gtheo Posted December 19, 2020 Share Posted December 19, 2020 It's been awhile since I have posted here. Found on beach in San Francisco. Area has Merced deposit fossils, mostly marine sediments Pliocene-Pleistocene. I am assuming it's a bivalve of some sort. I have found similar fossils at this location. The unusual thing about this one is it has symmetrical grooves on both sides on one end. I will first post pictures to give an overview of the fossil and in the comments will post the area with the "grooves". I am having trouble attaching files. will try attaching in comments. Link to comment Share on other sites More sharing options...
gtheo Posted December 19, 2020 Author Share Posted December 19, 2020 overview images Link to comment Share on other sites More sharing options...
gtheo Posted December 19, 2020 Author Share Posted December 19, 2020 more overview images Link to comment Share on other sites More sharing options...
gtheo Posted December 19, 2020 Author Share Posted December 19, 2020 the "grooves". what are they? Link to comment Share on other sites More sharing options...
gtheo Posted December 19, 2020 Author Share Posted December 19, 2020 another view of the grooves Link to comment Share on other sites More sharing options...
Tidgy's Dad Posted December 19, 2020 Share Posted December 19, 2020 I would guess that the grooves are the muscle scars. 1 Life's Good! Tortoise Friend. Link to comment Share on other sites More sharing options...
Plantguy Posted December 19, 2020 Share Posted December 19, 2020 Very nice find! Are the lines around what would be the inner margins of the valves/shells? I think that's what your views show. If yes I'm thinking they reflect the traces of the ribs like in the cockles. I am pretty sure we collected something similar in Sonoma County from the Merced Fm when I was there many many moons ago but with more shell material still left on the steinkerns. They were pretty hefty bivalves. Something like Clinocardium maybe. Heres a photo I have from a Florida type like we have around here on the east coast. Here's a local San Mateo db link to some photos that you might find useful and you might want to check out. Clinocardium nuttalli, Basket Cockle Fossil, 1.5-.75 Ma The San Mateo County Historical Association Online Collections Database Cardiidae indet., basket cockle fossil, possibly Miocene dating from between 23.03 to 5.333million years ago commonly found at low tide in littoral (sandy and muddy bottom) or sub-littoral (open bay, muddy marine) zones. Fossils taken from Merced Formation collected at Westborough Boulevard at Highway 280 in the late 1970s or early 1980s. https://historysmc.pastperfectonline.com/webobject/4935E90A-493C-4990-B6ED-364128533729 Mike or one of the other bivalve folks will probably set you straight if my guess is off base.. Continued hunting success! I always liked the SF/bay area...not true winter but it could be a bit brisk and just tolerable when the fog was in and wind was a howling.... Regards, Chris 1 Link to comment Share on other sites More sharing options...
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