Three genera of hyracoids were recorded from the Early Miocene of East Africa by Whitworth [18], but there has been considerable divergence of opinion about their status. Despite differences in cranial and dental morphology from Megalohyrax and Bunohyrax, Whitworth [18] classified two species in these genera that are recorded from much earlier deposits (Early Oligocene) in the Fayum, Egypt. One of his genera (Meroehyrax) was new. His classification has been the subject of debate, with some researchers [6,13] doubting the hyracoid status of one of his species (Bunohyrax sp), and changing the generic status of another (Megalohyrax championi). Meyer [6] recorded a fourth genus (Prohyrax) from Kenya, linking it to material from Namibia described by Stromer [16,17]. New samples of two hyracoid species collected by the Uganda Palaeontology Expedition throw light on their systematic position and taxonomy. It is concluded that there are three hyracoid genera (Afrohyrax, Brachyhyrax and Meroehyrax) in the Early Miocene deposits of East Africa, the first two of which are new. A fourth genus (Prohyrax) occurs in southern Africa, but is not reliably known from East Africa. .
Révision des Hyracoidea (Mammalia) du Miocène inférieur de l'Afrique de l’Est. Trois espèces d’Hyracoidea ont été signalées dans le Miocène inférieur d’Afrique orientale par Whitworth [18]. Malgré des différences importantes de la morphologie cranio-dentaire, deux des espèces kenyanes étaient classées dans Megalohyrax et Bunohyrax, genres connus dans les dépôts beaucoup plus anciens du Fayoum en Égypte. Le troisième genre décrit par Whitworth (Meroehyrax) était nouveau. La classification proposée [18] a été débattue ; certains auteurs [6,13] ont remis en cause le statut d’Hyracoïde d’une de ses espèces et ont modifié le statut générique d’une autre. Meyer [6] a signalé un quatrième genre (Prohyrax) au Kenya, sur la base des ressemblances avec le genre namibien décrit par Stromer [16,17]. De nouveaux spécimens récoltés par l’Uganda Palaeontology Expedition permettent d’éclaircir la position systématique et la taxonomie de deux des espèces. Nous concluons qu’il n’existe que trois genres d’Hyracoïdes dans les dépôts du Miocène inférieur d’Afrique orientale (Afrohyrax, Brachyhyrax et Meroehyrax), dont les deux premiers sont nouveaux. Par ailleurs, un quatrième genre (Prohyrax) est connu d’Afrique australe. .
Hyracoidea, East Africa, Early Miocene, Taxonomy, SystematicsHyracoidea, Afrique de l’Est, Miocène inférieur, Taxonomie, SystématiquepresentedPrésenté par Yves CoppensVersion française abrégéeIntroduction
Dans son étude pionnière des hyracoïdes est-africains, Whitworth [18] a décrit trois genres. Le matériel le plus commun a été attribué à l’espèce créée par Arambourg [2], Pliohyrax championi, que Whitworth a transférée dans le genre Megalohyrax. Deux des espèces décrites par Whitworth [18], Meroehyrax bateae et Bunohyrax sp., étaient fondées sur des échantillons restreints et leurs affinités sont restées suspectes. Ainsi, Meyer [6] pensait que Prohyrax était un synonyme de Meroehyrax, en raison du fait que le premier n’était connu que par des dentitions supérieures, et le second, que par des dentitions inférieures. Il a également transféré l’espèce championi dans le genre Pachyhyrax, et pensait que le matériel de Bunohyrax décrit par Whitworth n’appartenait pas à un hyracoïde [13].
Des échantillons plus complets de Prohyrax tertiarius de Namibie [11], comprenant des restes mandibulaires et maxillaires, montrent que Meroehyrax et Prohyrax sont très différents morphologiquement, malgré leur taille comparable. Ce résultat est confirmé par la description de pièces exceptionnellement complètes de l’espèce namibienne de plus grande taille (Prohyrax hendeyi) [9].
Parmi les fossiles récemment récoltés dans le Nord-Est de l’Ouganda (Napak, Moroto II), de nouveaux spécimens appartenant à Meroehyrax et à l’espèce de Bunohyrax décrite par Whitworth [18] ont été reconnus. Bien que les échantillons soient peu nombreux, ils sont assez représentés pour permettre une révision de leur statut taxonomique et de leur position systématique.
Descriptions systématiques
Ordre Hyracoidea Huxley, 1869
Sous-ordre Pseudhippomorpha Whitworth, 1954
Famille Geniohyidae Andrews, 1906
Genre Brachyhyrax nov.
Espèce type :Brachyhyrax aequatorialis sp. nov.
Synonymie :Bunohyrax sp. Whitworth, 1954, p. 25, Pl. 7, Fig. 3.
Bunohyrax sp. Meyer, 1978, p. 297.
Bunohyrax from East Africa, Rasmussen, 1989.
Diagnose : Hyracoïde qui se caractérise par des dents jugales supérieures aux cuspides buccales brachyodontes, parastyle réduit, situé en position antérieure par rapport au paracône, mésostyle plus bas que la crête, unissant le paracône au métacône, à faible métastyle, des molaires supérieures au contour occlusal carré, sans éperon lingual au paracône et au métacône, préprotocrista et postprotocrista presque alignées, mésoprotocrista gonflée, à l’hypocône avec une préhypocrista bien développée et une posthypocrista plus faible, avec un repli d’émail lingual entre le protocône et l’hypocône, vallée longitudinale aux molaires supérieures presque droite et sans encombrement, prémolaires supérieures avec des lophes postérieurs courts antéro-postérieurement (hypocône et métacône réduits), dents jugales inférieures au lophe antérieur, beaucoup plus court que le postérieur, lui-même plus bas que l’antérieur.
Derivatio nominis :Brachy fait référence à la brachyodontie des cuspides buccales aux dents jugales supérieures ; hyrax est le nom commun anglais pour les hyracoïdes actuels.
Espèce Brachyhyrax aequatorialis nov.
Diagnose : la même que celle du genre.
Derivatio nominis :aequatorialis fait référence à la situation géographique du matériel connu de l’espèce.
Holotype : M 21340, molaire supérieure gauche, probablement une M2/ (n° de terrain Sgr 311′49, et non pas Sgr 311′48, ainsi que l’a rapporté Whitworth [18]) (Fig. 1, 1).
Matériel référé : Sgr 924′47 ?, prémolaire inférieure gauche ; Nap XVIII 4′85 prémolaire supérieure gauche ; Nap I 102'02, prémolaire supérieure gauche ; Nap IV 64, m/3 gauche sans hypoconulide ; Nap IV 64 extrémité distale de tibia ; Nap V 84′02, deuxième phalange (Fig. 1, 2–7) (Tableau 1).
Localité type : Songhor, Kenya.
Âge : Miocène inférieur (ca 20–19 Ma).
Autres localités : Napak I, Napak IV, Napak V, Napak XVIII (Ouganda).
Discussion : Whitworth [18] a décrit et illustré deux dents qu’il attribua à Bunohyrax sp. Meyer [6] critiqua l’attribution générique des spécimens, car les dents étaient très différentes de celles des autres espèces de Bunohyrax ; il a même remis en cause l’attribution des pièces aux Hyracoidea, position confirmée par Rasmussen [13]. Il rapporta un des spécimens à un Anthracotheriidae (KNM RU 343) ; toutefois, cette pièce est en fait une dM4/ déciduale gauche de Kenyasus rusingensis [8].
Le nouvel hypodigme consiste en une collection homogène d’hyracoïdes chez qui les dents supérieures sont brachyodontes et les inférieures brachysélénodontes. Les seuls autres hyracoïdes qui se rapprochent, même de loin, de Brachyhyrax sont Selenohyrax et Geniohyus du Fayoum en Égypte [14], ainsi qu’un hyracoïde indéterminé provenant du sultanat d’Oman [12]. Parmi les ressemblances, il faut signaler, aux molaires inférieures, les lophides médiaux raccourcis par rapport aux distaux allongés, ainsi qu’une crête linguale gonflée (mésohypocristide) à l’hypoconide, qui s’étend vers la base du bassin du talonide.
Brachyhyrax ne ressemble à aucun hyracoïde du Fayoum [14], ainsi que le souligne Meyer [6]. Il diffère également de tous les hyracoïdes connus du Miocène inférieur et moyen d’Afrique orientale et australe, Afrohyrax championi, Meroehyrax bateae, Prohyrax tertiarius et Prohyrax hendeyi.
Par sa dentition, Brachyhyrax diffère de tous les titanohyracidés, saghatheriinés, pliohyracinés et procaviidés connus, et sa classification possible parmi les Geniohyidae repose principalement sur la morphologie brachyodonte des dents supérieures et brachysélénodonte des dents inférieures [11]. La découverte de spécimens plus complets est essentielle avant de conclure quant aux affinités du genre. Toutefois, les nouveaux spécimens révèlent nettement les affinités plus grandes de Brachyhyrax avec les Hyracoidea qu’avec n’importe quel autre groupe de mammifères.
Famille Titanohyracidae Matsumoto, 1926
Genre Afrohyrax nov.
Espèce type :Afrohyrax championi (Arambourg, 1933) [2]
Diagnose du genre : Titanohyracidés [5] de taille moyenne au toit crânien lisse, crêtes buccales du paracône et du métacône réduites à absentes ; paracône et métacône sans éperons linguaux, ectolophe assez redressé, mur buccal du métacône incliné à 60° sur l’axe de la rangée dentaire, métastyle faible et bas, parastyle et mésostyle forts, aux apex pincés et aux bases gonflées, hypocône beaucoup plus petit que le protocône, cingula buccal et lingual bien développés, prémolaires postérieures molarisées aux parastyle et mésostyle proéminents, crête antérieure (préhypocrista) de l’hypocône courte. Grande fosse faciale au-dessus des dents jugales antérieures, placée devant et au-dessus du foramen infra-orbitaire. Mandibule au foramen lingual proéminent sous les molaires postérieures, au moins chez certains individus (il s’agit peut-être d’un dimorphisme sexuel) et qui pénètre dans une chambre mandibulaire volumineuse. Tête de l’astragale non décalée par rapport à la trochlée.
Derivatio nominis :Afro pour l’Afrique, et hyrax, nom commun anglais des hyracoïdes actuels.
Diagnose de l’espèce : comme pour le genre.
Synonymie :Pliohyrax championi, Arambourg, 1933.
Megalohyrax championi (Arambourg), Whitworth, 1954, pp. 6–22, Pls. 1–4.
Megalohyrax sp. (cf M. pygmaeus Matsumoto), Whitworth, 1954, p. 23, Pl. 7, Fig. 2.
Pachyhyrax championi (Arambourg), Meyer, 1978, p. 301.
Description :Afrohyrax championi est le mieux représenté de tous les hyracoïdes du Miocène inférieur d’Afrique orientale, dont le crâne, les mandibules et quelques os postcrâniens ont été décrits par Whitworth [18], Meyer [6], Rasmussen et Simons [14], et Fischer [4]. Il n’est donc pas nécessaire de redécrire tout le matériel, mais plutôt de mettre en valeur les caractères qui révèlent son statut taxonomique et systématique.
Statut taxonomique d’Afrohyrax : Après comparaison avec le matériel du Fayoum, en Égypte, il apparaît que les fossiles kenyans attribués précédemment à Megalohyrax championi ou Pachyhyrax championi n’appartiennent pas à ces genres, contrairement à ce que pensaient Whitworth [18], Meyer [6], et Rasmussen et Simons [14].
Meyer [6] pensait que les mandibules provenant du Fayoum, en Égypte, et attribuées à Megalohyrax avaient été mal identifiées, et qu’elles auraient dû être placées dans le genre Pachyhyrax [15], dans lequel il a transféré les fossiles kenyans ; plus tard, néanmoins, ces derniers furent rapportés au genre Megalohyrax par Rasmussen et Simons [14]. Les variations d’attributions systématiques de l’espèce championi montrent que celle-ci ne se place pas aisément dans les genres oligocènes ou miocènes connus [13].
Dans leur classification de l’espèce championi, Whitworth [18] comme Meyer [6] semblent avoir été influencés par la présence d’un grand foramen conduisant à la chambre mandibulaire du côté lingual de la mandibule. Bien que cela soit un caractère important, c’est le seul (probablement lié au dimorphisme sexuel) partagé par Afrohyrax et Megalohyrax/Pachyhyrax parmi un grand nombre de traits, qui indique une forte divergence entre les genres paléogènes et ceux du Néogène d’Afrique orientale. La forme et la position du foramen et de la chambre mandibulaires suggèrent que les genres Megalohyrax, Pachyhyrax et Afrohyrax pourraient appartenir au même groupe supragénérique ; il faudra probablement ériger une nouvelle sous-famille de Titanohyracidae lorsque les données seront plus nombreuses.
Sous-ordre Procaviamorpha Whitworth, 1954
Famille Saghatheriidae Andrews, 1906
Genre Meroëhyrax Whitworth, 1954
Espèce Meroëhyrax bateae Whitworth, 1954
Synonymie :Meroehyrax bateae gen. et sp. nov. Whitworth, 1954, p. 41, Pl. 7, Fig. 1.
Meroehyrax bateae Whitworth, Meyer, 1978, p. 308.
Prohyrax sp. Meyer, 1978, p. 309, Fig. 14.10.
Meroehyrax bateae Whitworth, Rasmussen, 1989.
Diagnose émendée : Hyracoïdes de taille moyenne, à crâne court. Branche mandibulaire haute et convexe vers l’extérieur, convexité non causée par la grande fosse ovale à la face interne de la mandibule. Dents jugales inférieures brachyodontes, bunosélénodontes, en série continue au moins de la c/1 à la m/3. À la mandibule, la m/3 est la dent la plus longue, et montre un troisième lobe. Prémolaires postérieures molariformes. Molaires supérieures brachyodontes à l’ectolophe, mais un peu plus hautes que les cuspides linguales, pas d’éperon lingual au paracône et au métacône (en revanche, on observe des gonflements arrondis), préprotocrista aux bords acérés se terminant au milieu de la dent à la base linguale du paracône et derrière le cingulum mésial, métastyle petit mais accolé au cingulum distal qui atteint la base de l’hypocône, fermant ainsi distalement la vallée longitudinale. Protocône et hypocône comprimés au voisinage de leur apex. Parastyle et mésostyle pincés vers l’apex, et gonflés vers le collet. Vallée transversale bloquée lingualement par un pli cingulaire bas.
Matériel nouveau : Mor IIb 11′98, fragment de dent jugale supérieure; Mor II, 14′03, magnum; Mor II 4′04, troisième molaire supérieure droite peu usée; Mor II 5'04 fragments de mandibule gauche aux dents peu usées : p/4, m/1, la m/3 cassée et la m/3 droite brisée (Fig. 2, 1–5).
Discussion : Les quelques spécimens d’hyracoïdes de Moroto II sont intéressants, car ils offrent la première preuve de l’association de dentitions supérieure et inférieure d’une espèce rare, Meroehyrax bateae. Whitworth [18] a décrit une seule mandibule et une m/3 isolée, provenant de l’île de Rusinga, au Kenya, mais il a émis un doute sur les dents supérieures, qu’il a provisoirement incluses dans l’hypodigme. L’hypoconulide de la m/3 de Moroto est identique à celui de l’holotype (324′47) décrit par Whitworth [18] et diverge de l’hypoconulide plus sélénodonte qui caractérise la plupart des hyracoïdes, y compris Afrohyrax et Prohyrax. On peut donc définitivement rejeter l’hypothèse de Meyer [6], selon laquelle les genres Prohyrax et Meroehyrax sont synonymes. Le carpien de Moroto est plus petit que ceux d’Afrohyrax championi, l’hyracoïde commun des sites du Miocène inférieur d’Afrique orientale ; nous considérons qu’il peut être rapporté à Meroehyrax bateae. La molaire supérieure de Moroto est morphologiquement semblable à un spécimen de Loperot au Kenya figuré par Meyer [6] sous le nom de Prohyrax sp. Meyer a identifié les dents dans le maxillaire (n° 27–64) comme étant la première et la seconde molaires ; toutefois, la différence de taille relativement importante entre les dents indique qu’il s’agirait en fait de la P4/ et de la M1/. Si cela s’avérait juste, le spécimen appartiendrait à une espèce d’une taille proche de celle de M. bateae.
Les dents jugales supérieures provenant de Rusinga et mentionnées par Whitworth [18] comme des Meroëhyrax possibles ont été décrites comme des dents complètement molarisées, différant des molaires supérieures de Megalohyrax championi seulement par un mésostyle bas, un cingulum antérieur en forme de plaque et des crêtes transversales bien développées et similaires à celles observées chez Prohyrax tertiarius Stromer. Ces caractères isolent les dents kenyanes de la molaire supérieure de Moroto II, qui présente un mésostyle élevé, un cingulum antérieur étroit et des crêtes transversales faiblement développées. La détermination d’un des fossiles de Rusinga reste énigmatique, mais au moins un des spécimens (548′47, maintenant KNM RU 39) mentionné par Whitworth représente une dM4/ de chalicothère. L'un d’entre eux (381′48, maintenant KNM RU 55) appartient probablement à Megalohyrax championi. Le troisième spécimen (CMHy 98) pourrait avoir été perdu, puisqu’on n’en retrouve trace, ni au Natural History Museum de Londres, ni au National Museum du Kenya.
La molaire supérieure de Meroëhyrax diffère de celle d’un autre saghatheriiné, Thyrohyrax domorictus, qui présente des préprotocrista et préhypocrista mieux développées qui rejoignent l’éctolophe [6]. Elles diffèrent des espèces de Saghatherium qui possèdent un métastyle proéminent à la M3/, des préprotocrista et préhypocrista bien développées se terminant dans une petite cuspule, et des éperons du côté lingual des mésostyle et métastyle [6].
Affinités de la famille d’hyracoïdes actuels, les Procaviidae
On peut abandonner une relation proche entre les Procaviidae d’un côté et les Titanohyracidae [5] et Geniohyidae [1] de l’autre, car ces deux dernières possèdent une morphologie pseudhippomorphe de l’astragale et le premier un astragale de morphologie procaviamorphe [11]. Les Saghatheriidae et les Pliohyracidae apparaissent donc comme les plus proches parents des Procaviidae [11], qui représenteraient le groupe-frère des Pliohyracidae, mais la présence chez Meroëhyrax de molaires supérieures plus similaires à celles des procaviidés que de celles des pliohyracidés, éloignent les Procaviidae des Pliohyracidae, tout en les rapprochant des Saghatheriidae. À partir de la morphologie des molaires supérieures, on peut donc rejeter des relations de parentés proches entre les pliohyracidés et procaviidés, même si ces deux familles sont des procaviamorphes, comme l’indique la morphologie de l’astragale. Les Procaviidae présentent plus de caractères en commun avec Meroëhyrax qu’avec n’importe autre genre d’Hyracoidea. Par leur anatomie dentaire, ils apparaissent donc plus proches des Saghatheriidae que de n’importe quelle autre famille d’hyracoïdes. Des doutes subsisteront néanmoins, jusqu’à ce qu’on découvre un crâne de Meroëhyrax.
Conclusions
Jusqu’à récemment, les affinités des dents brachyodontes d’Hyracoïdes du Miocène inférieur d’Afrique orientale, attribuées à Bunohyrax sp., sont restées floues, principalement en raison du fait que très peu de spécimens ont été décrits. Avec la découverte de nouvelles pièces à Songhor au Kenya, et à Napak en Uganda, il est possible de confirmer leur attribution à un hyracoïde, et un nouveau genre est créé, à savoir Brachyhyrax. Les dents rapportées à ce dernier genre sont plus proches morphologiquement de celles des géniohyidés que de celles de n’importe quelle autre famille d’hyracoïdes ; le genre est donc provisoirement attribué à celle-ci.
L’hyracoïde le plus commun du Miocène inférieur d’Afrique orientale a eu une histoire taxonomique complexe : il a été attribué à trois genres différents (Pliohyrax, Megalohyrax, Pachyhyrax). Il diffère, par l’anatomie dentaire, de ces trois genres, il est aujourd’hui rapporté au genre Afrohyrax gen. nov., et présente des affinités avec la famille des Titanohyracidae.
Le genre mal connu Meroëhyrax est maintenant mieux représenté à l’état fossile, en particulier par la découverte de molaires supérieures et inférieures associées. Les molaires supérieures suggèrent que le genre n’est pas synonyme, comme on le pensait précédemment [6], de Prohyrax, qui possède des ectolophes fortement hypsodontes aux molaires supérieures, avec des para- et mésostyles gonflés. Les dents de Meroëhyrax sont plus proches morphologiquement de celles de Saghatherium (Saghatheriidae), tout en présentant des ressemblances avec celles des Procaviidae. Les premiers auraient donc pu être ancêtres des derniers. Les Pliohyracidae, auxquels appartient le genre Prohyrax, diffèrent des procaviidés par la morphologie de leurs dents, mais il apparaît plus probable aujourd’hui qu’ils ne représentent pas le groupe ancestral des damans modernes, comme cela avait été suggéré précédemment [3,12].
En résumé, on peut proposer la classification suivante des Hyracoïdes du Miocène inférieur d’Afrique orientale :
Ordre Hyracoidea Huxley, 1869
Sous-ordre Pseudhippomorpha Whitworth, 1954
Famille Geniohyidae, Andrews, 1906
Brachyhyrax aequatorialis nov. gen. nov. sp.
Famille Titanohyracidae Matsumoto, 1926
Afrohyrax championi (Arambourg, 1933)
Sous-ordre Procaviamorpha Whitworth, 1954
Famille Saghatheriidae Andrews, 1906
Meroehyrax bateae Whitworth, 1954
L’espèce procaviamorphe, Prohyrax tertiarius de Stromer [16,17], n’est connue que dans les dépôts du Miocène inférieur d’Afrique australe. Elle a été signalée auparavant en Afrique orientale, mais sur des fossiles qui appartiennent en fait à Meroëhyrax bateae. La famille des Pliohyracidae apparut en Afrique orientale à la fin du Miocène moyen (Parapliohyrax ngororaensis [10]), époque où les trois genres du Miocène inférieur d’Afrique orientale étaient éteints.
Introduction
In his pioneering study of East African hyracoids, Whitworth [18] recorded three genera (omitting the myohyracids which have been relocated in Macroscelidea [7]). The commonest and best-preserved material was attributed to Arambourg's [2] species Pliohyrax championi but was transferred to the genus Megalohyrax, which is well known from the Fayum, Egypt. Two of the species described by Whitworth [18], Meroehyrax bateae and Bunohyrax sp., were based on restricted samples, and as a result there has remained doubt about their affinities. For example, Meyer [6] thought that Prohyrax might be a senior synonym of Meroehyrax on the argument that the former was known only by upper dentitions, and the latter only by lowers. He also transferred the species championi to the genus Pachyhyrax, and was of the opinion that Whitworth's material of Bunohyrax may not even belong to Hyracoidea [13].
More complete samples of Prohyrax tertiarius from Namibia [11], including mandibular specimens, revealed that Meroehyrax and Prohyrax are different in morphology, even if they are about the same size. This conclusion is amplified by the description of exceptionally complete samples of a larger species of Prohyrax from Namibia (Prohyrax hendeyi) [9].
Recent collections from Early Miocene deposits in northeastern Uganda (Napak, Moroto II) contain additional specimens of Meroehyrax and Whitworth’s species of Bunohyrax. Even though the samples are still restricted, they are comprehensive enough to permit a reasonable reassessment of their taxonomic status and systematic position. In particular, the Uganda Palaeontology Expedition has sampled upper and lower teeth of both of these enigmatic taxa, removing doubt about which upper teeth belong to which lower ones. The discoveries also clarify the question of possible synonymy between Prohyrax and Meroehyrax, the two genera being markedly divergent, and indeed belonging to separate families of Hyracoidea.
This paper provides a revised taxonomy and systematic scheme for the Early Miocene hyracoids from East Africa.
Systematic descriptions
Order Hyracoidea Huxley, 1869
Suborder Pseudhippomorpha Whitworth, 1954
Family Geniohyidae Andrews, 1906
Genus Brachyhyrax nov.
Type species:Brachyhyrax aequatorialis sp. nov.
Diagnosis: Hyracoid in which the upper cheek teeth possess brachyodont buccal cusps, reduced parastyle located anterior to the paracone, mesostyle lower than the paracone-metacone ridge, weak metastyle, upper molars with square occlusal outline, no lingual spurs on paracone and metacone, protocone with preprotocrista and postprotocrista almost in line with each other, inflated mesoprotocrista, hypocone with well-developed prehypocrista and weaker posthypocrista, fold in lingual enamel between protocone and hypocone, longitudinal valley of upper molars almost straight and unencumbered by crista; upper premolars with antero-posteriorly short posterior lophs (hypocone and metacone reduced), lower cheek teeth with anterior loph considerably shorter than posterior loph, posterior loph lower than anterior one.
Derivatio nominis:Brachy signifies the brachyodont condition of the buccal cusps in the upper cheek teeth, hyrax is the common English word for extant hyracoids.
Species Brachyhyrax aequatorialis nov.
Synonymy:Bunohyrax sp. Whitworth, 1954, p. 25, Pl. 7, Fig. 3.
Bunohyrax sp. Meyer, 1978, p. 297.
Bunohyrax from East Africa, Rasmussen, 1989.
Diagnosis: as for genus.
Derivatio nominis:aequatorialis refers to the equatorial location of the know material of the species.
Holotype: M 21340, left upper molar, probably M2/ (field number Sgr 311′49, not Sgr 311′48 as reported in Whitworth, [18]) (Fig. 1,1).
Referred material: Sgr 924′47?, left lower premolar; Nap XVIII 4′85 left upper premolar; Nap I 102'02, left upper premolar; Nap IV 64, left m/3 lacking the hypoconulid; Nap IV 64 distal end of tibia; Nap V 84'02, second phalanx (Fig. 1,2–7).
Type locality: Songhor, Kenya.
Age: Early Miocene (ca 20–19 Ma).
Other localities: Napak I, Napak IV, Napak V, Napak XVIII (Uganda).
Description: The dental terminology is based on Rasmussen & Simons [14].
Upper dentition. The type specimen is a left upper molar, probably M2/ (Fig. 1,1). It is square in occlusal outline. The ectoloph undulates from mesial to distal, but is not markedly w-shaped as in titanohyracids and many other hyracoids. The parastyle is small and located on the mesio-buccal corner of the tooth in line with the paracone and metacone. The mesostyle is low, pinched at its apex and projects buccally. The apices of the paracone and metacone are appreciably higher than the mesostyle. The metastyle is small and in line with the paracone and metacone. The paracone and metacone have well-developed buccal 'ribs' to the extent that the cusps are almost conical in outline, as opposed to the usual condition in hyracoids where these cusps are more trenchant. The buccal surface of the metacone is angled with respect to the long axis of the tooth, and faces disto-buccally rather than buccally like the paracone. There are no signs of lingual spurs on either of the buccal cusps, the longitudinal valley being completely unencumbered from mesial to distal. This valley is only slightly undulating and it has no obvious fossettes, unlike titanohyracids, which do. The protocone has large pre- and postprotocrista which are almost in line with each other and angled at about 45° to the long axis of the tooth row. The preprotocrista extends to the mesial cingulum, which joins the base of the parastyle, closing off the longitudinal valley at its anterior end. The postprotocrista has an extra fold of enamel descending towards cervix and crossing the lingual end of the transverse valley. The protocone has a swollen central crista angled bucco-distally. There is a hint of a mesial cingulum and a small cingular eminence on the lingual aspect of the protocone, but not a clear cingulum. The hypocone has a long prehypocrista angled at about 60° to the long axis of the tooth row, but it does not cross the longitudinal valley. On its way mesially it shows a slight swelling. The posthypocrista departs from the apex of the hypocone directly distally and then curves buccally terminating at the base of the metastyle, thereby closing off the distal end of the longitudinal valley. The tooth has four subequal roots. The tooth is in light wear, with the protocone having slightly deeper wear than the paracone, and the hypocone slightly less than the metacone.
Nap I 102′02 is a left upper anterior premolar (P1/ or P2/) (Fig. 1,2a,2b). The anterior loph is like that of the molar described above, but the distal loph is reduced. The parastyle is positioned in line with the paracone and metacone. The parastyle is a weak swelling in the buccal surface of the paracone. The metacone is reduced in size, and in this specimen is heavily worn, all morphological details of the occlusal surface being eradicated, although the buccal surface is partly intact. The hypocone, and the root supporting it, is reduced. No morphological details of the distal loph can be given due to the heavy wear. The buccal enamel is wrinkled.
Nap XVIII 4′85 is a left upper posterior premolar (P3/ or P4/) (Fig. 1, 3a, 3b). The anterior loph is like that of the holotype molar save for its smaller dimensions. The parastyle is in line with the paracone and metacone, and the mesostyle is prominent and pinched in apically. The metastyle is small. The hypocone has a well-developed prehypocrista extending obliquely across the tooth towards the longitudinal valley and a curved posthypocrista that closes off the longitudinal valley distally. Lingually there is a large fold of enamel running from the base of the hypocone around the disto-lingual surface of the protocone. There is a fine mesial cingulum.
Lower dentition. Sgr 924′47? is a left lower premolar in medium wear (Fig. 1,4) from Songhor, Kenya. The anterior loph is much shorter mesiodistally than the rear loph. The protoconid has a paracristid that is obliquely oriented, terminating in a low paraconid, which has a cingular extension lingually, but separated from the anterior metaconid crest. The antero-buccal surface of the protoconid sports a cingulum. The trigonid basin is small and is almost closed off lingually where there is a narrow spout, which opens more anteriorly than lingually. The protocristid is transversely oriented and ends at the base of the metaconid. The metaconid has anterior and posterior cristids, which are large enough to give it a crescentoid aspect in occlusal view. The hypoconid has an extremely long cristid obliqua that extends to the base of the junction between the protocristid and the metaconid about 2/3 across the tooth. The cristid obliqua is slightly swollen in its middle. There is a wide sloping valley between the protoconid and hypoconid, which faces slightly posteriorly rather than directly buccally. At its base there is a cingular fold. The hypocristid is wide and runs slightly obliquely towards the base of the entoconid where it swells out distally as a small hypoconulid, which extends partly across the base of the distal surface of the entoconid. The talonid basin is large and opens lingually by way of a spout between the distal crest of the metaconid and the anterior crest of the entoconid.
Nap IV 64 is an unworn left m/3 lacking the hypoconulid (Fig. 1, 5a–c). In many respects, it resembles the premolar described above, but it is appreciably larger (Table 1). The trigonid basin opens anteriorly, as in the premolar and it is small. There is a narrow mesial cingulum, but none on the buccal side of the tooth. The hypoconid has a low ridge or rib on its mesio-lingual surface, which extends to the depths of the talonid basin separating off a small distal fovea from the talonid basin. The spout of the talonid basin is low down, near cervix. Judging from the broken distal surface of the tooth, the anterior part of the hypoconulid would have been about 2/3 the breadth of the tooth.
Post-cranial skeleton. There are two hyracoid post-cranial elements from Napak that are of the right dimensions to belong to Brachyhyrax aequatorialis. Nap IV 64 is a distal end of a tibia of a medium sized hyracoid measuring 11.5 mm dorso-plantar and 18.2 mm medio-laterally (Fig. 1,6). It has a prominent medial maleolar process next to a relatively small talar pulley facet, which suggests that the talus would have possessed a deep malleolar recess with no offset between the head and the pulley. If so then Brachyhyrax belongs to the Pseudhippomorpha in the sense of Pickford et al., [11] rather than to the Procaviamorpha. Nap V 84′02 is an axial second phalanx of a medium sized hyracoid (Fig. 1,7). It is a proximo-distally short, robust bone similar to those of other hyracoids.
Discussion: Whitworth [18] attributed two teeth (Sgr 311′48 (in fact the correct field number is Sgr 311′49), now M 21340, and R38′50, now KNM RU 295) to Bunohyrax sp. Meyer [6] criticised the generic attribution of these specimens, pointing out that they differed to such an extent from teeth of other species of Bunohyrax that he even questioned their attribution to Hyracoidea. He referred one specimen (KNM RU 343) to Anthracotheriidae but this tooth is in fact a deciduous left dM4/ of Kenyasus rusingensis[8]. Rasmussen [13] was in agreement with Meyer [6] that the Bunohyrax sp. from Kenya was probably not hyracoid. KNM RU 295 is not from a hyracoid – it is probably an artiodactyl upper molar, possibly deciduous. It possesses four main cusps and a paraconule, but no mesostyle or parastyle, and the protocone is not oriented in the same way as in hyracoids. M 21340, however, does belong to Hyracoidea, despite its peculiar morphology.
The new hypodigm comprises brachyodont upper cheek teeth and brachyselenodont lower ones. The only other hyracoids that even remotely resemble Brachyhyrax are Selenohyrax and Geniohyus from the Fayum, Egypt [14], and some teeth of an undetermined hyracoid from Oman [12]. Particular resemblances concern the shortened mesial lophids in the lower molars relative to the elongated distal lophids, and the presence of a slightly swollen lingual rib (mesohypocristid) on the hypoconid, which extends towards the base of the talonid basin. This structure is more complex in Selenohyrax than it is in Brachyhyrax and it may or may not be homologous to it. The upper dentition of Selenohyrax has not been described, so it is not possible to make comparisons.
Brachyhyrax is not close morphologically to any of the other Fayum hyracoids [14] as is evident from the criticisms by Meyer [6] of Whitworth’s [18] attribution of the fossils to Bunohyrax. It is also different from all known Early and Middle Miocene hyracoids from East and South Africa, including Afrohyrax championi, Meroehyrax bateae, Prohyrax tertiarius and Prohyrax hendeyi.
Dentally Brachyhyrax is divergent from all known titanohyracids, saghatheriines, pliohyracines, and procaviids, and its tentative classification in Geniohyidae is based mainly on the brachyodont (upper) and brachyselenodont (lower) morphology of the teeth [11]. The recovery of more complete specimens is required before its detailed affinities can be determined. However, the new specimens amply reveal its affinities with Hyracoidea as opposed to any other group of mammals.
Family Titanohyracidae Matsumoto, 1926
Genus Afrohyrax nov.
Type species:Afrohyrax championi (Arambourg, 1933) [2].
Synonymy:Pliohyrax championi, Arambourg, 1933.
Megalohyrax championi (Arambourg), Whitworth, 1954, pp. 6–22, Pls. 1–4.
Megalohyrax sp (cf M. pygmaeus Matsumoto), Whitworth, 1954, p. 23, Pl. 7, Fig. 2.
Pachyhyrax championi (Arambourg), Meyer, 1978, p. 301.
Generic diagnosis: Medium-sized titanohyracids with smooth skull roof; buccal ribs of the paracone and metacone reduced to absent; paracone and metacone lacking lingual spurs, ectoloph relatively upright, buccal wall of metacone oriented at ca 60° to the axis of the tooth row, metastyle weak and low, parastyle and mesostyle strong with pinched in apices and swollen bases, hypocone much smaller than protocone, well-developed buccal and lingual cingula, posterior premolars molarised with prominent parastyle and mesostyle, anterior crest (prehypocrista) of hypocone short. Large facial fossa above the anterior cheek teeth positioned anterior to and above the infra-orbital foramen. Mandible with prominent lingual foramen below the posterior molars (at least in some individuals: perhaps a sexually dimorphic character), which enters a voluminous mandibular chamber. Talus head not offset from trochlea.
Derivatio nominis:Afro for Africa, plus hyrax the common name of extant hyracoids.
Specific diagnosis: as for genus.
Description.Afrohyrax championi is the best represented of all the Early Miocene hyracoids from East Africa, with descriptions of skulls, mandibles and some postcranial bones provided by Whitworth [18], Meyer [6], Rasmussen and Simons [14], and Fischer [4]. It is therefore not necessary to redescribe all the material, but merely to highlight the features that reveal its taxonomic and systematic status.
Taxonomic status of Afrohyrax. Comparison of the Kenyan fossils previously attributed to Megalohyrax championi or Pachyhyrax championi with material from the Fayum, Egypt, reveal that they do not belong to either of these genera as thought by Whitworth [18], Meyer [6], and Rasmussen and Simons [14].
Meyer [6] argued that the Fayum, Egypt, mandibles attributed to Megalohyrax were wrongly classified, and should be identified as Pachyhyrax[15]. He transferred the Kenyan fossils to Pachyhyrax, but they were transferred back to Megalohyrax by Rasmussen & Simons [14]. Rasmussen [13] suggested that the ‘shuffling’ of the Kenyan species between various genera indicated that “M. championi does not comfortably fit any recognised Oligocene or Miocene genus.” There are significant dental differences between Megalohyrax from Kenya on the one hand and Pachyhyrax from the Fayum on the other, as was shown by Meyer [6], including the lack of lingual spurs on the protocone and metacone in the former, the more upright ectoloph, the relatively reduced hypocone and other features listed in the diagnosis above. In addition, the rear loph of the upper premolars of Megalohyrax eocaenus is reduced in mesio-distal length relative to the anterior loph, whereas in championi the premolars are more molarised.
In their classifications of the species championi, both Whitworth [18] and Meyer [6] appear to have been influenced by the presence of a large foramen leading into a mandibular chamber on the lingual side of the lower jaw. Whilst this is an important feature, it is only one character (probably sexually dimorphic) shared by the two genera, among many that reveal that the Palaeogene genera from Egypt and those from the Neogene of East Africa are quite divergent. The form and position of the mandibular foramen and chamber indicate that Megalohyrax, Pachyhyrax and Afrohyrax could belong to the same suprageneric grouping, and it may be necessary when more evidence is available, to erect a subfamily within Titanohyracidae.
Suborder Procaviamorpha Whitworth, 1954
Family Saghatheriidae Andrews, 1906
Genus Meroehyrax Whitworth, 1954
Species Meroehyrax bateae Whitworth, 1954
Synonymy: Meroehyrax bateae gen. et sp. nov. Whitworth, 1954, p. 41, Pl. 7, Fig. 1.
Meroehyrax bateae Whitworth, Meyer, 1978, p. 308.
Prohyrax sp. Meyer, 1978, p. 309, Fig. 14.10.
Meroehyrax bateae Whitworth, Rasmussen, 1989.
Emended diagnosis: medium-sized, short skulled hyracoids. Mandibular ramus deep and externally convex, convexity not caused by the large oval fossa on the inner surface of the mandible. Brachyodont, bunoselenodont lower cheek teeth, closed at least from c/1 to m/3. The m/3 is the longest tooth of the lower jaw, third lobe present. Posterior premolars molariform. Upper molars brachyodont with ectoloph slightly more hypsodont than lingual cusps, no lingual spurs on paracone and metacone (there are rounded swellings instead of spurs), preprotocrista sharp-edged, ending in midline of tooth at lingual base of paracone and behind the mesial cingulum, metastyle small but joined strongly to the distal cingulum which reaches across the tooth to the base of the hypocone, closing off the longitudinal valley distally. Protocone and hypocone compressed near their apices. Parastyle and mesostyle pinched apically, swelling towards cervix. Transverse valley blocked lingually by a low cingular fold.
New material: Mor IIb 11′98, upper cheek tooth fragment; Mor II, 14′03, magnum; Mor II 4′04, lightly worn right upper 3rd molar; Mor II 5′04 left mandible fragments with moderately worn p/4, m/1, broken m/3 and broken right m/3 (Fig. 2,1–5).
Description
The upper molar (Mor II 4′04) (Fig. 2,2) has four main cusps and a distal transverse crest and cingulum forming a low distal loph. The protocone is obliquely oriented, the anterior crest (preprotocrista) terminating in the centre line of the tooth just behind the anterior cingulum. The distal crest of the protocone (postprotocrista) is high and drops abruptly into the median transverse valley but does not block it, even at its base. The anterior surface of the protocone is concave. The base of the cusp is voluminous but it narrows sharply apically. The apex is blade-like in this unworn specimen. There is no lingual cingulum on the protocone but there is one in the lingual end of the median transverse valley. The paracone is selenodont with prominent parastyle and mesostyle. Both these styles are swollen at the base of the crown but pinch in apically. The buccal rib of the paracone is weakly expressed. The hypocone is conical with a sharp steep antero-buccal crest (prehypocrista) descending into the longitudinal valley terminating before reaching the median transverse valley. There is no trace of a cingulum on its lingual aspect. The ectoloph is almost straight with kinks where the styles are located. The metacone is selenodont with a prominent but low metastyle which is swollen basally and which bifurcates apically, one low crest blending into the distal crest of the metacone, the other reaching disto-lingually to form a small ‘fifth’ cusplet. The distal crest of this cusplet reaches lingually and blends into a distal cingulum that emanates from the disto-buccal corner of the hypocone. There is a low distal crest just anterior of the distal cingulum forming a small distal fossette. The enamel is finely wrinkled. There are three roots buccally and two lingually, meaning that this tooth is probably an M3/. Wear is minimal, being confined to outer cusps where it affects the apices of the paracone and metacone and their mesial and distal crests.
Mor II 11′98 is the distal part of an upper cheek tooth of a hyracoid (Fig. 2,1). It preserves part of the ectoloph and the hypocone together with the posterior fossette and is similar to the complete molar described immediately above. It too is likely to be an M3/ on account of the distal root pattern.
Mor II 5′04 (Fig. 2,3,4) is a fragmentary mandible with four teeth, broken into three main pieces. The lingual surface of the jaw below p/4-m/1 retains the upper edge of the lingual fossa, which forms a low antero-posterior ridge along the specimen.
The p/4 in Mor II 5′04 is in medium wear with about half the height of the crown worn off. It consists of two crescents, the anterior one shorter than the posterior one. The anterior crests of the crescents are oriented at about 45° to the long axis of the tooth, while the distal part of the crescent is almost at right angles to the long axis of the tooth row. There is a hint of a buccal cingulum in the end of the buccal notch, but it is low and insignificant. There is a light cingular fold on the antero-lingual corner of the tooth.
The m/1 is more deeply worn than the p/4, which is typical of hyracoids, and because of this most of the crown morphology has been obliterated. However it is possible to see that the anterior crescent is longer mesio-distally than the posterior crescent, the opposite of the situation in the p/4.
The left m/3 is at a lesser stage of wear than the p/4, again typical of hyracoids. It has lost about one third of the crown height due to wear and the hypoconulid is missing. The right m/3 retains the distal loph and the hypoconulid, so the total length of the m/3 can be estimated to be 14.6 mm. The anterior loph is broader than the second one, and the hypoconulid is short, low and narrow, being 3.9 mm wide compared to the anterior crescent, which is 7 mm wide. As in the p/4, the anterior crests of the crescents are oriented at about 45° to the long axis of the tooth row, whereas the distal crests are almost at right angles to the same axis. There is no buccal cingulum, and only a small anterior lingual one. The hypoconulid is almost bilaterally symmetrical in occlusal view, and is not markedly selenodont.
Mor II 14′03 is a small hyracoid magnum (Fig. 2,5), being C shaped in proximal and distal view with a prominent volar process and highly compressed proximo-distally. It measures 11.4 mm medio-lateral breadth, 10 mm dorso-volar height, and 4.4 mm proximo-distal length.
Discussion. The few hyracoid specimens from Moroto II are interesting as they provide the first evidence of an association between the upper and lower dentition of the rare species Meroëhyrax bateae. Whitworth [18] described a single mandible and an isolated m/3 from Rusinga Island, Kenya, but was doubtful about the upper teeth that he tentatively included in the hypodigm. The hypoconulid of the Moroto m/3 is identical to that in the holotype specimen (324′47) described by Whitworth [18] and is divergent from the more selenodont hypoconulid that typifies most hyracoids, including Afrohyrax and Prohyrax. We can thus definitively reject Meyer's [6] hypothesis that Prohyrax and Meroehyrax are synonyms. The cheek tooth and carpal from Moroto II are smaller than those of Afrohyrax championi, the common hyracoid of East African Early Miocene localities and we consider that they are also likely to represent Meroehyrax bateae. The upper molar from Moroto is morphologically similar to a specimen from Loperot, Kenya, figured by Meyer [6] as Prohyrax sp. Meyer identified the teeth in the maxilla (No. 27–64) as the first and second molars, but the relatively great size difference between the teeth suggests that they may in fact be the P4/ and M1/. If this is the case then the specimen represents a species close in size to M. bateae.
Three upper cheek teeth from Rusinga mentioned by Whitworth [18] as possibly representing Meroehyrax were described as being “completely molarised teeth, only differing from upper molars of Megalohyrax championi in the low mesostyle, the shelf-like anterior cingulum, and the well developed transverse crests, similar to those found in Prohyrax tertiarius Stromer.” This description suggests that the specimens differ from the Moroto II upper molar, which has a high mesostyle, a narrow anterior cingulum and poorly developed transverse crests. The determination of one of the Rusinga fossils remains enigmatic but one of the specimens (548′47, now KNM RU 39) mentioned by Whitworth, is a chalicothere dM4/. One of them (381′48, now KNM RU 55) is likely to belong to Megalohyrax championi. The third specimen (CMHy 98) may be lost, as no trace of it can be found in either the Natural History Museum, London, or the Kenya National Museum.
The upper molar of Meroehyrax differs from that of another saghatheriine, Thyrohyrax domorictus, which has more strongly developed preprotocrista and prehypocrista, which come in contact with the ectoloph [6]. They differ from Saghatherium species which have a prominent metastyle in the M3/, well developed preprotocrista and prehypocrista each of which terminates in a small cuspule, and spurs on the lingual side of the mesostyle and metastyle [6].
Affinities of the extant hyracoid family Procaviidae
We can rule out any close relationship between Procaviidae, on the one hand, and Titanohyracidae [5] and Geniohyidae [1], on the other, because the former has a procaviamorph talar morphology and both of the latter families possess the pseudhippomorph talar morphology [11]. This leaves Saghatheriidae and Pliohyracidae as the contendors for the closest relatives of the Procaviidae as all three families have the offset, procaviamorph talus. Pickford et al., [11] placed Procaviidae as the sister group of Pliohyracidae, but the discovery that Meroehyrax has upper molars that are more similar to those of procaviids than are those of pliohyracids, shifts the relationship away from the pliohyracids, and back towards the Saghatheriidae. On the basis of upper molar morphology, we can rule out any particularly close relationship between pliohyracids and procaviids, the latter family having more in common with Meroehyrax than with any other genus of Hyracoidea. This means that Procaviidae are probably more closely related to Saghatheriidae than to any other family of hyracoids. Some doubts will remain, however, until a skull of Meroehyrax is found.
Conclusions
Until recently, the affinities of brachyodont hyracoid teeth from the Early Miocene of East Africa hitherto attributed to Bunohyrax sp., have remained unsettled, mainly because few specimens were described. Now that some additional fossils have been recovered from Songhor, Kenya, and Napak, Uganda, it is possible to confirm that they do indeed represent a hyracoid for which the new genus Brachyhyrax is created. The teeth of this genus are closest in overall morphology to those of geniohyids, rather than to those of any other group of hyracoids, and it is provisionally attributed to this family.
The commonest East African Early Miocene hyracoid has had a checkered taxonomic history, having been attributed to three different genera (Pliohyrax, Megalohyrax, Pachyhyrax). It is now assigned its own genus, Afrohyrax, on account of dental differences from all three of the genera in which is was previously classified. Its familial affinities lie with Titanohyracidae.
The hitherto poorly known genus Meroehyrax is now better represented by fossils including the first known upper molars associated with lowers. The upper teeth reveal that Meroehyrax is not synonymous with Prohyrax as once thought [6], which has extremely hypsodont curved ectolophs in the upper molars, with swollen para- and mesostyles [9] and [11]. Meroehyrax is closest in dental morphology to Saghatherium (Saghatheriidae), but some resemblances to Procaviidae suggest that it may be ancestral to this group. Pliohyracidae, to which the genus Prohyrax belongs, are dentally divergent from procaviids, and it now appears likely that they are not ancestral to the extant hyraxes, as previously thought [3] and [9].
In summary, the Early Miocene Hyracoidea of East Africa are classified as follows:
Order Hyracoidea Huxley, 1869
Suborder Pseudhippomorpha Whitworth, 1954
Family Geniohyidae, Andrews, 1906
Brachyhyrax aequatorialis nov. gen. nov. sp.
Family Titanohyracidae Matsumoto, 1926
Afrohyrax championi (Arambourg, 1933)
Suborder Procaviamorpha Whitworth, 1954
Family Saghatheriidae Andrews, 1906
Meroëhyrax bateae Whitworth, 1954
The procaviamorph species Prohyrax tertiarius of Stromer [16] and [17] is known only from southern African Early Miocene deposits, previous records of it in East Africa [6] being based on specimens of Meroehyrax bateae. The family Pliohyracidae, to which Prohyrax belongs, makes its earliest appearance in East Africa in Late Middle Miocene times [11] in the form of Parapliohyrax ngororaensis[10] by which time all three of the East African Early Miocene hyracoids had gone extinct.
Acknowledgements
The Uganda Palaeontology Expedition is a collaborative project between the ‘Muséum national d’histoire naturelle’, Paris, France, and the Uganda Museum, Kampala. We thank the Uganda National Council for Science and Technology (Drs Nyiira, Kakule, Mugoya), the Uganda Museum (Dr E. Kamuhangire, Mr E. Musiime), Makerere University Geology Department (Mrs I. Ssemmanda), and the Ministry of Culture, Antiquities and Tourism (Dr S. Kagoda) for authorisation to carry out research and for cooperation within Uganda. The French Embassy in Kampala was of considerable aid to the Uganda Palaeontology Expedition. I particularly thank the District Administrator and Municipal Council of Moroto for help and encouragement to continue surveying in the region. Drs Brigitte Senut, Dominique Gommery and Mr Ezra Musiime assisted in the fieldwork at Moroto and Napak, during which the new fossils were found.
The Kenya Palaeontology Expedition is a collaborative project with the Community Museums of Kenya (Director: Mr E. Gitonga). Research authorisation was granted by the Kenyan Ministry of Education, Science, and Technology. I thank our field team in Kenya led by Mr K. Cheboi, and Dr B. Senut, co-director of the KPE, and translator of the abridged French version of this paper.
I am anxious to thank Professors Y. Coppens (Collège de France) and P. Taquet (Département Histoire de la Terre) for funds and other assistance. Funding was also supplied by the French Ministry of Foreign Affairs (‘Commission des fouilles’) and the CNRS (UMR 5143, and Projet PICS). Finally, I would like to acknowledge the assistance provided by Dr Jerry Hooker and Mr Andy Currant (Natural History Museum, London).
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Brachyhyrax aequatorialis gen. et sp. nov. from the Early Miocene of East Africa. (scale: 10 mm). 1. M 21340, left upper molar (probably M2/) from Songhor, Kenya, stereo occlusal view. 2. Nap XVIII 4'85, left upper posterior premolar (P3/ or P4/) from Napak, Uganda: (a) occlusal view (mesial to top of page) and (b) stereo occlusal view (mesial to the left). 3. Nap I 102'02, left upper anterior premolar (P1/ or P2/) from Napak, Uganda: (a) buccal view, (b) stereo occlusal view. 4. Sgr 924'47?, left lower premolar from Songhor, Kenya, stereo occlusal view. 5. Nap IV 64, left m/3 lacking the hypoconulid from Napak, Uganda: (a) lingual, (b) occlusal, (c) buccal view. 6. Nap IV 64, distal end of tibia from Napak, Uganda, distal view. 7. Nap V 84'02, axial second phalanx, from Napak, Uganda, dorsal view.
Brachyhyrax aequatorialis gen. et sp. nov. du Miocène inférieur d’Afrique orientale (échelle : 10 mm). 1. M 21340, molaire supérieure gauche (probablement une M2/) provenant de Songhor au Kenya, vue occlusale stéréoscopique. 2. Nap XVIII 4'85, prémolaire postérieure supérieure gauche (P3/ ou P4/) provenant de Napak, en Ouganda : (a) vue occlusale (partie mésiale vers le haut), (b) vue occlusale stéréoscopique (partie mésiale à gauche). 3. Nap I 102'02, prémolaire antérieure gauche supérieure (P1/ ou P2/) provenant de Napak, en Ouganda : (a) vue buccale, (b) vue occlusale stéréoscopique. 4. Sgr 924'47?, prémolaire inférieure gauche provenant de Songhor au Kenya, vue occlusale stéréoscopique. 5. Nap IV 64, m/3 gauche sans l’hypoconulide provenant de Napak, Ouganda : (a) vue linguale, (b) vue occlusale, (c) vue buccale. 6. Nap IV 64, extrémité distale de tibia provenant de Napak, en Ouganda, vue distale. 7. Nap V 84'02, deuxième phalange axiale provenant de Napak en Ouganda, vue dorsale.
Meroehyrax bateae from Moroto II, Early Miocene, Uganda (scale: 10 mm). 1. Mor II, 11′98, distal portion of upper molar: (a) occlusal, (b) distal view. 2. Mor II, 4′04, right M3/: (a) stereo occlusal view, (b) buccal, (c) lingual, and (d) mesial views. 3. Mor II, 5′04, left mandible with p/4-m/1: (a) buccal, (b) occlusal, and (c) lingual views. 4. Mor II, 5′04, left mandible with m/3 (lacking hypoconulid): (a) buccal, (b) occlusal, and (c) lingual views. 5. Mor II, 14′03, magnum: (a) proximal, (b) posterior, and (c) distal views.
Meroehyrax bateae de Moroto II, Miocène inférieur d’Ouganda (échelle : 10 mm). 1. Mor II, 11′98, partie distale de molaire supérieure : (a) vue occlusal, (b) vue distale. 2. Mor II, 4′04, M3/ droite, (a) vue occlusale stéréoscopique, (b) vue buccale, (c) vue linguale, (d) vue mésiale. 3. Mor II, 5′04, mandibule gauche avec p/4-m/1 : (a) vue buccale, (b) vue occlusale, (c) vue linguale. 4. Mor II, 5′04, mandibule gauche avec m/3 (sans hypoconulide), (a) vue buccale, (b) vue occlusale, (c) vue linguale. 5. Mor II, 14′03, magnum : (a) vue proximale, (b) vue postérieure, (c) vue distale.
Measurements (in mm) of the dental remains of Brachyhyrax aequatorialis gen. et sp. nov
Tableau 1
Mesures (en mm) des restes dentaires de Brachyhyrax aequatorialis gen. et sp. nov.
SpecimenToothMesio-distal lengthBreadth 1st lophBreadth 2nd lophM 21340left M2/?17.616.116.0Nap XVIII 4'85left upper premolar12.313.312.3Nap I 102'02left upper premolar11.112.611.3Sgr 924'47?left lower premolar13.310.19.7Nap IV 64left m/3 lacking hypoconulid24a13.912.4
Specimen is incomplete: the first two lophs measure 17 mm, the original total length would have been about 24 mm.