A Revision of Late Oligocene Associations of Small Mammals from the Aral Formation (Kazakhstan) in the National Museum of Georgia, Tbilissi
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Palaeodiversity 2: 343–377; Stuttgart, 30.12.2009. 343 A revision of Late Oligocene associations of small mammals from the Aral Formation (Kazakhstan) in the National Museum of Georgia, Tbilissi OLEG G. BENDUKIDZE , HANS DE BRUIJN & LARS W. VAN DEN HOEK OSTENDE Abstract The taxonomy and age of the small mammals from the type area of the Aral Formation have been disputed ever since the first specimens from Akespe were published by ARGYROPULO in 1939. The material from Altyn Schokysu, Sayaken, Akespe and Akotau dicussed below was collected by the first author (OGB) during the second half of the twentieth century and published in Russian in 1993. The revision of the fauna from the Aral Formation suggests a biostratigraphical correlation with the radiometrically calibrated Oligocene zone C/C` in Mongolia defined by DAXNER -HÖCK . Hence the original assignment of the Aral fauna to the Late Oligocene (Tabenbulukian) is considered to be correct. K e y w o r d s : Kazakhstan, Rodents, Lagomorphs, Insectivores, Oligocene. Zusammenfassung Die Taxonomie und das Alter der Kleinsäuger aus dem Typusgebiet der Aral-Formation werden seit der Be- schreibung der ersten Funde von Akespe durch ARGYROPULO (1939) diskutiert. Das hier besprochene Material von Altyn Schokysu, Sayaken, Akespe und Akotau wurde vom Erstautor (OGB) während der zweiten Hälfte des zwan- zigsten Jahrhunderts gesammelt und 1993 in Russisch publiziert. Die Revision der Fauna der Aral-Formation deutet auf eine biostratigraphische Korrelierung mit der radiometrisch kalibrierten und von DAXNER -HÖCK definierten Oligozän-Zone C/C’ in der Mongolei hin. Daher wird die ursprünglich angenommene Einstufung in das späte Oli- gozän (Tabenbulukium) als richtig betrachtet. Contents 1. Introduction . 343 2. Methods . 344 3. Systematic paleontology . 345 Erinaceomorpha GREGORY , 1910 . 345 Erinaceidae FISC H ER , 1814. .345 Soricomorpha GREGORY , 1910. 345 Talpidae FISC H ER , 1814 . 345 Heterosoricidae VIRET & ZAP F E , 1951. 346 Lagomorpha BRANDT , 1855. 347 Leporidae FISC H ER VON WALD H EIM , 1817. 347 Ochotonidae TH OMAS , 1897. 349 Rodentia BO W DIC H , 1821. 349 Castoridae HEMPRIC H , 1820. 349 Ctenodactylidae GERVAIS , 1853. 351 Dipodidae FISC H ER VON WALD H EIM , 1817. 352 Muridae ILLIGER , 1811. 352 4. List of the small mammals of the Aral local fauna represented in the BENDUKIDZE collection. 356 5. The age of the assemblage. 356 6. References . 356 1. Introduction mammals from the type area of the Aral Formation have been the subject of a series of detailed studies by LOPATIN , The decision to give an annotated series of figures of who greatly enlarged the collections from Altyn Schokysu the specimens from the North Aral area in western Ka- and increased the knowledge of its interesting fauna (LO- zakhstan described and discussed in the monograph of PATIN 1996, 1998, 1999a, 1999b, 2003, 2004). However, it BENDUKIDZE (1993) was taken shortly after the interna- is of interest to figure and update the identification of the tional meeting on “The Oligo/Miocene boundary in Ka- specimens in the BENDUKIDZE collection because it con- zakhstan,” Aktyubinsk, 1994. Since that time the small tains many types, and to discuss the age of the fauna in the 344 PALAEODIVERSITY 2, 2009 collecting bias because a sample taken by D. KÄLIN, T. BOLLIGER, G. DAXNER-HÖCK and the second author (HdB) from level 2 at Altyn Schokysu in 1994 (n = about 400) contained only about 5 % of the larger rodent species that dominate the BENDUKIDZE collection. For the geographical position of the localities and detailed descriptions the reader is referred to LOPATIN (2004), BENDUKIDZE (1993) and Fig. 1. Figures of the more interesting specimens as well as updated identifications will be given below. The material discussed below is housed in the collec- tions of the Institute of Paleobiology, Georgian National Museum, Tbilissi. Acknowledgements We thank Mr. W. DEN HARTOG for making the SEM photo- graphs and Mr. J. LUTEIJN for retouching these photographs. Mr. F. TRAPPENBURG made the plates and Mr. R. RABBERS made the sketch map of the study area (both Geomedia Department, Utrecht). Mr. H. BRINKERINK made the casts that served as the basis for the photographs, so covering the original specimens with gold could be avoided. Ms. J. RICHTER assisted in finding literature references for supraspecific taxa. The expert advice of our colleagues MARGUERITE HUGUENEY (Lyon), MARY R. DAWSON (Pittsburgh) and MARGARITA ERBAJEVA (Ulan Ude) on the Castoridae respectively the Lagomorpha in our collection is much appreciated. The second author (HdB) gratefully acknowledges his son in law, MARC TER HAAR for translating some Russian texts and KEES HORDIJK for reading the Fig. 1. Sketch map of Kazakhstan and the study area showing manuscript critically. the geographical position of the localities that yielded the small GUDRUN DAXNER-HÖCK made an essential contribution to this mammals discussed below (modified after LOPATIN 2004). paper by showing her collection of rodents from the Valley of Lakes, Mongolia to the second author (HdB). light of new information on the, radiometrically calibrat- 2. Methods ed, fauna succession from the Valley of Lakes in Mongolia (DAXNER-HÖCK et al. 1997). Measurements of non-lagomorph teeth represent max- The associations of fossil small mammal remains from imal length × width of the occlusal surface and are given the North Aral area, collected by the first author (OGB) in 0.1 mm units unless indicated otherwise. The nomen- during the eighties of the last century (BENDUKIDZE 1993), clature of parts of the cheek teeth follows LÓPEZ-MARTÍNEZ can be divided into a Late Oligocene and a Miocene group (1977) for the lagomorphs and HUGUENEY (1999) for the on the basis of biostratigraphical criteria. The material castorids. Three measurements are given for the molari- from the localities from the Aral Formation (Fig. 1): Altyn form lower cheek teeth of lagomophs: the first applies to Schokysu (levels 1–4), Sayaken, Akespe and Akotau in- the length, the second to the width of the trigonid and the cluded in the first group will be discussed below. The col- third to the width over the talonid. lections from the four different fossiliferous levels in the The specimens on the plates are all figured as if they Altyn Schokysu escarpment that have been recognised by are from the left side. If the original is from the right side some authors are united into one local fauna, because they the relevant number has been underlined on the plate. come from lenses that are situated at considerable lateral The specimens from the northern Aral area housed in distances. Their relative stratigraphical position is there- the Institute of Paleobiology, Tbilissi carry a locality as fore not clear. For a discussion of the litho- and chrono- well as a specimen number. Nine stands for the locality logical position of the Aral Formation we refer to LUCAS et Sayaken, eleven for Akespe, fifteen for Altyn Schokysu al. (1998). and sixteen for Akotau. The collection studied seems to suffer from a strong BENDUKIDZE ET AL., OLIGOCENE MAMMALS FROM KAZAKHSTAN 345 3. Systematic paleontology tion (LOPATIN 1999a). The material therefore clearly repre- sents a different and possibly new species. As the taxono- Erinaceomorpha GREGORY, 1910 my of Amphechinus is in mayhem as it is, we refrain from Erinaceidae FISCHER, 1814 describing yet another species based on scanty material. Galericinae POMEL, 1848 Galericinae gen. et sp. indet. BOHLIN, Pl. 1, Fig. 1 Amphechinus cf. minimus ( 1942) Pl. 1, Figs. 6–8 Locality: Altyn Schokysu. BENDUKIDZE Material and measurements: 1993 Amphechinus minimus. – , p. 10, pl. 2, figs. 1–4. No. Fig. Tooth Length × Width 1999 Amphechinus microdus LOPATIN, sp. nov. – LOPATIN, pp. 15/1 Pl. 1, Fig. 1 m1 sin. 27.1 × 18.4 185–187, fig. 3. [1999a] 2004 Amphechinus microdus LOPATIN, 1999. – LOPATIN, pp. S323–S234, fig. 8, pl. 6, figs. 6–8. R e m a r k s . – The presence of galericines in the fauna had already been noted by LOPATIN (2004), who assigned a L o c a l i t y : Altyn Schokysu. Material and measurements: p4 to Galerix sp. However, the specimen he illustrates seems to be an m3 of Amphechinus sp., fitting well in No. Fig. Tooth Length × Width 15/7 Pl. 1, Fig. 6 M1 sin. – × – morphology and dimensions with the m3 in the BEN- Fragment of a man- DUKIDZE collection. Nevertheless, one m1 in our collection 15/8 Pl. 1, Fig. 8 dible sin. with m2 18.2 × 12.6 strongly resembles Galerix in having a conical paraconid m3 7.8 × 4.2 at the end of a long paralophid. Galerix has its first occur- 15/8a Pl. 1, Fig. 7 m1 sin. 22.8 × 13.1 rence in the uppermost Oligocene of Anatolia (DE BRUIJN et al. 1992). Metrically, our m1 falls just outside the range of R e m a r k s . – The smaller of the two Amphechinus VAN DEN HOEK the oldest species of Galerix, G. saratji species from Altyn Schokysu was originally described as OSTENDE, 1992 , being slightly larger. Since we just have Amphechinus minimus by BENDUKIDZE (1993). LOPATIN one m1, and the Oligocene history of the Asian galericines (1999a) named the smaller species A. microdus. This new is poorly known, this tooth cannot be identified beyond species was distinguished mainly on the basis of the stron- the subfamily level. ger reduction of the m3 relative to the m2 (40 % vs 55 %). Although this feature is also observed in our material we believe that, without knowing the variation of this charac- F , 1814 Erinaceinae ISCHER ter, it is insufficient to warrant distinction at the species A Amphechinus YMARD, 1850 level. Therefore, we maintain the original classification as A. minimus. Amphechinus sp. Pl. 1, Figs. 2–5 2004 Galerix sp. – LOPATIN, pp.