Turtles Modern Anapsids General Characters Evolved at least 200 MYA. All are anapsids. None have teeth - they have a keratinous sheath which grows continuously, just as in birds.
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Occur in Australia and S. America.
All are carnivorous.
Matamata may stalk prey, uses a sudden thrust of neck and rapid opening of mouth to create negative presure and capture prey.
They are highly aquatic & good swimmers.
Generally, lack mesoplastral elements.
Have cervical scute on carapace.
Reduction/loss of neural bone.
Nasals & vomers usually present.
Premax & dentaries unfused.Pleurodira: Chelidae
angular bone of lower jaw touches meckel’s cartilage.
the opposite.Cryptodira: Differences between Testudinids and Emydids
This suggests that the bodies of Pareiasuars are broader and flatter than originally thought.Turtle History
Most basal amniotes, including nyctiphruretians and procolophonoids have 5 cervical vertebrae and 20 dorsal vertebrae.Turtle History
All turtles have 8 cervicals and 10 dorsals.Turtle History
5 or 6 dorsals were lost in the lineage leading to sclerosaurus, pareiasaurs, and turtles.
In the transition to turtles, there was an increase in the number of cervicals and a reduction in the number of dorsals.
This suggests that the pectoral girdle shifted posteriorly about 3 vertebrae in turtles, and that cervicals 6 to 8 in turtles are modified dorsals.Turtle History
the major line of neck flexion in pleurodires and cryptodiran turtles is between cervical 5 and 6 (perhaps the old cervical/dorsal boundary).
Cervicals 6, 7, and 8 usually work as a single rigid unit.
In pareiasaurs, the transverse processes on the 5 cervical centra are ventral, on the first 3 dorsals they gradually assume a more dorsal position.
In the earliest turtle, proganochelys, this change occurs at cervicals 6, 7, and 8.Turtle History
A similar pattern is seen with the pelvic girdle in pleurodires.Turtle History