Brachiopods of Mason City Mbr., Shell Rock Fm., North-Central Iowa (Devonian of the United States)

Where: Iowa (43.3° N, 92.8° W: paleocoordinates 31.4° S, 37.4° W)

• coordinate based on political unit

• basin-level geographic resolution

When: Mason City Member (Shell Rock Formation), Early/Lower Frasnian (383.7 - 382.4 Ma)

• Mainly in early Frasnian Tenticospirifer shellrockensis zone, but extending slightly into overlying Strophodonta cicatricosa zone.

• member-level stratigraphic resolution

Environment/lithology: marine; shelly/skeletal, argillaceous limestone and dolomitic grainstone

• Witzke et al. (ref. 9582): mainly shallow subtidal.
• From Witzke et al. (PBDB ref. 9582): "The Mason City Member is dominated by skeletal limestone and dolomitic limestone (calcilutite to calcarenite), in part argillaceous, in the type area; it includes prominent stromatoporoid biostromes at all localities. Hardground and discontinuity surfaces, locally encrusted with edrioasteroids and auloporids, are noted..."

Collection methods: Fauna of the Shell Rock not reported here include mollusks, corals, stromatoporoids, and echinoderms. These elements usually dominate the assemblages.

Primary reference: J. Day. 1988. The brachiopod succession of the Late Givetian-Frasnian of Iowa. In N. J. McMillan, A. F. Embry, and D. J. Glass (eds.), Devonian of the World, Volume III. Canadian Society of Petroleum Geologists. Calgary, Alberta, Canada 303-325 [M. Foote/M. Foote/M. Foote]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 35493: authorized by Michael Foote, entered by Michael Foote on 17.12.2003

Creative Commons license: CC BY (attribution)

Taxonomic list

Strophomenata
 Productida - Strophalosiidae
Strophalosia sp. King 1844
S. n. sp.
 Productida - Productellidae
 Orthotetida - Areostrophiidae
Floweria sp. Cooper and Dutro 1982
F. n. sp.
 Strophomenida - Leptostrophiidae
 Strophomenida - Strophodontidae
Rhynchonellata
 Athyridida - Athyrididae
 Spiriferinida - Cyrtinidae
Cyrtina sp. Davidson 1858
C. n. sp.
 Spiriferida - Cyrtospiriferidae
 Spiriferida - Spinocyrtiidae
 Spiriferida - Adolfiidae
 Spiriferida - Mucrospiriferidae
 Pentamerida - Gypidulidae
 Atrypida - Atrypidae
Spinatrypina sp. Rzhonsnitskaya 1964
S. n. sp.
 Rhynchonellida - Hypothyridinidae
 Rhynchonellida - Stenoscismatidae
 Orthida - Schizophoriidae
 Orthida - Dalmanellidae
Lingulata
 Lingulida - Lingulidae
Lingula sp. BruguiƩre 1797
L. n. sp.
Craniata
 Craniida - Craniidae