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A review of Shamosuchus and Paralligator (Crocodyliformes, Neosuchia) from the Cretaceous of Asia.

Turner AH - PLoS ONE (2015)

Bottom Line: Rugosuchus and Batrachomimus are sister taxa to Paralligator.Paralligatoridae is closely related to Theriosuchus, hylaeochampsids and a speciose Allodaposuchus clade, which together are the sister group of Borealosuchus plus Crocodylia.These results support the presence of a diverse clade in eastern Asia and western North America throughout the Cretaceous with origins in the Late Jurassic.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York, United States of America.

ABSTRACT
The crocodyliform Shamosuchus is known from numerous Late Cretaceous localities in southern and eastern Mongolia and fragmentary remains from Uzbekistan. Seven species of Shamosuchus have been named from six localities in Mongolia and three in Uzbekistan. Six species originally described as Paralligator were later referred to Shamosuchus. Only the type species, Shamosuchus djadochtaensis has been examined in detail. Many of the named species of Shamosuchus show striking similarity in size and cranial morphology but most are based on partial remains suggesting that the true species diversity is overestimated. A review of all species referred to Shamosuchus recognizes three valid taxa: Shamosuchus djadochtaensis, S. gradilifrons, and S. major. Shamosuchus sungaricus, S. borealis, and S. karakalpakensis are nomena dubia, whereas S. ancestralis, S. ulgicus, S. tersus, and S. ulanicus are junior subjective synonyms of S. gradilifrons. Phylogenetic analysis of 318 phenotypic characters recovers a Paralligatoridae clade consisting of Shamosuchus, Rugosuchus, Batrachomimus, Glen Rose Form, and Wannchampsus. Shamosuchus is non-monophyletic: S. djadochtaensis is near the base of Paralligatoridae whereas S. gradilifrons + S. major are the most deeply nested. The name Paralligator is resurrected for this clade. Rugosuchus and Batrachomimus are sister taxa to Paralligator. Paralligatoridae is closely related to Theriosuchus, hylaeochampsids and a speciose Allodaposuchus clade, which together are the sister group of Borealosuchus plus Crocodylia. These results support the presence of a diverse clade in eastern Asia and western North America throughout the Cretaceous with origins in the Late Jurassic.

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Skull morphology of Paralligatoridae.A, Shamosuchus djadochtaensis, AMNH FARB 6412, dorsal view; B, S. djadochtaensis, AMNH FARB 6412, left lateral view; C, S. ulanicus (= Paralligator gradilifrons), PIN 3140-502, left lateral view.
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pone.0118116.g004: Skull morphology of Paralligatoridae.A, Shamosuchus djadochtaensis, AMNH FARB 6412, dorsal view; B, S. djadochtaensis, AMNH FARB 6412, left lateral view; C, S. ulanicus (= Paralligator gradilifrons), PIN 3140-502, left lateral view.

Mentions: Shamosuchus djadochtaensis is known exclusively from the Campanian Djadokhta Fm. Pol et al. [5] provide a detailed diagnosis based on a combination of derived and autapomorphic characters. Autapomorphies for S. djadochtaensis include a dorsal surface of lacrimal and prefrontal that bears a smooth, rounded depression bounded by elevated ridges and a frontal with elevated orbital margins. The frontal participates in supratemporal fossa, as is common in many basal neosuchians. An additional, quite distinctive autapomorphy is the shallow and broad squamosal groove that tapers posteriorly at the level of the posterior edge of the otic aperture which then reappears along the lateral edge of the posterolateral process of the squamosal (Fig. 4B). This morphology produces a “flared” appearance to the lateral profile of the squamosal. S. djadochtaensis also is characterized by a narrow ascending process of the quadratojugal bearing a slightly developed ridge located close to its anterior margin, as well as cervical osteoderms with extremely large lateral keels located along the posterior margin of the osteoderm, possession of a set of osteoderms that are longer than they are wide, and dorsal osteoderms with keels restricted to the posterior margin.


A review of Shamosuchus and Paralligator (Crocodyliformes, Neosuchia) from the Cretaceous of Asia.

Turner AH - PLoS ONE (2015)

Skull morphology of Paralligatoridae.A, Shamosuchus djadochtaensis, AMNH FARB 6412, dorsal view; B, S. djadochtaensis, AMNH FARB 6412, left lateral view; C, S. ulanicus (= Paralligator gradilifrons), PIN 3140-502, left lateral view.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4340866&req=5

pone.0118116.g004: Skull morphology of Paralligatoridae.A, Shamosuchus djadochtaensis, AMNH FARB 6412, dorsal view; B, S. djadochtaensis, AMNH FARB 6412, left lateral view; C, S. ulanicus (= Paralligator gradilifrons), PIN 3140-502, left lateral view.
Mentions: Shamosuchus djadochtaensis is known exclusively from the Campanian Djadokhta Fm. Pol et al. [5] provide a detailed diagnosis based on a combination of derived and autapomorphic characters. Autapomorphies for S. djadochtaensis include a dorsal surface of lacrimal and prefrontal that bears a smooth, rounded depression bounded by elevated ridges and a frontal with elevated orbital margins. The frontal participates in supratemporal fossa, as is common in many basal neosuchians. An additional, quite distinctive autapomorphy is the shallow and broad squamosal groove that tapers posteriorly at the level of the posterior edge of the otic aperture which then reappears along the lateral edge of the posterolateral process of the squamosal (Fig. 4B). This morphology produces a “flared” appearance to the lateral profile of the squamosal. S. djadochtaensis also is characterized by a narrow ascending process of the quadratojugal bearing a slightly developed ridge located close to its anterior margin, as well as cervical osteoderms with extremely large lateral keels located along the posterior margin of the osteoderm, possession of a set of osteoderms that are longer than they are wide, and dorsal osteoderms with keels restricted to the posterior margin.

Bottom Line: Rugosuchus and Batrachomimus are sister taxa to Paralligator.Paralligatoridae is closely related to Theriosuchus, hylaeochampsids and a speciose Allodaposuchus clade, which together are the sister group of Borealosuchus plus Crocodylia.These results support the presence of a diverse clade in eastern Asia and western North America throughout the Cretaceous with origins in the Late Jurassic.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York, United States of America.

ABSTRACT
The crocodyliform Shamosuchus is known from numerous Late Cretaceous localities in southern and eastern Mongolia and fragmentary remains from Uzbekistan. Seven species of Shamosuchus have been named from six localities in Mongolia and three in Uzbekistan. Six species originally described as Paralligator were later referred to Shamosuchus. Only the type species, Shamosuchus djadochtaensis has been examined in detail. Many of the named species of Shamosuchus show striking similarity in size and cranial morphology but most are based on partial remains suggesting that the true species diversity is overestimated. A review of all species referred to Shamosuchus recognizes three valid taxa: Shamosuchus djadochtaensis, S. gradilifrons, and S. major. Shamosuchus sungaricus, S. borealis, and S. karakalpakensis are nomena dubia, whereas S. ancestralis, S. ulgicus, S. tersus, and S. ulanicus are junior subjective synonyms of S. gradilifrons. Phylogenetic analysis of 318 phenotypic characters recovers a Paralligatoridae clade consisting of Shamosuchus, Rugosuchus, Batrachomimus, Glen Rose Form, and Wannchampsus. Shamosuchus is non-monophyletic: S. djadochtaensis is near the base of Paralligatoridae whereas S. gradilifrons + S. major are the most deeply nested. The name Paralligator is resurrected for this clade. Rugosuchus and Batrachomimus are sister taxa to Paralligator. Paralligatoridae is closely related to Theriosuchus, hylaeochampsids and a speciose Allodaposuchus clade, which together are the sister group of Borealosuchus plus Crocodylia. These results support the presence of a diverse clade in eastern Asia and western North America throughout the Cretaceous with origins in the Late Jurassic.

Show MeSH
Related in: MedlinePlus