Description and Classification

Nqwebasaurus was a relatively small, bipedal dinosaur. It is estimated to have been about 90 centimeters (3 feet) long and might have weighed only a few kilograms. It had a slender build with long legs, suggesting it was a nimble and quick runner. One of its most notable features was its hands; Nqwebasaurus possessed a long first metacarpal (the bone in the palm leading to the thumb) and a semi-opposable first digit, or thumb. This suggests it might have had some grasping ability, which is unusual for many theropods of its time. The skeleton also included vertebrae from the neck, back, and tail, parts of the forelimbs and hindlimbs, and, significantly, gastroliths (stomach stones).

When first discovered, Nqwebasaurus was considered to be one of the earliest and most primitive members of the Ornithomimosauria, a group of ostrich-like dinosaurs. However, further studies have suggested that its features are more broadly characteristic of basal (primitive) coelurosaurs, the larger group of theropods that includes tyrannosaurs, ornithomimosaurs, and birds. Its exact placement is still debated, with some researchers placing it near the base of Ornithomimosauria, while others consider it a non-ornithomimosaurian coelurosaur, possibly related to dinosaurs like Compsognathus or as a basal maniraptoriform. This makes Nqwebasaurus an important species for understanding the early evolution and diversification of coelurosaurian dinosaurs.

Distinguishing Features

Nqwebasaurus can be distinguished from other theropod dinosaurs by several key characteristics:

• A relatively long first metacarpal (thumb bone) in its hand.
• A partially opposable pollex (thumb), which might have aided in grasping food.
• The presence of gastroliths preserved in its abdominal cavity, indicating its dietary habits.
• Its small body size, especially for an Early Cretaceous theropod from Gondwana.
• Certain features of its ankle bones, including the fusion of the astragalus and calcaneum to the tibia.

Paleoenvironment and Diet

Nqwebasaurus lived in what is now the Eastern Cape Province of South Africa, in an environment represented by the Kirkwood Formation. During the Early Cretaceous, this region depicted a floodplain environment with meandering rivers, lakes, and vegetated areas. The climate was likely temperate to subtropical, with distinct wet and dry seasons. Nqwebasaurus shared this habitat with other dinosaurs, including the large sauropod Algoasaurus, the stegosaur Paranthodon, and various ornithopods. The ecosystem also included crocodiles, turtles, and fish.

The discovery of numerous gastroliths (stomach stones) with the skeleton of Nqwebasaurus provides strong evidence about its diet. Gastroliths are stones swallowed by animals to help grind tough plant material in the digestive system. This suggests that Nqwebasaurus was at least partly herbivorous. Its small size and potentially grasping hands might have allowed it to feed on plants, seeds, or fruits. Some scientists also propose it could have been omnivorous, possibly supplementing its plant-based diet with insects or other small animals.

Significance and Ongoing Research

Nqwebasaurus is a significant dinosaur discovery for several reasons. It is one of the few well-preserved theropod dinosaurs known from the Early Cretaceous of southern Gondwana, offering valuable insights into the diversity and evolution of dinosaurs in this part of the world during a period with a sparse fossil record. Its anatomy, particularly the features of its hand and the evidence of gastroliths, contributes to our understanding of the early evolution of coelurosaurs and their diverse adaptations, including dietary shifts.

Ongoing research continues to focus on refining the exact phylogenetic position of Nqwebasaurus within the Coelurosauria. Detailed comparisons with other early coelurosaurs from both Gondwana and Laurasia are crucial for this. Further investigation into the functional morphology of its hand, especially the semi-opposable thumb, may shed more light on its feeding behavior and ecological role. As paleontological work continues in the Kirkwood Formation, there is always hope for new fossil discoveries that could provide more information about Nqwebasaurus and the ancient ecosystem it inhabited.