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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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Systematic variation in palate morphology among neosuchians.Numbers indicate character number from phylogenetic dataset using in this study, with state value following the period (i.e., char.charstate). A, Theriosuchus pusillus (NHMUK 48330); B, Iharkutosuchus makadii (MTM 2006.53.1); C, Isisfordia duncani (QM F44320); D, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501).
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pone.0118116.g015: Systematic variation in palate morphology among neosuchians.Numbers indicate character number from phylogenetic dataset using in this study, with state value following the period (i.e., char.charstate). A, Theriosuchus pusillus (NHMUK 48330); B, Iharkutosuchus makadii (MTM 2006.53.1); C, Isisfordia duncani (QM F44320); D, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501).

Mentions: The third unambiguous synapomorphy at this node is also a reversal from a more widespread neosuchian condition. In most basal neosuchians and in all crocodylians examined, the palatal process of the maxilla at the contact with the palatine possesses a posteromedial process that curves around the anterior margin of the suborbital fenestra and onto the bony pharyngeal passage (Fig. 15). This process is particularly well developed in most crown group taxa (it is absent in Gavialis) and variably developed in more basal neosuchian forms. The process is absent in all hylaeochampsids as well as in Theriosuchus, Batrachomimus and Rugosuchus (Fig. 15). As such it is optimized as a synapomorphy uniting the group. Presence of the derived morphology in the Glen Rose Form and the two species of Paralligator is interpreted here as secondary derivations of the morphology.


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

Turner AH - PLoS ONE (2015)

Systematic variation in palate morphology among neosuchians.Numbers indicate character number from phylogenetic dataset using in this study, with state value following the period (i.e., char.charstate). A, Theriosuchus pusillus (NHMUK 48330); B, Iharkutosuchus makadii (MTM 2006.53.1); C, Isisfordia duncani (QM F44320); D, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501).
© Copyright Policy
Related In: Results  -  Collection

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

pone.0118116.g015: Systematic variation in palate morphology among neosuchians.Numbers indicate character number from phylogenetic dataset using in this study, with state value following the period (i.e., char.charstate). A, Theriosuchus pusillus (NHMUK 48330); B, Iharkutosuchus makadii (MTM 2006.53.1); C, Isisfordia duncani (QM F44320); D, Shamosuchus ulgicus (= Paralligator gradilifrons) (PIN 3458/501).
Mentions: The third unambiguous synapomorphy at this node is also a reversal from a more widespread neosuchian condition. In most basal neosuchians and in all crocodylians examined, the palatal process of the maxilla at the contact with the palatine possesses a posteromedial process that curves around the anterior margin of the suborbital fenestra and onto the bony pharyngeal passage (Fig. 15). This process is particularly well developed in most crown group taxa (it is absent in Gavialis) and variably developed in more basal neosuchian forms. The process is absent in all hylaeochampsids as well as in Theriosuchus, Batrachomimus and Rugosuchus (Fig. 15). As such it is optimized as a synapomorphy uniting the group. Presence of the derived morphology in the Glen Rose Form and the two species of Paralligator is interpreted here as secondary derivations of the morphology.

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