Coelurosauravus

Credit: Nobu Tamura.

*Coelurosauravus* is an extinct genus of basal Diapsid reptile that lived in Madagascar during the Late Permian.

## History

The only *Coelurosauravus* were collected between 1907 and 1908 by J.M. Colcanap in southwestern Madagascar. It is unknown which exact locality *Coelurosauravus* was found in, but is likely from Mount Eliva near the Sakamena River upstream. They were described by Jean Piveteau (1926) as *C. elivensis*. After description, *Weigeltisaurus* was briefly synonymized as *C. jaekeli*, but was resurrected by a 2015 analysis. Robert L. Carroll (1979) placed one *Coelurosauravus* into a new genus, *Daedalosaurus* based on supposed differences, but has been found to be a synonym.

## Description

The skull of *Coelurosauravus* is the smallest of all Weigeltisaurids, being 3.5 centimeters long, around half those of other Weigeltisaurid genera. The skull was covered in ornamentation, made of lower tubercles and spikes, with a horned frill projecting from the squamosal. The teeth are simple and densely packed in a row, decreasing in size posteriorly. ~29 pairs of long, rod-like bones stretch from its sides, which are probably modified gastralia or a novel dermal ossification. These support a wing membrane, which allowed it to glide. The ornamentation lining the skull was likely for display.In 2022, a detailed redescription of the postcrania of this taxon revealed a shorter neck and longer trunk than previously thought. They also described a 4th manual digit phalanx, being the third weigeltisaurid to have this apomorphous trait revealed. They suggested that the longer reach provided by digit V of the manus may align with abduction, allowing for grasping of the leading patagium edge at the midpoint, This is supported by a similar character in *Draco*. The patagial spars are likely to deviate from the gastralia, which forms an attachment of the patagia below the center of gravity, thus increasing maneuverability via destabilization. Flight stability was provided by the dihedral angling of the patagia and aid from the arms.

## Paleobiology

   The rods start at the lower-lateral surface, with the furling and unfurling of the membrane probably controlled by muscles in the abdomen. *Weigeltisaurus* has a high degree of flexibility in these, like in gliding lizards. The wings are oriented upwards to increase stability. Gliding lizards use their forelimbs to grab the membrane, steering with them, which has been proposed for Weigeltisaurids. Comparison of *C. elivensis* and other similar extinct taxa to the extant Draco in a 2011 study find *Coelurosauravus* to be less efficient at gliding; having a wing loading of ~107.9 N/m2, 4.5 times greater than *Draco* and a large drop in height for every glide. This corresponds with a steep descent of 45+°. Weigeltisaurids were long believed arboreal, mostly due to their gliding abilities, but the non-patagial postcrania were often disregarded. In 2022, a redescription of the postcrania suggest that the long, gracile and dorsoventrally-compressed body, equally long fore- and hindlimbs and long autopodia suggest a clinging arboreal ecology. It was able to grasp the midpoint of the patagia, who attached below the center of gravity and thus aiding in maneuverability, to control gliding flight. It was one of the first known tetrapods to bear an adjustable flight apparatus and one of the first to have an arboreal lifestyle supported by anatomy. Weigeltisaurids were found to be one of the few tetrapod groups to have evolved hyperphalangy with climbing and gliding.

### Diet

Though no stomach contents are directly preserved, it is presumed an arboreal insectivore due to its teeth seeming to be adapted to piercing the arthropod's cuticle.

## Notable Specimens

* IP 1908-11-21a: The holotype *C. elivensis*; a poorly-preserved cranium and partial postcrania.
* IP 1908-11-22a and IP 1908-11-23a: A fragmentary skull and the anterior of the skeleton.
* IP 1908-5-2 and IP 1908-5-2b: Once assigned *Daedalosaurus*, containing partial postcrania (with gliding structures) and cranial fragments.

## Paleoecology

The Lower Sakamena is a wetland, found within a north-south-oriented rift valley, maybe comparable to Lake Tanganyika. It was temperate, warm and humid at deposition time, possibly having seasonal rainfall and monsoons. Flora includes equisetaleans, seed ferns and glossopterids. Palaeoniscoids, parareptiles, neodiapsids, rhinesuchids, theriodonts and dicynodonts were present.

## References

* https://en.wikipedia.org/wiki/Coelurosauravus
* https://www.tandfonline.com/doi/full/10.1080/02724634.2022.2108713