[Paleontology • 2023] Colossosuchus techniensis • A Giant Phytosaur (Diapsida: Archosauria) from the Upper Triassic of India with New insights on Phytosaur Migration, Endemism and Extinction

Colossosuchus techniensis

Datta & Ray, 2023 

 

DOI: 10.1002/spp2.1476 

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Abstract

A new Mystriosuchinae phytosaur, Colossosuchus techniensis, is described from the Upper Triassic Tiki Formation of India. Colossosuchus is diagnosed by multiple apomorphies, including a strongly downturned terminal rosette (c. 70°), closely spaced mediolateral band-like ornamentation on dorsal surface of the nasal, dorsolaterally oriented supratemporal fenestra, ventrolaterally inclined postorbital–squamosal bars depressed below the skull table, dorsally convex parietal–squamosal bar that descends ventrolaterally below the skull roof, dome-shaped skull in lateral view, prominent neural arch laminae and fossae, three sacral vertebrae, robust proximal end of the tibia, and fibula with high anteroposterior flaring of the distal end. The total body length of the largest individual recovered from the bonebed is estimated to be more than 8 m, suggesting that Colossosuchus is one of the largest phytosaurs known. Phylogenetic analysis nests Colossosuchus and other undescribed specimens from India within Mystriosuchinae. These form a distinct clade and represent the earliest record of endemism among Gondwanan phytosaurs. This clade is recovered as sister taxa to ((Volcanosuchus + Rutiodon) + Leptosuchomorpha), where the depressed supratemporal fenestra first appeared in the phytosaur lineage, a feature previously used to diagnose the derived leptosuchomorphs. Early-diverging phytosaur diversification may have coincided with the final stages of the Carnian Pluvial Event with their possible migratory routes along the circum-Tethyan coastline. The lineage continued to evolve mostly through endemic radiations and experienced an extinction event during early Norian, which marked the disappearance of most of the non-leptosuchomorph taxa. This is attributed to post-CPE aridification, although more study is required.

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

Colossosuchus techniensis

Debajit Datta and Sanghamitra Ray. 2023.  A Giant Phytosaur (Diapsida, Archosauria) from the Upper Triassic of India with New insights on Phytosaur Migration, Endemism and Extinction. Papers in Palaeontology. DOI: 10.1002/spp2.1476 

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[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

DOI: 10.1002/spp2.1292  

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Abstract

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) 

Genus VOLCANOSUCHUS nov. 

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

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[Paleontology • 2019] Mystriosuchus steinbergeri • Description and Phylogenetic Placement of A New Marine Species of Phytosaur (Archosauriformes: Phytosauria) from the Late Triassic of Austria

Mystriosuchus steinbergeri 

Butler, Jones, Buffetaut, Mandl, Scheyer & Schultz, 2019

DOI:  10.1093/zoolinnean/zlz014

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Abstract

Phytosaurs are a group of carnivorous, semi-aquatic archosaurian reptiles that attained an almost global distribution during the Late Triassic. We here describe a new species of the phytosaur genus Mystriosuchus from the Norian Dachstein Limestone of Austria, from a marine lagoonal depositional environment. The new Austrian material comprises remains of at least four individuals of similar size (c. 4 m in total length) found in association but disarticulated, and includes one complete and two partial skulls and postcrania. All of these specimens apparently represent a single taxon, which is distinguished by numerous anatomical features from the two previously named Mystriosuchus species. Maximum parsimony analysis of a comprehensive morphological dataset provides strong statistical support for the phylogenetic position of the new Austrian taxon in Mystriosuchus, as the sister taxon to a clade comprising M. planirostris and M. westphali. Histological analysis suggests that the Austrian phytosaur specimens represent individuals that were at least eight years old at time of death, but which had not yet reached skeletal maturity. Taphonomic and palaeoenvironmental data suggest that these phytosaurs were living in the marine lagoon in which they were preserved, providing the strongest evidence to date of marine adaptations in phytosaurs.

Keywords: bone histology, fossils, marine adaptations, morphology, phylogeny, reptiles

Figure 5. Holotype skull of Mystriosuchus steinbergeri sp. nov. (NHMW 1986/0024/0001)
 in right lateral (A), posterior (B), medial cross-sectional (C), dorsal (D) and ventral (E) views.

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Figure 1. Photographs taken in 1982 during the collection of the type and referred material of Mystriosuchus steinbergeri sp. nov. A, the type locality. The five figures in the centre of the photograph are clustered around the excavation site. B, the excavation team, including from left-to-right, Johann Segl, Sepp Steinberger, Georg Sverak and Walter Prenner. Georg Sverak is using the pneumatic hammer to drill a hole for a wedge used to split the blocks of limestone for removal. C, Georg Sverak and Walter Prenner in front of their tent. D, photograph of the block, as originally excavated, including the holotype skull (NHMW 1986/0024/0001; bottom right of photograph) and paratype mandible (NHMW 1986/0024/0002; top middle of photograph) in close association.

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Life reconstruction of Mystriosuchus steinbergeri sp. nov. in the Dachstein Limestone depositional environment.

Illustration: Mark Witton.

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SYSTEMATIC PALAEONTOLOGY 

Archosauriformes Gauthier, 1986 

Phytosauria Jaeger, 1828

Parasuchidae Lydekker, 1885 sensu Kammerer et al., 2015 

Mystriosuchinae Huene, 1915 sensu Kammerer et al., 2015 

Leptosuchomorpha Stocker, 2010 sensu Jones & Butler, 2018 

Mystriosuchini Huene, 1915 sensu Jones & Butler, 2018 

Mystriosuchus Fraas, 1896

Mystriosuchus steinbergeri sp. nov.

Etymology: The species is named for Sepp Steinberger, who discovered and helped collect the holotype and referred specimens.

Richard J. Butler, Andrew S. Jones, Eric Buffetaut, Gerhard W. Mandl, Torsten M. Scheyer and Ortwin Schultz. 2019. Description and Phylogenetic Placement of A New Marine Species of Phytosaur (Archosauriformes: Phytosauria) from the Late Triassic of Austria. Zoological Journal of the Linnean Society. zlz014. DOI:  10.1093/zoolinnean/zlz014  

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