Oxalaia

Oxalaia (in reference to the African deity Oxalá) is a genus of spinosaurid dinosaur that lived in what is now the Northeast Region of Brazil during the Cenomanian stage of the Late Cretaceous period, between 100.5 and 93.9 million years ago. Its fossils were found in 1999 on Cajual Island in the rocks of the Alcântara Formation. The remains of Oxalaia were described by Brazilian palaeontologist Alexander Kellner and colleagues, who named the species Oxalaia quilombensis, referencing the Brazilian quilombo settlements.

Oxalaia quilombensis is the eighth officially named theropod species from Brazil and the largest carnivorous dinosaur discovered there. Some studies suggest it may be closely related to the African genus Spinosaurus.

Although Oxalaia is known only from two partial skull bones, scientists found unique features in its teeth and skull. These traits suggest it had a partly piscivorous (fish-eating) lifestyle, similar to modern crocodilians. It lived in a tropical, forested area surrounded by arid land, which was connected to North Africa when the continents were part of the supercontinent Gondwana.

Discovery and naming

Oxalaia was found in northeastern Brazil, in rocks from the Late Cretaceous period, about 100.5 to 93.9 million years ago. The fossils were discovered in 1999 on Cajual Island. Palaeontologist Elaine Machado was surprised by the well-preserved fossil. She described the discovery as accidental. Usually, fossils from this area are broken because of erosion, but Oxalaia was different.

Oxalaia is one of three spinosaurid dinosaurs found in Brazil. The first fossils of Oxalaia were described in 2011 by Brazilian palaeontologists. The name Oxalaia comes from Oxalá, an African deity brought to Brazil during slavery, and the specific name quilombensis refers to the quilombo settlements founded by escaped slaves on Cajual Island.

Description

The fossils of Oxalaia show it had a long skull, about 1.35 metres (4.4 feet) long. It was smaller than its relative, Spinosaurus, but still one of the largest meat-eating dinosaurs found in Brazil. The front of its snout was wide and had a special shape, helping it fit together with its lower jaw.

Oxalaia had special bones in its upper jaw with holes that may have held blood vessels and nerves. Its teeth were different from older spinosaurids, lacking jagged edges. Instead, Oxalaia had two extra teeth growing in each socket, a feature more common in sharks than in other meat-eating dinosaurs.

Classification

The fossils of Oxalaia look a lot like another dinosaur called Spinosaurus aegyptiacus. But scientists found enough differences to say it is a special kind of dinosaur. These differences are in its skull, like a special shape on the top jaw and extra teeth.

Scientists have studied for years to learn where Oxalaia fits with other dinosaurs. Some think it is close to African spinosaurids. Others think it might be the same as Spinosaurus aegyptiacus. But new research shows that Oxalaia is its own special species. It has its own unique skull features that make it different from other spinosaurids.

Palaeoecology

The Late Cretaceous deposits of the Alcântara Formation were a wet place with tropical forests. These forests had conifers, ferns, and horsetails. Around these forests was a dry or semi-arid land. Many animals lived there. Some of these were dinosaurs, pterosaurs, snakes, molluscs, crocodilians, notosuchids, and fish.

As a spinosaur, Oxalaia would have had big front legs, small back legs, and a ridge or sail on its back. Spinosaurids likely stayed near water and ate water animals. They could also eat land animals if they wanted. Oxalaia’s teeth and skull were good for catching and eating fish. This was similar to the way the modern Indian gharial and alligators eat.