Opportunistic exploitation of dinosaur dung: fossil snails in coprolites from the Upper Cretaceous Two Medicine Formation of Montana

Multiple associations of fossil snails with dinosaur coprolites demonstrate that snails and dinosaurs not only shared ancient habitats but were trophically linked via dinosaur dung. Over 130 fossil snails representing at least seven different taxa have been found on or within herbivorous dinosaur coprolites from the Upper Cretaceous Two Medicine Formation of Montana. The terrestrial snail Megomphix is the most common taxon, but three other terrestrial taxa (Prograngerella, Hendersonia and Polygyrella) and three aquatic snails (Lioplacodes, ?Viviparus and a physid) also occur in coprolites. At least 46% of the shells in the faeces are whole or nearly so, indicating that most (if not all) of the snails were not ingested by dinosaurs, but were post‐depositional visitors to the dung pats. The sizeable, moist and microbially enriched dinosaur faeces would have provided both food and roosting sites for the ancient snails, and the large number of snail–coprolite associations reflect recurring, opportunistic exploitation of dung. The terrestrial taxa in the coprolites suggest that this Late Cretaceous locality included sufficiently moist detrital or vegetative cover for snails when dinosaur dung was not present. The aquatic snails probably entered the faeces during flood events. Dinosaur dung would have provided an abundant but patchy influx of resources that was probably seasonally available in the ancient environment.     

Phytopathology in fossil plants: New data,questions of classification

Examples of damages in fossil plants revealed using electron microscopy are considered. The formal classification of these damages is discussed.     

Applying modern analogs to understand the pollen content of coprolites

Most scientists working with coprolites from archaeological contexts assume that human fecal specimens reflect the mixing of the pollen ingested during the period in which the contribution to the coprolite, 19 to 37.5 h, was ingested, that the amount of pollen in a fecal sample directly reflects the amount of pollen originally ingested during that interval, and that differences between the amounts of pollen in different fecal specimens reflect differences in the quantities of pollen ingested at different times. These assumptions were tested and found wanting in an experiment in which two persons sequentially ate separate quantities of 15 pollen types in meals over a four-day interval. The pollen was retrieved and analyzed from feces produced during those four days and five days of subsequent fecal production. Pollen ingested first appeared in relatively small amounts, usually the day after it was ingested. Its concentration per gram of sample then increased rapidly and remained high over a one to three day interval relative to the amounts in previous and subsequent fecal specimens deposited. When pollen concentrations declined some pollen was retained in the gastrointestinal system and much lower concentrations per gram of sample of each type continued to appear in fecal samples for several days. These relatively low pollen concentrations appeared in fecal samples approximately twice as often as did higher concentrations. Our results indicate that comparatively high pollen concentrations can be used to determine that a given pollen type was ingested, but comparisons between pollen concentrations of the same pollen type in different fecal specimens or between different pollen types in the same fecal specimen, cannot be used to determine whether different amounts of pollen were ingested, or what was the relative amount of each ingested. Because pollen concentrations per gram of sample varied widely with time since ingestion, percentages of given pollen types did not occur in predictable patterns and could actually increase as the concentration of the pollen type decreases. Hence, percentages should not be used in coprolite pollen analysis. The experimental results also suggest that variations in the pollen content of different portions of a coprolite are meaningful only in terms of the overall pattern of a sequential group of coprolites.     

The steroids of 2000-year-old human coprolites.

Six samples of human coprolites, some more than 2,000 years old, were analyzed for fecal steroid composition. Despite this very lengthy period of storage, the fecal steroids of coprolites were remarkably similar to those of stool samples collected today. The sterol nucleus was clearly rather stable under the dry environmental conditions of the Nevada Caves. The steroid content (microgram/g dried weight) of coprolite was low in comparison to that of modern man. The bile acid/cholesterol and plant sterol/cholesterol ratios of the coprolite, however, were similar to these ratios of the stools of modern man. In the six coprolites, an average 73% of the neutral steroids was digitonin-precipitable. This precipitate was composed of cholesterol and three plant sterols (campesterol, stigmasterol, and beta-sitosterol) and their bacteria-modified products. A portion of the neutral steroids had been converted to products tentatively identified as epimers of these steroids. Individual bile acids were identified in the coprolite. The bile acid composition of the coprolite was similar to that of the stool of modern man.