Масиаказавр: хищный динозавр позднего мелового периода Мадагаскара

Noasaurid theropod dinosaur genus from the Late Cretaceous period

Masiakasaurus is a genus of small predatory noasaurid theropod dinosaurs from the Late Cretaceous of Madagascar. In Malagasy, masiaka means "vicious"; thus, the genus name means "vicious lizard". The type species, Masiakasaurus knopfleri, was named after the musician Mark Knopfler, whose music inspired the expedition crew. It was named in 2001 by Scott D. Sampson, Matthew Carrano, and Catherine A. Forster. Unlike most theropods, the front teeth of M. knopfleri projected forward instead of straight down. This unique dentition suggests that they had a specialized diet, perhaps including fish and other small prey. Other bones of the skeleton indicate that Masiakasaurus were bipedal, with much shorter forelimbs than hindlimbs. M. knopfleri was a small theropod, reaching long and weighing
Masiakasaurus lived around 70 million years ago, along with animals such as Majungasaurus, Rapetosaurus, and Rahonavis. Masiakasaurus was a member of the group Noasauridae, small predatory ceratosaurs found primarily in South America.

Remains of Masiakasaurus have been found in the Late Cretaceous Maevarano Formation in northwestern Madagascar and were first described in the journal Nature in 2001. Fragmentary bones comprising around 40% of the skeleton were collected near the village of Berivotra. Several parts of the skull, including the distinctive teeth, were found. The humerus (upper arm bone), pubis, hindlimbs, and several vertebrae were also collected. The new finds did however not allow for a detailed study of its evolutionary relationships among ceratosaurs. With the new material, around 65% of the skeleton is currently known. The first four dentary teeth of the lower jaw project forward, with the first tooth angled only 10° above the horizontal. These teeth are long and spoon shaped with hooked edges. They have carinae, or sharp edges, that are weakly serrated. Serrations are more evident along the rear edge the posterior teeth in the back of the jaw, which are also recurved and laterally compressed (flattened from the side), resembling the less unusual teeth of other carnivorous dinosaurs. The margin of the dentary curves downward so that the alveoli (tooth sockets) of the front teeth are directed forward. In fact, the alveolus of the first tooth is actually situated lower than the bottom edge of the rest of the lower jaw. The lower part of the rear edge of the dentary has a long prong, known as a ventral process. This differs from the situation in abelisaurids, which have a much shorter ventral process. On the other hand, the upper part of the rear edge of the dentary is very similar to that of abelisaurids such as Majungasaurus and Carnotaurus. This part of the bone possesses an array of four small structures, three of which line a socket which connects to the surangular bone at the back of the lower jaw. Although the surangular bone is not preserved, several other bones of the lower jaw are, including a triangular angular bone, a gently curving prearticular bone, and a damaged yet notably concave articular bone. The angular and prearticular formed the lower edge of a large and rounded in the lower jaw (known as a mandibular fenestra) while the articular bone formed the lower part of the jaw joint. A long and tapering hyoid (tongue bone) has also been preserved. The front teeth of the upper jaw are also procumbent, and the margin of the premaxilla curves slightly upward to direct them outward. Unlike the skulls of abelisaurids, which are very deep, the skull of Masiakasaurus is long and low. The lacrimal and postorbital bones around the eye are textured with bumpy projections. Not including the highly modified jaws and teeth, the skull of Masiakasaurus possesses many general ceratosaurian characteristics. Overall, its morphology is intermediate between abelisaurids and more basal ceratosaurs.

Carrano et al. (2002) distinguished two forms of Masiakasaurus, a robust form and a gracile form. The robust morph includes specimens with thicker bones and more pronounced projections for the attachment of ligaments and muscles. The gracile form includes specimens that are more slender and have less pronounced muscle attachments. It also has unfused tibiae, unlike the fused tibiae of the robust form. These two varieties may be an indication of sexual dimorphism in Masiakasaurus, but they may also represent two distinct populations. The holes may also have been the result of an infection.