Sunday, December 15, 2019

[Paleontology • 2020] Volcanosuchus statisticae • A New Phytosaur (Diapsida, Archosauria) from the Upper Triassic of India: Implications for Phytosaur Phylogeny and Biostratigraphy

Volcanosuchus statisticae
Datta, Ray & Bandyopadhyay, 2020

Detailed description and phylogenetic assessment of a phytosaur skull collected from the Tiki Formation of the Rewa Gondwana Basin of India and earlier diagnosed as Parasuchus hislopi, show that it pertains to a new genus and species, Volcanosuchus statisticae. The new taxon is characterized by marginal overlapping of the nostrils by the antorbital fenestrae, external nares situated on a bulbous and raised dome, the lateral surface of the jugal ornamented by a prominent ridge defined by multiple tubercles and radiating thread‐like structures, and distinct ornamentation patterns on the rostrum and skull table. Phylogenetic analysis nests Volcanosuchus within Mystriosuchinae, where it forms a sister taxon to (Rutiodon + Leptosuchomorpha) and marks the transition between the basal Parasuchidae and more derived Mystriosuchinae phytosaurs. Evolution of the phytosaur skulls resulted in changes from non‐overlapping nostril and antorbital fenestra to an overlapping state, anteroposterior elongation of the exoccipital–supraoccipital shelf, appearance of a median ridge on the basioccipital, and reduction of the supratemporal fenestra. Considerable faunal overlap of the Tiki Formation is evident with the lower Maleri Formation, which is late Carnian based on the occurrence of Hyperodapedon, Parasuchus and Exaeretodon. The Tiki Formation correlates with the Ischigualasto Formation of Argentina, the upper part of the Santa Maria Formation, and the overlying lower Caturrita Formation of Brazil, the Isalo II Beds of Madagascar, Lossiemouth Sandstone of Scotland, and the lower Tecovas Formation of the Chinle Group of North America, and ranges from late Carnian to early/middle Norian.

Keywords: archosaur, Gondwana, India, Late Triassic, phytosaur, phylogeny

Volcanosuchus statisticae gen. et sp. nov. Holotype, ISIR 44, a partial skull in dorsal view.

Volcanosuchus statisticae gen. et sp. nov. Holotype, ISIR 44, a partial skull in right lateral view.

ARCHOSAURIA Cope, 1869–1870 (sensu Ezcurra 2016) 

Order PHYTOSAURIA Jaeger, 1828 

Family PARASUCHIDAE Lydekker, 1885 (sensu Kammerer et al. 2016) 
Subfamily MYSTRIOSUCHINAE von Huene, 1915 (sensu Kammerer et al. 2016) 


Derivation of name. Generic name, derived from the Latin word ‘volcanus’ referring to the raised dome-like narial prominence, which resembles a high volcanic crater in lateral view, and ‘suchus’ meaning crocodile-like.

Volcanosuchus statisticae sp. nov.

Derivation of name. Specific name is after the Indian Statistical Institute, Kolkata, one of the first institutes in India to promote and establish a school of vertebrate palaeontology.

Debajit Datta, Sanghamitra Ray and Saswati Bandyopadhyay. 2020. Cranial Morphology of A New Phytosaur (Diapsida, Archosauria) from the Upper Triassic of India: Implications for Phytosaur Phylogeny and Biostratigraphy. Papers in Palaeontology. DOI: 10.1002/spp2.1292