New carnivores from the basal Middle Miocene of Arrisdrift, Namibia Autor(en): Morales, Jorge / Pickford, Martin / Soria, Dolores Objekttyp: Article Zeitschrift: Eclogae Geologicae Helvetiae Band (Jahr): 91 (1998) Heft 1 PDF erstellt am: 04.10.2021 Persistenter Link: http://doi.org/10.5169/seals-168406 Nutzungsbedingungen Die ETH-Bibliothek ist Anbieterin der digitalisierten Zeitschriften. Sie besitzt keine Urheberrechte an den Inhalten der Zeitschriften. Die Rechte liegen in der Regel bei den Herausgebern. Die auf der Plattform e-periodica veröffentlichten Dokumente stehen für nicht-kommerzielle Zwecke in Lehre und Forschung sowie für die private Nutzung frei zur Verfügung. Einzelne Dateien oder Ausdrucke aus diesem Angebot können zusammen mit diesen Nutzungsbedingungen und den korrekten Herkunftsbezeichnungen weitergegeben werden. Das Veröffentlichen von Bildern in Print- und Online-Publikationen ist nur mit vorheriger Genehmigung der Rechteinhaber erlaubt. 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Arrisdrift, Namibia ABSTRACT ZUSAMMENFASSUNG The early Middle Miocene locality .11 Arrisdrift, Namibia, has yielded seven Die früh-mitteleozäne Lokalität Arrisdrift. Namibia, lieferte sieben Spezies species of carnivores, comprising a giant creodont. two amphicyonids. a von Carnivoren. bestehend aus einem Riesen-Creodonten, zwei Amphicyoniden. mustelid. a stenoplesictid and two felids. The mustelid. stenoplesictid and fe- einem Musteliden. einem Stenoplesictiden und zwei Fehden. Der lids belong to new genera and one of the amphicyonids is a new species, while Mustelide. Stenoplestictide und die Fehden gehören zu neuen Gattungen. Einer the other forms are similar to species already known from East Africa and der Amphicyoniden ist eine Spezies, während die anderen Formen Arten ähnlich Europe. sind, die schon von Ostafrika und Europa bekannt sind. Comparisons of the Namibian fossils with those from other parts of Africa Vergleiche der namibischen Fossilien mit solchen aus anderen Gebieten and Europe suggest that Arrisdrift correlates with Faunal Set P Ilia of East von Afrika und Europa weisen darauf hin. dass Arrisdrift mit «Faunal Set P Africa (Pickford 1981 and the early part of MN04 of the European mammal lila» von Ostafrika (Pickford 1981 und dem frühen MN04 der europäischen zonation (ca 17-17.5 Ma) (Mein 1990). Säugetier-Zonierung (ca 17-17.5 Ma) (Mein 1990) korrelierbar ist. 1. Introduction The early Middle Miocene site at Arrisdrift, Namibia (fig. 1). It is most likely that the Arrisdrift channel only occasionally which was discovered in 1976 during diamond prospecting had water flowing through it. perhaps on a seasonal basis when activities, yielded a rich and diverse fauna (Corvinus & Hendey the Proto-Orange overtopped its principal channel. 1978: Harris 1977; Pickford 1987) including four species of Fossils are scattered throughout the channel fill, the average Carnivora (Hendey 1978). Recently, palaeontological study of grade of the deposit being 50 fossils per cubic metre. There the site has continued thanks to the support and encouragement is no obvious bone-bed or horizon at which the fossils occur. of Namdeb Diamond Corporation (Pty) Ltd. (formerly Many of the fossils have been reworked locally from a pre-existing Consolidated Diamond Mines (CDM) (Pty) Ltd). deposit, while some of them are in their primary burial The fossiliferous sediments occur in a 14 metre wide channel context. However, the reworked faunal elements consist of the carved into bedrock to a depth of 2 metres, located some same species as those in primary context, and consequently, 150 metres east of the main channel of the Proto-Orange there is not a great deal of time difference between the two River. The infilling of this lateral channel consists of conglomerates, assemblages. The surfaces of many of the fossils are cracked, sands, silts and clays with gypsum, deposited in a complex suggesting that they were exposed to the sun prior to being cut-and-fill sequence. The clay layers are thin and appear buried, while several of the larger mammal bones have tooth to he clay drapes of the sort that settle out of quiet water, while marks of the sort made by crocodiles. the cut-and-fill character of the succession indicates that the Some of the carnivores described here were collected in infilling was subjected to erosion from time to time, each 1976-1978 by Corvinus (1978). while preliminary descriptions episode of erosion being followed by deposition of new sediment. and interpretations were published by Hendey (1978). New Departamento de Paleobiologia. Museo Nacional de Ciencias Naturales. J. Gutierrez Abascal 2. E-28006 Madrid Chaire de Paléoanthropologie et de Préhistoire. Collège de France. 11. place Marcelin Berthelot. F-75005 Paris New carnivores from the Miocene of Namibia 27 SPERRGEBIET, NAMIBIA W É__r Bi -UDERITZ •T.C.: MANSKCP A C «INDHOEK J 0 10 20 30 mm. Fig. 2. AD 375'94. P4. llyainailotirus sulzeri. A. lingual view. B. buccal view. o C. occlusal view. 0 10 20 30 40 SO » Road -'. Track Description ARRISDRIFT » Fossiliferous locality M' with moderate parastyle. paracône high, wide and subdivided at its reduced, much smaller than the 0'° tip. Metastyle para- cone. Protocone located anterior to the paracône. but slightly behind the parastyle. with the cusp in the shape of a horseshoe Fig. 1. Location of Arrisdrift. an early Middle Miocene site in Southern Namibia. separated from the paracône by a valley. Cingulum only at the base of the parastyle. Discussion This tooth is extremely similar to its homologue in Hyainailourus sulzeri (Ginsburg 1980: Azanza et al. 1993) and to that of material, including the first creodont from the site, was Pterodon napakensis (Savage 1965: Ginsburg 1980). Both these unearthed by the Namibia Palaeontology Expedition in 1994 and forms possess similar sized molars, especially if we take into 1995. The material studied is currently housed in the Museum account the fact that the creodonts display strong interspecific- of the Geological Survey of Namibia (Windhoek. Namibia). size variability in their dentition, which can reach values of nearly 100%. Morphologically the differences between the above two 2. Systematic palaeontology species are minor, and it is possible that they belong to a single Order Creodonta Cope 1875 species. Nevertheless, the Arrisdrift M1. as in H. sulzeri. Family Hyaenodontidae Leidy 1869 possesses a protocone which is more individualised and located Genus Hyainailourus Biedermann 1863 further to the rear than in the molar of P. napakensis. and its Species Hyainailourus sulzeri Biedermann 1863 external wall, even though it is more rectilinear than in the European form, does not attain the almost flat profile seen in P. Material: AD 375"94. fragment of right maxilla with unworn napakensis. In addition, the parastyle of the Arrisdrift molar is M1 (measurements: L(Length)=35.2 mm. W(Width)=23 mm), clearly more developed than in P. napakensis, a further figure 2. feature that allies it with H. sulzeri. 28 J. Morales et al. Sf. r* _éS-Sîë ¦v -35- ÏÏÀ\ K&. s^*<_- m i #.-;,-: MSC_-=* '-¦ & A u; 0 10 20 30 mm *i»> ü^ -Ä*v -»¦ :/_ r- .x P 5£ *¦¦ S3»- B o S C 10 20 30 mm Fig. .v AD 135. holotype mandible of Ysengrinia ginsburgi sp. nov. A. buccal views B. lingual view. C. occlusal view of cheek teeth. New carnivores from the Miocene of Namibia 29 Suborder Fissipeda Blumenbach 1791 jsT' Family Amphicyonidae Trouessart 1885 __ Genus Ysengrinia Ginsburg 1966a .-- > Species Ysengrinia ginsburgi sp. nov. Previous identification: Amphicyon cf. steinheimensis NS (Hendey 1978) O Holotype: AD 133. left mandible, figure 3. Type locality: Arrisdrift. Namibia. Age: Basal Middle Miocene. Faunal Set P lila (Pickford 1981) (=MN04a. Mein 1990). Derivatio nominis: In honour of Dr Leonard Ginsburg. 10 20 30 mm. Diagnosis Ysengrinia of large size: Mi larger than M:: metaconid of Mi Fig. 4. AD 604'94. maxilla with P5 M1 of Ysengrinia ginsburgi. sp. nov. Occlusal view. reduced: Paraconid of M: lost: Protocone of P4 reduced. Differential diagnosis: Y. ginsburgi differs from Y. gerandi- ana (Viret 1929: Kuss 1965; Ginsburg 1966a) and from Y. valentiana (Belinchon & Morales 1989) by its larger size. It differs from Y. gerandiana. which is better known than Y. valentiana (L=20.5 mm. W=29 mm); M: (L=14 mm. W=26 mm). This by the greater reduction of the Mi, the loss of the specimen enables us to infer than the M2 is rather large. paraconid of M:, and the larger size of Mi with respect to Mi. Holotype AD 133 (fig. 3 a-c) is a left mandible with broken ascending ramus. The symphysis is extensive with a rugose surface. The horizontal ramus is high (the height at the anterior Description margin of P3 is 32 mm and below Mi is 38.5 mm). Two foramina AD 604'94 is a right maxilla with P'-M1 and a single alveolus occur in the mandible, one level with the gap between Pi for the anterior root of M: (Fig. 4). A small diastema occurs and P:. the other below the P-,. between P3 and P4. The infraorbital foramen is located above The canine (L=15.7 mm. W=10 mm) possesses a clearly the gap between P' and P4.