On the manual morphology of Compsognathus longipes and its bearing on the diagnosis of Compsognathidae

Compsognathus longipes sits at an important point in theropod evolution at the base of Coelurosauria . Despite its relative completeness and oft-cited morphology, however, the manual morphology has been unclear. This work provides the first detailed study of the morphology of the manus of Compsognathus longipes . It shows that Compsognathus longipes had two fully formed functional digits as well as a reduced, perhaps even non-functional, third digit. That conclusion runs counter to the usual interpretation that Compsognathus longipes had only two phalanges, rather than the expected complement of three, in digit II. This work also identifies a unique suite of metacarpal I morphologies that are used to diagnose a subclade among species often referred to as 'Compsognathidae'. These features are used to construct an apomorphy-based definition of a new clade name: Compsognathidae.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 569–581.