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I've been looking at my specimens of Acrocoelites trisulculosus from the Toarcian Jet Rock (Mulgrave Shale Member = Falciferum Zone) of the north Yorkshire coast. This is an anoxic mudstone deposited during a prominent worldwide Ocean Anoxic Event (OAE) and, as might be expected, the preservation is very good. A number of them (7 so far) have a thin pyrite layer around the apex. This shows obvious lineation in all of them, mostly oblique to the axis of the rostrum. As pyrite is often associated with soft tissue decay, I strongly suspect that this is preserving muscle texture. The texture is similar to that preserved in some other coleoids (e.g. from Solnhofen). Has anyone else seen this? Comments welcome! EDIT: I may be wrong about the soft preservation - a few well preserved specimens from other localities (though not from here) show similar texture on the calcite. Most belemnites look smooth though. (Comments and photos further down this thread) Just two of the specimens here: No. 1: No. 2: left lateral (with divided dorso-lateral furrow - a little unusual) right lateral
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Please could anyone suggest what this is? I'm assuming fish, with little (less than 1mm) white spherules that might be teeth or denticles. From the Jet Rock (Mulgrave Shale Member) - a Lower Jurassic, Toarcian shale at least partly deposited in anoxic waters. Near Whitby, Yorkshire, UK. (Acquired in an auction as an extra with another fossil that I really wanted so I'm just curious really, I know little about fish!)
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At over 4" across, this is the last few chambers of by far the largest diameter belemnite phragmocone I've ever seen. (If anyone has one from a Megateuthis, I'd love to see it! - they don't seem ever to be preserved.) Given to me by a friend, it is in a nodule from the Jet Rock (Upper Lias, Lower Jurassic) of Port Mulgrave, north Yorkshire coast. It must have belonged to an exceptionally large Acrocoelites trisulculosus which is probably the only belemnite to occur in this bed. It's a large species anyway - typical rostra of it are 5 - 7" long but about 9" has very rarely been recorded so a bit longer may be possible. Photo 6: Not having such a large Acrocoelites in my collection, I've done a conservative mock-up of it with a smallish (9") Megateuthis and another piece of phragmocone which is my second largest... A total length of 20 - 24" seems about right. Photo 7: For comparison , I have a complete but crushed example of A. trisulculosus about 12" long, the rostrum being 6.5". 1) 2) 3) 4) 5) 6) This should probably be stretched more... 7) A normal size Acrocoelites trisulculosus with crushed phragmocone (the strange ridged structure on top of it is a crushed on-edge Harpoceras shell mouth)
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