Baurusuchidae

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Baurusuchids
Temporal range:
Ma
Skull of Baurusuchus salgadoensis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Clade: Crocodyliformes
Suborder: †Notosuchia
Clade: †Sebecosuchia
Branch: †Baurusuchia
Warren, 1968
Family: †Baurusuchidae
Price, 1945
Genera

Baurusuchidae is a

subfamilies have been proposed: Baurusuchinae and Pissarrachampsinae
.

Genera

Several genera have been assigned to Baurusuchidae. Baurusuchus was the first, being the namesake of the family. Remains of Baurusuchus have been found from the Late Cretaceous Bauru Group of Brazil in deposits that are Turonian - Santonian in age.[3] In addition to Baurusuchus, five other South American crocodyliforms have been assigned to Baurusuchidae: Campinasuchus, Cynodontosuchus, Pissarrachampsa, Stratiotosuchus, and Wargosuchus. Cynodontosuchus was the first known baurusuchid, named in 1896 by English paleontologist Arthur Smith Woodward, although it was only recently assigned to Baurusuchidae.[4] Wargosuchus was described in 2008.[5] Cynodontosuchus and Wargosuchus are known only from fragmentary remains. Both genera are from the Santonian of Argentina.

Skull of Pissarrachampsa.

A fourth genus, Stratiotosuchus, was assigned to Baurusuchidae in 2001. Pabwehshi is the youngest genus that has been assigned to Baurusuchidae, and is from the Maastrichtian of Pakistan.[6] It was named in 2001 but has since been reassigned as a basal member of Sebecia.[7]

A new genus, Campinasuchus, was assigned to the family in May, 2011. It is known from the Turonian-Santonian Adamantina Formation of the Bauru Basin of Brazil.[8] Soon after, the new genus Pissarrachampsa was named from the Campanian–Maastrichtian Vale do Rio do Peixe Formation, also in the Bauru Basin.

Phylogeny

The family Baurusuchidae was named by

Edwin Harris Colbert erected the group Sebecosuchia, which united Baurusuchidae with the family Sebecidae (represented by the genus Sebecus).[10] Both Baurusuchus and Sebecus have deep snouts and ziphodont dentitions (teeth that are serrated and laterally compressed).[11] Other forms were later found that had a close appearance to these two genera, among them Cynodontosuchus, Stratiotosuchus, and Wargosuchus. Several features were used to unite these groups: a deep snout, a ziphodont dentition, a curved tooth row, an enlarged canine-like dentary tooth that fits into a deep notch in the upper jaw, and a groove on the lower jaw.[12]

Many

derived members of the clade. Below is a modified cladogram from Ortega et al. (2000) placing baurusuchids within Notosuchia:[15]

Notosuchia      Baurusuchids

In 2004, the superfamily

Baurusuchoidea was established to include baurusuchids and sebecids. Phylogenetically, Baurusuchoidea was defined as the most recent common ancestor of Baurusuchus and Sebecus and all of its descendants while Baurusuchidae was defined as the most recent common ancestor of Baurusuchus and Stratiotosuchus and all of its descendants.[16]

In a 2005 analysis, Sebecidae was found to be a

paraphyletic grouping, or a grouping that includes some descendants of a common ancestor but not all. Sebecids formed an assemblage of basal sebecosuchians, while baurusuchids remained a valid grouping of derived sebecosuchians. Below is a modified cladogram from Turner and Calvo (2005):[17]

 Metasuchia 

Later studies noted many features that distinguished baurusuchids from sebecosuchids. Sebecosuchids were often considered to be more closely related to

crocodylians, while baurusuchids were thought to be a more distantly related clade.[18] In a 1999 phylogenetic analysis, Baurusuchus formed a clade with notosuchians to the exclusion of other ziphosuchians.[19] This placement has been upheld by recent analyses, which place Baurusuchus within Notosuchia.[20]

In 2007, a new clade called Sebecia was erected.[7] Sebecia included sebecids and peirosaurids. Peirosauridae, a family of small terrestrial crocodyliforms, had often been placed in or near Neosuchia in previous studies. The assignment of sebecids to Sebecia placed the family closer to Neosuchia than Notosuchia. In this study, baurusuchids were split up, with Baurusuchus placed as a more basal metasuchian and the remaining baurusuchids (Bretesuchus and Pabwehshi) placed as sebecians. Therefore, the family Baurusuchidae was paraphyletic. Below is a modified cladogram from Larsson and Sues (2007):[7]

Metasuchia      Baurusuchids

More recent studies have nested Baurusuchus deep within Notosuchia, just as the larger group Sebecosuchia once was, while the remaining sebecosuchian genera have been placed more distantly in Metasuchia.

Crocodylus niloticus.[2]

In contrast to the node-based Baurusuchidae, the stem-based Baurusuchia does not include a common ancestor and all its descendants, but rather all forms more closely related to a specific baurusuchid than a non-baurusuchid. As a stem-based taxon, Baurusuchia is more inclusive than Baurusuchidae; a new taxon could potentially be placed outside Baurusuchidae because it is not a descendant of the most recent common ancestor of baurusuchids, but would still be a baurusuchian because it is more closely related to baurusuchids than it is to other crocodyliforms. For now, however, Baurusuchidae and Baurusuchia are almost identical in scope, with Baurusuchia also including Pabwehshi, based on their reference phylogenies.[12] Other analyses however, have recovered additional taxa within Baurusuchia outside of Baurusuchidae. (Pakasuchus and Comahuesuchus)[21]

Montefeltro et al. (2011) also divided Baurusuchidae into two subfamilies, Pissarrachampsinae and Baurusuchinae. Pissarrachampsinae includes Pissarrachampsa and Wargosuchus while Baurusuchinae includes Stratiotosuchus and Baurusuchus. Cynodontosuchus is not a member of either of these subfamilies, but the most basal baurusuchid. Many of the unique features that separate Cynodontosuchus may also be associated with a juvenile individual. The material that Cynodontosuchus is based on has been suggested to be a juvenile form of Wargosuchus, and the two taxa may be synonymous.[12]

Below is a cladogram from Montefeltro et al. (2011):[12]

Notosuchia 

A sixth genus of baurusuchid, Campinasuchus, was named just a few months before Pissarrachampsa, and was not included in the analysis.[22]

Darlim et al. (2021) described a new baurusuchid, Aphaurosuchus, and proposed formal definitions for the clades Baurusuchia, Baurusuchidae, Baurusuchinae, and Pissarrachampsinae. In addition to this, the study conducted a phylogenetic analysis to resolve the affinites of the new taxon and provide a reference phylogeny for the newly defined clades. The cladogram of this analysis is shown below.[2]

Baurusuchidae

Cynodontosuchus rothi

Gondwanasuchus scabrosus

Pissarrachampsinae

Campinasuchus dinizi

Pissarrachampsa sera

Wargosuchus australis

Baurusuchinae

Aphaurosuchus escharafacies

Aplestosuchus sordidus

Stratiotosuchus maxhechti

Baurusuchus albertoi

Baurusuchus pachecoi

Baurusuchus salgadoensis

Paleobiology

In 2011, fossilized eggs were described from the Late Cretaceous

oospecies called Bauruoolithus fragilis was named on the basis of these remains. The eggs are about twice as long as they are wide and have blunt ends. At about a quarter of a millimeter in thickness, the shells are relatively thin. Some eggs may have already hatched by the time they were buried, but none show extensive degradation. In living crocodilians (the closest living relatives of baurusuchids), eggs undergo extrinsic degradation to allow hatchlings to easily break through their shells. The fossils indicate that baurusuchid hatchlings probably broke through thin egg shells rather than shells that had been degraded over their incubation period.[23]

References

  1. PMID 30067779
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  2. ^
    PMID 33870512
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  3. doi:10.1016/j.cretres.2006.05.002
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  4. ^ Woodward, A.S. (1896). ". On two Mesozoic crocodilians, Notosuchus (genus novum) and Cynodontosuchus (genus novum) from the red sandstones of the Territory of Neuquén (Argentine Republic)". Anales del Museo de la Plata (Paleontología). 4: 1–20.
  5. doi:10.1016/j.crpv.2008.05.002
    .
  6. ^ Wilson, J.A.; Malkane, M.S.; Gingerich, P.D. (2001). "New crocodyliform (Reptilia, Mesoeucrocodylia) from the Upper Cretaceous Pab Formation of Vitakri, Balochistan (Pakistan)". Contributions from the Museum of Paleontology, University of Michigan. 30 (12): 321–336.
  7. ^
    doi:10.1111/j.1096-3642.2007.00271.x
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  8. doi:10.11646/zootaxa.2871.1.2
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  9. ^ Price, L.I. (1945). "A new reptile from the Cretaceous of Brazil". Rio de Janeiro, Departamento Nacional da Produção Mineral, Notas preliminares e estudos. 25: 1–8.
  10. ^ Colbert, E.H. (1946). "Sebecus, representative of a peculiar suborder of fossil Crocodilia from Patagonia". Bulletin of the American Museum of Natural History. 87: 217–270.
  11. ^
    ISSN 1342-937X. Archived from the original
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  12. ^
    PMID 21765925
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  13. doi:10.1080/02724634.1991.10011401
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  14. doi:10.1016/S0016-6995(96)80037-4
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  15. S2CID 85946263
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  16. ISSN 1342-937X. Archived from the original
    (PDF) on 2011-07-06.
  17. S2CID 86257810
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  18. ^ Clark, J.M. (1997). "Patterns of evolution in Mesozoic Crocodyliformes". In Fraser, N.C.; Sues, H.-D. (eds.). In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods. Cambridge: Cambridge University Press. pp. 84–97.
  19. doi:10.1080/02724634.1999.10011202
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  20. ^
    doi:10.3897/zookeys.28.325. Archived from the original
    on 2010-09-21. Retrieved 2010-08-13.
  21. S2CID 235172623
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  22. doi:10.11646/zootaxa.2871.1.2
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  23. doi:10.1111/j.1475-4983.2010.01028.x
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