Big and Small or A history of synonyms…

I showed you a relatively large Radstockiceras buvignieri  (from the collection of my friend Klaus) in an earlier post, now here´s the smaller Radstockiceras from my own collection :

Radstockiceras buvignieri, pyrite, 3 cm

Radstockiceras buvignieri, pyrite, 3 cm

This one is preserved in solid (stable) pyrite and came from the polymorphus subzone, together with a few other finely pyritized ammonites like Tragophylloceras numismale and Polymorphites sp.  (more on these later…)  Is this the same species as the larger version ? Preservation is certainly very different, the large Radstockiceras is preserved in grey limestone. I doubt my friend Klaus would forgive me if I broke open the large Radstockiceras  he loaned me to check if the inner whorls are the same as (the outer whorls) of the smaller pyrite ammonite (if preserved at all…) – Imagine me giving him back a small bag of rubble, saying “Thankyou, here´s your ammonite back, I ckecked something on it, but it came to no result…” ! I guess there would have been a chance to do this – the large ammonite had been broken in the middle when found – but there is no photographic record of what the inner whorls looked like (I feel yet another blog article coming up – photographing your finds shortly after you´ve made them…).
I had put the pyrite ammonite towards Radstockiceras complanosum, especially since I had seen a picture of one extremely similar ammonite in HOFFMANN´s 1982 publication about the lower Pliensbachien of North-West Germany. There it was listed as Radstockiceras oppeli, a few years later SCHLEGELMILCH 1992 lists this as a later synonym of Radstockiceras complanosum :
Radstockiceras oppeli (SCHLOENBACH, 1863)
Radstockiceras complanosum (SIMPSON, 1855)         -> since described earlier, this species has priority
HOWARTH 2002 goes even further and lists Radstockiceras complanosum as a synonym for Radstockiceras buvignieri :
Radstockiceras buvignieri (D´ORBIGNY, 1844)           -> since described even earlier, this has priority
Since HOWARTH obviously had the opportunity to compare against SIMPSON´s holotype, this is what it is labeled now as well : Radstockiceras buvignieri
The full list of synonyms even contains different genera (Ammonites, Retenticeras, Metoxynoticeras) as well, painting a picture of more than 150 years of different authors in different locations working on potentially differently preserved ammonites, of (early) branching and (final ?) joining of species names.
AndyS
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4 Comments

  1. Joe

     /  June 18, 2012

    Hi Andy,

    Thanks for sharing your knowledge, its been very interesting to read. Do you know the current state of Riparioceras – as sometimes I’ve seen it purveyed as a synonym of Gleviceras, but I’m unsure of the accuracy of this. I’d appreciate your insight into the matter.

    Regards,
    Joe

    Reply
    • Joe,
      Actually Riparioceras is quite different from Gleviceras :
      While Riparioceras is usually quite small (e.g. 4 cm) and has a rectangular whorl section and a thin, sharp keel, Gleviceras can grow quite large (e.g. 40 cm !) and
      has an oval whorl section and may or may not have a keel, depending on species.
      I´ve not seen Riparioceras from Yorkshire.

      All the best,
      AndyS

      Reply
  2. Joe

     /  June 18, 2012

    Thank you very much, Andy. I didn’t think they were synonymous because they look so different – but if you look at this website it appears, as I interpret it, to suggest they are synonymous (http://www.bgs.ac.uk/Palaeosaurus/Record.cfm?sample_id=544222) and this is what confused me. Thanks for clearing the matter up.

    Regards,

    Joe

    Reply
    • Joe,
      That entry in the BGS´s Palaeosaurus database does not mean they think its a synonym (though it appears that DONOVAN & FORSEY in their 1973 paper “Systematics of Lower Liassic Ammonitina” thought so) – putting Riparioceras in brackets behind Gleviceras means they treat it as a subgenus under Gleviceras. I have not been able to track down (yet) which author(s) thought so, but they must have some reason to think they´re more closely related than different genera.

      All the best,
      AndyS

      Reply

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