New Long-Necked and Horned Stem Archosaur from India
The Weird and Wonderful Shringasaurus indicus
The Triassic had some very weird and wonderful animals. Fantastic phytosaurs, the first pterosaurs, evolving and radiating members of the Dinosauria and joining this menagerie is the newly described Shringasaurus indicus, a large, herbivorous, horned plant-eater that superficially resembled a horned dinosaur.
An Illustration of the Newly Described Basal Archosaur S. indicus
Picture Credit: Conicet
A Pair of Large Supraorbital Horns
The most surprising feature of this reptile is the pair of large, forward pointing horns located on the top of the animal’s skull. These horns resemble those of some Cretaceous Ceratopsian dinosaurs, famous beasties from the fossil record such as Triceratops, Torosaurus and Chasmosaurus. The fossilised remains of Shringasaurus indicus were recovered from a red mudstone in the upper part of the Denwa Formation (north, central India). At least seven individuals of different growth stages were excavated from an area of approximately twenty-five square metres. Most of the specimens were disarticulated, with the exception of one partially articulated skeleton. Back in the early Middle Triassic, when Shringasaurus roamed, India was located in the southern hemisphere, part of a super-continent called Pangaea.
The Horns of Shringasaurus are Similar to Those of a Horned Dinosaur
Picture Credit: Scientific Reports
The picture above shows a line drawing (lateral view) of the skull of an adult S. indicus (a) compared to a lateral view of the skull of the Canadian, Chasmosaurine dinosaur Arrhinoceratops brachyops, (b) which was distantly related to Triceratops. The line drawing (c) shows the skull of S. indicus in dorsal view, (looking down onto the skull). Photographs d-g show dorsal views of several individuals at different growth stages. To produce a complete dorsal view of the skull, missing fossils have been reconstructed by digitally mirroring their preserved counterpart. As these reptiles grew, so the horns became larger and more prominent. Photographs h-j show lateral views of the bony horns. Specimens d to f and h-j possess horns and the two smallest specimens, representing the youngest individual (g and k) lack horns.
Scale bar = 4 cm for (a) and (c to k), the scale bar for the Ceratopsian skull is 20 cm (b)
en = external naris
ho = horn
or = orbit
stf = supratemporal fenestra
The researchers conclude that these horns were probably used in intraspecific combats, perhaps over mates, or to decide the hierarchy of the herd. This new study supports the idea of sexual selection pressure leading to the evolution of bizarre ornamentation within the Archosauria.
Commenting on the significance of this discovery, one of the authors of the scientific paper, Martín D. Ezcurra (CONICET–Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina), stated:
“An animal like Shringasaurus is remarkable for its horns, a completely unexpected feature in this group of reptiles. It shows that sexual selection led to the development of strange anatomical structures in the early evolutionary history of the Arcosauromorphs, a group that includes dinosaurs, crocodiles and birds.”
The Fossil Material Associated with Shringasaurus
Picture Credit: Scientific Reports
The genus name is a combination of Greek and ancient Sanskrit, it means “horned reptile”. This unusual reptile with its pair of horns has provided an insight to the diverse range of reptiles that occupied this part of Pangaea during the Anisian faunal stage of the Middle Triassic some 245 to 243 million years ago.