Eocene Green River Crocodile Coprolite
Borealosuchus wilsoni (?) Coprolite
with Diplomystus
Green River Formation
Middle Eocene
Lincoln County, Wyoming
This specimen of coprolite from the Green River Formation is an exceptionally large example. Most coprolite seen in the formation represents various genera of fishes. On rare occasion a large coprolite can be found that most probably represents crocodiles which are the largest swimming resident of the middle Eocene lakes. Borealosuchus (Brochu) skeletons of the size required to produce a coprolite of this size are known by notable specimens in the Fossil Butte Member. This specimen was originally collected and prepared by Carl Ulrich and has his original certificate attached to the back of the framed specimen. This example also contains a finely preserved skeleton of Diplomystus. The slab is 16 inches by 14.5 inches and has an attractive frame. The coprolite is 14.5 cm and the fish skeleton is 7 cm.
Borealosuchus (meaning boreal crocodile) is an extinct genus of crocodylians that lived from the Late Cretaceous to the Eocene in North America. It was named by Chris Brochu in 1997 for several species that had been assigned to Leidyosuchus. The species assigned to it are: B. sternbergii, the type species, from the Maastrichtian (Late Cretaceous) of Colorado, Montana, North Dakota, South Dakota, and Wyoming; B. acutidentatus, from the Paleocene of Saskatchewan; B. formidabilis, from the Paleocene of North Dakota; B. griffithi, from the Paleocene of Alberta; and B. wilsoni, from the Eocene of Wyoming. B. formidabilis is particularly well-known, represented by the remains of many individuals from the Wannagan Creek site in North Dakota.
Diplomystus is an extinct genus of freshwater clupeomorph fish distantly related to modern-day extant herrings, alewives, and sardines. The genus was first named and described by Edward Drinker Cope in 1877. D. dentatus (Cope, 1877) is well known from lower Eocene deposits from the Green River Formation in Wyoming. Specimens range from larval size to 65 cm and are commonly found in close association with the extinct herring Knightia sp. The Green River Formation is the remnant of a large lake whose mud would eventually be transformed into soft calcite-bearing shale.
$500