Megapnosaurus

Chapter • Meet the dinosaur

Overview

Megapnosaurus rhodesiensis was a small, lightly built predatory dinosaur that lived in southern Africa during the Early Jurassic, roughly 199–188 million years ago. At about 2.2–3 metres long and only 13–32 kilograms in weight, most of its length was taken up by a long stiffened tail and a slender neck. The skull was low and elongated, lined with many small, blade-like, backward-curving serrated teeth. Unlike some of its close relatives it lacked tall head crests, carrying only low ridges along the snout. It stood and moved horizontally, tail held clear of the ground as a counterbalance. Whether it bore any feather-like covering is unknown: no skin impressions are known for Megapnosaurus, so most reconstructions show scaly or bare skin, occasionally with speculative filaments. Its legs were long and slim, and several bones of the ankle and foot were partly fused — the feature that inspired its original name, Syntarsus, meaning 'fused ankle'. The whole build points to a fast, agile runner suited to open ground. Many specimens fall into two forms, one more robustly built and one more gracile. This has often been read as a difference between males and females, but the variation could equally reflect age or simple individual differences, and the question remains unresolved. Megapnosaurus was a carnivore that most likely hunted small prey: early mammal relatives, small reptiles, lizard-like animals, and perhaps the young of larger dinosaurs. Its narrow jaws and knife-edged teeth were far better suited to seizing and slicing small animals than to grappling with big ones. Microscopic growth rings in the bones show that these animals grew quickly in their first years and needed several seasons to reach full size; the oldest individuals studied were around seven years old. The first fossils came to light in the early 1960s in the Forest Sandstone Formation of what was then Rhodesia (now Zimbabwe), and the species was described in 1969 by palaeontologist Michael Raath as Syntarsus rhodesiensis. In 2001 three beetle specialists noticed that the genus name Syntarsus had been used for a beetle since 1869, and they supplied the replacement name Megapnosaurus, 'big dead lizard'. The renaming annoyed many dinosaur researchers because it was done without consulting them. Several workers have since argued that the species belongs in the genus Coelophysis instead, and the naming question is still debated.

Chapter • Where it lived

Habitat

Megapnosaurus rhodesiensis lived about 199–188 million years ago, early in the Jurassic, in what is now Zimbabwe and neighbouring parts of southern Africa. Its fossils come mainly from the Forest Sandstone Formation of the Karoo Supergroup, a deposit laid down in a vast desert of migrating sand dunes. Between the dunes lay seasonal watercourses, oases and damp hollows where animal life gathered. The richest site is the bone bed at the Chitake River, where the remains of many individuals were buried together. Comparable material has also been reported from beds of similar age in South Africa.

Chapter • Wild behavior

Behavior & Ecology

Did you know?

Chapter • Scientific place

Taxonomy