Taphonomy of microvertebrate fossil assemblages

Abstract

Two principal modes of origin have been suggested for microvertebrate deposits -1) the scatological hypothesis, and 2) the fluvial hypothesis. These two hypotheses were tested by 1) examining remains found in modern carnivore feces and owl pellets, 2) experimentally determining the susceptibility of various skeletal elements of small mammals to stream sorting, and 3) analyzing microvertebrate fossil assemblages.The abraded rather than sharply broken condition of the fossil bone and the frequency of preservation of individual elements most closely resembled that of the bone that had been experimentally abraded rather than bone from predator scats.Although the hydraulic properties of skeletal elements are dependent to some extent on shape, empirically derived settling curves show that the settling velocity of mammal bones is strongly size dependent. As predicted from the curves, it was found that the sediment particle size of the fossil bearing deposits had equivalent hydraulic properties to the bone contained in the sediment. It was concluded that the accumulations investigated were of alluvial origin.The paleoecologic applications of alluvially sorted microvertebrate fossil accumulations are limited because the effects of stream flow can markedly alter the composition and relative representation of members of the fauna. Korth-Microvertebrate Taphonomy 243Korth, William W. 1979. "Taphonomy of microvertebrate fossil assemblages."

Taphonomy of a late Cretaceous mammal-bearing microvertebrate assemblage from the Deccan inter-trappean beds of Naskal, peninsular India

“…The minimum number of individuals or MNI (Shotwell, 1955) for amphibians and mammals were calculated by counting the most frequent elements, taking into consideration the morphology of the elements, colour variation, and size of the elements. Relative representation (RR), the proportion of elements present relative to the expected number given MNI (RR=NISP observed/NISP expected elements) (Wolff, 1973;Korth, 1979) was calculated for these two groups in an attempt to compare these elements with Voorhies dispersal groups for hydraulic sorting.…”

“…In spite of many pioneering works on the taphonomy of megavertebrate fossils (Shotwell, 1955;Voorhies, 1969;Behrensmeyer, 1975Behrensmeyer, , 1988, very few studies have concentrated on the microvertebrate remains (Dodson, 1973;Mellett, 1974;Korth, 1979) in the past. Some workers (Dodson, 1973: Wolff, 1973Korth, 1979) have even cast doubt on their usefulness in the reconstruction of palaeocommunities because of the ease with which such elements are transported hydraulically or by predators.…”

“…In spite of many pioneering works on the taphonomy of megavertebrate fossils (Shotwell, 1955;Voorhies, 1969;Behrensmeyer, 1975Behrensmeyer, , 1988, very few studies have concentrated on the microvertebrate remains (Dodson, 1973;Mellett, 1974;Korth, 1979) in the past. Some workers (Dodson, 1973: Wolff, 1973Korth, 1979) have even cast doubt on their usefulness in the reconstruction of palaeocommunities because of the ease with which such elements are transported hydraulically or by predators. In the last 15 years, good qualitative works, stemming from the previous studies, have appeared and ascribed the origin of microvertebrate remains to avian (Mayhew, 1977;Dodson and Wexlar, 1979;Kusmer, 1990) or mammalian (Mellett, 1974;Andrews and Evans, 1983;Maas, 1985) predators or as a consequence of sorting and concentration by hydraulic forces (Dodson, 1973;Wolff, 1973;Korth, 1979;Wood et al, 1988: Eberth, 1990.…”

“…Some workers (Dodson, 1973: Wolff, 1973Korth, 1979) have even cast doubt on their usefulness in the reconstruction of palaeocommunities because of the ease with which such elements are transported hydraulically or by predators. In the last 15 years, good qualitative works, stemming from the previous studies, have appeared and ascribed the origin of microvertebrate remains to avian (Mayhew, 1977;Dodson and Wexlar, 1979;Kusmer, 1990) or mammalian (Mellett, 1974;Andrews and Evans, 1983;Maas, 1985) predators or as a consequence of sorting and concentration by hydraulic forces (Dodson, 1973;Wolff, 1973;Korth, 1979;Wood et al, 1988: Eberth, 1990. Irrespective of their nature, most of these studies are restricted to Neogene and Recent mammalian faunas ( Wolff', 1973;Behrensmeyer, 1978Behrensmeyer, , 1982Korth, 1979: Denys, 1985: Badgley, 1986Denys et al, 1987: Pratt, 1989: Kusmer, 1990) and very few workers have focused attention on older deposits (Dodson, 1971Winkler, 1983;Maas, 1985;Sander, 1987: Wood et al.…”

Revision of the Wind River faunas, early Eocene of central Wyoming. Part 2. Geologic setting

“…14). Korth (1979) suggested that small bone could be easily moved by very low currents of water competent to carry only the clay-sized fraction. Therefore, these bones would be sorted without being abraded.…”