Description and Classification

Altispinax was a bipedal predator, meaning it walked on two legs. Based on its known vertebrae, scientists estimate it could have been a large dinosaur, possibly reaching lengths of around 8 to 10 meters (26 to 33 feet). Its most striking feature was the series of extremely elongated neural spines on its dorsal (back) vertebrae. These spines were much taller than the main body of the vertebrae, suggesting they supported a prominent structure along its back, perhaps similar to a ridge or a low sail, though different in form from the sail of dinosaurs like Spinosaurus.

The classification of Altispinax has been debated due to the fragmentary nature of its fossils. It belongs to the group Tetanurae, which includes most theropod dinosaurs, such as Allosaurus and Tyrannosaurus rex. Some researchers suggest Altispinax might be related to the carcharodontosaurians, a group of large predatory dinosaurs that includes giants like Carcharodontosaurus and Giganotosaurus. Dinosaurs like Concavenator, which also had somewhat elongated vertebral spines, are part of this group. However, without more complete fossil material, its precise placement within the theropod family tree remains uncertain.

The history of Altispinax’s naming is complex. The fossil vertebrae that define the genus were first described in the 19th century and were initially assigned to other dinosaur genera, including Megalosaurus. It was later recognized as a distinct type of dinosaur, leading to the establishment of the genus Altispinax.

Distinguishing Features

Altispinax is primarily recognized by the following features, based on its known fossils:

• Extremely tall neural spines on its dorsal vertebrae, significantly higher than the vertebral body (centrum) is long.
• These spines likely formed a prominent ridge or low sail-like structure along its back, though its exact shape and extent are unknown.
• The structure formed by these spines was different from that seen in other “sail-backed” dinosaurs like Spinosaurus or the American theropod Acrocanthosaurus.

Paleoenvironment and Diet

Altispinax lived during the Early Cretaceous period, specifically in the Valanginian to Hauterivian stages. Its fossils have been found in the Wadhurst Clay Formation of the Wealden Group in southern England. During this time, the area was a complex environment of rivers, lakes, lagoons, and wooded plains, with a generally warm and humid climate.

This ecosystem supported a diverse range of other dinosaurs. Altispinax would have shared its habitat with herbivorous dinosaurs such as the iguanodontian Barilium, the large sauropod Pelorosaurus, and armored dinosaurs like Hylaeosaurus. As a large theropod, Altispinax was a carnivore. It likely preyed upon these plant-eating dinosaurs and other animals available in its environment. Its diet would have been typical of a large predatory dinosaur of its time, hunting or scavenging other suitably sized animals.

Significance and Ongoing Research

Altispinax is significant because it represents one of the European theropods from the Early Cretaceous that developed unusual vertebral structures. It adds to our understanding of the diversity and evolutionary experimentation that occurred within theropod dinosaurs. The function of its tall neural spines is still a topic of discussion. Possible uses include display to attract mates or intimidate rivals, species recognition, or perhaps even to make the animal appear larger.

Ongoing research on Altispinax largely focuses on trying to clarify its evolutionary relationships with other theropods. Because the known fossil material is so limited—consisting mainly of a few vertebrae—it is challenging to determine its exact place in the dinosaur family tree. Paleontologists compare its bones with those of other theropods, especially those with similar elongated neural spines, like Concavenator from Spain or Becklespinax, another English theropod which has sometimes been confused with Altispinax. The discovery of more complete fossil remains of Altispinax would be crucial for a better understanding of its anatomy, appearance, and lifestyle, shedding more light on this intriguing “high-spined” dinosaur of ancient Europe.