Carnivora from the Kanapoi hominin site, northern Kenya

Abstract

The assemblage from Kanapoi represents the most diverse early Pliocene carnivore assemblage from sub-Saharan Africa. Carnivora from Kanapoi were originally described by Werdelin (2003a), but continuing field work has brought to light significant new material from the site, shedding new light on the earliest post-Miocene radiation of Carnivora in Africa. Most importantly, a second species of Enhydriodon has been recovered from the site, including the first specimen to include a large part of the neurocranium. This makes Kanapoi the first site to include two species of this genus. This addition to the fauna will be of prime significance to understanding the ecology and evolutionary radiation of these giant, extinct otters. Other significant new finds include additional material of a wildcat-sized felid. Finds of this group are rare, and the new Kanapoi material adds significantly to our knowledge of the stem lineage of the genus Felis, which is widespread in Africa today.

Introduction

The Carnivora of Kanapoi were originally described by Werdelin (2003a) on the basis mainly of material collected by National Museums of Kenya expeditions in the 1990s, directed by Dr. Meave Leakey, with some additional specimens from the Harvard University expeditions in the 1960s directed by Dr. Bryan Patterson. Since the end of the 1990s, collecting at Kanapoi has continued on a smaller scale, led by one of us (FKM). This collecting has yielded additional carnivore material from the site, providing some significant additions to the fauna, including the first instance of two species of Enhydriodon in the same fauna. We have therefore prepared this contribution, to set these new finds in perspective and to take stock of the Kanapoi carnivoran sample as a whole.

The fossiliferous sediments at Kanapoi belong to the Kanapoi Formation, as defined by Feibel (2003). They consist of three sedimentary intervals: a lower fluviatile interval, a lacustrine interval, and an upper fluviatile interval. The stratigraphy and depositional setting of the Kanapoi sequence are discussed in detail by Feibel (2003). The Kanapoi sequence includes three dated tuffs (Leakey et al., 1998): a lower pumiceous tuff within the lower fluviatile interval, dated 4.17 ± 0.03 Ma, an upper pumiceous tuff just below the upper boundary of the lower fluviatile interval, dated 4.12 ± 0.02 Ma, and the Kanapoi Tuff at the top of the lacustrine interval, dated 4.07 ± 0.02 Ma. All of the carnivore specimens studied herein that have secured stratigraphic positions come from either the lower fluviatile interval or the lacustrine interval, with the exception of KNM-KP36600 (Homotherium sp.), which comes from the upper fluviatile interval.

Werdelin (2003a) noted that the majority of published eastern African early Pliocene (taken here as pre-Upper Laetolil beds, i.e., older than ca 3.85 Ma; Deino, 2011) mammal localities have few carnivore fossils associated with them. This is in marked contrast to the several rich Late Miocene localities such as Lothagam (Werdelin, 2003b), Lemudong’o (Howell and García, 2007) and the Lukeino Formation (Morales et al., 2005) in Kenya, and the Adu-Asa Formation in Ethiopia (Haile-Selassie and Howell, 2009). The situation has improved since 2003, however, with, e.g., the publication of carnivores from the informally named Mabaget Fm. overlying the Lukeino Fm. in Kenya (Morales et al., 2005). However, the assemblages from the early Pliocene still remain few and, more importantly, small. Therefore, any additions to these faunas are of great importance to the understanding of the first radiation of carnivores of modern aspect (i.e., post-Miocene) in Africa.