Disentangling morphological variation in metapodials of giraffids: Modern and traditional approaches

Abstract

Modern giraffids are nowadays represented by few species; however, this family was quite diverse during the Neogene. Several lineages radiated, showing high morphological disparity in metapodial shapes. During the last few years, not many scholars have focused on this subject. Furthermore, modern statistical approaches have been totally neglected. Herein, we present the first attempt to fill this gap of knowledge adopting a plethora of phylogenetic comparative approaches alongside multivariate statistics. Namely, we performed a series of traditional and geometric morphometric analyses for a total of 207 metapodial specimens of extant and fossil giraffid species. Our results recognized four different clusters, grouped in different morphospaces. Moreover, two of these clusters are clearly outliers in respect to an overall homogeneous distribution. The two outlying clusters include short and robust metapodials observed in Sivatherium, and long and slender metapodials observed in Giraffa and Bohlinia, respectively. Similarities between the modern Okapia and the extinct genus Decennatherium were also detected. This study explores the relations between the morphological adaptations and the ecological roles of different members of the Giraffidae. It also provides insights into how different environmental factors might have influenced the evolution of this group and the adaptation of their members to diverse environments. Furthermore, locomotory adaptations of the most hyper-specialized Giraffidae groups are briefly discussed and investigated.