Wooster’s Fossil of the Week: A ptilodictyine bryozoan from the Silurian of Ohio

May 15th, 2015

Phaenopora superba Brassfield 585The fossil above was found by Luke Kosowatz (’17) on our Sedimentology & Stratigraphy class field trip last month. We were measuring and sampling the Brassfield Formation (Early Silurian, Llandovery) near Fairborn, Ohio, and Luke pulled this beauty out of the rubble. This limestone is full of echinoderms and corals, so this lonely bryozoan was immediately a star.
Peela 050815This is the specimen that we sectioned and made an acetate peel from last month. The interior view, shown above, was critical to its identification. This peel was made perpendicular to the surface. It shows that the bryozoan is bifoliate, meaning it has two sides with zooids (the filter-feeding bryozoan polypides) and stood upright on the seafloor like a fan or leaf. Both sides had the characteristic bumps called monticules.
Phaenopora closerThe next critical view is this close-up of a slightly weathered surface of the bryozoan. It shows a regular arrangement of the larger zooecia (autozooecia) with two smaller zoooecia (metazooecia) between each pair. These clues enabled my friend Andrej Ernst, a paleontologist and bryozoan expert in the Department of Geosciences at the University of Hamburg, to identify this bryozoan as the ptilodictyine Phaenopora superba (Billings, 1866).
CNSPhoto-GEOLOGISTElkanah Billings (1820-1876) originally described this bryozoan species in 1866. He was Canada’s first government paleontologist, and he very much looked the part. Billings was born on a farm near Ottawa. He went to law school and became a lawyer in 1845, but he gave up dusty books for the life of a field paleontologist. In 1856 Billings joined the Geological Survey of Canada. He named over a thousand new species in his career. The Billings Medal is given annually by the Geological Association of Canada to the most outstanding of its paleontologists.

References:

Billings, E. 1866. Catalogues of the Silurian fossils of the island of Anticosti: with descriptions of some new genera and species. Dawson brothers.

Ross, J.P. 1960. Larger cryptostome Bryozoa of the Ordovician and Silurian, Anticosti Island, Canada: Part I. Journal of Paleontology 34: 1057-1076.

Ross, J.P. 1961. Larger cryptostome Bryozoa of the Ordovician and Silurian, Anticosti Island, Canada: Part II. Journal of Paleontology 35: 331-344.

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