I was searching the
web for mollusk resources, when I stumbled across your website and
the 'mystery' section. I took particular interest in these shells
from Wyoming: (I
am unable to do much formatting with gmail and so if anything is unclear,
please feel free to ask me)
The "possible Juga"
is Goniobasis tenera (now Goniobasis is considered synonymous
with Elimia, however, I've had an interesting yet brief discussion
with R.T. Dillon at COFC about this (http://www.cofc.edu/~dillonr/cvweb.htm)
The bivalves are Pleiselliptio
priscus (more ovate shape) and P. littoralacustris (more
The ID is based on J.H.
Hanley's PhD dissertation (Hanley is now deceased), which is the most
thorough analysis of the mollusks of the Green River Formation. I
don't have the original references handy, however, so I can't remember
who coined the name. I did my master's work on the Green River, so
I have spent quite some time with these
There are numerous collectors
who label gastropod fossils from the Green River as 'turritellids'
- these are all the internal casts of Goniobasis tenera. These
shells are often found in thick coquinas and these rocks are cut and
polished and labeled "Rattlesnake Agate" in some rock shops.
There are a few other species of snail from the green
river, but rarely are they collected in any quantitiy (Viviparus sp.
is the other that comes to mind).
I've included a short
bibliography of some more recent GR mollusk papers. I'm working on
pleistocene terrestrial gastropods for my PhD, but have a soft spot
in my heart for the Green River.
Hanley, J.H. 1974. Systematics,
paleoecology, and biostratonomy of nonmarine Mollusca from the Green
River and Wasatch formations (Eocene), southwestern Wyoming and northwestern
Colorado. Unpublished Ph.D. dissertation, University of Wyoming, Laramie,
Hanley, J.H. 1976. Paleosynecology
of nonmarine Mollusca from the Green River and Wasatch Formations
(Eocene), southwestern Wyoming and northwestern Colorado, in scott,
R.W. and West R.R., eds. Structure and Classification of Pleocommunities:
Stroudsburg, Dowden, Hutchinson and Ross, p. 235-261.
Hanley, J.H. and Flores,
R.M. 1987. Taphonomy and Paleoecology of Nonmarine Mollusca: Indicators
of Alluvial Plain Lacustrine Sedimentation, Upper part of the Tongue
River Member, Fort Union Formation (Paleocene), Northern Powder River
Basin, Wyoming and Montana: Palaios v.2. p. 479-496.
Kuchta, M.A., Geary
D.H., Carroll, A.H., 2000, Utility of nonmarine mollusca as paleoenvironmental
indicators in the Green River Formation, Wyoming, Abstracts with Programs
- Geological Society of
America, v. 32 no. 7, p. A12.
Kuchta, M.A., 2000,
Paleoenvironmental significance of nonmarine mollusca in the Luman
Tongue of the Green River Formation, Wyoming, Unpublished Master's
University of Wisconsin, Madison, 65p.
PhD student at UW Madison
(hiding out on the north shore)
210A Heller Hall, UMD campus