Agassiz, 1857
Slider turtles
Recognition
The eight species of slider turtles in this genus occur from North America to northern and central South America and on several Caribbean islands and the Bahamas, making this one of the widest ranging of all turtle genera. At times it has been included in the genera Chrysemys or Pseudemys, but Seidel and Smith (1986) have presented sufficient evidence to show it is a separate genus. The carapace is oval, moderately domed (especially in females), posteriorly serrated, contains a medial keel, and has neurals that are hexagonal and shortest anteriorly. Carapacial pattern often includes yellow stripes or dark-centered ocelli. There is a tendency for older males to become melanistic, and females are usually larger than males. The plastron is hingeless, the axillary and inguinal buttresses are short to moderately long, and the entoplastron lies anterior to the humero-pectoral seam. The skull is moderate in size with a complete temporal arch, and the orbito-nasal foramen is much larger than the posterior palatine foramen. The cranium is shallow anterior to the basisphenoid (30-34% of the condylobasal length). The lower parietal process touches the palatine, and the posterior pterygoid touches or is very near the exoccipital. Triturating surfaces of the lower jaws are narrow, and an anterior cusp is absent from the median ridge on the upper jaw. No tuberculate denticles occur on the triturating surface. The upper jaw is usually medially notched, the lower jaw rounded. There are three phalanges in the 5th toe, and the toes are webbed.
Barbour and Carr (1941) and Williams (1956) thought the island series to be derived from mainland populations of Trachemys scripta ornata which may have been blown to their respective islands during successive hurricanes.
Species identification
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