Giraffa camelopardalis ( Linnaeus, 1758 )

Rios, M, Danowitz, M & Solounias, N, 2016, First comprehensive morphological analysis on the metapodials of Giraffidae, Palaeontologia Electronica 410 (10453), pp. 1-39 : 19-21

Giraffa camelopardalis ( Linnaeus, 1758)

Specimens. AMNH 53543, AMNH 82001, AMNH 53550, AMNH 14135

Description. The proximal articular surface exhibits three distinct facets. The lateral facet for the os naviculocuboideum is kidney-shaped. The medial facet for the os cuneiforme intermediolaterale is more oval and can be contacting or slightly separated from the os cuneiforme mediale facet, which is oval. On the lateral facet, there is a slight constriction where the lateral ridge meets the lateral epicondyle. Medial to this constriction, there is a pointed bony protrusion on the articular surface. The medial and lateral epicondyles are symmetrical in size and morphology ( Figure 15). There is a shallow, obliquely oriented groove on the medial edge of the medial epicondyle, separating it into a plantar and a dorsal head. Both heads slightly flare outward ( Figure 14.3 ). There is a deep, oblique groove on the lateral epicondyle, separating the lateral epicondyle into a plantar and a dorsal head. Both heads flare outward, and the flaring is more pronounced on the dorsal head. The pygmaios is absent, there is a dish-shaped depression on the plantar surface between the medial and lateral epicondyles with lipped, distinct edges in its place ( Figure 16 ). There is a thin, elongated, oval bony protrusion on the medial surface of the medial epicondyle ( Figure 17). The central trough is shallow in depth, and flattens distally. The medial and lateral ridges are sharp and thin. On the lateral and medial surfaces, the lateral and medial ridges appear more textured than the main shaft. There is a faint pyramidal rise distally. The medial edge of the shaft flares towards the distal condyle. The keels of the distal condyle are confined and do not extend onto the distal shaft.

Comparisons between the metacarpals

To analyze the proportions of the metacarpals we have used the robustness index (RI) ( Fragomeni and Prothero, 2011; Woodman and Gaffney, 2014).

We have applied this formula to a sample of a total 115 giraffid metacarpals and established the following robustness categories ( Figure 19 ; Tables 1-2):

1. Very slender: RI under 9. Includes Bohlinia attica , Giraffa camelopardalis , Canthumeryx sirtensis , and Palaeotragus rouenii .

2. Slender:

3. RI between 9 and 10. Includes Okapia johnstoni and Decennatherium pachecoi .

4. Medium: RI between 10 and 17. Includes Bramatherium megacephalum , Samotherium major , Birgerbohlinia schaubi , and Helladotherium duvernoyi.

5. Robust: RI over 17. Includes Sivatherium giganteum .

We have also analyzed the variation in length of a sample of 142 giraffid metacarpals and established the following categories ( Figure 20 ; Tables 1, 3):

1. Long:> 500 mm, includes Bohlinia attica and Giraffa camelopardalis .

2. Medium: between 500 and 350 mm, most species fall into this category. Birgerbohlinia schaubi , Sivatherium giganteum , Decennatherium pachecoi , and Palaeotragus rouenii fall into the medium-short range, with most specimens between 350 and 450 mm, while Bramatherium megacephalum, Helladotherium duvernoyi, and Samotherium major fall into the medium-long category, with most specimens over 450 mm.

3. Short: <350 mm Canthumeryx sirtensis and

Okapia johnstoni fall in this category.

Using these descriptive parameters, we also plot the total length versus the midshaft minimum transverse diameter, to demonstrate the relative slenderness of the limbs ( Figure 21 ) ( Bover et al., 2010; Fragomeni and Prothero, 2011; Woodman and Gaffney, 2014).

Comparisons between the metatarsals

We have established the robustness categories using the same formula as above for the giraffid metatarsals (N=92) ( Figure 22 ; Tables 4-5):

1. Very slender: RI under 8. Includes Bohlinia attica , Giraffa camelopardalis , Canthumeryx sirtensis , and Palaeotragus rouenii .

2. Slender: RI between 8 and 10. Includes Okapia johnstoni and Decennatherium pachecoi .

3. Medium: RI between 10 and 12. Includes Bramatherium megacephalum , Samotherium major , Birgerbohlinia schaubi , and Helladotherium duvernoyi.

4. Robust: RI over 12. Includes the robust Sivatherium giganteum .

We have also analyzed the variation in length of a sample of 110 giraffid metatarsals and estab-

Total Species Specimen nº Diaph. TD RI Reference Length Canthumeryx sirtensis UCB V. 4899/42058 290 17,5 6,03 Hamilton, 1978

Canthumeryx sirtensis BU 20128

Figures

FIGURE 14. Palmar views of the right metacarpals (left) and plantar views of the metatarsals (right) of certain Giraffidae. 1, Canthumeryx sirtensis, early-middle Miocene, Moruorot Hill, NMK Mo 41 (metatarsal); 2, Bohlinia attica, late Miocene, Pikermi, MNHNP 27561 (metacarpal), MNHNP 2357 (metatarsal) (reversed); 3, Giraffa camelopardalis, Zaire, AMNH 53550 (metacarpal), AMNH 53550 (metatarsal) (both reversed). Scale bar equals 200 mm.

FIGURE 16. Three selected metatarsal characteristics. This simplified table can be used to facilitate specimen identifications and differentiate between different giraffid taxa.

FIGURE 19. Box-and-whiskers plot with the metacarpal RI of the Giraffidae analyzed.

FIGURE 20. Dispersion plot with the absolute metacarpal length of the Giraffidae analyzed. TABLE 3. Descriptive parameters of the metacarpal length of the Giraffidae (Max., maximum; Min., minimum; SD, standard deviation; Ntotal, total sample size).

FIGURE 21. Dispersion plot showing the total length of the metacarpals versus the midshaft minimum transverse diameter of the Giraffidae analyzed.

FIGURE 22. Box-and-whiskers plot with the metatarsal RI of the Giraffidae analyzed.