpp, medial plate of pterygoid mx, maxilla; pm, premaxilla; pr, posterior median ridge of
premaxilla; ps; parasphenoid; qd, quadrate; qptr, quadrate ramus of pterygoid; t, tusk; vo, vomer. Scale bars = 1 cm.
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10 • George et al.
specimens have smaller crests, lines up with known trends in
therapsid ontogeny (Jasinoski et al 2015, Kammerer et al. 2015,
Jasinoski and Abdala 2016). is suggests a biological reason be-
hind the variation between specimens that is related to muscle
area. e postorbitals of ELGNM 1999.5.1 articulate with the
parietals medially, which extend ventrally beyond the crest. e
mediolaterally thin crest indicates that the dorsal exposure of the
parietals was narrow.
Unlike for most of the specimen, there is a clearly identiable
suture between the le jugal and the zygomatic arch of the le
squamosal (Fig. 6A). e jugal–squamosal suture forms a di-
agonal line immediately posterior to the le orbit in le lateral
A
CD
EF
B
sc
sc
sc
po
po
po
pa
fo
fo
Figure 5. Sagial crest of ELGNM 1999.5.1 in le lateral (A), le anterolateral (B), tilted le posterolateral (C), ventral (only le half of crest)
(D), right anterolateral (E), and right posterolateral (F) views. Abbreviations: fo, fossa ventral to intertemporal bar; pa, parietal; po, postorbital;
sc, sagial crest. Scale bars = 1 cm.
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Any update • 11
view, such as is seen in many other Permian dicynodontoids,
e.g. Dicynodon lacerticeps (Kammerer et al. 2011). e other
cranial specimens of G. traquairi also preserve the zygomatic
arch, but precise jugal morphology is dicult to determine. e
suborbital portion of the zygoma is remarkably dorsoventrally
thin in ELGNM 1999.5.1 (Fig. 6), unlike the thicker structures
in many other dicynodontoids [e.g. NHMUK PV OR 47047
(Daptocephalus leoniceps)], but similar to that of Delectosaurus
areevi Kurkin, 2001 (PIN 4644/1) (Kammerer, pers. observ.).
Comparable zygomatic proportions are present in NHMUK
PV R 2106 (G. traquairi holotype), NHMUK PV R 2109 ("G.
huxleyana"), and ELGNM 1893.6 ("G. juddiana"), suggesting
that this is a consistent feature in Gordonia.
Only the le squamosal is completely preserved in ELGNM
1999.5.1 (Fig. 6), while the right is split between this specimen
and ELGNM 1999.5.2 (Clark et al. 2004). In dorsal view, the
width of the le zygomatic arch expands towards its posterior
end. In dorsal view, the posterior end of the squamosal is con-
cave, and the medial portion of the le squamosal articulates
with the bones of the sagial crest. Near the anterior end of
the zygomatic arch, there is an abrupt shi in morphology
of the zygomatic arch as it is dorsoventrally taller than it is
mediolaterally wide anteriorly and then becomes mediolaterally
wide posteriorly for much of its anteroposterior length. is
morphology is not seen in NHMUK PV R 2106 (G. traquairi
holotype), NHMUK PV R 2109 ("G. huxleyana"), NHMUK
PV R 2107 (referred to G. traquairi), and ELGNM 1893.6 ("G.
juddiana"), indicating that this shi in morphology in ELGNM
1999.5.1 represents taphonomic artefact rather than biological
variation. All the G. traquairi specimens with well-preserved
le squamosals have squamosal ventral processes that are ex-
posed posteriorly. In le lateral view, the anteroposterior length
of the quadrate ramus of the squamosal of ELGNM 1999.5.1
is greatest dorsally, and gradually decreases ventrally (Fig. 6A).
e adductor fossa of the le squamosal can be identied in le
lateral and posterior views as the fossa between the quadrate
and zygomatic rami (Fig. 6B).
e le quadrate of ELGNM 1999.5.1 is preserved with lile
distortion. In palatal view, the roughly equal-sized medial and
lateral condyles of the quadrate can be identied with a trochlea
between them, which would have articulated with the mandible
(Fig. 4). e right quadrate contacts the right quadrate ramus
of the pterygoid, but the le quadrate only nearly contacts the
le quadrate ramus of the pterygoid. is asymmetrical dier-
ence is probably a result of inconsistent preservation and not
biological variation, and in life, there would have been contact
on both sides. NHMUK PV R 2106 (G. traquairi holotype) and
ELGNM 1893.6 ("G. juddiana") show comparable quadrate
morphology. Only the le quadratojugal of ELGNM 1999.5.1
can be condently identied. e bone is a thin, broad plate
that is ush with the squamosal. In posterior view, the ventral
process of the squamosal occludes the quadratojugal. Similarly,
NHMUK PV R 2106 (G. traquairi holotype) and NHMUK PV
R 2107 (referred to G. traquairi) also possess le quadratojugals
that are visible in le lateral view, which are continuous with
the squamosals. In NHMUK PV R 2109 ("G. huxleyana") and
ELGNM 1893.6 ("G. juddiana"), the quadratojugals appear
to be missing, exposing the shallow articular fossa where they
would have overlapped the anteroventral face of the squamosal.
e le quadratojugal foramen of ELGNM 1999.5.1 is dorso-
ventrally taller than it is mediolaterally wide (Fig. 6A).
Part of the vomer of ELGNM 1999.5.1 can be identied
as a thin ridge between the internal nares, conuent anteri-
orly with the median palatal ridge of the premaxilla, and has a
ventral margin oset from the rest of the palate (Fig. 4). e
ridge has a consistent mediolateral width throughout (narrow
and blade-like), which is unlike that of other dicynodontoids
such as D. lacerticeps where a large portion of the anterior part
of the vomer ridge is mediolaterally wider than the rest of the
ridge (Kammerer et al. 2011). Posteriorly, the vomer splits at an
acute angle, bounding an isosceles triangular fossa anterior to
the interpterygoid vacuity. Lateral and dorsal to this split, hori-
zontally oriented laminar portions of the ventral surface of the
vomer form part of the primary palate. e dorsal portion of the
vomer was incompletely visible in the CT data; what could be re-
constructed is a tall, blade-like median element partially dividing
the nasal capsule, similar to that known in other dicynodontoids
(e.g. Lystrosaurus; Cluver 1971).
e palatine bones of ELGNM 1999.5.1 border the internal
nares laterally (Fig. 4). e exact morphology of the palatines is
unclear, due to poor resolution at the edges of the internal narial
cavities. e right internal narial opening in particular appears
damaged, with an opening extending much further anterior (be-
yond the caniniform process; Fig. 4A) than in other dicynodonts.
e posterior halves of the internal nares are beer preserved and
are almost parallel to each other, unlike those of D. lacerticeps,
which show greater transverse expansion posteriorly (Kammerer
et al. 2011). e right palatine of ELGNM 1999.5.1 has a dorsal
projection (Fig. 7A, B), which is angled anterolaterally and has
a concave medial face. is portion of the palatine appears to
bound part of the labial fossa. It is similar in morphology to that
of other dicynodontoids, but is mediolaterally wider and more
strongly dorsally angled than that of earlier diverging taxa, such
as Niassodon mfumukasi (Castanhinha et al. 2013).
Much of the following anatomy of the pterygoid of ELGNM
1999.5.1 described herein helps distinguish G. traquairi from
other taxa and cannot be seen in the reconstructions made by
Clark et al. (2004).
In palatal view, the pter ygoid of ELGNM 1999.5.1 is X-shaped
with two anterior rami diverging slightly anterolaterally and two
quadrate rami diverging more widely posterolaterally from the
medial plate (Fig. 4). e anterior rami of ELGNM 1999.5.1
diverge much less laterally than those of other taxa, such as
Dicynodon spp. (Kammerer et al. 2011, Kammerer 2019).
is morphology contributes to the relatively narrow palate of
ELGNM 1999.5.1 compared to other Permian dicynodontoids
(see above) (Kammerer et al. 2011, Kammerer 2019, Liu 2021),
and is instead more similar to some non-dicynodontoid di-
cynodont taxa such as Compsodon helmoedi van Hoepen, 1934
(Angielczyk and Kammerer 2017). ere are keels on the an-
terior rami of ELGNM 1999.5.1, which are best visible in le
lateral view (Fig. 7A). Similar keels are present throughout
Dicynodontoidea, other than in kannemeyeriiforms (Kammerer
et al. 2011). e keels of ELGNM 1999.5.1 gradually increase in
dorsoventral height towards their anterior ends. In palatal view,
there is a distinct indentation anterior to the le anterior ramus
of the pterygoid, which is best interpreted as the lateral palatal
fenestra based on its position and its somewhat teardrop-shaped
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12 • George et al.
zsq
zsq
tf
tf
po
qsq
vsq
vsq
afs
sjs
ju
qptr
qd
qd
qj
ju
A
CD
B
Figure 6. Le squamosal and associated elements of ELGNM 1999.5.1 in le lateral (A), dorsal (B), ventral (C), and posterior (D) views.
Abbreviations: afs, adductor fossa of squamosal; ju, jugal; qd, quadrate; qj, quadratojugal; qptr, quadrate ramus of pterygoid; qsq, quadrate
ramus of squamosal; sjs, suture between jugal and squamosal; tf, temporal fenestra; vsq, ventral process of squamosal; zsq, zygomatic process
of squamosal. Scale bars = 1 cm.
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Any update • 13
outline (Fig. 4B). e palatal fenestrae of other dicynodontoids,
such as D. lacerticeps, have a similar shape (Kammerer et al.
2011). e interpterygoid vacuity can be identied anterior to
the median pterygoid plate and is also roughly teardrop-shaped,
but anteroposteriorly elongate (Fig. 4A). A labial fossa appears
to be present lateral to the le anterior pterygoid ramus (Fig.
7B). e elements bounding this fossa cannot be determined;
by comparison to other dicynodontoids they probably consist of
the maxilla, jugal, and palatine (Kammerer et al. 2011). It is un-
likely that the pterygoid ramus directly contacts the fossa.
A
B
CD
EF
qptr
qptr
pk
aptr
pl
mx
pm
pl
vo
hpl
hpl
fr
ofc
mpw
mpw
pm
mx
lf
pt
Figure 7. Internal cranial bones of ELGNM 1999.5.1 in le lateral (A) and le anterolateral (B) views, and the anterior plate of the
mesethmoid–orbitosphenoid of ELGNM 1999.5.1 in right lateral (C), le lateral (D), posterior (E), and anterior (F) views. Abbreviations:
aptr; anterior ramus of pterygoid; fr, frontal; hpl, horizontal plate; lf; labial fossa; mpw, mesethmoid posterior wall; mx, maxilla; ofc, olfactory
cavity; pk; pterygoid keel; pl; palatine; pm, premaxilla; pt; pterygoid; qptr, quadrate ramus of pterygoid; vo, vomer. Scale bar in A-B = 4 cm,
and in C-F = 1 cm.
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14 • George et al.
e medial pterygoid plate of ELGNM 1999.5.1 is substan-
tially anteroposteriorly longer than it is mediolaterally wide
(Fig. 4). e median plate is proportionally anteroposteriorly
longer and mediolaterally narrower than in most other Permian
dicynodontoids, such as NHMUK PV OR 47047 (Daptocephalus
leoniceps), NHMUK PV R 4039 (V. trautscholdi), and Dicynodon
spp. and Turfanodon spp. (Kammerer et al. 2011, Kammerer
2019, Liu 2021) (Fig. 4), but is comparable to that of Jimusaria
spp. (see IVPP V341407 in: Kammerer et al. 2011, Shi and Liu
2023). ere are keels on the lateral sides of the medial plate that
are continuous with the keels of the anterior rami (Fig. 7A). e
crista oesophagea can be identied as a weak ridge posterior to
the interpterygoid vacuity. e crista oesophagea is present in
most dicynodontoids except for Daptocephalus spp. (Kammerer
2019). It should be noted that juvenile specimens of Dicynodon
lacerticeps also lack a crista oesophagea, indicating potential
ontogenetic control on this feature in other taxa (Kammerer
2019).
e quadrate rami of the pterygoid of ELGNM 1999.5.1 di-
verge posterolaterally to articulate with the quadrates (Fig. 4).
Both quadrate rami extend slightly ventrally from the medial
plate (Fig. 7A) like those of NHMUK PV R 2106 (G. traquairi
holotype), but unlike ELGNM 1893.6 ("G. juddiana") and
NHMUK PV R 2109 ("G. huxleyana") in which the quadrate
rami extend ventrally at a steeper angle, possibly due to distor-
tion. e ventral sides of the quadrate rami are continuous with
the keels on the lateral sides of the medial plate. In lateral views,
the height of the quadrate rami is comparable to that of the lat-
eral sides of the medial plate.
e parasphenoid of ELGNM 1999.5.1 is a thin, elongate
element ush with other internal cranial bones (Fig. 8A, B) and
probably fused with the basisphenoid, as in other dicynodonts
(Macungo et al. 2022). A small, median ridge on the dorsal sur-
face of the parasphenoid can be tentatively identied as part of
the base of the cultriform process. A parasphenoidal sulcus is
present on the dorsal surface as a shallow depression anterior
to the endocranial cavity. In palatal view, a single foramen for
the internal carotid artery is visible, presumably borne on the
basisphenoid (Fig. 4). It is slightly oset from the sagial plane,
indicative of it being one of a pair of foramina (the other not
preserving). It is in a similar position as the same structure in
Lystrosaurus, based on UMZC T758 and UMZC T788 and what
is described by Cluver (1971). For the basisphenoid, two add-
itional notable features can be identied. e rst is a dorsally
projecting tab-like structure that is angled slightly posteriorly,
which is best interpreted as the clinoid process (Fig. 8A). e
second is that the basal tubera (also formed by the basioccipital
posteriorly) are nearly vertical, with no clear ridges along their
long axes (Fig. 4). e tubera form the posterior portion of
the stapedial facet, which is open distally. Most details of the
sphenoid elements (especially those that cannot be identied
in palatal view) could not be observed in the reconstructions by
Clark et al. (2004).
e prootic dorsal processes compose the dorsally extending
portion of the internal cranial bones that articulate with the
occiput (Fig. 9B, C). e pila antotica is visible as a weakly-
developed, anteriorly-directed process at the anteroventral
margin of the prootic (identity of this element as prootic based
on comparison with other synapsids; it is likely that the prootic
is fused with other elements to form a periotic as in other di-
cynodonts; see below). e pila antotica is unusually low,
which probably represents incomplete preservation or visualiza-
tion. e only other specimens of G. traquairi with identiable
prootic regions are NHMUK PV R 2106 (G. traquairi holotype),
NHMUK PV R 2109 ("G. huxleyana"), and NHMUK PV R 2107
(referred to G. traquairi). However, these specimens do not re-
veal much detail concerning these elements, and do not substan-
tially aid in determining pila antotica morphology in Gordonia.
e opisthotics of ELGNM 1999.5.1 are inferred to contribute
to the borders of the vestibules, and their paroccipital processes
are identiable in posterior view as being ush with the rest of
the occiput (Fig. 9A). A similar paroccipital process can also be
identied in posterior view of the occiput of ELGNM 1893.6
("G. juddiana").
e prootics and opisthotics also contain the vestibule (de-
scribed in the description of the endocast and vestibule below).
e opening for the vestibule to meet the endocranial cavity
can be seen in le medial view of the basicranium, and based
on the morphology known for other dicynodont braincases
(Macungo et al. 2022), would have been enclosed by the prootic,
opisthotic, and basioccipital (Fig. 8D). e jugular foramen and
opening for the vestibule can also be seen in le medial view of
the basicranium and have a very similar position to what is seen
throughout dicynodonts (e.g. Lystrosaurus; UMZC T758 and
UMZC T788) (Surkov and Benton 2004). e basioccipital
median ridge is dorsally elevated (Fig. 8A–C). Additionally,
the foramen for the cranial nerve VII (facial nerve), the fenestra
basicranialis, and the foramen ovale can also be identied (Fig.
8D). ese neurocranial elements of ELGNM 1999.5.1 could
not be identied in the models made by Clark et al. (2004), em-
phasizing the value of novel tomographic study of this specimen.
e occiput is presumed to be composed of a periotic,
which is a fusion of several elements (minimally the prootic
and opisthotic, but oen incorporating several additional elem-
ents, e.g. supraoccipital, exoccipitals, and basioccipital), as in
most other dicynodonts (Kammerer et al. 2011, Kammerer
2019). An incompletely preserved occipital condyle (which
would be formed by paired, lateral exoccipital and median, ven-
tral basioccipital elements) is present ventral to the foramen
magnum of ELGNM 1999.5.1 (Fig. 9A). e foramen magnum
is oval-shaped, with its dorsoventral height greater than its
mediolateral width, as in ELGNM 1893.6 (‘G. juddiana’), and
as is common in dicynodonts (Laaß and Kaestner 2017). ere
is no clear occular fossa present on the medial side of the
supraoccipitals, but this may be a result of taphonomic factors.
ere is evidence for an ‘unossied zone’, a feature also seen
throughout non-dicynodontoid dicynodonts (Laaß 2015, Laaß
et al. 2017, Simão-Oliveira et al. 2019). e ‘unossied zone’ is
most visible in the endocast described below.
e laminar portion of the fused mesethmoid and orbito-
sphenoid (anterior plate) of ELGNM 1999.5.1 is ush with the
skull roof (Fig. 7C–F). Additionally, part of the olfactory cavity
can be identied. Most notably, the mesethmoid posterior wall
can be observed. In anterior and posterior views, this wall is
simple and thin, but in lateral views, the wall is a ventrally dir-
ected and dorsoventrally taller than the anteroposteriorly long,
triangular plate pointing anteroventrally. Considering that much
of the ethmoid region and olfactory cavity is not well preserved,
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Any update • 15
this pointed portion of the anterior plate may also not be com-
plete, and it is possible that it formed a more extensive median
structure separating the orbits, as in many other dicynodonts
(King 1988).
Mandible e mandible of ELGNM 1999.5.1 is completely pre-
served and is not taphonomically distorted in any way that ob-
scures much of its anatomical details from being discerned.
e dentaries of ELGNM 1999.5.1 have a typical
dicynodontoid morphology [as is described by Kammerer
(2019)]. Anteriorly, the dentaries fuse and largely con-
tribute to the mandibular symphysis, with a pointed beak at
its anterodorsal tip (Fig. 10). e symphysis is rectangular
(dorsoventrally taller than mediolaterally wide), and dorsoven-
trally shorter than that of other other Permian dicynodontoids,
including Dicynodon angielczyki and Jimusaria monanensis
fbscr
jf ve
VII
fo
ps
ABC
D
pr
bo
bo
bs clp
cup
pss
bmr
bmr
Figure 8. Basicranium of ELGNM 1999.5.1 in anterior (A), dorsal (B), posterodorsal (B), and le sagial (D) views. Abbreviations: bmr,
basioccipital median ridge; bo; basioccipital; bs; basisphenoid; clp, clinoid process; cup, base of cultriform process; scr, fenestra basicranialis;
fo, foramen ovale; jf, jugular foramen; pr, prootic; ps, parasphenoid; pss, parasphenoidal sulcus; ve, vestibule; VII, foramen for cranial nerve
VII. Scale bars = 1 cm.
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16 • George et al.
BC
pa
pr
pia
fm
op
qptr
qd
qd
qf
qj qj
qf
qptr
su
A
sq
su
bo
eo eobg
bt
fm
op
Figure 9. Occiput and associated elements of ELGNM 1999.5.1 in posterior (A), anterior (B), and le anterolateral (C) views. Abbreviations:
bo, basioccipital; bt, basioccipital tubera; eo, exoccipital; eobg, exoccipital bulge; fm, foramen magnum; op, opisthotic; pa, parietal; pia,
pila antotica; pr, prootic; qd, quadrate; qf, quadrato-jugal foramen; qj, quadratojugal; qptr, quadrate ramus of pterygoid; sq, squamosal; su,
supraoccipital. Scale bars in A = 2 cm, and in B and C = 4 cm.
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Any update • 17
(Kammerer 2019, Shi and Liu 2023). e anterior surface of
the symphysis of ELGNM 1999.5.1 is also more steeply angled
than that of D. angielczyki and J. monanensis (Kammerer 2019,
Shi and Liu 2023). Additionally, there are two ridges diverging
ventrolaterally from each other at about the midpoint of the an-
terior surface of the symphysis. ey represent the ventral parts
of the dentaries, and the indented part of the anterior surface of
the symphysis ventral to these ridges represents the splenial. e
dorsal portion of the symphysis is bifurcated into two dorsally
projecting protrusions with a notch between them, which is a
preservational artefact associated with incomplete preservation
or scan resolution (particularly evident in posterior view; Fig.
10D), in which the le side of the dentary tip is missing. A pos-
terior dentary sulcus can be identied on the dorsal surface of
each mandibular ramus immediately posterior to the at dentary
tables, situated posterolateral to the posterior dorsal surface of
the mandibular symphysis. ese sulci are narrow and deep, run
along the dorsal surface of the mandible, and extend approxi-
mately across the anterior third of the rami. e lateral edges of
the symphysis are swollen. Unlike ELGNM 1999.5.1, NHMUK
PV R 2106 (G. traquairi holotype) appears to have a rounded an-
terior face of the mandibular symphysis in lateral view. However,
this is probably artefactual; the dorsal surface of this region in
casts is strongly indented, unlike any other dicynodonts and in-
dicative of incomplete preservation in this region.
In lateral view of ELGNM 1999.5.1, the anterior ends of the
dentaries are dorsoventrally taller than any other part of the
bones (Fig. 10). e lateral dentary shelf of each mandibular
ramus is well exposed in lateral views. e lateral dentary shelves
are angled anterodorsally, have a rod-like morphology (with the
dorsal and lateral extensions of the shelf being roughly equal in
size), and do not expand into a rounded anterior boss nor a dif-
fuse muscle scar (Fig. 10). Instead, the anterior portion of each
dentary shelf is slightly swollen. A similar lateral dentary shelf
can be seen in NHMUK PV R 2106 (G. traquairi holotype). e
combination of these characteristics is unique to G. traquairi
among dicynodonts [as is noted by Kammerer et al. (2011)].
e lateral dentary shelf of Jimusaria monanensis is similar, but
not as strongly angled anterodorsally (Shi and Liu 2023). e
non-dicynodontoid dicynodont Compsodon helmoedi also has an
anterodorsally angled dentary shelf but, unlike in G. traquairi, it
is much more prominent, with a transverse ridge on the dorsal
surface of the dentary shelf and a fossa present near the posterior
end of the dentary shelf in that taxon (Angielczyk et al. 2023).
e lateral dentary shelves largely contribute to the dorsal
margin of the mandibular fenestrae, which are considerably
anteroposteriorly longer than they are dorsoventrally tall (Fig.
10). is mandibular fenestra shape is also present in NHMUK
PV R 2106 (G. traquairi holotype) and NHMUK PV R 2019
("G. huxleyana"). e suture between the dentary and le an-
gular of ELGNM 1999.5.1 cannot be identied, but is probably
represented in NHMUK PV R 2106 (G. traquairi holotype) by a
sinusoidal line running dorsoventrally at the posterior end of the
mandibular fenestra. e sinusoidal line then connects with the
posterior end of the mandibular fenestra.
e reected laminae of the angulars are ventrally directed
projections posterior to the mandibular fenestrae, and each is bi-
sected by a central groove. A similar reected lamina morphology
can be seen in many other Permian dicynodontoids (Kammerer
et al. 2011, Kammerer 2019, Olroyd and Sidor 2022). e pos-
terior ends of the surangulars are slightly laterally ared, and
this characteristic can also be seen in NHMUK PV R 2106 (G.
traquairi holotype) and NHMUK PV R 2109 ("G. huxleyana").
ere is a wide separation between the articulars and the re-
ected lamina, a trait seen throughout Permian dicynodontoids
(Olroyd and Sidor 2022). e medial and lateral condyles of the
articulars can be identied on either side of the median ridge,
which would have articulated with the quadrate. Retroarticular
processes protrude ventrally from the posterior ends of the
articulars.
Endocast and vestibule Most of the endocast and the le vesti-
bule of ELGNM 1999.5.1 were reconstructed (Fig. 11), except
for the olfactory bulbs, most of the olfactory tract, the entirety
of the right vestibule, all semicircular canals, and associated
bony canals enclosing blood vessels and nerves. Generally, the
endocast is not drastically distorted in any way that obscures
identication of much of its anatomy. In the description herein,
the endocast of ELGNM 1999.5.1 is referred to as the endocast
of G. traquairi, being the only endocast of this taxon known in
any detail. As illustrated by Newton (1893: pl. 32, g. 1), part of
the dorsal surface of the brain endocast appears exposed in ‘G.
duana’ (ELGNM 1978.559.1), but this comprises only a small
portion directly underlying the skull roof between the orbits and
pineal foramen.
In the lateral view of the endocast (Fig. 11E), the forebrain can
be identied as a beam-shaped structure showing a ‘keel’ on its
ventral side. is keel is a result of mediolateral compression of
the parietals in this specimen, and is unlikely to have been a fea-
ture of the anterior braincase in the living animal (in which the
oor was probably unossied). e forebrain is anteroposteriorly
longer than it is dorsoventrally tall, and mediolaterally thin in
dorsal view. is morphology can be aributed to a combination
of the legitimately narrow intertemporal region in the skull as well
as taphonomic distortion due to compression. e preserved
portion of the olfactory tract is within the olfactory cavity in the
orbitosphenoid–mesethmoid element. Overall, the elongated
shape of the forebrain of G. traquairi resembles that of various
earlier-diverging dicynodonts, such as Niassodon mfumukasi,
Pristerodon mackayi, Rastodon procurvidens, and Diictodon feliceps
Owen, 1876, as well as the dicynodontoid Lystrosaurus (Edinger
1955, Hopson 1979), rather than the bulbous and proportionally
large forebrains of the cistecephalid emydopoids Kawingasaurus
fossilis and Kembawacela spp. (Castanhinha et al. 2013, Laaß
2015, Laaß and Kaestner 2017, Laaß et al. 2017, Angielczyk et
al. 2019, Simão-Oliveira et al. 2019, Araújo et al. 2022). ere
is no bisected swelling in the forebrain of G. traquairi, again
similar to N. mfumukasi, P. m a c k ayi , R. procurvidens, D. feliceps,
and Lystrosaurus, and unlike K. fossilis and Kembawacela spp.
(Edinger 1955, Castanhinha et al. 2013, Laaß 2015, Laaß and
Kaestner 2017, Laaß et al. 2017, Angielczyk et al. 2019, Simão-
Oliveira et al. 2019, Araújo et al. 2022). e most distinguishing
characteristic of the endocast of G. traquairi is the well-developed
pineal body (Fig. 11E). In lateral view, the pineal body protrudes
anterodorsally within the mediolaterally thin sagial crest, and
has an anteriorly directed projection at its dorsal end, giving it a
triangular shape. e anterior side of the triangular dorsal end is
exposed to the outside of the skull through the pineal foramen
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18 • George et al.
immediately anterior to the sagial crest. is morphology is un-
likely to be a preservational artefact, but instead largely reective
of the true endocast morphology, as the element is entirely en-
closed by preserved skeletal elements that are not drastically
taphonomically altered. e anterior direction of the pineal
body can be aributed to the presence of the tall, narrow sagial
crest; the same structure in Lystrosaurus (where no sagial crest
is present) is a simple, vertical tube (Edinger 1955).
e midbrain forms the ventrally directed portion of the
endocast leading towards the hindbrain at the posterior end of
the endocast (Fig. 11E). e midbrain is strongly dorsoventrally
angled, creating an almost 45º angle between the forebrain and
spl
d
sa
ar
rla
AB
C
F
D
E
dta
d
spl
spl
spl
sa ar
ar
rla
ang
ang
ang rla rla
pra
lds
lds
pds
d
d
spl
mf
Figure 10. Mandible of ELGNM 1999.5.1 in dorsal (A), anterior (B), ventral (C), posterior (D) views, and right mandibular ramus in lateral
(E) and medial (F) views. Abbreviations: ang, angular; ar, articular; d, dentary; dta, dentary table; lds, lateral dentary shelf; mf, mandibular
fenestra; pds, postdentary sulcus; pra, prearticulat; rla, reected lamina of angular; sa, surangular; spl, splenial. Scale bars = 3 cm.
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Any update • 19
ot fb
mb
hb ve
hyp
uz
pb
AB
C
E
D
Figure 11. Endocast of ELGNM 1999.5.1 within a transparent skull in le lateral (A), right lateral (B), posterior (C), and dorsal (D) views,
and a close up of the endocast in le lateral view (E). Abbreviations: , forebrain; hb, hindbrain; hyp, hypophysis; mb, midbrain; ot, olfactory
tract; pb, pineal body; uz, ‘unossied zone’; ve, vestibule. Scale bars in A-D = 4 cm, and in E = 2 cm.
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20 • George et al.
hindbrain. Such an angle between the forebrain and hindbrain
can be observed in N. mfumukasi, P. ma c ka y i, D. feliceps, K . fossilis,
and Lystrosaurus, but not in R. procurvidens (although this may
be related to taphonomic dorsoventral aening of the specimen
used to generate the endocast) (Edinger 1955, Castanhinha et
al. 2013, Laaß 2015, Laaß and Kaestner 2017, Laaß et al. 2017,
Simão-Oliveira et al. 2019). Dorsal to the ventrally directed por-
tion of the endocast, a small posteriorly directed projection can
be identied as an ‘unossied zone’, a feature usually seen in di-
cynodont endocasts and suggested to house vascular sinuses
(Laaß 2015, Laaß et al. 2017, Simão-Oliveira et al. 2019). e
midbrain of G. traquairi is not as dorsoventrally elongate as that
of D. feliceps (Laaß et al. 2017). e hypophysis of G. traquairi
is identiable as a ventral extension of the posterior half of
the endocast, similar to that of N.mfumukasi, P. m a c k a y i, R .
procurvidens, and D. feliceps (Castanhinha et al. 2013, Laaß 2015,
Laaß et al. 2017, Simão-Oliveira et al. 2019).
e hindbrain of G. traquairi is mediolaterally wider than
the forebrain and the descending portion of the midbrain (Fig.
11E). is is unlike the endocasts of N.mfumukasi, P. mack a y i ,
R. procurvidens, D. feliceps, and K. fossilis (Castanhinha et al.
2013, Laaß 2015, Laaß and Kaestner 2017, Laaß et al. 2017,
Simão-Oliveira et al. 2019, Araújo et al. 2022). In lateral view,
no clear paraoccular lobe can be observed, and there is no evi-
dence of a paraoccular fossa (which encloses the lobe) in the
supraoccipital. It is possible that Gordonia had no paraoccular
fossae, which are greatly reduced in other bidentalian dicyno-
donts (Angielczyk and Kurkin 2003). However, a proportion-
ally small paraoccular lobe might not be detectable with the
available data for this specimen. All other published dicynodont
endocasts have paraoccular lobes protruding laterally from
the hindbrain (Castanhinha et al. 2013, Laaß 2015, Laaß and
Kaestner 2017, Laaß et al. 2017, Simão-Oliveira et al. 2019).
No medulla oblongata, such as that of R. procurvidens (Simão-
Oliveira et al. 2019), can be condently identied in the endocast
of G. traquairi. Additionally, no longitudinal medial sulcus can be
identied separating the ventral surface of the hindbrain (where
the pons is inferred to be), unlike that of R. procurvidens (Simão-
Oliveira et al. 2019).
e le vestibule is anteroposteriorly short in le lateral
view (Fig. 11E), unlike that of N. mfumukasi, P. m a c k ay i , R .
procurvidens, and D. feliceps, which have anteroposteriorly longer
vestibules relative to total endocast size (Castanhinha et al. 2013,
Laaß 2015, Laaß et al. 2017, Simão-Oliveira et al. 2019). e le
vestibule of G. traquairi is not inated, unlike that of K. fossilis
and Kembawacela spp. (Laaß and Kaestner 2017, Angielczyk et
al. 2019, Araújo et al. 2022). Furthermore, the vestibule of G.
traquairi does not taper in anteroposter ior length down its dorso-
ventral length, as in N. mfumukasi, P. m a ck a yi , and R. procurvidens
(Castanhinha et al. 2013, Laaß 2015, Simão-Oliveira et al. 2019).
In posterior view (Fig. 11C), the vestibule of G. traquairi is al-
most as mediolaterally wide as the hindbrain, which is unlike N.
mufumukasi, P. ma c k a y i, R. procurvidens, and D. feliceps, which
have hindbrains that are considerably mediolaterally wider than
their vestibules (Castanhinha et al. 2013, Laaß 2015, Laaß et al.
2017, Simão-Oliveira et al. 2019). e skeletal elements of G.
traquairi surrounding the vestibule are not taphonomically al-
tered to an extent that would cause such extreme mediolateral
widening of the vestibule (e.g. dorsoventral aening of the
skull), and this wide morphology likely approximates the true
vestibular morphology as it lls most of the prootic region.
Body mass estimates and encephalization quotient
values of Gordonia
Body mass estimates ranged from 7726.81 g to 86807.11 g
(Table 1). Since the greatest value is about 3.8 times larger than
the next greatest value (22999.57 g), and there are substantially
smaller dierences between the other estimates, the greatest es-
timate was excluded from calculation of the average body mass
value (11882.01 g). e endocast volume without the pineal
body (9850.9 mm3) is about 90% of the volume with the pineal
body (10930.04 mm3), and consequently, the Manger EQ value
calculated without the pineal body (0.2) is about 91% of the
value calculated with the pineal body (0.22).
Phylogenetic analysis results
e only notable dierences between the scorings for the
‘Gordonia traquairi’ OTU and ‘e Elgin Marvel’ OTU that are
not related to missing data for either OTU are continuous char-
acters 12 (angle between ascending and zygomatic processes of
the squamosal is 1.396 in the former OTU and 2.379 in the laer
OTU) and 13 (angulation of the occiput relative to the palate, ex-
pressed as the ratio of dorsal and basal lengths of the skull is 1.067
in the former OTU and 1.49 in the laer OTU). e phylogen-
etic analysis resulted in 1 most parsimonious tree (MPT) with
a length of 1370.86 steps (consistency index = 0.229, retention
index = 0.708) (Fig. 12). ‘e Elgin Marvel’ OTU is robustly
recovered as the sister-taxon to the ‘Gordonia traquairi’ OTU
(recovered in 97 replicates, Bremer support value = 3.317), sup-
porting the referral of ELGNM 1999.5.1 to Gordonia traquairi.
Furthermore, Gordonia is recovered within a clade also con-
taining Jimusaria (recovered in 60 replicates, Bremer support
value = 2). Synapomorphies uniting this clade are continuous
Ch. 8: 0.117–0.118 → 0.094–0.113 (narrow median pterygoid
plate relative to basal skull length), continuous Ch. 11: 9.599–
9.663 → 9.319 (area of internal nares small relative to basal skull
length), continuous Ch. 12: 9.9–10.25 → 8.9 (small angle be-
tween ascending and zygomatic process of the squamosal), con-
tinuous Ch. 13: 0.920–0.926 → 0.944-0.922 (strong angulation
of the occiput relative to the palate), discrete Ch. 38: 1 → 0 (ab-
sence of prefrontal bosses), discrete Ch. 45: 2 → 1 (preparietal
present and ush with skull roof), discrete Ch. 67: 1 → 0
(squamosal separated by tabular bone from supraoccipital),
discrete Ch. 107: 1 → 0 (tabulars contact opisthotics), and
discrete Ch. 172: 1 → 0 (unornamented anterior face of den-
tary symphysis). Within this clade, Jimusaria sinkianensis
is recovered immediately outside of a subclade containing
Jimusaria monanensis and Gordonia (recovered in 56 replicates,
Bremer support value = 1.889). is result mirrors Kammerer
(2019), Angielczyk et al. (2021), and Liu (2021) in recovering
Gordonia as the sister-taxon to J. sinkianensis, but not Kammerer
and Ordoñez (2021), Macungo et al. (2022), and Shi and Liu
(2023). Instead, these studies recover J. sinkianensis (Jimusaria
spp. in the case of Shi and Liu (2023)) immediately outside
of the clade containing Gordonia and ‘higher’ dicynodontoids
(e.g. Kannemeyeriiformes).
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Any update • 21
Moreover, our phylogenetic analysis recovers a relatively in-
clusive Lystrosauridae containing Peramodon, Daptocephalus,
Dinanomodon, Turfanodon, the Jimusaria + Gordonia clade,
Syops, Basilodon, Sintocephalus, Euptychognathus, and
Lystrosaurus [all taxa more closely related to Lystrosaurus than
to Kannemeyeria or Dicynodon; see Kammerer and Angielczyk
(2009) for clade denitions], but this large Lystrosauridae
clade is not strongly supported (recovered in <50 replicates,
Bremer support value = 0.806). Synapomorphies uniting this
version of Lystrosauridae in our analysis are continuous Ch. 3:
0.253 → 0.23–0.244 (small width of interorbital skull roof relative
to basal length of skull), continuous Ch. 7: 1.468–1.485 → 1.380–
1.443 (dorsoventrally short anterior pterygoid keel in lateral
view relative to height of non-keel ramus), discrete Ch. 98: 2 → 1
(basisphenoid contribution to the basisphenoid–basioccipital
tuber slopes anterodorsally at a steeper angle such that the
parabasisphenoid contribution is still somewhat ridge-like but
the portion of the ridge on the anterior surface of the tuber is
more vertically-oriented), discrete Ch. 142: 2 → 3 (number of sa-
cral vertebrae is six or more), discrete Ch. 165: 1 → 0 (proximal
articular surface of the femur present as a weak swelling that is
mostly limited to the proximal surface of the bone).
Recovery of Gordonia and Jimusaria within Lystrosauridae is a
result not found in other recent phy logenetic analyses (Kammerer
2019, Angielczyk et al. 2021, Kammerer and Ordoñez 2021, Liu
2021, Macungo et al. 2022, Shi and Liu 2023), although the re-
covery of Jimusaria in this clade has previously been obtained
by Kammerer et al. (2011). Additionally, Lystrosauridae and
Kannemeyeriiformes represent sister-taxa in the recovered top-
ology, a result previously obtained by Macungo et al. (2022), but
unlike other recent topologies that found Kannemeyeriiformes
to be the sister-taxon of a Gordonia + J. sinkianensis clade
(Kammerer 2019, Kammerer and Ordoñez 2021, Liu 2021),
or Kannemeyeriiformes to be the sister-taxon of a clade con-
taining Basilodon, Sintocephalus, Peramodon, Daptocephalus,
Dinanomodon, and Turfanodon (Shi and Liu 2023).
e stratigraphically problematic Chinese taxon Kunpania
scopulusa is here recovered as the sister-taxon to all other
bidentalians, rather than in the basal dicynodontoid position
found by Angielczyk et al. (2021). Angielczyk et al. (2021)
commented on the extremely weak support for Kunpania as a
dicynodontoid, so this minor lability in its position on the tree
is unsurprising. e more basal position of Kunpania would be
consistent with an older age for the unit from which it is known
(Upper Quanzijie Formation; Angielczyk et al. 2021).
Jackknife resampling and/or Bremer supports reveal that
many of the recovered clades in the analysis herein are un-
stable, including Bidentalia (recovered in <50 replicates, Bremer
support value = 0.35), Cryptodontia (recovered in <50 rep-
licates, Bremer support value = 1.864), Dicynodontoidea (re-
covered in <50 replicates, Bremer support value = 0.350), and
Kannemeyeriiformes (recovered in 61 replicates, Bremer sup-
port value = 0.350).
DISCUSSION
Evolutionary relationships of Gordonia and late Permian
biogeography
A notable nd of the phylogenetic analysis herein that is mir-
rored in some other studies (Kammerer 2019, Angielczyk et al.
2021, Kammerer and Ordoñez 2021, Liu 2021, Macungo et al.
2022) is that Gordonia forms a clade with Jimusaria (Fig. 12).
Of the synapomorphies uniting this clade, the narrow median
pterygoid plate relative to basal skull length (continuous Ch. 8:
0.117–0.118 → 0.094–0.113) is of particular interest. In both
Gordonia and Jimusaria, the median pterygoid plate is very narrow
compared to other Permian dicynodontoids (e.g. Dicynodon,
Turfanodon, and Daptocephalus), indicating that these two taxa
comprise a subclade of dicynodontoids characterized by this
anatomical trait. Gordonia and Jimusaria also have anterior ptery-
goid rami that do not are laterally to the same degree as other
dicynodontoids [although IVPP V31929 (referred to Jimusaria
monanensis) has anterior rami that are more laterally than other
Jimusaria specimens], and somewhat similar lateral dentary
shelves (that of Gordonia is more strongly anterodorsally angled)
(Shi and Liu 2023). Additionally, Kammerer et al. (2011) note
Table 1. Body mass and encephalization quotient calculations, and relevant measurements.
Basal skull length 166.34 mm
Humerus length 100 mm
Minimum humerus circumference 78 mm
Body mass from equation 1 (Quiroga 1980) 12426.64 g
Body mass from equation 2 (Hu et al. 2005) 22999.57 g
Body mass from equation 3 (Castanhinha et al. 2013) 8273.41 g
Body mass from equation 4 (Campione and Evans 2012) 86807.11 g
Body mass from equation 5 (Castanhinha et al. 2013) 7726.81 g
Body mass from equation 6 (Campione and Evans 2012) 7983.62 g
Average body mass (excluding value from equations 4) 11882.01 g
Endocast volume (excluding the olfactory bulbs and most of the olfactory tract) 10930.04 mm3
Endocast volume without pineal body (excluding the olfactory bulbs and most of the olfactory tract) 9850.90 mm3
Pineal body volume 1079.15 mm3
Pineal body as % volume of endocast 9.87%
Manger’s encephalization quotient 0.22
Manger’s encephalization quotient without pineal body 0.2
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22 • George et al.
that J. sinkianensis has a narrow snout and Shi and Liu (2023)
describe J. sinkianensis as having a narrow sagial crest with only
slight dorsal exposure of the parietal, both characteristics iden-
tiable in Gordonia. Further investigation of the similarities and
dierences between these two taxa is needed to test the validity
of this newly proposed subclade. e other synapomorphies
uniting the Gordonia and Jimusaria clade are not unique to
this clade, but their distribution in Dicynodontoidea is worth
exploring in greater detail. ere is also taxonomic importance
to such investigation since our phylogenetic analysis recovers J.
sinkianensis immediately outside of a clade containing Gordonia
and J. monanensis, raising doubt about the monophyletic nature
of Jimusaria (in which case it could be synonymized with
Gordonia, which has priority). It is possible that this subclade
of dicynodontoids might have also been one of several to cross
the Permo-Triassic boundary (alongside Lystrosaurus spp. and
Figure 12. Simplied version of the MPT (1370.86 steps, consistency index = 0.229, retention index = 0.708) focusing on portraying the
relationships within Bidentalia. Values le of nodes indicate replicates recovered aer Jackknife resampling (top) and Bremer supports
(boom).
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Any update • 23
Kannemeyeriiformes), as the holotype of J. sinkianensis was col-
lected from the Guodikeng Formation (Angielczyk et al. 2022),
which has recently been conrmed to span the Permo-Triassic
boundary (Yang et al. 2021). However, compounding geo-
logical factors and imprecise historical records have made recon-
structing statigraphic relationships dicult in the Guodikeng
Formation, so a Permian age for J. sinkianensis cannot be ruled
out (Yang et al. 2021, Angielczyk et al. 2022). Similarly, the
Laotian dicynodontoids Counillonia superoculis Olivier et al.,
2019 and Repelinosaurus robustus Olivier et al., 2019 are from
strata (the Purple Claystone Formation; Olivier et al. 2019) that
have recently been shown to span the Permo-Triassic boundary
(if not be entirely Early Triassic) (Rossignol et al. 2016), but
given the range of error involved in radiometric dates it has been
suggested that they are actually Permian (Liu 2020b).
A close relationship between Gordonia (from Elgin, Scotland,
United Kingdom), J. sinkianensis [from Dalongkou, Xinjiang,
China (Li et al. 2008, Angielczyk et al. 2022)], and J. monanensis
[Tumed Right Banner, Nei Mongol, China (Shi and Liu 2023)]
could be evidence of a Laurasian dicynodontoid clade. In
general, dicynodonts were widespread animals and phylogenetic
analyses for this group indicate a number of trans-hemispheric
sister-taxon relationships. For example, lineages branching o
from Dicynodontoidea phylogenetically proximal to Gordonia
according to our phylogenetic analysis contain species so far
only known from Russia (Peramodon amalitzkii Sushkin, 1926)
and southern Africa (Dinanomodon gilli and Daptocephalus
spp.). is adds to a growing body of evidence for Permian ther-
apsids having close relatives on far sides of the world, including
other evidence from the Scoish ‘Elgin Reptiles’. Namely, the
cryptodont dicy nodont Geikia is known from species in Scotland
and Tanzania: G. elginensis and G. locusticeps Huene, 1942, re-
spectively (Newton 1893, Huene 1942). e pylaecephalid
dicyndont Diictodon feliceps is also known from both South
Africa and China (Angielczyk and Sullivan 2008). e South
African cryptodont Tropidostoma Owen, 1876, has consistently
been found to be the sister-taxon to the Russian Australobarbarus
Kurkin, 2000 (e.g. Kammerer et al. 2011, 2015, Kammerer and
Smith 2017). Other Permian therapsid clades show similar dis-
tributions. e akidnognathid therocephalians Annatherapsidus
Kuhn, 1963 and Shiguaignathus Liu and Abdala, 2017 are closely
related and the former is from Western Russia, while the laer
is from Nei Mongol, China (Ivakhnenko 2011, Liu and Abdala
2017). Another akidnognathid taxon, Euchambersia, is known
from two species: E. mirabilis Broom, 1931 from South Africa
and E. liuyudongi Liu and Abdala, 2022 from Nei Mongol. e
rare therocephalians Ichibengops Huenlocker et al., 2015, and
Mupashi Huenlocker and Sidor, 2016, which are endemic
to the Luangwa Basin of Zambia, have been recovered as re-
lated to Russian taxa (Huenlocker and Sidor 2016). Even the
gorgonopsian Inostrancevia Amalitzky, 1922, long considered
a Russian endemic taxon, has been found in South Africa
(Kammerer et al. 2023). Similar paerns are observed in non-
synapsid tetrapods as well. e Scoish parareptile Elginia (a
contemporary of Gordonia from the Cuies Hillock Formation)
has also been discovered in Nei Mongol, China (Liu and Bever
2018), and closely related chroniosuchians are known from
both European Russia, the Henan Province of China, and
Xinjiang (including the same stratigraphic section that has
yielded J. sinkianensis) (Buchwitz et al. 2012, Liu 2020a). is
body of evidence strongly indicates that the biogeography of late
Permian tetrapods is complex, with taxa diversifying and quickly
spreading to distant regions across Pangea. Future research that
takes a closer look at the phylogenetics and biogeography of late
Permian tetrapods, climate, and precipitation and other environ-
mental factors across Pangea could shed light into these Permian
distribution paerns.
e relatively inclusive Lystrosauridae recovered in our ana-
lysis is not well supported (recovered in <50 replicates, Bremer
support = 0.81) and the synapomorphies uniting the clade
are not unambiguously unique to its members. Instability in
this group is related to larger issues involving high lability in
Dicynodontoidea and potential paraphyly of Cryptodontia;
for recent discussion see: Angielczyk and Kammerer (2017),
Angielczyk et al. (2021), and Shi and Liu (2023).
Development and evolution of the non-mammalian
therapsid pineal body
e pineal body of Gordonia is the most remarkable feature
of its endocast, with its enlarged anterodorsal projection and
triangular shape (Fig. 11E) being the most prominent dier-
ences from other therapsids with reconstructed endocasts
(e.g. Edinger 1955, Rowe et al. 2011, Benoit et al. 2017a). is
morphology is here hypothesized to be a developmental artefact
related to exaggeration of the sagial crest. ELGNM 1893.6 ("G.
juddiana") lacks a prominent sagial crest, and instead shows a
temporal bar that is not dorsally oset from the rest of the skull
roof. Considering that ELGNM 1893.6 ("G. juddiana") is a
smaller specimen than ELGNM 1999.5.1, and as such probably
represents an earlier ontogenetic stage, sagial crest develop-
ment is probably an allometric feature in Gordonia [as in other
non-mammalian synapsids with known growth series ( Jasinoski
et al. 2015, Jasinoski and Abdala 2016)]. ELGNM 1893.6 ("G.
juddiana") also has a pineal foramen angled perpendicular to the
skull roof, unlike ELGNM 1999.5.1 and other larger G. traquairi
specimens in which the pineal foramen is angled anterodorsally.
is is also related to exaggeration of the sagial crest, with in-
creased height and curvature of the intertemporal bar resulting
in changes to the position and orientation of the foramen. In as-
sociation with these changes, the pineal body of Gordonia would
have enlarged, elongated, and shied from being a tubular and
vertical structure (as in, e.g. Lystrosaurus; Edinger 1955) to an
anterodorsally expanded structure in order to connect the pineal
foramen to the brain. e anterodorsal angulation of the for-
amen is likely also related to the anterior expansion of the pineal
body that grants it the triangular shape in lateral view, which is
unlikely to be a preservational artefact as the skull roof is well-
preserved. If this hypothesis is correct, it implies a substantial
degree of neuroanatomical plasticity in early therapsids.
Many other non-mammalian therapsids also had distinctive
pineal bodies (Fig. 13), most also in association with elabor-
ation of the skull roof. In the dinocephalian Moschops Broom,
1911, a taxon with intense cranial pachyostosis resulting in the
formation of a frontoparietal ‘dome’, the pineal body is greatly
elongated, occupying a ‘pineal tube’ that extends through the
‘dome’ (Benoit et al. 2017b). Rhachiocephalid dicynodonts
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24 • George et al.
(Kitchinganomodon Maisch, 2002 and Rhachiocephalus Seeley,
1898) probably also had an elongated pineal body, as they pos-
sess narrow temporal bars with pineal foramina strongly angled
anteriorly. As can be seen in the Rachiocephalus magnus Owen,
1876 specimen BP/1/1512, which provides a cross-sectional
lateral view of the midline of the skull, the lumen of the pineal
body is elongate (Supporting Information, Fig. S30). In the
endocasts of the Triassic bidentalians Lystrosaurus and Placerias
Lucas, 1904 (based on natural casts and cranial sections, not CT
data), the pineal bodies also have an elongate, dorsally projecting
morphology (Simão-Oliveira et al. 2019). e tall sagial crest
of Placerias and other kannemeyeriiforms is related to the en-
larged jaw musculature in this group (Angielczyk et al. 2018).
In the case of Gordonia, the sagial crest would have supported
large masticatory muscles, which implies that the pineal body
may have been reshaped as a consequence of feeding or trophic
adaptations in this taxon. As such, we consider the remarkable
pineal body of G. traquairi to most likely be a ‘spandrel’ (sensu
Gould and Lewontin 1979) that is a by-product of other factors
rather than an adaptive feature.
Ontogenetic variation in the pineal body in early therap-
sids is currently poorly understood; we suspect that the elab-
orate morphologies of the pineal bodies in the aforementioned
taxa developed late in ontogeny, but this needs to be tested by
CT-scanning growth series. Excellent growth series are known
for Lystrosaurus (Ray 2005), Aulacephalodon Seeley, 1898
(Tollman et al. 1980), and Diictodon (Ray and Chinsamy 2004).
Substantial variation in skull size and degree of pachyostosis is
also present in the known sample of Moschops (Broom 1911),
so the record is amenable to such a test. Many non-mammalian
therapsids with less baroque skull roof morphologies had smaller,
less elongate pineal bodies, and exaggerated versions of this
structure probably evolved multiple times within erapsida.
Variation in this structure between closely related therapsid taxa
and potentially during the growth history of single individuals
has confounding implications for analyses of relative endocast
size, which, combined with the probably minimal contribu-
tion of actual neural tissue to this region (which may have been
mostly glandular tissue), means that therapsid EQs should be
calculated with the pineal body volume excluded.
Variation in encephalization quotient throughout erapsida
e EQ of Gordonia (0.22 with pineal body, 0.2 without
pineal body) is within the range for most non-mammalian
therapsids (approximately 0.05–0.2) but greater than all
other sampled dicynodonts (0.06–0.17) with the exception
of Kawingasaurus (0.43), which is an extreme outlier for the
clade that is more similar to that of derived cynodonts closely
related to crown mammals, such as Hadrocodium Luo et al.,
2001 (0.51) and Morganucodon Kühne, 1949 (0.31) (Fig.
14). Although Laaß and Kaestner (2017) argue that the in-
crease in brain size in Kawingasaurus was an adaptation for a
specialized fossorial lifestyle, a similar argument cannot be
made for Gordonia. ere is no direct evidence indicating that
G. traquairi was a quasi- or obligately fossorial taxon, as has
been suggested for cistecephalids (such as Kawingasaurus)
(Cox 1972, Angielczyk et al. 2019, Kammerer 2021, Macungo
et al. 2022).
Moschognathus
Cynariops
Chiniquodon
Rastodon
Dicynodon
Gordonia
Lystrosaurus
Placerias
Therapsida
Dinocephalia
Theriodonta
Gorgonopsia
Cynodontia
Dicynodontia
Dicynodontoidea
Figure 13. Variation in endocast morphology throughout non-mammalian therapsids with a focus on the pineal body. Silhouees of endocasts
(besides that of G. traquairi) and template from Simão-Oliveira et al. (2019), used with permission of Daniel de Simão-Oliveira. Endocasts not
too scale.
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Any update • 25
e considerable dierence between the EQ of Gordonia
and the most phylogenetically proximate of the sampled taxa,
Lystrosaurus (0.06), is noteworthy (Fig. 14). However, it should
also be noted that measurement of the endocast volume of
Lystrosaurus was carried out with historical techniques rather
than through modern CT scanning and processing, which might
contribute to the drastic dierence in EQ (Quiroga 1980).
Additionally, the Gordonia endocast is incomplete (in particular
the olfactory tract and bulbs), which might actually mean that
EV is being underestimated, and thus EQ as well. e large dif-
ference in EQ between these two closely related taxa and be-
tween dicynodontoids and cistecephalids is a reminder that
more neuroanatomical data, from a broader range of species
over time, is needed for dicynodonts. With this said, substantial
uncertainty related to EQ paerns in synapsids is probably in-
escapable, given the incomplete ossication of their braincases
making exact determination of endocranial volume impossible
for most taxa.
ere is no clear gradual increase in proportional brain size
leading up to cynodonts from basal therapsids (Fig. 14). is is
drastically unlike what is seen within Cynodontia, where brain
size, and other neuroanatomical characteristics, increase leading
up to Mammalia (although whether this increase occurred over
evolutionary pulses or gradually is unclear) (Rowe et al. 2011,
Rowe and Shepherd 2016, Rowe 2017, Homann and Rowe
2018, Wallace et al. 2019, Benoit et al. 2023, Kerber et al. 2023).
Instead, non-cynodont therapsids had a general range of EQs
(0.05–0.2) that varied within and between clades. A notable ex-
ception to this is the clade Dinocephalia, which is characterized
by very low EQs (0.02–0.03). Additionally, there are two species
with EQ values greater than 0.3 in non-mammaliaform therap-
sids: the Late Triassic cynodont erioherpeton Bonaparte and
Barberena, 1975 (0.32) and the aforementioned dicynodont
Kawingasaurus (0.43). ese taxa might have required these pro-
portionally enlarged brains to support dedicated fossorial and/
or social lifestyles (Laaß and Kaestner 2017).
It is also worth noting that conclusions regarding EQs based
solely on endocast data are not equivalent to those based on
brain tissue. Since the endocast shapes of many non-mammalian
therapsids, especially most dicynodonts, resemble those of
non-avian reptiles, it is plausible to infer endocast ll in non-
mammalian therapsids might have been more similar to that
of reptiles, which unlike mammals, do not fully or nearly fully
ll their endocranial cavity with brain tissue (Castanhinha et al.
2013, Caspar et al. 2024). is is corroborated by the fact that
clear ssures are usually not discernible in the endocasts of non-
mammalian therapsids, similar to non-avian reptiles, but not
mammals. ese ssures indicate sulci, and the presence of them
0 0.1 0.20.3 0.40.5 0.60.7 0.
80
.9
Lemurosaurus BP/1/816
Lemurosaurus NMQR1702
Leucocephalus SAM-PK-11112
Struthiocephalus SAM-PK-12049
Moschognathus AM4950
Moschognathus (w/o pineal tube) AM4950
Rastodon UNIPAMPA PV317P
Pristerodon MB.R.985
Niassodon PPN2009-1
Kawingasaurus GPIT-PV-117032
Gordonia ELGNM 1999.5.1
Gordonia (w/o pineal body) ELGNM 1999.5.1
Lystrosaurus MCZ 2124
Cyonosaurus GPIT-PV-60854
Aelurosaurus BP/1/216
Gorgonopsia indet.BP/1/155
Tetracynodon UCMP 42869
Microgomphodon SAM-PK-K10160
Thrinaxodon UCMP 40466
Trirachodon SAM-PK-K4801
Diademodon NHMUK PV R 4092
Diademodon UCMP 42446
Galesaurus AMNH FARB2227
Massetognathus BP/1/4245
Massetognathus PVL 4016
Exaeretodon PVL 2088
Probelesodon PVL 4015
Probainognathus PVL 4169
Therioherpeton MVP 05.22.04
Tritylodon BP/1/5088
Tritylodon BP/1/4778
Brasilodon UFRGS PV1043T
Hadrocodium IVPP 8275
Morganucodon IVPP 8685
Asioryctes ZPAL MgM-I/56
Didelphis TMM M-2517
Manger EQ values
Mammalia
non-mammalian
Mammaliamorpha
non-probainognathian
Cynodontia
Biarmosuchia
Therocephalia
Gorgonopsia
Dinocephalia
Dicynodontia
non-mammaliamorph
Probainognathia
Figure 14. Manger’s encephalization quotients of non-mammalian therapsids, Asiorcytes, and Didelphis.
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26 • George et al.
in endocasts suggests that almost all the endocast is lled by brain
tissue (Laaß and Kaestner 2017). Also, there might have been
a gradual increase in endocast ll as therapsids became more
mammal-like across their evolutionary history. is would mean
distantly related taxa, such as the biarmosuchian Lemurosaurus
Broom, 1949 and the cynodont Diademodon Seeley, 1894 might
have similar EQ values according to the data presented herein,
but also could have had drastically dierent degrees of endocast
ll. Furthermore, endocast ll can change drastically across
ontogenetic stages of modern reptiles as well, e.g. in crocodilians
where the brain can ll anywhere from 29% to 95% of the
endocast depending on ontogeny (Barrios et al. 2023, Ferreira et
al. 2023). Whether the brain ll of non-mammalian therapsids
changed to such a large extent throughout development is un-
known. Such dramatic possibilities and more conservative alter-
natives should not be ruled out when studying non-mammalian
therapsid neuroanatomy.
As a nal caveat, reliable body mass estimates are required
for accurate and precise calculations of EQ. Recent research
has shown that estimating body mass with volumetric methods
A
BC
Figure 15. Life reconstruction of Gordonia traquairi (A), close up of the head with skull overlain (B), and close up of the head with endocast
overlain (C). Illustrations by Sco Reid.
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Any update • 27
yields values that are within much smaller margins of error than
those estimated with regression formulae (Sellers et al. 2012,
Bates et al. 2015, Brassey et al. 2015, Brassey 2016, Romano and
Manucci 2019, Romano and Rubidge 2019, Romano et al. 2019,
Van den Brandt et al. 2023). Additionally, mass estimates made
with volumetric methods are oen substantially lower than those
made with regression formulae in both non-therapsid tetrapod
(Bates et al. 2015, Brassey et al. 2015, Van den Brandt et al. 2023)
and therapsid taxa (Romano and Manucci 2019, Romano and
Rubidge 2019), indicating that values derived through regres-
sion formulae will oen be overestimates. Nevertheless, given
that it is much more feasible and time-ecient to derive body
mass estimates from regression formulae, and that very few taxa
preserve the complete skeletons required for rigorous volu-
metric analysis, it is unlikely that proxy-based mass estimates
using regressions will and should be wholly abandoned among
palaeobiologists
CONCLUSION
e use of µCT scanning has allowed for a new look at the external
and internal skull anatomy of one of the only know n dicynodonts
from Western Europe, Gordonia (Fig. 15). e incorporation of
the new anatomical data into a phylogenetic analysis provides an
updated test of the evolutionary relationships of Gordonia, and
suggests it forms a clade with the Chinese Jimusaria, expanding
our understanding of late Permian therapsid biogeography.
Furthermore, the digital endocast of the brain and vestibule of
G. traquairi are the rst generated for this taxon, and the rst to
be published for a bidentalian dicynodont. e pineal body of
Gordonia has an unusual morphology (that can also be seen in
other non-mammalian therapsids), which can be explained as an
accommodation to t a skull with a proportionally large sagial
crest. Moreover, the EQ of Gordonia is within the range of most
non-mammalian therapsids, and substantially less than that of
mammals and other derived cynodonts. However, due to the
many gaps in our knowledge of non-mammalian therapsid en-
cephalization, there is much uncertainty surrounding how much
EQ data represents neurological variation between taxa.
SUPPLEMENTARY DATA
Supplementary data are available at Zoological Journal of the
Linnean Society online.
ACKNOWLEDGEMENTS
is publication is based on the MRes thesis (part of the Palaeontology
and Geobiology MScR programme) of H.G. at the University of
Edinburgh. We are extremely grateful to Alison Wright, David
Longsta, and Janet Trythall of the Elgin Museum Geology Group for
providing access to, and allowing transport of, the ‘e Elgin Marvel’,
and to Elizabeth Martin-Silverstone for scanning the specimen at the
University of Bristol Palaeobiology Laboratories. We extend our grati-
tude to David Longsta for guiding H.G. through Clashach quarry
to beer understand the geological seing, and to Alison Wright,
Mathew Lowe (University of Cambridge), and Michael Day (Natural
History Museum, London) who provided access to specimens for
H.G. to examine. Additionally, we thank Paige dePolo (University of
Edinburgh) for her assistance in exporting the digital models used in
this study, and Candice Stefanic (Stony Brook University) for her ad-
vice regarding preparing digital models for publication. We also thank
Daniel de Simão-Oliveira (Universidade Federal de Santa Maria) for
permission to use the template in Figure 13, and Sco Reid for creating
the brilliant artwork used in Figure 15. We also thank Julien Benoit for
pointing out a taxonomic error in Figure 13. We are grateful to Kenneth
Angielcyzk (Field Museum) and an editor of ZJLS for reviewing this
work, which has substantially improved its quality. H.G. is supported
by a University of Bristol Scholarship. D.F.’s work on using CT to study
the Elgin Reptiles was supported by the Royal Commission for the
Exhibition of 1851 Science Fellowship. S.L.B.’s work on brain evolu-
tion in tetrapods is supported by the Swedish Research Council (‘e
Evolution of Minds’ project) and his work on early mammal evolution
is supported by a European Research Council Starting Grant (PalM,
number 756226). Finally, Clare Clark is thanked for intervening in
1997 to prevent the traditional, more destructive analysis of the ‘e
Elgin Marvel’ and suggesting medical scanning instead.
CREDIT STATEMENT
Hady George (conceptualization, data curation, formal analysis, in-
vestigation, methodology, writing original dra, writing review, and
editing), Christian F. Kammerer (conceptualization, data curation,
formal analysis, investigation, methodology, writing original dra,
writing review, and editing), Davide Foa (conceptualization, data
curation, formal analysis, investigation, methodology, writing original
dra, writing review, and editing), Neil D.L. Clark (writing original
dra, writing review, and editing), and Stephen L. Brusae (concep-
tualization, data curation, formal analysis, investigation, methodology,
writing original dra, writing review, and editing).
CONFLICT OF INTEREST
No conicts of interest to be declared.
FUNDING
University of Bristol Scholarship—PhD funding to H.G..
e Royal Commission for the Exhibition of 1851—Fellowship to D.F.
(CT scans).
Swedish Research Council—Grant to S.L.B..
European Research Council—Grant to S.L.B..
DATA AVAILABILITY
e µCT data used in this study and 3D reconstructions are available at
hps://www.morphosource.org/projects/000586798?locale=en
REFERENCES
Amalitzky V. Diagnoses of the new forms of vertebrates and plants from
the Upper Permian on North Dvina. Bulletin de l’Academié des Sciences
de Russie, 6th Series 1922;16:329–40.
Anderson JM, Cruickshank ARI. e biostratigraphy of the Permian and
the Triassic. Part 5. A review of the classication and distribution of
Permo-Triassic tetrapods. Palaeontologia Aicana 1978;21:15–44.
Angielczyk KD, Kammerer CF. e cranial morphology, phylogen-
etic position and biogeography of the upper Permian dicynodont
Compsodon helmoedi van Hoepen (erapsida, Anomodontia).
Papers in Palaeontology 2017;3:513–45. hps://doi.org/10.1002/
spp2.1087
Downloaded from https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlae065/7694288 by University of Bristol Research Station user on 18 June 2024
28 • George et al.
Angielczyk KD, Kammerer CF. Non-mammalian synapsids: the deep
roots of the mammalian family tree. In: Zachos FE, Asher AJ (eds),
Mammalian Evolution, Diversity and Systematics. Berlin: De Gruyter,
2018, 117–98. hps://doi.org/10.1515/9783110341553-005
Angielczyk KD, Kurkin AA. Phylogenetic analysis of Russian Permian
dicynodonts (erapsida: Anomodontia): implications for
Permian biostratigraphy and Pangaean biogeography. Zoological
Journal of the Linnean Society 2003;139:157–212. hps://doi.
org/10.1046/j.1096-3642.2003.00081.x
Angielczyk KD, Sullivan C. Diictodon feliceps (Owen, 1876), a dicyno-
dont (erapsida, Anomodontia) species with a Pangaean distribu-
tion. Journal of Vertebrate Paleontology 2008;28:788–802. hps://doi.
org/10.1671/0272-4634(2008)28[788:dfoadt]2.0.co;2
Angielczyk KD, Hancox PJ, Nabavizadeh A. A redescription of the
Triassic kannemeyeriiform dicynodont Sangusaurus (erapsida,
Anomodontia), with an analysis of its feeding system. Journal of
Vertebrate Paleontology 2018;37(Suppl.1 memoir17):189–227.
Angielczyk KD, Benoit J, Rubidge BS. A new tusked cistecephalid di-
cynodont (erapsida, Anomodontia) from the upper Permian
upper Madumabisa Mudstone Formation, Luangwa Basin, Zambia.
Papers in Palaeontology 2019;7:405–46. hps://doi.org/10.1002/
spp2.1285
Angielczyk KD, Liu J, Yang W. A redescription of Kunpania scopulusa,
a bidentalian dicynodont (erapsida, Anomodontia) from
the ?Guadalupian of northwestern China. Journal of Vertebrate
Paleontology 2021;41:e1922428.
Angielczyk KD, Liu J, Sidor CA et al. e stratigraphic and geographic
occurrences of Permo-Triassic tetrapods in the Bogda Mountains,
NW China—implications of a new cyclostratigraphic framework and
Bayesian age model. Journal of Aican Earth Sciences 2022;195:104655.
hps://doi.org/10.1016/j.jafrearsci.2022.104655
Angielczyk KD, Peecock BR, Smith RMH. e mandible of Compsodon
helmoedi (erapsida: Anomodontia), with new records from the
Ruhuhu Basin, Tanzania. Palaeontologica Aicana 2023;56:88–102.
Araújo R, Fernandez V, Rabbi RD et al. Endothiodon cf. bathystoma
(Synapsida: Dicynodontia) bony labyrinth anatomy, variation and
body mass estimates. PLoS One 2018;13:e0189883. hps://doi.
org/10.1371/journal.pone.0189883
Araújo R, Macungo Z, Fernandez V et al. Kembawacela yajuwayeyi n.
sp., a new cistecephalid species (Dicynodontia: Emydopoidea)
from the Upper Permian of Malawi. Journal of Aican Earth Sciences
2022;196:104726. hps://doi.org/10.1016/j.jafrearsci.2022.104726
Barrios F, Bona P, Paulina-Carabajal A et al. An overview on the
crocodylomorpha cranial neuroanatomy: variabi lity, morphological pat-
terns and paleobiological implications. In: Dozo MT, Paulina-Carabajal
A, Macrini TE, Walsh S (eds), Paleoneurology of Amniotes: Springer
Cham, 2023, 213–66. hps://doi.org/10.1007/978-3-031-13983-3_7
Barry TH. A new dicynodont ancestor from the Upper Ecca (Lower
Middle Permian) of South Africa. Annals of the South Aican Museum
1974;64:117–36.
Bates KT, Falkingham PL, Macauley S et al. Downsizing a giant:
re-evaluating Dreadnoughtus body mass. Biology Leers
2015;11:201502215.
Benoit J, Fernandez V, Manger PR et al. Endocranial casts of pre-
mammalian erapsids reveal an unexpected neurological diversity at
the deep evolutionary root of mammals. Brain, Behavior and Evolution
2017a;90:311–33. hps://doi.org/10.1159/000481525
Benoit J, Manger PR, Norton L et al. Synchrotron scanning reveals the
palaeoneurology of the head-buing Moschops capensis (erapsida,
Dinocephalia). PeerJ 2017b;5:e3496. hps://doi.org/10.7717/
peerj.3496
Benoit J, Kruger A, Jirah S et al. Evolution of facial innervation in
anomodont therapsids (Synapsida): insights from x-ray computerized
microtomography. Journal of Morphology 2018;279:673–701.
Benoit J, Dollman KN, Smith RMH et al. At the root of the mammalian
mind: the sensory organs, brain and behavior of pre-mammalian
synapsids. Progress in Brain Research 2023;275:25–72. hps://doi.
org/10.1016/bs.pbr.2022.10.001
Benton MJ, Spencer PS. Br itish Permian fossil reptile sites. In: Benton MJ,
Spencer PS (eds), Fossil Reptiles of Great Britain. Dordrecht: Springer,
1995, 17–32.
Benton MJ, Walker AD. Palaeoecology, taphonomy and dating of Permo-
Triassic reptiles from Elgin, north-east Scotland. Palaeontology
1985;28:207–34.
Benton MJ, Walker AD. Saltopus, a dinosauriform from the Upper Triassic
of Scotland. Earth and Environmental Science Transactions of the Royal
Society of Edinburgh 2011;101:285–99. hps://doi.org/10.1017/
s1755691011020081
Bertrand OC, Shelley S, Williamson TE et al. Brawn before brains in
placental mammals aer the end-Cretaceous extinction. Science
2022;376:80–5.
Birch S. Sterolithography (laser prototypes Europe). Automotive
Engineering 1993;101:56.
Bonaparte JF, Barberena MC. A possible mammalian ancestor from
the Middle Triassic of Brazil (erapsida-Cynodontia). Journal of
Paleontology 1975;49:931–6.
Boos ADS, Kammerer CF, Schultz CL et al. A new dicynodont
(erapsida: Anomodontia) from the Permian of Southern Brazil and
its implications for bidentalian origins. PLoS One 2016;11:e0155000.
hps://doi.org/10.1371/journal.pone.0155000
Brassey CA. Body-mass estimation in palaeontology: a review
of volumetric techniques. e Palaeontological Society Papers
2016;22:133–56.
Brassey CA, Maidment SCR, Barre PM. Body mass estimates of an ex-
ceptionally complete Stegosaurus (Ornithischia:yreophora): com-
paring volumetric and linear bivariate mass estimation methods.
Biology Leers 2015;11:20140984. hps://doi.org/10.1098/
rsbl.2014.0984
Broom R. On the use of the term Anomodontia. Records of the Albany
Museum 1905;1:266–9.
Broom R. On some new South African Permian reptiles. Proceedings
of the Zoological Society of London 1911;81:1073–82. hps://doi.
org/10.1111/j.1096-3642.1911.tb01976.x
Broom R. Notices of some new genera and species of Karroo fossil rep-
tiles. Records of the Albany Museum 1931;4:161–6.
Broom R. e Mammal-like Reptiles of South Aica and the Origin of
Mammals. London: H.F. & G. Witherby, 1932.
Broom R. New fossil reptile genera from the Bernard Price collection.
Annals of the Transvaal Museum 1949;21:187–94.
Buchwitz M, Foth C, Kogan I et al. On the use of osteoderm features in a phylo-
genetic approach on the internal relationships of the Chroniosuchia
(Tetrapoda: Reptiliomorpha). Palaeontology 2012;55:623–40.
hps://doi.org/10.1111/j.1475-4983.2012.01137.x
Campione NE, Evans, DC. A universal scaling relationship be-
tween body mass and proximal limb bone dimensions in quadru-
pedal terrestrial tetrapods, BMC Biology 2012;10:60. hps://doi.
org/10.1186/1741-7007-10-60
Caspar KR, Gutiérrez-Ibáñez C, Bertrand O, et al. How smart was T. rex?
Testing claims of exceptional cognition in dinosaurs and the appli-
cation of neuron count estimates in palaeontological research, e
Anatomical Record 2024;1-32. hps://doi.org/10.1002/ar.25215
Castanhinha R, Araújo R, Júnior LC et al. Bringing dicynodonts back to
life: paleobiology and anatomy of a new emydopoid genus from the
upper Permian of Mozambique. PLoS One 2013;8:e80974. hps://
doi.org/10.1371/journal.pone.0080974
Clark NDL. e Elgin Marvels (Part 2). Journal of the Open University
Geological Society 1999;20:16–8.
Clark NDL, Adams C, Lawton T et al. e Elgin Marvel: using magnetic
resonance imaging to look at a mouldic fossil from the Permian of
Elgin, Scotland, UK. Magnetic Resonance Imaging 2004;22:269–73.
hps://doi.org/10.1016/j.mri.2003.09.006
Clemmensen LB. Complex star dunes and associated bedforms,
Hopeman Sandstone Formation (Permo-Triassic), Moray Firth. In:
Frostrick L, Reid I (eds), Desert Sediments, Ancient and Modern, Vol .
35. London: Geological Society of London, Special Publications,
1987, 35–231.
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