Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 19. 2001. (Budapest, 2001)

Taphonomy and palaeoecology of the holotype of Heterodelphis leiodontus PAPP, 1905 (Cetacea, Mammalia) from Szentmargita (St. Margarethen, Austria) by Emese KAZÁR & Zoltán LANTOS Abstract — Investigation of the type specimen of Heterodelphis leiodontus PAPP, 1905 and the embedding Leithakalk yielded a taphonomic model and a paleoenvironment reconstruction. Preservation of an articulated skeleton is exceptional for the Leithakalk. After death the studied specimen underwent rapid burial caused by sudden sediment redeposition, probably due to stormy water movements. The burial took place in a shallow, euphotic, nearshore marine environment. The sediment was coarse, calcareous sand composed mainly of red algal grains. We suppose that fragments of coralline algae have originated from maerl while other microfaunal elements have been transported from a sea-grass meadow community. Reefs were not present in the close vicinity. Keywords — Miocene, Badenian, Leithakalk, Paratethys, St. Margarethen (Austria), taphonomy, paleoecology, Odontoceti, Heterodelphis KAZÁR, E. & LANTOS, Z. (2001): Taphonomy and paleoecology of the holotype of Heterodelphis leiodontus PAPP, 1905 (Cetacea, Mammalia) from Szentmargita (St. Margarethen, Austria). — Fragmenta Palaeontologica Hungarica, 19: 51—60. Introduction The present paper addresses the taphonomy of a dolphin skeleton that is the holotype of the extinct species Heterodelphis leiodontus PAPP, 1905 and gives a reconstruction for the habitat the studied specimen lived in. The fossil skeleton in question is well-known and one of the most famous odontocete remains from the Miocene of Middle Europe (e.g. KELLOGG, 1927; MÜLLER, 1970). The skeleton was found in the Leithakalk (Leitha limestone, Rákos Formation in Hungary) of Szentmargita (= Szentmargitbánya, today: St. Margarethen) in the Rüster Bergland, close to the Leitha Gebirge (Leitha Mts., Burgenland, Austria) in 1880. The original description (PAPP, 1905) does not give us any clue to retrace the exact location where the fossil remains were excavated. Three quarries expose similar limestones to those preserved with the studied skeleton: the "Hummel" and Roman quarries are located on the north side of the road leading from St. Margarethen to Rust, the "Kummer" quarry is situated on the opposite side of the same road. The skeleton originates most probably from the Roman quarry (Figure 1, A), since limestone had already been exploited in this quarry by the time of the dolphin's discovery. DÜLLO (1983, Fig. 5; and Figure 1: B hereby) published a stratigraphie section from the "Hummel" quarry. This section is typical for the Leithakalk in the area. Since the stratigraphie column shows cyclic repetition of five different microfacies types, the origin of the limestone block that yielded the dolphin skeleton cannot be determined. According to DÜLLO (1983), the stratigraphically younger part of the section is characterised by caliche-like crusts and fine-laminated marls deposited in restricted lagonal environments. He also observed meniscus and dripstone cements referring to cementation in vadose environment due to early subaerial exposures of the carbonate sand succession. The primary marine cementation was weak, only thin micritic cement is present. A B Mari o m Figure 1 A: Map showing the locality where the type specimen of H. leiodontus was most probably found. B: Lithologie section from the Hummel quarry of St. Margarethen (redrawn after DuLLO, 1983). Original position of the limestone bed yielding Ob-258 cannot be determined in the section.