Compsognathidae

Compsognathidae is a small family of theropod dinosaurs characterized by their diminutive size and slender build. The best known member is Compsognathus longipes from the Late Jurassic of Europe, with Sinosauropteryx prima from the Early Cretaceous of China often discussed as a member in older classifications. The precise composition of the family has varied among researchers, and some taxa have been reassessed as our understanding of relationships among small theropods has evolved.

In terms of classification, compsognathids are generally considered small theropods, and many analyses place them among the coelurosaurian theropods. However, their exact phylogenetic position remains a matter of debate. The status of Sinosauropteryx within Compsognathidae has been particularly fluid in some studies, reflecting broader uncertainties about early coelurosaur relationships.

Anatomically, compsognathids were among the smallest non-avian theropods, typically under a meter in length. They possessed lightweight skeletons, long hind limbs, and elongated tails, with teeth adapted for small prey. Notably, Sinosauropteryx provides important evidence of feather-like structures in non-avian dinosaurs, indicating that plumage evolved early in theropods, though the fossil record for other members is less clear on this point.

The fossil record for Compsognathidae spans Europe and Asia, with Late Jurassic deposits in Europe and Early Cretaceous sites in China. Their small size and presumed agility suggest a lifestyle as quick, small-predator or insectivore specialists, hunting tiny vertebrates and invertebrates in their respective ecosystems.