Florida Chicken Turtle
Chicken turtles are medium (males)-to-large (females) basking turtles & females achieve fair bulk (females roughly on par with female RES, but males smaller than male RES). The carapace has a brown to grey base color with a distinctive reticulate pattern (think ‘irregular chain link fence’). The plastron tends toward plain yellow. There's a single broad yellow stripe down the front of the fore-legs. Between rear leg & tail is vertical striping. They are famous for having very long necks (by U.S.A. standards; they don’t reach true ‘snake neck’ proportions. They do carry the nickname ‘American snake neck’). Some have an upward-angled light stripe from the rear of the mouth to the nose, giving them an upturned snout look (like a hognose snake, but the snout doesn't actually turn up), sort of a smiling expression (vaguely like a male common map turtle). There's a bar or partial bar across the eye pupil.
Florida chicken turtles have the more ornate reticulations & possibly head striping (the 'loudest' coloration). Keith B. described some stereotypical sub-species differences (warning: not all individuals will match these, & integrates are expected):