Diamphidiocystis-Pyrgocystis Comm., near Ord./Sil. boundary, Guilford, Illinois (Ordovician to of the United States)

Where: Illinois (42.4° N, 90.3° W: paleocoordinates 20.2° S, 58.7° W)

• coordinate based on political unit

• local area-level geographic resolution

When: Gamachian to Gamachian (449.5 - 440.8 Ma)

• "Basal Silurian (Llandovery A) or possibly latest Ordovician (Gamachian). The unit with this fauna overlies the Maquoketa Group but lies below the Mosalem, according to Dennis Kolata (pers. comm. 1986). The age determination as Silurian rests on sparse conodont data (D. Kolata, pers. comm. 1986): G. Klapper (pers. comm. 1986) does not consider the conodont data conclusive."

Environment/lithology: open shallow subtidal; dolomitic, silty, cherty/siliceous wackestone and dolomitic siltstone

• Part of the authors deeper shelf group. Disarticulation of skeletons predominant. "The bedding and apparent absence of some common benthic gruops (corals and molluscs) suggests somewhat restricted environment, but near enough to normal marine salinities that echinoderms can be an imporant (in fact, dominant) component...a somewhat offshore position (BA3, possible inner BA4) is favored."

•SEP environmental call based on given information and regional context.

• "The dominant lithology is a flat-lying, silty, wavy-bedded dolowackestone with local chert and dolomitic nodule horizons. Some portions of theunit are laminated dolosiltstones with only rare skeletal debris."

Primary reference: T. J. Frest, C. E. Brett, and B. J. Witzke. 1999. Caradocian-Gedinnian echinoderm associations of Central and Eastern North America. Paleocommunities--a case study from the Silurian and Lower Devonian 638-783 [M. Foote/K. Koverman/P. Wagner]more details

Purpose of describing collection: paleoecologic analysis

PaleoDB collection 26685: authorized by Michael Foote, entered by Michael Foote on 24.10.2002

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names
unclassified
  -
Apiocystitidae indet.
Stylophora
 Mitrata -
Diamphidiocystis sp.
Edrioasteroidea
  - Pyrgocystidae
Pyrgocystis sp.
Pyrgocystis sp. Bather 1915
Crinoidea
 Inadunata -
Inadunata indet.
 Calceocrinida - Calceocrinidae
Calceocrinidae indet.
Calceocrinidae indet. Meek and Worthen 1869 Sea lily
Bryozoa
  -
Bryozoa indet.
Bryozoa indet. Ehrenberg 1831
Brachiopoda
  -
Brachiopoda indet.
Brachiopoda indet. Cuvier 1805
Rhynchonellata
 Orthida -
Orthida indet.
Orthida indet. Schuchert and Cooper 1932
 Orthida - Hesperorthidae
Hesperorthis sp.
Hesperorthis sp. Schuchert and Cooper 1931
 Atrypida -
Protatrypa sp.
Protatrypa sp. Boucot et al. 1964
Trilobita
  -
Trilobita indet.
Trilobita indet. Walch 1771 trilobite