Friday, 27 November 2015

Yet another transitional fossil: a giraffe-like animal with an intermediate-length neck

We don't need any more evidence for evolution as the evidence for the reality of common descent and large-scale evolutionary change was already compelling a over a century ago. However, new evidence is always welcome, particularly if it casts light on iconic animals. In this case, it is the giraffe and its long neck. We already know how the path of the recurrent laryngeal nerve in giraffes, which makes a pointless detour down its neck, under the aorta, before returning to innervate the larynx - a wasteful detour of several metres - provides evidence for common descent as this same pointless detour is shared by other creatures with which it shares a common ancestor. Now, as , ,

The authors neatly summarise the significance of Samotherium major for our understanding of the evolution of the giraffe neck:
Giraffidae are represented by many extinct species. The only two extant taxa possess diametrically contrasting cervical morphology, as the okapi is short-necked and the giraffe is exceptionally long-necked. Samotherium major, known from the Late Miocene of Samos in Greece and other Eurasian localities, is a key extinct giraffid; it possesses cervical vertebrae that are intermediate in the evolutionary elongation of the neck. We describe detailed anatomical features of the cervicals of S. major, and compare these characteristics with the vertebrae of the two extant giraffid taxa. Based on qualitative morphological characters and a quantitative analysis of cervical dimensions, we find that the S. major neck is intermediate between that of the okapi and the giraffe. Specifically, the more cranial (C2–C3) vertebrae of S. major represent a mosaic of features shared either with the giraffe or with the okapi. The more caudal (C5–C7) S. major vertebrae, however, appear transitional between the two extant taxa, and hence are more unique. Notably, the C6 of S. major exhibits a partially excavated ventral lamina that is strong cranially but completely absent on the caudal half of the ventral vertebral body, features between those seen in the giraffe and the okapi. Comprehensive anatomical descriptions and measurements of the almost-complete cervical column reveal that S. major is a truly intermediate-necked giraffid. Reconstructions of the neck display our findings. [Emphasis mine]
There is little more that needs to be said here other than that once again, YEC claims that there are no transitional fossils have been shown to be nonsense.

Ventral view of the C1–C7 vertebrae of (a) Okapia johnstoni (AMNH 51197), (b) Samotherium major and (c) Giraffa camelopardalis (AMNH 82001). The S. major vertebrae depicted are the most complete and undistorted specimens and are represented in figures 14. (Source)

Lateral view of articulated C1–C7 vertebrae of (a) Giraffa camelopardalis (AMNH 82001), (b) Samotherium major and (c) Okapia johnstoni (AMNH 51197). A representative skull of Samotherium major using undistorted surfaces of several specimens (NHMBa29, NHMBa30, AMNH22808A, MGL11, SMNS 13285) is included to demonstrate verticality and a more complete illustration of this key extinct giraffid. The S. major vertebrae depicted are the most complete and undistorted specimens and are represented in figures 14.