Limusaurus

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Ceratosauria > Neoceratosauria > Abelisauroidea > Noasauridae > Elaphrosaurinae

Overview: Animals often go through pronounced physical changes as they age, but among the Dinosauria, Limusaurus is one of the more extreme examples of this. Fossil material belonging to the animal was first discovered in the early to mid-2000’s, in what is today the region of Xinjiang, in western China. Multiple specimens were found, notably of different growth stages, representing a decent amount of fossils. Limusaurus received its official description in 2009, published by the renowned Chinese paleontologist Xu Xing, among others. Its generic name is a combination of both Latin and Greek, meaning “mud lizard”, referring to the mudstone found encasing its remains. This appears to have been the remnants of a prehistoric mire, which trapped these Limusaurus specimens, leading to their deaths and eventual fossilization. This mudstone is a part of the Shishugou Formation, with those specific layers dated to the early part of the Late Jurassic. Limusaurus had to deal with a few predators like Guanlong, Sinraptor, and possibly Monolophosaurus.

Limusaurus was a fairly small theropod dinosaur, measuring around or a little over two meters long as an adult. It had a slender build, a fairly long neck, and quite tiny forelimbs. The skull of the adults had narrow, toothless jaws. Most notable, however, were the jaws of the juveniles. As we would expect, younger specimens had comparatively larger heads with stubbier proportions and large eyes, but they also had teeth. Limusaurus, it seems, started out with teeth, but would lose them as it grew, replacing them with a beak. This could also indicate a change of diet, with juveniles eating an assortment of insects or small vertebrates, while adults were omnivorous or even herbivorous. The genus belongs to an odd family of ceratosaurs called the Noasauridae and, more specifically, to a subfamily called the Elaphrosaurinae. Other related noasaurids may’ve had a similar change when reaching adulthood. The tiny arms seen on Limusaurus actually match a trend seen among most of the derived ceratosaur lineages, which tended to have ever smaller forelimbs.