Melanorosaurus (MEH-lan-or-oh-SAWR-us; “Black Mountain Lizard”) is a genus of early sauropodomorph dinosaur that lived during the Late Triassic period, approximately 227 to 201 million years ago. Its fossils have been discovered in South Africa and Lesotho. The name Melanorosaurus refers to Black Mountain (Thaba ‘Nyama) in South Africa, near where some of the first fossils were found, and was given by paleontologist Sidney H. Haughton in 1924. It was one of the earliest large-bodied herbivorous dinosaurs.

Description and Classification

Melanorosaurus was a large and heavily built dinosaur for its time, reaching lengths of around 8 meters (about 26 feet), although some estimates suggest it could have grown even larger, possibly up to 10 or 12 meters. It likely weighed between 1 to 2 metric tons. It walked on four sturdy, pillar-like legs to support its considerable weight, though its hind limbs were longer than its forelimbs. Melanorosaurus had a relatively small head, a moderately long neck, and a long tail, which helped with balance.

This dinosaur belongs to the group Sauropodomorpha, which includes the later giant long-necked dinosaurs like Brachiosaurus and Apatosaurus. Melanorosaurus is considered a basal (early) sauropodomorph. While sometimes referred to as a “prosauropod,” this term is now generally seen as describing a group of early sauropodomorphs that are not a true natural group. Melanorosaurus is significant as it shows many features that were becoming more common in true sauropods, and it is sometimes placed within its own family, Melanorosauridae, or considered a very early sauropod. It is one of the first dinosaurs to achieve such a large size.

Distinguishing Features

Melanorosaurus had several features that set it apart, especially from other early sauropodomorphs:

• Its considerable size, being one of the largest dinosaurs of the Late Triassic period.
• A robust and heavily built skeleton, more so than many contemporary sauropodomorphs like Plateosaurus.
• A fully quadrupedal (four-legged) stance, although its forelimbs were shorter than its hind limbs, indicating a transition towards the limb proportions of later sauropods.
• The femur (thigh bone) was notably straight and massive, adapted for supporting great weight.
• Feet were relatively short and broad.

Paleoenvironment and Diet

Melanorosaurus lived in what is now southern Africa during the Late Triassic. The landscape was likely semi-arid, meaning it was quite dry but had seasonal rains. These rains would have supported areas with conifer trees, ferns, and horsetails, especially along rivers and floodplains. Fossil remains of Melanorosaurus are often found in the Elliot Formation, which preserves these ancient environments.

As a large sauropodomorph, Melanorosaurus was a herbivore, feeding on plants. Its size meant it needed to eat a lot of vegetation each day. Its teeth were likely simple and leaf-shaped, good for stripping leaves and other plant material from branches. With its moderately long neck, it could probably browse on vegetation at different heights, from low-growing plants to an extent up into the trees.

Significance and Ongoing Research

Melanorosaurus is a very important dinosaur for understanding the early evolution of sauropodomorphs, particularly the trend towards gigantism. It was one of the first dinosaurs to reach such a large body size, showing that this characteristic of later sauropods like Argentinosaurus began to develop much earlier than previously thought, during the Triassic period. Its anatomy provides valuable clues about how these dinosaurs transitioned from smaller, bipedal ancestors to enormous, four-legged plant-eaters.

Ongoing research on Melanorosaurus continues to refine our understanding of this ancient giant. Scientists are still working to pinpoint its exact position in the sauropodomorph family tree – whether it’s best classified as an advanced non-sauropod sauropodomorph, an early sauropod, or part of its own distinct family. Studies also focus on its locomotion, how it moved, and the details of its growth to such a large size so early in dinosaur history. Comparing Melanorosaurus with other early large sauropodomorphs, such as Antetonitrus and Lessemsaurus, helps paleontologists piece together the story of how the truly giant sauropods came to be.