Primate penile bone symplesiomorphy disclosed: why a critical literature review is crucial?

PRIMATE PENILE BONE SYMPLESIOMORPHY DISCLOSED: WHY A CRITICAL LITERATURE REVIEW IS CRUCIAL? Federica Spani1, Gabriele Gentile2, Massimiliano Scalici1, Monica Carosi1 1 Department of Sciences, Roma Tre University, 2 Department of Biology, University of Rome Tor Vergata In order to reconstruct the evolutionary history of primate penile bone (baculum) we accomplished a thorough primary literature search and critical revision, collecting data about the occurrence of baculum in 306 primate species. Although our resulting presence/absence binary matrix was mapped onto the most complete primate phylogeny (N=367; Springer et al., 2012) the analysis was performed on 255 species since we had to exclude taxa either provided with occurrence data however missing in the phylogeny or viceversa. Based on data analysed it appears that the primate ancestor had a baculum which therefore is a symplesiomorphic trait for the entire order. Main results show 8 independent losses of baculum. Two cases in particular need to be deepened: the phylogenetic parallelism of loss in Lagothrix and Ateles and the exceptional presence of baculum in only one Tarsius species (T. syrichta) despite the absence in the whole genus. Our evolutionary scenario clarifies uncertainties recently reported by Schultz et al. (2016) who couldn’t set the ancestral state of baculum for the primate order. In that study, likely flaws were the literature source used (only reviews) which resulted in a low number of primate species included into the analysis (N=102), and the arbitrary choice of transferring occurrence data between congeneric species to maximize the covering of the phylogeny used. Our study confirms that a higher number of species can substantially modify results about the ancestral characterstate reconstruction of baculum. Future multidisciplinary investigations including potential correlates might contribute to disentangle both evolution and function of this neglected bone.