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Most crocodyliforms of the Bauru Group were found in rocks of the Adamantina Formation, whereas the younger Marília Formation is almost devoid of such fossils. Here, we provide a detailed comparative description of MPMA 02–0005/87, a large skull roof found in Marília Formation deposits of the Monte Alto area, assigning it to a new crocodyliform. Despite its fragmentary nature and puzzling suit of characters, the new taxon possesses enough characters to reject its placement within Notosuchia, which is so far the only crocodyliform clade known from the Bauru Group. We tested its phylogenetic position with twodata matrices, both of which recovered the new taxon within Neosuchia and Eusuchia. Although the material does not preserve any eusuchian synapomorphy, a neosuchian affinity is supported by: anterior extension of the meatal chamber covered by the squamosal; constricted flange of the posterior process of the postorbital; poorly developed posterolateral process of squamosal. Finally, the large size estimated for the specimen, ranging from 2.98 to 5.88 metres, coupled with its possible neosuchian affinity, suggests a possible semiaquatic behaviour, an ecology rarely explored by the predominantly terrestrial crocodyliforms of the Bauru Group.
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Historical Biology
An International Journal of Paleobiology
ISSN: (Print) (Online) Journal homepage:
A large-sized mesoeucrocodylian from the Late
Cretaceous of Brazil with possible neosuchian
Thiago S. Fachini, Pedro L. Godoy, Júlio C. A. Marsola, Felipe C. Montefeltro &
Max C. Langer
To cite this article: Thiago S. Fachini, Pedro L. Godoy, Júlio C. A. Marsola, Felipe C. Montefeltro
& Max C. Langer (2022): A large-sized mesoeucrocodylian from the Late Cretaceous of Brazil with
possible neosuchian affinities, Historical Biology, DOI: 10.1080/08912963.2022.2122822
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Published online: 26 Sep 2022.
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A large-sized mesoeucrocodylian from the Late Cretaceous of Brazil with possible
neosuchian anities
Thiago S. Fachini
, Pedro L. Godoy
, Júlio C. A. Marsola
, Felipe C. Montefeltro
and Max C. Langer
Laboratório de Paleontologia de Ribeirão Preto, FFCLRP, Universidade de São Paulo, Ribeirão Preto, Brazil;
Department of Anatomical Sciences, Stony
Brook University, Stony Brook;
Departamento de Zoologia, Universidade Federal do Paraná, Curitiba, Brazil;
Universidade Tecnológica Federal do
Paraná, campus Dois VizinhosParaná, Brazil;
Laboratório de Paleontologia e Evolução de Ilha Solteira, Universidade Estadual Paulista “Júlio de Mesquita
Filho”, Ilha Solteira, Brazil
Most crocodyliforms of the Bauru Group were found in rocks of the Adamantina Formation, whereas the
younger Marília Formation is almost devoid of such fossils. Here, we provide a detailed comparative description
of MPMA 02–0005/87, a large skull roof found in Marília Formation deposits of the Monte Alto area, assigning it
to a new crocodyliform. Despite its fragmentary nature and puzzling suit of characters, the new taxon possesses
enough characters to reject its placement within Notosuchia, which is so far the only crocodyliform clade
known from the Bauru Group. We tested its phylogenetic position with twodata matrices, both of which
recovered the new taxon within Neosuchia and Eusuchia. Although the material does not preserve any
eusuchian synapomorphy, a neosuchian anity is supported by: anterior extension of the meatal chamber
covered by the squamosal; constricted ange of the posterior process of the postorbital; poorly developed
posterolateral process of squamosal. Finally, the large size estimated for the specimen, ranging from 2.98 to
5.88 metres, coupled with its possible neosuchian anity, suggests a possible semiaquatic behaviour, an
ecology rarely explored by the predominantly terrestrial crocodyliforms of the Bauru Group.
Received 10 June 2022
Accepted 2 September 2022
Notosuchia; Neosuchia;
Eusuchia; Crocodyliformes;
Bauru Group; Marília
The Bauru Group (Figure 1) is a vertebrate-rich Late Cretaceous
lithostratigraphic unit that crops-out in south-central Brazil
(Menegazzo et al. 2016; Batezelli 2017), which is famous for its extensive
record of crocodyliforms (Carvalho et al. 2010; Godoy et al. 2014;
Martinelli and Teixeira 2015). However, this diversity is currently
represented only by notosuchians (Mannion et al. 2015; Pol and
Leardi 2015), a group of predominantly terrestrial, small- to medium-
sized crocodyliforms, which are not directly linked to the extant cro-
codylians and exhibited a wide range of morphologies and ecologies
(Candeiro et al. 2006; Turner 2006; Carvalho et al. 2010; Godoy et al.
2014; Godoy et al. 2020; Nascimento 2014; Pol et al. 2014; Iori and
Arruda-Campos 2016; Marsola et al. 2016; Melstrom et al. 2019;
Montefeltro 2019; Wilberg et al. 2019; Stubbs et al. 2021). One of the
most significant fossil-bearing areas of the Bauru Group is the Monte
Alto municipality, which has already yielded five formally named
notosuchians: Caipirasuchus montealtensis, Caipirasuchus paulistanus,
Morrinhosuchus luziae, Montealtosuchus arrudacamposi, and
Barreirosuchus franciscoi (Carvalho et al. 2007; Iori and Carvalho
2009; 2011; Montefeltro et al. 2011; Iori and Garcia 2012; Iori et al.
2013; 2018).
All Monte Alto notosuchians have been recovered from rocks of
the Adamantina Formation, the age of which has been the subject of
intense debate, with high-precision U-Pb dating recently revealing
a post-Turonian maximal age of around 87.8 million years ago
(Castro et al. 2018; but see Gobbo-Rodrigues et al. 1999; Dias-Brito
et al. 2001; Menegazzo et al. 2016; Batezelli 2017 for alternative ages
based on biostratigraphy). Yet, the Monte Alto region also contains
deposits of another stratigraphic unit within the Bauru Group, the
Marília Formation (Figure 1), which is slightly younger in age, loosely
dated as Maastrichtian based on biostratigraphy, using both verte-
brates and microfossils (Dias-Brito et al. 2001; Santucci et al. 2008;
Martinelli et al. 2011; Batezelli 2017). Although outcrops of the
Marília Formation are not as common around Monte Alto as those
of the Adamantina Formation, it is surprising that they have so far
yielded almost no unambiguous crocodyliform fossils.
The only exception is the fragmentary skull roof MPMA 02–0005/
87. Given its large size and fragmentary nature, the material was initially
labelled as a partial titanosaur skull in the museum exhibition, but later
acknowledged as a fragmentary crocodyliform skull (Iori and De
Arruda-Campos 2016). According to newly proposed stratigraphic
schemes (Soares et al. 2020), this represents the only crocodyliform
known from the Marília Formation. Although breakages prevent the
complete removal of the rock matrix, the right side of the specimen is
relatively well-preserved, which allowed Iori and Arruda-Campos
(2016) to briefly describe it. Those authors compared MPMA 02–
0005/87 mostly with notosuchians, but refrained from its more precise
assignment to any crocodyliform subgroup.
In this study, we provide a detailed description of MPMA 02–0005/
87 and a full morphological comparison to a wide range of
CONTACT Thiago S. Fachini Laboratório de Paleontologia de Ribeirão Preto, FFCLRP, Universidade de São Paulo, Ribeirão Preto,
Supplemental data for this article can be accessed online at
© 2022 Informa UK Limited, trading as Taylor & Francis Group
Published online 26 Sep 2022
mesoeucrocodylians, which allowed its assignment to a new taxon. We
performed a pair of phylogenetic analyses to assess its position among
Crocodyliformes, by scoring the specimen into two comprehensive
data matrices, with the addition of some newly proposed characters.
Finally, we also estimated the total body length of the specimen,
discussing its paleoenvironmental and palaeoecological implications.
Material and methods
The crocodyliform material described here includes a partially pre-
served skull roof, with the right side of the temporal arch, posterior
portion of the orbits, right meatal chamber, and the occipital region
only incompletely present. The material was collected in 1987 and is
housed at the Museu de Paleontologia ‘Professor Antonio Celso de
Arruda Campos’ (MPMA). We used the literature and first-hand
examination of fossil specimens to conduct the morphological
comparative description. The full list of specimens analysed can
be found in the Supplementary Material.
Phylogenetic analysis
The phylogenetic position of MPMA 02–0005/87 was tested with its
inclusion in two independent morphological datasets. First, we used
the matrix of Martínez et al. (2018) with 114 taxa and 441 char-
acters, which is one of the most recent versions of the dataset
originally assembled by Pol et al. (2014). Second, we scored
MPMA 02–0005/87 into the dataset of Ruiz et al. (2021) with 101
taxa and 507 characters, an updated version of the matrix first
presented by Montefeltro et al. (2013). These datasets were chosen
because they include a significant number of notosuchians and
neosuchians, given that the affinity of the specimen within
Mesoeucrocodylia is uncertain. Furthermore, to better represent
the morphological information available for MPMA 02–0005/87
(i.e., cranial roof bones), we expanded both datasets by proposing
seven new characters (see Supplementary Material).
Maximum parsimony equally weighted phylogenetic analyses
were performed using TNT version 1.5 (Goloboff et al. 2008;
Goloboff and Catalano 2016). For each data matrix, a heuristic
search (‘Traditional Search’ in TNT) of 1,000 replicates was con-
ducted using random addition sequences (RAS), with random seed
value set to 0, followed by tree bisection and reconnection (TBR)
branch swapping and 10 trees saved per replication. Another round
of TBR was performed at the end of the replicates (i.e., trees saved in
memory) and the trees were collapsed after the searches. Most
parsimonious trees were summarised in strict consensus.
Body size estimation
The total body length of MPMA 02–0005/87 was estimated based on
comparisons with preserved cranial elements of other mesoeucroco-
dylians, followed by the application of equation to estimate total
body length of crocodyliforms. First, we roughly estimated the dorsal
skull length (DCL) of MPMA 02–0005/87, by comparing the width
of its skull roof to that of multiple crocodyliforms, given the uncer-
tain affinity of the specimen within Mesoeucrocodylia. The skull roof
width of MPMA 02–0005/87 was calculated by measuring the lateral
border of the squamosal until the midpoint of the dorsal anterior
surface of the parietal, which was subsequently multiplied by two to
obtain the total skull roof width. The taxon sampling used for
comparison prioritised specimens with skull roof width roughly
similar to that of MPMA 02–0005/87, varying between 10 and
20 cm. It includes the living crocodylians Crocodylus acutus and
Alligator mississippiensis, the notosuchians Uberabasuchus terrificus
and Stratiotosuchus maxhechti, and the neosuchian Eosuchus lerichei.
Subsequently, we used the range of DCL estimates to obtain the total
body length (TL) by applying the equations presented by Hurlburt
et al. (2003), which uses regressed data from extant crocodylian
Figure 1. Geological map of the Bauru Group in São Paulo state. The type-location of MPMA 02–0005/87 is indicated by a red dot.
species. All the measurements, equations and list of taxa used for the
body size estimation can be found in the Supplemental Material.
Institutional abbreviations
MPMA, Museu de Paleontologia ‘Professor Antonio Celso de
Arruda Campos’; LPRP/USP, Laboratório de Paleontologia da
Universidade de São Paulo, Campus Ribeirão Preto.
Systematic palaeontology
CROCODYLOMORPHA Hay, 1930 (sensu Benton and Clark
CROCODYLIFORMES Hay, 1930 (sensu Clark 1986)
MESOEUCROCODYLIA Whetstone and Whybrow 1983
Titanochampsa iorii gen. et sp. nov.
The generic name congregates the latinised Greek words ‘titan’ (=
large/brutal) and ‘champsa’ (= crocodile), in reference to the large
size of the animal and also its previous identification as a titanosaur
dinosaur. The specific epithet ‘iorii’ honours the Brazilian palaeon-
tologist Fabiano V. Iori, due to his numerous contributions to the
palaeontology of the Monte Alto region.
MPMA 02–0005/87 (Figures 2–5), a partial cranial roof including
frontal, parietal, supraoccipital, right postorbital, squamosal, quad-
rate, quadratojugal, and laterosphenoid.
Type-locality and horizon
MPMA 02–0005/87 was collected in a site located about 3.5 km
west from Monte Alto, São Paulo State (21° 16’ 28.9” S, 48° 32’ 13.4”
W; Figure 1), at an altitude of about 760 m, on the embankments of
a secondary road that gives access to the rural district of Água
Limpa. It exposes sediments of the Marília Formation, which is
composed of whitish, fine to medium, carbonated sandstones, with
frequent calcrete beds (Iori and Arruda-Campos 2016) and has
a proposed Maastrichtian age (Bertini et al. 2001; Dias-Brito et al.
2001; Martinelli et al. 2011; Batezelli 2017; Soares et al. 2020).
Titanochampsa iorii differs from all other Crocodyliformes by the
following unique set of traits (autapomorphies marked with an
asterisk): large supratemporal fenestrae, occupying over half of
the area of the skull roof; flat dorsal surface of the frontal; laterally
oriented capitate process of the laterosphenoid; anteroposterior
projection of the parietal/squamosal set with almost the same length
as the supratemporal fenestra*; dorsal end of the postorbital bar
thicker than the supratemporal squamosal bar*; rudimentary crests
on the dorsal surface of the anterior portion of the parietal; meatal
chamber anteroposteriorly narrow; upper earlid groove placed only
on the squamosal*; dorsal lamina of the frontal thicker than squa-
mosal bar; anterodorsal process of the quadratojugal dorsally over-
coming the tip of the infratemporal fenestra; dorsal, primary
quadrate head articulating with prootic and laterosphenoid; small
foramina piercing the dorsal surface of the postorbital bar.
General morphology and ornamentation
The material is composed of a partial skull roof, including most of
its right side (Figures 3–5). The squamosal, postorbital, and latero-
sphenoid are well-preserved, whereas the quadratojugal and
supraoccipital are represented only by small fragments. Despite its
incompleteness, Titanochampsa iorii bears several unique charac-
ters, which are discussed below. There are obvious signals of abra-
sion on the roof surface, but the ornamentation can still be
observed, mainly on the squamosal, at the lateral corner of the
skull. It is composed of small regularly spaced pits and faint
grooves, mostly visible on the external surface of the frontal, par-
ietal, postorbital, and squamosal (Figures 4–5). This ornamentation
differs from that observed in baurusuchids, in which it varies
between the lateral corner and the dorsal surface of the skull roof,
with larger grooves in the postorbital and squamosal compared to
those of the dorsal surface of the frontal (Carvalho et al. 2005, 2011;
Pinheiro et al. 2008; Nascimento and Zaher 2010; Montefeltro et al.
2011). The skull roof ornamentation of Titanochampsa iorii also
contrasts with that of some peirosaurids (e.g., Hamadasuchus
rebouli, Pepesuchus deiseae, Stolokrosuchus lapparenti, and
Rukwasuchus yajabalijekundu), which have more developed pits
and crenulations, as well as with that of most eusuchians (e.g.,
Gavialis gangeticus, Hylaeochampsa vectiana, Allodaposuchus pre-
cedens, Crocodylus sp., Alligator mississippiensis, Susisuchus anato-
ceps, Isisfordia duncani, Lohuecosuchus megadontos, Agaresuchus
fontisensis, Aegisuchus witmeri, Aegyptosuchus peyeri,
Pietraroiasuchus ormezzanoi and Iharkutosuchus makadii), which
have larger and deeper pits and stronger grooves.
Skull roof
In dorsal view, the temporal bar of Titanochampsa iorii is poster-
olaterally directed, as in Baurusuchus salgadoensis, Armadillosuchus
arrudai, Lohuecosuchus megadontos, Iharkutosuchus makadii,
Pietraroiasuchus ormezzanoi, Crocodylus porosus, and
Montealtosuchus arrudacamposi (Carvalho et al. 2005; Carvalho
et al. 2007; Õsi et al. 2007; Marinho and Carvalho 2009;
Buscalioni et al. 2011; Narváez et al. 2015). This differs from what
is seen in Barreirosuchus franciscoi, Hylaeochampsa vectiana,
Gavialis gangeticus, Alligator mississippiensis, Crocodylus niloticus,
Agaresuchus fontisensis, Susisuchus anatoceps, and Uberabasuchus
Figure 2. Position of the preserved skull roof of Titanochampsa iorii on
a hypothetical crocodyliform skull. Scale bar – 5 cm.
terrificus, in which the temporal bar is roughly parallel to the lateral
surface of the skull roof Holbrook 1842; Owen 1874; Salisbury et al.
2003; Carvalho et al. 2004; Iori and Garcia 2012; Narváez et al.
2016). In lateral view, the skull table of Titanochampsa iorii resem-
bles the condition seems in Aegisuchus witmeri and Aegyptosuchus
peyeri, being it dorsoventrally thick and buttressed by a robust
laterosphenoids (Holliday and Gardner 2012). The postorbital pos-
terior process and the squamosal anterior process are roughly
horizontalized, as in Barreirosuchus franciscoi, Armadillosuchus
arrudai, Hylaeochampsa vectiana, Agaresuchus fontisensis,
Osteolaemus tetraspis, and Gavialis gangeticus (Carvalho et al.
2007; Marinho and Carvalho 2009; Iori and Garcia 2012), differing
from the slightly convex outline seen in Uberabasuchus terrificus
and Baurusuchus salgadoensis (Carvalho et al. 2004; Carvalho et al.
2005) and the sinuous outline of Allodaposuchus precedens,
Lohuecosuchus megadontos, and Crocodylus spp. (Iordansky 1973;
Delfino et al. 2008; Narváez et al. 2015).
Cranial openings
The supratemporal fenestra of Titanochampsa iorii has a triangle-
shaped outline, slightly anteroposteriorly longer than laterome-
dially wide, with moderate exposure of the external supratemporal
fossa (sensu Montefeltro et al. 2011). The lateral border of the
supratemporal fenestra is slightly convex in dorsal view, whereas
its medial margin is strongly concave. Such triangle-shaped fenestra
is observed in some notosuchians, such as baurusuchids, mahajan-
gasuchids, and Armadillosuchus arrudai. The external supratem-
poral fossa is moderately wide at its anteromedial portion near the
parietal-postorbital contact. It extends until the anterolateral mar-
gin of the descending processes of the parietal (crista cranii parie-
talis), which borders the transition between the anterior and the
middle region of the dorsal lamina of the parietal, terminating near
the parietal-squamosal suture. The posterolateral surface of the
external supratemporal fossa is not anteroposteriorly wide, but
deeply concave (Figure 4). Such exposition of the external supra-
temporal fossa seems to be autapomorphic for Titanochampsa iorii.
In dorsal view, the angle formed between medial and anterior
margins of the external supratemporal fossa is approximately 90°,
as in most crocodyliforms, except for thalattosuchians (e.g.,
Dakosaurus andiniensis, Cricosaurus suevicus and Dakosaurus max-
imus), in which the angle averages 45°.
The frontals are fused, forming a partially preserved broad dorsal
horizontal lamina and two thick descending laminae. The bone
contacts the postorbitals posterolaterally via concave sutures,
which resembles those of Lohuecosuchus megadontos, Crocodylus
acutus, and Alligator mississippiensis (Martínez et al. 2018). These
sutures are morphologically variable in notosuchians, from strongly
concave, as in Hamadasuchus rebouli, baurusuchids, and
Barreirosuchus franciscoi (Carvalho et al. 2005; Carvalho et al.
2011; Larsson and Sues 2007; Pinheiro et al. 2008; Nascimento
and Zaher 2010; Montefeltro et al. 2011; Iori and Garcia 2012), to
less sinuous, as in Mahajangasuchus insignis, Armadillosuchus arru-
dai, Rukwasuchus yajabalijekundu, Pepesuchus deiseae,
Montealtosuchus arrudacamposi, and Uberabasuchus terrificus
(Carvalho et al. 2004; Carvalho et al. 2007; Turner and Buckley
2008; Marinho and Carvalho 2009; Campos et al. 2011; Sertich and
O’Connor 2014).
The posterior portion of the frontal contacts the parietal via
a near straight suture on the skull table similar to that of
Hamadasuchus rebouli (Larsson and Sues 2007), becoming
posterolaterally oriented as it approaches the external supratem-
poral fossae. Yet, the same suture in Barreirosuchus franciscoi,
Montealtosuchus arrudacamposi, Lohuecosuchus megadontos, and
Agaresuchus fontisensis is transversely oriented in relation to the
major axis of the skull, becoming straighter towards the external
supratemporal fossae (Carvalho et al. 2007; Iori and Garcia 2012).
In addition, among eusuchians, Crocodylus spp. shows a wedge-
shaped frontal-parietal suture, with Gavialis gangeticus having
a slightly convex one. Small posterior portions of the frontal of
Titanochampsa iorii enter the external supratemporal fossae, con-
tacting the parietal and postorbitals. The same is seen in
Hamadasuchus rebouli and Rukwasuchus yajabalijekundu
(Larsson and Sues 2007; Sertich and O’Connor 2014), whereas
extinct eusuchians (e.g., Pietraroiasuchus ormezzanoi,
Lohuecosuchus megadontos, Hylaeochampsa vectiana) have the pos-
terior parts of the frontal occupying a greater portion of the external
supratemporal fossae, preventing the parietal-postorbital contact
(Clark and Norell 1992; Buscalioni et al. 2011; Narváez et al. 2015).
The frontal of Titanochampsa iorii is notably thicker than that of
any other taxa analysed here (Figures 3 and 5). Its descending
lamina extends ventromedially, contacting the postorbital poster-
olaterally via a sinuous suture and the laterosphenoid via a nearly
straight suture. In the ventral portion of the descending lamina, the
crista cranii frontalis extends near the frontal-laterosphenoid
suture. The groove formed by the crista cranii frontalis encom-
passes the olfactory and optic tracts and is proportionally narrower
than that of Barreirosuchus franciscoi. The crista cranii frontalis
forms a blunt lamina, resembling those of Agaresuchus fontisensis
and Allodaposuchus precedens, whereas Barreirosuchus franciscoi,
Hamadasuchus rebouli, Pissarrachampsa sera, Montealtosuchus
arrudacamposi, Rukwasuchus yajabalijekundu, and living crocody-
lians have a sharply laminated crista cranii frontalis.
Only the anterior portion of the parietal is preserved, at the centre
of the skull roof. The recovered part includes its dorsal body and
descending laminae, which form the medial walls of the supratem-
poral fenestrae. The dorsal surface of the parietal is marked by two
longitudinal crests near its lateral borders, where the descending
laminae project ventrally. Although not as thick as in
Titanochampsa iorii, these crests are also seen in other taxa, such
as the notosuchians Barreirosuchus franciscoi, Montealtosuchus
arrudacamposi, and Uberabasuchus terrificus (Carvalho et al.
2004; Carvalho et al. 2007; Iori and Garcia 2012), and the eusu-
chians Agaresuchus fontisensis, Hylaeochampsa vectiana,
Allodaposuchus precedens, Isisfordia duncani, Pietraroiasuchus
ormezzanoi, Alligator mississippiensis, Crocodylus niloticus, and
Crocodylus porosus. Such crests of Titanochampsa iorii are some-
what similar to those of Rukwasuchus yajabalijekundu, but lacks the
sagittal crest seen in the parietal dorsal lamina of the later taxon
(Figures 4A and C) (Sertich and O’Connor 2014).
The descending laminae of the parietal enter the supratemporal
fenestrae, forming their entire anterolateral and medial portions, as
well as most of the posterior portion. The anterior most portions of
the laminae form the corners where parietal, frontal, and postorbitals
contact one another. Anterior to the corners, the parietal descending
laminae contact the descending laminae of the anterior portion of the
postorbitals via curved, anteroventrally-directed sutures. These
sutures end at the contact between the parietal, postorbitals, and
laterosphenoids. Posterior to each of these triple contacts, there is
a long and oblique posteroventral suture that separates the descend-
ing lamina of the parietal from the posterolateral lamina of the
laterosphenoid, within the supratemporal fenestra.
The posterior portion of the parietal bears an elevated and
slightly sinuous suture with the squamosal, posterior to the supra-
temporal fenestrae. Although damaged, the posterior portion of the
parietal represents more than 50% of the entire lateral extension of
the cranial roof, an autapomorphy of Titanochampsa iorii
(Figures 3B and D; Figures 4A and B). The descending laminae of
the parietal briefly overlap the dorsal primary quadrate heads.
The presence of a partial suture with the parietal, suggests that
the supraoccipital was a large element. Large supraoccipitals are
also observed in some notosuchians, such as in baurusuchids,
Araripesuchus gomesii, Montealtosuchus arrudacamposi,
Hamadasuchus rebouli, Lomasuchus palpebrosus, Pepesuchus
deiseae, and Stolokrosuchus lapparenti, as well as in the eusu-
chian Eosuchus lerichei (Gasparini et al. 1991; Delfino et al.
2005; Larsson and Sues 2007; Campos et al. 2011).
The postorbital is a triradiate bone, formed by anteromedial, pos-
terior, and descending processes. Its anteromedial and posterior
regions form the dorsal lamina of the postorbital and are relatively
robust (4 cm and 3.5 cm thick, respectively) (Figure 4). This indi-
cates a wide postorbital, even when compared to those of large taxa
such as Barreirosuchus franciscoi and Baurusuchus salgadoensis
(Carvalho et al. 2005; Iori and Garcia 2012). The posterior process
of the postorbital forms most of the lateral border of the supratem-
poral fenestra, contacting the squamosal via an irregular suture. In
lateral view, the suture is slightly curved and oblique. On the lateral
border of the supratemporal fenestra, that suture extends antero-
ventrally in a zig-zag fashion along the dorsalmost portion of the
descending process, until it contacts the dorsal primary head of the
The orbital lamina of the postorbital is formed by anterome-
dial and descending processes. The latter is short, laterally
expanded, and dorsoventrally depressed, unlike the plate des-
cending lamina (sensu Pol et al. 2014) found in all notosuchians,
including peirosaurids and mahajangasuchids (Pol et al. 2014).
As in Titanochampsa iorii, most neosuchians lack the plate
descending lamina, e.g., Agaresuchus fontisensis, Allodaposuchus
precedens, Gavialis gangeticus, Alligator mississippiensis,
Crocodylus spp., Hylaeochampsa vectiana, Lohuecosuchus mega-
dontos, and Isisfordia duncani (Iordansky 1973; Clark and Norell
1992; Delfino et al. 2008; Narváez et al. 2015; 2016). The des-
cending process of the postorbital meets the anterior tip of the
squamosal and the anterodorsal portion of the quadratojugal,
posterior to the dorsal end of the postorbital bar, but not the
anterodorsal process of the quadrate, as also observed in
Allodaposuchus precedens, Agaresuchus fontisensis, Gavialis gang-
eticus, Osteolaemus tetraspis, Tomistoma schlegelii, and
The postorbital bar is oval-shaped in cross-section and has an
anterolaterally directed small spur in its dorsal region (Figures 4–5).
This spur is also observed in Pepesuchus deiseae and some living
crocodylians, such as Gavialis gangeticus and Caimaninae
(Iordansky 1973; Campos et al. 2011), and is quite different from
the long and robust element present in dyrosaurids (de Stefano
1903; Denton et al. 1997; Jouve et al. 2006; Hastings et al. 2010).
Moreover, the anterior and medial surfaces of the postorbital bar
are flat, whereas the lateral and posterior surfaces possess irregular
outlines. In lateral view, the dorsal part of the postorbital bar bears
a moderate-sized notch, with many small foramina, which indicate
some level of vascularisation. A vascularised postorbital bar is
typical of some neosuchians, such as Theriosuchus pusillus,
Calsoyasuchus valliceps, and Sunosuchus junggarensis and eusu-
chians, such as Gavialis gangeticus, Leidyosuchus canadensis,
Crocodylus spp., and Alligator spp. The dorsal end of the postorbital
bar is oriented almost vertically, as seen in Barreirosuchus
Figure 3. Partial skull roof of Titanochampsa iorii. in anterior (A and C) and posterior (B and D) views. Broken regions of the skull represented by hatched areas. Anatomical
abbreviations: cup – cultriform process; exo – exoccipital; f – frontal; ls – laterosphenoid; lb – laterosphenoid bridge; p – parietal; po – postorbital; po b – postorbital bar;
q – quadrate; sq – squamosal; I – olfactory foramen. Scale bar – 5 cm.
franciscoi, Hamadasuchus rebouli, Pepesuchus deiseae, Baurusuchus
salgadoensis, and Gavialis gangeticus (Carvalho et al. 2005; Larsson
and Sues 2007; Campos et al. 2011; Iori and Garcia 2012), but
diverging from Caiman latirostris (LPRP/USP 0008 A), in which
it is more anterolaterally directed.
The squamosal is a triradiate bone formed by anterior, medial, and
posterior processes, the confluence of which forms a thick dorsal
body. The dorsal body and the descending processes border part of
the posterolateral margin of the supratemporal fenestra and contact
the descending lamina of the parietal via a sinuous suture. In lateral
view, the anterior descending process extends ventrally dorsal to the
quadratojugal, under the posterior portion of the postorbital, as
a tapering process that reaches the descending process of that bone
(Figure 5). This condition resembles that of Gavialis gangeticus,
differing from the vast majority of notosuchians, in which the
descending process reaches the level of the contact between the
postorbital bar and the posterior palpebral (Campos et al. 2011; Iori
and Garcia 2012; Pol et al. 2014; Sertich and O’Connor 2014).
There is a faint groove for the upper ear lid that extends across
the lateral margin of the squamosal, as seen in most extinct and
extant mesoeucrocodylians (Montefeltro et al. 2016). Intriguingly,
Titanochampsa iorii has a small notched area just anterior to the
posterior lobe of the squamosal, which is also seen in Shamosuchus
djadochtaensis (Pol et al. 2009; Turner 2015). The roof of the meatal
chamber is formed by the anterior process and the descending
lamina of the medial and posterior processes of the squamosal.
The roof is not ventrally concave as in peirosaurids, baurusuchids,
and extant crocodylians (Iordansky 1973; Carvalho et al. 2004;
2005, 2007; Larsson and Sues 2007; Pinheiro et al. 2008;
Nascimento and Zaher 2010; Sertich and O’Connor 2014). Its
ventral surface is formed entirely by the anteroventral extension
of the squamosal. The anterior process of the squamosal is hyper-
trophied and slops laterodorsally, gradually becoming horizontal at
the level of dorsal margin of the bony otic aperture.
Despite its partial preservation, the posterior descending process
of the squamosal does not seem to flares as in Rukwasuchus yaja-
balijekundu (Sertich and O’Connor 2014). Moreover, it is distally
oriented, forming a very short and shallow posterior portion of the
meatal chamber. This condition resembles that of living crocody-
lians (e.g., Crocodylus spp., Gavialis gangeticus, Alligator mississip-
piensis, Paleosuchus palpebrosus, and Tomistoma schlegelii) and
some extinct mesoeucrocodylians (e.g., Barreirosuchus franciscoi,
Shamosuchus djadochtaensis, Hylaeochampsa vectiana,
Hamadasuchus rebouli, Mahajangasuchus insignis, and
Stolokrosuchus lapparenti) (Larsson and Gado 2000; Clark and
Norell 1992; Larsson and Sues 2007; Turner and Buckley 2008;
Iori and Garcia 2012; Turner 2015). The suture between the poster-
ior descending process of the squamosal and the dorsal process of
Figure 4. Partial skull roof of Titanochampsa iorii in dorsal (A and C) and ventral (B and D) views. Broken regions of the skull represented by hatched areas. Anatomical
abbreviations: cap – capitate process; cup – cultriform process; f – frontal; ls – laterosphenoid; p – parietal; po – postorbital; q – quadrate; qj – quadratojugal; s – sediment;
sp f – supratemporal fenestra; sq – squamosal; I – olfactory foramen. Scale bar – 5 cm.
the quadrate is posteroventrally oriented, as seen in Barreirosuchus
franciscoi (Iori and Garcia 2012), whereas Caiman latirostris has
a sub-horizontal suture. There is a large foramen at the ventral
surface of the posterior descending process of the squamosal. The
shallow meatal chamber of Titanochampsa iorii is clearly seen
because the bony otic aperture is close to the lateral margin of the
dorsal lamina of the squamosal, as in Pepesuchus deiseae (Campos
et al. 2011).
The quadrate is incomplete, preserving only a partial primary head and
its anterodorsal process. In lateral view, the anterodorsal process forms
a dorsally oriented wall, anterior to the bony otic aperture, which is also
seen in Mahajangasuchus insignis, Stolokrosuchus lapparenti,
Hamadasuchus rebouli, Rukwasuchus yajabalijekundu, Pepesuchus dei-
seae, Montealtosuchus arrudacamposi, and Uberabasuchus terrificus
(Carvalho et al. 2004; Carvalho et al. 2007; Larsson and Sues 2007;
Turner and Buckley 2008; Campos et al. 2011; Sertich and O’Connor
2014). Such orientation is different from that of extant crocodylians, in
which the anterodorsal process forms a medially-sloped wall, probably
due to the dorsoventral flattening of the skull (Iordansky 1973). In this
region, the anterodorsal process of the quadrate reaches the anterior
region of the periotic fossa. The posteroventral margin of the bony otic
aperture is not preserved, but it is possible to infer that it was dorsally
directed, with an oval-shaped outline. This orientation resembles that
of Mahajangasuchus insignis, Barreirosuchus franciscoi (Iori and Garcia
2012), Hamadasuchus rebouli, Rukwasuchus yajabalijekundu,
Pepesuchus deiseae, and some extant crocodylians as Gavialis gang-
eticus and Tomistoma schlegelii (Larsson and Sues 2007; Campos et al.
2011; Sertich and O’Connor 2014). However, it differs from that of
Montealtosuchus arrudacamposi, Uberabasuchus terrificus, and baur-
usuchids, in which the aperture is anterodorsally directed (Carvalho
et al. 2004, 2005; 2007; 2011; Montefeltro et al. 2011).
The anterodorsal process of the quadrate forms the anterior, ante-
rodorsal, and ventral margins of the bony otic aperture. Because the
meatal chamber is shallow, the dorsal otic incisure of Titanochampsa
iorii is entirely exposed in lateral view. The incisure is located at the
anteromedial, ventrally extensive broad lamina. The otic buttress is
not preserved, but we infer that it met the otic incisure posteriorly. The
meatal chamber is anteroposteriorly elongated and, in its posterior
region, the suture between the descending lamina of the squamosal
and the anterodorsal process of the quadrate is oriented dorsally. The
contact between the quadrate and the squamosal occurs at the poster-
odorsal margin of the bony otic aperture, with the quadrate occupying
the whole posteroventral border of the otic aperture, as seen in
Gavialis gangeticus and Tomistoma schlegelii (Iordansky 1973).
The quadratojugal is only represented by a small fragment, which
reaches the edge of the external supratemporal fossa, buttressing the
Figure 5. Partial skull roof of Titanochampsa iorii in lateral (A and C) and ventrolateral (B and D) views. Broken regions of the skull represented by hatched areas. Anatomical
abbreviations: boa – bony otic aperture; cr cot; cotylar crest; f – frontal; ls all laterosphenoid anterolateral lamina; ls pll – laterosphenoid posterolateral lamina; po –
postorbital; po b – postorbital bar; q – quadrate; qj quadratojugal; s sediment; sf – foramen siphoneal; sp f supratemporal fenestra; sq squamosal; sq pdl
squamosal posterior descending lamina; u e g – upper earlid groove; ? – unidentified structure; I – olfactory foramen; II optic foramen; IV – trochlear foramen. Scale bar
5 cm.
anterior region of the descending lamina of the squamosal, the
anterodorsal process of the quadrate, and the posterior descending
lamina of the postorbital.
The laterosphenoid forms the anterolateral walls of the braincase,
and is divided in anterolateral and posterolateral laminae by
a cotylar crest (Figures 4B and D; Figures 5 B and D). The
anterolateral lamina extends anteroposteriorly from the cotylar
crest, buttressing the descending lamina and the posterior region
of the dorsal lamina of the frontal. The surface of the anterolateral
lamina of the laterosphenoid is notably concave, and the suture that
separates that lamina from the descending lamina of the frontal is
thick and slightly sloped ventrally. The medial tip of the anterolat-
eral lamina meets its counterpart medially, forming a ventrally
closed floor for the olfactory tract. The pair of laminae contact
one another via a broad, rough, and posteriorly directed suture,
forming the roof of the optic foramen. At its ventral most portion,
Figure 6. Resulting strict consensus cladogram illustrating the phylogenetic relations of Titanochampsa iorii and its position inside Crocodylia (modified matrix from
Martínez et al. 2018).
the laterosphenoid has a bulged area, located dorsal to the optic
foramen canal. From this bulged area a crest extends dorsoven-
trally, meeting the roof of the optic foramen. Ventrolateral to the
optic foramen, in the right anterolateral lamina, the trochlear fora-
men (IV) is found, distal to the ventral most portion of the ante-
rolateral lamina and dorsal to the oculomotor foramen (III).
Although present, the trigeminal region is badly preserved, pre-
cluding the proper assessment of its morphology. Posteriorly, the
anterolateral lamina has a capitate process that are laterally oriented
in Titanochampsa iorii, as well in Aegisuchus witmeri,
Aegyptosuchus peyeri and gavialoids.
Phylogenetic relationships
The analysis using the dataset of Martínez et al. (2018) resulted in
200,880 most parsimonious trees (MPTs) of 1,771 steps, whereas
that using the matrix of Ruiz et al. (2021) resulted in 560 MPTs of
2,318 steps. Both analyses placed Titanochampsa iorii nested within
Neosuchia, in a close relation with eusuchians (Figures 6 and 7).
The strict consensus of the first analysis, retrieved Titanochampsa
iorii nested within Crocodylia, in a polytomy at the base of
Longirostres (sensu Harshaman et al. 2003; i.e. Gavialoidea +
Crocodyloidea), along with Argochampsa krebsi, Crocodylus spp.,
Asiatosuchus germanicus, and Gavialis gangeticus +
Eothoracosaurus mississippiensis. Such arrangement is supported
by only one synapomorphy, i.e., a wide posterior half of axial neural
spine (character 258.1), which is not preserved in Titanochampsa
iorii. In some MPTs, the clade is also supported by three other
features (character 91.4, 100.0, and 71.0). However, none of these
are preserved in Titanochampsa iorii. Indeed, among the fifty char-
acters scored for Titanochampsa iorii in the dataset of Martínez
et al. (2018), few provide some clues about its affinity to Neosuchia.
These include the grooved external surface of the skull roof bones
(character 1.1–2), also seen only in Eothoracosaurus
Figure 7. Resulting strict consensus cladogram illustrating the phylogenetic relationship of Titanochampsa iorii and its position inside Eusuchia (modified matrix from Ruiz
et al. 2021).
mississippiensis; the anterolaterally facing edge of the dorsal part of
the postorbital (character 29.1), observed in all neosuchians
included in the dataset; and the anterior temporo-orbital opening
exposed in dorsal view (character 173.0), shared only with
Sarcosuchus imperator.
The second analysis – based on the dataset of Ruiz et al. (2021) –
also recovered Titanochampsa iorii within Eusuchia (Figure 7),
within a large polytomy that includes Hylaeochampsa vectiana,
Allodaposuchus precedens, Susisuchus anatoceps, Isisfordia duncani,
Lohuecosuchus megadontos, Agaresuchus fontisensis,
Pietraroiasuchus ormezzanoi, and Iharkutosuchus makadii, as well
as the three extant crocodylians included in the analysis (Gavialis
gangeticus, Crocodylus spp., and Alligator mississippiensis). Such
clustering is supported by five synapomorphies (characters 1.1,
16.2, 100.2, 108.1, and 172.1), all of which are also not preserved
in Titanochampsa iorii. Once again, very few of the sixty characters
scored for Titanochampsa iorii in the matrix of Ruiz et al. (2021)
indicate a neosuchian affinity for the taxon. The exceptions are an
ornamented external surface of the sull roof bones (character 1.1),
shared with Longirostres; and vascular openings in the dorsal sur-
face of postorbital bar (character 172.1), which represents
a neosuchian synapomorphy.
Although the results of both phylogenetic analyses unambiguously
place Titanochampsa iorii within Eusuchia, the incompleteness of
the fossil material imposes caution towards a robust assignment
even to Neosuchia. On the other hand, we are significantly more
confident on rejecting a notosuchian affinity for this taxon. This is
interesting given that the Late Cretaceous crocodyliform fauna of
Gondwana is largely dominated by notosuchians, particularly in the
Bauru Group (Godoy et al. 2014; Pol and Leardi 2015). The reasons
for rejecting a notosuchian affinity are detailed below.
Rejecting a baurusuchid anity for Titanochampsa iorii
Baurusuchids were relatively large-sized notosuchians and form the
most taxonomic diverse group of crocodyliforms in the Bauru
Group, with nine species described so far and several additional
specimens reported (Pol and Leardi 2015; Dumont et al. 2020;
Darlim et al. 2021). This justifies a tentative assignment of MPMA
02–0005/87 to the group, given that it also corresponds to a large
specimen (see below). Yet, twelve characters, found in both
matrices used here (Martínez et al. 2018; Ruiz et al. 2021), distin-
guish Titanochampsa iorii from baurusuchids, two of which repre-
sent synapomorphies of the clade: (1) the posterolateral process of
the squamosal is elongated and ventrally directed in baurusuchids,
forming an angle of approximately 90° to the skull roof, whereas it
is poorly developed in Titanochampsa iorii and in neosuchians,
projecting horizontally relative to the skull roof; (2) the dorsal
surface of the frontal in baurusuchids has a broad basin-like
depressed area bordered posteriorly by a transverse ridge, whereas
that of Titanochampsa iorii and neosuchians is flat or only slightly
depressed, lacking a transverse ridge.
The general architecture of the Titanochampsa iorii skull table is
widely divergent from the morphology of all baurusuchid species.
The small internal and enlarged external supratemporal fenestrae
(sensu Montefeltro et al. 2011) create an extensive supratemporal
fossa in baurusuchids, particularly at the posterior portion of the
skull table, which is not seen in Titanochampsa iorii. In this taxon,
the supratemporal fossa is reduced and equally developed around
all its margins. The interfenestral bar between supratemporal fenes-
trae in baurusuchids is formed by a reduced surface (about half the
width of the supratemporal fenestra), whereas in Titanochampsa
iorii the interfenestral bar is large (about the same width of the
supratemporal fenestra). In addition, the lateral margins of the
interfenestral bar in baurusuchids form hypertrophied rims for
the fenestra, whereas in Titanochampsa iorii the bar has smooth
Other characters that distinguish Titanochampsa iorii from
baurusuchids include a narrow dorsal process of the quadratojugal
that contacts only a small part of the postorbital, whereas the
process is broad in baurusuchids, with an extensive contact with
the postorbital. Additionally, the dorsal extension of the medial
surface of the quadratojugal of Titanochampsa iorii reaches the
dorsal margin of the infratemporal fenestra, whereas in baurusu-
chids it ends ventral to that. Likewise, baurusuchids and some other
notosuchians have a midline ridge on the dorsal surface of the
frontal and parietal, whereas that surface is flat in Titanochampsa
iorii, peirosaurids, and most neosuchians. The slightly grooved
ornamentation pattern seen in Titanochampsa iorii is similar to
that of the early crocodyliforms Zaraasuchus shepardi and
Gobiosuchus kielanae, as well as that of early-diverging eunotosu-
chians (sensu Ruiz et al. 2021), such as Araripesuchus gomesii,
Araripesuchus patagonicus, Pakasuchus kapilimai, and
Malawisuchus mwakasyungutiensis. This contrast with the heavily
ornamented skulls of baurusuchids, peirosaurids, and neosuchians,
with deeper pits and grooves. In addition, Titanochampsa iorii does
not present the peculiar pebbled ornamentation at the border of
external supratemporal fenestra, which has been considered
a synapomorphy of Baurusuchidae (Montefeltro et al. 2011;
Darlim et al. 2021). The quadrate has a ventrally directed major
axis in baurusuchids, whereas that axis is posteroventrally directed
in Titanochampsa iorii and most other mesoeucrocodylians.
Finally, the quadrate with a single and anteriorly placed subtympa-
nic foramen (sensu Montefeltro et al. 2016) of Titanochampsa iorii
is shared with Peirosauridae and well-distributed within Neosuchia,
whereas multiple subtympanic foramina are seen in Baurusuchidae.
In Titanochampsa iorii, as well as in Peirosauridae and
Neosuchia, the meatal chamber is covered by a straight or slightly
sinusoidal lateral margin of the squamosal. This differs from the
condition seen in most eunotosuchians, including baurusuchids,
which have a strongly convex ventral outgrowth of the squamosal,
located anterior to a small, but marked concavity at the level of the
bony otic aperture. Overall, the bony otic aperture of
Titanochampsa iorii is posteriorly closed and triangle-shaped,
with its apex directed dorsally. Such morphology is very similar to
that of neosuchians and peirosaurids, whereas the bony otic aper-
ture in Eunotosuchia, including baurusuchids, is subpolygonal to
elliptical and posteriorly open. Finally, the anterodorsal ramus of
the quadrate of Titanochampsa iorii corresponds to more than 50%
of the lateral edge of the internal supratemporal fenestra, as in the
majority of the mesoeucrocodylians, but not in Baurusuchidae.
Rejecting a peirosaurid anity for Titanochampsa iorii
Peirosaurids are also common components of the Bauru Group
fauna and, although most hypotheses place them within
Notosuchia, their possible affinity to Neosuchia (e.g., Iori et al.
2018) warrants further comparisons. A short anterior extension of
the meatal chamber is seen in Titanochampsa iorii and neosu-
chians, in which such anterior ending is represented by the squa-
mosal. This condition diverges from that of Peirosauridae, in
which the meatal chamber extends into the dorsal part of the
postorbital bar (Pol et al. 2014). In addition, the anterior limit of
the meatal chamber in peirosaurids corresponds to a concave
surface formed by the posteroventral process of the postorbital
and the anterodorsal process of quadrate and quadratojugal. This
concave surface is more restricted in longirostrine peirosaurids
such as Stolokrosuchus lapparenti and Pepesuchus deiseae (Larsson
and Gado, 2000, Campos et al. 2011), but much more developed
in other peirosaurids such as Montealtosuchus arrudacamposi,
Hamadasuchus rebouli, and Rukwasuchus yajabalijekundu
(Carvalho et al. 2007; Larsson and Sues 2007; Sertich and
O’Connor 2014). However, in Titanochampsa iorii, the meatal
chamber ends anteriorly in a reduced surface, limited ventrally
by the dorsal tip of the lateral temporal fenestra and dorsally by
the lateral shelves of the postorbital and squamosal expanding
from the skull roof. The configuration present in Titanochampsa
iorii is similar to that of eusuchians, including extant forms such
as Caiman spp. and Crocodylus spp. The poorly developed poster-
olateral process of the squamosal, which is projected horizontally
at the same level of the skull in Titanochampsa iorii, is similar to
that of eusuchians, whereas peirosaurids possess an elongated,
thin, and posteriorly directed posterolateral process. The squamo-
sal and the postorbital of Titanochampsa iorii have parallel lateral
margins, resembling the condition of Neosuchia and
Barreirosuchus franciscoi, whereas these margins diverge poster-
iorly in other peirosaurids.
Neosuchian traits of Titanochampsa iorii
Although Titanochampsa iorii does not preserve any of the syna-
pomorphies of Eusuchia and/or Crocodylia recovered in our phy-
logenetic analyses; it exhibits some features shared with members of
Neosuchia. The rectangular skull table of Titanochampsa iorii
resembles that of peirosaurids, as well as of the neosuchians
Pholidosaurus purbeckensis and Sarcosuchus imperator, whereas
baurusuchids and eusuchians have trapezoidal skull tables. The
squamosal of Titanochampsa iorii lacks a supratemporal fossa on
the lateral border of the supratemporal fenestra. This condition is
present in almost all neosuchians analysed here, except for
Crocodylus spp. and Alligator mississippiensis, diverging from
a fenestra bordered entirely by the supratemporal fossa found in
Notosuchia. Titanochampsa iorii, peirosaurids, and neosuchians
have smooth supratemporal rims, contrasting with the raised and
hypertrophied rims observed in several notosuchians, such as
Baurusuchidae, Mahajangasuchidae, Sebecidae, Simosuchus clarki,
Yacarerani boliviensis, and Caipirasuchus paulistanus (Turner and
Buckley 2008; Kley et al. 2010; Montefeltro et al. 2011; Pol et al.
2014). Finally, Titanochampsa iorii bears the supratemporal fenes-
trae occupying almost the entire area of the supratemporal fossa, as
also seen in Pholidosaurus purbeckensis, Eosuchus minor,
Argochampsa krebsi, and Gavialis gangeticus, whereas most noto-
suchians have small, anterolaterally oriented supratemporal
In this context, the recent description of Burkesuchus mallin-
grandensis (Novas et al. 2021), a possible neosuchian from the
Late Jurassic of Chile, represents an interesting base for compar-
ison with Titanochampsa iorii, given that both South American
taxa have a somehow ambiguous taxonomy. Both specimens are
fragmentary, but there is important anatomical overlap between
them. Specifically, although both Titanochampsa iorii and
Burkesuchus mallingrandensis preserve most of their cranial
roofs, they only share two conspicuous features: a rod-like des-
cending process of the postorbital; and a single subtympanic fora-
men. On the other hand, Burkesuchus mallingrandensis differs
from Titanochampsa iorii by possessing a heavily ornamented
skull roof, a frontal bearing a longitudinal ridge (which is also
present in some notosuchians and neosuchians), small supratem-
poral fenestrae and foramina (shared with most notosuchians);
a squamosal strongly flexed posteroventrally, forming an
expanded wing that partially covers the meatal chamber, in addi-
tion to an external auditory meatus, deeply sunk and mostly
covered laterally by the wing of the squamosal (also observed in
eunotosuchians). Therefore, even though Burkesuchus mallingran-
densis was not included along with Titanochampsa iorii in our
phylogenetic analyses, the many differences between these two
South American early neosuchians would likely imply in different
positions in the mesoeucrocodylian tree.
Body size of Titanochampsa iorii and its palaeobiological
After comparisons with other mesoeucrocodylians, we coarsely
estimated the dorsal cranial length (DCL) of Titanochampsa iorii
to be constrained between 37.01 and 74.43 cm. Given the significant
difference between the higher and upper limits of this estimation,
we did not use the mean value of DCL to apply the equations of
Hurlburt et al. (2003), and instead used maximum and minimum
DCL values. This resulted in a total body length (TL) of
Titanochampsa iorii ranging from 2.98 to 5.88 metres.
Even though we do not expect our body size estimation to be
very accurate, given the fragmentary nature of MPMA 02–0005/87
and the varied body proportions of different crocodyliform sub-
groups, these results suggest that Titanochampsa iorii possibly
surpassed three metres in total body length. Baurusuchids were
the notosuchian apex predators of the Bauru Group (Riff and
Kellner 2011; Godoy et al. 2014; Bandeira et al. 2018; Montefeltro
et al. 2020), ranging from about two to four metres in total length,
they represent some of the largest crocodylomorphs with a fully
terrestrial lifestyle (Godoy et al. 2014; 2016; 2019). In comparison,
the aforementioned total body length range recovered to the
Titanochampsa iorii, place it in the large-size end of the spectrum
of body size variation seen among the Bauru Group mesoeucroco-
dylians and of terrestrial crocodylomorphs in general (Godoy et al.
However, the comparative morphology of Titanochampsa iorii,
as well as our phylogenetic results, suggests a closer relation to
neosuchians, which are predominantly semiaquatic/freshwater cro-
codyliforms (Wilberg et al. 2019). As other stratigraphic units of the
Bauru Group, the lithology of the Marília Formation suggests
a fluvial depositional environment, in semiarid context (Garcia
et al. 2005; Basilici et al. 2016; Mineiro et al. 2017; Batezelli 2019;
Soares et al. 2020). Therefore, a semiaquatic lifestyle cannot be ruled
out for Titanochampsa iorii. In this case, the size of this taxon would
be compatible with that of medium-sized aquatic crocodylomorphs,
which are consistently larger than their terrestrial counterparts, due
to physiological constraints (Godoy et al. 2019; Gearty and Payne
2020; Godoy and Turner 2020).
Paleoenvironmental and ecological implications of
Titanochampsa iorii
In a recent study of Soares et al. (2020), the former Serra da Galga
and Ponte Alta Member of the Marília Formation were elevated to
the Formation rank. Those authors argue that the Serra da Galga
Formation was deposited in proximal-medial distributive fluvial
systems (Basilici et al. 2016; Mineiro et al. 2017; Soares et al.
2020), whereas the Echaporã Member of the Marília Formation
(which yielded Titanochampsa iorii) represents the distal portion
of such systems, with occasional unconfined flows, in a semiarid to
arid environment with well-drained periods. Such environmental
differences would also be evidenced by the fossil record, with the
Serra da Galga Formation revealing a vast diversity of invertebrates
and vertebrates, including several notosuchian crocodyliforms
(Carvalho et al. 2004; Campos et al. 2005; Kellner et al. 2005;
2011; Novas et al. 2005; 2008; Salgado and Carvalho 2008; Báez
et al. 2012; Martinelli et al. 2013; Martinelli and Teixeira 2015) and
the Marília Formation yielding much fewer fossils (Bertini et al.
2001; Méndez et al. 2014; Iori and De Arruda-Campos 2016;
Mineiro et al. 2017). Among these, Titanochampsa iorii is the first
crocodyliform described for the Marília Formation, as redefined by
Soares et al. (2020).
The discovery of Titanochampsa iorii in deposits of the
Echaporã Member suggests that this taxon, with possible neosu-
chian affinities, would inhabit an arid to semiarid environment,
where ephemeral water bodies were common. Its large internal
supratemporal fenestra indicates the presence of bulk adductor
muscles of the lower jaw (Busbey 1989), suggesting a strong bite
(Iordansky 1964; Walmsley et al. 2013). In contrast, most noto-
suchians have smaller internal supratemporal fenestrae, which
might help explaining the surprisingly weak bite estimated for
baurusuchids (Montefeltro et al. 2020). Both the large size of
Titanochampsa iorii and its inferred strong bite are compatible
with an amphibian lifestyle, including ambushing behaviour, as
seen in most crocodiles nowadays and matching its possible affi-
nity to Eusuchia. This inferred behaviour strongly departs from
that of most crocodilians recorded in the older Adamantina
Formation, which are predominantly terrestrial, with more diverse
feeding habits. Although the record of a single specimen provides
no strong basis for bold statements, the prevalence of crocodilians
such as Titanochampsa iorii may be an outcome of the increase in
humidity seen in the last phases of the Bauru Basin deposition,
which includes the Echaporã Member (Fernandes and Ribeiro
The comparative description of Titanochampsa iorii reveals its
uniqueness among mesoeucrocodylians, differing from notosu-
chians by lacking typical traits of the group, such as a meatal
chamber closed anteriorly by a flange of the posterior process of
the postorbital and posteriorly by the ventrally deflected lateral
margin of the squamosal. Our phylogenetic analyses recover
Titanochampsa iorii nested within Neosuchia, although almost
all key-features of the group are not preserved in the rather
incomplete specimen. Nevertheless, the skull roof of
Titanochampsa iorii resembles that of neosuchians by the ante-
rior extension of the meatal chamber covered by the squamosal,
the constricted flange of the posterior process of the postorbital,
and the poorly developed posterolateral process of squamosal.
Perhaps most importantly, the material is well-preserved enough
to confidently rule out its inclusion within Baurusuchidae, and
less clearly within Peirosauridae. The more than three metres
long Titanochampsa iorii is the only crocodyliform presently
known for the Marília Formation and its inferred ecology
matches the climatic conditions prevalent at the time.
We thank both Dr. Sandra Tavares, curator of the “Museu de Paleontologia Prof.
Antonio Celso de Arruda Campos”, and Dr. Fabiano Iori for the loan of the
specimen. TSF was supported by the Conselho Nacional de Desenvolvimento
Científico e Tecnológico (CNPq grant number 165031/2018-2). PLG was supported
by the National Science Foundation (NSF DEB 1754596). JCAM and PLG were
supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
(CAPES grant numbers 8887.572782/2020-00 and 88887.583087/2020-00). JCAM
and MCL were supported by the São Paulo Research Foundation (FAPESP grant
numbers 2021/1456-4 and 2020/07997-4). FCM was supported by Program 162
(Projetos De Cooperação em Pesquisa Entre o Brasil e a Alemanha - CAPES/DAAD
-PROBRAL). TNT is made freely available through the Willi Henning Society.
Disclosure statement
No potential conflict of interest was reported by the authors.
This work was supported by the Conselho Nacional de Desenvolvimento
Científico e Tecnológico (CNPq 165031/2018-2), National Science Foundation
(NSF DEB 1754596), Coordenação de Aperfeiçoamento de Pessoal de Nível
Superior (CAPES 8887.572782/2020-00 and 88887.583087/2020-00), and São
Paulo Research Foundation (FAPESP 2021/1456-4 and 2020/07997-4).
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We describe the basal mesoeucrocodylian Burkesuchus mallingrandensis nov. gen. et sp., from th Upper Jurassic (Tithonian) Toqui Formation of southern Chile. The new taxon constitutes one of the few records of non-pelagic Jurassic crocodyliforms for the entire South American continent. Burkesuchus was found on the same levels that yielded titanosauriform and diplodocoid sauropods and the herbivore theropod Chilesaurus diegosuarezi, thus expanding the taxonomic composition of currently poorly known Jurassic reptilian faunas from Patagonia. Burkesuchus was a small-sized crocodyliform (estimated length 70 cm), with a cranium that is dorsoventrally depressed and transversely wide posteriorly and distinguished by a posteroventrally fexed wing-like squamosal. A well-defned longitudinal groove runs along the lateral edge of the postorbital and squamosal, indicative of a anteroposteriorly extensive upper earlid. Phylogenetic analysis supports Burkesuchus as a basal member of Mesoeucrocodylia. This new discovery expands the meagre record of non-pelagic representatives of this clade for the Jurassic Period, and together with Batrachomimus, from Upper Jurassic beds of Brazil, supports the idea that South America represented a cradle for the evolution of derived crocodyliforms during the Late Jurassic.
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Sphagesauridae is a group of notosuchian crocodyliforms from the Late Cretaceous of South America characterized by highly specialized jaws and dentition. Here, we describe a new sphagesaurid from the Santo Anastácio Formation (Caiuá Group, Bauru Basin), south-east Brazil. The specimen is composed of a partial palate, neurocranium, mandible and fragmentary teeth. It represents a new species that can be assigned to Caipirasuchus due to the presence of a lateromedially narrow and anteroposteriorly long mandibular symphyseal region, apicobasal ridges on the posterior teeth, a diastema between D5 and D6, and a linear row of large neurovascular foramina on the lateral surface of the dentary. It differs from previously described Caipirasuchus species based on a ventrolaterally inclined surface of the dentaries posterior to the tooth row, a connection between the anteroventral margin of the external mandibular fenestra and the floor of the Meckelian canal, and the anterior process of the angular forming a ‘V’-shaped suture in its contact with the splenial. The results of a phylogenetic analysis of notosuchians recovered the so-called ‘advanced notosuchians’ in a clade, for which we propose a phylogenetic definition and erect the name Sphagesauria. We also recovered two more inclusive clades encompassing an array of Mesozoic notosuchians, here named Xenodontosuchia, which includes Sphagesauria + Baurusuchia, and Eunotosuchia, including Xenodontosuchia, Uruguaysuchidae and other Cretaceous forms.
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Baurusuchidae is one of the most diverse groups of South American notosuchians, unambiguously recorded in Late Cretaceous deposits of Brazil and Argentina. The group is characterized by a reduced tooth formula, a lateromedially compressed rostrum, and a verticalized quadrate, representing one of the top predators of their faunas. Historically, skull morphology is the most employed tool to investigate the relationships of baurusuchids, as most of the species have been primarily based on cranial remains. The present study describes a new baurusuchid species from the Bauru Basin of Brazil, based on the first tridimensional digital reconstruction of individualized skull bones for Notosuchia, and discusses its phylogenetic position within the group. The new species differs from all the other known baurusuchids by a depression on the posterior portion of the nasal bearing a crest, an infraorbital crest of the jugal that extends until the anterior margin of the lacrimal, the dorsal surface of the frontal lacking a longitudinal crest or depression, and the lateral convexity of the squamosal prongs participating in the occipital wall. The new taxon is consistently positioned as sister to the remaining baurusuchines, with Aplestosuchus sordidus and Stratiotosuchus maxhechti, as successive sister‐taxa to a monophyletic Baurusuchus (Ba. albertoi, Ba. Salgadoensis, and Ba. pachecoi). Our updated phylogenetic analysis helps to differentiate the two major Baurusuchidae lineages, Baurusuchinae and Pissarrachampsinae. Yet, the new species shares morphological features with both groups, suggesting the occurrence of “Zones of Variability” in the radiation of Baurusuchidae.
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Understanding the origin, expansion and loss of biodiversity is fundamental to evolutionary biology. The approximately 26 living species of crocodylomorphs (crocodiles, caimans, alligators and gharials) represent just a snapshot of the group's rich 230-million-year history, whereas the fossil record reveals a hidden past of great diversity and innovation, including ocean and land-dwelling forms, herbivores, omnivores and apex predators. In this macroevolutionary study of skull and jaw shape disparity, we show that crocodylomorph ecomorphological variation peaked in the Cretaceous, before declining in the Cenozoic, and the rise and fall of disparity was associated with great heterogeneity in evolutionary rates. Taxonomically diverse and ecologically divergent Mesozoic crocodylomorphs, like marine thalattosuchians and terrestrial notosuchians, rapidly evolved novel skull and jaw morphologies to fill specialized adaptive zones. Disparity in semi-aquatic predatory crocodylians, the only living crocodylomorph representatives, accumulated steadily, and they evolved more slowly for most of the last 80 million years, but despite their conservatism there is no evidence for long-term evolutionary stagnation. These complex evolutionary dynamics reflect ecological opportunities, that were readily exploited by some Mesozoic crocodylomorphs but more limited in Cenozoic crocodylians.
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The Bauru Basin of SE Brazil is a large (ca. 370,000 km2) Upper Cretaceous intracratonic feature, important for its fossil remains and of particular value as a source of regional palaeoclimatic information. Historically, lithostratigraphic reconstructions have been performed mainly for successions of the central and southern parts of the basin, resulting in a lithostratigraphic scheme that is not applicable to the northernmost regions. In particular, the northeastern deposits of the Marília Formation (Serra da Galga and Ponte Alta members) reveal lithological, stratigraphic, and palaeontological differences from southeastern and northwestern counterparts (Echapor~a Member). Nevertheless, these deposits are considered as a single lithostratigraphic formation in the literature. To address this problem, this study demonstrates how the northeastern deposits of the Marília Formation do not show affinity to the rest of the unit. A more suitable lithostratigraphic model is proposed for the northeastern succession as a distinct and independent unit. Lithofacies and palaeopedological analysis, combined with lithostratigraphic mapping of the northeastern deposits, reveal 11 distinct lithofacies and three pedotypes over an area of _450 km2. Sedimentary facies and pedotypes were assigned to six interbedded architectural elements: (a) type 1 channel fill, (b) type 2 channel fill, (c) type 3 channel fill, (d) interchannels, (e) palaeosols, and (f) calcrete beds. The succession is interpreted as a distributive fluvial system with overall direction of flow to the NNW, and which developed under the influence of a semiarid climate regime. This contrasts with deposits of the southeastern and northwestern Marília Formation, previously suggested to be of fine-grained aeolian affinity with interbedded poorly channelised deposits assigned to an aeolian sand sheet environment. By revising the existing lithostratigraphic scheme for the northeastern deposits, and contrasting them with laterally equivalent strata, this work demonstrates how the previously named Serra da Galga and Ponte Alta members reveal a unique set of lithological, architectural, and genetic signatures that permits to separate them from the Marília Formation. Finally, a new lithostratigraphic classification for the unit is proposed: the Serra da Galga Formation, whose deposition relates to an ancient distributive fluvial system.
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Theropod dinosaurs were relatively scarce in the Late Cretaceous ecosystems of southeast Brazil. Instead, hypercarnivorous crocodyliforms known as baurusuchids were abundant and probably occupied the ecological role of apex predators. Baurusuchids exhibited a series of morphological adaptations hypothesized to be associated with this ecological role, but quantitative biomechanical analyses of their morphology have so far been lacking. Here, we employ a biomechanical modelling approach, applying finite element analysis (FEA) to models of the skull and mandibles of a baurusuchid specimen. This allows us to characterize the craniomandibular apparatus of baurusuchids, as well as to compare the functional morphology of the group with that of other archosaurian carnivores, such as theropods and crocodylians. Our results support the ecological role of baurusuchids as specialized apex predators in the continental Late Cretaceous ecosystems of South America. With a relatively weak bite force (~600 N), the predation strategies of baurusuchids likely relied on other morphological specializations, such as ziphodont dentition and strong cervical musculature. Comparative assessments of the stress distribution and magnitude of scaled models of other predators (the theropod Allosaurus fragilis and the living crocodylian Alligator mississippiensis) consistently show different responses to loadings under the same functional scenarios, suggesting distinct predatory behaviors for these animals. The unique selective pressures in the arid to semi-arid Late Cretaceous ecosystems of southeast Brazil, which were dominated by crocodyliforms, possibly drove the emergence and evolution of the biomechanical features seen in baurusuchids, which are distinct from those previously reported for other predatory taxa.
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Background: Little is known about the long-term patterns of body size evolution in Crocodylomorpha, the > 200-million-year-old group that includes living crocodylians and their extinct relatives. Extant crocodylians are mostly large-bodied (3-7 m) predators. However, extinct crocodylomorphs exhibit a wider range of phenotypes, and many of the earliest taxa were much smaller (< 1.2 m). This suggests a pattern of size increase through time that could be caused by multi-lineage evolutionary trends of size increase or by selective extinction of small-bodied species. Here, we characterise patterns of crocodylomorph body size evolution using a model fitting-approach (with cranial measurements serving as proxies). We also estimate body size disparity through time and quantitatively test hypotheses of biotic and abiotic factors as potential drivers of crocodylomorph body size evolution. Results: Crocodylomorphs reached an early peak in body size disparity during the Late Jurassic, and underwent an essentially continual decline since then. A multi-peak Ornstein-Uhlenbeck model outperforms all other evolutionary models fitted to our data (including both uniform and non-uniform), indicating that the macroevolutionary dynamics of crocodylomorph body size are better described within the concept of an adaptive landscape, with most body size variation emerging after shifts to new macroevolutionary regimes (analogous to adaptive zones). We did not find support for a consistent evolutionary trend towards larger sizes among lineages (i.e., Cope's rule), or strong correlations of body size with climate. Instead, the intermediate to large body sizes of some crocodylomorphs are better explained by group-specific adaptations. In particular, the evolution of a more aquatic lifestyle (especially marine) correlates with increases in average body size, though not without exceptions. Conclusions: Shifts between macroevolutionary regimes provide a better explanation of crocodylomorph body size evolution on large phylogenetic and temporal scales, suggesting a central role for lineage-specific adaptations rather than climatic forcing. Shifts leading to larger body sizes occurred in most aquatic and semi-aquatic groups. This, combined with extinctions of groups occupying smaller body size regimes (particularly during the Late Cretaceous and Cenozoic), gave rise to the upward-shifted body size distribution of extant crocodylomorphs compared to their smaller-bodied terrestrial ancestors.
Knowledge on crocodyliform paleoneurology has significantly improved with development of computed tomography. However, studies so far have been able to reconstruct brain endocasts based only on single specimens for each taxon. Here for the first time, we reconstructed brain endocasts for multiple fossil specimens of the same crocodyliform taxon (Baurusuchus), consisting of complete skulls of two medium sized specimens, one large adult, and a late juvenile. In addition, we were able to reconstruct the inner ear anatomy of a fragmentary skull using microtomography. We present estimates of brain size using simple models, based on modern Crocodylia, able to adapt brain to endocranial cavity ratios to expected ontogenetic variation instead of using fixed ratios. We also analyzed relative brain sizes, olfactory ratios, facial sensation, alert head posture, best hearing frequencies, and hearing range. The calculated endocranial volumes showed that they can be greatly altered by taphonomic processes, altering both total and partial endocranial volumes. Reconstructed endocasts are compatible with different degrees of occupation along the endocranial cavity and some of their characteristics might be useful as phylogenetic characters. The relative brain size of Baurusuchus seems to be small in comparison to modern crocodilians. Sensorial abilities were somewhat similar to modern crocodilians and hearing ranges and best mean frequencies remarkably similar to modern taxa, whereas olfactory ratio values are a little higher. Differing from its modern relatives, Baurusuchus hypothesized alert head posture is compatible with a terrestrial habit.
Crocodylians are currently facing evolutionary decline. This is evinced by the rich fossil record of their extinct relatives, crocodylomorphs, which show not only significantly higher levels of biodiversity in the past but also remarkable morphological disparity and higher ecological diversity. In terms of body size, crocodylians are mostly large animals (>2m), especially when compared to other extant reptiles. In contrast, extinct crocodylomorphs exhibited a 10-fold range in body sizes, with early terrestrial forms often quite small. Recent research has shed new light on the tempo and mode of crocodylomorph body size evolution, demonstrating a close relationship with ecology, in which physiological constraints contribute to the larger sizes of marine species. Abiotic environmental factors can also play an important role within individual subgroups. Crocodylians, for instance, have been experiencing an average size increase during Cenozoic, which seems to be related to a long-term process of global cooling.
At least twenty‐six species of crocodylian populate the globe today, but this richness represents a minute fraction of the diversity and disparity of Crocodyliformes. Fossil forms are far more varied, spanning from erect, fully terrestrial species to flippered, fully marine species. To quantify the influence of a marine habitat on the directionality, rate, and variance of evolution of body size in Crocodyliformes and thereby identify underlying selective pressures, we compiled a database of body sizes for 264 fossil and modern species of crocodyliform covering terrestrial, semi‐aquatic, and marine habitats. We find increases in body size coupled with increases in strength of selection and decreases in variance following invasions of marine habitats but not of semi‐aquatic habitats. A model combining constraints from thermoregulation and lung capacity provides a physiological explanation for the larger minimum and average sizes of marine species. It appears that constraints on maximum size are shared across Crocodyliformes, perhaps through factors such as the allometric scaling of feeding rate versus basal metabolism with body size. These findings suggest that broad‐scale patterns of body size evolution and the shapes of body size distributions within higher taxa are often determined more by physiological constraints than by ecological interactions or environmental fluctuations. This article is protected by copyright. All rights reserved