Enamel microstructure evolution in anthracotheres (Mammalia, Cetartiodactyla) and new insights on hippopotamoid phylogeny

Abstract

Investigations on enamel microstructure provided new data for the debate on hippopotamid origin. Observations indicated a diversity of patterns relevant to phylogenetic inferences. Within Hippopotamoidea, the distribution of these patterns seems to be in favour of a hippopotamid origin within the Palaeogene African anthracotheres. Enamel microcharacters therefore prove to be particularly relevant for future phylogenetic analysis of the superfamily, and have implications for our understanding of ecological transitions within hippopotamoids at the end of the Miocene. Indeed, unlike equids or bovids, which developed grass feeding thanks to their hypsodont molars, hippopotamoids may have had another way to exploit this resource. The combination of inter‐row sheets, which appeared early in the evolutionary history of the group, and the increased thickness of radial enamel could have eased the consumption of highly abrasive graminoids. © 2014 The Linnean Society of London

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

“…Our phylogenetic study allows formal identification of the archaic bothriodontines as stem group of the Hippopotamidae (in accordance with some of the hypotheses discussed in refs 10,11,26). First, this placement unveils the complete evolutionary changes that led to the hippopotamid dental morphology.…”

“…1 Enamel microstucture investigations. We followed the methodology, nomenclature and comparative materials described in Alloing-Séguier et al 26 Two thin sections were performed: a horizontal one and a vertical one (Supplementary Note 3, Supplementary Fig. 2).…”

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

“…There are no buccal or lingual cingulids. The enamel is not thick proportionally to the tooth size (Alloing-Séguier et al, 2014); the maximum thickness is about 1.3 mm, judging from the natural breakage of the cross section ( Figure 1G). …”

“…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).…”

Characteristics of the transverse 2D uniserial arrangement of rows of decussating enamel rods in the inner enamel layer of mouse mandibular incisors

“…; Alloing‐Séguier et al. ). In the past half century, the shape and arrangement of enamel rods have also been of special interest as potential indicators of the pathways ameloblasts follow in secreting the enamel layer (Boyde, ; Osborn, ; Warshawsky, ; Risnes, ; Radlanski & Renz, ; Hanaizumi et al.…”