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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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Paralligatorids from Nemegt Fm, Maastrichtian.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), dorsal view; B, PIN 3140-502, ventral view; C, line drawing of PIN 3140-502, dorsal view; D, line drawing of PIN 3140-502, ventral view; E, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), dorsal view; F, line drawing of PIN 554-1, dorsal view; G, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/1), dorsal view; H, line drawing of PIN 551-29/1, dorsal view. Abbreviations: bo, basioccipital; bs, basisphenoid; d, dentary; f, frontal; j, jugal; la, lacrimal; m, maxilla; n, nasal; ot, otoccipital; pa, parietal; pf, prefrontal; pl, palatine; pm, premaxilla; po, postorbital; pt, pterygoid; q, quadrate; qj, quadratojugal; sq, squamosal.
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pone.0118116.g008: Paralligatorids from Nemegt Fm, Maastrichtian.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), dorsal view; B, PIN 3140-502, ventral view; C, line drawing of PIN 3140-502, dorsal view; D, line drawing of PIN 3140-502, ventral view; E, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), dorsal view; F, line drawing of PIN 554-1, dorsal view; G, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/1), dorsal view; H, line drawing of PIN 551-29/1, dorsal view. Abbreviations: bo, basioccipital; bs, basisphenoid; d, dentary; f, frontal; j, jugal; la, lacrimal; m, maxilla; n, nasal; ot, otoccipital; pa, parietal; pf, prefrontal; pl, palatine; pm, premaxilla; po, postorbital; pt, pterygoid; q, quadrate; qj, quadratojugal; sq, squamosal.

Mentions: Compared to all putative Shamosuchus now known, S. gradilifrons is characterized by a well-developed and heavily ornamented surangular flange on the retroarticular process (Fig. 6C). There appears to be a suite of features present in all or the majority of Shamosuchus taxa described from the Nemegt and Bayanshiree Fms. (Figs. 5 and 8). These include the fifth maxillary tooth being the largest (present in all Shamosuchus species except S. djadochtaensis), a groove that runs through the postorbital near the frontal-postorbital contact (present in all Nemegt and Bayanshiree taxa), a groove that runs through the preorbital crest (present in all Nemegt and Bayanshiree taxa), and a short mandibular symphysis relative to S. djadochtaensis (Figs. 3 and 5F, G). The majority of Nemegt and Bayanshiree Shamosuchus species have robust orbital crests on the frontal that parallel the midline interorbital crest (absent in S. ancestralis and S. tersus) (Figs. 5E, G and 6–8). The holotype of S. gradilifrons has a weakly expressed squamosal groove and posterior flaring of the squamosal (Figs. 6B and 7) combined with well-developed orbital ridges boarding a pronounced interorbital crest (Fig. 6A). This feature appears to be variably developed among the described Shamosuchus species.


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

Turner AH - PLoS ONE (2015)

Paralligatorids from Nemegt Fm, Maastrichtian.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), dorsal view; B, PIN 3140-502, ventral view; C, line drawing of PIN 3140-502, dorsal view; D, line drawing of PIN 3140-502, ventral view; E, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), dorsal view; F, line drawing of PIN 554-1, dorsal view; G, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/1), dorsal view; H, line drawing of PIN 551-29/1, dorsal view. Abbreviations: bo, basioccipital; bs, basisphenoid; d, dentary; f, frontal; j, jugal; la, lacrimal; m, maxilla; n, nasal; ot, otoccipital; pa, parietal; pf, prefrontal; pl, palatine; pm, premaxilla; po, postorbital; pt, pterygoid; q, quadrate; qj, quadratojugal; sq, squamosal.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4340866&req=5

pone.0118116.g008: Paralligatorids from Nemegt Fm, Maastrichtian.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), dorsal view; B, PIN 3140-502, ventral view; C, line drawing of PIN 3140-502, dorsal view; D, line drawing of PIN 3140-502, ventral view; E, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), dorsal view; F, line drawing of PIN 554-1, dorsal view; G, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/1), dorsal view; H, line drawing of PIN 551-29/1, dorsal view. Abbreviations: bo, basioccipital; bs, basisphenoid; d, dentary; f, frontal; j, jugal; la, lacrimal; m, maxilla; n, nasal; ot, otoccipital; pa, parietal; pf, prefrontal; pl, palatine; pm, premaxilla; po, postorbital; pt, pterygoid; q, quadrate; qj, quadratojugal; sq, squamosal.
Mentions: Compared to all putative Shamosuchus now known, S. gradilifrons is characterized by a well-developed and heavily ornamented surangular flange on the retroarticular process (Fig. 6C). There appears to be a suite of features present in all or the majority of Shamosuchus taxa described from the Nemegt and Bayanshiree Fms. (Figs. 5 and 8). These include the fifth maxillary tooth being the largest (present in all Shamosuchus species except S. djadochtaensis), a groove that runs through the postorbital near the frontal-postorbital contact (present in all Nemegt and Bayanshiree taxa), a groove that runs through the preorbital crest (present in all Nemegt and Bayanshiree taxa), and a short mandibular symphysis relative to S. djadochtaensis (Figs. 3 and 5F, G). The majority of Nemegt and Bayanshiree Shamosuchus species have robust orbital crests on the frontal that parallel the midline interorbital crest (absent in S. ancestralis and S. tersus) (Figs. 5E, G and 6–8). The holotype of S. gradilifrons has a weakly expressed squamosal groove and posterior flaring of the squamosal (Figs. 6B and 7) combined with well-developed orbital ridges boarding a pronounced interorbital crest (Fig. 6A). This feature appears to be variably developed among the described Shamosuchus species.

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