Ossicone

Ossicones of a reticulated giraffe
Fossilised antler-like ossicone of Sivatherium maurusium

Ossicones are horn or antler-like, protuberances on the heads of giraffes, male okapis, and their extinct relatives, such as Sivatherium, and the climacoceratids, such as Climacoceras.[1] It has been argued that these extinct species did not have true ossicones; however, later research has revealed their ossicones to be in line with those of giraffids. Ossicones are located dorsal to the frontal bone and fuse to the skull later in life.[2]

Ossicones are similar to the horns of antelopes and cattle, except that they are derived from ossified cartilage rather than living bone,[3] and that the ossicones remain covered in skin and fur, rather than horny keratin. Antlers (such as on deer) are derived from bone tissue: when mature, the skin and fur covering of the antlers, termed "velvet", is sloughed and scraped off to expose the bone of the antlers.

Ossicones are present at birth; however, they lie flat and are not attached to the skull as to avoid injury at birth.[4] Male and female ossicones vary in structure and purpose. Males typically have thicker ossicones that become bald on top due to frequent necking. These ossicones also add weight to the giraffe's head allowing them to deliver heavier, sometimes fatal, blows. The added weight is an evolutionary trait bred from necessity. The addition of ossicones also leads to other evolutionary adaptations like heavy hides and specialized dermal shields.[5]

References

  1. ↑ Hadar Picture Gallery. An ossicone of the extinct, giant, short-necked giraffe. University of Washington.
  2. ↑ Solounias, N (1988). "Prevalence of Ossicones in Giraffidae (Artiodactyla, Mammalia)". Journal of Mammalogy. 69 (4): 845–8. doi:10.2307/1381645. JSTOR 1381645.
  3. ↑ "The Nashville Zoo at Grassmere – Animals :: Masai Giraffe". Nashville Zoo at Grassmere. 30 Jun 2008. Archived from the original on 2008-06-30.
  4. ↑ "FAQs - GiraffeConservation.org". GiraffeConservation.org. Retrieved 2018-04-26.
  5. ↑ Geist, Valerius (1966). "The Evolution of Horn-Like Organs". Behaviour. 27 (1): 175–214. doi:10.1163/156853966x00155.

Further reading

  • Hou, Sukuan; Danowitz, Melinda; Sammis, John; Solounias, Nikos (2014). "Dead ossicones, and other characters describing Palaeotraginae (Giraffidae; Mammalia) based on new material from Gansu, Central China". Zitteliana. 32: 91–8.
  • Solounias, N; Moelleken, S. M. C (1991). "Evidence for the Presence of Ossicones in Giraffokeryx punjabiensis (Giraffidae, Mammalia)". Journal of Mammalogy. 72 (1): 215–7. doi:10.2307/1382004. JSTOR 1382004.
  • Churcher, Charles S (1990). "Cranial Appendages of Giraffoidea". Horns, Pronghorns, and Antlers. pp. 180–94. doi:10.1007/978-1-4613-8966-8_5. ISBN 978-1-4613-8968-2.
  • Davis, E. B; Brakora, K. A; Lee, A. H (2011). "Evolution of ruminant headgear: A review". Proceedings of the Royal Society B: Biological Sciences. 278 (1720): 2857–65. doi:10.1098/rspb.2011.0938. JSTOR 41315010. PMC 3151718. PMID 21733893. Lay summary – ScienceDaily (July 10, 2010).
  • Danowitz, Melinda; Barry, John C; Solounias, Nikos (2017). "The earliest ossicone and post-cranial record of Giraffa". PLOS One. 12 (9): e0185139. doi:10.1371/journal.pone.0185139. PMC 5605118. PMID 28926638.
  • Ríos, María; Sánchez, Israel M; Morales, Jorge (2017). "A new giraffid (Mammalia, Ruminantia, Pecora) from the late Miocene of Spain, and the evolution of the sivathere-samothere lineage". PLOS One. 12 (11): e0185378. doi:10.1371/journal.pone.0185378. PMC 5665556. PMID 29091914. Lay summary – Science (November 2, 2017).


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