Odontochelys

Odontochelys semitestacea

Odontochelys is an extinct animal that was only just recently discovered (2008). It is pretty darn remarkable find, and represents the earliest Turtle that we know about.. it dates back to the Early Triassic over 220 million years ago!

Odontochelys is a transitional reptile. It shares many characteristics with modern turtles, but also demonstrates traits found in earlier reptiles. It has a plastron, which is the under part of a turtle's shell, but it has no carapace! It also has a turtle-like beak, but there are teeth inside it!

The find is helping scientists figure out how turtles evolved. The previous-oldest-fossil already had a carapace, so discovering a species without one gives clues as to where the shell actually came from. One theory is that shells came from the fusion of osteoderms, which are bony plates of armor in the skin. But Odontochelys has no osteoderms, yet it still has a plastron.

The other theory, which is now looking better, is that the plastron grew first (presumably to protect the aquatic turtles from underside attacks). Once the plastron was in place the turtles eventually evolved extensions from their ribs and backbone that fused together to form a full shell. However, it will be difficult to determine for sure until more transitional fossils are uncovered.

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Status : Extinct for around 220 Millions Years
Location : China
Size : Length up to 9.5in (24cm), Weight up to 4.5lbs (2kg)

Classification : Phylum : Chordata -- Class : Sauropsida -- Order : Testudines
Family : †Odontochelyidae -- Genus : †Odontochelys-- Species : †O. semitestacea