Derbyia crassa (Meek & Hayden, 1859)

General abundance:  Common

The is one of the larger specimens found at this locality.

Viewer Comments:

The specimen you illustrate is a juvenile, a little over 1 cm in
diameter. Although small, the shape and ribbing is so close to the
many illustrations of Derbyia crassa in Dunbar & Condra (1932)
that there is no reason to hesitate with the species name. Also,
Hoare (1961) illustrates this species and comments that it is a
common species. Dunbar & Condra (1932) note that this is
the common species of Derbyia in the midcontinent.

Your photo of the pedicle valve (the more 3 dimensional,
pyramidal valve) shows a distinct round beak area with
dots and small bumps. This is a feature that Dick Grant
and others finally determined to be the area where the
pedicle emerged to hold the shell in place. This round
beak has a large number of small holes that were apparently
openings for tiny threads of pedicle that extended outward
and passed into sediments to act as an anchor. This type
of pedicle attachment is quite unusual among brachiopods.

Dr. Tom Yancey

References:

Dunbar, C.O. and Condra, G.E., 1932, Brachiopoda of the Pennsylvanian
System in Nebraska; Nebraska Geological Survey, Bulletin 5, p.79,
pl.3, figs,1-12

Hoare, R. D., 1961, Desmoinesian Brachiopoda and Mollusca from
Southwest Missouri; University of Missouri Press, p.27, pl.1,
figs.17-23

Hoare, R.D., 1968, Pennsylvanian brachiopods of Ohio; Ohio Geological
Survey Bulletin 63, p.26, pl.3, figs.1-4

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