GEOLOGICA BELGICA (2013) 16/4: 236-244 New mammals from the marine Selandian of Maret, Belgium, and their implications for the age of the Paleocene continental deposits of Walbeek, Germany Eric DE BAST, Etienne STEURBAUT & Thierry SMITH O.D. Earth and History ofLife, Royal Belgian Institute for Natural Sciences, Rue lautier 29, 1000 Brussels, Belgium ABSTRACT. The early to middle Selandian fossiliferous Orp Sand Member of the Heers Fonnation in Belgium has regularly been excavated at its type-locality Maret for its rich and diversified selachian fauna. Among the abundant vertebrate remains, extremely rare mammal specimens have been found. Three isolated teeth have been published previously, all with uncertain affinities. The purpose of this study is to present new specimens from the same deposits, including a small well-preserved dentary of an adapisoriculid attributable to “Afrodon” germanicus, a fragmentary upper molar, referred to Berndestes sp., and a premolar of a large arctocyonid. Among the previous specimens we identified Arctocyonides cf. weigeld. The adapisoriculid dentary offers new clues that allow transferring “Afrodon’ germanicus to tile genus Bustylus. The five mammal taxa from Maret indicate an age intermediate between reference-levels MP1-5 of Hainin, Belgium and MP6 of Cemay, France and present the greatest correlation with the rich Walbeek fauna in Germany. The deposits from Walbeek were usually thought to be slightly older than the late Thanetian deposits of Cemay. We infer here that the age of Walbeek is likely to be Selandian. The strong differences observed between Hainin on the one hand, and Walbeek and Cemay on tile other hand, document a dispersal event from North America to Europe around the Danian-Selandian boundary. KEYWORDS: Orp Sand Member, Heers Formation, Biostratigraphy, Paleobiogeography, Adapisoriculidae 1. Introduction Herman & Sigé, 1975). Unfortunately, tile specimens figured by Herman and Sigé ( 1975 ) were not deposited in a public institution or even numbered, and seem to be lost. However, casts of tile Paleocene continental deposits of northwestern Europe are specimens were recovered in the collection of tile University of extremely discontinuous, both in space and time. This is essentially Montpellier; these casts are now deposited at tile RBINS with because a large part of Europe’s surface was flooded by shallow type and figured specimen numbers. These previously mentioned epicontinental seas and the remaining continental sedimentary specimens, together with tile new Orp Sand records, including archive was largely destroyed by the many subsequent vast marine an adapisoriculid jaw, are discussed here and compared to other transgressions (Vinken, 1988; Pomerol, 1989; Steurbaut, 1998). Paleocene mammal faunas of Europe. The stratigraphie position and age of these continental deposits are particularly difficult to establish, essentially because of the lack of suitable bio stratigraphie markers. This prevents easy and Institutional abbreviations— IRSNB, Royal Belgian Institute accurate correlation between the terrestrial and marine records of Natural Sciences, Brussels, Belgium; MLU Wa, Walbeek, and with the Geological Time Scale. The often short time span Institut für Geologische Wissenschaften und Geiseltalmuseum, covering many of the continental strata and the scarcity of well- Martin-Luther-Universität Halle-Wittenberg, Gennany. studied localities are not helping either. Palynomorphs provide one of the rare keys for disentangling the continental-marine 2. The Maret site and its spatial and temporal setting relationships (Steurbaut et al., 2003). Another key that helps in constraining the age estimates of continental faunas are remains The fossiliferous outcrops of Maret, a hamlet of the village Orp- of continental vertebrates found in marine deposits (Smitii & le-Grand, about halfway between tile towns of Leuven and Liège, Smith, 2003; Smith et al., 2004). have been intermittently but intensively investigated since the end of the 19,hcentury (see Herman & Sigé, 1975 for an overview). Among Paleocene MP levels (international mammal The mammal remains studied here have been collected on reference-levels for the European Paleogene, see Schmidt-Kittler, both sides of tile Maret railway track, and at different spots in 1987 and BiochroM’97, 1997), only MP6, which corresponds tile over 100 m wide exposure zones (coordinates 50°42’40”N, to the upper Thanetian, has been definitely identified based on 4°59’59”E). Herman & Sigé (1975) sampled on the North and tile mammal fauna from Cemay. The fauna of Hainin (Mons Basin, Belgium) is the only European fauna that is clearly older than the typical Cemaysian MP6 level. It is therefore the only representative for the interval M PI-5, which needs to be redefined and subdivided in the future when new intermediate mammal faunas are found. In his study on the Paleocene mammals of Europe, Russell (1964) noticed that many taxa of tile continental fauna of Walbeek (Germany) showed slightly more primitive features than similar taxa from Cemay. Walbeek ^?\M aret was later suggested to represent MP?5 (Schmidt-Kittler, 1987, BiochroM’97, 1997; Gheerbrant et al., 1999; Smith & Smitii, 2003), but tile aberrant mammal assemblage coupled with the lack of stratigraphie control prevented scientists from considering BELGIUM Walbeek as a reference-level (Schmidt-Kittler, 1987). New fossil terrestrial mammal specimens have recently FRANCE been collected from tile Orp Sand Member at Maret, the type- locality of this stratigraphie unit (Steurbaut, 1998) (Fig. 1). At this particular site, these Mid-Paleocene sands are renowned for c. 60.0 Ma - Selandian their rich marine selachian fauna, and they represent tile locus | . Heers Formation typicus and stratum typicum of one genus and several species of E = erosion, influx Cretaceous coccoliths sharks (Herman, 1973, 1977; Cappetta & Nolf, 2005). Extremely E.S., 2008 ---------- isopachs (equidistance 20m) rare terrestrial vertebrate remains have been found in association with the marine vertebrates (Dollo, 1890; Herman, 1973), Figure 1.Current distribution of the Heers Formation in Belgium with among which are a few mammal specimens (Quinet et al., 1971; thickness estimates and location of the fossiliferous site of Maret. S e l a n d ia n m a m m a l s f r o m B e l g iu m 237 At Maret, the Orp Sands, of which only the upper 4 m are The Maret outcrop section in Central Belgiumexposed, consist of a heterogeneous complex of essentially sandy sediments, with intermittent influxes of whitish marl m material, sometimes forming thin beds, but mostly restricted to * I * I * i centimetric to decimetric large irregular marl lumps (Fig. 2). The 1*1* i * at high carbonate content of these marls is due to the presence of blocky siliceous whitish i= reworked Cretaceous coccoliths (Fig. 1). Sedimentation took 1*1 * * I limestone, glauconitic o H O STT jT-r ^ r i H t/> place in a shallow marine context, with temporary estuarine 0 influences, at the edge of the continent, with exposed chalk strata *1*1*1 * I * ) E 25 (cliffs? Bless & Fernández-Narvaiza, 1996, fig. 36; Dreesen et highly glauconitic * • . il al., 1998). This is evidenced by the presence of bioturbated and c T O 0 horizontally stratified sands and thin marl beds, pointing to rather more sandy O towards the base c calm sedimentation conditions, and the reworked marl lumps, the -a-b-C gravel bed concentrations of glauconite and the channeling, reflecting high- _ . V I ~S energy input. u i i I g IO TT7 grey marly stonebed GM The three other isolated mammal teeth from Maret were encountered in the basal gravel of the Lincent Limestone Member. fine stratified sand This siliceous limestone to calcareous sandstone unit, overlying a thin basal gravel, represents the lower Member of the Hamiut Formation. In agreement with its attribution to the lower part of biotubated clayey sand with 4 - nannofossil zone NP8, it belongs to the lower middle Thanetian. //. & large marl chunks O The basal gravel layer in Maret has yielded a rich selachian fauna. Or7* ? , 0 -Q In between the Orp Sand Member and the Lincent Member intercalation of stratified E occurs a whitish crumbly marly chalk, the Gelinden Marl Member, sand and marl layers 0 i ^ i y i ^ i ^ i et the thickness of which is reduced to less than 1 m at Maret. The age o estimate of the Gelinden Marl Member is mid to late Selandian several sets of glauconitic“D LL C on the basis of the calcareous nannofossil (upper NP4-NP5) and sand 0 co dinoflagellate associations (Zone 3 of Heihnann-Clausen (1985), co Qt Q_ recorded in the upper part of the Æbelo Fonnation and base of the S bioturbated clayey sand LU LU Holmehus Formation in Denmark (Sheldon et al., 2012). biotubated clayey sand X with large marl chunks 3. Systematic Palaeontology bioturbated clayey sand Class Mammalia Linnaeus, 1758 GM = Gelinden Marl Member ES Grandorder Euarchonta? Waddell, Okada, and Hasegawa, 1999 M = location of mammal specimens 2013 Family Adapisoriculidae Van Valen, 1967 Genus Bustylus Gheerbrant & Russell, 1991 Figure 2. Lithology and lithostratigraphic interpretation of the Maret Type species: Bnstyliis cemaysi Gheerbrant & Russell, 1991 outcrop (logged on the southern side of the railtrack on June 16th 1992), with location of the mammal finds: a. Herman, 1973 and Herman & Sigé, Bustylus germanicus (Russell, 1964) comb. nov. 1974; b. Quinet et al., 1971; c. this paper. (Fig. 3C) Referred specimens: IRSNB M2017, left dentary with p3-m3 South sides of the track, all others (Quinet et al., 1971; this paper) in place, from the Orp Sand Member of the Heers Fonnation at only on the South side (see Herman & Sigé, 1975 for a detailed Maret. map of tile area). This southern site, last re-excavated in the early 1990s, was logged in 1992 (Fig. 2). Measurements: p4: L = 1,41 nun, 1 = 0,67 nun; ml: L = 1,35 nun, Of tile six mammal specimens discussed here, three 1 = 0,74 nun; m2: L = 1,31 nun, 1 = 0,75 nun; m3: L = 1,27 nun, come from the Orp Sand Member, which at Maret, as nearly 1 = 0,70 mm.