CRETACEOUS BRYOZOANS AND THE OLD WEST

Cretaceous faunas, known for dinosaurs and mosasaurs, include inconspicuous Bryozoa equally important for understanding ancient ecosystems. But, bryozoans are rare and depauperate in deposits of the Western Interior Seaway, unlike Europe. To understand this distributional anomaly better, we compiled a list of Cretaceous bryozoan occurrences throughout the Western Interior of the U.S. and Canada. Coincidentally, a surprisingly high proportion of these are close to iconic Old West historical sites.

The bryozoans span Albian—Maestrichtian time, northern to southern borders of the U.S., and represent deep off-shore muddy bottoms to shallow near-shore shell beds. Genera reported include cheilostomes (Conopeum, Dysnoetopora, Marginaria, Membranipora, Pyripora, Solenophragma, Villicharixa, Wilbertopora), ctenostomes (Orbignyopora, Pierrella), and cyclostomes (Ceriopora?, Idmonea, Oncousoecia, Proboscina, Pustulopora, Reptomulticava), most of the Western Interior bryofauna. By contrast, deposits of this age in Europe contain 500+ genera, while 77 are recorded from just the later Cretaceous (Campanian—Maestrichtian) in the U.S. Gulf + Atlantic coastal plains.

Old West sites close to Cretaceous bryozoan localities include, from N to S: Missouri River (Lewis & Clark Expedition 1804-06; Fort Peck, Shell Buttes, Chamberlain); Deadwood frontier town with Wild Bill Hickok and Calamity Jane 1876, and Custer’s expedition to the Black Hills 1874 (Deadwood); Hole-in-the-Wall hideout of Butch Cassidy and Sundance Kid late 1800’s, and Teapot Dome scandal 1923 (Shannon); first trans-continental railroad 1869 (Laramie); Dodge City with Wyatt Earp and Bat Masterson 1870’s (Carlile); Columbus target of Pancho Villa’s cross-border raid 1916 (Smeltertown); Tombstone with OK Corral gunfight Wyatt Earp & Doc Holliday vs Clantons 1881 (Mural).

While it would be romantic to view the bryozoans as psychic cryptic bystanders awaiting future events, reality is much more prosaic. The Old West developed in a vast landscape traversed by few transportation routes, which concentrated much of the early activity there into relatively few locations. Geologists initially exploring the West followed these arteries too, and so made many of their observations and collections near what were to become historic locations.