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Abdominal contents reveal Cretaceous crocodyliforms ate dinosaurs
Matt A. White
a,b,
⇑
, Phil R. Bell
a
, Nicolás E. Campione
a
, Gabriele Sansalone
a
, Tom Brougham
a
,
Joseph J. Bevitt
c
, Ralph E. Molnar
d
, Alex G. Cook
b
, Stephen Wroe
a
, David A. Elliott
b
a
Palaeoscience Research Centre, University of New England, Armidale 2351, New South Wales, Australia
b
Australian Age of Dinosaurs Museum of Natural History, The Jump-Up, Winton 4735, Queensland, Australia
c
Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights 2234, New South Wales, Australia
d
University of California Museum of Paleontology, University of California, Berkeley, CA, USA
article info
Article history:
Received 23 June 2021
Revised 7 January 2022
Accepted 31 January 2022
Available online 10 February 2022
Handling Editor: J.G. Meert
Keywords:
Confractosuchus sauroktonos
Crocodyliform
Crocodylians
Morphometrics
Winton Formation
Cretaceous
Ornithopod
Stomach contents
abstract
Crocodylians are among Earth’s most successful hyper-carnivores, with their crocodyliform ancestors
persisting since the Triassic. The diets of extinct crocodyliforms are typically inferred from distinctive
bite-marks on fossil bone, which indicate that some species fed on contemporaneous dinosaurs.
Nevertheless, the most direct dietary evidence (i.e. preserved gut contents) of these interactions in fossil
crocodyliforms has been elusive. Here we report on a new crocodyliform, Confractosuchus sauroktonos
gen. et sp. nov., from the Cenomanian (92.5–104 Ma) of Australia, with exceptionally preserved abdom-
inal contents comprising parts of a juvenile ornithopod dinosaur. A phylogenetic analysis recovered
Confractosuchus as the sister taxon to a clade comprising susisuchids and hylaeochampsids. The ornitho-
pod remains displayed clear evidence of oral processing, carcass reduction (dismemberment) and bone
fragmentation, which are diagnostic hallmarks of some modern crocodylian feeding behaviour.
Nevertheless, a macro-generalist feeding strategy for Confractosuchus similar to extant crocodylians is
supported by a morphometric analysis of the skull and reveals that dietary versatility accompanied
the modular assembly of the modern crocodylian bauplan. Of further interest, these ornithopod bones
represent the first skeletal remains of the group from the Winton Formation, previously only known from
shed teeth and tracks, and may represent a novel taxon.
Ó2022 The Author(s). Published by Elsevier B.V. on behalf of International Association for Gondwana
Research. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/
licenses/by-nc-nd/4.0/).
1. Introduction
Modern crocodiles are numerical relicts (Simpson, 1944), the
surviving members of a once more speciose group. By contrast,
Mesozoic crocodyliforms occupied a far greater range of feeding
ecologies including dietary extremes such as herbivory and duro-
phagy (Buckley et al., 2000; Melstrom and Irmis, 2019).
Typically, interpreting the diets of these extinct taxa relies on
tooth and skull morphologies (Melstrom and Irmis, 2019;
Drumheller and Wilberg, 2019) or feeding traces on food items
(Noto, Main and Drumheler, 2012; Boyd, Drumheller and Gates,
2013; Njau and Blumenschine, 2006). Among carnivorous forms,
such dietary inferences focus on the largest members of the clade,
Sarcosuchus and Deinosuchus (Schwimmer, 2002), which, at > 11 m
long, were probably capable of dispatching similar-sized
dinosaurians (Sereno et al., 2001; Rivera-Sylva, Frey and
Guzmán-Gutiérrez, 2009). Smaller forms, such as Orgresuchus,
which was discovered in a dinosaur nesting area, may also have
fed on dinosaurs (Sellés et al., 2020), which is corroborated by
tooth marks, and in one case, an embedded crocodyliform tooth
found in an ornithopod bone (Boyd, Drumheller and Gates,
2013). However undeniable evidence of predation on dinosaurs
has been discovered among much smaller representatives of other
clades, with abdominal remains identified within a snake (sauro-
pod hatchlings) (Wilson et al., 2010) and a mammal (juvenile Psit-
tacosaurus)(Hu et al., 2005).
Preserved crocodyliform gut contents are demonstrably rare, a
fact possibly exacerbated by extremely corrosive stomach acids,
which is a hallmark of living crocodylians (Grigg and Kirshner,
2015). The only record of extinct crocodyliform stomach contents
are: 1) a sphagesaurid crocodylomorph found within the abdomi-
nal cavity of the baurusuchid Aplestosuchus from the Late Creta-
ceous of Brazil (Godoy et al., 2014) and 2) indeterminate
carbonized remains found within the gut of a ‘yearling’ crocodylian
from the Eocene Green River Formation (Langston and Rose, 1978).
Here we report on a new crocodyliform from the mid-Cretaceous
https://doi.org/10.1016/j.gr.2022.01.016
1751-7311/Ó2022 The Author(s). Published by Elsevier B.V. on behalf of International Association for Gondwana Research.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
⇑
Corresponding author at: Palaeoscience Research Centre, University of New
England, Armidale 2351, New South Wales, Australia.
E-mail address: fossilised@hotmail.com (M.A. White).
Gondwana Research 106 (2022) 281–302
Contents lists available at ScienceDirect
Gondwana Research
journal homepage: www.elsevier.com/locate/gr
Winton Formation of Australia with exceptionally preserved stom-
ach contents identified as the partial remains of a juvenile ornitho-
pod dinosaur. These contents are the first definitive evidence of
food-web interactions and the first skeletal elements of an ornitho-
pod reported from the Winton Formation. Geometric morphomet-
rics (GM) has proven to be a reliable indicator of feeding behaviour
in extant and extinct crocodyliform species (Erickson et al., 2012;
Walmsley et al., 2013; Piras et al., 2014; Molnar et al., 2015;
Drumheller and Wilberg, 2019) and for the first time the results
are substantiated using actual fossilised stomach contents.
2. Methods
2.1. Scanning
Visualisation of the stomach contents and most of the postcra-
nial elements otherwise hidden by matrix, was achieved via neu-
tron tomography, 3D segmentation and modelling. The fragments
of the concretion housing Confractosuchus sauroktonos were
scanned at the Australian Nuclear Science and Technology Organ-
isation (ANSTO) using Imaging and Medical beamline at 100 mm.
Neutron Radiography was also used on the fragment containing
the abdominal contents at a 15 mm resolution.
2.2. Neutron tomography: Experimental setup and data reconstruction
This study utilised the Dingo thermal neutron radiography/to
mography/imaging station, located at the 20 MW Open-Pool Aus-
tralian Lightwater (OPAL) reactor (Australian Nuclear Science and
Technology Organisation (ANSTO), Lucas Heights, New South
Wales, Australia) to non-invasively image this specimen. The Dingo
facility utilises a quasi-parallel collimated beam of thermal neu-
trons. For this study, a collimation ratio (L/D) of 1000 (Garbe
et al., 2015) was used to ensure highest available spatial resolution,
where L is the neutron aperture-to-sample length and D is the neu-
tron aperture diameter. The field of view was set to 80 47 mm
2
with a voxel size of 15.8 15.8 15.8
l
m and sample-to-
detector distance of 36 mm. Neutrons were converted to photons
with a 30
l
m thick terbium-doped Gadox scintillator screen
(Gd2O2S:Tb, RC Tritec AG); photons were then detected by an Iris
15 sCMOS camera (16-bit, 5056 2960 pixels) coupled with a
Makro Planar 100 mm Carl Zeiss lens. The specimen was scanned
in two vertical parts. Each scan consisted of a total of 3200
equally-spaced angle shadow-radiographs obtained every 0.1125°
as the sample was rotated 360°about its vertical axis with the
specimen’s centre of rotation shifted to 11.4 mm from the detector
edge. Both dark (closed shutter) and beam profile (open shutter)
images were obtained for calibration before initiating shadow-
radiograph acquisition. To reduce anomalous noise, a total of four
individual radiographs with an exposure length of 16 s were
acquired at each angle (Mays, Bevitt and Stilwell, 2017). Total scan
time was 5 days. The individual radiographs were summed in post-
acquisition processing using the Grouped ZProjector function in
ImageJ v.1.51 h, normalised and stitched using IMBL Stitch on the
Australian Synchrotron Computing Infrastructure and tomographic
reconstruction of the 16-bit raw data performed using Octopus
Reconstruction v.8.8 (Inside Matters NV), yielding virtual slices
perpendicular to the rotation axis.
2.3. Digital processing
The resulting images were imported into Mimics version 20
(Materialise HQ, Leuven, Belgium) and converted into 3D surface
meshes of each individual bone. These meshes were imported into
Zbrush 2021.6.2 Pixologic (Pixologic Inc, California, USA), which
was used to rearticulate the digital concretion fragments that also
contained separate internal meshes of the bones. Bones were occa-
sionally split between concretionary fragments, which, following
realignment, could be digitally sutured back together (Fig. 1).
2.4. Phylogeny
The phylogenetic position of Confractosuchus sauroktonos was
assessed by adding it to the phylogenetic dataset of Martin et al.
(2020) which is a derivative of the Turner (2015) matrix. This
matrix was selected because it has been iteratively constructed
to elucidate character evolution in crocodyliforms leading up to
Eusuchia (Leite and Fortier, 2018; Martin et al., 2020; Turner,
2015). The matrix was evaluated under equally weighted parsi-
mony in TNT 1.5 (Goloboff and Catalano, 2016), using 100 replica-
tions of a driven search strategy with random and constrained
sectorial searches, 100 iterations of ratcheting, 20 iterations of
drifting and 5 rounds of fusing, with the analysis stopping when
the same minimum length trees were found in two consecutive
runs. All characters considered as ordered by Turner (2015) were
treated likewise. A further round of branch swapping was per-
formed on the set of most parsimonious trees from the driven
search to ensure thorough exploration of the tree space. Bootstrap
and jackknife values for each node in the strict consensus tree were
calculated from 100 resampled replicates of the driven tree search
strategy, with frequencies summarised using the group present/-
contradicted (GC) metric in TNT. In addition, Bremer supports were
calculated using the BREMER.RUN script.
2.5. Geometric morphometrics
The skull shape of Confractosuchus was assessed within the con-
text of extant and extinct crocodyliforms using two previously
published 2D and 3D geometric morphometric datasets (Piras
et al., 2014; Drumheller and Wilberg, 2019). The 2D analysis
includes a sample of 130 crocodyliform species, used to define
seven ecomorphological categories across Crocodyliformes
(Drumheller and Wilberg, 2019). To this dataset, we added Confrac-
tosuchus and Isisfordia duncani based on their dorsal profiles. The
3D analysis spans 26 (3 extinct) species originally used to investi-
gate modularity and integration in the crocodylian skull (Piras
et al., 2014). Only Confractosuchus could be incorporated into the
3D analysis.
2.5.1. GM analysis 1
Integration into the Drumheller & Wilberg (2019) dataset was
done using tpsDIG2 v2.31 (Rohlf, 2018) and the R package geo-
morph (Adams & Collyer, 2019). The dataset includes a total of
130 taxa (26 extant) from which six landmarks and 24 sliding
semi-land-marks were chosen to capture the shape of the cranium,
snout, and supratemporal fossa. To this dataset, we added Confrac-
tosuchus and Isisfordia, based on their respective right sides, which
were mirrored to generate fully bilaterally symmetric skulls and
appended to the Drumheller & Wilberg (2019) dataset using a cus-
tom code (Appendix A).
2.5.2. GM analysis 2
Confractosuchus was also incorporated into 73 out of 90 unilat-
eral 3D landmarks (digitized on the left side of the skull; Supple-
mentary Data,Fig. S1) identified by Piras et al., (2014). These
data were obtained from juvenile–adult specimens of 23 extant
species (Alligatoridae: 157 individuals, 8 extant species; Crocodyl-
idae: 223 individuals, 14 extant species; Gavialis gangeticus:20
individuals) and 3 fossil representatives (Voay robustus (Brochu,
2007a), Crocodylus ossifragus (Dubois, 1908), and Dollosuchoides
densmorei (Brochu, 2007b). Data from Piras et al. (2014) were
M.A. White, P.R. Bell, Nicolás E. Campione et al. Gondwana Research 106 (2022) 281–302
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Fig. 1. Work utilizing Zbrush to digitally reconstruct and display the holotype specimen of Confractosuchus sauroktonos gen et sp. nov. (a) importing raw files; (b) merging
subtools; (c) colouring subtools; (d) aligning concretion fragments and internal bone meshes, digitally joining bones from separate digital concretionary fragments, repairing
surface artefacts of the 3D mesh files, projecting restored mesh to original raw mesh retaining original specimens’ morphology; (e) digital specimen in situ within the digital
concretionary fragment.
M.A. White, P.R. Bell, Nicolás E. Campione et al. Gondwana Research 106 (2022) 281–302
283
collected with an Immersion Microscribe G2, whereas 3D land-
marks on Confractosuchus were digitized in the software IDAV
Landmark. Successively, a generalized Procrustes analysis, has
been performed in the R package ‘‘Morpho” (Schlager, 2013).
3. Descriptions and results
3.1. Systematic palaeontology
Crocodyliformes Hay 1930
Mesoeucrocodylia Whetstone & Whybrow 1983
Neosuchia Benton & Clark 1988
Eusuchia Huxley 1875
Confractosuchus gen. nov.
Type species. Confractosuchus sauroktonos gen. et sp. nov.
Diagnosis. As for species.
3.2. Etymology
Confractus (‘broken’, Latin), referring to the shattered concretion
in which the holotype was preserved, and suchus (derived from the
Greek, Soûkhos), referring to the Egyptian crocodile god Sobek;
sauros (‘lizard’, Greek), a common word used as a suffix for dino-
saur genera, and ktonos (‘killer’ Greek) referring to its abdominal
contents.
3.3. Diagnosis
Neosuchian with the following autapomorphies: two pairs of
longitudinal ridges on the rostrum that appear to span the pre-
frontal and lacrimal bones and terminate mid-rostrum; strongly
regionalised vertebral assembly consisting of incipiently pro-
coelous cervicals (c3–5), strongly procoelous thoracics (t1–2),
incipiently procoelous (t3, ?t13) and amphicoelous mid-thoracic
vertebrae (t4–7, ?9–12) (Fig. 2).
3.4. Holotype
AODF (Australian Age of Dinosaurs Fossil, Winton) 0890; a near-
complete skull with dentition and semi-articulated postcranial
skeleton missing the tail and hind limbs (Figs. 2 - 3,Supplementary
Data,Fig. S2-4). It was estimated to be around 2–2.5 m in length.
3.5. Horizon and locality
Elderslie Station, Winton Shire, central-western Queensland,
upper Winton Formation (Cenomanian), ca 93 Ma (Cook et al.
2013; Tucker et al., 2013, 2017); (AODL) Australian Age of Dino-
saurs Locality 0120 (Fig. 4).
3.6. Geological and sedimentological setting.
The Winton Formation is the uppermost unit of the Eromanga
Basin, part of the Great Australian Super Basin, an intracontinental
sag basin, which formed during the Jurassic to Cretaceous in inland
eastern Australia (Cook et al., 2013). The Winton Formation com-
prises labile sandstone, mudstones, claystones and minor coal all
of which have been deeply weathered during the Cenozoic. The
sediments originated from the Whitsundays Volcanic Province
(Cook et al. 2013; Tucker et al. 2016), and were deposited in estu-
arine (basal), lacustrine and fluvial depositional settings. Sand-
stones represent high sinuosity channel and related crevasse
splay deposits, whereas the mudstones and claystones represent
floodplain and lacustrine deposition. Coals, silicified peat beds
and richly carbonaceous shales represent peat swamp conditions
in the lower part of the formation.
The holotype of Confractosuchus sauroktonos (AODF0890) was
located in situ 1 m below the surface during exploratory excava-
tions of poorly-preserved sauropod remains that were found
exposed on the surface within montmorillonite-rich vertisol (com-
monly termed black-soil), which was about 1 m thick. This layer
superimposed an organic rich bluish-grey volcanogenic clay with
sandstone lenses. Confractosuchus was located within a concretion
at the transition from clay to black-soil. No additional sauropod
remains were found in association with AODF0890, therefore the
original relationship between the sauropod remains and those of
AODF0890 are unknown; however, the sauropod remains are
clearly reworked from underlying layers (Hocknull et al., 2009;
White et al., 2020; Hocknull et al., 2021; Poropat et al., 2021)
(Fig. 4).
3.7. Taphonomic remarks
The skeleton of Confractosuchus was found articulated-to-
associated in life position but lacking most of the pelvic girdle, hin-
dlimbs and the tail. The dorsal osteoderms are randomly dispersed
throughout the skeleton with none in situ. A large cluster of osteo-
derms that formed the ventral shield are preserved beneath the
pterygoids and cervical vertebrae and are mostly perpendicular
to their life position. The skull and jaws are tightly occluding but
the dentary has shifted posteriorly relative to the cranium. The
pre-sacral axial skeleton is largely complete but ‘segmented’ into
discontinuous strings of cervical and thoracic vertebrae; thoracic
vertebrae 5–7 have become disarticulated and separated from
their corresponding ribs, which are also scattered along with the
entire gastral basket. The forelimbs are close to life position but
are disarticulated; the right manus is disarticulated on the right-
hand side of the rostrum whereas elements of the left manus are
randomly dispersed around the left shoulder girdle (Fig. 3 and Sup-
plementary Data,Fig. S4). There is no apparent evidence of preda-
tion/scavenging (i.e. shed teeth or tooth marks); however, this
cannot be ruled out given the absence of the hind-limbs and tail,
which may in itself have been the result of scavenging.
The pattern of preservation of AODF0890 is consistent with
other articulated-to-associated crocodylomorph fossils in the Win-
ton Formation (Syme and Salisbury, 2014) that were hypothesised
to have been interred after a relatively brief period of subaquaeous
decay in a low-energy environment (Syme and Salisbury, 2014,
2018).
Neutron tomography permitted visualisation of the abdominal
cavity, revealing a remarkable insight into the diet of Confracto-
suchus. The partially-digested remains of a juvenile ornithopod
dinosaur were found concentrated in the anterior part of the
abdominal cavity in the vicinity of the pectoral girdle and bound
unambiguously between the axial skeleton and osteoderms of
the presumed gastral shield (Fig. 3;Supplementary Data,Fig. S4).
The partially-digested remains were identified as ornithopod as
the femur possesses the characteristic pendant fourth trochanter, a
synapomorphy of non-iguanodontian ornithopods (Norman et al.,
2004). The fourth trochanter is elongate compared to other taxa,
including other Australian forms (Molnar and Galton, 1986; Rich
and Vickers-Rich, 1989, 1999) but is similar in extent to Orycto-
dromeus (Brown et al., 2013).
3.8. Description of Confractosuchus sauroktonos
3.8.1. Skull
The skull (28.5 cm long, 19 cm wide) is triangular in dorsal
aspect and brevirostrine (Erickson et al. 2012, see fig. 3.19 in
Grigg and Kirshner, 2015), similar Bernissartia fagesii (see Fig. 1 in
M.A. White, P.R. Bell, Nicolás E. Campione et al. Gondwana Research 106 (2022) 281–302
284
Martin et al. (2020)) and Caiman crocodilus, but distinct from the
broad, platyrostral snout of susisuchids (Salisbury et al., 2006).
Fusion or preservation (via ironstone replacement) masked the cra-
nial sutures, and the majority of cranial bone contacts cannot be
distinguished with certainty (Fig. 2;Supplementary Data,Figs. 2-
4). The external narial opening is wider than long and partially
invaded posteriorly by a blunt triangular projection of the paired
nasals. The lateral edge of the oral margin is straight when viewed
from the dorsal aspect, although the snout is medially pinched
behind the naris, presumably to receive the enlarged fourth den-
tary tooth as in extant crocodylids. A relatively large dislodged
tooth present in this region on the left side may be this tooth. Dor-
sally, the rostrum is ornamented by two pairs of anteroposteriorly-
oriented longitudinal ridges that extend from the anterior margin
of the orbit to a point in line with the fourth maxillary tooth. The
medial ridge originates on the prefrontal, whereas the lateral ridge
occupies the lacrimal; both ridges likely extend onto the maxilla,
although fusion or preservation has obliterated most of the cranial
sutures in this area. These ridges are similar to those possessed by
some allogatorids including Paleosuchus trigonatus (see Fig. 8Cin
Brochu (1999)), Alligator mississippiensis (see Fig. 4CinBrochu
(1999)), and Melanosuchus niger (see Fig. 7C & 61 in Brochu
(1999)). The longitudinal rostral ridges of Confractosuchus are
sub-parallel and anteriorly converging, like those of A. mississippi-
ensis, but are distinctly more dorsally pronounced than in the latter
species. The ridges are also pronounced in both Melanosuchus and
Paleosuchus; however, the lateral ridges are anteriorly divergent,
similar to Caiman, and unlike the convergent ridges of Confracto-
suchus (Fig. 5). Elsewhere, cranial ornamentation consists of shal-
low pits and grooves on the frontal, parietal, postorbital,
squamosal, and lateral surface of the jugal and dentary. Ornamen-
tation, aside from the longitudinal ridges, is not apparent on the
rostrum (Fig. 2); however, ironstone may have masked such orna-
mentation, rendering comparisons problematic. The skull table
(comprising the postorbitals, squamosals, and parietals) is roughly
trapezoidal and concave posteriorly in dorsal aspect and appears
devoid of a median crest like Bernissartia (see Fig. 4JinMartin
et al. (2020)). The supratemporal fenestrae are small and oval, sim-
ilar to but proportionally smaller than in Bernissartia (see Figs. 1-3
in Martin et al. (2020)). The dorsolaterally-facing infratemporal
fenestra is teardrop-shaped and attenuates caudolaterally. The
postorbital bar is poorly preserved and its overall morphology
could not be distinguished. From contact with the postorbitals,
the frontal converges rostromedially before diverging again to a
Fig. 2. Cranial and mandibular osteology of Confractosuchus sauroktonos gen. et sp. nov. (AODF0890). (a-b) dorsal view of skull; (c-d) left lateral view of skull; (e-f), dorsal
view of posterior part of skull with skull table removed following a natural break; (g) synchrotron image of suture margins between the choana and palatines; (h) 3D render of
the choana and palatine suture. Abbreviations: art, articular; cond occ, occipital condyle; cho, choana; den, dentary; eoc, exoccipital; emf, external mandibular fenestra; f,
frontal; intemp, infratemporal fenestra; j, jugal; l, lacrimal; max, maxilla; n, nasal; nar, naris; orb, orbit; pal, palatine; par, parietal; pf, prefrontal; pmax, premaxilla; po,
postorbital; pter, pterygoid; q, quadrate; qj, quadratojugal; s, scapula; sm, suture margins of cervical ribs; sq, squamosal; stp, superior temporal fossa; sur, surangular; t,
tooth. Dotted lines represent suspected suture regions.
M.A. White, P.R. Bell, Nicolás E. Campione et al. Gondwana Research 106 (2022) 281–302
285
lesser degree more rostrally, defining the dorsal margin of the
elliptical orbits (Fig. 2). Unlike Susisuchus and Isisfordia, there is
no defined supraorbital ridge on the frontal. Both jugals are dam-
aged; however, they clearly form the lateral margins of the orbits
and the intertemporal fenestrae. Like Susisuchus and Isisfordia,
the jugal is arched beneath the orbits but flattens when bordering
the intertemporal fenestrae. The exoccipital region is poorly pre-
served masking the supraoccipital and the posterior end of the
parietals. Despite this, an exposed portion reveals that the exoccip-
ital is smooth. All other parts of the braincase are obscured by
matrix.
Imaging and medical beamline (100 mm) revealed a secondary
palate with an anteriorly positioned choana, bound anteriorly by
the palatines and divided by a median septum (Fig. 2GH) like
Bernissartia (see Figs. 2 and 3 in Martin et al. 2020). The anterior
edge of the choana is situated anterior to the posterior edge of
the suborbital fenestra, a characteristic shared with Isisfordia (see
Fig. 4 in Salisbury et al. 2006). The width of the choana is similar
to the minimum mediolateral width of the palatine (Fig. 2GH).
These characteristics combined appear to be unique for Confracto-
suchus; however, this claim is weak given the poor preservation
and/or figuring of comparable specimens.
The occipital surface of the basicranium and basisphenoid ven-
tral to the occipital condyle is currently covered in matrix and
requires preparation to reveal its morphological features; it was
not clear in the synchrotron images. In lateral aspect, the
postorbital-squamosal forms a lateral shelf overhanging the inci-
sura otica, which is only visible on the left side of the skull. The
shelf is ventrally convex with a longitudinal groove bisecting it
centrally, which is mostly formed by the squamosal.
Both mandibular rami are preserved in tight occlusion with the
upper jaws; however, individual sutures delineating the dentary,
splenial, surangular, and angular are indistinct. Grooves in this
region may in fact identify the suture margins (Fig. 2D). The occlu-
sal margin of the dentary is straight and the external mandibular
fenestra is semicircular (height:length 1) (flat ventrally) unlike
the elongate opening in Isisfordia and Crocodylia (Salisbury et al.,
2006). Ornamentation is restricted to the posterior one-quarter
of the mandible and likely did not extend onto the dentary. There
are 4 premaxillary, 12 maxillary and 17 dentary teeth (revealed by
imaging and medical beamline) that occlude in an overbite pattern.
The teeth are conical and homodont with weak mesial and distal
carinae, which is unlike the robust hypertrophied teeth of
hylaeochampsids (Boyd, Drumheller and Gates, 2013; Narváez
et al., 2015) or the small, labiolingually flattened teeth of susisu-
chids that become conical apically (Salisbury et al., 2006).
3.8.2. Vertebrae
The vertebral column is incomplete, consisting of cervicals c3–5
and thoracics t1–7, t?9–13. Interestingly the vertebral form is
Fig. 3. Digital dissection of Confractosuchus sauroktonos gen. et sp. nov (AODF0890) in (a) dorsal aspect; (c) ventral aspect; (c) left lateral aspect; (d) close-up of pectoral region
with ventral osteoderms removed (in ventral aspect); (e) abdominal contents showing ornithopod remains. Abbreviations: c, coracoid; car, carpal; c(no.), cervical vertebrae
(number); cho, choana; cr3, cervical rib 3; d, dentary; f, femur; h, humerus; mcI, metacarpal 1; mc1-1, manual phalanx 1–1; mcI-2, manual phalanx I-2; mcII metacarpal 2;
mcIII metacarpal III; mcV metacarpal 5; man, manus; o, osteoderm; p, manual phalanx; pal, palatines; pter, pterygoids; pu, pubis; r, radius; s, scapula; tm, tooth mark; t(no.),
thoracic vertebrae (number); u, ulna; ul, ulnare; vo, ventral osteoderm.
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Fig. 4. Australian Age of Dinosaurs Locality 0120. (a) schematic of modern-day Australia with the Winton Formation (in green) and the position of Winton (red dot); (b)
satellite image of locality in relation to the town of Winton and the Australian Age of Dinosaurs Museum; (c) image of sauropod bone found in situ at the surface; (d)
stratigraphy of AODL0120; (e) photograph of AODL 0120.
Fig. 5. Examples of extant alligatoroid skulls with rostral ridges compared with Confractosuchus. (a-b) Confractosuchus sauroktonos gen. et sp. nov; (c-d) Paleosuchus
palpebrosus (obtained from Fig. 8 in Brochu (1999); (e-f) Alligator mississippiensis (United States National Museum (USNM) 292078) (modified from Fig. 4 in Brochu (1999);G-
H, Caiman latirostris (modified from Fig. 7 in Brochu (1999)).
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strongly regionalised, revealed via segmentation of the syn-
chrotron data (see diagnosis). The centra and corresponding neural
arches are fused in the thoracic vertebrae but are open in the cer-
vical series, indicating the individual was sub-adult at the time of
death (Brochu, 1996)(Fig. 3A and Fig. 6;Supplementary Data,
Fig. S5).
3.8.3. Cervical vertebrae
There are three preserved cervical vertebrae in articulation,
which we identify as C3-5. The neural arches are missing along
the neurocentral suture indicating that fusion with the vertebral
centra had not yet occurred. The centra have an incipiently pro-
coelous condition in which the anterior surface is shallowly con-
cave and the posterior condyle is shallowly convex with a small
depression in its centre, like that described in Theriosuchus
(Salisbury and Frey, 2001), Pachycheilosuchus (Rogers, 2003) and
Isisfordia cf. I. selaslophensis (Hart et al., 2021). A weekly developed
keel is present on c4 and c5 (Fig. 7;Supplementary Data,Fig. S6).
3.8.4. Thoracic vertebrae
Twelve partial and complete thoracic vertebrae are preserved
consisting of t1–7, and t9?–13? (Figs. 8-9;Supplementary Data,
Fig. S7-8). All thoracic vertebrae have closed neurocentral sutures,
although the neural arches of t5–9 are broken and largely missing.
Thoracic vertebrae t1 and t2 are procoelous, t3 is incipiently
procoelous whereas t4–9 are amphicoelous, t10 appears weakly
procoelous, t11–13 amphicoelous. This varying thoracic condition
has been inadvertently referred to as occurring in some neosuchi-
ans such as Theriosuchus, which is said to have ‘‘at least some pro-
coelous vertebrae” (Turner, 2015), and Shamosuchus where the
cervical and first dorsal vertebra was noted as being procoelous
(Turner, 2015). The allodaposuchids Allodaposuchus hulki (Blanco
et al. 2015), Allodaposuchus palustris (Blanco et al. 2014), Allodapo-
suchus precedens (Narváez et al. 2020) were all described as pos-
sessing strongly procoelous vertebra with no mention of varying
morphology. Vertebral morphology varies between members of
Susisuchidae: Isisfordia duncani was described as a transitional
form with the presence of incipiently procoelous vertebrae,
whereas Susisuchus appears to possess only amphicoelous verte-
brae (see Fig. 5 in Salisbury et al. 2006). Susisuchidae is typically
regarded as phylogenetically near Eusuchia; however, its exact
placement remains uncertain (Salisbury et al. 2006; Turner and
Pritchard 2015). The varying vertebral morphology possessed by
Confractosuchus alludes to a transitional morphology, and also sup-
ports a phylogenetic position near Eusuchia.
The first three thoracic vertebrae have a pronounced hypapoph-
ysis which tapers posteriorly into a ventral keel. A less pronounced
hypapophysis is preserved on t4, which has a correspondingly
reduced ventral keel. Both features are non-existent in t5–13.
The anterior thoracic vertebrae t1–4 have constricted (hourglass-
shaped) centra, whereas the centra of t5–13 are more cylindrical.
Centra increase in length from the first thoracic vertebra. The
Fig. 6. Various vertebrae morphologies identified in Confractosuchus sauroktonos gen. et sp. nov. Vertebrae in: left lateral (a, d, g, j); ventral (b, e, h, k); and posterior (c, f, i, l)
views.(a-c) cervical vertebra 5 with incipiently procoelous condition; (d-f) thoracic vertebra 2 with procoelous condition; (g-i), thoracic vertebrae 3 with amphicoelous
condition; (j-l), thoracic vertebrae 10 with slight incipient condition. Abbreviations: prezyg, prezygapophysis; cond vert, vertebral condyle; di, diapophysis; hyp,
hypapophysis; ns, neural spine; parap, parapophysis; poz, postzygapophysis.
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parapophysis is situated mid-height on the anterior margin of t1-2
and becomes less pronounced on the more posterior centra. Pre-
and postzygapophyses and both the diapophysis and parapophysis
are too poorly preserved and/or digitally represented to warrant
detailed descriptions. The first four vertebrae articulate or are near
enough associated with their corresponding ribs, confirming that
the first four ribs have a distinct branch separating the capitulum
and tuberculum. Posterior of the fourth vertebra, the preservation
and digital resolution deteriorates due to ironstone; however, the
few disarticulated ribs that are preserved in close proximity to t7
and t9 have no distinct branching of the capitulum and tuberculum
and indicate a shift towards aligning in the same plane as is the
case in living crocodiles.
3.8.5. Scapula
Both scapulae are preserved. The right scapula is more complete
than the left, preserving some of the blade and near complete acro-
mion process, scapular synchondrosis and glenoid fossa. The left is
represented by an incomplete scapular synchrondrosis. The blade
is only partially preserved but an antero-posterior constriction is
apparent. In lateral view, the scapular blade is oblique to the syn-
chrondrosis for the coracoid. A shallow curved deltoid crest is vis-
ible is both anterior and medial views. Lateral to the deltoid crest,
in anterior aspect, the acromion process forms a dorsal lip over the
scapular synchondrosis (Fig. 10;Supplementary Data Fig. S9-10).
3.8.6. Coracoids
Both coracoids are near complete with the left missing a small
portion of the articular surface that articulated with the scapula
synchondrosis (coracoid contact surface). It has a pendulous con-
tribution to the glenoid facet on its posterior side. The long ventral
shaft is medially bowed, constricted at the midpoint and becomes
fan-shaped distally (in mediolateral views) with a convex termina-
tion. In medial and lateral views, the blade is almost symmetrical.
The proximal anterior edge has a pointed process. The coracoid
foramen is circular. The coracoid forms more of the glenoid facet
than the scapula. The sutural surface with the scapula slopes prox-
imally but is slightly convex (Fig. 11;Supplementary Data,
Fig. S11-12).
3.8.7. Shoulder girdle
The shoulder girdle of Confractosuchus closely resembles
Anteophthalmosuchus hooleyi (see Fig. 16 in (Martin Delfino and
Smith, 2016)). Anteophthalmosuchus shoulder girdle morphology
was reported to be similar to Isisfordia duncani (scapula only see
Fig. 2 in Salisbury et al. (2006) and Susisuchus anatoceps (schematic
outline, see Fig. 3 in Salisbury et al. (2003); however, the published
images of both these susisuchids were insufficient to draw such
similarities to Confractosuchus. A resemblance with Pachycheilo-
suchus trinquei (Rogers, 2003) can be established despite a slightly
different orientation in the figures and only one view supplied of
each (see Fig. 6A,B in Rogers (2003)). Much like the description
of Anteophthalmosuchus hooleyi (Martin, Delfino and Smith, 2016)
the coracoid resembles the morphology of eusuchians.
3.8.8. Forelimb
The forelimbs are mostly adducted beneath the chest cavity and
most of the elements have shifted from life position but remain on
Fig. 7. Confractosuchus sauroktonos gen. et sp. nov. cervical vertebrae and associated elements. (a) photograph; (b) 2D schematic of elements in dorsal view; (c) 3D
representation of the cervical vertebrae in dorsal aspect with associated cervical ribs (other elements removed). Digital renders of individual cervical vertebrae in dorsal
aspect (d, c3; e, c4; f, c5); ventral aspect (g, c3; h, c4; I, c5); posterior aspect (j, c3; k, c4; l, c5); anterior aspect (m, c3; n, c4; o, c5); left lateral aspect (p, c3; q, c4; r, c5).
Abbreviations: c, cervical vertebrae; cr, cervical rib; d, dentary; g, gastralia; h, humerus; o, osteoderm.
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their respective sides. Of these forelimb elements, the right ulna
and radius are the only ones that appear to be articulated. The right
manus is disarticulated on the right-hand side of the rostrum
whereas elements of the left manus are randomly dispersed
around the left shoulder girdle (Fig. 3 and Supplementary Data,
Fig. S4).
Fig. 8. Thoracic elements of Confractosuchus sauroktonos gen. et sp. nov. in (a), block containing thoracic vertebrae t1-7 and associated thoracic ribs in dorsal aspect; (b), 3D
schematic of elements in (a); (c1-5) thoracic vertebra 1; (d1-5) thoracic vertebra 2; (e1-5) thoracic vertebra 3; (f1-5) thoracic vertebra 4; (g1-5) thoracic vertebra 5; (h1-5)
thoracic vertebra 6; (i1-5) thoracic vertebra 7; (c1, d1, e1, f1, g1, h1) in anterior aspect; (c2, d2, e2, f2, g2, h2, i2) posterior aspect; (c3, d3, e3, f3, g3, h3, i3) dorsal aspect; (c4,
d4, e4, f4, g4, h4, i4) ventral aspect; (c5, d5, e5, f5, g5, h5, i5) lateral aspect. Abbreviations: prz, prezygapophysis; di, diapophysis; hp, hypapophysis; ns, neural spine; poz,
postzygapophysis; t, thoracic vertebrae; vk, ventral keel.
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3.8.9. Humerus
The right humerus is complete (10.1 cm long) whereas the left
is missing the distal end. In anterior and posterior aspects, the shaft
is straight whereas in medial and lateral views the shaft is sig-
moidal. The proximal head of the humerus is slightly offset from
the shaft. It is convex dorsally, expanded transversely and inclined
slightly medially. In dorsal aspect, the medial head is anteroposte-
riorly thicker than the lateral head. In lateral aspect, the deltopec-
toral crest is well developed with its proximal margin flat,
rounding at its anterior margin forming a tuberosity that tapers
distally, merging with shaft within the proximal half of the
element. In anterior aspect, the deltopectoral crest is offset medi-
ally. In posterior aspect, the ulnar hemicondyle is marginally
longer than the radial hemicondyle. A deep depression occupies
the distal third of the posterior ulna surface, which in distal aspect
separates the medial and lateral malleoli as a shallow groove
(Fig. 12;Supplementary Data,Fig. S13-14).
3.8.10. Ulnae
Both ulnae are partially preserved but together permit the
description of the entire element (estimated length 7.5 cm).
The proximal portion of the ulna shaft is strongly bowed relative
Fig. 9. Thoracic elements of Confractosuchus sauroktonos gen. et sp. nov. (a), block containing thoracic vertebrae t9-13 and associated thoracic ribs in dorsal aspect; (b) 3D
schematic of elements in (a); (c1-5) thoracic vertebra 9; (d1-5) thoracic vertebra 10; (e1-5) thoracic vertebra 11; (f1-5) thoracic vertebra 12; (g1-5) thoracic vertebra 13; (c1,
d1, e1, f1, g1) in anterior aspect; (c2, d2, e2, f2, g2) in posterior aspect; (c3, d3, e3, f3, g3) in dorsal aspect; (c4, d4, e4, f4, g4) in ventral aspect; (c5, d5, e5, f5, g5) in lateral
aspect. Abbreviations: t, thoracic vertebrae; r, rib.
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Fig. 10. Digital renders of the scapulae of Confractosuchus sauroktonos gen. et sp. nov. Right scapula in: (a) lateral; (b) medial; (c) anterior; (d) posterior. Left scapula in: (e)
lateral; (f) medial; (g) anterior; (h) posterior. Abbreviations: ap, acromion process; dc, deltoid crest; gf, glenoid fossa; sb, supraglenoid buttress; scs, scapula synchondrosis.
Fig. 11. Digital renders of the coracoids of Confractosuchus sauroktonos gen. et sp. nov. Right coracoid in: (a) anterior; (b) lateral; (c) posterior; (d) medial. Left coracoid in: (e)
anterior; (f) lateral; (g) posterior; (h) medial. Abbreviations: ccg, coracoid contribution to glenoid; cof, coracoid foramen.
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to the main shaft in lateral aspect. The proximal end of the ulna is
sub-circular in proximal view and expanded relative to the shaft,
with an undulating proximal surface: the olecranon process is
indistinguishable. In anterior aspect, the proximal head of the ulna
overhangs the radial facet. The shaft is ovoid in cross-section
becoming mediolaterally compressed and anteroposteriorly
expanded at its distal end (Fig. 13;Supplementary Data,Fig. S15-
16).
3.8.11. Radii
Both radii are preserved. The right is complete (6.7 cm long)
whereas the left is missing the distal one-quarter. The proximal
end is mediolaterally and, to a lesser extent, anteroposteriorly
expanded relative to the shaft. The proximal articular surface itself
is concave and ovoid in proximal view. The shaft is straight, ellip-
tical in cross-section, flaring mediolaterally at the distal end. The
distal articular surface is flat (Fig. 14;Supplementary Data,
Fig. S17-18).
3.8.12. Ulnare
The ulnare is hourglass-shaped, and strongly expanded medio-
laterally at both the proximal and distal ends. The proximal end is
hemispherical, whereas in anterior view, the distal end is boot-
shaped, projecting from the shaft more on the lateral margin. A
concavity on the distomedial margin is likely the facet for the radi-
ale. In distal aspect, the terminus is flat and tear-drop shaped,
tapering laterally (Fig. 15A-D; Supplementary Data,Fig. S19).
3.8.13. Manus
The manus elements of Confractosuchus were identified by com-
paring them with Crocodylus porosus. These comparisons were
completed digitally using scans of Crocodylus porosus that were ini-
tially used to analyse limb musculature (Klinkhamer et al., 2017).
Eight elements of the right manus and five elements from the
left have been preserved including: left and right metacarpals I
and II (Supplementary Data,Figs. S20-23), left metacarpal III (Sup-
plementary Data,Fig. S24), right metacarpal IV (?) (Supplementary
Fig. 12. Digital renders of the right and left humerus of Confractosuchus sauroktonos gen. et sp. nov. Right humerus in: (a) anterior; (b) lateral; (c) posterior; (d) medial; (e)
proximal; (f) distal. Left humerus in: (g) anterior; (h) lateral; (i) posterior; (j) medial; (k) proximal. Abbreviations: dpc, deltopectoral crest; hh, humeral head; mhp, medial
humeral process; rsr, radial supracondylar ridge; usr, ulnar supracondylar ridge.
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Data,Fig. S25), with two suspected adjoining phalanges IV-1 and
IV-2; a right ungual I-2 (Supplementary Data,Fig. S26) and a sus-
pected left phalanx IV-2 (Fig. 15).
Metacarpal I is robust with an expanded proximal end and a
weakly expanded distal end. In proximal aspect it is tear-drop
shaped, tapering laterally. A small circular facet on the proximolat-
eral surface forms the articulation with metacarpal II. In distal
aspect it appears rectangular with the lateral condyle slightly taller
than the medial. The shaft is more concave on its lateral side and is
dorsoventrally flattened. It is the broadest of the metacarpals.
Metacarpal II is longer and more gracile than metacarpal I. It is
slightly fan shaped at the proximal end with a medial projection to
receive metatarsal I. In proximal aspect it is ovoid with the anterior
margin slightly concave. In distal aspect the end is rectangular with
the anterior margin slightly concave. In relation to the proximal
end, the distal end is rotated 45°clockwise. The shaft is mostly
circular in cross section.
Metacarpal III is the longest and most gracile of the metacarpals
(Fig. 15). In anterior aspect the proximal end is fan-shaped with a
shallow circular region on its medial margin to receive metacarpal
II. In proximal aspect it is ovoid with a slightly concave posterior
margin. In distal aspect it is rectangular and, like metacarpal II,
the distal end is rotated clockwise in relation to the proximal
end, but to a less extent (30°). The shaft is mostly circular in cross
section.
Metacarpal IV (?) is the smallest of the recovered metacarpals.
In both proximal and distal aspects, it is ovoid. The shaft is circular
in cross section.
3.8.14. Pelvic girdle
The only element that is preserved of the pelvic girdle is the dis-
tal part of the left pubis. The remaining part of the shaft close to the
distal end is ovoid in cross-section. The distal blade is spatulate
with a wing-shaped, triangular lateral margin, whereas the medial
margin missing (Fig. 16,Supplementary Data,Fig. S27).
3.8.15. Femur
The only element of the hindlimb that was recovered is a partial
right femur, which is broken in two below the level of the fourth
trochanter. The distal one-third of the femur is also missing; how-
ever, enough of it is preserved to indicate the shaft was sigmoid in
lateral view. In proximal aspect the lateral margin is flat whereas
Fig. 14. Digital renders of the left and right radius of Confractosuchus sauroktonos gen. et sp. nov. Right radius in: (a) anterior; (b) posterior; (c) medial; (d) lateral; (e)
proximal; (f),distal. Left radius in: (g) posterior; (h) anterior; (i) medial; (j) lateral; (k) proximal.
Fig. 13. Digital renders of the left and right ulna of Confractosuchus sauroktonos gen. et sp. nov. Left ulna in: (a) medial; (b) lateral; (c) anterior; (d) posterior; (e) proximal; (f)
distal. Right ulna in: (g) lateral; (h) medial; (i) anterior; (j) posterior. Abbreviations: op, olecranon process; rf, radial facet.
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the medial margin bears a proximal tuberosity with a notable pro-
tuberance. The fourth trochanter is a broad, rounded ridge; how-
ever, it is poorly preserved and incomplete due to a transverse
break (diagenetic origin) in this region. More distally, the remain-
ing part of the shaft is circular in cross-section (Fig. 17;Supple-
mentary Data,Fig. S28).
3.8.16. Osteoderms
The dermal armour is entirely disarticulated. Osteoderms evi-
dently lack an anterior articulating process and, when complete,
are mostly ovoid. They are deeply pitted with a central ridge or
keel (Fig. 18); however; none of them are biserial (larger, twin-
keeled), supporting the interpretation of an entirely segmented
paravertebral shield as in Susisuchus and Isisfordia (Salisbury
et al., 2006; Figueiredo et al., 2011) but unlike Bernissartia
(Salisbury et al., 2006; Buscalioni and Sanz, 1990)(Supplementary
Data,Fig. S29). Un-keeled, mostly circular, pitted osteoderms clus-
tered on the ventral part of the neck probably formed part of the
displaced gastral shield (Fig. 3B; Supplementary Data,Fig. S30).
The fully segmented paravertebral shield, enabled greater lateral
and dorso-ventral flexion of the trunk, an adaptation for improved
aquatic locomotion (Salisbury and Frey, 2001; Molnar et al., 2015).
Larger, more primitive crocodyliforms such as goniopholids and
Fig. 15. Digital renders of the manual elements of Confractosuchus sauroktonos gen. et sp. nov. (a-q) Right manus. (r-y) Left manus. Right manus. Ulnare in: (a) anterior, (b)
medial, (c) lateral, (d) posterior views. Metacarpal I in: (e) anterior, (f) posterior views. Metacarpal II in: (g) anterior, (h) posterior aspect. Metacarpal IV(?) in: (i) anterior, (j)
posterior. Manual phalanx I-2 in: (k) anterior, (l) posterior, (m) medial, (n) lateral, (o) proximal views. Right manus in: (p), anterior; (q), posterior views. Left manus.
Metacarpal I in: (r) anterior, (s) posterior views. Metacarpal II in: (t) anterior, (u) posterior views. Metacarpal III in: (v) anterior, (w) posterior views. Left manus in: (x)
anterior, (y) posterior views. Abbreviations: car, carpal; ul, ulnare.
Fig. 16. Left pubis of Confractosuchus sauroktonos gen. et sp. nov. Left pubis in: (a)
dorsal; (b) ventral view.
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pholidosaurids that possessed amphicoelous vertebrae, were
cloaked in a closed, interlocking paravertebral shield that enabled
sustained terrestrial walking regardless of size (Salisbury and Frey,
2001; Molnar et al., 2015); however, they lacked lateral and dorso-
ventral flexion of more derived crocodyliforms.
3.9. Abdominal contents
Collectively, the ornithopod remains comprise three dorsal ver-
tebrae, two sacral centra, three distal caudal centra, both proximal
femora, left tibia, and several other elements that could not be
identified from the synchrotron data, all presumably from a single
individual (based on their relative size and non-repeating ele-
ments) (Supplementary Data,Figs. S31-34). Successive vertebrae
in each of the three main regions (dorsal, sacral, caudal) are
articulated-to-associated, although these regions are non-
contiguous (e.g. articulated sacral vertebrae are not continuous
with the articulated caudal vertebrae), suggesting connective
tissues were still intact at the time its consumer died. The two
articulated dorsal centra are spool-shaped, amphiplatyan, and
unfused to their respective neural arches. A second string of three
semi-articulated vertebra all lack their neural arches. Comparisons
with other more complete vertebral series (Galton, 1974; Salgado,
Coria and Heredia, 1997; Scheetz, 1999) indicate that these repre-
sent the last dorsal and first two sacral centra. The sacral centra are
dorsoventrally low, amphiplatyan, and strongly mediolaterally
expanded at both anterior and posterior ends forming prominent
sacral rib attachments. The sacral ribs themselves are not pre-
served. The three caudal centra are articulated and likely derive
from the distal part of the series based on anteroposteriorly elon-
gate proportions and absence of transverse processes. No caudal
neural arches are present on any of the caudal vertebrae. The lack
of fusion between the dorsal centra and their neural arches and
between the sacral centra (Galton, 1974), together with the overall
small size of the specimen, suggest a juvenile status.
Both femora are incomplete, sheared obliquely below the level
of the fourth trochanter, the right presumably as a result of oral
processing, whereas the left was the result of excavation. Despite
Fig. 17. Right femur of Confractosuchus sauroktonos gen. et sp. nov. Femur in: (a) anterior; (b) medial; (c) posterior; (d) lateral views. Abbreviation: pt, proximal tuberosity;
4 t, fourth trochanter.
Fig. 18. Dorsal osteoderms of Confractosuchus sauroktonos gen. et sp. nov. (a-c), individual osteoderms. A, scanned at 100 mm; B-C, scanned at 15 mm.
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breakage, the femur is bowed in lateral view and the pendant
fourth trochanter would have been located within the proximal
half of the element, as is typical for femora of non-iguanodontian
ornithopods (Norman et al., 2004). The femoral head is separated
from the greater trochanter by a saddle-shaped fossa trochanteris
as in some non-iguanodontian ornithopods (Han et al., 2012).
The finger-like lesser trochanter is anterolaterally situated relative
to the greater trochanter and terminates well below the level of the
greater trochanter. On the anteromedial surface of the left femur,
between the fourth trochanter and the femoral head, is a sharp-
edged, circular pit with a V-shaped cross-section, distinctive of
modern crocodylian feeding traces (‘bisected pits’) (Njau and
Blumenschine, 2006). This pit is distinct from the depression for
the m. caudofemoralis longus, which occurs at the base of and
extends onto the posterior surface of the fourth trochanter
(Fig. 19;Supplementary Fig. 4;Supplementary Data,Fig. S34).
The tibia is proportionately elongate and gracile (43 mm long,
10 mm in mid-length circumference, 8 mm in both proximal and
distal widths), which appears to be similar to the South American
ornithopod Notohypsilophodon comodorensis (see Fig. 9AinIbiricu
et al. 2014). Both of which are significantly more elongate than
Hypsilophodon (Galton, 1974), Anabisetia (Museo Municipal ‘‘Car-
men Funes”, Plaza Huincul, Neuquén, Argentina ([MCF-PVPH]
74), and most North American parksosaurids, such as Park-
sosaurus and Thescelosaurus (Galton, 1974). The gracile proportions
Fig. 19. Ornithopod elements found within the abdominal region of Confractosuchus sauroktonos. Articulated thoracic vertebrae in: (a) left lateral; (b) right lateral; (c) ventral;
(d) dorsal; (e) anterior; (f) posterior; (g) dorsal view with neural spines removed; (h) ventral view of unfused neural spines. Articulated distal caudal centra in: (i) dorsal
aspect; (j) ventral views. Semi-articulated last thoracic and first two sacral vertebrae in: (k) left lateral; (l) ventral; (m) right lateral; (n) dorsal aspects. Left femur in: (o)
lateral, (p) medial, (q) posterior, (r) anterior, (s) proximal. Right femur in: (t) lateral, (u) medial, (v) anterior, (w) posterior, (x) proximal. Right tibia in: (y) anterior, (z)
posterior. Abbreviations: g-troc, greater trochanter; l-troc, lesser trochanter; tm, tooth mark; head, femur head; 4th-troc, fourth trochanter.
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might be distinctive of this taxon but might also be a result of, or
exaggerated by its small size.
Comparably complete Australian ornithopod tibiae have yet to
be described, therefore meaningful comparisons cannot be made.
The proximal end is anteroposteriorly expanded but otherwise
poorly defined in the synchrotron scans. The distal end is mediolat-
erally expanded and spatulate, buttressed posteriorly by a medial
malleolar ridge. The medial malleolus extends below the level of
the lateral malleolus. There is no indication that the distal fibula
was fused to the tibia as it is in Albertadromeus and heterodon-
tosaurids (Galton, 1974)(Fig. 19).
4. Phylogenetic systematics
The phylogenetic analysis produced eight most parsimonious
trees of 1046 steps, and the strict consensus recovered Confracto-
suchus as an early-branching eusuchian, a sister taxon to the ances-
tor of susisuchids (Isisfordia +Susisuchus) and hylaeochampsids
(Hylaeochampsa +Iharkutosuchus +Acynodon)(Fig. 20;Supplemen-
tary Data,Fig. S35). There is only one synapomorphy (calculated
using the ‘apo’ command in TNT) diagnosing the node immediately
below Confractosuchus (Ch. 79, Maxillary teeth waves) with the
transition from state 2 (enlarged maxillary teeth curved in two
waves festooned) to state 1 (one wave of teeth enlarged). This is
an ambiguous synapomorphy as the same character state transi-
tion occurs between Calsoyasuchus and the ancestral node that it
shares with Eutretauranosuchus.
The bootstrap and jack-knife support values for the majority of
nodes within Eusuchia, including the node immediately basal to
Confractosuchus, were very low (i.e., single digit or negative Group
present/contradicted (GC) clade frequencies, see Supplementary
Data,Fig. S35). These low values indicate that there is considerable
uncertainty regarding the interrelationships of Eusuchia, including
Confractosuchus, given the present cladistic dataset. Resolving the
issue of poor nodal support in Eusuchia requires reconsideration
of character construction in crocodyliform cladistic matrices which
is beyond the scope of the present study.
5. Geometric morphometric analysis
The relative completeness of AODF 0890 enabled us to evaluate
its ecomorphology via GM analysis of its skull shape. Two cranial
morphometric datasets were used 1) the 3D dataset of Piras et al.
(2014) (Supplementary Data,Fig. 1) and 2) 2D dataset of
Drumheller & Wilberg (2019)—both of these datasets generate reli-
able indicators of feeding behaviour and diet in extant species
(Erickson et al., 2012; Walmsley et al., 2013; Piras et al., 2014;
Molnar et al., 2015; Drumheller and Wilberg, 2019)—including
extant and fossil crocodyliforms. Preference was given to the 2D
dataset, as it includes a broader taxonomic sampling of both
extinct and extant taxa (130 vs. 26 species, respectively). Further-
more, Drumheller & Wilberg’s (2019) dataset allows for a more
refined dietary categorization of Confractosuchus, as the dataset
was specifically constructed to identify such categories among
crocodyliformes. Following the standard generalized Procrustes
analysis, whereby landmark configurations were standardized (ro-
tated, translated, and scaled), a principal component analysis
revealed 87.9% of the variation along the first two principal compo-
nent axes (Table 1). As in Drumheller and Wilberg (2019), PC1
(69.9% of the variation) describes short to long snouts and, more
generally, long/narrow to short/wide crania. In comparison, PC2
(18.1% of the variation) describes wide to narrow snouts, along
with relatively small to large supratemporal fossae. Confracto-
suchus occurs within the range of macro-generalists along PC1
and PC2, but also spans brevirostrine heterodont, ziphodont, and
stenorostrine categories along PC2. Other crocodylians in close
proximity to Confractosuchus include: Theriosuchus guimarote (fos-
sil, macro-generalist, Late Jurassic), Osteolaemus osborni (extant,
generalist, Congo Dwarf Crocodile), Osteolaemus tetraspis (extant,
macro-generalist, Dwarf Crocodile), Bernissartia (fossil, generalist,
Early Cretaceous, Laurasia), Araripesuchus wegeneri (fossil, brevi-
rostrine Heterodont, Late Cretaceous).
Interestingly, Isisfordia duncani approaches the average
crocodyliform cranial shape along PC1 and PC2 (i.e., near the ori-
gin), given this dataset. Confractosuchus is well placed amid the
generalist category and on the edge of the ziphodont group, of
Fig. 20. Phylogenetic position of Confractosuchus sauroktonos gen. et sp. nov. within Eusuchia. Time-calibrated strict consensus of the 8 MPTs resulting from the analysis of
the modified matrix of Martin et al. (2020), highlighting the position of Confractosuchus sauroktonos gen. et sp. nov. within Eusuchia.
M.A. White, P.R. Bell, Nicolás E. Campione et al. Gondwana Research 106 (2022) 281–302
298
which Isisfordia could also belong, given its labiolingually-flattened
dentition (Salisbury et al., 2006). The results indicate, at minimum,
a generalist feeding lifestyle for Confractosuchus (Fig. 21).
6. Discussion
Confractosuchus is only the second extinct crocodyliform so far
discovered with identifiable abdominal contents (see also Godoy
et al., 2014) and the first to include indisputably dinosaurian
remains. The ornithopod’s estimated body mass (1.0–1.7 kg; calcu-
lated using the bipedal formula of Campione et al. (2014)) falls well
within the size range for expected prey (Njau and Blumenschine,
2006)ofConfractosuchus, which has an estimated body length of
2.5 m based on the preserved elements. Yet, despite its last meal,
Confractosuchus was likely not a dinosaur specialist. The results
of the GM analysis indicate that Confractosuchus was a macro-
generalist, and, by definition, capable of taking prey larger than
itself (Fig. 21). Like living platyrostral crocodylians (Grigg and
Kirshner, 2015), we postulate that Confractosuchus was a more
opportunistic feeder than is indicated by its abdominal contents.
The skeletal remains of an early-diverging ornithopod found
within the abdominal cavity of Confractosuchus complement the
sparse ornithopod record from the Winton Formation, which
includes footprints and a single shed tooth (Hocknull and Cook,
2008). The gracile proportions of the tibia may be an indication
that it represents a novel taxon. However, this may be a result of
its small size and/or juvenile status, and comparative elements of
other Australian early-branching ornithopods have not been
described. As it contains no clear autapomorphies, we refrain from
naming it. Unlike most iguanodontians, but in common with many
early-branching ornithopods, the femur is bowed in lateral view,
has a deep fossa trochanteris, and the fourth trochanter is pendent
and proximally positioned (Norman, 2004; Norman et al., 2004;
Butler et al. 2011; Madzia, Boyd and Mazuch, 2018). We therefore
identify it as a non-iguanodontian ornithopod.
Partial articulation and absence of acid etching indicates the
carcass had not been significantly digested. Stomach acids in mod-
ern crocodylians are among the most powerful in the animal king-
dom (Grigg and Kirshner, 2015), which, if also true of their early-
branching relatives, indicates that Confractosuchus died not long
after its last meal. This time-of-death is supported by the articula-
tion of some of the ingested vertebrae. However, whether Confrac-
tosuchus had a highly acidic gut, characteristic of living crocodiles,
remains equivocal, and its effect on ingested remains, particularly
during the earliest phases of digestion, cannot be disentangled
from short residence time in the digestive tract (Cott, 1961;
Fisher, 1981). There is, however, clear evidence of oral processing,
carcass reduction (dismemberment) and bone fragmentation of the
ornithopod carcass (Fig. 3;Supplementary Data,Fig. S4), which are
diagnostic hallmarks of modern crocodylian feeding behaviour
(Drumheller and Brochu, 2016). Crocodylians typically reduce the
size of large carcasses into more manageable components using
easily grasped body parts (such as the fore- and hindlimbs), which
are then torn free and ingested, often as entire units (Njau and
Blumenschine, 2006). Smaller prey require less reduction, enabling
the pelvic girdle and limbs to be ingested directly (Njau and
Blumenschine, 2006). This pattern of prey reduction appears
superficially congruent with the remains found in Confractosuchus.
Table 1
Results of the geometric morphometric analysis using the data from Drumheller & Wilberg (2019), showing the variance explained across the first 10 principal components.
PC1 PC2 PC3 PC4 PC5 PC6 PC7 PC8 PC9 PC10
Standard deviation 0.15 0.076 0.031 0.028 0.026 0.02 0.018 0.014 0.011 0.009
Proportion of Variance 0.699 0.181 0.03 0.025 0.022 0.013 0.01 0.006 0.004 0.003
Cumulative Proportion 0.699 0.879 0.91 0.935 0.956 0.969 0.979 0.985 0.988 0.991
Fig. 21. Comparative cranial morphospace defined by principal components (PC) 1 (69.9% of variance) and 2 (18.1% of variance). (a), Digitized landmarks of Confractosuchus
sauroktonos gen. et sp. nov. plotted amongst the data of Piras et al. (2014) as a principal component analysis (PCA) was used to visualize the ordination of the aligned
specimens. (b), Dataset is from Drumheller & Wilberg (2019), incorporating Confractosuchus here plotting just within macro-generalists (can take prey larger than
themselves) and Isisfordia, here plotting amongst generalists (can take prey equal to own body size). Abbreviations: Am, Alligator mississippiensis; As, Alligator sinensis; Ca,
Crocodylus acutus; Cc, Caiman crocodylus; Cin, Crocodylus intermedius; Cj, Crocodylus johnstoni; Cl, Caiman latirostris; Cm, Crocodylus mindorensis; Cmor, Crocodylus moreletii;
Cnil, Crocodylus niloticus; Cnov, Crocodylus novaeguineae; Coss, Crocodylus ossifragus; Cpal, Crocodylus palustris; Cpor, Crocodylus porosus; Crho, Crocodylus rhombifer; Crob, Voay
robustus; Cs, Crocodylus siamensis; Cy, Caiman yacare; Con, Confractosuchus sauroktonos; Dollo, Dollosuchoides densmorei; Gg, Gavialis gangeticus; Mcat, Mecistops cataphractus;
Mn, Melanosuchus niger; Ot, Osteolaemus tetraspis; Pp, Paleosuchus palpebrosus; Pt, Paleosuchus trigonatus; Ts, Tomistoma schlegelii. LN, longirostrine; MG, macro-generalist; G,
generalist; BR, brevirostrine.
M.A. White, P.R. Bell, Nicolás E. Campione et al. Gondwana Research 106 (2022) 281–302
299
Although it is possible that the juvenile ornithopod was scavenged,
given its small size in relation to its consumer, there is an equally
likely but currently untestable probability that it suffered a
crocodylian-style ambush feeding strategy (Njau and
Blumenschine, 2006; Gody et al., 2014). However, the abdominal
region preserving the ornithopod was badly damaged by excava-
tion equipment prior to its discovery, hindering its overall restora-
tion; it is uncertain how much of the ornithopod was initially
preserved. Post-mortem decay and disarticulation of Confracto-
suchus prior to burial may have also reduced the preservation of
the entire abdominal cavity.
The shift from Neosuchia to Eusuchia is one of the key transi-
tions in crocodyliform evolution, as it represents the onset of the
modern crocodylian bauplan (Salisbury et al., 2006; Turner and
Pritchard, 2015; Leite and Fortier, 2018) together with the adop-
tion of a strictly semi-aquatic, ambush-predator lifestyle (Gignac
and O’Brien, 2016). Historically, this transition simultaneously cen-
tred on the position and construction of the choana and the acqui-
sition of procoelous vertebrae (Salisbury et al., 2006; Turner and
Pritchard, 2015; Leite and Fortier, 2018). Interestingly, despite
the poor nodal support within Eusuchia, the position and construc-
tion of the choana (bound by palatines and pterygoids) of Confrac-
tosuchus support its phylogenetic position in relation to
Susisuchidae, which possess a pterygoid-bound choana. However,
these characters have been found to vary more widely in early-
branching eusuchians and their closest relatives (hylaeochampsids,
bernissartiids and susisuchids) (Martin et al., 2020). Despite this,
Confractosuchus is recovered within a group consisting of mostly
highly derived neosuchians and the construction of its choana
and varying vertebrae morphologies supports its phylogenetic
position.
Finally, the vertebral arrangement in Confractosuchus demon-
strates that the acquisition of procoelous vertebrae was not univer-
sally acquired. Its presence in the neck region but lack thereof in
the majority of the trunk, indicates there was likely some struc-
tural advantage to its acquisition in this region initially. Interest-
ingly, crocodyliforms with fully segmented paravertebral shields
and amphicoelous vertebrae, were small (e.g., Susisuchus), because
they lacked the structural support of a paravertebral shield that
reinforced the trunk against shear loads associated with terrestrial
locomotion (Molnar et al. 2015; Salisbury and Frey, 2001; Salisbury
et al., 2006). Furthermore, in extant crocodylians, the acquisition of
procoelous vertebrae along with horizontally-oriented zygapophy-
ses created a rigid bracing system and allowed for a more flexible
arrangement of the paravertebral shield (Salisbury and Frey 2001;
Molnar et al. 2015). This structural arrangement provided the
structural support necessary for sustained terrestrial locomotion
in all extant forms and afforded a greater range of motion concor-
dant with a semi-aquatic lifestyle (Molnar et al., 2015). If pro-
coelous vertebrae evolved to cope with increased shear loads, its
presence in the neck and lack thereof in the majority of the trunk,
indicates the neck region was initially reinforced. Therefore, we
hypothesise that these characteristics, coupled with a fully seg-
mented paravertebral shield, facilitated aquatic ambush-style
predatory behaviour by enabling greater flexibility and a strength-
ened neck region to dispatch and dismember struggling prey (Njau
and Blumenschine, 2006; Molnar et al., 2015; Fish et al., 2007),
such as juvenile dinosaurs.
Confractosuchus represents only the second Crocodyliform dis-
covered from the Winton Formation. The other, Isisfordia duncani,
comprises multiple semi-articulated and partially complete skele-
tons, and assigned isolated elements, all of which come from
potentially lower parts of the formation than Confractosuchus
(Salisbury et al., 2006; Syme & Salisbury, 2018). Isolated crocodyli-
form fossils and, more recently, traces (Poropat et al., 2021), are
quite common, having been discovered at nearly all of the AODL’s,
including over 40 teeth discovered at one locality (AODL0127).
Descriptions of these isolated elements and teeth are beyond the
scope of this publication, but their abundance indicates that
crocodyliforms were common predators of the mid-Cretaceous
freshwater fluvial and lacustrine ecosystems of the Winton
Formation.
7. Conclusion
Here, we have described a new crocodyliform, Confractosuchus
sauroktonos gen. et sp. nov., from the Winton Formation of central
Queensland Australia. Its last meal, a juvenile ornithopod dinosaur,
was discovered in its abdominal cavity. These gut contents oddly
represent the first recorded skeletal remains of ornithopods from
the Winton Formation and may represent a novel taxon. The
abdominal contents provided a unique opportunity to verify pre-
dictions of feeding behaviour, ascertained from a morphometric
analysis of the skull. The prediction of Confractosuchus as a
macro-generalist or, at the very least a generalist feeder via GM
was substantiated by the ornithopod it consumed.
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgements
We thank the Australian Age of Dinosaurs Museum staff and
volunteers for coordinating the excavation of this specimen; Bob
Elliott, Sandra Muir and Ian Muir for the specimens discovery; Judy
Chelini and Judy Elliott for the specimen preparation. We thank Dr.
Paolo Piras for his suggestions on the GMM part of this study. We
thank Dr Adam Pritchard, Dr Keegan Melstrom for reviewing initial
drafts of this manuscript. We thank the two anonymous reviewers
and Dr Joseph Meert for their constructive feedback. TNT is made
freely available thanks to a subsidy from the Willi Hennig Society.
This work was supported by a University of New England Internal
Scholarship to (MAW). The Australian Nuclear Science and Tech-
nology Organisation access grants to MAW, JJB, DAE (AS183/
IMBL/M13963) M10862, M9508, ACN/DINGO/P4371, P3977,
DB6552, IC3802). The Australian Research Council Discovery Early
Career Researcher Awards to NEC (project ID: DE190101423) and
PRB (project ID: DE170101325).
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.gr.2022.01.016.
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