A new horned and long-necked herbivorous stem-archosaur from the Middle Triassic of India

Abstract

The early evolution of archosauromorphs (bird- and crocodile-line archosaurs and stem-archosaurs) represents an important case of adaptive radiation that occurred in the aftermath of the Permo-Triassic mass extinction. Here we enrich the early archosauromorph record with the description of a moderately large (3–4 m in total length), herbivorous new allokotosaurian, Shringasaurus indicus, from the early Middle Triassic of India. The most striking feature of Shringasaurus indicus is the presence of a pair of large supraorbital horns that resemble those of some ceratopsid dinosaurs. The presence of horns in the new species is dimorphic and, as occurs in horned extant bovid mammals, these structures were probably sexually selected and used as weapons in intraspecific combats. The relatively large size and unusual anatomy of Shringasaurus indicus broadens the morphological diversity of Early–Middle Triassic tetrapods and complements the understanding of the evolutionary mechanisms involved in the early archosauromorph diversification.

Colobops : a juvenile rhynchocephalian reptile (Lepidosauromorpha), not a diminutive archosauromorph with an unusually strong bite

“…STF, supratemporal fenestra. [1,[18][19][20][21][22][23]. We used this data matrix because it has key taxa and characters that we consider important to test the phylogenetic position of a putative early rhynchosaur, as is the case for Colobops noviportensis.…”

Osteology of the archosauromorph Teyujagua paradoxa and the early evolution of the archosauriform skull

“…The absence of an anterodorsal process and the consequent confluence of the external nares is an unusual feature in archosauromorphs. Among non-archosauriforms, confluent nares are apparently present in allokotosaurians, such as Pamelaria, Azendohsaurus and Shringasaurus (Sen, 2003;Flynn et al, 2010;Sengupta et al, 2017), and this feature is also a synapomorphy of the extremely specialized rhynchosaurs (Ezcurra et al, 2016).…”

Gondwana Vertebrate Faunas of India: Their Diversity and Intercontinental Relationships

“…Recently the horned allokotosaur Shringasaurus (Fig. 6A-B) has been described from this horizon (Sengupta et al, 2017). This is the only known horned Triassic reptile to date.…”

“…Recently, a new capitosaurid temnospondyl, Antarctosuchus, a sister taxon to the Indian form Paracyclotosaurus crookshanki, has been described from the upper Fremouw Formation of Antarctica (Sidor et al, 2014). Based on this fossil fauna, the age of the Denwa Formation is considered as Anisian (Bandyopadhyay and Sengupta, 1999;Sengupta et al, 2016Sengupta et al, , 2017.…”