Thecosmilia Trichitoma Posted February 22, 2021 Share Posted February 22, 2021 I found this bivalve eroding out of the Pleistocene Bay Point Formation of Point Loma near Sunset Cliffs in San Diego CA. Does anyone know the ID or have a good resource for Bay Point Formation Mollusks that isn’t paywalled. This isn’t important for the ID, but the matrix filling in the shell is full of original aragonite shell material! It’s common at the site, but still really amazing! 1 It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt -Mark Twain Link to comment Share on other sites More sharing options...
IsaacTheFossilMan Posted February 22, 2021 Share Posted February 22, 2021 Looks like Opis rosarioensis to me. I will try to find some resources, if you promise to let me win the contest... Joking! ~ Isaac; www.isaactfm.com "Don't move! He can't see us if we don't move!" - Alan Grant Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry. Link to comment Share on other sites More sharing options...
IsaacTheFossilMan Posted February 22, 2021 Share Posted February 22, 2021 I found this. It may be referring to the Cretaceous, but, hey, who said 60 odd million years makes a difference!? Jokes aside, it talks about Opinae, the subfamily, which could be useful, if my identification is anything near correct! CRETACEOUS OPINE BIVALVES FROM THE PACIFIC SLOPE OF NORTH AMERICA AND PALAEOBIOGEOGRAPHY OF SUBFAMILY OPINAE.pdf ~ Isaac; www.isaactfm.com "Don't move! He can't see us if we don't move!" - Alan Grant Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry. Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted February 22, 2021 Share Posted February 22, 2021 Opis went extinct in the Cretaceous so it's a pretty big difference. It doesn't really match Opis anyway. It seems similar to Semele decisa which is also reported from the type locality of the Bay Point Formation. Link to comment Share on other sites More sharing options...
IsaacTheFossilMan Posted February 22, 2021 Share Posted February 22, 2021 Attacking this from a more general perspective, Astarte sp. comes to mind. So does Tellina sp., although this seems a bit too spherical for Tellina. ~ Isaac; www.isaactfm.com "Don't move! He can't see us if we don't move!" - Alan Grant Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry. Link to comment Share on other sites More sharing options...
IsaacTheFossilMan Posted February 22, 2021 Share Posted February 22, 2021 2 minutes ago, Thomas.Dodson said: Opis went extinct in the Cretaceous so it's a pretty big difference. It doesn't really match Opis anyway. It seems similar to Semele decisa which is also reported from the type locality of the Bay Point Formation. Opis went extinct in the Palaeocene. ~ Isaac; www.isaactfm.com "Don't move! He can't see us if we don't move!" - Alan Grant Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry. Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted February 22, 2021 Share Posted February 22, 2021 1 minute ago, IsaacTheFossilMan said: Opis went extinct in the Palaeocene. During the KT extinction, so Cretaceous really. Link to comment Share on other sites More sharing options...
IsaacTheFossilMan Posted February 22, 2021 Share Posted February 22, 2021 1 minute ago, Thomas.Dodson said: During the KT extinction, so Cretaceous really. Last recorded appearance was 56mya, so, pretty much K, I agree. I've just realised I got my times all messed up... I read 60mya, as 60tya... I think I'm a bit tired... Anyways, yes, it does seem reminiscent of Semele. Could you send me the resource to it being reported there? I'm not disagreeing with you, I just would like to read it to get more of a feel for the area. ~ Isaac; www.isaactfm.com "Don't move! He can't see us if we don't move!" - Alan Grant Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry. Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted February 22, 2021 Share Posted February 22, 2021 1 minute ago, IsaacTheFossilMan said: Last recorded appearance was 56mya, so, pretty much K, I agree. I've just realised I got my times all messed up... I read 60mya, as 60tya... I think I'm a bit tired... Anyways, yes, it does seem reminiscent of Semele. Could you send me the resource to it being reported there? I'm not disagreeing with you, I just would like to read it to get more of a feel for the area. Do you have the reference for the last recorded appearance for me to read? The source I read listed last appearance at the literal KT boundary, 66.043 mya. Here's the Bay Point reference. https://www.jstor.org/stable/1300903 Link to comment Share on other sites More sharing options...
IsaacTheFossilMan Posted February 22, 2021 Share Posted February 22, 2021 11 minutes ago, Thomas.Dodson said: Do you have the reference for the last recorded appearance for me to read? The source I read listed last appearance at the literal KT boundary, 66.043 mya. Here's the Bay Point reference. https://www.jstor.org/stable/1300903 Thank you! Opis virginalis has been reported up to the Palaeocene. https://www.biodiversitylibrary.org/page/16341130#page/69/mode/1up I believe it's on page 78. On Mindat.org | Opis virginalis, it is referenced. (I find Mindat.org to be much easier to digest!) ~ Isaac; www.isaactfm.com "Don't move! He can't see us if we don't move!" - Alan Grant Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry. Link to comment Share on other sites More sharing options...
LabRatKing Posted February 22, 2021 Share Posted February 22, 2021 Im getting some papers on the subject now. Aditional tip- there is an addon for Chrome and Brave browser called "Unpaywall" which makes it super easy to see if your paper is available from a different source. It is perfectly legit as it does not bypass anything, just points out open sources for the same title. 1 Link to comment Share on other sites More sharing options...
IsaacTheFossilMan Posted February 22, 2021 Share Posted February 22, 2021 1 minute ago, LabRatKing said: Im getting some papers on the subject now. Aditional tip- there is an addon for Chrome and Brave browser called "Unpaywall" which makes it super easy to see if your paper is available from a different source. It is perfectly legit as it does not bypass anything, just points out open sources for the same title. Interesting, thanks for sharing! ~ Isaac; www.isaactfm.com "Don't move! He can't see us if we don't move!" - Alan Grant Come to the spring that is The Fossil Forum, where the stream of warmth and knowledge never runs dry. Link to comment Share on other sites More sharing options...
LabRatKing Posted February 22, 2021 Share Posted February 22, 2021 My vote is for Lucinoma sp. Perhaps L. annulatum one of the indicator species in the area? https://archive.org/details/biostor-232490/page/n1/mode/2up Though Epilucina sp. is very highly likely also...perhaps even californica https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.964.7036&rep=rep1&type=pdf Link to comment Share on other sites More sharing options...
Thecosmilia Trichitoma Posted February 22, 2021 Author Share Posted February 22, 2021 If this helps, I have exposed the underside so that the muscle scars are visible. Thank you so much for all fo the responses, they are really helpful! It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt -Mark Twain Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted February 22, 2021 Share Posted February 22, 2021 16 minutes ago, LabRatKing said: My vote is for Lucinoma sp. Perhaps L. annulatum one of the indicator species in the area? https://archive.org/details/biostor-232490/page/n1/mode/2up Though Epilucina sp. is very highly likely also...perhaps even californica https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.964.7036&rep=rep1&type=pdf I did think it looked similar to Lucina and other Lucinids. This is something I can get behind now that I took a closer look at the hingement which is more like Lucinids and that it is reported from the area. For what it's worth a good generic character of Epilucina sp. over other Lucinids are the medium sized, strongly asymmetric lunule. Although we're working off of one valve a picture of the lunule with the valve sitting flat might help. Examination of other generic characteristics will require more preparation of the specimen. I'm not sure what the generic characteristics of Lucinoma are. Table from "Kurihara Yukito, April 2007. Occurrence of Epilucina californica (Conrad) (Bivalvia: Lucinidae) from the Neogene of Japan, with notes on the biogeographic history of Epilucina. Paleontological Research 11(Apr 2007):29-39" Link to comment Share on other sites More sharing options...
LabRatKing Posted February 22, 2021 Share Posted February 22, 2021 3 minutes ago, Thomas.Dodson said: I did think it looked similar to Lucina and other Lucinids. This is something I can get behind now that I took a closer look at the hingement which is more like Lucinids and that it is reported from the area. For what it's worth a good generic character of Epilucina sp. over other Lucinids are the medium sized, strongly asymmetric lunule. Although we're working off of one valve a picture of the lunule with the valve sitting flat might help. Examination of other generic characteristics will require more preparation of the specimen. I'm not sure what the generic characteristics of Lucinoma are. Table from "Kurihara Yukito, April 2007. Occurrence of Epilucina californica (Conrad) (Bivalvia: Lucinidae) from the Neogene of Japan, with notes on the biogeographic history of Epilucina. Paleontological Research 11(Apr 2007):29-39" Agreed. This specimen might benefit from some careful scratch and peck to expose more of the diagnostic structures. I haven't hunted this site in years and years, but I remember the matrix being fairly soft. EDIT...just noticed the exposed version. WIll follow up shortly. Link to comment Share on other sites More sharing options...
LabRatKing Posted February 22, 2021 Share Posted February 22, 2021 From Occurrence of Epilucina californica (Conrad) (Bivalvia: Lucinidae) from the Neogene of Japan, with notes on the biogeographic history of Epilucina In particular 3a, both 3b, and 4b being pretty diagnostic to this specimen. Particularly fun as this critter is basically still around! Link to comment Share on other sites More sharing options...
Thecosmilia Trichitoma Posted February 22, 2021 Author Share Posted February 22, 2021 Here is a better image of the lunule. 1 It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt -Mark Twain Link to comment Share on other sites More sharing options...
Thecosmilia Trichitoma Posted February 22, 2021 Author Share Posted February 22, 2021 And another image of the the underside with all of the last dirt cleaned off. 1 It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt -Mark Twain Link to comment Share on other sites More sharing options...
Thomas.Dodson Posted February 22, 2021 Share Posted February 22, 2021 1 hour ago, LabRatKing said: In particular 3a, both 3b, and 4b being pretty diagnostic to this specimen. Particularly fun as this critter is basically still around! Agreed. Link to comment Share on other sites More sharing options...
Thecosmilia Trichitoma Posted February 23, 2021 Author Share Posted February 23, 2021 So, is Epilucina californica confirmed as the ID? Thanks for all of the help! It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt -Mark Twain Link to comment Share on other sites More sharing options...
LabRatKing Posted February 23, 2021 Share Posted February 23, 2021 1 hour ago, Thecosmilia Trichitoma said: So, is Epilucina californica confirmed as the ID? Thanks for all of the help! I’d not go so far as to say confirmed for species, but I’m confident of the genus. we have a few bivalve folks around here that might be able to dial it in. Link to comment Share on other sites More sharing options...
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