Dromicosaurus

Lore & Background

The only known specimen of Dromicosaurus was discovered by paleontologist Egbert Cornelis Nicolaas van Hoepen at Noupoortsnek, near the road from Bethlehem to Clarens. Weathering had already freed most of the two pubes from the surrounding rock. During excavation, the shaft of the tibia scattered into pieces, but van Hoepen was able to immediately fit and glue the bone back together. The specimen became part of the collection of the Ditsong National Museum of Natural History in Pretoria under specimen number TM 119 (or TM 119a).

Van Hoepen described the specimen in 1920 as the new genus and species Dromicosaurus gracilis. The name derives from Ancient Greek δρομικός 'quickly walking' and sauros 'lizard', selected because 'the slender leg must have enabled the animal to go quicker than

Reader's Guide

Dromicosaurus represents a historically significant but taxonomically uncertain sauropodomorph from the Late Triassic or Early Jurassic of South Africa. Its fragmentary remains, discovered by van Hoepen in the Elliot Formation, have been repeatedly reassigned to species of Massospondylus, reflecting the difficulty of classifying incomplete dinosaur material from this region. The two most recent reviews (Galton 1990; Galton and Upchurch 2004) consider Dromicosaurus an indeterminate sauropodomorph, meaning it cannot be confidently assigned to a known genus or species. This status highlights the challenges in paleontology when dealing with weathered, partial skeletons. Despite its dubious nature, Dromicosaurus contributes to the understanding of early sauropodomorph diversity in southern Africa and the history of their study. The specimen's preservation—with weathering having freed bones and the tibia being glued back together—illustrates the practical difficulties of fieldwork and preparation. Its name, emphasizing quick walking, reflects early interpretations of its locomotion based on slender leg bones.

Did You Know?

• The name Dromicosaurus means 'quick-walking lizard' in Ancient Greek.
• The two most recent reviews list Dromicosaurus gracilis as an indeterminate (dubious) sauropodomorph.

The Excavation at Noupoortsnek

In 1920, the palaeontologist Egbert Cornelis Nicolaas van Hoepen unearthed a fragmentary dinosaur skeleton at a site called Noupoortsnek, situated near the road connecting Bethlehem and Clarens in the Free State region of South Africa. By the time he arrived, natural weathering had already liberated most of the two pubic bones from their enclosing rock matrix, a fortunate circumstance that spared those elements from further damage. The excavation itself was not without challenges: the shaft of the tibia shattered into multiple fragments as it was freed from the stone, but van Hoepen worked quickly to reassemble and glue the pieces back into their original configuration. The recovered material was catalogued under the number TM 123 and entered the holdings of the Transvaal Museum in Pretoria, the institution where van Hoepen was employed at the time. That museum is now known as the Ditsong National Museum of Natural History. The specimen originated from the Elliot Formation, though whether it came from the upper (Late Triassic) or lower (Early Jurassic) portion of that unit remains unresolved.

A Name Built on Slender Legs

When van Hoepen formally described the new genus and species in 1920, he chose the name Dromicosaurus gracilis, drawing on the Ancient Greek words for 'quickly walking' and 'lizard.' His reasoning was straightforward: the hindlimb bones of this animal were notably more slender than those of its contemporary relative Eucnemesaurus, and he believed this lighter build would have allowed the creature to move faster. The femur measured 49.5 centimetres in length, and the humerus was only about half that, indicating a relatively short forelimb. Van Hoepen also noted that the fourth trochanter—the ridge on the femur where leg muscles anchored—sat higher up on the bone than in Massospondylus carinatus, and the proportions of the tibia's lower end differed as well. These anatomical distinctions were, in his view, sufficient to warrant a separate genus. The overall impression was of a gracile, lightly built sauropodomorph whose body plan favoured speed over bulk, a design that set it apart from the heavier contemporaries known from the same South African deposits.

A Century of Taxonomic Disputes

From the moment Dromicosaurus entered the scientific literature, its placement has been contested. Van Hoepen originally assigned it to the Anchisauridae, a group he regarded as clearly separate from the Plateosauridae, though both were then interpreted as theropods—a classification that has since been abandoned in favour of placing them among basal sauropodomorphs. In 1932, Friedrich von Huene argued the animal was closely allied to Massospondylus and Thecodontosaurus, and he went further, suggesting that the high position of the fourth trochanter combined with the short forelimb implied strongly bent knees and a bipedal posture. By 1976, Peter Galton and Michael Cluver had synonymised D. gracilis with Massospondylus harriesi, following an earlier suggestion by John Attridge. Michael Cooper took a different tack in 1981, lumping it under M. carinatus instead. The two most recent reassessments, by Galton in 1990 and by Galton and Upchurch in 2004, sidestepped the synonymy question entirely and listed the specimen as an indeterminate, or dubious, sauropodomorph—a status it retains to this day.

What the Bones Tell Us

The sole known specimen of Dromicosaurus is a partial skeleton of modest but varied content. It includes what van Hoepen identified as an almost complete cervical vertebra, possibly the third in the series, though Friedrich von Huene later reinterpreted this element as a dorsal vertebra. Roughly eight poorly preserved vertebrae from the anterior tail are also present. Among the limb elements, the material includes fragments of the humerus and radius, a weathered femur, and—most notably—the well-preserved right tibia and fibula. The pelvic bones are represented by two pubes in good condition alongside more fragmentary ischia. Several foot bones survive as well, including the first three metatarsals. The overall preservation is uneven: some elements like the pubes and lower leg bones are in excellent shape, while others such as the tail vertebrae and the femur are heavily degraded. This patchwork of bones, all recovered from a single site in the Free State, constitutes the entirety of what is known about this enigmatic Late Triassic or Early Jurassic dinosaur.

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