MORFOMETRIA CAUDA-CLOACAL PARA SEXAGEM DE Phrynops geoffroanus (SCHWEIGGER, 1812)

In order to study the presence of sexual dimorphism in Phrynops geoffroanus , collections were carried out in the Leite stream in the municipality of Floriano-Piaui. The 22 specimens captured (13 males e 9 female) were measured and sexed, considering quantitative data (pre-cloacal and post-cloacal distances, length and width of the anal plate) and qualitative data (narrow or wide head and length of the humeral plates). Data were analyzed using the Wilcoxon-Mann-Whitney test (U), Dummy variable (D) and linear regression. The U Test demonstrated that the variables anal plate length (α = 0.177), pre-cloacal distance (α = 0.0004) and post-cloacal distance (α = 0.038) showed significant differences between genders. Through linear regression it was possible to observe that the pre-cloacal and post-cloacal length measurements in males have values twice as high as in females. The Dummy variable resulted in a value of D = 7.14, demonstrating that there is reason to believe in the existence of dimorphic morphological patterns in P . geoffroanus . From the results found, it is possible to conclude that the measurements of anal plate, pre-cloacal and post-cloacal distances are different between males and females in the studied population of P . geoffroanus , confirming sexual dimorphism, however, further studies of different populations are required in order to establish a morphological pattern for the species. Keywords: Morphology; Sexual dimorphism; Turtles.