Mirasaura: Beast of the Week

 This week we will be checking out a newly published and super unique little creature, Mirasaura grouvogeli!

Watercolor life reconstruction of Mirasaura grouvogeli by Christopher DiPiazza.

Mirasaura was a reptile that lived in what is now France, during the late Triassic period, 247 million years ago.  Adults of this species may have grown to about 8-10 inches (20-25cm), The genus name translates to "Marvelous Reptile".  The species name, grouvogeli, honors Louis Grouvogel, who originally discovered the first fossils of Mirasaura and helped with its excavation. Mirisaura is known from two almost complete, likely juvenile specimens, as well as eighty specimens of isolated parts of the crest structure found on the animal's back.  Some of these isolated crests are much longer than those of the two nearly complete individuals, implying they could have grown larger than the two actual skeletons on the fossil record.  Sadly the limbs and tail from both skeletons are missing, but relatives of Mirasaura had limbs and feet adapted for grasping branches and some had a single claw on the tip of the tail.  

Despite being recently published, Mirasaura was actually discovered back in the 1930s.  Its crest was initially believed to have been a disembodied fish fin, and then an insect wing.  It wasn't until 2019 that it was reexamined and realized to be the elaborate and unusual crest of a reptile.  

Photograph of one of the nearly complete, likely juvenile, Mirasaura specimens.

Mirasaura was a member of a family of interesting creatures called drepanosaurs.  Drepanosaurs were small, tree-dwelling reptiles, that lived only during the Triassic period.  They all exhibit traits similar to modern lizards, in particular chameleons, but are not directly related to them.  Narrow, beaklike snouts with small teeth on the sides of the jaws and a hunched back are traits common to members of this group, including Mirasaura.  Some of them, like Mirisaura, sported flamboyant crests on their backs, which were made of soft, yet rigid structures that were actually extremely similar to feathers.  Thanks to Mirasaura, of which many fossil specimens preserved these soft feather-like structures, it is possible other members of this group, which only preserved bones, had similar crests.  

Possibly the most interesting thing about the crest is the fact that the individual structures that form it are arranged slightly overlapping but in a single file down the midline of the animal, making it not symmetrical.  So far experts do not know exactly why this is.  The exact function of the whole crest is also still a mystery.  Like modern reptiles it may have been a signal to members of its own species for impressing mates or intimidating rivals.  If they sported them before they were fully grown, however, they may have had other uses.  Perhaps they could have been for camouflage, obscuring Mirasaura's outline and making it look more like part of a tree?  We may never know for sure.

Mirasaura may have specialized in eating small insects, rooting them out of crevices in trees with its pointed snout, and then crunching them up with the teeth in the sides of its jaws.  Because it was so small, it would have needed to be weary of many predators when alive, ranging from pterosaurs, to dinosaurs, to early crocodilian relatives, and even early mammals, which were around during the late Triassic.  Because of this, living up in the trees may have been an effective way to minimizing predation.  

References

Calzavara M., Muscio G. & Wild R. (1980). "Megalancosaurus preonensis, n. g., n. sp., a new reptile from the Norian of Friuli". Gortania. 2: 49–63.

Senter, P. (2004). "Phylogeny of Drepanosauridae (Reptilia: Diapsida)". Journal of Systematic Palaeontology. 2 (3): 257–268.

Spiekman, Stephan N. F.; Foth, Christian; Rossi, Valentina; Gascó Martín, Cristina; Slater, Tiffany S.; Bath Enright, Orla G.; Dollman, Kathleen N.; Serafini, Giovanni; Seegis, Dieter; Grauvogel-Stamm, Léa; McNamara, Maria E.; Sues, Hans-Dieter; Schoch, Rainer R. (2025-07-23). "Triassic diapsid shows early diversification of skin appendages in reptiles".