taxonID	type	description	language	source
03808792FFBFFF92FF150CEF90C3FF5D.taxon	description	Coryndon, 1978: 291, fig. 18: 7 B. Palaeopotamus gen. nov.; Pickford, 2007 b. Emended diagnosis: Differs from hippopotamine genera notably by: P 3 protocone formed by a single bulge of the lingual cingulum; molar wear pattern generally less trefoliate; relatively marked paraconule on upper molars; frequent occurrence of two ectometafossules at least on M 1; more complex trigonid (more cristids / fossids); postprotocristid less reduced, extending more distally; M 3 ectohypocristulid often expressed as few ectoconulids. Differs from anthracotheriids, palaeochoerids, and suids notably in the following character association: lower incisors with rounded transverse sections, lacking marked fossids on the crown; P 4 lacking a clear parastyle and a metacone, retaining a complex paracone with developed paracristae and fossae; frequent occurrence of ectostyles on upper molars, with a parastyle tending to fuse to mesiostyle; occurrence of small, multiple distal conids on lower premolars; a lower molar postmetacristid elongating toward the centre of the crown; presence of a posthypofossid. Discussion: The diagnosis proposed by Pickford (2007 b: 99) for Palaeopotamus, a monospecific genus defined for K. ternani, listed features that are also found in the late Miocene specimens (see, for comparisons, Figs 5, 7): upper molar protocone with an ‘ oblique anterior crest’ (preprotocrista) joining the mesial ‘ accessory cusplet in the centre line of the tooth behind the anterior cingulum’ (paraconule); deep sagittal valley, separating the labial and lingual cusps until quite deep wear; presence of labial and lingual ‘ basal pillars rising from the cingulum’ at the transverse valley (ecto- and entostyles); presence of a postmetaconule (distal ‘ hypoconule’); roots fused near the crown but separate root apices; deep mesial cingulum; on lower molars, mesial and distal cingulids well developed; the labial cingulid, although deep on the hypoconid, remains incomplete ‘ with only a few pimples of enamel showing its course’, except at the transverse valley where a ‘ basal pillar’ (ectostylid) occurs. Wear may have played a role in shaping some of the proposed diagnostic features: this is the case for the paracone crests orientated directly mesially and distally from the apex (pre- and postparacristae). In the M 3 Bar 2171 ′ 01, direct observation indicated a position of the paracone cristae similar to that of other kenyapotamines, whereas wear has destroyed the salient ridges topping the cristae and formed artificial ridges. The attenuation of the lingual and labial cingula on the upper molars could also be related to wear. In addition, the holotype of K. ternani (KNM-FT 3934, Fig. 5 F) exhibits well-developed, continuous cingula not limited to ‘ small pustules’, a trait that featured prominently in the initial diagnosis of K. ternani, that was not revised by Pickford (2007 b). Another proposed diagnostic trait is the ‘ small median accessory cusplet’ (mesoconulid) not blocking the centre of lower molar median transverse valley in Palaeopotamus. The difference in mesoconulid position between the late Miocene lower molars and those from Kipsaramon or Maboko (Fig. 7 C) is however not obvious, all, including the M 1 Bar 1186 ′ 99 (Pickford, 2007 b: fig. 6 B 2), having a similar central position on the crown. The mesoconulid of Bar 1186 ′ 99 actually appears more developed and differentiated than in other material. Consequently, none of the diagnostic features proposed for Palaeopotamus allow for a clear distinction from the late Miocene material attributed to K. coryndonae. The comparative analysis performed here indicated discrete morphological differences between K. ternani and K. coryndonae. These differences are minor compared to those distinguishing the different genera of Hippopotaminae, essentially based on craniomandibular features (Boisserie, 2005), and do not involve marked differences of crown structures as between Kenyapotamus and Hippopotaminae. Moreover, our analyses support the monophyly of the Kenyapotaminae, and in our opinion taxonomy should reflect the phylogeny. Therefore, we prefer retaining a distinction of specific rank only for the two known species of Kenyapotaminae. Given the scarcity of material, we concede that future discoveries of middle Miocene specimens may alter this conclusion, indicating multiple lineages within kenyapotamines and, possibly, a closer link for some of these lineages with Hippopotaminae. For the time being, however, there is no clear evidence of multiple lineages, and it seems more cautious to retain only one genus and to treat Palaeopotamus as a junior synonym of Kenyapotamus.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFB8FF92FF280F3191E7FF5D.taxon	description	2007 b: 99 – 101, figs 5 – 6. Geographical distribution: Kenyan Rift, Kenya, eastern Africa. Temporal distribution: Middle Miocene, roughly between 16 and 13.5 Mya. Attributed material: Fort Ternan: KNM-FT 3322 (left M 3); KNM-FT 3934 (right M 1 – holotype); KNM-FT 19089 (right P 2). Kipsaramon: Bar 211 ′ 02 (left P 3); Bar 759 ′ 02 (right dP 4) †; Bar 821 ′ 01 (left M 2) †; Bar 977 ′ 02 (left P 2) †; Bar 978 ′ 02 (left dP 4) †; Bar 1186 ′ 99 (left M 1) †; Bar 1458 ′ 01 (left M 1) †; Bar 2680 ′ 03 (mesial half of lower? molar); Bar 2171 ′ 01 (left M 3); Bar 2681 ′ 03 (left dP 3) †; KNM-TH 31008 (right lower canine fragment). Maboko: KNM-MB 864 (left M 1 or M 2); KNM-MB 865 (M 1 or M 2); KNM-MB 866 (right M 2); KNM-MB? (right P 4, Pickford, 1983: fig. 16) †. † indicates material attributed to K. ternani in the original publications (Pickford, 1983, 2007 b) not directly observed in this work. Emended diagnosis: Size smaller compared to K. coryndonae; no deep median indentation of P 3 labial cervix; upper molars with parastyle not mediomesial, distinct from mesiostyle; presence of salient postectohypocristid on lower molars more frequent than in K. coryndonae. Discussion: The proposed specimen attributions to K. ternani mostly follow Pickford (2007 b). Two new specimens were identified, bringing additional information: the fragmentary lower canine KNM-TH 31008 from Kipsaramon collected by the Baringo Paleontological Research Project, and the P 2 from Fort Ternan, KNM-FT 19089. However, the previous attribution of two specimens from Kipsaramon to K. ternani (Pickford, 2007 b) is considered to be uncertain. The unusual morphology of the left P 4 Bar 758 ′ 02 led us to refer it to K. cf. ternani, until the association to K. ternani of such P 4 morphology can be clearly demonstrated. The upper molar (?) Bar 1459 ′ 01 appears too fragmentary to warrant a certain attribution. It also seemed more cautious to identify it as K. cf. ternani.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFB8FF93FCB40F4F961BFCF9.taxon	description	‘ a genus of the Suidae similar to Bunolistriodon ’; Coryndon, 1978: 291, fig. 18: 7 B.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFB8FF93FCB40F4F961BFCF9.taxon	description	Kenyapotamus sp.; Pickford, 1990: pl. I. Nomenclatural remark: We followed Weston & Boisserie (in press) here and used a feminized species name, this species being named after a woman, Shirley Coryndon. Geographical distribution: Kenyan Rift, Kenya, and Afar depression, Ethiopia, eastern Africa; central Tunisia, northern Africa. Temporal distribution: Late Miocene, roughly between 10.5 and 8.5 Mya. Attributed material: Nakali: KNM-NA 187 (distal half of right M 3) †; KNM-NA 188 (right M 1); KNM-NA 192 (distal half of right lower molar); KNM-NA 194 (right lower premolar, most probably P 4); KNM-NA 203 (right P 3 or, maybe, P 4); KNM-NA 246 (right mandibular corpus with P 4, M 1, distal half of M 2, M 3); KNM-NA 247 (apical fragment of lower incisor). Ngeringerowa: KNM-BN 1289 (lower incisor fragment); KNM-BN 1320 (fragmentary right M 1 or M 2); KNM-BN 1321 (right M 3 – holotype with BN 2075); KNM-BN 1322 (fragmentary right M 1); KNM-BN 1323 (distal half of lower premolar); KNM-BN 1483 / 1487 (right P 2); KNM-BN 1489 (distal half of left M 1 or M 2); KNM-BN 1490 (right P 2 or P 3); KNM-BN 1492 (right P 2) †; KNM-BN 1493 (left P 4); KNM-BN 1494 (fragmentary palate with left M 1 and right M 2); KNM-BN 1715 (left P 3); KNM-BN 1717 (right P 1); KNM-BN 1802 (left P 4); KNM-BN 2075 (fragmentary right M 2 – holotype with BN 1321). Samburu Hills: KNM-SH 14789 (fragmentary left mandibular corpus with M 1 or, less likely, M 2); KNM-SH 14792 (fragmentary left mandibular corpus with M 1 and emerging M 2); KNM-SH 15850 (right M 1 or 2?) †; KNM-SH 15851 (left M 1); KNM-SH 15857 (fragmentary mandible with: two canine fragments, left P 3, P 4, fragmentary M 1, M 2, M 3; fragmentary right P 3, P 4, M 1, M 2, M 3); KNM-SH 18001 (fragmentary upper molar); KNM-SH 40142 (fragmentary right mandibular corpus with P 3 and P 4). Emended diagnosis: Exhibits features also found in Hippopotaminae: deep median indentation of P 3 labial cervix; upper molars with parastyle confounded or very close to mediomesial mesiostyle. Salient postectohypocristid on lower molars occurring infrequently. Molar crowns relatively shallower than in Hippopotaminae. Discussion: Some examined specimens from Ngeringerowa could be related to K. coryndonae, but their fragmentary condition did not warrant certain attribution. This was the case for two molar fragments, KNM-BN 1488 and KNM-BN 1601 (Fig. 5 G), as well as for KNM-BN 1353, a fragment of canine enamel. This fragment displays the fine ridging typical of hippopotamids, similar enamel thickness, and could be a portion of the linguomedial enamel band lining the distal groove of upper canines. If this identification was proven correct, this fragment would correspond to a canine similar in size to Archaeopotamus harvardi, i. e. larger than expected for K. coryndonae. We therefore referred these fragmentary remains to K. cf. coryndonae. Similarly, all postcranial remains identified as K. coryndonae (Fig. 8) should be better referred to K. cf. coryndonae until the discovery of clearly associated dental and postcranial material. KNM-NA 250 includes a canine fragment and right M 3 (Fig. 7 E), with morphologies similar to other specimens of K. coryndonae. However, the M 3 appears closer in size to KNM-FT 3322 (Fig. 7 F) attributed to K. ternani (dimensions of KNM-NA 250 M 3: mesiodistal length = 35.5 mm; mesial lobe maximal width = 20.0 mm). Given the incompleteness of the Fort Ternan specimen and the small available sample, we prefer to attribute KNM-NA 250 to K. cf. coryndonae. The dental remains of Kenyapotamus from the Beglia Formation were found to be of similar size to the dentition of K. coryndonae and most similar to specimens from Nakali (Pickford, 1990). We did not examine this material, but in our opinion its publication clearly demonstrated the occurrence of Kenyapotamus in northern African. However, it was not made clear whether the author preferred to attribute this material to ‘ K. coryndoni ’ or ‘ Kenyapotamus sp. ’ (Pickford, 1990: tab. I, pl. I). We have therefore retained here an attribution to K. cf. coryndonae. Closer affinities mentioned between specimens from Beglia and those from Nakali were proposed on the basis of higher molar crowns and a more robust P 4 with better developed metaconid and distal cuspids compared to those found at Ngeringerowa (Pickford, 1990). We could not identify a premolar displaying clear hippopotamid P 4 features in the material from Ngeringerowa (contra Pickford, 1983), whereas a figured Beglia molar (Pickford, 1990: pl. I E, F) exhibits a similar crown height as molars from Ngeringerowa and Nakali, with the exception of one specimen from the latter locality. KNM-NA 251 (Fig. 5 B) is a right M 3 moderately worn (all cusps display dentine isles) exhibiting significant difference in crown height to other specimens. Despite wear, the crown of KNM-NA 251 appears relatively as high as or higher than that of unworn molars from Nakali, Ngeringerowa, and Beglia. Its hypsodonty index was estimated to be similar to that of hippopotamines (H probably close to 80). This difference appears significant enough in morphofunctional terms to cast doubt on the attribution of this specimen to K. coryndonae. We prefer for now to refer it to K. aff. coryndonae. These proposed specimen reassignments are of little consequence to the existing taxonomy of late Miocene kenyapotamines. However, they may indicate a greater diversity amongst these kenyapotamines than initially thought, with the likely occurrence of two forms separated by crown height differences, and maybe of a third form characterized by its smaller size.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFBAFF90FF2E0C929744FAE0.taxon	description	Whatever the interpretation of the endometapremeta-preprotocristid complex evolution, it would have to be combined with a reduction of the postprotoconid to reach the condition seen in hippopotamines. Overall, this would represent quite significant modification of the trigonid in terms of dental morphofunctionality. For now, we do not have any concrete evidence of this evolution. If hippopotamines had derived from the late Miocene Kenyapotamus, such evidence should be looked for, together with the other modifications cited above, within a relatively short time interval, between about 9 and 7.5 Mya. Our observations and cladistic analyses, supporting a monophyletic Kenyapotamus, suggest a different scenario. The late Miocene forms could have developed their ‘ hippopotamine-like’ traits in parallel with a hypothetical hippopotamine lineage, whilst retaining or developing independently kenyapotamine features, such as the trigonid and the P 3 protocone morphologies. It is striking that KNM-NA 251 (Fig. 5 B), the most advanced known specimen of Kenyapotamus in terms of crown height, also exhibits one of the most complex patterns of cristae / fossae and conules, i. e. most different from the somewhat younger holotype of K. coryndonae (KNM-BN 1321, Fig. 5 A) and from hippopotamines. Regarding hippopotamine intragroup relationships obtained here, the paraphyly of Archaeopotamus agrees with Weston’s (2000) interpretation of the morphology of A. lothagamensis, advocating the basal position of this species within Hippopotaminae contra Boisserie (2005). This analysis, including mostly dental remains, did not take into account the mandibular morphological features on which Boisserie (2005) based the diagnosis of Archaeopotamus.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFBAFF91FC670BF1973DF8C8.taxon	description	Any putative close relationship between Doliochoerus, Palaeochoerus, and Taucanamo, on the one hand, and Kenyapotamus, on the other, appears to be unsupported. In a recent informal phylogeny, Pickford & Tsujikawa (2005: fig. 3 D) indicated that a sistergroup relationship between palaeochoerids and Hippopotamidae was supported by the ‘ posterior groove in upper canines’ and ‘ the partial fusion of roots immediately beneath molars forming a substantial base to the crowns’. Unfortunately, an upper canine distal groove is not known in palaeochoerids except in Schizochoerus. First, this genus displays a specialized, bilophodont cheek tooth morphology (see Fig. 1 H and Pickford, 1978), making it a particularly unlikely stem for Hippopotamidae. Second, its affinities amongst suoids appear unclear. Although it was initially described as a suid (Crusafont & Lavocat, 1954), since then it has been considered as an ‘ Old World tayassuid’ (Pickford, 1978) or palaeochoerid (Made, 1997). A recent cladistic analysis however placed it back within Suidae (Orliac, 2007). The position of Shizochoerus within Suoidea was not resolved in our analysis, we thus remain cautious regarding its actual affinities in the superfamily. The second feature mentioned by Pickford & Tsujikawa (2005), partial root fusion, in support of a clade (palaeochoerids + Hippopotamidae) does apply differently to hippopotamids and Doliochoerus, Taucanamo, and Palaeochoerus. In these three latter genera, roots display a complete fusion and form only one structure (lingual roots on the upper molars, mesial roots and distal roots on the lower ones), and only labial upper molar roots remain unfused and completely free. Hippopotamids (including Kenyapotamus) exhibit variable partial fusion with apices always remaining free, and the partial fusion pattern can vary amongst specimens. This condition is also seen in all examined anthracotheriids, except in Merycopotamus and Libycosaurus where the fusion is more similar to that found in palaeochoerids. In order to further assess hypotheses linking hippopotamids with suoids, we ran some phylogenetically constrained analyses (see Supporting Information). We tested the ‘ tayassuid hypothesis’ as formulated by Pickford (1989). Such a scenario was shown to require no fewer than 55 additional steps compared to the unconstrained phylogenetic hypothesis. Similarly, any grouping of hippopotamids with suoids would require 14 additional steps, whereas any clade formed by hippopotamids and palaeochoerids (excluding Schizochoerus) would require 25 additional steps (or 21 if including Schizochoerus). We therefore reject exclusive affinities between Suoidea (Tayassuidae + Suidae + palaeochoerids) and Hippopotamidae on the basis of dental characters following a careful analysis of the material corner- stone to the ‘ tayassuid’ then ‘ palaeochoerid’ hypotheses, i. e. that of Kenyapotamus. Close affinities between Suoidea and Hippopotamidae were also previously rejected on the basis of a character sample dominated by craniomandibular characters (Boisserie et al., 2005 a, b). Furthermore, a reanalysis of the most complete previous data matrix (Boisserie et al., 2005 b), without dentally based characters, also led to a clade (Hippopotamidae + Anthracotheriidae) that excluded suoids. To demonstrate that hippopotamids emerged within Suoidea, it would be necessary to: exhaustively discuss the characters and their states presented here, as well as those presented by Boisserie et al. (2005 a, b), and demonstrate that they are incorrect or homoplastic; find a significant amount of synapomorphies between Hippopotamidae and any suoid; explain how extant hippopotamids can overall display stronger molecular affinities with extant cetaceans and ruminants than with extant suids and tayassuids (amongst an abundant literature, see notably Irwin & Arnason, 1994; Gatesy et al., 1996; Ursing & Arnason, 1998; Nikaido, Rooney & Okada, 1999; Arnason et al., 2000; Gatesy & O’Leary, 2001; Arnason, Gullberg & Janke, 2004; Price, Bininda-Emonds & Gittleman, 2005; Marcot, 2007). The purpose of the cladistic analysis was to decipher the relationships of Kenyapotaminae, not to resolve the phylogeny of Suoidea. However, some results on suoid intragroup relationships call for some comments. Regarding the relationships amongst the palaeochoerids (excluding Schizochoerus), the loss of the ventral vascular groove of the mandible (character 3) seems less likely than a reduction of the P 4 mesiostylid. The former is found in some peccaries as part of a complex adaptation to wide gape and implies significant additional musculoskeletal specializations of the whole skull (Herring, 1975) – the lack of a vascular groove in Hexaprotodon and Libycosaurus could be linked to a different solution for achieving a wide gape, with a ramus angular process particularly developed and everted. The topology [(Doliochoerus, Taucanamo), Palaeochoerus] could therefore appear somewhat more parsimonious, with a parallel evolution of the vascular groove in Taucanamo and Pecari (as well as in some anthracotheriids and hippopotamids). However, a satisfying resolution of palaeochoerid intragroup relationships requires consideration of additional evidence. Finally, the position of the tayassuid P. tayacu as sister group of palaeochoerids (excluding Schizochoerus) is interesting, as palaeochoerid affinities with New World tayassuids have been postulated for a long time (Pearson, 1927). A resolution of this question would require further comparison of fossil tayassuids from northern America with palaeochoerids.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFB4FF9CFF3E0EB1918EFCF9.taxon	description	The reassessment of kenyapotamine affinities was a particularly good opportunity to test hippopotamid relationships within artiodactyls on a wide array of cheek tooth characters and by the means of a formal cladistic analysis. A deep nesting of hippopotamids within bothriodontines was also obtained in previous works essentially based on craniomandibular features (Boisserie et al., 2005 a, b). This and previous analyses (Boisserie et al., 2005 a, b) included Libycosaurus within the sister group of Hippopotamidae, alone or with other bothriodontines. A close phylogenetic relationship between Libycosaurus and Hippopotamidae has been recently criticized (Pickford, 2006: 270): ‘ The anteriormost “ premolar ” (Pacc) in Libycosaurus represents a new acquisition, unique to Libycosaurus among artiodactyls, which primitively possess only four upper premolars. Incidentally, this strange dental acquisition provides strong evidence that Hippopotamidae have no close phylogenetic relationship to Libycosaurus, because in hippos there are only four (or three) premolariform teeth anterior to the M 1 /, and not five as in Libycosaurus. ’ The author is correct in depicting this structure as quite unique amongst artiodactyls – it is indeed an autapomorphic trait of Libycosaurus (Lihoreau, 2003; Lihoreau et al., 2006). However, the reasoning behind his phylogenetic argument is difficult to understand. The author would be correct if he had criticized a hypothesis presenting Libycosaurus as the forerunner of Hippopotamidae, but to our knowledge, no past or recent publications have suggested this. If his argument was put forward to refute the presence of Libycosaurus within the sister group of Hippopotamidae, this would similarly mean that Libycosaurus could not figure within the sister group of either anthracotheriids or artiodactyls, or of any known placental mammal younger than the late Cretaceous (Novacek, 1986), a suggestion probably not intended by Pickford (2006). More generally, the same author provided a list of differences and similarities amongst Hippopotamidae, palaeochoerids, and Anthracotheriidae (Pickford, 2007 b: table 8) in support of the following view: ‘ the supposed synapomorphies between hippos and anthracotheres cited by Boisserie et al. (2005 b) are either incorrectly reported or are more likely to be parallelisms’ (Pickford, 2007 b: 103). These features and their derived or primitive conditions were unfortunately not discussed, nor illustrated. This is highly regrettable, as we did discuss and illustrate many of them in a contribution (Boisserie et al., 2005 a) apparently ignored by Pickford (2007 b), despite the fact that the manuscript was cited in the publication he criticized (Boisserie et al., 2005 b). Another paper (Pickford, 2006), providing a detailed review of the anatomy of Libycosaurus anisae, and summarized by Pickford (2007 b: table 7), was also cited against the phylogenetic hypothesis presented by Boisserie et al. (2005 b). We would simply note that: (1) previous works by Boisserie et al. (2005 a, b) did not discuss the affinities of Libycosaurus anisae, but those of Libycosaurus petrocchii; (2) unpolarized character differences observed between a single species of anthracotheriid and Hippopotamidae (for which the comparative sample was not mentioned by Pickford, 2006) are not sufficient to invalidate an emergence of Hippopotamidae within Anthracotheriidae – a result obtained even when Libycosaurus was removed from the present data matrix and from those of Boisserie et al. (2005 a, b). Similarly, we note that the recently suggested systematic changes within Libycosaurus (Pickford, 2008), not followed here, would not have any impact on this phylogenetic hypothesis. Other studies, addressing the more general relationships between cetaceans and artiodactyls, did not recognize exclusive relationships between Anthracotheriidae and Hippopotamidae (O’Leary, 1999, 2001; O’Leary & Geisler, 1999; Geisler, 2001; Geisler & Uhen, 2003, 2005; Theodor & Foss, 2005; Geisler et al., 2007). However, these studies did not consider the full diversity of taxa characterizing Anthracotheriidae, and represented them mostly by northern American taxa excluding Eurasian anthracotheriines and bothriodontines – an issue acknowledged by Geisler et al. (2007). Three Eurasian anthracotheriids were incorporated by Thewissen et al. (2007). None of them belong to Eurasian bothriodontines, and two of them, Anthracokeryx and Microbunodon, belong to the Microbunodontinae, a subfamily distinct from other anthracotheriids in displaying evolutionary trends analogous to those of moschids and tragulids (Lihoreau & Ducrocq, 2007). The resulting phylogeny did not support a particularly close affinity between anthracotheriids and hippopotamids. In contrast, O’Leary & Gatesy (2007) followed Boisserie et al. (2005 a, b) in incorporating a number of Eurasian anthracotheriids, including Eurasian bothriodontines (Merycopotamus, Libycosaurus, Bothriogenys). Their results were broadly similar to ours, supporting close affinities between hippopotamids and most anthracotheriids, and excluding suoids from this relationship. However, some of their results appear inconsistent with ours. Notably, the position of Libycosaurus was most often not found in a clade with other anthracotheriids and Hippopotamidae, suggesting a polyphyletic Anthracotheriidae. This situation constitutes a major discrepancy with our results and other works nesting Libycosaurus within Bothriodontinae (Pickford, 1991; Lihoreau & Ducrocq, 2007). This issue illustrates more generally the incongruence between the relationships within Anthracotheriidae obtained by O’Leary & Gatesy (2007) and ‘ classical’ views on the phylogeny of the family (Black, 1978; Pickford, 1991; Lihoreau & Ducrocq, 2007). In our opinion, the former should not be validated until further substantiation based on exhaustive reassessment focusing on material relevant to the family Anthracotheriidae. Furthermore, we are convinced that the proper resolution of hippopotamid relationships requires the consideration of hippopotamid evidence beyond that included in the analyses cited above, i. e. solely the two extant species. Hippopotamus and Choeropsis may appear different enough to broadly represent the family Hippopotamidae but they are, nevertheless, representatives of lineages with peculiar adaptations and evolutionary histories (Boisserie, 2007; Weston & Boisserie, in press). They should not be viewed as approximations of earlier species from the family, which in our opinion, provide more reliable data for resolving hippopotamid origins. The results reported here and those of Boisserie et al. (2005 b) independently offer support to a close relationship between crown bothriodontines (including Merycopotamus and Libycosaurus) and Hippopotamidae, as one analysis of the present data matrix, performed after exclusion of characters shared with the data matrix of Boisserie et al. (2005 b) yet still led to a similar result (66 characters remaining, see Supporting Information). Furthermore, cheek tooth characters alone support an emergence of hippopotamids within bothriodontines, a situation which may have been regarded as counterintuitive (Boisserie & Lihoreau, 2006), but was foreseen by Colbert (1935). Of course, a scenario explaining the evolution of hippopotamid dentition from a bothriodontine dentition would depend on which bothriodontines are included within the sister group of Hippopotamidae. Crown bothriodontines as sister group of Hippopotamidae The complete data matrix analysis indicated that the sister group of Hippopotamidae included solely Libycosaurus and Merycopotamus, i. e. the most advanced Old World bothriodontines (or crown bothriodontines), to the exclusion of the other anthracotheriids considered in this work (Fig. 9). This topology is based mainly on craniomandibular and frontal dentition character changes: width of mandibular symphysis (2: 1); about constant corpus height (4: 1); cylindrical roots of lower incisors (7: 0, to be lost in Merycopotamus); and large lower canines, at least in males, reaching below P 3 – P 4 and enamel extensively covering the crown (11: 1, 12: 1, 13: 1). In previous contributions (Boisserie et al., 2005 a, b), a close relationship of Hippopotamidae with crown anthracotheriids was largely established on features from the same morphocomplexes. Notably, a reversal of the cylindrical lower incisor roots in Merycopotamus does not appear likely, and we favour the parallel evolution of this trait in Libycosaurus and Hippopotamidae. In addition, dental features that support the clade (Hippopotamidae + crown bothriodontines) are: the presence of one to several postparaconules on the P 3 (23: 1); the partial fusion of the lingual and the distolabial roots on the P 4 (31: 1) – an ambiguous synapomorphy not verifiable for middle Miocene Kenyapotamus and A. lothagamensis; the great reduction or loss of the upper molar paraconule (44: 2); and the great reduction or loss of the premetacristid on M 1 - 2 (69: 1). Two reversals would have therefore occurred in Kenyapotamus: the complete redevelopments of the paraconule and of the premetacristid. Once again, this seems an unlikely scenario perhaps better interpreted as parallel losses. This close relationship with crown bothriodontines fits scenarios proposed by Gaziry (1987) and Boisserie & Lihoreau (2006). They suggested that the origin of Hippopotamidae may be looked for within early to middle Miocene African bothriodontines including Afromeryx and Sivameryx. First, this hypothesis involves a certain degree of parallelism in craniomandibular structures (e. g. high orbits) between hippopotamids and crown bothriodontines, in particular Libycosaurus (see Boisserie et al., 2005 a, b). Second, it also relies on a relatively complex modification of the cheek tooth pattern as discussed above and by Boisserie & Lihoreau (2006). In this regard, examin- ing the phylogenetic signal using only cheek tooth characters was an important test. Advanced bothriodontines as sister group of Hippopotamidae This test resulted in two conflicting phylogenetic hypotheses (see Supporting Information). Half of 14 resulting trees displayed the same topology as that shown in Figure 9. In contrast, the other half exhibits a sister group of Hippopotamidae that includes crown bothriodontines and Elomeryx (‘ advanced bothriodontines’; Fig. 10). This would indicate a possible emergence of Hippopotamidae within more basal bothriodontines, relatively close to Bothriogenys. The clade grouping Hippopotamidae and their sister group would be defined by the loss of the upper molar ectometacristule (48: 2); the occurrence of a metaconid on P 3 (54: 1); and the shallow ectoprotofossid on M 1 - 2 (66: 1). The occurrence of one or several P 3 postparaconules (23: 1) and the upper molar paraconule reduction (44: 1) would be retained as ambiguous clade support. This topology would not require a redevelopment of labial cingulum structures on hippopotamid upper molars. In fact, as discussed in Appendix 2 (character 34), this structure may not have disappeared in advanced bothriodontines, but simply merged with the extensions of the postparacristae and premetacristae. This situation differs from the simple cingular structures observed in Bothriogenys and Hippopotamidae. Similarly, this topology involves: no reappearance of the postprotofossid on P 4 in Hippopotamidae, but its presence as a plesiomorphic state found in anthracotheriines and basal bothriodontines, lost in more advanced bothriodontines; and no reversal in Kenyapotaminae of the paraconule reduction and of the important trigonid modifications evolving in parallel within the Hippopotaminae and crown bothriodontines. Most probably, the paraconule loss occurred independently on multiple occasions within Anthracotheriidae (Lihoreau & Ducrocq, 2007). This reduction may also have followed parallel pathways in basal hippopotamines and within crown bothriodontines, and a similar scenario may have applied to the evolution of the trigonid. The fusion of the P 4 roots would also have occurred independently within crown bothriodontines and Hippopotamidae. If we extrapolate for noncheek-tooth characters, this topology (Fig. 10) implies that the development of the mandibular symphysis and lower canines could have been reversed in Elomeryx, or been acquired in parallel in Hippopotamidae and crown bothriodontines. Similar parallelism would be found for: the cylindrical lower incisor root (developed in Hippopotamidae and Libycosaurus only); the constant mandibular corpus height; the extension of the enamel band to the whole length of the lower canine. An emergence of Hippopotamidae within basal bothriodontines (Fig. 10) seems ‘ dentally more realistic’ than the scenario derived from the complete data matrix analysis. A dental transition could be relatively easy to imagine, especially if it involved cheek tooth enamel thickening (Boisserie & Lihoreau, 2006). However, this scenario implies a parallelism between hippopotamines and crown bothriodontines greater than previously suggested (Boisserie et al., 2005 a, b), affecting more cranial and dental structures. This parallelism would appear to be particularly extreme between Libycosaurus petrocchii and the most advanced Hippopotaminae, such as Hippopotamus (Boisserie et al., 2005 a). This situation could have resulted from the occupation of the same niche – in this case, that of semiaquatic large herbivores – by species with closely related genomes and sharing close social organizations (i. e. structured herds, with some form of segregation between males and females).	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFB6FF9DFCD70DEA9108FA46.taxon	description	Asian helohyids were suggested to have a sister or stem group relationship with Anthracotheriidae (see, e. g. Coombs & Coombs, 1977 b; Ducrocq et al., 1997). These putative relationships were not confirmed here, essentially in relation to paraconid loss (81: 1) in all taxa except Gobiohyus and the outgroup. The exclusion of this character led to eight equally parsimonious trees (287 steps) including two with the position previously observed and six with a clade (Gobiohyus + Cebochoerus + Hippopotamoidea). In four of these trees, Gobiohyus was found within the sister group of Hippopotamoidea (with Cebochoerus in two trees, alone in the remaining). Independent paraconid loss should not be excluded, as it probably occurred on several occasions, so we cannot reject for now a relatively close relationship between Hippopotamoidea and Asian helohyids. The results do not agree with Pearson’s (1927) hypothesis of hippopotamid emergence from the archaic Cebochoeridae, but indicate a close relationship between Cebochoerus and the Hippopotamoidea, previously not supported by Boisserie et al. (2005 a, b). Interestingly, Theodor & Foss (2005) emphasized the presence of deciduous dental structures (accessory denticles) in cebochoerids found also in deciduous and permanent dentitions of archaic cetaceans (archaeocetes). These results definitely underscore the need for a better understanding of hippopotamoid affinities amongst Eocene artiodactyls from Eurasia. What is at stake exceeds the simple problem of anthracotheriid origins, and concerns the larger question of relationships amongst major terrestrial, semi-aquatic, and aquatic radiations amongst paraxonians. Eocene archaic artiodactyls, including the earliest known anthracotheriids, are particularly diverse and, most often, not well known. This makes their phylogenetic relationships particularly difficult to resolve. The discovery of complete remains of the raoellid Indohyus brought an apparently radical resolution of cetacean origins (Thewissen et al., 2007). It is quite possible that equivalent future discoveries will alter this resolution in a similarly dramatic way. It also shows that beyond morphology, the palaeoecology of archaic artiodactyls can be enlightening. That of the earliest anthracotheriids needs further exploration: it would not be surprising if at least some of them were found to be semiaquatic, as for Indohyus (Thewissen et al., 2007), given the repeated developments of semiaquatic adaptations in Hippopotamoidea. Raoellids have previously been related to anthracotheriids and helohyids (for a summary of and contra this hypothesis, see Sahni et al., 1981). Geisler et al. (2007) suggested close relationships amongst cetaceans, hippopotamids, raoellids, helohyids, anthracotheriids, cebochoerids, and Mixtotherium. This view was partially supported by O’Leary & Gatesy (2007), who also found close relationships amongst hippopotamids, some anthracotheriids and helohyids, and raoellids, as well as entelodonts and Andrewsarchus. A better understanding of the exact phylogenetic relationships amongst these taxa and others (including mesonychians and archaic ruminants) should lead to a cetartiodactyl phylogeny congruent with the relationships amongst extant cetaceans, hippopotamids, and ruminants suggested by molecular-based studies.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFB7FF9DFF4C080D919DF9DD.taxon	description	HIPPOPOTAMOID EVOLUTION Boisserie & Lihoreau (2006) described two phylogenetic scenarios of hippopotamid origins relying on different biogeographical events. The first one proposed the migration from Asia to Africa of a common ancestor exclusive to Libycosaurus and Hippopotamidae after 15 Mya. This scenario seems unlikely because: (1) our phylogenetic results do not support Libycosaurus as exclusive sister group for the Hippopotamidae; (2) confirmation of K. ternani within Hippopotamidae implies a first appearance datum possibly as early as 16 Mya. The second scenario corresponded to the emergence of Hippopotamidae within advanced bothriodontines, i. e. with a sistergroup relationship between Hippopotamidae and crown bothriodontines. In this case, the bothriodontine forerunners of Hippopotamidae and African advanced bothriodontines would have probably migrated from Asia during the early Miocene, closely to the first appearance of advanced bothriodontines Sivameryx and Afromeryx in eastern and northern Africa (see Fig. 11, hypothetical relation 1). This would correspond to the first main faunal interchange between Eurasia and Africa triggered by firm land bridge formation around 18 ± 1 Mya (Thomas, 1985; Rögl, 1999). Compared to an emergence within advanced bothriodontines, a scenario relating Hippopotamidae to archaic bothriodontines would rely on quite different spatial and temporal grounds (Fig. 11, hypothetical relation 2). It would potentially link the origins of Hippopotamidae to anthracotheriids found in Africa as early as the late Eocene (Lihoreau & Ducrocq, 2007). These anthracotheriids include Bothriogenys and Quatraniodon from the Jebel Qatrani Formation, Fayum, Egypt (early Oligocene, see Ducrocq, 1997; Seiffert, 2006), Brachyodus (early to middle Miocene, Lihoreau & Ducrocq, 2007), and potentially other nondescribed material (e. g. Sanders, Kappelman & Rasmussen, 2004). Brachyodus exhibits a derived dental morphology (modified anterior dentition, extremely developed styles on upper molars, see Dineur, 1981) probably excluding it from the lineage that led to Hippopotamidae. However, the Fayum anthracotheriids could represent the stem for a putative anthracotheriid lineage, the stem group of Hippopotamidae. Unfortunately, the African anthracotheriid fossil record from the upper Oligocene and the lowermost Miocene is particularly poor. The presence of a relatively bunodont anthracotheriid in the lower Miocene of Kenya (Coryndon, 1978 a, b; Pickford, 2007 a) is of interest with regard to this scenario, but relies on quite fragmentary remains and its affinities within Anthracotheriidae need to be clarified.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
03808792FFB7FF9BFCBC08C090F0FCE7.taxon	description	Unfortunately, the ecology of kenyapotamines remains largely unknown. To date, the most reliable data come from analyses of enamel stable isotopic content performed by Harris et al. (2008) on some late Miocene kenyapotamine specimens. They notably show that the 18 O / 16 O ratio, a parameter complexly linked to water dynamics in habitats and diets, is not significantly different in kenyapotamines and hippopotamines. This suggests similar semiaquatic habits in both subfamilies, but it is not possible to conclude firmly without comparing these stable isotope results with more general ones obtained for the complete faunas including Kenyapotamus. The last known remains of Kenyapotamus predate the ‘ hippopotamine event’. This event corresponds to the sudden appearance around 7.5 Mya of particularly abundant, fully evolved hippopotamines dominating local wet ecosystems in the Arabo-eastern African and northern central African fossil records (Boisserie, 2006; Weston & Boisserie, in press). This event may be an artefact of incomplete fossil records, the result of a punctuated equilibrium, a dramatic increase of hippopotamine abundance in relation to environmental changes, or a combination of these effects. Earliest known hippopotamines represented a considerable biomass in depositional environments, were relatively diversified, and were characterized by a distribution extended at least to the northern half of the continent. These elements seem in favour of an emergence of ‘ true’ hippopotamines well before the ‘ hippopotamine event’. Morphology tends to support this view: late Miocene kenyapotamines seem indeed a less suitable stem group for Hippopotaminae than middle Miocene ones, suggesting a deeper hippopotamine evolutionary history. Resolution of this question will probably come from new discoveries, either of a form transitional between K. coryndonae and late Miocene hippopotamines, or, more likely in our opinion, of a hippopotamine lineage contemporary to the late Miocene Kenyapotamus. Expansion of Hippopotamidae outside Africa is recorded only at the terminal Miocene, after the ‘ hippopotamine event’, to southern Europe and southern Asia (Fig. 11). Maximal distribution of the family was reached during the Pleistocene, with Pan-African distribution, presence of Hippopotamus in western to south-eastern European and south-western Asia, and extension of Hexaprotodon from southern Asia to south-eastern Asia (Kahlke, 1990; Boisserie, 2007). It would be important to look for Mio-Pliocene hippopotamid remains in south-western Asia in order to complete the biogeographical history of the family.	en	Boisserie, Jean-Renaud, Lihoreau, Fabrice, Orliac, Maeva, Fisher, Rebecca E., Weston, Eleanor M., Ducrocq, Stéphane (2010): Morphology and phylogenetic relationships of the earliest known hippopotamids (Cetartiodactyla, Hippopotamidae, Kenyapotaminae). Zoological Journal of the Linnean Society 158 (2): 325-366, DOI: 10.1111/j.1096-3642.2009.00548.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00548.x
