Aardonyx

Chapter • Meet the dinosaur

Overview

Aardonyx celestae was a mid-sized plant-eating dinosaur from the early part of the Jurassic, roughly 199–191 million years ago. The known skeletons belong to animals that had not yet reached full size; they were about six to seven metres long and probably weighed around half a tonne. The body follows an early sauropodomorph blueprint: a long neck carrying a small, narrow head, a deep barrel-shaped trunk, and a long muscular tail held horizontally clear of the ground. The forelimbs were unusually sturdy for such an early herbivore, and the thumb carried a large curved claw — the claw that gave the animal its name. What made Aardonyx famous is the way it moved. Its hind limbs still did most of the work and it could walk and run on two legs, but the skeleton shows clear signs that the arms had begun to bear weight. The forearm bones sat closer together, the elbow could be locked more firmly, and the hand could take a downward load in a way that does not work in strictly bipedal relatives. Researchers therefore describe Aardonyx as a transitional animal that could drop onto all fours, walking with a wide-gauge stance in which the limbs were held further from the body midline than in later, more pillar-legged sauropods. Aardonyx ate plants. Its jaws were narrow and lacked the fleshy cheeks seen in many early herbivorous dinosaurs, which means the mouth could open very wide and food was swallowed in bulk rather than being carefully chewed. Digestion happened instead in a capacious gut, exactly as in the true sauropods that followed. The long neck allowed browsing at several heights, from ground level up to branches a few metres above the head — conifers, ginkgoes, ferns and seed ferns were all likely food. The fossils were recovered on the farm Spion Kop near Senekal in the Free State province of South Africa, in the upper part of the Elliot Formation. The material represents at least two individuals and was described in 2010 by Adam Yates and colleagues in Proceedings of the Royal Society B. The genus name combines Afrikaans "aard" (earth) with Greek "onyx" (claw), and the species name celestae honours Celeste Yates, who prepared much of the bone from the rock.

Chapter • Where it lived

Habitat

Aardonyx lived in southern Africa during the Early Jurassic, in the landscape now preserved as the upper Elliot Formation of the Free State and Lesotho. The setting was semi-arid with strongly seasonal dry spells, cut by intermittent rivers and broad floodplains that laid down sheets of sand and mud. Vegetation was concentrated along the watercourses and consisted of ferns, seed ferns, ginkgoes and conifers. The only known locality is the farm Spion Kop near Senekal, Free State, South Africa.

Chapter • Wild behavior

Behavior & Ecology

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Chapter • Scientific place

Taxonomy