Monkey-Lizard Update: the Skull of Megalancosaurus
10:31 pm
Reconstruction of the skull of Megalancosaurus preonensis,
after Renesto & Dalla Vecchia, 2005. Fig 5.
Silvio Renesto & Fabio Marco Dalla Vecchia have recently published the first detailed description of the skull of a Monkey-Lizard.* The holotype of Megalancosaurus preonensis—a fairly well-known arboreal reptile from the Triassic of Italy—consists of two slabs that each preserve part of the front half of one individual, including a complete but split skull. This skull shows the head to be triangular and somewhat birdlike in profile, but a second, partial skull preserved in a different plane allowed Renesto & Dalla Vecchia to reconstruct the skull in two views—the image to your left is drawn from their reconstruction.
This new dorsal view makes Megalancosaurus look even more birdlike, or as the paper suggests, pterosaur-like. The authors point out that the skull of Megalancosaurus has several features in common with the skulls of early pterosaurs, but admit that it lacks a big one: the antorbital fenestra (a hole between the eye socket and the nose that likely housed some sort of sinus). Megalancosaurus and other monkey-lizards are generally considered to be quite distantly related to pterosaurs, so the similarities that they share might simply be due to convergence—both navigated complex, three-dimensional environments and likely pursued similar prey. Alternately, monkey-lizards might actually be closely related to pterosaurs, and Megalancosaurus simply lost its antorbital fenestra along the way.
After all, it probably needed it like a hole in the head.
*Renesto, S. and Dalla Vecchia, F. M., 2005. “The Skull and Lower Jaw of the Holotype of Megalancosaurus preonensis (Diapsida, Drepanosauridae) from the Upper Triassic of Northern Italy.” Rivista Italiana di Paleontologia e Stratigrafia, 111: 2. pp. 247-257.
The term “Monkey-Lizards,” used with gleeful abandon at the Hairy Museum, is a loose translation of the name Simiosauria, coined by Phil Senter in 2004. Simiosauria technically refers to the group of animals that includes the family Drepanosauridae and all reptiles more closely related to it than to Coelurosauravus (a prehistoric gliding reptile) or modern reptiles. If Senter’s family tree is correct, this works out to include the animals described in the HMNH’s Monkey-Lizard Gallery, which have traditionally been referred to as drepanosaurs or drepanosaurids. This taxonomic footnote is provided for those wishing to learn more about the group—you’ll generally have more luck Googling “drepanosaur” than “monkey lizard”.
Thanks to Prof. Silvio Renesto for bringing this paper to my attention.
[...] The fossil, described by Dr. Silvio Renesto (previously mentioned here for his work on Triassic “Monkey-Lizards”), preserves a partial skeleton of Tanystropheus that includes the first reported example of the animal’s soft tissue. A few traces of skin show that Tanystropheus had subrectangular, non-overlapping scales on at least part of its body. But even more intriguing are the “wide patches of black material” preserved around the base of its tail. [...]
Dear Hairy Museum,
Drepanosaurus and kin are such nifty critters, and the term “mokey lizard” just seems to fit. I’ve been calling them “monkey lizards” informally for awhile, and after publishing the J. Syst. Palaeont. paper I wondered whether anyone else would pick up on “monkey lizard” and start using it. It is very gratifying to see “monkey lizard” all over your site! Whether the phylogeny in the paper is widely accepted or not, the best part of having had that paper published is the discovery that someone else likes the term “monkey lizard”–and the animals themselves–as much as I do.
A toast to monkey lizards and kindred spirits!
–Phil
P.S. Another toast to nicknaming prolacertiforms “sauropod elves,” because of their long necks.