Morphological Variation in Pseudemys 125 



specimen (NCSM 29278) is an adult female (315 mm carapace length) 

 with a "C" on the second pleural scute and broad gular and 

 supratemporal head stripes (13 and 15% of head width) similar to P. 

 concinna or P. floridana. However, it has a relatively long cervical scute 

 (8% of carapace length), well-defined premaxillary notch, and broad 

 xiphiplastron angle (75°) as in P. rubriventris. The skull of that turtle is 

 also clearly intermediate. The vomer marginally contributes to the 

 triturating (alveolar) surface, and the lateral edge of the dentary is 

 weakly serrated. Alveolar width on the dentary surface is 15% of the 

 condylobasal length, and maxillary alveolar width is 21%. In eight P. 

 rubriventris skulls that we examined, the dentary width ranged from 17 

 to 21%, and the maxillary width ranged from 20 to 25%. In 11 P. 

 concinna and P. floridana examined, the dentary width ranged from 13 

 to 16%, and the maxillary ranged from 16 to 20%. The other intermediate 

 specimen (NCSM 14783) is an adult female (254 mm carapace length) 

 without a "C" mark on the second pleural scute and with fairly narrow 

 gular and supratemporal stripes (7-8% of head width) as in P. 

 rubriventris. However, similar to P. concinna and P. floridana, the 

 cervical scute is less than 8% of the carapace length, the lateral angle of 

 the carapace is 95°, and the xiphiplastron angle is 55°. The skull of 

 NCSM 14783 is also somewhat intermediate. Although the vomer does 

 not project to the alveolar surface, the lateral edge of the dentary is 

 weakly serrated. Alveolar width on the dentary surface is 17% of the 

 condylobasal length, and the maxillary width is 20%. Both NCSM 

 29278 and 14783 are thus morphological intermediates (presumed 

 hybrids). The former more closely resembles P. rubriventris, whereas 

 the latter is more similar to P. floridana. 



Ward (1984) indicated that markings and coloration are too variable 

 to be reliable for diagnosing cooter species. If, as Ward suggests, only 

 osteological characters reliably separate P. concinna from P. floridana, 

 those species should be considered cryptic (sibling) based on their 

 external morphology. That would also imply that there are two clearly 

 recognizable osteomorphs, with little intergradation or polymorphism. 

 Because large series of skeletal material taken throughout the range of 

 Pseudemys have not been examined, there is no basis for that conclusion. 

 Hedges (1990) appropriately stated that "speciation is a dynamic process 

 and we should expect borderline cases." Results from the present study 

 suggest that the relationship between P. concinna and P. floridana in 

 the Atlantic drainages of North Carolina is more characteristic of 

 subspecies than species. Nearly all of the typical examples of P. concinna 

 occur in the piedmont, whereas individuals easily identified as P. 

 floridana are in the coastal plain (Fig. 1). That is similar to Carr's (1952) 

 observations that led him to consider the two forms subspecies of P. 



