Palaeont. afr., 36,119-138(2000) THE NEOGENE RHINOCEROSES OF NAMIBIA by Claude Guerin ERS 2042 - Centre de Paleontologie Stratigraphique et Paleoecologie, Universite Claude Bernard -Lyon I, U.F.R. des Sciences de la terre, 27-43 boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France. ABSTRACT: Since 1991 the Namibia Palaeontology Expedition has excavated four Miocene sites in the Sperrgebiet, three of which (Arrisdrift, Fiskus and Auchas Mine) are new. Only the material from Arrisdrift and a single bone from Langental are specifically determinable. All but one of the 81 rhinocerotid fossils from Arrisdrift constitute a homogeneous sample pertaining to a very large species of cursorial rhino. The exception is an isolated magnum which suggests a small to medium-sized short legged form, perhaps Chilotheridium pattersoni. A magnum from Langental probably represents Brachypotherium heinzelini. The large form from Arrisdrift seems to be the largest of the Miocene African Rhinos; the size and proportions of the metapodials and the other limb bones suggest an analogy with Diceros gr. pachygnathus-neumayri of the Upper Miocene of the Near East; the type of construction of the upper cheek teeth, namely die fourth premolar, is of Dicerotine type and presents, as do the dimensions, close resemblances with Diceros douariensis of the Upper Miocene of North Africa and Italy; the mandible shows analogies with the Dicerotines, especially the apparently short symphysis. This Rhino is Diceros australis nov. sp., so far the oldest known species of the subfamily. KEYWORDS: Neogene, Namibia, Sperrgebiet, Arrisdrift, Perissodactyla, Rhinocerotidae, Diceros australis sp. nov. INTRODUCTION Since 1991 the Namibia Paleontology Expedition, led by B. Senut and M. Pickford, has excavated Miocene sites in the Sperrgebiet (Pickford et al. 1995). Rhinos were found at four sites, one of them, Arrisdrift, being very important. I had the good luck to find among about 85 fossils three specimens of the same carpal bone, the magnum, showing that three different species are present, one at Langental and two at Arrisdrift (Figure 1: 3-5; Figure 2). The bulk of the Arrisdrift material (80 pieces) belongs to a new species, Diceros australis. D. australis is the oldest species of the Dicerotine sub­ family, whose present day representatives are the black and the white rhinos of Africa. Previously, some mammalian remains were recovered from South West Africa and sent to Germany, where they were studied by E. Stromer (1926); the only published fossil rhino was assigned to “Rhinocerine g. et sp. indet” . Several papers were later published reassessing some mammalian species and describing others. Hamilton & Van Couvering (1977) synthesized the preceding works and brought the faunal list up to date. In that list the only identified rhinocerotid was Brachypotherium heinzelini, based on a report by K. Heissig (1971) on the half-mandible found at Langental and described without determination by E. Stromer. Among the undescribed rhino fossils from Namibia found prior to the work of the Namibia Palaeontology Expedition, there is a weathered but complete metatarsal III from a large Brachypotherium housed in the Figure 1. 1: right calcaneum (AD 50’97) of Diceros australis nov. sp.; 2: left astragalus (AD 619’94) of Diceros australis nov. sp.; 3-5: the three magnums of the Miocene rhinoceroses from Namibia: 3: cf. Chilotheridium pattersoni (AD 618’97), 4: Diceros australis nov. sp. (AD 63 8 ’97); both from Arrisdrift, 5: Brachypotherium heinzelini from Langental (LT 384’96). Scale bar is 3 cm. 120 collections of the South African Museum (SAM PQ recognized by Heissig in 1971 on the basis of half a 2517) and recovered 8 km southeast of Bogenfels mandible found at the same site. (probably the sites of Glastal 1 or 2) by J. Schneider in 1983. Fiskus Finally some Quaternary rhino remains also are known A deeply worn upper premolar was found in Fiskus, from Namibia: an M 3/ of Ceratotherium (South African with an age of about 20 Ma. Museum SAM PQ 2126) was found in 1978 by G. Corvinus in the “brown grits in the Upper Grillental”. A Auchas Mine skull, a mandible and some rhinoceros tracks attributed Auchas Mine is an alluvial diamond-bearing deposit to D iceros bicornis were recovered near 50 km upstream from Oranjemund (Pickford et al. Kolmannskuppe (= Kolmanskop) and Charlottenthal 1995), about 19 to 20 Ma old. Among seven mammalian and briefly described by R. Heinz (1933) and reviewed species found in pit AM 02 is an undetermined rhinoceros by C. Guerin & G. Demathieu (1993). of which two specimens were recovered: an atlas vertebra and a mandible fragment. THE SITES Four lower or middle Miocene rhino sites were worked MIOCENE RHINOS OF AFRICA by the Namibia Paleontology Expedition in the Six rhino lineages (comprising a total of seven genera Sperrgebiet, three of which are new : Arrisdrift, Fiskus and eleven species) are so far known from the African and Auchas Mine. Miocene (Hooijer 1973, 1978; Guerin 1980 b, 1989; Prothero et al. 1989). The ages of numerous African Arrisdrift sites are based on the results of M. Pickford (pers. This very rich site, near the Orange River, 35 km east comm.), of Oranj emund, is about 17 Ma old and yielded numerous vertebrate remains (Pickford et al. 1996). All but one of Aceratheres the 81 fossil rhino specimens from Arrisdrift constitute Aceratheres are medium to large-sized, hornless, a homogeneous sample pertaining to a very large species tapir-like cursorial rhinos with four toes in the forelimb, of cursorial rhino, Diceros australis. The exception is They possess strong lower tusks, and their cheek-teeth an isolated magnum which is totally different from the are very brachyodont with the upper ones possessing an magnum assigned to D. australis: it is shallow and very outer wall which is more or less flat. They are recorded wide and suggests a small to medium sized short-legged from East and North Africa: form, perhaps Chilotheridium pattersoni, which was Aceratherium acutirostratum (Deraniyagala 1951) defined at Loperot, Kenya, the age of which is about the is medium-sized: It is known from the Alengerr Beds (14 same as that of Arrisdrift. to 12 Ma), Chemeron Formation-Northern Extension (5 to 4.5 Ma), Karungu (18 Ma), Moruaret Hill near Langental Losidok (ca 16 Ma), Ngorora Formation (11 to 12 Ma), In this 18 to 19 Ma old site one rhino specimen, a Ombo (15 Ma), and Rusinga (18 Ma) in Kenya; Napak complete magnum, was recovered. This fossil probably (19.5 Ma) in Uganda; Karugamania (older than 7 Ma) represents Brachypotherium heinzelini which was and Sinda (more than 6 Ma) in Congo. 80 T ♦ A □ O 40 + o 30 - 20 - - ■ D. bicornis G Langental ♦ A rrisd rift large O A rrisdrify small * Aceratheres 10 - A schleiermacheri • pachygnathus O Brachypothere 0 4-----------------------------b------------------------- 1----------------------------1----------------------------1--------------------------- 1------------------------------1 30 35 40 45 50 55 60 F igure 2: Scatter diagram of the anterior width (Y axis) versus the sus-articular height (X axis) of the three magums of Miocene rhinoceroses from Namibia, other Miocene rhinoceroses and the present day Diceros bicornis. 70 60 I ■ 50 ▲ A r Aceratherium campbelliHamilton 1973 is very large: it is recorded from Jebel Zelten (ca 16 to 17 Ma) in Libya. Dicerorhines Dicerorhines are two-homed medium- to large-sized cursorial rhinos with well developed lower tusks; the upper cheek teeth are relatively brachyodont with an outer wall presenting (especially in the two last premolars) two powerful vertical folds (paracone and metacone folds). They possess long faces. It is known from East Africa: Dicerorhinus leakeyi Hooijer 1966 is medium-sized: it has been recorded from the Alengerr Beds (14 to 12 Ma), Chemeron Northern Extension (ca 5 Ma), Karungu (18 Ma), Maboko (15.5 Ma), Ombo (15 Ma), Rusinga (18 Ma) in Kenya and Napak (19.5 Ma) in Uganda. Note that in most of these sites D. leakeyi is sympatric with Aceratherium acutirostratum. An Upper Miocene Algerian species, Dicerorhinus primaevus Arambourg 1959, has a controversial generic status (Geraads 1986). Large species of Dicerorhinus are so far unknown in the African Miocene but are present in Europe with D. schleiermacheri and others (Guerin 1980). Dicerotines This subfamily includes the two extant African rhinos Diceros bicornis ("black" rhino) and Ceratotherium simum ("white" rhino). Ceratotherium is much more evolved and dates from the Uppermost Miocene. Species of the less specialized genus Diceros, which appears during the Middle Miocene, are large and heavily-built two-homed rhinos. The face is short; they possess short mandibular symphysis and there are no incisors. The outer wall of the brachyodont upper cheek teeth possesses only one marked vertical fold, the paracone. Miocene forms are known from Northern Africa, Southern Spain, Italy and the Near East (Guerin 1980): Diceros douariensis Guerin, 1966: This species has been reported from Douaria (9.5 Ma), and possibly Djebel Krechem el Artsouma (Upper Miocene) in Tunisia (Geraads 1989), and Baccinello V3 (zone MN 13) in Italy (Guerin 1980). Material from Gravitelli (Upper Miocene) in Sicily (Italy), Cenes de la Vega and Los Homillos (both MN 13) in the Granada Basin (Spain) clearly represents Diceros but is not sufficient for a determination at the specific level. The two Near-East Upper Miocene Diceros species, whose discrimination and affinities are somewhat controversial, are D. pachygnathus from Pikermi (Greece) and D. neumayri from Turkey. All these species of Diceros are much younger than the Arrisdrift fauna. Paradiceros mukirii Hooijer 1968 is a small rhino of the Dicerotine group known from Fort Teman (about 13 Ma) and perhaps Maralal in Kenya, Kisegi (13 to 14 Ma) in Uganda, and Beni Mellal (12.5 Ma) in Morocco (Hooijer 1968; Guerin 1994). 121 Iranotheres Iranotheres are very large and heavily built rhinos from Eurasia with (for the time) extremely hypsodont cheek-teeth whose folded enamel is characteristic. Only one species has so far been found in Africa, and it is poorly known (Aguirre & Guerin 1974): Kenyatherium bishopi Aguirre & Guerin 1974 is recorded from Nakali (9.5 Ma) and Sambum Hills in Kenya (9.5 Ma) (Nakaya et al. 1999). Brachypotheres Brachypotheres are large hippopotamus-like hornless rhinos with very shortened but powerful legs. The outer wall of the upper cheek teeth show a trend to flattening. The tusks are large. The way of life was hippopotamus­ like. As noted by M. Pickford et al. (1993, p. 109) the African species need revision. They are known from North, East and South Africa: Brachypotherium snowi (Fourtau 1920) is known from Wadi Moghara, Egypt and Jebel Zelten (17 to 16 Ma) in Libya. Brachypotherium heinzelini Hooijer, 1963 is reported from Arongo Uyoma (Early Miocene), Chemeron Formation-Northern Extension (5 to 4.5 Ma), Kamngu (18 Ma) and Rusinga (18 Ma) in Kenya; Bukwa (between 17.5 and 18.5 Ma) and Napak (19.5 Ma) in Uganda; Karugamania (older than 7 Ma) and Sinda (more than 6 Ma) in Congo and Langental (18 Ma) in Namibia. Brachypotherium lewisi Hooijer & Patterson, 1972 is recorded from Kanapoi (4.5 Ma), Lothagam (7 Ma), Mpesida (6.5 Ma), Ngorora (12 to 11 Ma) in Kenya and Sahabi (6.5 Ma) in Libya. Chilotheres Although pertaining to a different subfamily Chilotheridium presents many convergences with the preceding group. It is a small short-legged rhino with small tusks, but there is one small horn in both sexes, and the manus is four-toed. The cheek teeth are hypsodont. It is known from East Africa (Hooijer 1971). Chilotheridium pattersoni Hooijer 1971 is present at Kirimum (15 Ma), Loperot (17 Ma), Ngorora (12 to 11 Ma), Ombo (16 Ma) and Rusinga (18 Ma) in Kenya; and Bukwa (ca 18 Ma) in Uganda. Reference material I had the opportunity to study a great number of specimens of Miocene rhinos from Africa, particularly material preserved in the Natural History Museum, London. I had the possibility to study all the known material of Chilotheridium pattersoni from Loperot when it was in Holland. The holotype of Diceros douariensis is in Lyon, and the material from Baccinello V3 is preserved in Basle, Switzerland. Among the material in London there are different pieces from the three African species of Brachypotherium, good casts of skulls and teeth of Paradiceros mukirii, some specimens of Aceratherium campbelli, skulls and mandibles o f Aceratherium acutirostratum and Dicerorhinus leakeyi. 122 Unfortunately, in the original description of Dicerorhinus leakeyi, D.A. Hooijer (1966,1973) wrote that it is impossible to distinguish the postcranial material of that species from Aceratherium acutirostratum. Consequently postcranial bones of the two species are not separated in the London collections, and they are not numerous enough to enable distinction. But, although I have not seen it, I am convinced that such a distinction will be possible on the original material housed in the National Museums ofKenya inNairobi. In the following tables the undifferenciated D. leakeyi/A. acutirostrartum material is named MSUR. To cover up the absence of references forthepostcranials of medium­ sized African Aceratherium, I thus use a mixture of m easurem ents taken on the European species Aceratherium tetradactylum (Middle Miocene) and A. incisivum (Upper Miocene), which pertain to the same lineage, for comparison; in the tables the mixture is labelled Aceratheres. Because large species of Dicerorhinus are so far unknown in the Miocene of Africa, I utilise Dicerorhinus schleiermacheri from the Upper Miocene of Europe for comparisons. Finally, to have a sample of large Miocene Diceros, I used the material from Pikermi (widely scattered in all the Natural History Museums of Europe) which is D. pachygnathus, and the material from Turkey which is housed in the Museum of Munich, Germany; the last one belongs to Diceros neumayri. In order to avoid the problems of disorder in the nomenclatural designation of D. pachygnathus, and of the differentiation between D. pachygnathus and D. neumayri (in my opinion close to but somewhat distinct from each other) I will refer to the regrouped m aterial by the name D iceros gr. pachygnathus-neumayri. THE LARGE RHINOCEROS FROM ARRISDRIFT, Diceros australis sp. nov Material 2 large and 5 small fragments of mandibles with more or less important elements of their respective tooth- rows; 2 lower incisors; 10 isolated upper cheek-teeeth; 13 isolated lower cheek-teeth; 1 radius; 3 ulnae (including 1 complete); 6 carpals (2 magnums, 2 pyramidals, 1 semilunar, 1 pisiform); 4 metacarpals (1 Me II, 2 Me III, 1 Me IV); 1 tibia; TABLE 1. Compared dimensions of the mandible of Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam== diameter; dist= distal; horiz= horizontal; prox:= proximal; tr= transverse. ARRISDRIFT Diceros douariensis n° AD 556'94 AD 300'97 AD313'98 AD437'97 AD 223'97 AD478'95 n mean min. max. symmetry R L R R R Distance symphysis-heel 462 1 396 Depth horiz. ramus P2-P3 67 67.5 1 82.00 Depth horiz. ramus P3-P4 80 77 2 84.50 80 89 Depth horiz. ramus P4-M1 87.5 81 2 96.50 95 98 Depth horiz. ramus M l-M2 93.5 93 2 108.00 106 110 Depth horiz. ramus M2-M3 99 102.5 108 1 1 0 0 .0 0 Depth horiz. ramus M3 107 105 1 107.00 Width horiz. ramus P4-M1 60 about 43,5 2 49.75 49.5 50 Width horiz. ramus M3 67 60.5 50 2 57.50 57 58 AP diam. ascending ramus 167 Transv. diam. condyle 125.5 Chilotheridium pattersoni P. mukirii B. heinzelini MSUR n mean min. max. Fort Teman Langental Karungu Distance symphysis-heel 2 423.00 404 442 Depth horiz. ramus P2-P3 1 92.00 59.5 60 Depth horiz. ramus P3-P4 3 84.50 71 98 64 59 Depth horiz. ramus P4-M1 3 89.00 77 99 70 64 Depth horiz. ramus M l-M2 3 91.67 77 104 82.5 6 6 Depth horiz. ramus M2-M3 3 91.67 85 103 88.5 est. 82 70 Depth horiz. ramus M3 2 101.75 101.5 102 92 78 Width horiz. ramus P4-M1 45 37 Width horiz. ramus M3 47 ’> 54 41.5 AP diam. ascending ramus Transv. diam. condyle 98 123 0 Figure 3: Teeth of Diceros australis nov. sp. 1: lower tusk AD 87’98 (photo V. Eisenmann); 2: Left D 4/ AD 292’94; 3: Right P 4/ AD 578’98; 4: Right M 3/ PQ AD 339; 5 and 8 : Left D /3 PQ AD 635 (respectively labial and lingual view); 6 and 9: Left P /2 AD 86’98 (respectively labial and lingual view); 7 and 10: Left M /3 AD 200’98 (respectively labial and lingual view). Scale bar is 1 cm for the tusk and 3 cm for the cheek-teeth. I patella; II tarsals ( 3 tali, 4 calcanea, 1 cuboid, 2 naviculars, 1 first cuneiform); 9 metatarsals (4 Mt II including 2 complete, 4 complete or subcomplete Mt III, 1 complete Mt IV); 9 phalanges; 3 sesamoids. Systematic Palaeontology All but one of the 81 fossil rhino specimens from Arrisdrift constitute a homogeneous sample pertaining to a very large species of cursorial rhino. The large rhino from Arrisdrift can be characterized as follows: • with the possible exception of Kenyatherium, whose teeth are totally different, it is the largest of the known African Miocene rhinos; • size and proportions of the metapodials and the other limb bones suggest an analogy especially with the Diceros gr. pachygnathus-neumayri of the Upper Miocene ofthe Near East, and to a lesser extent with Dicerorhinus schleiermacheri from the Upper Miocene of Europe; • the type of construction of the upper cheek teeth, especially the fourth premolar, is of Dicerotine type and presents strong resemblances to Diceros douariensis of the Upper Miocene of North Africa and Italy; • the mandible shows analogies with the Dicerotines, especially the apparently short symphysis. • the small reduced lower tusk could represent an evolutionary stage prior to the loss of the entire anterior dentition. Thus this rhino is a large new species of Dicerotine, which I name Diceros australis nov. sp.; it is so far the oldest known species of the sub-family. Its definition is as follows: PALAEONTOLOGIA AFRICANA VOLUME 36-2000 124 ARRISDRIFT AD 292'94 AD 578'98 AD 649'97 AD 228'97 AD 285'95 PQ AD 339 PQ AD 2697 PQ AD 2661 PD AD 1103 TABLE 2. Compared dimensions of the upper cheek teeth of Diceros australis nov. sp ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. D 4/ ap tr M 1/ ap tr M 2/ ap tr 47 47 59 56.5 58 62.5 M 3/ absolute length 64.5 65.5 66.5 65.5 anat. length 55 53 52 54 tr 62 62 61 60 P 4/ ap 43.5 37.5 tr 60.5 54 D. douariensis B. snowi n mean min. max. n mean min. max. D 4/ ap 1 44.00 0 tr 1 49.00 0 M 1/ ap 2 60.25 59 61.5 2 61.50 55 68 tr 3 61.33 59 64 1 71.00 M 2/ ap 3 62.83 60 67.5 2 67.00 63 71 tr 2 68.75 66.5 71 2 76.50 74 79 M 3/ absolute length 1 63.00 0 anat. length 3 57.33 50 64 1 63.00 tr 3 61.17 59 64 0 P 4/ ap 2 40.50 37.5 43.5 1 49 tr 2 57.25 54 60.5 1 69 Paradiceros mukirii Fort Teman D 4/ M 1/ M 2/ M 3/ P 4/ ap tr ap tr ap tr absolute length anat. length tr ap tr 31.5 45 Dicerorh. leakeyi Rusinga 40 50 48 56 53 43 56.5 Diagnosis: a very large cursorial rhinoceros of the Dicerotine type. Upper cheek teeth brachyodont, with a more or less continuous crenellated inner cingulum, and a crochet as the only or main internal fold. Ectoloph of the upper premolars with a strong parastyle, paracone fold thick but not very prominent and no mesostyle nor metacone fold. Upper molars possess on their ectoloph a large paracone fold and a weak vertical bulge in the middle of it, and a protocone weakly constricted on its anterior face. Tall and slim but sturdy limb bones. Lateral and medial metapodials very long with respect to the central one. Locus typicus and Stratum typicum: Arrisdrift, Sperrgebiet, SouthemNamibia; Lower Middle Miocene, about 17 Ma. Derivatio nominis: from «austral» = southern; D. australis is the most southern Tertiary Diceros ever found. Holotype: Left third metacarpal AD 52’97 (Figure 5: 3 and 4). A. campbelli 58 68.5 54 47.5 49.5 48 63 Ascribed material: Left half mandible AD 300’97; right upper fourth premolar AD 578’98 (Figure 3: 3); left upper fourth milk molar AD 292’94 (Figure 3: 2); right upper third molar PQ AD 339 (Figure 3: 4); left lower second premolar AD 86’98 (Figure 3:6 and 9); left lower third molar AD 200’98 (Figure 3: 7 and 10); left lower third milk molar PQ AD 635 (Figure 3: 5 and 8); left radius PQ AD 3099; AD 52’97; left astragalus AD 619’94 (Figure 1:2);rightcalcaneum AD 50’97 (Figure 1:1); right third metatarsal AD 618’94 (Figure 5:1 and 2). The material is housed in the Geological Survey of Namibia in Windhoek. Description Mandible Of the six specimens which are all incomplete, two possess an important part of the horizontal ramus, with probably a very short symphysis (none showing the anterior end) whose maximum height is 35 mm. In the two cases the posterior border of the symphysis at the middle P /2 level; for Diceros douariensis the symphysis 125 is 100 mm long and 43 mm high, with the level of the posterior border is between P 12 and P /3; the posterior border is at the anterior part of P /4 in D. pachygnathus. Whereas the anterior part of the horizontal ramus is shallower, the posterior part (from about the M /2 level) has dimensions comparable with D. douariensis (Table 1). Middle-sized African Aceratheres and Dicerorhines are much smaller, as is Paradiceros, and Chilotheridium pattersoni shows different proportions. Symphysis shortness suggests a very weak development or an absence of lower incisors, a character of the Dicerotine group. Lower incisors Two lower tusks (in fact incisors and not canines as reported by Hooijer 1971) were recovered. AD 88’98 looks like a vestigial tooth, is knob-shaped and unworn. Its total length is 41.5 mm including 11 mm for the crown, the crown base transverse diameter is 9.5 mm, and its dorso-ventral diameter is 11 mm. It could be a di /l. AD 8 7 ’ 9 8 is a right lower incisor, feebly worn (Figure 3:1), it is 84 mm long (including 24 mm for the crown); at the crown base the transverse diameter is 19 mm, and its dorso-ventral diameter is 13.5 mm; the bevelled wear surface is 11 mm long and 10 mm wide; enamel thickness indicates a permanent tooth, i.e. an I 12. The cross section is an asym m etrical flattened ellipse. Chilotheridium tusks are much larger: after Hooijer 1971, the cross sections are respectively 22 x 17, 30 x 18,30x15 and 40 x 25 mm, with crown length (for much worn specimens) between 44 and 55 mm; the shape is different, being more asymmetrical (Hooijer 1971, Plate 6), and there is a cingulum at the base of the crown. Such reduced dimensions would preclude the use of the Arrisdrift tusk as an effective weapon, whereas tusk- bearing living (and thus fossil) rhinos have much larger tusks and use them as bayonets. I consider the small reduced lower adult tusk from Arrisdrift to be a representative of an evolutionary stage prior to the loss ofthe entire anterior dentition, the loss being accomplished in the Upper Miocene Dicerotine. Upper cheek teeth A well preserved D 4/ is weakly worn (Figure 3:1): its maximum height of 3 8 mm gives it a hypsodonty index of 81. The powerful paracone fold constitutes the sole relief on the outer wall, and the crochet is the only internal fold.There is a discontinuous crenellated lingual cingulum, mainly under the mouth of the inner valley. Its dimensions are about the same as these of.D. douariensis (Table 2). Two complete specimens of M 1/ or 2/ are known; one of them (AD 228’97), probably an M 1/, is only slightly worn and has a hypsodonty index of about 85. The ectoloph shows a large paracone fold and a weak vertical bulge in the middle of it. The crochet is the only internal fold. The protocone is weakly constricted on its anterior face. There is a weak crenellated inner cingulum under the mouth of the inner valley. The dimensions (Table 2) are slightly inferior to D. douariensis and largely inferior to A. campbelli but the two teeth are larger than those of D. leakeyi. The four available specimens of M 3/ show the same morphology (Figure 3:4): a strong paracone fold, a crochet as the only inner pleat, a weakly constricted protocone, an incomplete lingual cingulum and a crenellated postero-labial cingulum extending onto the posterior quarter of the outer surface. Its dimensions are the same as for three M 3/ of D. douariensis. Two right specimens of P 4/ have been recovered, one of them (AD 5 78’98) in a medium state of wear and the other (AD 649’97) very worn. The ectoloph has a strong parastyle, and a paracone fold which is thick but not very prominent; there is no mesostyle nor metacone fold. The sole inner fold is a strong crochet (but AD ■ Arrisdrift pachygnathus schleiermacheri Aceratheres pattersoni Figure 4: Diceros australis nov. sp: Simpson diagram of the radius compared with that of other Miocene rhinoceroses. Reference is Diceros bicornis. 1: Length; 2: proximal transverse diameter; 3: proximal anteroposterior diameter; 4: diaphysis transverse diameter; 5: diaphysis anteroposterior diameter; 6 : distal transverse diameter; 7: distal anteroposterior diameter. TABLE3 Compared dimensions of the lower cheek teeth of Diceros australis nov. sp ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. ARRISDRIFT AD PQ AD AD AQ AD AD AD PQ AD AD AD AD PQ AD PQ AD AD AD AD AD 8'98 635 44'98 200'98 468'97 163'97 378'94 134 86'98 157'95 432'95 827 330 556'94 300'97 313’98 437'97 D /2 ap 30 tr 18 D /3 ap 45 tr 25.5 D /4 ap tr M /1 ap 45 46.5 tr 37.5 M /2 ap 50.5 55 58 tr 38.5 37 39 33.5 M /3 ap 59 52.5 60 59 about 60 tr 36.5 39 35 35.5 P /2 ap 31.5 33 30 32 tr 20.5 19.5 22 P /3 ap 38 39 38 39 43 tr 28 29 27.5 29 P /4 ap 40.5 40 44.5 tr 32.5 35.5 Length P/3-P/4 83 Length M/1-M/3 156.5 157 Diceros douariensis B. heinzelini B. snowi Chil. pattersoni MSUR P. mukirii n mean min. max. Langental n mean min. max. East Africa Fort Teman D/2 D /3 D /4 ap tr ap tr ap tr 28.50 16.00 M /1 ap 2 48.00 47 49 48 2 42.00 40.5 43.5 39.00 35 tr 1 30.50 34.5 2 30.00 27 33 30.00 27 M /2 ap 2 56.75 55.5 58 50 51.50 3 54.50 50.5 57 47.00 42 tr 2 33.75 32 35.5 36 35.00 3 31.00 29.5 32.5 32.00 26 M /3 ap 1 54.00 60 58.00 2 59.50 56 63 54.00 43.5 tr 1 31.50 about 38 36.50 2 30.75 27.5 34 31.00 25 P /2 ap 1 26.00 30.00 4 23.12 20 25 22.00 24 tr 1 18.50 22.00 2 16.00 14 18 14 P /3 ap 1 35.50 36.50 4 33.62 25.5 38.5 32.50 27.5 tr 1 33.00 26.50 4 21.12 18.5 24 23.50 19.5 P /4 ap 1 43.00 44.50 4 37.50 34 39 37.50 30.5 tr 1 30.00 31.50 3 26.17 25.5 27 27.50 24.5 Length P/3-P/4 1 80.00 3 67.00 53 74.5 66.00 59 Length M /l-M /3 1 155.00 about 154 169.00 4 152.25 144 159 130.00 121 AD 223'97 46 37 126 127 649'97 shows a closed medifossette). There is a strong, continuous and crenellated lingual cingulum, and no trace of constriction of the protocone (Figure 3:3). Such a morphology, especially that of the outer wall - the best odontological character for rhino determinations, see Guerin 1980 a - is very close to that seen in Diceros douariensis and D. gr. pachygnathus-neumayri from Pikermi, as are the dimensions (Table 2). Lower cheek teeth Lower deciduous molars include one D /2 and one D /3. The latter tooth, which is weakly worn, shows sharp V-shaped internal valleys with no difference in level; traces of a labial cingulum are to be seen on the posterior lobe (Figure 3: 5 and 8). Dimensions (Table 3) are very similar to those (43 x 24 mm) of an isolated D /3 from Pikermi (Museum of Bologna, Italy). There is one incomplete isolated M /2, and there are three isolated M /3, the latter in a good state of preservation (Figure 3: 7 and 10). These are wider than the only known M /3 of D. douariensis, and are about as large as those of Brachypoptherium heinzelini and B. snowi, but much wider than Chilotheridium, Paradiceros and the medium-sized African Acerathere and Dicerorhinine (Table 3). The internal valleys have, for the anterior one, a sharp V-shaped transverse profile; the posterior valley is V-shaped in one case, U-shaped in the other two, the difference of level being moderate or strong. There are no lingual or labial cingula, but all the M /3 present a crenellated posterior cingulum of a very diverse shape. Two isolated specimens of P /2, three of P /3 and one of P /4 were available for study. The P /3 n° AD 157’95 shows no trace of wear and possesses a hypsodonty index of 108; the two internal valleys are V-shaped with a strong level difference; there are no labial nor lingual cingula but the anterior and posterior ones run slightly onto the labial surface, as also observed in the P /2 (Figure 3: 5 and 8). Lower cheek teeth included in tooth rows present the same characters; the most complete row (AD 300’97) has the lengths ofthe molar segment and of the two last premolars very close to the values observed in D. douariensis (Table 3) and D. gr. pachygnathus- neumayri. Radius and ulna The radius is longer than those of the largest D. gr. pachygnathus-neumayri and D. schleiermacheri, the last being more slender. The undifferentiated Acerathere/ Dicerorhine from Rusinga, which possesses the same dimensions and proportions as the middle-sized Upper Miocene Aceratheres of Europe, is smaller and with different proportions. The radius of Chilotheridium and especially B. snowi is stockier and much shorter (Table 4; Figure 4). TABLE 4. Compared dimensions of the radius of Diceros australis nov. sp ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. ARRISDRIFT MSUR B. snowi PQ AD 3099 Rusinga Jebel Zelten Length 435 305 286.5 prox tr 113 95 86.5 prox ap 70.5 57.5 51.5 diaphysis tr 64.5 51.5 48.5 diaphysis ap 42 47.5 40 dist tr 115 92 86 dist ap 83 69 53.5 dist artic tr 103 80.5 dist artic ap 54 41.5 D. gr. pachygnathus!neumayri Chilotheridium pattersoni n mean min. max. Stand, dev. coeff. var. n mean min. max. Length 9 364.22 342 375 9.536 2.62 1 327.00 327 327 prox tr 9 100.61 95 107 3.790 3.77 2 94.50 94 95 prox ap 9 65.00 55 72 5.315 8.18 1 53.00 53 53 diaphysis tr 9 59.11 55 63 2.667 4.51 2 45.00 44 46 diaphysis ap 9 38.78 33 47 4.402 11.35 2 32.50 32 33 dist tr 9 104.00 95 109.5 4.488 4.32 2 93.00 91 95 dist ap 9 65.78 60 71.5 3.833 5.83 2 56.75 54.5 59 dist artic tr 2 85.50 85 8 6 dist artic ap D. schleiermacheri Aceratheres n mean min. max. Stand, dev. coeff. var. n mean min. max. Stand, dev. coeff. var. Length 5 369.30 351.5 396 18.62 5.04 6 341.17 316 348 12.46 3.65 prox tr 4 99.38 94.5 104.5 4.33 4.35 9 86.67 78.5 100 7.96 9.19 prox ap 3 64.00 63 6 6 1.73 2.71 10 54.25 50.5 59.5 2.78 5.13 diaphysis tr 5 54.20 48 57.5 3.78 6.98 6 48.33 44 52.5 3.66 7.56 diaphysis ap 5 40.60 38 43 1.78 4.39 6 37.92 33 42.5 3.65 9.63 dist tr 5 95.20 87 1 00 5.71 6 .0 0 6 85.17 75 103.5 10.61 12.45 dist ap 5 65.60 61 69 3.99 6.08 7 54.50 50 61 3.93 7.20 dist artic tr 4 82.12 79 88.5 4.39 5.34 5 72.60 68.5 79.5 4.89 6.74 dist artic ap 4 44.75 44 45 0.50 1 .1 2 5 38.70 36.5 42.5 2.41 6.24 128 The proximal articulation does not possesses the very undulating anterior border nor the large re-entrant angle at the level of the coronoid process which characterize the genus Ceratotherium. But it shows a transversely elongated lateral facet the anterior border of which is only slightly retracted in relation to the anterior edge of the medial facet, and whose posterior border, regularly concave, constitutes moreover an obtuse angle with the posterior edge of the medial facet. These last characters speak in favour of the proximity of the large Arrisdrift rhino to the Dicerotine subfamily. Three ulnae have been recovered from Arrisdrift of which one only (AD 273’97) is complete; for a total length of 533 mm its proximal articular diameter is 95 mm and the proximal antero-posterior diameter is 157 mm. The other two pieces are a distal epiphysis of an adult specimen and the proximal end of a juvenile one. Carpus The semilunar presents an anterior surface whose width (42 mm) is similar to the height. The distal point of that surface, sited near the midline, is rounded. The length is 69.5 mm. One of the two known pyramidals (= cuneiforms) is well preserved; it is very large, and markedly wider (71.5 mm) than tall (63 mm). The only pisiform in the collection has a length of 70 mm, and is 29 mm wide; the height is 52 mm. One only ofthe two magnums found at Arrisdrift (AD 538’97) is attributable to the large rhino species. Its dimensions are as follows: T otal length: 104 mm Anterior width: 5 6 mm Anterior height: 45 mm Maximum height: 74 mm Sus-articularheight: 72 mm Such dimensions and proportions differ from those of D. schleiermacheri but are close to those of three magnums of Diceros gr. pachygnathus-neumayri; they are totally different from that of the other magnum recovered in the same site (Figure 1: 3-5 and Figure 2). In anterior view the bone presents a rhomboidal outline, rounded distally, and is higher than wide; the distal articulation is about as wide in its fore part as in its posterior part. Metacarpal II The only known specimen, a left one, is longer than the largest known specimens of Diceros gr. pachygnathus- neumayri and Dicerorhinus schleiermacheri, and is distinctly slender. That of Chilotheridium is very short and stocky, and that of true Aceratheres is shorter and shows very different proportions (Table 5). The proximal articulation is long and narrow, crescent­ shaped with a distinct notch on its posterior edge. On the lateral surface ofthe proximal epiphysis there is only one TABLE 5. Compared dimensions of the second metacarpal of Diceros australis nov. sp ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. ARRISDRIFT AD 536'97 Length 188 prox tr 41 prox ap 54 diaphysis tr 32.5 diaphysis ap 25 dist max tr 43 dist tr artic 42 dist ap 45.5 D. gr. pachygnathus!neumayri Chilotheridium pattersoni n mean min. max. Stand. coeff. n mean min. max. dev. var. Length 9 156.33 140.5 169 8.842 5.66 2 129.50 129.5 129.5 prox tr 9 44.67 37 54 5.385 12.06 2 43.00 42 44 prox ap 4 46.50 40 51 4.231 9.10 2 37.25 37 37.5 diaphysis tr 9 40.78 33.5 44.5 4.374 10.73 2 31.75 31 32.5 diaphysis ap 9 24.33 2 0 26 1.750 7.19 2 16.50 16 17 dist max tr 9 48.89 40 54 5.355 10.95 2 39.75 37 42.5 dist tr artic 9 43.17 34.5 48.5 4.644 10.76 2 34.00 31 37 dist ap 9 42.39 38.5 46 4.583 6.09 2 36.25 36 36.5 D. schleiermacheri Aceratheres n mean min. max. Stand coeff. n mean min. max. Stand coeff. dev. var. Length 3 168.83 156.5 179 11.41 6.76 5 133.20 120.5 148 13.30 9.98 prox tr 3 43.00 40 47 3.61 8.39 3 33.67 32 36 2.08 6.18 prox ap 3 42.50 40 44 2.18 5.13 3 33.17 29.5 40 5.92 17.86 diaphysis tr 4 36.88 34 40.5 2.72 7.37 4 32.38 28.5 36 3.09 9.55 diaphysis ap 4 22.50 18.5 27 3.54 15.71 4 19.00 17 21.5 1.96 10.30 dist max tr 3 44.67 40 47 4.04 9.05 4 37.75 36 40 1 .6 6 4.39 dist tr artic 3 40.17 39 41 1.04 2.59 4 34.38 32.5 36 1.49 4.34 dist ap 3 40.33 39.5 41.5 1.04 2.58 4 35.62 32 38.5 2.69 7.55 129 Figure 5. Third metapodials of Diceros australis nov. sp. 1: Mt III AD 618’94, front view; 2: Mt III AD 618’94, posterior view; 3: Me III AD 52’97, front view; 4: Me III AD 52’97, posterior view. Scale bar is 3 cm. articular facet, constricted in its medium part and expanding onto the whole height of the bone. The transverse section of the diaphysis is a rounded triangle. Metacarpal III Two left Me III have been recovered complete and the largest is marginally longer than the largest known specimens of Diceros gr. pachygnathus-neumayri and Dicerorhinus schleiermacheri, but are a little more slender. Brachypotherium snowi and B. heizelini are shorter and stockier, as is Chilotheridium. True Aceratheres show more or less analogous proportions but are much smaller. The Simpson diagram shows that the Arrisdrift Me III does not belong to a Brachypothere, nor to an Acerathere, whereas analogies with Diceros gr. pachygnathus- neumayri and Dicerorhinus schleiermacheri are noticeable (Table 6, Figures 5 and 6). The proximal articulation is very wide, triangular, and with a rectilinear anterior edge. There are two articular facets on the lateral surface of the proximal epiphysis; the anterior one is pentagonal with two parts, the lowest of which is more or less expanded anteroposteriorly according to the observed specimen; the posterior facet, located lower than the anterior one, is a rounded triangle whose width varies on each specimen. On the medial surface of the epiphysis there is a small inverted S- shaped facet whose height is variable. The transverse section of the diaphysis is trapezoidal, with a slightly convex anterior edge and a slightly concave posterior one; the lateral edge is straight and longer than the medial edge whose profile is more or less straight. Metacarpal IV This bone is much more longer and more slender than the largest measured specimens of Diceros gr. pachygnathus-neum ayri and D icerorhinus schleiermacheri (Table 7). The proximal articulation is triangular, a little longer than broad; such a width/height ratio is inverted for short-legged rhinos such as Brachypotherium and Chilotheridium. On the medial surface of the proximal epiphysis there are two articular facets; the anterior one is long and low, and semi-elliptical, while the posterior one is a vertical ellipse, much taller than broad. Tibia Only one tibia was found, and it is badly damaged especially the proximal epiphysis, but the total length can nevertheless be measured. As for the Me Ills the tibia is marginally longer than the largest known specimens of D iceros gr. pachygnathus-neum ayri and Dicerorhinus schleiermacheri, and is more slender (Table 8). Surprisingly enough, the dimensions of a broken distal epiphysis of a Diceros cf. douariensis from Baccinello V3 are identical to those of Arrisdrift! Astragalus Three astragali have been recovered of which two are complete (Figure 1: 2). Dimensions (Table 9) and proportions (Figure 4) are close to those of Diceros gr. pachygnathus-neumayri, and do not differ much from Dicerorhinus schleiermacheri. The astragalus of Brachypotherium snowi is slightly larger but markedly lower, and it is proportionally the same for 130 — heinzelini ---- ♦— snowi ---- O - — pachygnathus ------ * — schleiermacheri ------ A— Aceratheres ------ • — pattersoni 0,08 - 0,06 - 0,04 - 0,02 - - 0,02 - - -0,04 -- -0,06 -- -0,08 -- - 0,1 - Figure 6 : Diceros australis nov. sp: Simpson diagram of the third metacarpal compared with that of other Miocene rhinoceroses. Reference is Diceros bicornis. 1: length; 2: proximal transverse diameter; 3: proximal anteroposterior diameter; 4: diaphysis transverse diameter; 5: diaphysis anteroposterior diameter; 6 : distal maximal transverse transverse diameter; 7: distal transverse articular diameter; 8 : distal anteroposterior articular diameter diameter. TABLE 6. Compared dimensions o f the third metacarpal o f Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. ARRISDRIFT B. snowi B. heinzelini AD 52'97 AD 243'95 Jebel Zelten Rusinga Length 2 0 0 2 1 2 159.5 149.5 prox tr 6 8 63.5 74.5 6 6 prox ap 58 51.5 57 52 diaphysis tr 57.5 58.5 60.5 53 diaphysis ap 27 26.5 22.5 24.5 dist max tr 65 63.5 73.5 72.5 dist tr artic 60 60 58 58.5 dist ap 48 54.5 46.5 D. gr. pachygnathus/neumayri Chilotheridium pattersoni n mean min. max. Stand, dev. coeff. var. n mean min. max. Length 9 187.17 181 198 5.668 3.03 3 157.67 150 169 prox tr 6 65.50 62.5 74.5 4.461 6.81 3 54.33 50 61 prox ap 8 54.94 52 59 2.427 4.42 3 41.67 37 45 diaphysis tr 11 63.55 59 69 3.020 4,75 3 40.83 39 43 diaphysis ap 9 24.56 2 2 26.5 1.333 5.43 3 19.17 17.5 21.5 dist max tr 9 71.22 66.5 76 2.705 3.80 3 54.83 51 61 dist tr artic 10 56.15 52 59 2.174 3.87 3 46.33 44.5 49.5 dist ap 10 48.05 45 53 2.619 5.45 3 38.17 37.5 39 D. schleiermacheri Aceratheres n mean min. max. Stand, dev. coeff. var. n mean min. max. Stand, dev. coeff. var. Length 6 195.42 181 204 8.55 4.37 10 163.75 139.5 181 13.38 8.17 prox tr 9 62.67 58 69 3.70 5.90 10 53.35 50 59.5 3.09 5.80 prox ap 5 50.30 47.5 52 1.99 3.95 10 43.80 40 47.5 2.41 5.49 diaphysis tr 9 55.78 49.5 6 6 5.36 9.61 11 45.55 42 49 2.25 4.95 diaphysis ap 8 23.38 2 2 25.5 1.19 5.08 10 2 0 .2 0 17 24.5 2.16 10.71 dist max tr 7 63.50 60 69 3.15 4.96 10 55.25 49.5 60.5 3.68 6.65 dist tr artic 7 52.14 49 56 2.48 4.75 10 47.00 38.5 52 3.89 8.29 dist ap 7 46.71 45 49 1.41 3.02 7 41.71 38 44.5 2.56 6.15 131 ARRISDRIFT MSUR TABLE 7: Compared dimensions of the fourth metacarpal of Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. AD 404'97 N moyenne mini maxi Length about 188 2 158.75 152.5 165 prox tr 55 1 52.00 prox ap 51.5 1 46.00 diaphysis tr 37.5 2 34.00 34 34 diaphysis ap 27 2 21.25 20.5 2 2 dist max tr 51 2 46.25 42 50.5 dist tr artic 45 2 43.00 40 46 dist ap 53 2 38.75 37 40.5 D. gr. pachygnathus/neumayri Chilotheridium pattersoni n mean min. max. Stand, dev. coeff. var. n mean min. max. Stand, dev. Length 8 144.81 134 156 9.059 6.26 3 125.17 121.5 129.5 4.04 prox tr 8 47.81 43 53 3.535 7.39 2 35.50 34 37 2 .1 2 prox ap 8 42.12 37 47,5 3.410 8.09 2 38.00 32 44 8.49 diaphysis tr 8 37.69 31.5 41 3.162 8.39 3 26.17 23 30.5 3.88 diaphysis ap 8 24.75 2 0 29 2.726 11.01 3 18.00 17.5 18.5 0.50 dist max tr 8 46.69 39 52.5 4.166 8.92 3 42.17 37 47.5 5.25 dist tr artic 8 43.06 37.5 47 3.590 8.34 3 35.50 33.5 37 1.80 dist ap 8 41.00 37.5 46 2.712 6.62 3 34.33 33 37 2.31 D. schleiermacheri Aceratheres n mean min. max. n mean min. max. Stand, dev. coeff. var. Length 1 145.00 5 144.50 141.5 147.5 2.48 1.71 prox tr 2 49.25 47.5 51 7 42.86 38.5 48 3.58 8.35 prox ap 1 43.00 7 39.21 32 42 3.32 8.45 diaphysis tr 2 32.50 32.5 32.5 5 30.10 27.5 32.5 2.38 7.91 diaphysis ap 2 21.50 21 2 2 5 22.40 19 25 2.33 10.40 dist max tr 2 45.25 43 47.5 5 39.00 37.5 40 0.94 2.40 dist tr artic 2 42.25 38.5 46 5 38.90 36 43 2.90 7.46 dist ap 2 40.50 40 41 5 37.60 34 40 2.38 6.34 Arrisdrift - MSUR ---- ♦— snowi — pachygnathus ------ * ---- schleiermacheri ------ A— Aceratheres ~~ pattersoni Figure 7: Diceros australis nov. sp: Simpson diagram of the astragalus compared with that of other Miocene rhinoceroses. Reference is Diceros bicornis. 1: transverse diameter; 2: height; 3: anteroposterior medial diameter; 4: distal articular transverse diameter; 5: distal articular anteroposterior diameter; 6 : trochlea upper width; 7: distal maximal transverse diameter. Chilotheridium. The dimensions are inferior and the proportions are different for the true Aceratheres, and also for the undifferenciated sample of D. leakeyi-A. acutirostratum, whose similarity with true Aceratheres is noticeable. Among the qualitative characters, the tubercle on the lower part of the medial surface is located in the middle, well above the articular edge. Individual variation observed in the three astragali from Arrisdrift concerns mainly the height of the neck, the obliquity of the medial edge of the distal articulation, and the posterior development of the upper end of the medial lip. Calcaneum A damaged juvenile and three adult calcanei are known, of which two are complete (Figure 1:1). As for the astragalus, their dimensions (Table 10) and proportions are close to Diceros gr. pachygnathus-neumayri and PALAEONTOLOGIA AFRICANA VOLUME 36 - 2000 132 ARRISDRIFT Chilotheridium pattersoni max. 355 TABLE 8. Compared dimensions of the tibia of Diceros australis nov. sp ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. PQ AD 561 min. Length 440 319 diaphysis ap 57 47 dist tr 1 00 88 dist ap 80 6 6 dist artic tr 87 dist artic ap 75 D. gr. pachygnathus!neumayri D. cf. douariensis n mean min. max. Stand, dev. coeff. var. Baccinello V3 Length 5 390.40 368 420 19.97 5.12 diaphysis ap 7 58.36 49 73 8.80 15.07 58 dist tr 6 107.92 99 115 7.09 6.57 101 distap 7 79.00 71 99 10.72 13.57 80 dist artic tr dist artic ap Arrisdrift ~ pachygnathus ------ ♦— schleiermacheri — Aceratheres ---- ±-— pattersoni D. schleiermacheri Aceratheres n mean min. max. n mean min. max. Stand, dev. coeff. var. Length 2 398.00 386 410 9 361.22 328 383 20.66 5.72 diaphysis ap 2 58.25 57.5 59 9 47.39 38 53 5.82 12.28 dist tr 2 103.50 101 106 9 86.17 72.5 91.5 6.26 7.26 dist ap 2 72.25 69 75.5 11 62.55 53 68 5.01 8.01 dist artic tr 1 82.50 3 71.00 60 79 9.85 dist artic ap 1 60.00 3 50.67 46 55 4.51 0,08 -- 0,06 -- 0,04 -- 0,02 - - 0 — A - 0,02 + -0,04 - -0,06 - -0,08 - - 0,1 - Figure 8 : Diceros australis nov. sp: Simpson diagram ofthe third metatarsal compared with that of other Miocene rhinoceroses. Reference is Diceros bicornis. 1: length; 2: proximal transverse diameter; 3: proximal anteroposterior diameter; 4: diaphysis transverse diameter; 5: diaphysis anteroposterior diameter; 6 : distal maximal transverse transverse diameter; 7: distal transverse articular diameter; 8 : distal anteroposterior articular diameter diameter. D. schleiermacheri, having nothing to do with those of Paradiceros, Chilotheridium nor Aceratheres. In posterior view the sustentaculum axis makes a right angle with the axis of the body of the bone. In lateral view the front of the tuberosity is situated well behind the beak (= foremost part of the bone), the anterior edge between the two points being oblique and slightly concave. The posterior edge of the surface is globular for the upper two thirds of its height, and depressed for the last third, especially in specimen PQ AD 601. Individual variation is noticeable in the proximal part of the bone when observed from the posterior surface: shaped as an inverted V for PQ AD 601, it is flat for AD 50’97. Other tarsals The cuboid is very large: its total length is 77 mm, its total height 61 mm, and maximum width 52.5 mm. The anterior surface is much taller than broad (53 and 41.5 mm), and its lateral edge is longer than the medial one. Two naviculars have been recovered, and are broader 133 TABLE 9. Compared dimensions of the astragalus of Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. Arrisdrift Arrisdrift D. gr. pachygnathus/neumayri AD 619'94 PQ AD 1219 n mean min. max. Stand. coeff. var. dev. Transverse diameter 101 1 0 0 7 98.57 94 104 3.65 3.70 Height 95 96 6 87.17 84 92 3.55 4.07 ap medial diameter 63.5 64.5 6 63.00 61 65 1.90 3.01 Dist artic tr 75 78 7 81.07 76.5 8 6 3.10 3.83 Dist artic ap 55 53.5 7 50.86 45 53.5 3.33 6.54 Trochlea width 72 77 6 69.83 61 77.5 5.77 8.26 Distal tr diameter 80.5 85 5 84.90 82 90.5 3.47 4.09 D. schleiermacheri Brachypotherium snowi n mean min. max. Stand. coeff. n mean min. max. dev. var. Transverse diameter 11 91.45 86.5 99 3.60 3.93 2 108.75 105 112.5 Height 13 85.35 78.5 93 4.72 5.53 1 82.00 ap medial diameter 12 61.79 55 70 4.13 6 .6 8 2 59.00 58 60 Dist artic tr 8 73.00 62 82 6.65 9.11 2 82.25 80 84.5 Dist artic ap 10 47.95 44.5 55 2.83 5.91 Trochlea width 12 66.63 61 75 3.73 5.60 1 51.00 Distal tr diameter 10 79.75 76 8 6 3.81 4.78 2 92.75 90.5 95 Aceratheres Chilotheridium pattersoni n mean min. max. Stand. coeff. n mean min. max. Stand. dev. var. dev. Transverse diameter 29 79.60 72 88.5 4.35 5.46 3 88.50 85.5 92 3.28 Height 30 70.07 62 81 4.58 6.54 3 70.17 68.5 71 1.44 ap medial diameter 26 52.44 45 59 3.59 6.85 3 53.67 52 55.5 1.76 Dist artic tr 29 64.59 56.5 73 3.88 6 .0 1 3 71.00 64 79 7.55 Dist artic ap 25 39.68 35 47 2.69 6.77 2 40.50 38 43 3.54 Trochlea width 31 52.39 46 65 5.23 9.98 3 55.33 52 58 3.06 Distal tr diameter 28 70.95 65 76.5 3.12 4.40 3 75.33 73 79 3.22 MSUR n mean min. max. Stand. coeff. dev. var. Transverse diameter 8 80.62 75.5 84 3.41 4.23 Height 7 72.79 69 78.5 3.71 5.09 ap medial diameter 7 52.14 47.5 56 3.16 6.06 Dist artic tr 8 6 8 .0 0 65 74 3.02 4.45 Dist artic ap 6 38.83 33.5 43.5 3.80 9.79 Trochlea width 7 48.79 45 50 1.89 3.87 Distal tr diameter 8 73.81 70.5 78.5 3.09 4.19 ~ schleiermacheri -------♦— pachygnathus ~ Aceratheres ---- ±— pattersoni Figure9. Diceros australis nov. sp: Simpson diagram of the limb segments compared with those of other Miocene rhinoceroses. Reference is Diceros bicornis. 1: ulna length; 2: radius length; 3: Me II length; 4: Me III length; 5: Me IV length; 6 : tibia length; 7: Mt II length; 8 : Mt III length; 9: Mt IV length. 134 TABLE 10. Compared dimensions of the calcaneum of Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. ARRISDRIFT ARRISDRIFT ARRISDRIFT Paradiceros MSUR AD 50'97 PQ AD 601 AD 530'95 Kisegi Height 158.5 153 153 92.5 130.5 Head tr 58 55 64 36 52.5 Head ap 77 67 50 54 middle width 41.5 40 33 43 Sustentaculum tr 77.5 79 77 50 81 maximum width 81 81 80 55.5 85.5 maximum ap 84 75.5 about 75 63 D. gr. pachygnathus!neumayri Chilotheridium pattersoni n mean min. max. Stand. coeff. n mean min. max. Stand. coeff. dev. var. dev. var. Height 7 143.36 132 151.5 6.30 4.39 3 120.83 113 132 9.93 8 .22 Head tr 6 58.42 54 63 3.64 6.23 3 44.33 42 48.5 3.62 8.16 Head ap 7 75.07 65 82 5.76 7.68 3 67.67 60 74 7.10 10.48 middle width 2 46.50 45 48 2 .12 4.56 Sustentaculum tr 7 82.07 74 87.5 4.64 5.65 2 70.00 70 70 0 .0 0 0 .0 0 maximum width maximum ap 5 77.90 72 83 5.03 6.46 3 59.17 57 62 2.57 4.34 D. schleiermacheri Aceratheres n mean min. max. Stand. coeff. n mean min. max. Stand. coeff. dev. var. dev. var. Height 5 142.10 134 149 6.71 4.72 20 108.82 98.5 123.5 6 .66 6 .1 2 Head tr 6 53.17 50.5 55 1.78 3.35 2 0 42.97 35 49 3.93 9.13 Head ap 6 72.67 68.5 79.5 5.97 9.01 19 61.03 49.5 79 6.55 10.73 middle width 4 40.13 37 43.5 2.78 6.93 6 33.75 26 41 6.03 17.87 Sustentaculum tr 5 80.90 72.5 88 6.37 7.87 15 70.33 61 78.5 4.14 5.88 maximum width maximum ap 6 74.50 69 86 6.72 9.01 20 59.58 51 70 5.10 8.55 than long: respectively 67 x 56.5 mm for a height of 40 mm and 78 x 56.5 mm for a height of 38 mm. The only big cuneiform preserved is 44.5 mm long, 26 mm wide, and 35.5 mm high. Metatarsal II Four Mt IIs were found, of which two are complete or nearly so (during fossilisation they were broken but knitted again into place). They are much longer but more slender than the largest known specimens of Diceros gr. pachygnathus-neum ayri and D icerorhinus schleiermacheri. That of Chilotheridium is very short and relatively stockier, and that of true Aceratheres is shorter with different general proportions (Table 11). On the lateral surface of the proximal epiphysis there are two well separated articular facets, both taller than broad, with an elliptical outline. The transverse section of the diaphysis is a rounded trapezium, widest on the posterior border and with a sharp anterior angle. In one specimen (AD 442 ’ 97) the posterior part of the proximal epiphysis is strongly expanded rearwards, the lateral facets are broader and there are two articular facets on the medial face. the sus-articular transverse distal diameter. It is significantly longer than those of Dicerorhinus schleiermacheri. Chilotheridium is much shorter and relatively stockier. True Aceratheres show different proportions and are smaller (Table 12, Figure 8). The proximal articulation is very wide, triangular, with a convex anterior edge whose point of bending is laterally offset; the antero-lateral angle is pointed; the medial edge begins with a cant followed by a shallow depression. The anterior articular facet on the lateral surface of the proximal epiphysis is located higher than the posterior one, which possesses an elliptical elongated outline. The transverse section ofthe diaphysis is trapezoidal, with a convex anterior edge and a concave posterior one; the lateral edge is straight, and the medial one is slightly convex. Individual variation observed concerns mainly the outline of the anterior articular facet of the lateral surface of the proximal epiphysis which is more or less triangular. It also concerns the convexity of the anterior edge and the concavity of the posterior edge of the transverse section. Metatarsal III Four Mt Ills have been recovered, including one broken into two parts more or less linked together, and another one whose incomplete proximal epiphysis is partly preserved in gypsum. The bone (Figure 5:1-2) is about as long as the largest known specimens of Diceros gr. pachygnathus- neumayri and has about the same proportions except Metatarsal IV Only one Mt IV is known, and it is in a bad state of preservation. As for the Mt II, it is much longer than the largest known specimens of Diceros gr. pachygnathus- neumayri and Dicerorhinus schleiermacheri, but is not especially slender. That of Chilotheridium is very short, and that of true Aceratheres is shorter with different general proportions (Table 13). 135 TABLE 11. Compared dimensions of the second metarsal of Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. Arrisdrift Arrisdrift Arrisdrift Arrisdrift Chilotheridium pattersoni MSUR AD 744'97 PQ AD 251 AD442’97 AD 348'95 Loperot Loperot Kiboko Length 182.5 181 129 115 153 prox tr 30 31 32 31 about 36 30 27 prox ap 51 47 57 51 37.5 34.5 diaphysis tr 31 30 31.5 23 19.5 diaphysis ap 30 25.5 29 21 18.5 dist max tr 40.5 39 42 35 29 dist tr artic 38.5 37.5 38.5 32.5 28 dist ap 46 40 43 36.5 30 D. schleiermacheri n mean min. max. Stand, dev. coeff. var. Length 3 153.33 150 156 3.06 1.99 prox tr 3 33.83 27 40.5 6.75 19.96 prox ap 3 45.67 43 50.5 4.19 9.18 diaphysis tr 2 27.00 26 28 1.41 5.24 diaphysis ap 2 27.75 27 28.5 1.06 3.82 dist max tr 3 37.17 35.5 39 1.76 4.72 dist tr artic 3 35.00 33 37 2 .0 0 5.71 dist ap 3 39.17 37 40.5 1.89 4.83 D. gr. pachygnathus/neumayri n mean min. max. Stand, dev. coeff. var. Length 5 153.70 147.5 157.5 4.04 2.63 prox tr 5 33.60 30.5 37 3.03 9.01 prox ap 5 45.70 42.5 49 2.73 5.97 diaphysis tr 5 34.80 32 37.5 2.08 5.98 diaphysis ap 5 25.20 23.5 27 1.48 5.89 dist max tr 4 43.50 40 45 2.38 5.47 dist tr artic 5 39.30 36.5 41 1.75 4.46 dist ap 5 43.50 39 47 2.96 6.80 Aceratheres n mean min. max. Stand, dev. coeff. var. Length 8 137.06 117.5 165.5 14.37 10.49 prox tr 9 28.00 25.5 31 1.70 6.06 prox ap 9 39.17 35 41.5 2.26 5.78 diaphysis tr 7 26.57 23.5 32 2.99 11.26 diaphysis ap 7 21.93 19 25 2.13 9.71 dist max tr 7 36.07 31 40 3.18 8.82 dist tr artic 8 32.88 26 40 4.60 14.00 dist ap 7 36.50 33 40.5 2.80 7.67 Limb segments: Simpson diagram of the limb segments (Figure 9) shows once more similarities with Dicerorhinus schleiermacheri and Diceros gr. pachygnathus- neumayri, with, as a noticeable particularity, a much greater relative length of the lateral and medial metapodials. THE SMALLER RHINO FROM ARRISDRIFT, cf. Chilotheridium pattersoni An isolated magnum (AD 618’97) is totally different (Figure 1: 3) from that attributed to Diceros australis. Its dimensions are as follows: Total length: Anterior width: Anterior height: Maximum height: Sus-articular height: 91 mm 50 mm 27 mm 54.5 mm 52.5 mm Shallow and very wide, with a flattened and oblique anterior surface, it shows an inverted width/height ratio (Figure 2) which suggests a small to medium sized short­ legged form, probably Chilotheridium, which was defined at Loperot, Kenya, the age of which is about the same as Arrisdrift. For ten incomplete specimens of Chilotheridium from Loperot, Hooijer (1971, Table 14) gives a slightly greater anterior height (3 0 to 3 3 mm) and a slightly lesser anterior width (44 to 49 mm) but this is not a significant difference, the method of measuring probably not being exactly the same. THE LANGENTAL BRACHYPOTHERE, Brachypotherium heinzelini A complete magnum (LT 384’96) presents the following dimensions: Total length: 84.5 mm Anterior width: 57 mm Anterior height: 3 9 mm Maximum height: 58.5 mm Sus-articular height: 57 mm The Langental magnum (Figure 1: 5) is thus much larger than the smaller specimen from Arrisdrift but 136 Compared dimensions of the third metatarsal of Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. TABLE 12. Arrisdrift Arrisdrift Arrisdrift Arrisdrift AD 618'94 PQ AD 249 PQ AD 1191 PQ AD 183 C. pattersoni Loperot Length 197.5 197 about 180 about 178 128 prox tr 57.5 61 54 43.5 prox ap 52 49 40 diaphysis tr 50 51.5 52.5 44 36 diaphysis ap 26 25.5 25.5 18.5 dist max tr 61.5 60.5 57.5 55.5 48 dist tr artic 53 57 52.5 51 43 dist ap 46 47.5 42 42 35 D. schleiermacheri n mean min. max. Stand, dev. coeff. var. Length 2 173.25 171.5 175 2.48 1.43 prox tr 1 48.00 prox ap 1 40.00 diaphysis tr 2 45.00 43.5 46.5 2 .1 2 4.71 diaphysis ap 2 23.25 23 23.5 0.35 1.52 dist max tr 2 55.50 53.5 57.5 2.83 5.10 dist tr artic 2 47.75 46 49.5 2.48 5.18 dist ap 2 39.00 33 45 8.49 21.76 D. gr. pachygnathus!neumayri n mean min. max. Stand, dev. coeff. var. Length 9 174.56 165 194.5 8.56 4.90 prox tr 8 60.06 57 64.5 2.32 3.86 prox ap 8 50.88 45 57.5 4.96 9.74 diaphysis tr 9 53.22 51.5 55 1.23 2.31 diaphysis ap 9 25.33 22.5 28.5 1.97 7.77 dist max tr 7 66.93 60.5 71.5 3.76 5.61 dist tr artic 8 54.50 49.5 60.5 3.65 6.69 dist ap 8 46.50 41.5 49 2.41 5.17 Aceratheres n mean min. max. Stand, dev. coeff. var. Length 11 150.36 130 166 11.44 7.61 prox tr 10 46.25 40 53.5 4.63 1 0 .0 0 prox ap 10 41.90 38 46 2.76 6.58 diaphysis tr 11 41.32 37.5 46.5 2.70 6.55 diaphysis ap 10 19.90 16.5 24.5 2.76 13.85 dist max tr 11 52.45 47 60.5 4.12 7.85 dist tr artic 11 45.45 40.5 51.5 3.23 7.10 dist ap 11 37.82 32 42.5 3.47 9.17 presents the same kind of width/height ratio (Figure 2), which is typical of Brachypotheres and Chilotheres. I thus assign it to Brachypotherium heinzelini, a large brachypothere whose magnum remains undescribed but the presence of which is already known at the site since the study of K. Heissig (1971). UNDETERMINED RHINOS FROM FISKUS AND AUCHAS MINE From Fiskus a very worn and poorly preserved upper right premolar (P 3/ or P 4/) was recovered. Its total length is 42 mm for a collar width of 52 mm. The ectoloph seems flat. Dimensions are compatible with the P 3/ of a Brachypothere or the P 4/ of a large true Acerathere. From Auchas Mine there is an atlas not completely cleared from the sediment, and a totally encrusted mandibular fragment which was found during the field trip following the 1998 PSSA meeting at Windhoek. CONCLUSIONS Four mammal-bearing Miocene sites excavated since 1991 by the Namibia Paleontology Expedition have yielded rhinoceros remains: Langental, Fiskus, Auchas Mine and Arrisdrift, the last three being new. At Langental a well preserved magnum was found. It probably pertains to Brachypotherium heinzelini, a half mandible of which was recovered from the site before the First World War and which was identified by K. Heissig (1971). From Fiskus there is a very worn upper premolar, perhaps from an Acerathere or a Brachypothere. An atlas vertebra and a mandibular fragment, both encrusted with sediment and thus specifically undeterminable, have been recovered from Auchas Mine. A great number of rhino specimens were found at Arrisdrift. All but one of the 81 fossil pieces constitute 137 Compared dimensions of the fourth metatarsal of Diceros australis nov. sp. ap= anteroposterior; artic= articular; diam= diameter; dist= distal; horiz= horizontal; prox= proximal; tr= transverse. TABLE 13. Arrisdrift Chilotheridium pattersoni PQ AD 253 Loperot Loperot Length about 182 111 113 prox tr 44 41 40.5 prox ap 42 40 about 38,5 diaphysis tr 35.5 22.5 22.5 diaphysis ap 22.5 20.5 2 0 dist max tr 42 33 30.5 dist tr artic 41 34.5 32 dist ap about 36 35.5 34.5 D. schleiermacheri n mean min. max. Length 2 153.50 152 155 prox tr 2 42.25 37 47.5 prox ap 1 50.00 50 50 diaphysis tr 2 27.75 26.5 29 diaphysis ap 2 29.25 28 30.5 dist max tr 2 36.00 35.5 36.5 dist tr artic 2 36.50 35 38 dist ap 2 42.50 42 43 D. gr. pachygnathus!neumayri n mean min. max. Stand, dev. coeff. var. Length 8 148.31 138.5 166.5 9.05 6 .1 0 prox tr 8 48.63 43 53 3.15 6.47 prox ap 8 46.88 42.5 51 2.90 6.19 diaphysis tr 8 32.12 30 35 1.64 5.11 diaphysis ap 8 29.00 24.5 32 2.79 9.62 dist max tr 8 41.12 37 45 2.62 6.36 dist tr artic 8 39.75 35.5 43 2.78 6.99 dist ap 8 42.75 40 45 1.93 4.51 Aceratheres n mean min. max. Stand, dev. coeff. var. Length 10 131.40 117.5 144 9.02 6.87 prox tr 11 40.95 37 44.5 2.08 5.08 prox ap 11 38.09 32.5 42.5 3.59 9.43 diaphysis tr 10 26.85 23 30 2.08 7.76 diaphysis ap 10 24.85 21 28 2 .2 1 8.90 dist max tr 9 31.56 29 34.5 1.98 6.26 dist tr artic 8 30.25 27.5 35.5 2.87 9.47 dist ap 10 35.15 31 37.5 2.48 7.07 a homogeneous sample pertaining to a very large species of cursorial rhino. The exception is an isolated magnum which suggests a small to medium sized short-legged form, perhaps Chilotheridium pattersoni, a species described from Loperot in Kenya, the age of which is about the same as Arrisdrift, i.e. 17 Ma. The large form from Arrisdrift seems to be the largest of the African Miocene Rhinos; the size and proportions of the metapodials and the other limb bones suggest a strong analogy with Diceros gr. pachygnathus-neumayri of the Upper Miocene of the Near East; the type of construction of the upper cheek teeth, in particular the fourth premolar, is of Dicerotine type and presents, as do the dimensions, close resemblances with Diceros douariensis of the Upper Miocene of North Africa and Italy; the mandible shows analogies with the Dicerotines, especially the apparently short symphysis. This rhino is Diceros australis nov. sp., so far the oldest known species of the subfamily. ACKNOWLEDGEMENTS I am greatly indebted to Dr. Brigitte Senut and Dr. Martin Pickford for offering me the Miocene Namibian rhinoceros remains for study and report, and for inviting me to the September 1998 PSS A meeting at Windhoek, where I presented a preliminary version ofthe present paper. Dr. Vera Eisenmann made useful remarks, provided help for the statistical interpretation and did the photograph for F igure 3:1. Dominique Gommery kindly made the cast of the figured lower tusk. Dr M. Pickford kindly corrected the English. 138 REFERENCES AGUIRRE, E. & GUERIN, C. 1974. Premiere decouverte d’un Iranotheriinae (Mammalia, Perissodactyla, Rhinocerotidae) en Afrique: Kenyatherium bishopi nov. gen. nov. sp. de la formation vallesienne (Miocene superieur) de Nakali (Kenya). Estudios geologicos 30, 229-233. GERAADS, D. 1986. Sur les relations phyXetiquesde Dicerorhinus primaevus Arambourg, 1959, rhinoceros duVallesiend’Algerie. Comptes rendus hebdomadaires des seances de I ’Academie des Sciences de Paris, I I302 (13), 835-837. ------- 1989. Vertebres fossiles du Miocene superieur du Djebel Krechem el Artsouma (Tunisie centrale). Comparaisons biostratigraphiques. Geobios 22 (6 ), 777-801. GUERIN, C. 1966. Diceros douariensis nov. sp., un rhinoceros du Mio-Pliocene de Tunisie duNord. Documents du Laboratoire de Geologie de la Faculte des Sciences de Lyon 16,1 -50. ------- 1976. Les restes de rhinoceros du gisement miocene de Beni-Mellal, Maroc. Geologie mediterraneenne 3 (2), 105-108. ------- 1980 a. Les rhinoceros (Mammalia, Perissodactyla) du Miocene terminal au Pleistocene superieur en Europe occidentale. Comparaison avec les especes actuelles. Documents des Laboratoires de Geologie de Lyon 79 (1-3), 1-1185. ------- 1980 b. A propos des rhinoceros (Mammalia, Perissodactyla), neogenes et quatemaires d’Afrique: essai de synthese sur les especes et sur les gisements. Proceedings o f the 8th. PanAfrican Congress o f Prehistory and Quaternary Studies, Nairobi, September, 1977, TILLMIAP edit., Nairobi, 58-63. ------- 1989. La famille des Rhinocerotidae (Mammalia, Perissodactyla): systematique, histoire, evolution, paleoecologie. Cranium 6 (2), 3-14. ------- & DEMATHIEU, G. 1993. Empreintes et pistes de Rhinocerotidae (Mammalia, Perissodactyla) du gisement pliocene terminal de Laetoli (Tanzanie). Geobios 26 (4), 497-513. --------1994. Les Rhinoceros (Mammalia, Perissodactyla) du Neogene de l’Ouganda, 263-279, In: Senut, B. & Pickford, M. Eds, Geology and Palaeobiology ofthe Albertine Rift Valley, Uganda-Zaire, vol. II: Palaeobiology, CIFEG edit, Orleans, occasional publication 1994/ 29. HAMILTON, W.R. 1973. North African Lower Miocene Rhinoceroses. Bulletin o f the British Museum (Natural History), London 24 (6 ), 351-395. ------- & VAN COUVERING, J.A. 1977. Lower Miocene Mammals from South West Africa. Bulletin o f the Desert Ecological Research Unit, Oct. 1977,9-11. HEINZ, R. 1933. Ein vorzeitlicher Trankplatz in der Namibwiiste bei Luderitzbucht (Deutsch-Siidwestafrika). Mitteilungen der Geographischen Gesellschaft in Hamburg XLIII, 267-302. HEISSIG, K. 1971. Brachypotherium aus dem Miozan von Sudwestafrika. Mitteilungen der Bayerische Staatssammlungfur Palaontologie und historische Geologie, Munchen 11, 125-128. HOOIJER, D.A. 1966. Miocene rhinoceroses of East Africa. Bulletin o f the British Museum (Natural History), London, 13 (2), 119-190. --------1968. A rhinoceros from the late Miocene of Fort Teman, Kenya. Zoologische Mededelingen 43 (6 ), 77-92. ------- 1971. A new rhinoceroses from the late Miocene of Loperot, Turkana District, Kenya. Bulletin o f the Museum o f Comparative Zoology. 42 (3), 339-392. ------- 1973. Additional Miocene to Pleistocene rhinoceroses of Africa. Zoologische Mededelingen 46 (11), 149-178. ------- 1978.19: Rhinocerotidae, 371 -378, In: Maglio V. J. & Cooke H.B.S. Eds, Evolution o f African Mammals, Cambridge (Mass.), Harvard University Press. NAKAYA, H., PICKFORD, M., YASUI, K., &NAKANO, Y., 1999 (dated 1987). Additional large mammalian fauna from the Namurungule Formation, Samburu Hills, Northern Kenya. Afr. Study Monogr. Suppl. Issue 5, 79-130. PICKFORD, M., SENUT, B. & HADOTO, D. 1993. Geology and palaeobiology ofthe Albertine Rift Valley, Uganda-Zaire, vol. I: Geology, CIFEG, Orleans, occasional publication 1993/24, 190 p. ------- , SENUT, B„ MEIN, P., MORALES, J., SORIA, D., NIETO, M., WARD, J. & BAMFORD, M. 1995. The discovery of lower and middle Miocene vertebrates at Auchas, southern Namibia. Comptes rendus hebdomadaires des seances de I ’Academie des Sciences de Paris, II a 322, 901-906. ------- f SENUT, B„ MEIN, P., GOMMERY, D., MORALES, J., SORIA, D„ NIETO, M. & WARD, J. 1995. Preliminary results of new excavations at Arrisdrift, middle Miocene of southern Namibia. Comptes rendus hebdomadaires des seances de I ’Academie des Sciences de Paris, II a 322, 991-996. PROTHERO, D.R., GUERIN, C. & MANNIN, G. E. 1989. The History of the Rhinocerotoidea. In: Prothero, D.R. & Schoch, R.M., Eds, The Evolution ofPerissodactyls (IVth Theriological Congress, Edmonton, Alberta, 1985), 321-340. New York, Oxford Univ. Press. STROMER E. 1926. Reste Land- und Susswasser-bewohnender Wirbeltiere aus den Diamantfeldem Deutsch-Sudwestafrikas. In: Kaiser, E. Ed., Die Diamantenwuste Siidwestafrikas, 107-153 Dietrich Reimer (Ernst Vohsen) A.D. edit., Berlin, Bd. II.