Protostegidae

Live reconstruction of Protostega gigas, an up to 3 meters long Protostegiden from the Upper Cretaceous of Kansas

• North America, South America,
• Eastern Asia, Western Europe,
• Australia

The Protostegidae are an extinct family of turtles ( Testudines ), which together with the still existing sea turtles ( Cheloniidae ) and leatherback turtles ( Dermochelyidae ) sea turtles relatives ( Chelonioidea ) form.

Until now, fossils of five different genera known. These include species of the genera Santanachelys, Notochelone, Desmatochelys, Chelosphargis and the eponymous Protostega. The oldest fossils found so far of this group is Santanachelys gaffneyi from the Santana Formation in eastern Brazil. It dates from the early Cretaceous period and is about 110 million years old. The largest member of this group is up to 4.5 m long Archelon from the Upper Cretaceous (Campanian ) of North America.

System

Based on a comparison of a total of 104 features of the skeletons of various extinct and still living sea turtles relatives and some species outside of this taxon ( outgroup comparison) a cladistic pedigree analysis of the first to describe the type Santanachelys gaffneyi performed in order to classify them within the system of sea turtles. The analysis was performed with the aid of the PAUP ( phylogenetic analysis using parsimony ) known software and came to the following result ( Simplified), after whom the family relationships are clarified within the Protostegidae:

Santanachelys gaffneyi

Archelon Ischyros

Other Protostegidae ( Notochelone, Desmatochelys )

Leatherback turtles ( Dermochelyidae )

Genuine sea turtles ( Cheloniidae, now living and fossil species)