Turtles 1 5 



Hyoplastron - Differs from Terrapene and Emydoidea in that C. gutta- 

 ta lacks the hinge components. C. muhlenbergii differs slightly from C. guttata 

 in that the scute overlap is narrower in C. muhlenbergii. Specimens of Trache- 

 mys and Pseudemys that fall within the size range of C. guttata have scute over- 

 laps that are greatly reduced in comparison to C. guttata and the elements exhib- 

 it incomplete ossification. Deirochelys and Chrysemys picta can be separated 

 from Clemmys guttata because the distance between the entoplastron and 

 hypoplastron is ca. 40% greater in adults of the former two genera. Also, in C. 

 picta, the humeral sulcus does not cross dorsally over the scute overlap area. C. 

 insculpta exhibits incomplete ossification when elements fall within the size 

 range of C. guttata. 



Hypoplastron - This element can be separated from other genera of 

 emydid turtles by the lack of hinge components (separating it from Terrapene 

 and Emydoidea), or by its posterior width being greater than its length (separates 

 it from Trachemys and Pseudemys). Holman (1977) gives characters used to sep- 

 arate this element from C. muhlenbergii and C. insculpta. 



Xiphiplastron - Separation of this element from C. picta is listed under 

 that species. It can be separated from C. muhlenbergii and C. insculpta in that the 

 posterior edge is generally squared off rather than tapering to a point, as in the 

 other two species. However, some specimens of C. guttata do exhibit a pointed 

 condition. These still can be separated from C. muhlenbergii because the area 

 where the abdominal muscle attaches to the xiphiplastron is more pronounced. 

 C. insculpta can also be separated from C. guttata because, in the area where the 

 anal sulcus crosses onto the scute overlap area, the xiphiplastron is deeply 

 notched, being greatly reduced or lacking in C. guttata. 



Entoplastron - In C. guttata the humero-pectoral sulcus crosses the 

 entoplastron within the anterior half of that element. In C. muhlenbergii the 

 humero-pectoral sulcus may cross the entoplastron at its posterior extremity, but 

 typically it does not cross the entoplastron at all (Bentley and Knight 1993). 

 These fossil entoplastra are tentatively assigned to C. guttata, and not C. insculp- 

 ta, because this element is generally more robust in C. insculpta and the humero- 

 pectoral sulcus crosses the entoplastron more posteriorly in C. insculpta than in 

 C. guttata. 



Costal - Characters used to differentiate costal elements from C. picta 

 are described in that section. Costals of Clemmys guttata differ from C. muh- 

 lenbergii in having substantially more curvature. The dorsal surface of costals in 

 C. guttata is smooth, lacking any exterior bulges or sculpturing common to adult 

 C. muhlenbergii, C. insculpta, Deirochelys, Trachemys, and Pseudemys. The 

 costals of Emydoidea, Trachemys, and Pseudemys exhibit immature traits when 

 they are within the size range of C. guttata. Terrapene has deeply incised sulci, 

 and its elements tend to be more acutely angled proximally and exhibit "bul- 

 bous" sculpturing. 



