Concavenator

About Concavenator

Discovery at Las Hoyas and the Miracle of "Pepito"

Concavenator was discovered in a beautifully articulated state, with almost its entire skeleton connected, at a fossil excavation site called Las Hoyas in Cuenca Province, Spain. In its native Spain, it is affectionately known by the cute nickname "Pepito".

During the Early Cretaceous period when it lived, this area was a subtropical wetland with distinct dry and rainy seasons. It is thought that the environment spreading there at the time is the reason why such a large dinosaur, measuring 6 meters in length, was preserved so beautifully as a fossil.

During the rainy season, water currents carried sediment over a body that had died and dried up during the dry season, and a layer of microorganisms spreading within the environment completely enveloped the whole body. As a result, not only bones but also traces of skin and scales were preserved.

Features of Concavenator: The Strange "Hump" on its Back

The most eye-catching feature of Concavenator is the triangular "hump" or "sail" structure formed by elongated vertebrae (the 11th and 12th dorsal vertebrae) located slightly in front of the hips. While there are other dinosaurs with sails on their backs, a localized protrusion like Concavenator's is a very unusual shape.

The function of this strange structure is still debated among researchers.

• Display Theory: This theory suggests it was used for communication with peers, displaying to the opposite sex, or claiming territory. Like the crests of modern birds, it might have had conspicuous colors.
• Thermoregulation Theory: It is thought that blood vessels ran through the hump, and this theory suggests it acted as a "heat exchanger", exposing it to the wind to cool the body, or basking in the sun's rays to quickly warm its large body.

In the past, there was also a possibility considered that it was a hump for storing fat, like a camel's. However, camel humps have no bone core, which is different from the shape of Concavenator where the bone itself is elongated, so this theory is currently viewed negatively. It is thought to have been something like a sail of thin soft tissue.

Arm Feathers and Foot Scales: Unexpected Similarities with Birds

Small bumps called "quill knobs" line the forearm bone (ulna) of Concavenator. In modern birds, this is a structure used to firmly anchor the bases of large feathers (flight feathers) to the bone.

There was fierce debate over this discovery, with some researchers arguing that "this is just a muscle attachment scar." However, recent research using CT scans has proven that it is different from a muscle attachment site and that the bone had become distorted during the fossilization process, making the view that it is a "trace of feathers" currently prominent.

Concavenator belongs to a group of large carnivorous dinosaurs called Carcharodontosauridae and could not fly. Therefore, it is thought that these arm feathers were not for flying, but were "ribbon-like ornaments (display organs)" for show.

Concavenator's Fearsome Hunting Method

Concavenator was an apex predator in the rich wetlands of its time. Like its close relatives, it did not have teeth designed to crush the bones of prey, but rather thin, sharp teeth with tiny serrations called "shark-teeth."

It is thought that it specialized in hunting by efficiently slicing through prey's flesh using these teeth and powerful neck muscles, causing fatal massive bleeding. A "lump of bird bones (pellet)," which is thought to have been regurgitated by a dinosaur, has also been found in the same strata, suggesting that Concavenator had a flexible diet, swallowing small birds and reptiles whole in addition to herbivorous dinosaurs.

Concavenator Stamp and Fossil Gallery