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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 Bayanshiree Fm, Cenomanian to Santonian.A, Shamosuchus (= Paralligator) major (PIN 3726/501, holotype), dorsal view; B, PIN 3726/501, ventral view; C, line drawing of PIN 3726/501, dorsal view; D, line drawing of PIN 3726/501, ventral view; E, Shamosuchus (= Paralligator) gradilifrons (PIN 554-1, holotype), dorsal view; F, PIN 554-1, ventral view; G, line drawing of PIN 554-1, dorsal view; H, line drawing of PIN 554-1, ventral view; I, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501), ventral view; J, line drawing of PIN 3458/501, ventral view. Abbreviations: an, angular; ar, articular; bo, basioccipital; d, dentary; ect, ectopteryoid; 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; sa, surangular; sp, splenial; sq, squamosal.
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pone.0118116.g005: Paralligatorids from Bayanshiree Fm, Cenomanian to Santonian.A, Shamosuchus (= Paralligator) major (PIN 3726/501, holotype), dorsal view; B, PIN 3726/501, ventral view; C, line drawing of PIN 3726/501, dorsal view; D, line drawing of PIN 3726/501, ventral view; E, Shamosuchus (= Paralligator) gradilifrons (PIN 554-1, holotype), dorsal view; F, PIN 554-1, ventral view; G, line drawing of PIN 554-1, dorsal view; H, line drawing of PIN 554-1, ventral view; I, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501), ventral view; J, line drawing of PIN 3458/501, ventral view. Abbreviations: an, angular; ar, articular; bo, basioccipital; d, dentary; ect, ectopteryoid; 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; sa, surangular; sp, splenial; sq, squamosal.

Mentions: The holotype skull (PIN 554-1; Figs. 5E-H and 6) is nearly complete but fails to preserve a few of important areas of the skull (most of the secondary palate including palatines and secondary choanae as well as the entirety of the pterygoids and ectopterygoids; note shaded regions in Fig. 5H). The absence of the choanae and pterygoids perhaps helped lead Konzhukova to the believe Paralligator was closely related to the Alligator radiation, given the otherwise superficial resemblance to Alligator. Presumably a more distant relationship to Alligator would have been espoused if the “mesosuchian” grade construction of the palate in Paralligator (like that known at the time in Shamosuchus djadochtaensis) had been known.


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

Turner AH - PLoS ONE (2015)

Paralligatorids from Bayanshiree Fm, Cenomanian to Santonian.A, Shamosuchus (= Paralligator) major (PIN 3726/501, holotype), dorsal view; B, PIN 3726/501, ventral view; C, line drawing of PIN 3726/501, dorsal view; D, line drawing of PIN 3726/501, ventral view; E, Shamosuchus (= Paralligator) gradilifrons (PIN 554-1, holotype), dorsal view; F, PIN 554-1, ventral view; G, line drawing of PIN 554-1, dorsal view; H, line drawing of PIN 554-1, ventral view; I, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501), ventral view; J, line drawing of PIN 3458/501, ventral view. Abbreviations: an, angular; ar, articular; bo, basioccipital; d, dentary; ect, ectopteryoid; 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; sa, surangular; sp, splenial; sq, squamosal.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0118116.g005: Paralligatorids from Bayanshiree Fm, Cenomanian to Santonian.A, Shamosuchus (= Paralligator) major (PIN 3726/501, holotype), dorsal view; B, PIN 3726/501, ventral view; C, line drawing of PIN 3726/501, dorsal view; D, line drawing of PIN 3726/501, ventral view; E, Shamosuchus (= Paralligator) gradilifrons (PIN 554-1, holotype), dorsal view; F, PIN 554-1, ventral view; G, line drawing of PIN 554-1, dorsal view; H, line drawing of PIN 554-1, ventral view; I, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501), ventral view; J, line drawing of PIN 3458/501, ventral view. Abbreviations: an, angular; ar, articular; bo, basioccipital; d, dentary; ect, ectopteryoid; 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; sa, surangular; sp, splenial; sq, squamosal.
Mentions: The holotype skull (PIN 554-1; Figs. 5E-H and 6) is nearly complete but fails to preserve a few of important areas of the skull (most of the secondary palate including palatines and secondary choanae as well as the entirety of the pterygoids and ectopterygoids; note shaded regions in Fig. 5H). The absence of the choanae and pterygoids perhaps helped lead Konzhukova to the believe Paralligator was closely related to the Alligator radiation, given the otherwise superficial resemblance to Alligator. Presumably a more distant relationship to Alligator would have been espoused if the “mesosuchian” grade construction of the palate in Paralligator (like that known at the time in Shamosuchus djadochtaensis) had been known.

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