Sebecosuchia

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Sebecosuchia
Temporal range: Middle Jurassic - Middle Miocene, 167–11  Ma
Baurusuchus BW.jpg
Life restoration of Baurusuchus salgadoensis
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Clade: Crocodyliformes
Clade: Notosuchia
Clade: Xenodontosuchia
Clade: Sebecosuchia
Simpson, 1937
Families

Sebecosuchia (meaning "Sobek crocodiles") is an extinct group of mesoeucrocodylian crocodyliforms that includes the families Sebecidae and Baurusuchidae. The group was long thought to have first appeared in the Late Cretaceous with the baurusuchids and become extinct in the Miocene with the last sebecids, but Razanandrongobe pushes the origin of Sebecosuchia to the Middle Jurassic. [1] Fossils have been found primarily from South America but have also been found in Europe, North Africa, Madagascar, and the Indian subcontinent.

History and phylogeny

Sebecosuchia was first constructed in 1937 by George Gaylord Simpson. [2] In 1946 the concept was again used by American paleontologist Edwin Colbert to include Sebecus and Baurusuchidae. Sebecus, which had been known from South America since 1937, was an unusual crocodyliform with a deep snout and teeth that were ziphodont, or serrated and laterally compressed. The family Baurusuchidae was named the year before and included the newly described Baurusuchus, which was also a South American deep-snouted form. [3]

More recently, other crocodyliforms have been assigned to Sebecosuchia that cannot be placed into either family. These include the genera Eremosuchus , named in 1989, and Pehuenchesuchus , named in 2005. They are usually considered to be more basal sebecosuchians than the sebecids and baurusuchids. [3]

Below is a cladogram showing the possible phylogenetic position of Sebecosuchia modified from Turner and Calvo (2005). In this cladogram, Sebecidae is a paraphyletic assemblage of basal sebecosuchians while Baurusuchidae is monophyletic and includes the more derived sebecosuchians.

Crocodyliformes  

In a phylogenetic study of crocodyliforms, Benton and Clark (1988) split up Sebecosuchia, finding baurusuchids to be basal notosuchians while sebecids were basal neosuchians. Since that time, most studies have supported a monophyletic Sebecosuchia. In 2007, however, a phylogenetic study placed baurusuchids as basal metasuchians and sebecids as close relatives to a family of notosuchians called the Peirosauridae. Together, sebecids and peirosaurids made the new clade Sebecia. Below is a cladogram from that study, Larsson and Sues (2007): [4]

Sebecosuchians
Sebecosuchians

Two years later, Sereno and Larsson (2009) came to the same conclusion, except they placed baurusuchids as advanced notosuchians. More recently however, Turner and Sertich (2010) found support for Sebecosuchia in their analysis of notosuchian relationships. In their study, Sebecosuchia was a derived clade within Notosuchia. Iori and Carvalho (2011) came to similar conclusions, grouping Baurusuchus alongside Sebecidae. Below is the cladogram from Turner and Sertich (2010): [5]

Notosuchia

Diego Pol and Jaime E. Powell (2011) came to the same conclusion, however their analysis couldn't find a monophyletic Baurusuchidae within Sebecosuchia. The following cladogram simplified after their analysis, with focus on Sebecosuchia. [6]

Paleobiology

Sahitysuchus skull Sahitysuchus.png
Sahitysuchus skull

All sebecosuchians were carnivorous and terrestrial. The nares open at the very tip of the snout, suggesting that it lived on land rather than in water (in aquatic crocodyliforms, the nares usually open dorsally on top of the snout). The snout itself is laterally compressed, a feature shared with other terrestrial reptiles such as theropod dinosaurs. The eye sockets are opened laterally rather than dorsally as in aquatic crocodyliforms. Moreover, there is a prominent fourth trochanter on the femur for the attachment of muscles that would have aided in upright walking. Although they are now widely accepted to be terrestrial, sebecosuchians were once thought to be semiaquatic, spending part of their time in water.

The laterally compressed snout of sebecosuchians may have enabled them to withstand high forces during biting. The teeth are also laterally compressed, pointed, and serrated. Their shape would have allowed them to easily penetrate and slice flesh. The pterygoid bone in the skull is strongly bent, allowing for a larger jaw adductor muscle to quickly close the jaws and give sebecosuchians a powerful bite. [7]

Related Research Articles

<i>Simosuchus</i> Extinct genus of reptiles

Simosuchus is an extinct genus of notosuchian crocodyliforms from the Late Cretaceous of Madagascar. It is named for its unusually short skull. Fully grown individuals were about 0.75 metres (2.5 ft) in length. The type species is Simosuchus clarki, found from the Maevarano Formation in Mahajanga Province, although one isolated multicuspid tooth of this genus was discovered in Kallamedu Formation of India.

<i>Razanandrongobe</i> Genus of fossil reptiles related to crocodilians

Razanandrongobe is a genus of carnivorous ziphosuchian crocodyliform from the Middle Jurassic of Madagascar. It contains the type and only species Razanandrongobe sakalavae, named in 2004 by Simone Maganuco and colleagues based on isolated bones found in 2003. The remains, which included a fragment of maxilla and teeth, originated from the Bathonian-aged Sakaraha Formation of Mahajanga, Madagascar. While they clearly belonged to a member of the Archosauria, Maganuco and colleagues refrained from assigning the genus to a specific group because the fragmentary remains resembled lineages among both the theropod dinosaurs and crocodylomorphs.

<i>Baurusuchus</i> Extinct genus of reptiles

Baurusuchus is an extinct genus of baurusuchid mesoeucrocodylian, which lived in Brazil from 90 to 83.5 million years ago, in the Late Cretaceous period. It was a terrestrial predator and scavenger, estimated to reach up to 113.4 kilograms (250 lb) in weight. Baurusuchus lived during the Turonian to Santonian stages of the Late Cretaceous Period, in Adamantina Formation, Brazil. It gets its name from the Brazilian Bauru Group. It was related to the earlier-named Cynodontosuchus rothi, which was smaller, with weaker dentition. The three species are B. pachechoi, named after Eng Joviano Pacheco, its discoverer, B. salgadoensis and B. albertoi. The latter species is disputed. Its relatives include the similarly sized Stratiotosuchus from the Adamantina Formation, and Pabweshi, from the Pakistani Pab Formation.

<span class="mw-page-title-main">Notosuchia</span> Extinct suborder of reptiles

Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group ; if Sebecosuchia is included within Notosuchia its existence is pushed into the Middle Miocene, about 11 million years ago. Fossils have been found from South America, Africa, Asia, and Europe. Notosuchia was a clade of terrestrial crocodilians that evolved a range of feeding behaviours, including herbivory (Chimaerasuchus), omnivory (Simosuchus), and terrestrial hypercarnivory (Baurusuchus). It included many members with highly derived traits unusual for crocodylomorphs, including mammal-like teeth, flexible bands of shield-like body armor similar to those of armadillos (Armadillosuchus), and possibly fleshy cheeks and pig-like snouts (Notosuchus). The suborder was first named in 1971 by Zulma Gasparini and has since undergone many phylogenetic revisions.

<span class="mw-page-title-main">Baurusuchidae</span> Extinct family of reptiles

Baurusuchidae is a Gondwanan family of mesoeucrocodylians that lived during the Late Cretaceous. It is a group of terrestrial hypercarnivorous crocodilians from South America and possibly Pakistan. Baurusuchidae has been, in accordance with the PhyloCode, officially defined as the least inclusive clade containing Cynodontosuchus rothi, Pissarrachampsa sera, and Baurusuchus pachecoi. Baurusuchids have been placed in the suborder Baurusuchia, and two subfamilies have been proposed: Baurusuchinae and Pissarrachampsinae.

<i>Barinasuchus</i> Extinct genus of reptiles

Barinasuchus is an extinct genus of sebecid mesoeucrocodylian. Its fossils have been found in middle Eocene-age rocks of the Divisadero Largo Formation of Argentina, middle Miocene-age rocks of the Ipururo Formation of Peru, and middle Miocene-age rocks of the Parángula Formation of Venezuela.

Pabwehshi is an extinct genus of mesoeucrocodylian. It is based on GSP-UM 2000, a partial snout and corresponding lower jaw elements, with another snout assigned to it. These specimens were found in Maastrichtian-age Upper Cretaceous rocks of the Vitakri and Pab Formations in Balochistan, Pakistan, and represent the first diagnostic crocodyliform fossils from Cretaceous rocks of South Asia. Pabwehshi had serrated interlocking teeth in its snout that formed a "zig-zag" cutting edge. Pabwehshi was named in 2001 by Jeffrey A. Wilson and colleagues. The type species is P. pakistanensis, in reference to the nation where it was found. It was traditionally classified as a baurusuchid closely related to Cynodontosuchus and Baurusuchus. Larsson and Sues (2007) found close affinity between Pabwehshi and the Peirosauridae within Sebecia. Montefeltro et al.Pabwehshi has a sagittal torus on its maxillary palatal shelves – a character that is absent in baurusuchids – but they did not include Pabwehshi in their phylogenetic analysis.

Trematochampsidae is an extinct family of mesoeucrocodylian crocodyliforms. Fossils are present from Madagascar, Morocco, Niger, Argentina, and Brazil. Possible trematochampsids have been found from Spain and France, but classification past the family level is indeterminant. The trematochampsids first appeared during the Barremian stage of the Early Cretaceous and became extinct during the late Maastrichtian stage of the Late Cretaceous.

<i>Bergisuchus</i> Extinct genus of reptiles

Bergisuchus is an extinct genus of small sebecosuchian mesoeucrocodylian known primarily from the Eocene Messel Pit in Germany. Few fossils of Bergisuchus have been discovered, only a single incomplete snout, a few partial lower jaws and some teeth. Despite being fragmentary, the jaw bones are enough to indicate that Bergisuchus had a short, deep, narrow snout and serrated teeth, quite unlike the broad flat snouts of modern crocodylians.

<i>Bretesuchus</i> Extinct genus of reptiles

Bretesuchus is an extinct genus of sebecosuchian mesoeucrocodylian within the family Sebecidae known from northwestern Argentina. It was a large apex predator.

Eremosuchus is an extinct genus of sebecosuchian mesoeucrocodylian. Fossils have been found from El Kohol, Algeria of Eocene age. It had serrated, ziphodont teeth.

Ilchunaia is an extinct genus of sebecid mesoeucrocodylian. Fossils have been found from the Divisadero Largo Formation of Argentina dating back to the Late Eocene, and a locality in Mendoza, Argentina dating back to the Oligocene. Little material is known from the genus, with only the anterior portion of the skull being present to study.

<i>Kaprosuchus</i> Genus of crocodyliform from the Late Cretaceous period

Kaprosuchus is an extinct genus of mahajangasuchid crocodyliform. It is known from a single nearly complete skull collected from the Upper Cretaceous Echkar Formation of Niger. The name means "boar crocodile" from the Greek κάπρος, kapros ("boar") and σοῦχος, soukhos ("crocodile") in reference to its unusually large caniniform teeth which resemble those of a boar. It has been nicknamed "BoarCroc" by Paul Sereno and Hans Larsson, who first described the genus in a monograph published in ZooKeys in 2009 along with other Saharan crocodyliformes such as Anatosuchus and Laganosuchus. The type species is K. saharicus.

<span class="mw-page-title-main">Metasuchia</span> Clade of reptiles

Metasuchia is a major clade within the superorder Crocodylomorpha. It is split into two main groups, Notosuchia and Neosuchia. Notosuchia is an extinct group that contains primarily small-bodied Cretaceous taxa with heterodont dentition. Neosuchia includes the extant crocodylians and basal taxa, such as peirosaurids and pholidosaurids. It is phylogenetically defined by Sereno et al. (2001) as a clade containing Notosuchus terrestris, Crocodylus niloticus, and all descendants of their common ancestor.

<i>Sebecus</i> Extinct genus of reptiles

Sebecus is an extinct genus of sebecid crocodylomorph from Eocene of South America. Like other sebecosuchians, it was entirely terrestrial and carnivorous. The genus is currently represented by two species, the type S. icaeorhinus and S. ayrampu. Several other species have been referred to Sebecus, but were later reclassified as their own genera.

<span class="mw-page-title-main">Sebecia</span> Extinct clade of reptiles

Sebecia is an extinct clade of mesoeucrocodylian crocodyliforms that includes peirosaurids and sebecids. It was first constructed in 2007 to include Hamadasuchus, Peirosauridae, and Sebecus. It was initially considered to be the sister taxon of the clade Neosuchia, which includes living crocodilians, although some later studies have placed it within Neosuchia as a basal clade. Sebecians were terrestrial crocodyliforms characterized by their deep snouts and ziphodont dentition. They first appeared in the Late Cretaceous, survived the Cretaceous–Paleogene extinction event, and became extinct in the Miocene epoch.

<i>Stratiotosuchus</i> Prehistoric genus of reptiles

Stratiotosuchus is an extinct genus of baurusuchid mesoeucrocodylian from the Adamantina Formation in Brazil. It lived during the Late Cretaceous. The first fossils were found in the 1980s, and the type species Stratiotosuchus maxhechti was named in 2001. A hyperpredator, it and other baurusuchids may have filled niches occupied elsewhere by theropod dinosaurs.

<i>Campinasuchus</i> Extinct genus of reptiles

Campinasuchus is an extinct genus of baurusuchid mesoeucrocodylian from Minas Gerais State of Brazil.

<i>Pissarrachampsa</i> Extinct genus of reptiles

Pissarrachampsa is an extinct genus of baurusuchid mesoeucrocodylian from the Late Cretaceous of Brazil. It is based on a nearly complete skull and a referred partial skull and lower jaw from the ?Campanian - ?Maastrichtian-age Vale do Rio do Peixe Formation of the Bauru Group, found in the vicinity of Gurinhatã, Brazil.

<i>Sahitisuchus</i> Extinct genus of reptiles

Sahitisuchus is an extinct genus of sebecid mesoeucrocodylian known from Rio de Janeiro State of southeastern Brazil. It contains a single species, Sahitisuchus fluminensis. It is a terrestrial sebecid, however also adopted to a semi-aquatic lifestyle to some degree, most probably coexisting with the semi-aquatic alligatorid Eocaiman itaboraiensis.

References

  1. Dal Sasso C, Pasini G, Fleury G, Maganuco S. (2017) Razanandrongobe sakalavae, a gigantic mesoeucrocodylian from the Middle Jurassic of Madagascar, is the oldest known notosuchian. PeerJ 5:e3481 https://doi.org/10.7717/peerj.3481
  2. Simpson, G.G. 1937. "New reptiles from the Eocene of South America". American Museum Novitates967: 1-20
  3. 1 2 Turner, A.H.; Calvo, J.O. (2005). "A new sebecosuchian crocodyliform from the Late Cretaceous of Patagonia" (PDF). Journal of Vertebrate Paleontology. 25 (1): 87–98. doi:10.1671/0272-4634(2005)025[0087:ANSCFT]2.0.CO;2.
  4. Larsson, H. C. E.; Sues, H.-D. (2007). "Cranial osteology and phylogenetic relationships of Hamadasuchus rebouli (Crocodyliformes: Mesoeucrocodylia) from the Cretaceous of Morocco". Zoological Journal of the Linnean Society. 149 (4): 533–567. doi: 10.1111/j.1096-3642.2007.00271.x .
  5. Turner, Alan H.; Sertich, Joseph J. W. (2010). "Phylogenetic history of Simosuchus clarki (Crocodyliformes: Notosuchia) from the Late Cretaceous of Madagascar". Journal of Vertebrate Paleontology. 30 (6, Memoir 10): 177–236. doi:10.1080/02724634.2010.532348.
  6. Diego Pol and Jaime E. Powell (2011). "A new sebecid mesoeucrocodylian from the Rio Loro Formation (Palaeocene) of north-western Argentina". Zoological Journal of the Linnean Society. 163: S7–S36. doi: 10.1111/j.1096-3642.2011.00714.x . hdl: 11336/69518 .
  7. Carvalho, I.S.; Campos, A.C.A.; Nobre, P.H. (2005). "Baurusuchus salgadoensis, a new Crocodylomorpha from the Bauru Basin (Cretaceous), Brazil" (PDF). Gondwana Research. 8 (1): 11–30. doi:10.1016/S1342-937X(05)70259-8.