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closeOssicones and musculature support necks-for-sex origin
Posted by RESimmons on 05 Dec 2015 at 13:27 GMT
Congratulations to the authors for their thorough re-interpretation of this possible giraffid. A caught my eye ....
Also, as noted by Astibia et al. [24] the neck musculature probably climbed the most basal part of the occipital appendage acquiring a relatively pronounced angle in its occipital insertion, thus helping in the enhanced head extension of palaeomerycids. These neck-head modifications resulted in powerful lateral and dorsal movements of the head although their exact purpose is not known, and both ecological and behavioral morpho-functional hypotheses could be suggested (e.g. male intraspecific fighting is an obvious one) but we have no data to back up any of them.
YES!... and they have been suggested! I think you are being too modest. With short ossicones and strong musculature indicating powerful lateral and dorsal movements of the head you may have uncovered the key to the use of the extant giraffe's necking mode of fighting (a unique fighting style in ruminants). We (Simmons and Altweg 2010 (J Zool Lond 282: 6-12.) predicted that the shape of the ossicones and the fighting style may be key to differentiating the necks for sex and competing browsers hypotheses. If this animal lies at the base of the giraffoid lineage as you suggest then you may have uncovered a critical link that we were looking for....
The other obvious mode of male-male fighting is head-butting and head wrestling. The strong lateral muscles are not needed for either, but a side to side and backward motion of the head and neck is consistent with what we see in the modern giraffe. Your fossil evidence doesn't give any clues to neck length (unless I missed something) so that would be useful to explore. The protruding teeth are intriguing, and may also give a clue to fighting style.
RE: Ossicones and musculature support necks-for-sex origin
Micromeryx replied to RESimmons on 13 Dec 2015 at 11:44 GMT
Thanks for your compliments. I find your comments very interesting, and, of course, the first thing that crossed my mind when describing the modified neck musculature of palaeomerycids is the giraffe-like male-to-male combat. But I think it is not so easy to say we have unlocked the origin of the necking fighting method. First, the anatomical modifications in the nuchal area of palaeomerycids are not present in the Giraffidae; in fact they are not present in any other known member of the Giraffomorpha (or the Pecora, by the way). And second, between palaeomerycids and giraffids there are several giraffomorph groups (e.g. Prolibytherium and climacoceratids) that do not present the short supra-orbital ossicones of palaeomerycids and (some) giraffids, but instead have complicated and strange appendages, so it is difficult to claim for a unique basal development of the giraffe fighting method. Maybe the necking mode of fighting was developed more than once within the Giraffomorpha. However it is a very interesting line of research.