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

marine vertebrate fauna of the Leithakalk in St. Margarethen. The majority of these fossils consists of inarticulated remains and appears to be randomly distributed in the limestone. Only few articulated dolphin skeleton fragments are known from St. Margarethen, the most complete one being Ob-258. Other Leithakalk occurrences (e. g. in Mátraszőlős, North Hungary) show a similar vertebrate fossil composition and pattern, but have never yielded any articulated skeleton fragments (KORDOS 1978, 1985, KORDOS & SOLT 1984). In his taxonomic paper PAPP (1905) described the condition of the skeleton in detail. Here we restrict ourselves to a brief description, emphasising aspects that are important for the understanding of the taphonomic processes. The skeleton is almost complete with exception of both missing ends (as discussed earlier)(Plate I: A). The mandibles are attached to the skull and the right tympanic bone lies approximately on its original place. Although the preserved tympanic bone is fragmentary, its surfaces do not show any signs of weathering or rounding. The période bone is not exposed at present, but further preparation may prove its presence. The preserved teeth are difficult to count, it is nevertheless clear that most of the teeth are in situ. The brain case is highly compressed, roughly dorsoventrally, as concluded from the dorsally exposed tympanic bone. PAPP (1905) asserted that a hyal bone could also be seen on the smaller block. The present authors cannot confirm the existence of this bone. All seven cervical and all thoracic vertebrae are in their original position. There is, however, one thoracic vertebra (the ninth, according to PAPP 1905) that is slightly hanging out from the arch of the vertebral column. On the larger block, 6 (7?) lumbar vertebrae can bee seen in articular position. The chest is collapsed and the contacts between the preserved ca. 8 ribs and the corresponding thoracic vertebrae are difficult to interpret. This situation may be a result of the distortions of the ribs, or simply due to the fact that the vertebral processes are very fragmented. The right scapula and flipper bones (humerus, radius, ulna, carpals, metacarpals and some phalanges of three fingers) are preserved on the larger rock slab (Plate I: A). All flipper bones are in articular position, but the forelimb and the scapula as a whole are slighdy shifted cranioventrally. Although the humerus can only be seen in longitudinal section, it is clear that the proximal epiphysis was completely fused to the shaft in the living animal. Likewise, fusion of vertebral epiphyses to centra was completed in all preserved regions of the vertebral column. In recent Stene/Ia, fusion of the humerus is completed by the onset of sexual maturity (PERRIN 1975). Fusion of vertebral epiphyses to centra progresses from the cephalic and caudal ends of the vertebral column. Fusion of thoracic and lumbar vertebrae is not completed until physical maturity is reached (PERRIN 1975). If the ontogeny of Heterodelphis was comparable to that of modern spotted dolphins, then we can assume that Ob-258 was physically mature by its death. The X-ray failed to confirm the presence of any bone elements inside the limestone blocks. Few other fossils were found in close association with the H. leiodontus skeleton. In the upper block, cross-section of a single coral polyp was found. One shell of Pecten (Chlawys) elegáns (PAPP 1905) is situated in the vicinity of the mandibles. Another bivalve shell is located next to the last rib. Among the ribs, concentration of bony fish remains, vertebrae, fin rays and one fish tooth can be seen (figure 7 in PAPP 1905). According to PAPP, the latter belonged to Chrysophrys (=Sparus, Sparidae, Perciformes). Found in the posterior area of the chest, this concentration is interpreted as a food bolus (see also PAPP 1905). No traces of encrusting fauna were found on the skeleton. Neither tooth marks nor other evidence of predator or scavenger action could be identified on the bones. This, however, can be misleading since large parts of the skeleton were cut longitudinally (as discussed earlier). Thus, the majority of the bones exhibits their inner structure only, and not the bony surfaces. In conclusion, all bones are roughly in articular position. Minor distortions of the preserved ribs and slight dislocation of the right flipper are thought to be due to compression during burial. The same might be true for the vertebral column that exhibits a marked breakage between the 8

th and 9

th thoracic (or between the last thoracic and first lumbar) vertebrae. The embedding limestone layers Macroscopic observations — The embedding Leithakalk block consists of porous calcarenite. The limited dimensions of the rock sample do not allow the recognition of larger sedimentary structures, e. g. cross stratification. There is a notable grain-size contrast between the lower part of the larger slab and the rest. The boundary of these two rock types is indicated with dashed line in Plate I: B. In the lower part of the thicker and larger rock slab the grains and the open pores are definitely smaller than in the upper part of the slab and in the whole thinner slab. The latter parts consist of significandy coarser grains and contain more and larger pores. Because of the noticeable grain-size and porosity contrast, it is highly possible that here we are dealing with a bedding surface between the top, finer section of the underlying layer and the coarser base of the next layer. The dolphin skeleton lies between the two blocks,