The lost Arnioceras or The hunt for a name

There are specimen that are appear unremarkable when you collect them, and you don´t
have high hopes for them,  but you take them home anyway.


Nodule with ammonite in3 pieces as found

Nodule with ammonite in3 pieces as found

This was very much the case for this specimen shown as found ex-situ in
Robin Hoods Bay this March. It just showed the section of an ammonite
on the side of the nodule, when formatting the rock, the part containing the
ammonite also fell into 3 pieces due to natural cracks.
I think there might have been a moment when I thought of chucking the
bits into the sea,  but the breaks were clean and promised to be simple to
glue so it went into the bag…

For one of the final stages of prepwork, which the air abrading usually is for me,
I often accumulate a few specimen that have been previously roughly prepared
with a big pen, then fine prepped with a small pen and just need that little bit of
extra cleaning with the air abrader – preparations before and cleaning up after
air abrading take some time and I usually don’t do that for single specimen.

I had glued the parts of the small nodule back together again, and after finishing
my other specimen to be abraded,  I had a bit of powder still in the tank and
decided just to test the ammonite to see what it was.
With nodules that have been weathering or a while that usually works, even if
the nodule itself is not completely abradeable due to increasing hardness of the
matrix when the weathered layer is off.

To my surprise, I could just keep on abrading…
The matrix was soft enough to be abraded at a relatively low pressure (3.5 bar),
the ammonite´s shell was beautifully preserved in dark grey calcite, and the
ammonite had a very strong undamaged keel.

I had initially wondered if it could be an Arnioceras, and that seemed to be the
correct genus identification.


Arnioceras sp., 5 cm diameter

Arnioceras sp., 5 cm diameter

BUT: I had never found a Yorkshire Arnioceras that could be air abraded from the matrix.
I don´t think even a very weathered semicostatum  matrix e.g. from the Holderness Coast
ever becomes abradable.
AND it looked different from all the species I had described in an earlier blogpost (link).

The innermost whorls up to about 1 cm are relatively smooth just like in Arnioceras semicostatum,
but the ribbing is more straight and finishes almost abruptly at the edge of the venter.


Arnioceras sp., 5 cm diameter, view of keel

Arnioceras sp., 5 cm diameter, view of keel


The keel on the venter is very strong, similar to Arnioceras falcaries, but
it´s whorl section is more rectangular.
It also has less ribs per whorl than the species mentioned : about 25 ribs / whorl at 5 cm diameter.


Arnioceras sp., 5 cm diameter, view of keel & whorl section

Arnioceras sp., 5 cm diameter, view of keel & whorl section

So I started getting out the books…(which in these days most of the time is
starting the full text database on the computer)
First candidate I found was Arnioceras oppeli GUÉRIN-FRANIATTE, but while whorl
section,  style of ribbing and keel was a good match,  the count of ribs/whorl of my
specimen was lower, and A. oppeli seems to not have smooth innermost whorls.


Arnioceras bodleyi (J. BUCKMAN), 7 and 5 cm diameter, Kilve/Somerset

Arnioceras bodleyi (J. BUCKMAN), 7 and 5 cm diameter, Kilve/Somerset

I then remembered the purchased Kilve/Somerset Arnioceras specimen I have in my
collection, which is Arnioceras bodleyi (J. BUCKMAN, 1844).
(incidentally it was James BUCKMAN, not SS BUCKMAN, who “founded” this species
(in the words of his son Sidney Savoury BUCKMAN, of “Yorkshire type ammonites”
Very good match with the strong keel, style of ribbing, but again slightly less ribs/whorl
in my specimen, and maybe less compressed than the Kilve specimen, and no keel
I was ready to call it a close enough match at this point in time. But I still had that
nagging thought that you have when something does not completely fit…

As a final check I consulted with some friends from the facebook Yorkshire fossils
collectors group if they had seen a similar Arnioceras from a soft matrix –
and Dave showed me a perfectly matched specimen from Redcar, in a very soft matrix !

Now two occurrences of Arnioceras in soft matrix make a pattern, so I scanned
HOWARTH´s summary of Bairstow´s collection again for Arnioceras from
Robin Hoods Bay – and found mentions of Arnioceras above the semicostatum
subzone, in the turneri zone, birchi/brooki subzone !

Ammonites from these subzones in Robin Hoods Bay show exactly the same style of
preservation and “abradebility”, unfortunately HOWARTH does not figure them,
the brooki subzone Arnioceras from the Bairstow collection are mentioned as
“?Arnioceras sp. indet. 1,lost”, and I unfortunately don´t remember from my last visit
what the two specimen from the birchi subzone housed in the collection looked like.

So back to the database…what species of Arnioceras occurs above the semicostatum
subzone ?

Kevin Page´s paper “The lower Jurassic of Europe: its subdivision and correlation”
delivers a hint on Arnioceras hartmanni from the brooki subzone, but no figure…

No luck in the Palaeontological Association´s “Fossils from the Lower Lias of the
Dorset Coast”  either – “not figured“.

But finally Alpheus Hyatt´s “Genesis of the Arietidae” has a figure (Plate II, fig. 17)  –
and it´s a perfect match and he also mentions that it can be found in the Whitby area !!!
Similarly fitting is D’ORBIGNY´s specimen of “Ammonites kridion” which was revised to
“Ammonites hartmanni” by OPPEL which I found after a bit of internet research in the
Paris Muséum National D’Histoire Naturelle’s online collection (very nice !)

It is still somewhat “circumstancial evidence”, since the ammonite was found ex-situ,
and of course therefore I cannot with absolute certainty know that this ammonite
really is from the brooki subzone but I think it´s close enough to give it a name,
at least with a “cf.” :

Arnioceras cf. hartmanni (OPPEL)

So if anyone has a Caenisites brooki together with an Arnioceras from Robin Hoods Bay,
please let me know, for final proof 🙂

Anyway, who would have thought that you can spend this much fun time on a rainy
weekend prepping and digging through palaeontological history on this (only seemingly)
unremarkable little ammonite ?
The excitement of the fossil hunt becomes the hunt for a name, which to me can be
almost as exciting.


Literature and Links :

Paris Muséum National D’Histoire Naturelle’s online collection, “Ammonites kridion” :
Schlegelmilch R. (1992), Die Ammoniten des süddeutschen Lias, 2nd Ed,
Gustav Fischer Verlag
Howarth M.K. (2002),  The Lower Lias of Robin Hood´s Bay, Yorkshire, and the work of
Leslie Bairstow, Bulletin of The Natural History Museum Geology Series Vol. 58/2, London
Oppel  A. (1856), Die Juraformation  Englands,  Frankreichs  und des südwestlichen Deutschlands.
Jahreshefte  des  Vereins  für  vaterländische  Naturkunde  in Württemberg
Hyatt, A. (1889), Genesis of the Arietidae, Smithonian Contr. Knowl., Washington
Page, K. (2003), The Lower Jurassic of Europe: its subdivision and correlation,
Geological Survey of Denmark and Greenland Bulletin 1

Recent prep results and What´s in the queue ?

Recent prep results, numbers see text

Recent prep results, numbers see text

You might have noticed, I´ve deviated from my usual schedule of posting an article about every 2-3 weeks…
There are a couple of reasons, none bad, which have kept me from posting.
Reason number 1 is that commitments from my daytime job have kept me unusually busy for January and February and this will stay that way at least until mid march,
so you´ll have to wait for  a new full article until about 3-4 weeks time.

Reason number 2 is I´ve been working on several full articles, but due to my perfectionism I was not satisfied with what I could have posted…

In the “unfinished posts” queue is the first part of the Dactylioceras article, dealing with the lower toarcian Dactylioceras species.
When looking at some of the ammonites I was photographing (every little prep fault  somehow gets exaggerated when you look through a lens…),
I found that most of them needed some form of re-prep to comply to the same standard I´ve been trying to adhere to for the book.
This is for example the reason why #7 in the photograph, a Dactylioceras (Orthodactylites) clevelandicum,  went back to the top of my prep queue :
The inner whorls needed some more attention with the fine air pen and the air abrader – it had been found in 2002 and basically went straight to the drawer at that time.

Reason number 3 is I need to clean up my prep slate before I go for my traditional spring collection tour to make space for potential new finds,
so the proportion of time prepping was higher that the one on writing…
All of the ammonites (and other fossils) have been prepped last weekend, in case you´re wondering what they are here´s the list :

  1. Dactylioceras (Orthodactylites) tenuicostatum,  7 cm
  2. Double of Dacytlioceras commune, 5 & 4 cm, thanks to Dr. Mike Howarth for helping to correct my inital thoughts on this one…
  3. A Plagiostoma sp. bivalve, 6 cm,  from the apyrenum subzone of the middle lias, a “first” for me, I´ve never seen one before from the Yorkshire lias…
  4. A combo of Amaltheus stokesi (5.5 cm) , Amaltheus bifurcus (2.5 cm) , Amaltheus wertheri (2 & 1 cm)
  5. Pleuroceras hawskerense, 6 cm
  6. Dactylioceras (Orthodactylites) semicelatum, 5 cm
  7. Dactylioceras (Orthodactylites) clevelandicum, 9 cm

Another article that´s in the “unfinished posts” queue for a long time already is about pathologies on Yorkshire coast liassic ammonites, for the simple reason that
literature about pathologies was somewhat thinly spread across a wide range of publications, most of the time with few pictures (so important for the amateur collector !).
But thanks to Prof. Dr. Keupp from FU Berlin this has now changed ( :
A brand new copy of his almost 400 page thick, large format, just released new atlas on cephalopod palaeopathologies has landed on my desk, I had only very little time to study it yet, but what I´ve seen so far is
spectacular (pictures galore !) and will surely set the scientific standard on this topic for years to come (unfortunately it is currently only available in german).
So through this new publication my “sick ammonites from Yorkshire” post will take a giant leap forward and will be published after the first part of the Dac post…











Asteroceras blakei or The first description

This is an Asteroceras blakei SPATH, 1925 from Robin Hoods Bay, found by Keeley and Adrian on the 20th of April, 2011 (guess what, my little red book told me that…).
They entrusted this 10 cm ammonite to me for the preparation using my air abrader. After securing the remaining shell with a bit of liquid super glue, to stop it from flying away in the air stream (it easily does that by the way) , I prepped it and it came out like this.
Asteroceras blakei SPATH, 1925, 10 cm

Asteroceras blakei SPATH, 1925, 10 cm

But this is not all that this little story is about, it´s more about finding out more about Asteroceras blakei. 
I usually at least try to take a look at the original description of the author. As you can see from the name, the original describer of this species, Leonard Frank Spath, did name this ammonite in 1925.
In HOWARTH 2002 the ammonite was pictured and full details were given for the original describer and the year, a list of synonyms (Asteroceras marstonense SPATH is one), some museum references, and, in the references the name of the publication where SPATH described the ammonite :
“Notes on Yorkshire ammonites. The Naturalist, Hull, 1925”. The Naturalist, as I found out, is the periodical publication of the West-Riding Consolidated Naturalists’ Society and, later, the  Yorkshire Naturalists’ Union.  Some volumes (between 1865 and 1921) can be found at :
They´re delightful reading, most is about fungi, lichen, spiders, birds, etc. but sometimes there is something about geology or fossils. If you open one of the volumes in Acrobat reader and search for “ammonite”,  in the 1921 volume for example you´ll find some not so pleased remarks on BUCKMAN´s then new nomenclature in his “Yorkshire type ammonites” or the prohibitive cost of printing for some of his volumes, in the 1909 volume a short arcticle about “The ammonites called A. serpentinus”, some species of the Harpoceras genus,  including a picture of the giant Harpoceras (then called H. mulgravium) that is now exhibited in Whitby museum. But no luck with the 1925 volume…
I sent out severall calls of help to the various forums I visit, but first to no avail. I had almost given up, when after almost 5 months later out of the blue I received a note from Dr. Rene Hoffmann, from the Ruhr University at Bochum, sending me copies of the two pages describing Asteroceras blakei – thanks again for that !
So here is that first picture of Asteroceras blakei SPATH, 1925 :
Asteroceras blakei, the original picture from "The Naturalist", 1925

Asteroceras blakei, the original picture from “The Naturalist”, 1925

But that´s almost all that SPATH writes about this new species – I must admit I was somewhat underwhelmed for all the trouble it took to find this description !
Thanks of course to Keeley and Adrian, for letting me borrow, prep & photograph the ammonite !

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.

Standing on the shoulders of giants or Ammonite literature

Standing on the shoulders of giants

Just a small selection of ammonite literature I´m using to write this book

When you start collecting ammonites seriously, you want to know what you have found. Most collectors early in their collecting life begin by picking up everything that looks like a fossil (just as I did) . Only later, when your drawers start to overflow up or simply because you are interested in one type of fossil more than in others, specialization will happen.
Chances are that for identifying your finds you´ve had one or more of the more general fossil books which cover everything from foraminifera to dinosaurs and mammals. For every fossil group these naturally can only show the most common representatives of that group – when you specialize, you will very soon get to the limits of these books, even for a fossil group such as ammonites, with a lot of very common representatives.

Now palaeontology is a science with hundreds of years of history and many palaeontologists specialized on ammonites and published their works about them.
A brief snip from my literature index, in my view with particular importance to the liassic ammonites in Yorkshire, Britain and elsewhere :
Ammonite literature

A brief snip from my ammonite literature index, spanning approximately 6000 pages

This constitutes an estimated 6000 pages of some rather specialized books and papers.
I have them all in my library and have read through many, but not all of them, some are just ad-hoc reference. But this is something only somebody as crazy as I am will do. You will have trouble getting access to many of these books and papers since many are out of print for a long time or in a pay-per-view internet library. For some you will have to pay collector´s prizes if you wanted a printed book, like the very popular Lias SCHLEGELMILCH that sometimes costs more on eBay now than what you had to pay after it was freshly published.
I think this is in the process of change at the moment as Open Access (see ) gradually becomes more accepted and more and more journals open up their back volumes to public access in the form of pdf files. Some scientists even publish a pdf copy of every paper they can scan on their own server – though there still may be copyright issues with newer publications on there (that´s why I won´t put the link on here).

As you can see in some of the titles, these monographs tend to be very specialized as well, only covering e.g. one family of ammonites, one specific stratigraphy, one location. These are publications that have been made with the scientist in mind, everything is as reproducible as possible, and in many cases statistical studies have been made to verify population boundaries as for example in HOWARTH´s Hildoceratidae monograph – I´m deeply awed by these works and not always completely without regrets of having chosen another profession. But this is not for everyone…
All this taken together amounts to one of the reasons I´m writing this book : I get a feeling that something “in between” is needed, something bridging the gap
between the specialist paper and the amateur collector that allows to get a decent overview of the Yorkshire ammonites without reading tons of papers.
And who knows how this project might turn out : Nowadays it´s just a difference of a few mouse clicks (OK a bit more)  and you publish your paper as a real paper book, an e-book  or an open access pdf file… although I must admit a real paper book is my absolute favourite option of these.