Coprolites from the Bridger Formation of Wyoming, their composition and microoerganisms

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Abstract
Well preserved mammalian and reptilian coprolites found in parts of the Eocene Bridger formation in the Bridger Basin of Wyoming contain silicified bacteria closely resembling the intestinal saprophytes of living animals. One of the mammalian coprolites, inferred to have been produced either by a carnivore or an omnivore, contains, in addition, an abundance of free-living fresh water algae (principally small desmids). The small desmid cells are extraordinarily well preserved. Internal structures such as pyrenoids, nuclei, and somewhat shrunken chloroplasts have been preserved. Dividing cells, 2 pairs of conjugating cells, zygospores?, and one monstrosity were found. In addition to the desmids there are 2 other spp. of Chlorophyceae and one flagellate alga, together with minute forms that may also be flagellate algae. Systematic descriptions of 6 microorganisms are given and 3 new species are proposed the bacterium, Escherichia bridgerana, the chlorococcale, Closteridium bulliforme, and the desmid, Staurastrum interoxenum. These free-living algae and a few ostracodes were probably imbibed by the animal in drinking water. The feces presumably fell on dry ground and were soon covered by volcanic ash which yielded siliceous waters to silicify the microorganisms. The presence of large numbers of desmids suggests that the animal drank from a pool of acid swamp water.

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