Editing Pygmy hippopotamus (section)

=== Nigerian subspecies ===
A distinct subspecies of pygmy hippopotamus existed in Nigeria until at least the 20th century, though the validity of this has been questioned.<ref name="Redlist"/> The existence of the subspecies, makes ''Choeropsis liberiensis liberiensis'' (or ''Hexaprotodon liberiensis liberiensis'' under the old classification) the full [[trinomen|trinomial nomenclature]] for the Liberian pygmy hippopotamus. The Nigerian pygmy hippopotamus was never studied in the wild and never captured. All research and all zoo specimens are the Liberian subspecies. The Nigerian subspecies is classified as ''C.&nbsp;liberiensis heslopi''.<ref name="The Hippos"/>

The Nigerian pygmy hippopotamus ranged in the [[Niger River|Niger River Delta]], especially near [[Port Harcourt]], but no reliable reports exist after the collection of the museum specimens secured by [[Ian Heslop]], a British colonial officer, in the early 1940s. It is probably extinct.<ref name="Redlist"/> The subspecies is separated by over {{convert|1800|km|mi|abbr=on}} and the [[Dahomey Gap]], a region of savanna that divides the forest regions of West Africa. The subspecies is named after Heslop, who shot three members of it in 1935 and 1943.<ref name=Enigma>{{cite book|author-last1=Robinson| author-first1=Phillip T.|author-last2=Flacke| author-first2=Gabriella L.| author-last3=Hentschel| author-first3= Knut M.| year=2017| title=The Pygmy Hippo Story: West Africa's Enigma of the Rainforest| publisher=Oxford University Press| place=Oxford| isbn=978-0-19-061185-9|pages=61, 65}}</ref> He estimated that perhaps no more than 30 pygmy hippos remained in the region.<ref name=Action>{{Cite web | url = http://www.iucn.org/themes/ssc/sgs/pphsg/APchap3-3.htm | archive-url = https://archive.today/20080105044155/http://www.iucn.org/themes/ssc/sgs/pphsg/APchap3-3.htm | url-status = dead | archive-date = 2008-01-05 | title = Pigs, Peccaries and Hippos Status Survey and Action Plan | year = 1993 | access-date = 2008-08-23 | work = [[World Conservation Union]] status survey | author = Eltringham, S. Keith}}</ref>

Heslop sent four pygmy hippopotamus skulls he collected to the [[British Museum of Natural History]] in London. These specimens were not subjected to taxonomic evaluation, however, until 1969 when {{Ill|Gordon Barclay Corbet|de}} classified the skulls as belonging to a separate subspecies based on consistent variations in the proportions of the skulls.<ref name=Corbet>{{Cite journal| title = The taxonomic status of the pygmy hippopotamus, Choeropsis liberiensis, from the Niger Delta | author = Corbet, G. B. | journal = [[Journal of Zoology]] | year = 1969 | volume = 158 | issue = 3 | pages = 387–394| doi = 10.1111/j.1469-7998.1969.tb02156.x}}</ref> The Nigerian pygmy hippos were seen or shot in [[Rivers State]], [[Imo State]] and [[Bayelsa State]], [[Nigeria]]. While some local humans are aware that the species once existed, its history in the region is poorly documented.<ref name="The Hippos"/>