[[File:Okapi Giraffe Neck.png|thumb|Despiteஒட்டகச்சிவிங்கியின் greatlyகழுத்து differingமுள்ளந்தண்டெலும்புகளின் neck lengths, [[okapi]] (left) and giraffe (right) both have seven cervical vertebrae. The giraffe's neck is elongated by [[heterochrony]], extension of the time for the [[embryonic development]] of these bones.நீளம்<ref>{{cite book |last=Hillis |first=David M. |title=Principles of Life |url=https://books.google.com/books?id=-WQdBQAAQBAJ&pg=PA280 |date=May 2011 |publisher=Palgrave Macmillan |isbn=978-1-4641-6298-5 |pages=280– |deadurl=no |archiveurl=https://web.archive.org/web/20180506014656/https://books.google.com/books?id=-WQdBQAAQBAJ&pg=PA280 |archivedate=2018-05-06 |df= }}</ref>]]