Oxalaia: Brazil’s New, Giant Spinosaur

Paleontologists have not found much of Oxalaia quilombensis. A fragment of the snout and a portion of the upper jaw are all that is known of this dinosaur. Even so, those two parts are enough to know that Oxalaia was one of the peculiar predatory dinosaurs known as spinosaurs, and a giant one at that.

Just described by Alexander Kellner, Sergio Azevedo and colleagues in Annals of the Brazilian Academy of Sciences, the new dinosaur was found in Late Cretaceous deposits of northeastern Brazil dating back to about 95 million years ago. The portion of the snout alone confirms that it was one of the spinosaurs. Unlike other predatory dinosaurs with heavy, broad heads, the spinosaurs had elongated, crocodile-like jaws, with the upper jaw ending in a spoon-shaped rosette. Oxalaia had the same snout shape, and using this fragment along with skull proportions of better-known spinosaurs, Kellner and co-authors estimate that this dinosaur would have had a skull about four and a half feet long.

Oxalaia would have been a giant among spinosaurs. Compared with the spinosaur fossils previously found in slightly older rock in Brazil—given the names Irritator and Angaturama, though likely representing the same dinosaur—Oxalaia was certainly the biggest type of this dinosaur found in South America. Only spinosaurs from Africa—such as Suchomimus and Spinosaurus—were the same size or larger.

Frustratingly, our knowledge of Oxalaia is so incomplete that it is difficult to know what the entire animal looked like. The fossils recovered so far are most similar to those of Spinosaurus, but there is not yet a way to tell whether the new spinosaur from Brazil had a sail on its back or how it compared to its close relatives. Additional Oxalaia bones may be difficult to find. The site where the two skull fragments were found is dominated by isolated bones that are often quickly destroyed by the elements once exposed. Now that paleontologists know what to look for, though, perhaps researchers will be able to accumulate more bits and pieces of Oxalaia.

References:

KELLNER, A.; AZEVEDO, S.; MACHADO, A.; DE CARVALHO, L.; HENRIQUES, D. (2011). A new dinosaur (Theropoda, Spinosauridae) from the Cretaceous (Cenomanian) Alcântara Formation, Cajual Island, Brazil Anais da Academia Brasileira de Ciências, 83 (1), 99-108

Riley Black | | READ MORE

Riley Black is the author of The Last Days of the Dinosaurs and many other books. She is a science correspondent for Smithsonian magazine covering fossils and natural history, and she writes about the prehistoric past for a variety of publications.