皮骨角

皮骨角^[1]（英語：Ossicones）是指長頸鹿、雄性㺢㹢狓等動物頭上的犄角。此外，現已滅絕的西瓦鹿和梯角鹿科動物（如Climacoceras）頭部也生有這種結構。^[2]部分學者曾認為這些滅絕種頭部的皮骨角並非真正意義上的皮骨角；不過後續的研究表明，這些動物的皮骨角和長頸鹿科的動物很接近。皮骨角位於背骨、額骨上，隨着年齡的增加會逐漸長到頭骨上。^[3]

皮骨角和洞角類似，區別在於皮骨角由軟骨組織骨化而成，而非由活骨直接形成，^[4]而且皮骨角上由皮毛覆蓋，而非角蛋白。

皮骨角一出生起就存在，但剛生下來時皮骨角貼着頭部而不是長在頭骨上，以防降生時受傷。^[5]雄性動物和雌性動物的皮骨角結構、用途都有不同。雄性的皮骨角更厚，因雄性長頸鹿喜歡脖擊而導致皮骨角頂部的骨骼裸露出來。這些皮骨角還會增加長頸鹿頭部的重量，使得其脖擊時的攻擊威力更大，有時甚至能致命。皮骨角的出現也導致了一些其他的進化特徵，如動物的外皮更重，真皮層也出現了特化的防禦。^[6]

參考資料

[1]
邱占祥; 閻德發; 賈航. 山东山旺Palaeomer yx化石的初步研究 (PDF). 古脊椎動物學報. 1985-07, 23 (3): 173–195 [2019-12-22]. （原始內容存檔 (PDF)於2020-05-17）.
[2]
Hadar Picture Gallery. An ossicone of the extinct, giant, short-necked giraffe （頁面存檔備份，存於互聯網檔案館）. University of Washington.
[3]
Solounias, N. Prevalence of Ossicones in Giraffidae (Artiodactyla, Mammalia). Journal of Mammalogy. 1988, 69 (4): 845–8. JSTOR 1381645. doi:10.2307/1381645.
[4]
The Nashville Zoo at Grassmere – Animals :: Masai Giraffe. Nashville Zoo at Grassmere. 2008-06-30. （原始內容存檔於2008-06-30）.
[5]
FAQs - GiraffeConservation.org. GiraffeConservation.org. [2018-04-26]. （原始內容存檔於2019-01-12）（美國英語）.
[6]
Geist, Valerius. The Evolution of Horn-Like Organs. Behaviour. 1966, 27 (1): 175–214. doi:10.1163/156853966x00155.

拓展閱讀

Hou, Sukuan; Danowitz, Melinda; Sammis, John; Solounias, Nikos. Dead ossicones, and other characters describing Palaeotraginae (Giraffidae; Mammalia) based on new material from Gansu, Central China. Zitteliana. 2014, 32: 91–8 [2019-12-22]. （原始內容存檔於2020-02-13）.
Solounias, N; Moelleken, S. M. C. Evidence for the Presence of Ossicones in Giraffokeryx punjabiensis (Giraffidae, Mammalia). Journal of Mammalogy. 1991, 72 (1): 215–7. JSTOR 1382004. doi:10.2307/1382004.
Churcher, Charles S. Cranial Appendages of Giraffoidea. Horns, Pronghorns, and Antlers. 1990: 180–94. ISBN 978-1-4613-8968-2. doi:10.1007/978-1-4613-8966-8_5.
Davis, E. B; Brakora, K. A; Lee, A. H. Evolution of ruminant headgear: A review. Proceedings of the Royal Society B: Biological Sciences. 2011, 278 (1720): 2857–65. JSTOR 41315010. PMC 3151718 . PMID 21733893. doi:10.1098/rspb.2011.0938. 簡明摘要 – ScienceDaily (July 10, 2010).
Danowitz, Melinda; Barry, John C; Solounias, Nikos. The earliest ossicone and post-cranial record of Giraffa. PLOS ONE. 2017, 12 (9): e0185139. PMC 5605118 . PMID 28926638. doi:10.1371/journal.pone.0185139.
Ríos, María; Sánchez, Israel M; Morales, Jorge. A new giraffid (Mammalia, Ruminantia, Pecora) from the late Miocene of Spain, and the evolution of the sivathere-samothere lineage. PLOS ONE. 2017, 12 (11): e0185378. PMC 5665556 . PMID 29091914. doi:10.1371/journal.pone.0185378. 簡明摘要 – Science (November 2, 2017).

[1] [1]
邱占祥; 閻德發; 賈航. 山东山旺Palaeomer yx化石的初步研究 (PDF). 古脊椎動物學報. 1985-07, 23 (3): 173–195 [2019-12-22]. （原始內容存檔 (PDF)於2020-05-17）.

[2] [2]
Hadar Picture Gallery. An ossicone of the extinct, giant, short-necked giraffe （頁面存檔備份，存於互聯網檔案館）. University of Washington.

[3] [3]
Solounias, N. Prevalence of Ossicones in Giraffidae (Artiodactyla, Mammalia). Journal of Mammalogy. 1988, 69 (4): 845–8. JSTOR 1381645. doi:10.2307/1381645.

[4] [4]
The Nashville Zoo at Grassmere – Animals :: Masai Giraffe. Nashville Zoo at Grassmere. 2008-06-30. （原始內容存檔於2008-06-30）.

[5] [5]
FAQs - GiraffeConservation.org. GiraffeConservation.org. [2018-04-26]. （原始內容存檔於2019-01-12）（美國英語）.

[6] [6]
Geist, Valerius. The Evolution of Horn-Like Organs. Behaviour. 1966, 27 (1): 175–214. doi:10.1163/156853966x00155.

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