Before the famous horned ceratopsian dinosaurs like Triceratops evolved, there was Shringasaurus.
This large reptile from the Triassic period possessed two horns upon its head similar to those of the later horned dinosaurs.
Besides it horns, Shringasaurus’s overall appearance looked vaguely like a large, muscular, long-necked lizard.
Shringasaurus’s full binomial name, Shringasaurus indicus, means “Indian Horned Lizard”, in reference to its distinguishing horns and country of origin.
First described in in 2017, all known Shringasaurus fossils come from a single bonebed in India. This bonebed only contains fossils of Shringasaurus, with bones of at least seven individuals.
Given how many Shringasaurus skeletons of various ages were found together in this bonebed, with no other species in the present, it seems likely that Shringasaurus lived in herds.
The Shringasaurus bonebed is part of the Denwa Formation. While not dated, the fauna present suggests the Denwa Formation was formed during the Anisian stage of Middle Triassic, between roughly 247 to 242 million years ago.
By this point, life had still not fully recovered from the Permian Mass Extinction and animals were still diversifying to fill the gaps the catastrophe left behind.
Rather fittingly for an animal that so closely resemble the “dinosaurs” in cheap movies that were played lizards with horns tack on Shringasaurus was not a dinosaur.
Instead, it was part of a larger group of reptiles called Archosauromorpha,
which contains dinosaurs, crocodilians, and all reptiles more closely related to them than any other living reptiles
Shringasaurus was an early member of the group, lacking many of the traits of the more advanced archosaurs. Instead, it belonged to a subgroup of archosauromorphs called Allokotosauria.
Like, Shringasaurus most allokotosaurs also looked superficially like lizards.
The closest relative of Shringasaurus was Azendohsaurus. While similar to Shringasaurus in appearance, Azendohsaurus was slightly smaller, not as powerfully built, and lacked Shringasaurus’s iconic horns.
As its teeth were leaf shaped, there is little doubt that Shringasaurus was a herbivore. No other herbivorous archosauromorphs are known to have attained large size until the Late Triassic
with the only other large Middle Triassic herbivores being the dicynodonts.
As the Triassic progressed, dicynodonts would become rarer and archosauromorphs take their place as the dominant large herbivores.
While Shringasaurus may represent the first stages of this faunal revolution, it may have not competed too heavily with the large contemporary dicynodonts.
The key is Shringasaurus’s neck, which was long enough for it to access foliage in tree branches unavailable dicynodonts.
Indeed, Shringasaurus may have been one of the first high browses, specializing in foraging from the tops of trees.
Therefore, while its horns may make it more reminiscent of ceratopsians, early sauropodomorphs like Plateosaurus may be better analogues for how Shringasaurus lived,
meaning it convergently evolved features similar to two different groups of dinosaurs.
Of course, the ceratopsians-like horns were Shringasaurus's most iconic trait.
Attached to the top of the head, the horns pointed upward and curved forward over most its short skull.
The horns have a rough texture, which usually indicates of the presence of a keratinous covering. Therefore, like those of ceratopsians, Shringasaurus horns were probably longer in life.
Intriguingly, the horns are not present in two of the specimens despite the part of the skull that held the horns in the other skulls being undamaged. This means that not all Shringasaurus individuals had their namesake horns.
Additionally, the horns of younger individuals are proportionally smaller than in the larger individuals.
Meanwhile, there is variation within the shape of the horns in the older adults. Such variation is usually observed in traits under sexual selection.
As only some adults possess horns, it would seem they were most likely restricted to one sex, most likely the males.
Shringasaurus’s horns are closest to those of species were males place their horns together and then use them to wrestle against each other.
This suggest that male Shringasaurs engaged in ritualistic dules with one another, with the victor winning the right to mate.
While the participants could have gotten hurt, this would have been a lot safer than using horns adapted for stabbing each other.
However, this also made the horns less useful for defense against predators, but since females apparently lacked them anyway, this implies defense was at best a secondary function.
Such interspecies combat may also explain some of the other differences between Shringasaurus and its close relative Azendohsaurus.
Larger and more muscular males would have had a better chance in such contests, leading to them being selected for.
Evolutionary pressure for larger and larger size may have been what enabled Shringasaurus to become a high browser in the first place.
However, it also may be why it was later replaced by sauropodomorphs dinosaurs.
Its neck was shorter than those of Azendohsaurus and other closely related allokotosaurs, apparently to support its horns and more muscles.
This would mean that, unlike the sauropodomorphs, it couldn’t easily evolve a longer neck to reach more leaves.
Therefore, the very same evolutionarily pressure that may have enabled Shringasaurus to become a high browser in the first place
may have restricted its ability to evolve further in that direction.
Still, while it may not have been an optimal high browser, Shringasaurus was certainly an impressive addition to the Tree of Life.
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