This one is a complete shell with both valves (or maybe it's just one that was flipped over?).
The other is a partial of the brachial valve and you can see the muscle attachment scars.
Sowerbyella is an Ordovician genera but if anyone has any more information on where they may originate, formation wise, please let me know.
For fun (yeah, I know) I did some online sleuthing. The geological map of Wisconsin shows that Lafayette County, WI (where Shullsburg--no "c"--is located) is mostly underlain by Middle Ordovician Sinnipee Group rocks. Looking up Sinnipee on the USGS Lexicon ("Geolex") turned up a USGS Professional Paper 309, available as a (huge) PDF file from the USGS publications site. This paper describes the Decorah Formation (part of the Sinnipee Group). In particular, the Guttenberg Limestone Member contains Sowerbyella. The paper also lists about a zillion lead/zinc mines in the Shullsburg area. Apparently most if not all of them were underground workings and are abandoned. Which one your brach specimen came from is anyone's guess. There are no obvious mine workings visible around Shullsburg on Google Earth, but the Shullsburg town website describes a defunct mine and museum right in the town that's open for tours.
ReplyDeleteCheers,
--Howard
Howard - Thanks for the research help. I too consider the research process to be fun in it's own way. I'll have to look that paper up myself when I next have the chance. The Decorah Formation sounds as likely a candidate as any since it is the most widespread and fossiliferous Ordovician formation in the upper midwest.
ReplyDelete-Dave
Cunningham in lilydale have hash layer of one kind. Cunningham is classified as Decorah formation anyway but I separate the two because of rock colors.
ReplyDeleteBeside from the looks of things late ordovivcian fossils are vastly underreported from minnesota. I keep finding fossils either reported from other states, even a few that might be undescribed.
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