<i>Morotochoerus</i> de Uganda (17.5 Ma) y <i>Kenyapotamus</i> de Kenia (13-11 Ma): implicaciones sobre el origen de los hipopotámidos

Abstract

The aim of this paper is to describe and interpret suiform teeth from Moroto, Uganda, and Ngorora, Kenya, which contribute to the debate about hippo-anthracothere-whale relationships. The early stages of hippopotamid evolution are relatively poorly known on account of the paucity of their fossil record older than 7 Ma. New specimens of Morotochoerus from Uganda reveal that it is not closely related to Hippopotamidae; the superficial resemblances of the cheek teeth to those of hippos represent convergences and not homologies. Restricted samples of Palaeopotamus ternani are available from the Middle Miocene of Kenya {Maboko, ca 16 Ma; Muruyur, ca 14.5 Ma; Fort Ternan, ca 13.7 Ma} while from the base of the late Miocene, Kenyapotamus coryndonae is known from Kenya {Ngerngerwa, ca 10.5-10 Ma; Nakali, ca 10.5 Ma; Samburu Hills, ca 9.5 Ma}, Ethiopia {Ch'orora, ca 10.5 Ma} and Tunisia {Beglia Formation ca 11-10 Ma}. The recovery of specimens of Kenyapotamus from the Ngorora Formation, Kenya, aged ca 11 Ma, is of interest because it includes well preserved teeth, including an m/3 in good condition. These specimens support the hypothesis that hippopotamids descended from palaeochoerids and not from anthracotheres.Keywords: Morotochoerinae, Morotochoerus, Kenyapotamus, Hippopotamidae, Palaeochoeridae, Cetartiodactyla, Africa, Miocene, Evolution RESUMEN El objetivo de este trabajo es describir e interpretar los dientes suiformes de Moroto, Uganda, y Ngorora, Kenia, que contribuyen al debate sobre las relaciones hipo-anthracothere-whale. Las primeras etapas de la evolución de los hipopotámidos son relativamente poco conocidas a causa de la escasez de su registro fósil en edades superiors a los 7 Ma. Nuevos ejemplares de Morotochoerus en Uganda revelan que no están estrechamente relacionados con Hippopotamidae, las semejanzas superficiales de los dientes de la mandíbula con los de los hipopótamos representan convergencias y no homologías. Algunas muestras de Palaeopotamus ternani aparecen en el Medio Mioceno de Kenia {Maboko, ca 16 Ma; Muruyur, ca 14.5 Ma; Fort Ternan, ca 13.7 Ma}, mientras que desde la base del Mioceno tardío, Kenyapotamus coryndonae aparece en Kenia {Ngerngerwa, ca 10.5-10 Ma; Nakali, ca 10.5 Ma; Samburu Hills, ca 9,5 Ma}, {Ch'orora Etiopía, ca 10.5 Ma} {y Túnez Beglia Formación ca 11-10 Ma}. La obtención de especímenes de Kenyapotamus de la Formación Ngorora, Kenya, con edad ca 11 Ma, es de interés porque incluye dientes bien conservados, incluyendo un m/3 en buenas condiciones. Estos ejemplares apoyan la hipótesis de que los hipotámidos descienden de paleoquéridos y no de antracotéridos.

Evolutionary processes involved in the diversification of chelonian and mammal polystomatid parasites (Platyhelminthes, Monogenea, Polystomatidae) revealed by palaeoecology of their hosts

“…The common hippo, Hippopotamus amphibious Linnaeus, 1758, and the pygmy hippo, Choeropsis liberiensis Leidy, 1852, are the only two representatives of extant hippopotamids that would have diverged from each other at about 5.7 Mya (Montgelard et al, 1997). Whereas hippopotamids may have originated in the Early Miocene, Orliac et al (2010) considered an origin at about 21 Mya, while Pickford (2011) argued for their first appearance at about 16.5 Mya. Regardless of the exact timing of their origin, hippopotamids may have adopted semi-aquatic habits at least as early as the latest Miocene (Boisserie et al, 2011).…”

Hippos stem from the longest sequence of terrestrial cetartiodactyl evolution in Africa

“…Apparently, these uncertainties sustained a diversity of opinions on the affinities of Hippopotamidae within fossil cetartiodactyls (for example, refs [2][3][4][5][6][7][8]. Among these, some noncladistic approaches are still radically in disagreement with molecular data 7,8 , whereas combined data set analyses have essentially maintained an unclear emergence of Hippopotamidae from an Oligocene ghost lineage, for example refs 3,4,9. In fact, the integration of Miocene hippopotamid data into morphology-based cladistic analyses brought substantial support to a hippopotamid emergence among anthracotheres 10,11 .…”

“…Among these, some noncladistic approaches are still radically in disagreement with molecular data 7,8 , whereas combined data set analyses have essentially maintained an unclear emergence of Hippopotamidae from an Oligocene ghost lineage, for example refs 3,4,9. In fact, the integration of Miocene hippopotamid data into morphology-based cladistic analyses brought substantial support to a hippopotamid emergence among anthracotheres 10,11 . However, this approach did not succeed in precisely identifying the stem group of Hippopotamidae among anthracotheres.…”

A Lower Molar of a Primitive, Large Hippopotamus from the Lower Miocene of Kenya

“…Tsubamoto et al (2011) also suggested a possible hippopotamid affinity of Kulutherium. In contrast, Pickford (2011) suggested an anthracotheriid affinity of Morotochoerus and Kulutherium. However, the fossil material of these two early Miocene genera is very limited (Pickford, 1998(Pickford, , 2007a.…”

“…Pickford, 2007bPickford, , 2008Pickford, , 2011Boisserie and Lihoreau, 2006;Boisserie et al, 2010Boisserie et al, , 2011Tsubamoto et al, 2011;Alloing-Séguier et al, 2014;Lihoreau et al, 2015; and references cited therein). The undoubtedly oldest record of the family is from the middle Miocene of Kenya, which has yielded a kenyapotamine hippopotamid, Palaeopotamus ternani (= Kenyapotamus ternani) (Pickford, 1983(Pickford, , 2007b(Pickford, , 2008(Pickford, , 2011Boisserie and Lihoreau, 2006;Boisserie, 2007;Boisserie et al, 2010;Weston and Boisserie, 2010). A few years ago, Orliac et al (2010) suggested that Morotochoerus from the lower Miocene of Uganda and Kulutherium from the lower Miocene of Kenya were representatives of primitive hippopotamids and tentatively assigned them to the Kenyapotaminae.…”