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Teeth similar to those of Roxochampsa have been recognized from Brazil's Bauru Group as early as 1911, when Hermann von Ihering analyzed two isolated teeth recovered a few years prior from a well in São José do Rio Preto municipality. Von Ihering compared the teeth to those of the thalattosuchianMachimosaurus and the neosuchianGoniopholis, but due to his own uncertainty simply assigned them to the family Goniopholididae rather than any particular genus. Concurrently with von Iherings description of the isolated teeth in 1911, a second collection of fossils from the region was assembled, including additional isolated teeth. These were described in 1913 by Joviano A. Pacheco, who like van Ihering recognized similarities to the European genus Goniopholis, but unlike the former actually assigned the material to it. Both von Iherings and Pacheco's fossils were then later studied by Friedrich von Huene in 1931. In the case of the van Ihering teeth, von Huene likewise drew comparison to Machimosaurus, specifically referring one of the teeth to the species Machimosaurus hugii. Von Huene was less certain on Pacheco's identification, instead simply regarding the teeth as having come from a long-snouted mesoeucrocodylian rather than Goniopholis specifically. In 1950 Llewellyn Ivor Price called the interpretation of the supposed Machimosaurus tooth into question, arguing that the morphological difference to the other tooth described by von Ihering could be due to tooth wear. Price also cast doubt over the "Goniopholis hypothesis", though the relevant fossil has now been lost.[1]
The original material described by Roxo, including the lectotype teeth and an assigned tibia.
Description of Goniopholis paulistanus
Even more fragmentary remains were discovered through the early 1900s, including two teeth (DGM 259-R and DGM 258-R) recovered in 1935 near Amandaba city in Mirandópolis, which corresponds to the CretaceousAdamantina Formation, a partial tibia (DGM 225-R) found in a well in Valparaíso and a now missing tail vertebra. This material was described under the name Goniopholis paulistanus in 1936 by Mathias de Oliveria Roxo, who regarded this new species as a close relative to "Goniopholis" affinis. While the two teeth found in 1935 served as the syntype material, Roxo also assigned the fragmentary postcrania as well as the teeth previously described by von Ihering and Pacheco to this new species.[2]
As a consequence, various teeth of similar morphology and even some other cranial remains from the Bauru Group came to be assigned to the family Goniopholididae in the subsequent years. However, even with a formal species of Goniopholis established from South America, some authors remained suspicious of the groups presence on the continent. After Eric Buffetaut established the family Trematochampsidae in 1974, several teeth of similar morphology to those of Goniopholis paulistanus were instead referred to this family and even several more complete longirostrine taxa such as Itasuchus and Pepesuchus. However, Trematochampsidae was eventually regarded as an unnatural grouping, being centered around a chimeric taxon and including multiple ultimately unrelated forms.[1]
Revisions and reassessment
2011 saw a revision of the genus Goniopholis published by Andrade and colleagues. In this study, the team warned that though useful in recognizing broader morphotypes, tooth crowns alone are not sufficient in recognizing specific clades or even species and would require either the support of a phylogenetic framework of more substantial fossil remains. Accordingly Goniopholis paulistanus, which was named on the basis of isolated teeth, was regarded as a nomen dubium due to the absence of diagnostic features and overall scarcity of fossil material.[3][1]
Pinheiro et al. (2018) described new jaw material from the Presidente Prudente Formation of the Alfredo Marcondes municipality in São Paulo state, and noted that the tooth crowns in the jaw material morphologically matched the teeth in the syntype series of G. paulistanus. They coined the new genus name Roxochampsa for the species, designating DGM 259-R and DGM 258-R as the lectotype and paralectotype respectively, while regarding the tibia (collected at a different locality than the teeth) as having belonged to an indeterminate taxon.[1]
Etymology
The name Roxochampsa combines the Greek suffix Xαμψαι (champsa), which translates to "crocodile" and the last name of Mathias de Oliveria Roxo, who originally described the species as Goniopholis paulistanus in 1936.[1]
Description
The snout of Roxochampsa is interpreted as having been mesorostrine and platyrostral, meaning it was of moderate or "normal" length and flattened much like those of modern crocodiles. This morphology can also be found in related notosuchians like Itasuchus, Pepesuchus and Barreirosuchus. In lateral view the lower jaw shows two distinct waves that festoon the mandible, one that peaks around the level of the fourth and fifth dentary teeth and a second, shallower peak between the eight and fourteenth teeth. Conversely, the occlusal margin of the mandible performs downard slopes that reach their lowest points around the region between the fifth and ninth dentary teeth and further back between the 13th and 15th teeth. Behind these the mandible grows slightly in height, though the increase is less prominent than even Pepesuchus and Itasuchus.[1]
The symphyseal region, where the two halves of the lower jaw are conjoined, is formed by both the dentaries and splenials and about as broad as it is tall. The symphysis is moderately long as in Itasuchus and Pepesuchus and is thought to extend across nine teeth, with the dentary symphysis containing the first five and the subsequent four being positioned alongside the splenial's contribution to the element. Behind the symphysis with its straight lateral margin the mandible expands outward at a 25° angle with a convex outline, giving the entire mandible the shape of a narrow Y. Towards the back of the dentary the outer surface bears a sulcus that ends in a nutrient foramen and would have presumably extended onto the surangular, though the bone is missing in the known fossil of Roxochampsa.[1]
While most of the mandibles surface is obscured it seems to follow the general pattern seen in other mesoeucrocodylians that sees a pitted ornamentation in the front and a sulci pattern towards the rear of the lower jaw.[1]
Dentition
Based on the referred mandibular remains Roxochampsa is thought to have had 19 teeth in each hemimandible with most of them nestled in distinct alveoli formed by the dentary bone, though from the space between the 13th and 14th tooth onward the splenial forms the medial wall of the alveoli and the last two teeth are situated in an alveolar groove. This tooth is slightly higher than what has been described for Pepesuchus and Itasuchus but lower than the reported tooth count of Caririsuchus. Pinheiro and colleagues describe the distance between the individual teeth as ranging from "normal to well interspaced" throughout most the jaw. The spacing differs more significantly just behind the symphysis from the sixth to ninth dentary teeth. Both the seventh and eight are very small and essentially contiguous with the sixth and ninth respectively, forming a pair of couplets similar to what is seen in Itasuchus and Pepesuchus. The closely spaced couplets are in turned separated from another by a short diastema.[1]
The tooth size varies throughout the jaw, a condition that depending on the authorship may be referred to as moderate heterodonty, anisodonty or pseudoheterodonty. The seventh and the eight teeth are the smallest in the lower jaw and the teeth posterior to the 14th grow increasingly smaller until the end of the toothrow. Though only small parts of the fourth alveolus are preserved, Pinheiro and colleagues hypothesize that the respective tooth would have been the largest in the lower jaw, as is commonly the case in crocodylomorphs. The second biggest tooth was the 12th dentary tooth just like in Pepesuchus, while in Itasuchus its the 11th.[1]
The individual teeth are subconical and monocuspid with generally blunt and rounded tips and a circular crosssection. Between the root and the crown the teeth bear a discretely constricted neck that is not as prominent as what is seen in peirosaurids. The tooth crowns in the anterior and middle parts of the lower jaw show a degree of asymetry, with the outer (labial) surface being wider and convex while the inner (lingual) surface is narrower and ranges from concave to straight due to the tooths inward curvature. The teeth furthermore display "false ziphodonty", which means that the cutting edges of the teeth (carinae) bear crenulations, as opposed to the distinct denticles that define true ziphodonty.[1]
In addition to the crenulated main carinae the teeth of Roxochampsa are furthermore adorned by a number of irregular keels or crests formed by the enamel and the dentine. These crests extend from the base of the base of the tooth crown, where they are sometimes braided, towards the midpoint subparallel to each other, essentially functioning as secondary carinae. Some of the crests found on the anteromedial teeth are furthermore crenulated, something which is especially well developed in the enlarged 12th dentary tooth. However, Pinheiro and colleagues highlight that the crenulation of these ridges differs markedly from the crenulation observed on the primary cutting edge of the teeth, possessing coarser, more individualized crenulations. The presence of such crenulated apico-basal ridges, which lead Pinheiro and colleagues to coin the term "multicrenulated tooth", can also be observed in species of the entirely unrelated Machimosaurus, a thalattosuchian from the Late Jurassic and Early Cretaceous. The crown of the 12th dentary tooth furthermore features blunt, overlapping and hooked structures that extend from the middle of the crown through its topmost quarter before transitioning into what Pinheiro and colleagues describe as a rugose and "scaly" texture at the tooth's apex.[1]
While the upper jaw is not preserved, the occlusal pattern can be determined thanks to scars left by the dentition of the upper jaw on the lateral surface of the dentary. The scars left in Roxochampsa are described to be similar to those also seen in Itasuchus, whereas they are more subtle in Pepesuchus. Based on these, all three taxa would have had interlocking dentition similar to modern crocodiles, which is why this particular pattern is also referred to as "crocodyloid occlusion".[1]
Phylogeny
The phylogenetic position of what is now known as Roxochampsa has changed drastically across its history, having been initially placed in the neosuchian family Goniopholididae before its 2018 redescription. Pinheiro and colleagues recovered the taxon within Ziphosuchia, which the team broadly split into Notosuchia (consisting of Uruguaysuchidae, Baurusuchidae and Sphagesauridae) and Sebecia. Sebecia itself was found to consist of four families by the team, namely Sebecidae, Mahajangasuchidae, Peirosauridae and Itasuchidae. The family Itasuchidae was originally established in 2004 to include the genera Itasuchus and Malawisuchus as a sister group to Peirosauridae, but eventually fell into disuse as both forms stopped being recovered as close relatives. However, Pinheiro and colleagues recovered a clade formed by Roxochampsa, Itasuchus, Caririsuchus and Pepesuchus all within a polytomy, which they reason should bear the rehabilitated name Itasuchidae. The team specifically redefines the group as every taxon more closely related to Itasuchus than to Sebecus, Mahajangasuchus, Barreirosuchus and Montealtosuchus. In the study′s phylogenetic tree itasuchids are the sister group to a clade formed by Barreirosuchus and Ayllusuchus while Stolokrosuchus was found to be the basalmost member of this branch. Together this clade was recovered as the basalmost offshoot of Sebecia.
Also in 2018 the discovery of additional Pepesuchus remains lead to the independent creation of the clade Pepesuchinae, which was similar in its contents to Pinheiro's newly redefined Itasuchidae but placed as a subfamily of Peirosauridae.[4] Since then the contents of both families have similarily expanded, resulting in Ruiz et al. (2024) and Wilberg et al. (2025) recovering almost identical clades but under different names. The former using the name Pepesuchinae and the latter the name Itasuchidae. In both cases Roxochampsa was found to be among the most derived members of its clade, but once again appeared in a polytomy much like in the 2018 Pinheiro publication. The key difference is that in these more recent analysis Pepesuchus was recovered as just outside this grouping, while Amargasuchus is now part of the polytomy. Wilberg and colleagues furthermore provide a semi-strict consensus alternative in an attempt to resolve this polytomy, which indicates that Roxochampsa and Amargasuchus may be sister taxa.[5][6] The 2025 description of Ibirasuchus also recovers a phylogentic tree similar to those of Ruiz et al. and Wilberg et al., only differing in the presence of Ibirasuchus and absence of Sissokosuchus.[7]
↑Roxo, M.D.O. (1936). "On a new species of fossil Crocodilia from Brazil, Goniopholis paulistanus sp. n.". An. Acad. Bras. Ciênc. 8: 33–36.
↑Andrade, M.B.; Edmonds, R.; Benton, M.J.; Schouten, R. (2011). "A new Berriasian species of Goniopholis (Mesoeucrocodylia, Neosuchia) from England, and a review of the genus". Zool J Linn Soc. 163: 66–108. doi:10.1111/j.1096-3642.2011.00709.x.
↑Ruiz, Juan V.; Queiroz, Marcos V. L.; Martins, Kawan C.; Godoy, Pedro L.; Iori, Fabiano V.; Langer, Max C.; Montefeltro, Felipe C.; Bronzati, Mario (2024-08-29). "A new Peirosauridae (Crocodyliformes, Notosuchia) from the Adamantina Formation (Bauru Group, Late Cretaceous), with a revised phylogenetic analysis of Sebecia". The Anatomical Record. 308 (2): 574–597. doi:10.1002/ar.25559. hdl:11449/298094. PMID39210546.
↑Wilberg, E.; Hill, R. V.; Pascucci, T. R.; Roberts, E. M.; Bouaré, M. L.; O'Leary, M. A. (2025). "A new itasuchid (Crocodyliformes, Notosuchia) from the Early Cretaceous of Mali and the ancient Paleo-Tegama river system of Gondwana". Journal of Vertebrate Paleontology. 45 (1) e2505473. Bibcode:2025JVPal..4505473W. doi:10.1080/02724634.2025.2505473.
↑Iori, Fabiano Vidoi; Marinho, Thiago da Silva; Paschoa, Leonardo Silva; Fernandes, Renan Oliveira; Tavares, Sandra Simionato; Montefeltro, Felipe Chinaglia (2025-07-30). "Crocodyliforms of the São José do Rio Preto Formation (Bauru Basin, Upper Cretaceous), taxonomic and preservational aspects". Journal of South American Earth Sciences. 165 (in press) 105718. Bibcode:2025JSAES.16505718I. doi:10.1016/j.jsames.2025.105718.
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