Prolacerta

Prolacerta Temporal range: Early Triassic
Reconstruction of Prolacerta broomi
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Family:	†Prolacertidae Parrington, 1935
Genus:	†Prolacerta Parrington, 1935
Type species
†Prolacerta broomi Parrington, 1935

Prolacerta (meaning "before lizard" in Latin) is an extinct genus of archosauromorph reptile from the Early Triassic. It includes one species, Prolacerta broomi, named in 1935 from the Karoo Basin of South Africa. Remains of Prolacerta have also been found from Antarctica. Prolacerta is traditionally classified as a member of Prolacertiformes, a group of basal archosauromorphs that also includes protorosaurids and tanystropheids. However, most recent phylogenetic analyses place it in a more derived position as the sister taxon of Archosauriformes, thereby making the traditional Prolacertiformes a polyphyletic group. "Prolacertiformes" is currently restricted by definition to Prolaceta alone, and the rest of the traditional prolacertiformes are known as protorosaurs.

Classification

The paleontologist Francis Rex Parrington named Prolacerta broomi in 1935 on the basis of a skull from South Africa, and considered it a transitional form between early diapsids and lizards, although he classified it within the archosaurian group Thecodontia. In 1945 Charles Lewis Camp classified Prolacerta as an early lepidosaur more closely related to lizards than to archosaurs. Camp grouped Prolacerta with Protorosaurus, and both would later become part of a larger group of reptiles called Prolacertiformes. Up until the 1980s, Prolacerta and Protorosaurus were often placed in a group called Eosuchia, which consists of early reptiles that were thought to be ancestral to both archosaurs and lepidosauromorphs. As phylogenetic analyses became common in the late 1980s and 1990s, Prolacerta was generally considered a member of Prolacertiformes, which was placed at the base of Archosauromorpha and included other Triassic reptiles such as tanystropheids and Macrocnemus.

Several features in the skull of Prolacerta link it with the earliest archosauriforms. Its teeth are ankylothecodont, meaning that they implant deeply into the jaw and fuse to the bone. More advanced archosaurs from later in the Triassic had thecodont teeth that were loosely implanted into sockets. Prolacerta has a gap between the premaxilla and maxilla bones of the upper jaw and a slightly downturned snout that is also seen in the rhynchosaur Mesosuchus and the early archosauriform Proterosuchus.