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Dactylioceras (Orthodactylites) semicelatum (Simpson 1843)



7cm. From Kettleness near Whitby in Yorkshire, GB. Semicelatum subzone, tenuicostatum zone of the Whitby Mudstone Formation. Lowest Toarcian. I aquired this one from Byron Blessed at the Petrefakta last year.

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Ammojoe

Posted

Hi Roger,

I was just researching Dactylioceras on Google whereupon I stumbled across this gallery image. I don't know if D. annulatum exists; but if it's from the tenuicostatum zone is certainly can't be a D. annulatum as there's only four 'grey shales Dacs' [D. crosbeyi, D. clevelandicum, D. semicelatum, and D. tenuicostatum]. I think your ammonite is actually a D. semicelatum.

Ludwigia

Posted

Hi Joe,

I got this ammonite from Byron Blessed from Fossils UK at the Petrefakta here in Germany where he had a stand and just took over the information on the ammonite from him. I figured he knew what he was talking about, but you obviously seem to have your doubts. Is annulatum maybe a synonym?

Ammojoe

Posted

Roger,

This ammonite is definitely a D. semicelatum - there's no other 'valid' species it can be. I should have made myself clearer earlier, but yes, I am pretty sure it's a synonym for D. semicelatum (or potentially, can't find the paper that confirms which yet, D. tenuicostatum). As far as I am aware D. annulatum is no longer considered valid.

Ludwigia

Posted

PS. I just found an old post of Byron's in a thread I started here a few years ago where he shows D.annulatum and says that it occurs together with D.semicelatum.

Ammojoe

Posted

Thanks for the link, Roger. I'm following Howarth's 1973, 'The Stratigraphy And Ammonite Fauna Of The Upper Liassic Grey Shales Of The Yorkshire Coast' - there's no mention of D. annulatum; just the aforementioned other four species.

Personally I would consider D. annulatum a synonym of D. semicelatum. I do not believe they occur together as different species, instead, there is just one valid genus.

Ludwigia

Posted

I don't have that publication myself (Do you have a pdf of it perhaps that you could send me?), but I do know that Byron refers to it. Maybe you should send him a message asking if he knows anything new about that species. Perhaps he could aid you in your research....or you could teach him something new...

Ammojoe

Posted

PM sent.

Ludwigia

Posted

I just recieved an answer from Byron and he has corrected the ID and now it's clear that Ammojoe was right in his assumption.

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