Morphometric differentiation between two murid rodents, Praomys tullbergi (Thomas, 1894) and Praomys rostratus (Miller, 1900), in West Africa

Morphometric differentiation between the two species of the genus Praomys Thomas (1915) inhabiting West Africa was investigated using univariate and multivariate statistics on external, cranial and dental measurements. One hundred and seventy six adult specimens (78 P. tullbergi and 98 P. rostratus) from fifteen localities throughout the Upper Guinean rainforest were analyzed. All specimens had been previously identified to species level by molecular analyses (16S rRNA and/or cytochrome b gene sequencing). Sexual dimorphism was observed in both species, but was more significant in P. rostratus than in P. tullbergi. Body weight was significantly lower in P. tullbergi than in P. rostratus. Moreover, males of P. tullbergi had a significantly smaller head and body length than males of P. rostratus. Specimens of P. tullbergi of both sexes were on average smaller than males of P. rostratus regarding all cranial and dental measurements, and smaller than females of P. rostratus with regard to most measurements. However, none of the cranial or dental measurements treated in our study could be used alone to separate P. rostratus and P. tullbergi, because of considerable overlap in the ranges of each variable. A good discrimination between the two species was obtained by means of craniometrical multivariate statistics, several rostrum measurements being significantly lower in P. tullbergi than in P. rostratus. Discrepancies between our results and former published studies are hypothesized to be due to differences between the variables used and/or the geographical areas covered.