First comprehensive morphological analysis on the metapodials of Giraffidae

Abstract

Giraffids are a group of relict pecoran ruminants with only two living taxa. During the Miocene, however, this group was much more diverse, with more than 20 different species showing a wide range of variability. In addition to many other parts of the skeleton this variability is also represented in their metapodials. We find inter-specific anatomical differences in the giraffid metapodials; each taxon evaluated possesses a unique combination of limb morphologies. The proximo-palmar/plantar metapodial surface provides useful characteristics and allows for genus identifications and comparisons. We describe the central trough of the metapodial shaft; when combined with the absolute length of the limb, the depth of this trough allows for better separation between taxa. We find that the metacarpal robustness index exceeds that of the metatarsals in all except one giraffid evaluated, supporting a front-loaded body weight distribution, consistent with the elongated cervicals or large ossicones seen in many taxa. The morphological features of the giraffid metapodials, as well as the limb lengths and proportions can be a useful tool for phylogenetic analysis.

Comparisons of Schansitherium tafeli with Samotherium boissieri (Giraffidae, Mammalia) from the Late Miocene of Gansu Province, China

“…We use cervical vertebral terminology and characteristics established by Danowitz and Solounias [24] and Danowitz et al [25]. We use metapodial terminology established by Rios et al [6]. …”

“…The metacarpals were evaluated after Rios et al [6]. The epicondyles are similar in size and morphology.…”

“…The medial and lateral epicondyles are continuous distally with the medial and lateral ridges, respectively. The pygmaios [6] is oriented closer to the medial epicondyle. There is an elongated, oval bony protrusion at the proximal medial shaft, which originates at the level of the proximal articular surface.…”

“…There are approximately twenty-five species of Giraffidae, two extant and the rest are extinct [2–3]. The modern giraffe possesses exceptionally elongated cervical vertebrae and metapodials; the extinct taxa exhibit varying degrees of neck and limb elongation [4–6]. Giraffidae possess specialized cranial appendages termed ossicones, which start as separate ossifications that subsequently fuse to the skull [2, 7–9].…”

Fossil Giraffidae (Mammalia, Artiodactyla) from the late Miocene of Thermopigi (Macedonia, Greece)

“…Nevertheless, there are distinct morphological differences on the limb bones of both taxa. Detailed descriptions of characters of post-cranial elements of both H. duvernoyi and S. major, were given by Kostopoulos (2009), Ríos et al (2016), and Solounias and Danowitz (2016b).…”