Limits...
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.

Show MeSH

Related in: MedlinePlus

Jugal morphology in Paralligatoridae.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), right side; B, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), right side; C, S. (= Paralligator) gradilifrons (PIN 554-1, holotype), left side; D, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/7), right side.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4340866&req=5

pone.0118116.g010: Jugal morphology in Paralligatoridae.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), right side; B, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), right side; C, S. (= Paralligator) gradilifrons (PIN 554-1, holotype), left side; D, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/7), right side.

Mentions: Although based on a relatively incomplete skull, PIN 551-29/1 preserves a number of features shared among Shamosuchus species. It possesses the preorbital crest (as noted by Konzhukova), a lateral ridge on the jugal (Fig. 10), and has the lobate squamosal with a depressed anterior margin and a flared posterior process seen in other Shamosuchus (Fig. 7B). There is a boss on the anterolateral corner of the postorbital and a narrow groove runs longitudinally across the dorsal surface of the postorbital near the postorbital-frontal contact (Fig. 7B). The groove through the postorbital is common to all Shamosuchus species except S. djadochtaensis. The boss is common to all Shamosuchus from the Nemegt Fm. (i.e., S. ulanicus, S. tersus), but it is weakly expressed in S. tersus and is variably present in the specimens assigned to S. ulanicus. Given the distribution of these features I see little basis to distinguish S. ancestralis from S. gradilifrons and thus consider S. ancestralis a subjective junior synonym of S. gradilifrons.


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

Turner AH - PLoS ONE (2015)

Jugal morphology in Paralligatoridae.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), right side; B, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), right side; C, S. (= Paralligator) gradilifrons (PIN 554-1, holotype), left side; D, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/7), right side.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0118116.g010: Jugal morphology in Paralligatoridae.A, Shamosuchus ulanicus (= Paralligator gradilifrons) (PIN 3140-502), right side; B, S. tersus (= Paralligator gradilifrons) (PIN 3141-501), right side; C, S. (= Paralligator) gradilifrons (PIN 554-1, holotype), left side; D, S. ancestralis (= Paralligator gradilifrons) (PIN 551-29/7), right side.
Mentions: Although based on a relatively incomplete skull, PIN 551-29/1 preserves a number of features shared among Shamosuchus species. It possesses the preorbital crest (as noted by Konzhukova), a lateral ridge on the jugal (Fig. 10), and has the lobate squamosal with a depressed anterior margin and a flared posterior process seen in other Shamosuchus (Fig. 7B). There is a boss on the anterolateral corner of the postorbital and a narrow groove runs longitudinally across the dorsal surface of the postorbital near the postorbital-frontal contact (Fig. 7B). The groove through the postorbital is common to all Shamosuchus species except S. djadochtaensis. The boss is common to all Shamosuchus from the Nemegt Fm. (i.e., S. ulanicus, S. tersus), but it is weakly expressed in S. tersus and is variably present in the specimens assigned to S. ulanicus. Given the distribution of these features I see little basis to distinguish S. ancestralis from S. gradilifrons and thus consider S. ancestralis a subjective junior synonym of S. gradilifrons.

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