''Megalancosaurus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of extinct reptile from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

Dolomia di Forni Formation and Zorzino Limestone of northern

Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...

, and one of the best known drepanosaurids. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''M. preonensis''; a translation of the animal's scientific name would be "long armed reptile from the Preone Valley."

Anatomy

''Megalancosaurus'' was fairly small, its adult length was only about 25 centimeters (10 inches). It was built like a

chameleon Chameleons or chamaeleons (Family (biology), family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 200 species described as of June 2015. The members of this Family (biology), family are best known for ...

and probably lived a similar

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

lifestyle, feeding on insects and other small animals. Even its feet were chameleon like, with two toes being opposed to the remaining three. The tail is long, prehensile, and bears a strange claw-like organ made of fused vertebrae at its end. Its shoulders formed a

withers Withers are the ridge between the shoulder blades of an animal, typically a quadruped. In many species, this ridge is the tallest point of the body. In horses and dogs, it is the standard place to measure the animal's height. In contrast, catt ...

that would have served as an attachment site for especially strong muscles. Some specimens have an opposable digit on the feet. Because not all members of the species appear to bear this digit, it has been speculated that it is an instance of

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

, only being possessed by whichever sex needed a stronger grip on the branch during

copulation Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both.Sexual inte ...

. The head of ''Megalancosaurus'' is superficially very birdlike. The skull was roughly 30 mm long and 12 mm tall. The eyes were large and the snout was narrow. Towards the tip of the snout were two small premaxillary teeth, which were separated by a diastema from at least 22 small maxillary teeth. The orbits were directed anteriorly, suggesting that ''Megalancosaurus'' had good binocular vision. It has been proposed that ''Megalancosaurus'' was capable of gliding, though while not fully ruled out it has largely been dismissed. The two species of ''Megalancosaurus'' were able to coexist by living in different microhabitats such that they did not occupy the same niche.

History

''Megalancosaurus preonensis'' was first described in 1980. Its discoverers interpreted it as an archosaur, based in part on the belief that it had an antorbital fenestra. In 1994, two specimens originally thought to be juveniles of '' Drepanosaurus'' were assigned to the species. This discovery led to the realization that it was a drepanosaurid. Since then, it has been regarded as one of the most derived members of the group.

Related genera

* '' Dolabrosaurus'' * '' Drepanosaurus'' * '' Hypuronector'' * '' Vallesaurus''

References

External links

Hairy Museum of Natural History page on simosaurs
{{Taxonbar, from=Q3079302 Drepanosauromorpha Late Triassic reptiles of Europe Fossils of Italy Fossil taxa described in 1981 Prehistoric reptile genera