to evidence of hybridization between dorsalis and picta, the Turtle Taxonomy Working Group and the Reptile Database have since followed through with it, although both the subspecific and specific names have been recognized. Fossils Although its evolutionary history—what the forerunner to the species was and how the close relatives branched off—is not well understood, the painted turtle is common in the fossil record. The oldest samples, found in Nebraska, date to about 15 million years ago. Fossils from 15 million to about 5 million years ago are restricted to the Nebraska-Kansas area, but more recent fossils are gradually more widely distributed. Fossils newer than 300,000 years old are found in almost all the United States and southern Canada. DNA The turtle's karyotype (nuclear DNA, rather than mitochondrial DNA) consists of 50 chromosomes, the same number as the rest of its subfamily-mates and the most common number for Emydidae turtles in general. Less well-related turtles have from 26 to 66 chromosomes. Little systematic study of variations of the painted turtle's karotype among populations has been done. (However, in 1967, research on protein structure of offshore island populations in New England, showed differences from mainland turtles.) Comparison of subspecies chromosomal DNA has been discussed, to help address the debate over Starkey's proposed taxonomy, but as of 2009 had not been reported. The complete sequencing of the genetic code for the painted turtle was at a "draft assembled" state in 2010. The turtle was one of two reptiles chosen to be first sequenced. Description Adult painted turtles can grow to long, with males being smaller. The shell is oval, smooth with little grooves where the large scale-like plates overlap, and flat-bottomed. The color of the top shell (carapace) varies from olive to black. Darker specimens are more common where the bottom of the water body is darker. The bottom shell (plastron) is yellow, sometimes red, sometimes with dark markings in the center. Similar to the top shell, the turtle's skin is olive to black, but with red and yellow stripes on its neck, legs, and tail. As with other pond turtles, such as the bog turtle, the painted turtle's feet are webbed to aid swimming. The head of the turtle is distinctive. The face has only yellow stripes, with a large yellow spot and streak behind each eye, and on the chin two wide yellow stripes that meet at the tip of the