================================================================== RECENT _Chrysemys_ | _Chrysemys limnodytes_ | RECENT _Pseudemys_ --------------------+------------------------+-------------------- Not serrated. | Posterolateral | Serrated. | marginals not serrated.| --------------------+------------------------+-------------------- Not notched. | Carapace with broad | Notched. | shallow notch at | | anterior end. | --------------------+------------------------+-------------------- Occasional faint | Plastron does not have | Distinct notch at notch at femoro-anal| a pronounced notch at | femoro-anal suture. suture. | femoro-anal suture. | --------------------+------------------------+-------------------- Posterior lobe of | Posterior lobe of | Posterior lobe of plastron flares | plastron does not | plastron does not laterally. | flare laterally. | flare laterally. --------------------+------------------------+-------------------- Carapace smooth. | Carapace has smooth | Carapace has | contours. | depressions and | | elevations. --------------------+------------------------+-------------------- Old specimens | Seven or eight ridges | Ridges cover occasionally have | on lower half of | costals. five or six ridges | costals. | near border of | Remaining surface of | costals. | costals and neurals | | rugose. | --------------------+------------------------+-------------------- No ridges on | No ridges on | May or may not marginals. | marginals. | have ridges on | | marginals. --------------------+------------------------+-------------------- Nuchal smooth. | Nuchal smooth. | Nuchal has ridges. --------------------+------------------------+-------------------- Carapace not | Probably arched less | Greatly arched. greatly arched. | than in _Pseudemys_, | | but more than in any | | Recent _Chrysemys_. | --------------------+------------------------+-------------------- Keel often present | No keel present. | Keel often present. at birth, but soon | | lost. | | --------------------+------------------------+-------------------- Anterior and | Anterior and posterior | Anterior width of posterior widths of | widths of first | first vertebral first vertebral | vertebral scute less | scute less than scute approximately | than width of second | posterior width, same as width of | vertebral scute.