2016-12-13 10:23:23
A few years ago at the Zoo we talked about fossils of apes, those arboreal reptiles that lived in the Triassic period. In that episode, focused on three species from an archipelago in the Tethys Sea, in present-day Italy, Drepanosaurus, Megalancosaurus and Vallesaurus, we already said that other species inhabited other parts of the world at the same time. The one we bring today, Hypuronector, lived in the Upper Triassic, about 215 million years ago, further west, in the heart of the Pangea continent, in what is now New Jersey.
Hypuronector is a quadrupedal reptile about twelve centimeters in length, slender and light, with a long and flexible neck and long and graceful legs, with prehensile fingers ending in long, narrow and sharp nails. The head, like that of other apes, is triangular, similar to that of birds. But also, Hypuronector does not have teeth like other apes, but a pointed beak, like a bird’s.
Dozens of specimens of this fossil species have been found, but none are complete. Their appearance and way of life is subject to controversy. Although these fossil remains have been known for decades, the species was not described until 2001.
The most important difference between Hypuronector and the rest of the apes is the tail. Hypuronector’s tail is very long and broad, flattened in the vertical plane, shaped like a leaf or paddle, and tilted upwards. The chevrons, special bones that project downward from the tail vertebrae and provide rigidity while protecting nerves and blood vessels, are especially large.
Hypuronector means “high-tailed swimmer”, because at first it was thought, due to the shape of the tail and because its fossil remains were found at the bottom of an ancient lake, that it was an aquatic reptile that swam with lateral movements of the tail. such as salamanders and crocodiles. But there are many problems with this hypothesis. The tail is too rigid and its vertebrae are too delicate to withstand the force required to move through the water, and the powerful caudal musculature necessary to move it does not appear to be present. The legs are not short and broad, as in other aquatic or semi-aquatic animals, but rather long and graceful. Also, the front ones are longer than the rear ones. Hypuronector was probably arboreal like its relatives.
Perhaps the tail was just an ornament, with no involvement in the animal’s way of life. Or maybe not. The proportions of the legs, especially the long front legs, suggest that it could be a gliding animal, similar to a flying squirrel, with webbing between the legs. In this case, the long, flat tail could serve as a rudder, to stabilize the glide and even modify the trajectory to some extent.
But Hypuronector’s anatomy isn’t all that different from that of other apes. Simiosaurs had many features that would have been useful for flight: a relatively large brain, binocular vision, a light skeleton, a rigid body, and mobile, muscular legs. Perhaps some other species in the group was also capable of gliding; in fact, this possibility has been proposed in the scientific literature in the case of Megalancosaurus. Although these are hypotheses for both species, we know that quite a few climbing animals are capable of gliding: frogs, lizards, marsupials, squirrels, colugos… If so many different groups have achieved it, it doesn’t seem like a very difficult evolutionary step to take. Now all that remains is to find the definitive evidence in the fossils. That’s how science works.
#Cienciaes.com #Hypuronector #gliding #ape