>One of the mysteries of fossil vs recent cones, is that many fossil
>cones are sinistral, while NONE of the modern species are (unless i have
>missed something?).  Can anyone tell me when the left-handed cone
>species died out, and whether this was a sudden or a gradual process?
 
Conus adversarius Conrad, 1840, of which probably all of Petuch's "species" of
Contraconus are variants, appears in the lower Pliocene, a little over 3.8
million years ago but less than 5 million, about the same time as sinistral
Busycon, in the lower Goose Creek Limestone, Tamiami Limestone, and
equivalents.  It survived until the end of the Pliocene, about 1.6 million
years ago (end of the James City Formation, upper Waccamaw Formation, upper
Caloosahatchie Formation, and equivalents), a time of widespread extinction
of warmer-water taxa in the northwest Atlantic.  The extreme variability
shown in the lower Pliocene Pinecrest Formation forms disappears earlier,
by about 3.5 million years ago.
 
Rare sinistral specimens of Conus ventricosus are known from the Recent,
but the usually sinistral adversarius lineage is extinct.
 
David Campbell
 
"Old Seashells"
 
Department of Geosciences
CB 3315 Mitchell Hall
University of North Carolina at Chapel Hill
Chapel Hill NC 27599-3315
USA
 
919-962-0685
FAX 919-966-4519
 
"He had discovered an unknown bivalve, forming a new genus"-E. A. Poe, The
Gold Bug