These are not the Androgs you’re looking for – the Liparoceratidae

Liparoceras (Becheiceras) gallicum

While colloquially these will always remain the “Androgs” (and “Lipos”), these are the
genera that this blogpost will be about, and not many are actually Androgynoceras
by the most recent  naming convention.
I have been attempting to write this blog post on and off for the last years and always
found groups of ammonites easier to research and describe and the Liparoceratidae
always went into the backlog again. This may be due to their variability and also due
to the impression you get when you look into the standard monograph, the 1938
“A catalogue of The Ammonites of the Liassic Family Liparoceratidae” [1],
written by Leonard Frank Spath. The table of contents lists no less than 93
species and variants, and there is no easy approach for this monumental work.

The Liparoceratidae can be categorized by their obvious morphology :
(only the species I have so far found in or photographed from Yorkshire
shown here)

  • The “capricorns” are evolute ammonites where the consecutive whorls don’t
    overlap each other a lot – the result is the typical open spiral ammonite.Aegoceras (Beaniceras) luridum
    Aegoceras (A.) maculatum
    Aegoceras (A.) maculatum var. leckenbyi
    Aegoceras (A.) maculatum var. atavum
    Aegoceras (A.) lataecosta
    Aegoceras (A.) artigyrus
    Aegoceras (A.) capricornus
    Aegoceras (Oistoceras) figulinum
  • The “sphaerocones” where consecutive whorls widely overlap each other a
    lot which creates inflated ammonites with deep umbilical funnels :Liparoceras (Liparoceras) cheltiense
    Liparoceras (Liparoceras) divaricosta
    Liparoceras (Liparoceras) naptonense
    Liparoceras (Becheiceras) gallicum
  • Morphologically linking capricorns and sphaerocones are the so called “hybrids”
    which have capricorn inner whorls,  but develop large Liparoceras-style outer whorls:Androgynoceras sparsicosta
    Androgynoceras heterogenes

This classification also used by Spath this is a purely morphological approach, that does
not include any interpretation of relationships or evolution.
We´ll get to that later in this blog post…

Aegoceras (Beaniceras) luridum (SIMPSON, 1855)
luridum sz

Beaniceras luridum

This species has so far eluded me apart from a very small, almost undiagnostic ammonite,
and some doubtful fragments.The small ammonite sits on the whorl of a larger Lytoceras
in a nodule characteristic for the subzone.
Beaniceras luridum is quite similar to Aegoceras (A.) maculatum, ribs while strong on the
flank are not as prominent on the venter as on A. maculatum and swing forward on the
venter to create convex curves. Well preserved specimen show thin intermediate ribbing.

 

Beaniceras luridum, Ehenfeld/Germany

The german specimen pictured above shows the characteristics a bit better than the small
Robin Hoods Bay specimen. Hope to find a well preserved bigger Yorkshire specimen some
time…

Aegoceras (A.) maculatum (YOUNG & BIRD)
maculatum sz

Aegoceras maculatum

This is the standard “Androg”, a relatively common ammonite, depending if you´re in the
right place at the right time. In the 1990s we used to pick up 10 specimen in an hour on
Bay Ness, probably because debris from earlier cliff falls was “ripe”, i.e. nodules were
washed out of the bigger blocks. Today you need to search long and hard in the same
place to find a decent ammonite.
Robust ribbing, between 20 and 22 ribs / whorl at around 70 mm. Mature specimen
with suture crowding show a characteristic hood at the mouth border as pictured on
the specimen above. Strong calcite shell which unfortunately often stays in the negative
when nodules are hit with a hammer, but that also means that perfect splits revealing
all (inner mould) whorls of the ammonite are relatively common.
Shell preservation is rarely seen in collections as the Yorkshire matrix is
usually not abradable.  The species is quite variable, we´ll see some variants below.

Aegoceras maculatum, mostly preserved with shell

Aegoceras (A.) maculatum from lower in the maculatum subzone can be found in
septarian sideritic nodules (e.g. Bairstow bed 581, 585) with some interesting
preservation where the sideritic veins seem to have grown between inner mould
and shell :

Aegoceras maculatum in septarian nodule

There are large specimen of A. maculatum that maintain the “normal” ribbing pattern of
A. maculatum at sizes above 70 mm,  SPATH seems to have called them “var. arcigerens”
and considered them late developments.
Two 80 mm examples shown below, I have heard of specimen around 100 mm.

 

Aegoceras maculatum – large specimen

Aegoceras (A.) maculatum (YOUNG & BIRD) var. leckenbyi SPATH, 1938
maculatum sz

Aegoceras maculatum var leckenbyi

Aegoceras maculatum var leckenbyi

The var leckenbyi of A. maculatum retains a whorl section and ribbing pattern which at
approx. 60-70 mm is not distinguishable from a normal A. maculatum, after which size
the whorl starts to swell and develops bi-tuberculation and a liparoceratid ribbing pattern.
Andogynoceras heterogenes in contrast has more massive whorls at 60-70 mm already
which can be separated from var. leckenbyi and A. maculatum.
Both specimen shown here are fully septate, so fully complete specimen including the
body chamber would have been significantly larger, e.g. 20-30 cm.

Aegoceras (A.) maculatum (YOUNG & BIRD) cf. var. atavum SPATH, 1938
maculatum sz

Androgynoceras maculatum cf. var. atavum

I have one specimen that might fit into the atavum variant for A. maculatum.
It has ribbing much reduced in depth, which could also (and in my view probably
more likely) be the result of a pathology, also given the apparent rarity of this form.
The specimen does have a mostly complete body chamber.

 

Aegoceras (A.) artigyrus (BROWN, 1837)
capricornus sz

Aegoceras artigyrus casts from geoed.co.uk

The two lower specimen have been figured in [8], table 4 as syntypes for
“Defossiceras defossum” ; I have not been able to trace the origin of the first one.

I’ve been on the hunt for this ammonite quite a while, even bought some casts
from GeoEd some time ago to get an impression of the morphology.

Unfortunately these casts, while their details are absolutely stunning in detail,
did not help me then,because they were missing a crucial element, the original color.
Only at the beginning of this year, when John Fam re-posted a tweet from Zoe Hughes
on the Ammonite facebook group, I restarted my search for this morphology in my
collection again. The proverbial light bulb moment came when I finally realized that
A. artigyrus is found in the capricornus sz in the oyster bed or above – ammonites
from these beds in Yorkshire are readily recognizable due to their light rusty
brown color !

Aegoceras artigyrus in sideritic matrix

Aegoceras artigyrus multi

Ammonites from the capricornus sz are not often well preserved, inner whorls can be pure
calcite and when weathered this calcite often has a soft chalky consistency… Despite this I
have in my 30+ years of collecting found a couple of well preserved specimen which I had
previously all labeled as A. lataecosta…

At 2.5 cm diameter : 26 ribs/whorl
Outer whorls of bigger specimen : 20-22 ribs/whorl
Difference to A. capricornus, A. lataecosta : Swelling of whorls at smaller diameters

 

Aegoceras artigyrus

The above specimen was bought from Byron Blessed, originating from an old
collection.

A. artigyrus is also where the name “Defossiceras defossus” has found it´s home,
see Hugh Torrens wonderful compliation in the Geocurator 2/6 here :

” Detection at the Sedgwick: An illustration of the Importance of Data Retention”
https://www.geocurator.org/images/resources/geocurator/vol2/geocurator_2_6.pdf

and M.K. Howarth´s description in [2], pg. 143.

The “Defossiceras defossum” in Whitby museum is a mis-identified Euagassiceras.

Aegoceras (A.) lataecosta (J. de C. SOWERBY, 1827)
capricornus sz

 

Aegoceras lataecosta

Aegoceras lataecosta seems to be a relatively rare species in Yorkshire.
It’s inner whorls cannot be distinguished from A. artigyrus or A. capricornus,
but it retains a constant 26 ribs/whorl even at bigger diameters,
and whorl section remains relatively compressed.
A. lataecosta does have quite a thick shell, which in most cases with Yorkshire
material is either chalky white and/or very brittle and is relatively easy to remove
with an air abrader. The pictured specimen also is an inner mould, and therefore
looks slighty different than the normally shelled A. lataecosta from Dorset.

Aegoceras (A.) capricornus (SCHLOTHEIM, 1820)
capricornus sz

Howarth 2013  does not list a Yorkshire Aegoceras capricornus amongst the finds
of Leslie Bairstow [2], neither does Spath in the specimen list in his 1938
Liparoceratidae monograph.
The Rotunda Geology Group (web site link http://www.rotundageologygroup.org/)
figures a specimenfrom the Robinson collection, clearly from the  sideritic beds of the
capricornus sz, but unfortunately the keel is not shown.

So I’m rather happy that I have two specimen that show the classic feature of a
A. capricornus, the flattened ribs crossing the venter.

Aegoceras capricornus

 

Aegoceras capricornus, flattened ribs on venter

Some rib statistics : 25 ribs/whorl outer whorl, next whorl in 21 ribs/whorl
Looking at these ammonites it is likely that A. artigyrus, A. lataecosta, and
A. capricornus are only slightly different morphologies of the same species.

Aegoceras (Oistoceras) figulinum (SIMPSON, 1855)
figulium sz

 

Oistoceras figulinum

The beds Aegoceras (Oistoceras) figulinum occurs in are in general relatively soft
and erode easily, and in my observation there is no significant hard nodule development
protecting the ammonites from being destroyed in the waves. Therefore it took a
relatively long time until I found well preserved specimen in a relatively freshly fallen
block in 1997. The above ammonite came from this fall.
As I´m both a collector of ammonites and starfish/crinoids, I was especially pleased
when Mike Marshall offered me (and he knew I could not resist ! ) a specimen of both
on one small block !

Oistoceras figulinum and Palaeocoma milleri brittle stars

2 other species of Aegoceras (Oistoceras) also occur on the Yorkshire coast,
A. (O.) angulatum and A. (O.) sinuosiforme in slightly deeper beds than
A. (O.) figulinum. I have not found any well preserved specimen from these
beds so far.

Androgynoceras sparsicosta (TRUEMAN, 1919)
luridum/maculatum sz

 

Androgynoceras sparsicosta

Possibly bed 585 , on lighter brown, very slightly septarian nodule
15-16 ribs/whorl.

This one surprised me, I had not expected to have it in my collection.
I found it in the cellar in my prep backlog while looking for unprepped specimen that
would fit into this blog post, only the outer whorl was visible, so I was happy to see an
acceptable inner whorl after prep.

Aegoceras sparsicosta from maculatum sz

I always knew this bigger specimen on a maculatum sz type nodule was different,
it did not fit the pattern of A. heterogenes developing liparoceratid ribbing at larger
diameters. Only when I realized it also occurs in maculatum subzone and counted
the ribs, it struck me that this is also a A. sparsicosta.
Unfortunately it is an ex-situ nodule, it would have been interesting to know at which
exact level it occurs.

Phelps 1985 [7] postulated a division of the maculatum subzone into a sparsicosta zonule
and a maculatum zonule, which Howarth 2002 [2] rejected due to the ammonite figured
as A. sparsicosta in this paper being a complete non-match for the holotype, and a
typical A. maculatum instead.

Bairstow had not found any specimen matching Trueman’s A. sparsicosta holotype,
figured in Spath 1938, plate V, fig. 7, so Howarth had no indication they ocurred on
the Yorkshire coast. Spath does not mention any finds from the Yorkshire coast
either (he mentions most of his Yorkshire specimen came from Bairstow anyway),
so A. sparsicosta indeed seems to be quite a rare ammonite on the Yorkshire coast.

The bigger specimen shows the specific preservation characteristics mentioned
by Howarth [2] for Bairstow bed 590.61, high in maculatum sz – the white chalky
circular spots.
If this preservation is indeed specific for this bed, it would mean that A. maculatum
and A. sparsicosta share the same stratigraphical distribution, thus the
sparsicosta zonule would be identical to the maculatum zonule.

A. sparsicosta has elongated nodes on the outer whorl :

Nodes Andogynoceras sparsicosta

Left maculatum sz specimen, right luridum sz specimen

As with A. maculatum, Androgynoceras sparsicosta can also be found in sideritic
septarian nodules, but often torn apart or squashed :

Androgynoceras sparsicosta in septarian nodule

This specimen is probably transitional to A. heterogenes.

Androgynoceras heterogenes (YOUNG & BIRD, 1828)
maculatum sz

Androgynoceras heterogenes + maculatum

Again a wonderful specimen found & prepped by Mike Forster, kindly sold to me.
It contains an incomplete, fully septate A. heterogenes and a mostly complete A. maculatum.

Androgynoceras heterogenes

Specimen found & prepped by Mike Marshall, kindly sold to me.
Strong capricorn inner whorls and good development of liparoceratid ribbing, but still septate.

Androgynoceras heterogenes + 3 Aegoceras maculatum

A specimen I found quite a long time ago with 1 large A. heterogenes (fully septate) and
3 A. maculatum. There´s a slight pathology of the ribbing on the capricorn part of the whorl.

Androgynoceras heterogenes – possible microconch

A possible microconch with mostly complete body chamber.
The rate of whorl breadth increase is higher than on any other A. heterogenes
in my collection.

Comparison (left to right)
A. sparsicosta
A. heterogenes
A. maculatum

Comparison of similarly sized specimen of (from left to right) A. sparsicosta,
A. heterogenes,  and A. maculatum. Androgynoceras heterogenes is really only
comparable to Aegoceras  maculatum in the first 3-4 centimeters, where specimen
of this size cannot be separated.
After this diameter, the whorl of A. heterogenes begins to quite massively swell,
at a higher rate than A. sparsicosta. After about 7-8 cm the normal ribbing changes
over to bi-tuberculation and liparoceratid ribbing pattern.

Androgynoceras heterogenes – different sizes

The first two specimen in this series are possible microconchs (unfortunately the
relevant area still has shell) and show possibly complete body chamber, while the
right two are fully septate, imcomplete specimen. Both A. heterogenes and
A. sparsicosta have elongated nodes on the ribs after about 3-4 cm.

As already indicated, also the large liparoceratid forms of A. heterogenes are most
often  found as fully septate phragmocones, indicating that at least half a whorl of
body chamber is missing. A section of a liparoceratid body chamber fragment from
maculatum sz is shown below, indicating possible sizes of complete specimen to be
in the area of 20-25 cm.

A. heterogenes body chamber fragment

Liparoceras (Liparoceras) cheltiense (MURCHISON, 1834)
masseanum sz

Liparoceras in general is probably less common on the Yorkshire coast than in Dorset,
and well preserved specimen are a rarity, which also can be difficult to prep.
The relatively small specimen of L. (L.) cheltiense is an example, it was painstakingly
prepped with air pen and abrader from a block of solid ironstone :

Liparoceras cheltiense –
as found

Liparoceras cheltiense

Liparoceras (Liparoceras) divaricosta (TRUEMAN, 1919)
figulinum sz

 

Liparoceras divaricosta

This rather water worn specimen is from figulinum sz, its whorl is much thinner
than that of Liparoceras (Becheiceras).

Liparoceras (Liparoceras) naptonense SPATH, 1938
luridum/maculatum sz

 

Liparoceras naptonense (Bolton collection)

This Liparoceras (Liparoceras) naptonese is in the T. Bolton collection, picture by kind
permission. What is immediately evident is that the ammonite has quite a long capricorn
stage which looks quite like Androgynoceras sparsicosta, I would in fact go as far to say
that this is the macroconch for the A. sparsicosta microconch.

Liparoceras (Becheiceras) gallicum
figulinum sz

Liparoceras (Becheiceras) gallicum

This truly stunning specimen was found and very nicely prepared by Mike Forster,
who kindly sold this specimen to me. It is an inner whorl of a large
Liparoceras (Becheiceras) cf. gallicum that sits inside its
partially removed (I assume because it was crushed) outer whorl.
I assume from the preservation that this came from the figulinum sz, which matches
literature and also my own observation, as the whorl section below showing the complex
suture of Liparoceras (Becheiceras) was found 1997 inside a fallen block that was also
full of Aegoceras (Oistoceras) figulinum – the A. figulinum pictured above also came
from that same block.

Liparoceras (Becheiceras) gallicum – suture

A very large liparoceratid outer whorl found in 2006 has been donated to the Robin Hoods Bay
Old Coastguard station, and gives an indication what sizes could be possible.

Liparoceras (Becheiceras) gallicum

A wider interpretation

The naming of the ammonites above is according to the latest published literature.

Looking closely at the ammonites, for me a pattern becomes apparent, that would
reduce the number of species quite drastically. As I´ve already indicated above,
Androgynoceras sparsicosta looks very much like a capricorn microconch /
immature version of a liparoceratid macroconch L. (L.) naptonense. Similarly, there
seems to be a micrococh/macroconch pair for Androgynoceras heterogenes.
If you regard A. maculatum var. leckenbyi as the liparoceratid macroconch for the
capricorn microconch A. maculatum, there is another pair.
If you allow for extreme variation in developing mature macroconch liparoceratid
characteristics, you could even go as far as including
A. maculatum/A. maculatum var leckenbyi in the same chronospecies as
A. heterogenes – they seem to at least share a few cm of an indistinguishable
capricorn nucleus.

Allthough not shown here, and as far as I know not found in Yorkshire so far,
but known from Dorset, are similar pairs for A. lataecosta, A. capricornus and A. figulinum.

The Liparoceras ammonites from the ibex zone do not seem to have a recognizable
capricorn nucleus, neither does L. (B.) gallicum or L. divaricosta from the figulinum sz.
Liparoceras and Aegoceras/Androgynoceras are clearly related, but a common ancestor seems
to be lower in the ibex zone.

Unlike Liparoceras (L.) divaricosta, Liparoceras (Becheiceras) continues on into the
margaritatus zone, this is one of the reasons it is seen as a separate branch in the tree
of Liparoceratid genera, even by Spath.

There are more Liparoceratidae species out there…

As always, a blog post represents the specimen I have in my collection or am able to
photograph, and as such is a snapshot of the interpretation and knowledge derived
from these. While I wrote this, I took a lot of notes to check for certain beds, hunt for
certain ammonites, view certain ammonites in museums, view certain collections and
photograph some more ammonites, all the things I would have loved to do before
posting this.

Due to the current situation all this has not been possible this year, and I´m missing the
Yorkshire Coast and the people living on it badly. We certainly hope this will change next
year , and then there will most likely be additions to this post.

Many thanks for online discussions go to Murray Edmunds.

Literature

[1] SPATH, L.F. (1938), The Ammonites of the Liassic Family Liparoceratidae in the
British Museum (Nat. History),  British Museum, London
[2] HOWARTH, M.K.(2002),  The Lower Lias of Robin Hood´s Bay, Yorkshire, and the
work of Leslie Bairstow, Bulletin  58/2 of The Natural History Museum, London
[3] PAGE,K.N.(2004), Normanby Stye Batts – Miller´s Nab (Robin Hood´s Bay),
North Yorkshire (NZ 972 025- NZ 952 075), in : British Lower Jurassic Stratigraphy,
Geological Conservation Review Series, JNCC Peterborough 2004, pp. 250-262
[4] SCHLEGELMLICH, R.(1992) ,Die Ammoniten des süddeutschen Lias, 2nd revised
and extended edition, Stuttgart & New York
[5] EDMUNDS, M. (2009), A revision of the Lower Jurassic Ammonite Genus
Eoderoceras SPATH and its Immediate Descendants and Other Relatives,
Palaeontographical Society
[6] HOWARTH, M.K. (2013), Treatise of Invertebrate Palaeontology, (Number 57), Part L,
Revised, Volume 3B, Chapter 4: Psiloceratoidea, Eoderoceratoidea, Hildoceratoidea,
University of Kansas
[7] PHELPS, M.C.(1985), A Refined Ammonite Biostratigraphy for the Middle and Upper
Carixian (Ibex and Davoei Zones, Lower Jurassic) in North-West Europe and
Stratigraphical Details of the Carixian-Domerian Boundary, John Murray, London
[8] DONOVAN, D.T. & FORSEY,G.F.(1973), Systematics of Lower Liassic Ammonitina,
The University of Kansas Plaeontological Contributions

Pieces of a puzzle – 2 new Eparietites species for the collection

Visiting a location, especially a coastal one, over a long period of time again and again has
it’s benefits. Exposures can change every day,but extreme conditions like a bed scoured
clear off it’s usual overlying layer of pebbles can be rare, so coming often gives you more
of achance to experience this and may be even find fossils you’ve not found before
(or did not recognize before as we shall see…).

On one such occasion during the summer of 2019 I found a bed in the lower part of the
denotatus subzone scoured and some ammonites I had not found before in this
completeness in it. On a solo trip I found a large specimen to which access was
unfortunately prevented by a large beach boulder hanging over it,
which I could not move on my own.

Big ammonite on the beach wedged under a big beach boulder – I could not move it on my own !

I was however successful in finding a small nodule on the surface of the bed, with
an ammonite embedded perpendicular to the bed surface, which apparently had
already either been partially eroded by the sea or touched by another collector,
because part of the outer whorl was already missing.

On a trip a few days later together with Adrian, we were able to shift the beach
boulder together and extract the large ammonite without breaking it.
Thanks again for your help, Adrian !

Large Eparieties successfully extracted.
An outer whorl of an Aegasteroceras can be seen on thebottom left of the picture


In the immediate vicinity of the ammonite within the same bed there were also
remnants of other fossils, including a crushed Eparietites, an outer whorl of an
Aegasteroceras (crassum or sagittarium) and a crushed nautilus, which were left in place.
The Aegasteroceras would indicate this bed to be Bairstow 455.x

Small Eparietites and Aegasteroceras in the same bed as the big Eparieties


The size of the ammonite and the bed it was found in initially led me to hope it could
be an  Eparietites bairstowi, but once the umbilical width couldbe clearly measured
during the early stages of preparation, it became clear that Eparietites bairstowi
has a significantly higher umbilical width than this specimen.

Back at home I prepped both the small and the big specimen and also went through
my unprepped specimen pile, because I remembered I hadfound an outer whorl
of a similar specimen some years earlier but had not prepped it yet.

So here are the 3 specimen :

Eparietites undaries, 6 cm / 2.5 “

 

Eparietites undaries – 30 cm / 12″
Surprisingly most of the inner whorls are preserved.
Outer whorls show only light undulations, no ribbing.

 

Inner whorls of the big Eparieties – it seems the worm tubes are holding the inner whorls together, only the last 5 cm/2″ of whorls are not preserved

 

Outer whorls of an Eparietites undaries, 23 cm/ 9″,
found again in my prep backlog and finished for this blog post


Looking through some pictures I had taken for the book of ammonites in
J. Herring’s collection in 2012, I also found another specimen that neatly fits
into the size range of the others, being slightly bigger than the small one at 11 cm.

Eparieties undaries, 11 cm, Col. J. Herring
Ribs are vanishing at this size

From the whorl section of the smaller specimen it was clear that it could not be
an Eparietites impedens,  and that E. undaries would be a good candidate.
The E. undaries illustration of the lectotype in [4] and [5] shows a specimen
of about 150 mm diameter with little details of the inner whorls.
The description in [4] however states that the ribbing would change to soft
undulations of the shell at over 10 cm and that the shells of large specimens
are almost smooth.
Unfortunately the shells of the large specimen are not preserved,  but judging
from the internal moulds, this seems to be the case.
In Quenstedt’s own illustrations in [6] table 20, fig 2-6, E. undaries whorl
section for small and large specimen is clearly shown, also the gorgeous
fine shell structure seen also on the small specimen.  
A perfect picture for E. undaries from a specimen of Quenstedt’s collection,
which was the original to his illustration in [6] table 20, fig 2 is given in [7],
Plate XIII- it fits in all aspects with both my smaller specimen and the 11 cm
specimen from J. Herring’s collection.

So this settles it for these specimen – they are
Eparietites undaries (QUENSTEDT, 1884)

As the ammonites were found in close proximity to if not in the same beds
that Howarth mentions in his description for E. bairstowi, this poses the question
if E. undaries and E. bairstowi might be the same species after all.
This question has also come up in papers by Page in [2] and Edmunds in [3].

From the very large specimen Howarth figures the large E. undaries specimen
seems to be similar in all aspects apart from umbilical width. The smaller paratype
illustrated in [1], plate 2, fig 8 does seem to be more strongly ribbed on the inner
whorls compared to my small specimen, indicating E. bairstowi as likely a
separate species. Unfortunately I do not remember this specimen from my visit to the
Bairstow collection in the NHM , but comparing the 2specimen in the future would
be interesting.

Since Bairstow measured these beds between 92 and 55 years have passed
(he started in 1928 and retired in 1965) , so the illustrations of the bednumbers
given in [1] can only be approximations of the situation today.
There is no mention of any E. undaries found in these beds by Bairstow,
which returns us to what I described at the beginning of this blog post –
as these exposures are small and prone to rapid change, new finds
can be possible even after decades or centuries.

Many thanks to Murray Edmunds for discussions and showing different
Oxynoticeras and Eparietites specimen from his collection, which made me realize
that there is another Eparietites species sitting unrecognized in my collection.

They are from the other end of the Eparietites evolution towards
Oxynoticeras, I have a few specimen in my collection
where I had always been undecided between Eparietites and Oxynoticeras. 

Eparieties collenoti, Scunthorpe, 12 cm / 4 3/4″.
Purchased on eBay

Oxynoticeras simpsoni, 11 cm / 4.5″
A find from summer 2019


They show ribbing reduced to growth striations similar to Oxynoticeras, but there is still
a small shoulder on the venter revealing their relation to Eparietites.
In literature you find references to both Oxynoticeras collenoti and Eparietites collenoti.

Comparison between E. collenoti (top) and O. simpsoni (bottom). On E. collenoti a shoulder is still visible on the keel, with O. simpsoni it is missing


AndyS

Literature :

[1] HOWARTH, M.K.(2002),  The Lower Lias of Robin Hood´s Bay, Yorkshire,
     and the work of Leslie Bairstow, Bulletin  58/2 of
     The Natural History Museum, London 

[2] PAGE,K.N.(2004), Normanby Stye Batts – Miller´s Nab (Robin Hood´s Bay),
     North Yorkshire (NZ 972 025- NZ 952 075), in : British Lower Jurassic
     Stratigraphy,  GCR Series, JNCC Peterborough 2004, pp. 250-262

[3] EDMUNDS M., et al. (2016), A systematic account of the ammonite
     faunas of the Obtusum Zone (Sinemurian Stage, Lower Jurassic) from
     Marston Magna, Somerset, UK. Proc. Geol. Assoc.

[4] SCHLEGELMLICH, R.(1992) ,Die Ammoniten des süddeutschen Lias,
      2nd revised and extended edition, Stuttgart & New York

[5] S. GUÉRIN-FRANIATTE (1966) , Ammonites du Lias inférieur de France,
     Psilocerataceae: Arietidae, Paris

[6] QUENSTEDT, F.A. (1883-1885), Die Ammoniten des Schwäbischen Jura,
     Band 1, Der Schwarze Jura (Lias), Schweizerbart, Stuttgart

[7] REYMENT, R.A. (1958), On Liassic Ammonites From Skåne,
     Southern Sweden, Stockholm Contributions in Geology Vol II:6

The youngest Harpoceras or With a lot of help from my friends

One of the ammonites I‘ve conciously hunted and unsuccessfully so for at least 10 years is Harpoceras subplanatum, a species of Harpoceras from the fibulatum subzone. I‘ve even been desperate enough to buy a reference Harpoceras subplanatum from Deux Sevres / France a few years ago on eBay:

Harpoceras subplanatum , Deux Sevres / France, 16 cm diameter
Harpoceras subplanatum , Deux Sevres / France, 16 cm diameter


As you‘ve seen from the previous post about Harpoceras most members of the genus are actually from exaratum, falciferum and commune zone of the upper Toarcien, so Harpoceras suplanatum is the youngest Yorkshire member of the genus.

Harpoceras subplanatum is relatively similar to Harpoceras falciferum, so with the previous potential fragments I‘ve found, which were ex situ, in areas where there are also exaratum, falciferum and commune subzone sediments around, I just  could not be sure …

This all changed about 18 months ago, when I was fossil hunting with John at Ravenscar. There was a small fall that produced the usual fibulatum ammonites like Peronoceras and Catacoeloceras, so age was definitely confirmed. At the end of collecting at this location, we compared finds, and John showed me a discus shaped ammonite in a nodule saying something like „I think it‘s some kind of Haugia, I think I‘m going to give it a whack…“ˋ- and I said something to the effect of  

„Noooooo – Please don‘t, it‘s a rare Harpoceras subplanatum !“

This is what it looked like :

Harpoceras suplanatum in cement shale nodule as found
Harpoceras suplanatum in cement shale nodule as found


Later in the year, John decided to move south and sell off his collection in the process, and the unprepped Harpoceras went to Dave. Dave generously handed this ammonite to me this summer, and of course I was over the moon….

Howarth in his 1992 Harpoceratidae mentions 4 known Yorkshire specimen, so even if there may be more mis- or unidentified or unknown specimen in private collctions, this is definitely one of the rarer ammonites of the Yorkshire lias.

Of course it was one of the first ammonites on the prep list when I returned home after a glorious 3 week holiday in Yorkshire this summer.
Not knowing if the ammonite had inner whorls preserved, I first tackled one side which seemed the most likely to me to be preserved. I usually start ammonites in cement stone matrix by abrading off the soft outer layer to get an impression about preservation and possible cracks running through the fossil.

John or Dave had already secured one obvious crack in the nodule with liquid super glue, but I also found some more potential cracks into which I also let some liquid super glue seep in and let the nodule rest a day before I continued further  with the air pen.

Prep work with the pen turned out to be relatively easy and the matrix was not at all sticky to remove. I used magnification during air pen work to make sure I inflicted as little as possible damage to the ammonite shell.
In the end this the result of the first side, showing mainly the phragmocone of the ammonite :

Harpoceras subplanatum, first side prepped
Harpoceras subplanatum, first side prepped


The other side showed some potential to have more of the whorl, possibly a bit of the body chamber preserved, but most likley crushed to some extent.When you prep an ammonite completely free of matrix, which was my goal with this one,you have to take extra care about any potential cracks, so again this side was surveyed under magnification and all potential cracks secured with super glue, especially in the thin inner whorls and the ammonite rested for another day to have the supper glue fully solidify in the cracks.

This side proved to be similarly easy to prep but with a bit of a challenge because the body chamber had been crushed in severall layers towards the inside of the nodule, producing a stair like effect, where the edges of the next stair down needed to be detected very carefully. I decided not to prep the inner whorls more deep than on the other side, fearing to push through the inner whorls which had a crack running right through the middle anyway.


Here‘s the final result for this side :

Harpoceras subplanatum, second side prepped, 14 cm diameter
Harpoceras subplanatum, second side prepped, 14 cm diameter


When comparing Harpoceras falciferum and Harpoceras subplanatum side by side, H. subplanatum does have a less deep furrow in the middle of the whorl, and the angle of the ribs is less acute – H. falciferum has falcate ribbing, H. subplanatum falcoid ribbing. The relative umbilical width of H. subplanatum is smaller than that of H. falciferum.

Falcate Ribbing of Harpoceras falciferum
Falcate Ribbing of Harpoceras falciferum
Falcoid ribbing of Harpoceras suplanatum
Falcoid ribbing of Harpoceras suplanatum


Huge thanks to John who found this ammonite (and did not whack it) and to Dave who handed it on to me – this really means a lot to me !

AndyS

“Show me the keel, please” – or : A nodular mystery

When I´m asked to identify an ammonite from a picture, I often have to say
“show me the keel, please”,  because especially with liassic ammonites, a safe
identification of an ammonite cannot be done without  having a view of the keel.
The following example illustrates this best…

 

The mystery nodule with a partially prepared ammonite

The mystery nodule with a partially prepared ammonite

This nodule with a partially prepped ammonite was shown by David in the Yorkshire
Fossil Hunters group on facebook a while ago.

The fossil was found on the Holderness Coast as a glacial erratic, so age wise this can
basically be anything – from lower jurassic to cretaceous.
The keel of the ammonite was not prepped at this state, so identification was pure
speculation –  Schlotheimia and Caenisites were proposed candidates.

Intrigued by the nodule and the mystery, I offered David to try and prep this ammonite.
We met this summer in Robin Hoods Bay, exchanged the ammonite, and David also
allowed me to photograph another beautiful and rare ammonite,
a Xipheroceras dudressieri, which you will see in another blog post soon…

The matrix the ammonite is embedded in – a greyish-brown, relatively hard clay ironstone
like concretion – did not aid a lot in the identification – it could still be
hettangian (Schlotheimia), sinemurian (Caenisites), or even pliensbachian (Pleuroceras)
or some non-liassic formation unknown to me.

When I returned home after my vacation, I started prep work on the ammonite.
The matrix was still just soft enough to be air abraded using iron powder,
so my first check was wether this ammonite actually had a keel
(Caenisites, Pleuroceras,…) or just a furrow (Schlotheimia..).

After about an hour of carefully working towards the keel, first with an air pen, and then
with an air abrader, it was clear that the ammonite does actually have a keel, so it had to
be Caenisites – but wait, the keel is relatively strongly crenelated – could it be a Pleuroceras ?

Counting the ribs it would have to be a Pleuroceras apyrenum, and there is a bed that actually
produces nodules like these, so I went on based on this assumption…

Is this a Pleuroceras keel which I see before me ?

Is this a Pleuroceras keel which I see before me ?

Seing the beautiful preservation of the ammonite
(a milk cholcolate brown shell on a solid calcite core –
doesn´t that make your mouth water 🙂 ), I decided to completely prep the side
of the ammonite still completely hidden in the  concretion as well.

It is never without risk to prepare an ammonite from both sides, the ammonite might
break, or the innermost whorl might just blow through.

Since the concretion had some calcite-filled shrinkage cracks as well which might be
breaking points, I had to prep it most carefully and as vibration free as possible, so I
did most of the work with the air abrader, after securing the innermost whorl with a
drop of super glue, from the other side, just to be safe 😉

Keel of ammonite with deep furrows

Keel of ammonite with deep furrows

A few hours on, the furrows on the side of the keel I exposed got deeper and deeper…
Back to the books – no, there is no Pleuroceras where the furrows are that deep, even
taking into account that this specimen has shell preserved.

That means, it has to be a Caenisites after all, more specifically a Canisites turneri .
I had previously only seen smaller specimen without shell, so the crenelated keel
on larger whorl sizes is new to me.

After about 10 prep hours, here in it´s full beauty :

Caenisites turneri BUCKMAN 1925, 65 mm, found Holderness coast, D. Pearson collection

Caenisites turneri BUCKMAN 1925, 65 mm, found Holderness coast, D. Pearson collection

In summary, I think this shows how difficult it is to identify an ammonite without
having full view of all the diagnostic characteristics.

It´s been an absolute pleasure to prepare this ammonite
(but remember : Don´t ask me, I will ask you…), and of course it yielded a few more
good pictures of this species for the book and this blog.
The ammonite will be returned in the next couple of weeks to David, with special thanks .

AndyS

An ichthyosaur travels…and finds a new home

Ichthyosaur paddle bones laid out on a piece of foam for taking measure

Ichthyosaur paddle bones laid out on a piece of foam for taking measure

It was in March 1995, Klaus and I were searching the lower lias reefs at Robin Hoods Bay
for ammonites when I stumbled across something exposed at the surface of the shale that
looked like a hand… it turned out to be an Ichthyosaur paddle.

We spent a few hours excavating the mostly disarticulated bones, before the upcoming tide
chased us away. Unfortunately I do not have a picture of how the bones looked like when in
situ – this was pre-digital, and my wife had the camera with her…and we did not want to
wait another day to return with the camera, risking we would not find the bones again.
In hindsight that probably was a good decision – there was a bit of a storm the night and we
barely found the place again next day for checking if we had left any bones !

In the end there was one mostly complete paddle, a few vertebrae, some jaw sections partly
with teeth, some isolated teeth and an isolated hind fin femur.

Ichthyosaur paddle fitted in to a box and the piece of foam

Ichthyosaur paddle fitted in to a box and the piece of foam

A cover of bubble wrap for additional protection

A cover of bubble wrap for additional protection

A sheet of foam on top ...

A sheet of foam on top …

...and a lid on top and this one´s ready to travel !

…and a lid on top and this one´s ready to travel !

The ichthyosaur remains stayed mostly unprepped, only the paddle and two jaw sections
(I gave one to Klaus for his help salvaging the bones) were prepped.
The preparation was somewhat tricky since it could only be done mechanically – the bones
are not embedded in any kind of nodule and are relatively soft, so no air abrasion was
possible.

Ichthyosaur jaw parts and teeth laid out waiting to be packed...

Ichthyosaur jaw parts and teeth laid out waiting to be packed…

Fast forward almost exactly 20 years (doesn´t time fly ?)…

Discussing bones in the Yorkshire Fossil Collectors Facebook group, I mentioned the
finds we made in 1995 and was persuaded by a collector specialized on bones
(that´s you, Mark !) to post a few pictures.
Dean Lomax and Nigel Larkin expressed an interest in the fossils due to their rarity
(ichthyosaur material from the lower lias is a lot rarer in Yorkshire than from the
upper lias), so I mentioned that I would be happy to donate these (I´m really more
of an ammonite collector, you might have guessed), if they could come up with a
museum which would take them.

Contact was made with Sarah King, curator at the Yorkshire museum in York and
after a few e-mails back-and-forth a meeting on August 24 was arranged to hand
the fossils over to Sarah.

Klaus kindly donated his jaw section back to me, so the bones were again complete
as found.

...laid out on a thick sheet of foam for getting measured...

…laid out on a thick sheet of foam for getting measured…

To get the fragile ichthyosaur bones back to Yorkshire (talk about carrying owls to Athens…)
boxes were fitted with several layers of foam, one at the bottom for cushioning, one with a
cut-out of the fossils shape in the middle, and one at the top to cover.

...foam is being cut out ...

…foam is being cut out …

...the jaw parts fitted in (and you know the rest)

…the jaw parts fitted in (and you know the rest)

An afternoon of cutting foam later, the bones were safely packaged up in four boxes and
one bag (for associated bits of shale without bones).
To be able to carry the bulky (though not heavy) boxes, two large blue bags from a well
known swedish furniture chain were utilized.

All ready in the box & ready to go !

All ready in the box & ready to go !

On August 24, the bags were packed into our car and the bones made their journey to
the Yorkshire museum at York.  Sarah was met in her office, I gave her a bit of a tour
of the boxes with the bones and she in turn gave us a tour of the fossil collection
rooms in the museum.

Final hurdle was a donation panel decision in September and that was positive as well,
so everything was set.
The museum catalog number for the ichthyosaur remains is  :
YORM : 2015.618, just in case anyone needs to look it up…

Yorkshire Museum in York

Yorkshire Museum in York

Although I´m really specialized in ammonites, I can´t help myself from finding
other “stuff” 🙂 from time to time. These days, if I´d find something rare like this again,
I´d probably engage the help of Pro´s like Mike Marshall or Mark Smith to
professionally collect the bones – these guys are much better equipped and experienced
to deal with finds like this.

I´m letting this find go with one crying and one laughing eye.

One crying eye because of course one gets attached to a rare find – but it´s much better
to give it to someone much more suited to take care of this find properly and provide
access for scientific study.

One laughing eye because this frees up two large drawers for more ammonites !

Thanks to Dean Lomax and Nigel Larkin for providing the contact , to Sarah King and
the Yorkshire museum for taking care of this find and of course to the members of the
Yorkshire fossil collectors Facebook group for the many good discussions…

AndyS

What´s in a name – Catacoeloceras

Catacoeloceras cf. jordani GUEX, 5 cm diameter

Catacoeloceras cf. jordani GUEX, 5 cm diameter (or Catacoeloceras cf. engeli forma jordani if you prefer the forma type )

In summer 2012 I had the good fortune to find the above pictured ammonite at Hawsker.
I have pictured the unprepped specimen before here and finished the preparation early this
year. The preservation was somewhat special since the ammonite´s outer whorl was covered
by softer matrix and could be prepped with the air abrader straight away, allowing the spines
to be preserved.Only the inner whorl was covered by a small knob of harder matrix that had
to be carefully removed with an airpen.

I did initially have some trouble identifying the species – the outer whorl is close to what SCHLEGELMILCH lists as Peronoceras andraei, which according to HOWARTH is a synonym of Peronoceras perarmatum, but I could not find any visible fibulation on the inner whorls, which are also quite finely ribbed.

Catacoeloceras cf. jordani, inner whorls without visible fibulation

Catacoeloceras cf. jordani, inner whorls without visible fibulation

Generally, the features of this ammonite (more on this see below) point more to
Catacoeloceras,HOWARTH lists a Catacoeloceras dumortieri but the measurements
do not agree – Catacoeloceras dumortieri seems to have more depressed (wider) whorls
and a lower rib density (and we´ll get to it later).

Browsing french literature I then saw Catacoeloceras jordani, which is also noted by
GUEX (1972) as the oldest Catacoeloceras and whose measurements, taken from pictures
in literature, are pretty close to this specimen, but I still left the naming at
Catacoeloceras cf. jordani, also due to the factthat the specimen was not found in situ,
but in cliff fall debris.
I find it relatively easy to see how Peronoceras subarmatum (through loss of fibulation)
could have evolved into this species, and with the few specimen in my collection, I can see
intermediates between the two forms, but lacking the necessary amount of specimen to
prove it, this remains speculation.

Assignment of different species to Catacoeloceras or Nodicoeloceras varied wildly by author
until the late 1970s / early 1980s, HENGSBACH in 1985 defined the morphological
differences between Catacoeloceras and Nodicoeloceras as follows :

 

  • Catacoeloceras never ever shows (real) fibulation
  • Nodicoeloceras sometimes shows fibulation on the inner and/or outer whorls
  • Intermediate ribs crossing the complete whorl without bifurcation are relatively common
    with Nodicoeloceras, relatively rare with Catacoeloceras
    (e.g. 2-4 per whorl, the above pictured Catacoeloceras has 6)
  • Nodicoeloceras usually has more dense ribbing

 

Catacoeloceras seems to be a very variable genus in whorl section, in 1985 as Hengsbach
worked on Catacoeloceras, instead of creating different species names for every different
whorl section, he created forma types of C. raquinianum and C. engeli and applied some
other existing species.
The only issue with his work in relevance to Yorkshire is that most of his specimen were
quite small, mostly in the range below 30 mm, so with most Yorkshire specimen exceeding
this size, his work his difficult to apply (if you do not want to break apart you rare & prized
specimen…). Additionally most of his ammonites were not collected from specific known
horizons, which can also be difficult in the steep-hilled badlands of the french Causses,
where most of the ammonites he examined came from.
I’ve decided to not use the forma type names and stick to simple species names here –
I lack the amount of material to do any meaningful statistics to distinguish forma types
anyway…
HOWARTH defined the Ranges for Catacoeloceras and Nodicoeloceras in Yorkshire in
1978 as follows, so once you know which bed the ammonite is from, the distinction is clear :

 

Ranges of Catacoeloceras and Nodicoeloceras, compiled from HOWARTH, RIEGRAF

Ranges of Catacoeloceras and Nodicoeloceras, compiled from HOWARTH, RIEGRAF

In April this year, when visiting Mike Marshall, he showed me this beautifully prepped,
7 cm, Catacoeloceras raquinianum (which I naturally could not leave without & bought
it off him…) :

Catacoeloceras raquinianum (D´ORBIGNY, 1844), 7 cm, complete specimen

Catacoeloceras raquinianum (D´ORBIGNY, 1844), 7 cm, complete specimen

Another Catacoeloceras raquinianum procured some years earlier also from Mike shows
how difficult it is to estimate the appearance of a complete adult ammonite form an inner
whorl (which this seems to be, and a bit pathological as well) :

Small inner whorl of Catacoeloceras raquinianum, 3 cm, purchased from Mike Marshall

Small inner whorl of Catacoeloceras raquinianum, 3 cm, purchased from Mike Marshall

When you compare the coronate inner whorl of the two ammonites, it becomes clear that
they’re the same species. The fully grown adult specimen shows characteristics of
Catacoeloceras crassum on the outer whorl, though the whorl is probably not as wide.

 

Coronate inner whorl of Catacoeloceras raquinianum

Coronate inner whorl of Catacoeloceras raquinianum

When looking again at Catacoeloceras dumortieri in the latest Ammonite volume of the
TREATISE, the resemblance of at least a few specimen with what I used to lump into
Catacoeloceras puteolum struck me, especially when looking at a specimen found in April
at Ravenscar (unfortunately I cannot show a comparison picture from the Treatise due to
copyright) :

Catacoeloecras dumortieri (DE BRUN), 6 cm, complete specimen with hood at mouth border, unfortunately inner whorl not preserved

Catacoeloecras dumortieri (DE BRUN), 6 cm, complete specimen with hood at mouth border, unfortunately inner whorl not preserved

I could not find any mention anywhere that Catacoeloceras puteolum had been renamed
Catacoeloceras dumortieri, in fact they were both mentioned as early as in HOWARTH´s
1962 paper “The Jet Rock Series and the Alum Shale Series of the Yorkshire Coast”,
with C. dumortieri from the Peak Shales at Ravenscar, and C. puteolum as “not found”.

 

A survey of measurements of “Catacoeloceras puteolum” held among the members of the
“Yorkshire fossil hunters” Facebook group revealed the potential existence of two groups
which differ in their maximum whorl width, one group with a maximum whorl width of up
to 20-25 mm, the other one with a maximum whorl width of up to 30 mm :

Catacoeloceras dumortieri (DE BRUN), 6 cm, complete specimen with mouth border, associated with severall Pseudolioceras boulbiense, purchased from Mike Marshall

Catacoeloceras dumortieri (DE BRUN), 6 cm, complete specimen with mouth border, associated with severall Pseudolioceras boulbiense, purchased from Mike Marshall

Catacoeloceras dumortieri (DE BRUN), 6 cm, complete specimen with mouth border

Catacoeloceras dumortieri (DE BRUN), 6 cm, complete specimen with mouth border

Venter view of Catacoeloceras dumortieri (DE BRUN), 6 cm, complete specimen with wonderfully carved out mouth border, a work of prep art by Mike Marshall

Venter view of Catacoeloceras dumortieri (DE BRUN), 6 cm, complete specimen with wonderfully carved out mouth border, a work of prep art by Mike Marshall

Catacoeloceras puteolum (SIMPSON, 1855), 7 cm, only a few mm missing of the mouth border, purached from Byron Blessed

Catacoeloceras puteolum (SIMPSON, 1855), 7 cm, only a few mm missing of the mouth border, purchased from Byron Blessed

Venter view of Catacoeloceras puteolum (SIMPSON, 1855), 7 cm

Venter view of Catacoeloceras puteolum (SIMPSON, 1855), 7 cm

Until about 2-3 cm, the inner whorls look the same for both groups with a rib density of
about 32/whorl, then the specimen of the group reaching a larger whorl width continue
the growth in whorl width beyond about 20-25 mm up to 30 mm and reach a higher rib
density on the outermost whorl of > 36 ribs/whorl (i.e. retaining an almost constant
distance between ribs), while he group with a smaller max. whorl width do not increase
their whorl width and have a constant rib density of about 32 ribs/whorl on the outermost
adult whorl (i.e. increasing absolute distance between ribs on the outer whorl).

I´m almost sure the group with the bigger maximum whorl width can be associated with
Cataceloceras puteolum, while the group with the smaller max. whorl width is
Catacoeloceras dumortieri – if proven to be found within the same bed (which seems
possible, given the same association with Pseudolioceras boulbiense), they could –
given their similarity in the inner whorls – as well be variants of the same species or
sexual dimorphs.

When writing this blog post, I had the most difficulty finding a representative example
for Catacoeloceras crassum. I have a few candidates, some are inner whorls, one is slightly
pathological, none are complete adults, with the associated uncertainties this poses
(as seen above…). Catacoeloceras crassum is characterized by not having significant
tubercles at the bifurcation points of the ribs, being much like an inflated
Dactylioceras commune.

2 inner whorls Catacoeloceras crassum, 4 & 5 cm

2 inner whorls Catacoeloceras crassum, 4 & 5 cm

Catacoeloceras crassum (YOUNG & BIRD, 1828), 6 cm, slightly pathological

Catacoeloceras crassum (YOUNG & BIRD, 1828), 6 cm, slightly pathological

Catacoeloceras crassum, 5 cm diameter

Catacoeloceras crassum, 5 cm diameter

 

What I mentioned earlier about finds not being collected from known horizons applies to
many of the finds from Yorkshire as well – what we amateurs find most often comes from
cliff falls, most of the time touched by the sea – more work is needed to clarify exact horizons
in which these ammonites occur. Catacoeloceras is a very interesting but also intensely
variable genus – only collections from specific horizons can quantify that variability.

Literature

R.HENGSBACH, 1985 : Die Ammoniten-Gattung Catacoeloceras im S-französichen und
S-deutschen Ober-Toarcien, Senckenbergiana-lethaea 65

W.RIEGRAF, 1986 : Stratigraphische Verbreitung der Ammonitengattung Catacoeloceras
im Toarcium Europas, Senckenbergiana-thethaea 67

M.K. HOWARTH, 2013 : TREATISE ONLINE 57, Part L revised, Volume 3B,
Chapter 4 : Psiloceratoidea, Eoderoceratoidea, Hildoceratoidea, The University of Kansas

R. SCHLEGELMILCH, 1976 : Die Ammoniten des süddeutschen Lias, Gustav Fischer Verlag

M.K.HOWARTH, 1962 : The Jet Rock Series and the Alum Shale Series of the Yorkshire Coast,
Proc. Yorkshire Geological Society 33

L. RULLEAU, P. LACROIX, M. BÉCAUD, J.P. LE PICHON, 2013 : Les Dactylioceratidae du
Toarcien Inférieur et Moyen, und famille cosmoplite, Dédale Editions

J.GUEX , 1972 : Réparation biostratigraphique des ammonites du Toarcien moyen de la bordure
sud des Causses (France) et révision des ammonites décrites et figurées par Monestier (1931),
Eclogae geol. Helv 65/3

 

A moment frozen in time, part III, or A sun star by any other name would be as rare…

Plumaster ophiuroides, 11 cm with small Tropidaster pectinatus

Plumaster ophiuroides, 11 cm with small Tropidaster pectinatus

In part 2 I showed you what I then thought was a fragment of a Luidia murchisoni sun star –
well it turns out I´ve been wrong again…

In one of the fossil forums I visit, fellow collector Tarquin Bolton recently showed a fabulous
fragment of another starfish that made me re-assess my specimen and another acquisition
of a complete specimen from an old collection that I have treated myself to in 2012, shown
above.

The specimen painstakingly prepped by Tarquin, with great patience & skill removing grain
by grain of matrix with a prep needle and a modified dental descaler in about 150 hours,
shows an amazing fine structure of small ossicles similar to regular echinoids and enables
the specimen to be attributed to the genus Plumaster, more specifically to the species
Plumaster ophiuroides WRIGHT 1863, which has also been written about by
Prof. Andrew Gale (Portsmouth University) in a 2010 paper.

Fragment of Plumaster sp as found, specimen Bolton collection, picture by kind permission
Fragment of Plumaster sp as found, specimen Bolton collection, picture by kind permission
Fragment of Plumaster sp with dental descaler used for preparation, specimen Bolton collection, picture by kind permission
Fragment of Plumaster sp with dental descaler used for preparation, specimen Bolton collection, picture by kind permission
Beautiful fine ossicle structure of Plumaster arems, specimen Bolton collection, picture by kind permission
Beautiful fine ossicle structure of Plumaster arems, specimen Bolton collection, picture by kind permission

Sure enough, when I looked at the complete specimen above under magnification, I also
saw these structures, and thus it is not a Luidia, but also a Plumaster and so is the fragment
I had shown earlier.

It seems now that Plumaster is much more “common” (relatively speaking, they are still
extremely rare in absolute terms !) than Luidia, and is also quite often associated with
Tropidaster, as is the specimen shown at the top.

Plumaster is in fact, unlike Luidia (which Hans Hess placed in Solaster in 1955), not a
“true” sun star belonging to the Solasteridae family of starfish, but belongs to the
Plumasteridae, a family erected by Andrew Gale as recently as 2011.

 

Whatever their name & family , these fossil starfish are some of the rarest fossils on
the Yorkshire coast due to their fragility, both at time of fossilisation and when they are
exposed again – as so often a collector needs to be there right time & place to rescue
them from the elements and it also takes a skilled preparator like Tarquin to bring them
“to life” again properly.

 

AndyS

Gleviceras – a small Riparioceras in a big cloak

 

Gleviceras at Robin Hoods Bay is very rare – at least for me – to the point that I do not have much more than a small bit of a whorl, found at the time of the rebuilding of the sewage pipe (link) on May 1, 1996, a small bit of Gleviceras subguibalianum, from the upper Sinemurian, aplanatum subzone, Robin Hoods Bay  which is not really representable, and as usual, if you have a better one from the area, let me know !

 

The following is a Radstock/ Somerset specimen to show you what a whole Gleviceras looks like :

 
Gleviceras sp. from Radstock / Somerset, 17 cm, inner whorl not preserved

Gleviceras sp. from Radstock / Somerset, 17 cm, inner whorl not preserved

 

So did you wonder what I meant with the title of this post ?

 

Well, the astounding thing about Gleviceras is, and allthough I´ve had some discussion about it with a regular reader of this blog (that´s you Joe !) in 2012,
I’ve only relatively recently become really aware of this through Mike Howarth’s Treatise #57 volume, even as it looks very much like a member of the
Oxynoticeratidae family that it is from the outside, it starts as a tiny “Riparioceras” on the inside.

 
A 3.5 cm Gleviceras sp. from Gloucestershire shows where the journey is going...

A 3.5 cm Gleviceras sp. from Gloucestershire shows where the journey is going…

 

If you had found a pyrite “Riparioceras” at the usual size of e.g. max. 1-2 cm you’d be well excused to think that this could never,
ever develop into a Gleviceras like shown from Radstock above, and I would certainly have thought the same.

 

That is, before I saw final living (actually quite long dead) proof in this Dorset specimen on eBay below :

 
 

It is not the finest preservation that can be found, but it is just eroded enough around the umbilicus to reveal its “Riparioceras” state beginning,
something you would not see in the un-eroded state – I just had to get it, see it with my own eyes and show you…

 

Gleviceras BUCKMAN 1918 has precedence over Riparioceras SCHINDEWOLF 1962, so that “degrades” Riparioceras to a synonym for Gleviceras.

 

Just shows again, a species should never be erected on the basis of non-adult specimen only…

 

AndyS

Twice bought and three times found or Why finding the fossil yourself is best…

Amaltheus gibbosus (SCHLOTHEIM 1820), Prince Charles Cave, Isle of Skye, 8.5 cm

Amaltheus gibbosus (SCHLOTHEIM 1820), Prince Charles Cave, Isle of Skye, 8.5 cm

In my Amaltheidae post (link) I had shown you a very nice small specimen of Amaltheus gibbosus, that I had purchased from Mike Forster via Mike Marshall´s shop.

Quite recently, I had to succumb to temptation again ;-), when Mike offered a larger calcite preserved Amaltheus gibbosus from Skye – Amaltheus gibbosus according to literature is not common on the Yorkshire coast so I had basically given up finding one myself.
I was grateful to be able to plug that hole in my collection with these beautiful specimen, but why is it just not the same as finding one yourself ?
Some of the better finds start inconspicuous – and it was just like that with the following find I´d like to present you now.
When picked it up as a beach pebble at Hawsker it was then just showing a whorl cross section on the surface, and I usually investigate to see if there´s more of it…
I tried to split the rock at the ammonite, but another piece of rock broke off and showed the cross section of a second ammonite – time to bag all the pieces and take a better look during preparation !

Specimen as found with section of whorls on both pieces, oolitic structure can be seen

Specimen as found with section of whorls on both pieces, oolitic structure can be seen

Now when I removed the matrix plug in the umbilicus  of the first ammonite I knew it was something special:  There are characteristic spines on the inner whorls – It´s an Amaltheus gibbosus !

Amaltheus gibbosus (SCHLOTHEIM 1820), Hawsker Bottoms, inner whorl, width of view ca. 2.5 cm

Amaltheus gibbosus (SCHLOTHEIM 1820), Hawsker Bottoms, inner whorl, width of view ca. 2.5 cm

With this one I found after prep (I had to remove some of the remnants of the badly crushed body chamber) that it does show a bit of what is thought to be similar to the black wrinkle layer on a nautilus : A bit of specially formed shell secreted on the outer side of the inner whorl to prepare for buildup of a new bit of body chamber and supposedly helping the animal to get a better “grip” of the mantel on the shell. QUENSTEDT in 1885 called them “Bauchstreifen”  (belly stripes) since with the Amaltheidae they are consisting of spiral stripes in the dorsal overlap of the outermost whorl with the inner whorl.

Amaltheus gibbosus (SCHLOTHEIM 1820), max. width 9 cm, remnanst of wrinkle layer marked

Amaltheus gibbosus (SCHLOTHEIM 1820), max. width 9 cm, remnants of wrinkle layer marked

What would the second one that I had broken in two during my splitting attempt be ?
I quickly glued back together the pieces…
Preparation was not easy, it is never with spiny specimen. Luckily the matrix  was just soft enough so I could air abrade the inner whorl and the keel with high pressure, revealing this second, even nicer specimen of Amaltheus gibbosus.

Amaltheus gibbosus (SCHLOTHEIM 1820), Hawsker Bottoms, 6 cm diameter

Amaltheus gibbosus (SCHLOTHEIM 1820), Hawsker Bottoms, 6 cm diameter

There was something else about this rock that I somehow remembered from an earlier find : The matrix is oolitic, i.e. there are many small calcareous, sphaerical grains made up of thin concentric layers embedded in the rock, characteristic for some of the ironstone seams on the coast, in this case I think it must be the Raisdale seam.
I knew I had seen this before on the underside of an Amaltheus fragment that I had found at Staithes in 1994 and labeled as Amaltheus margaritatus. When I looked at it again in the drawer now, I realized it is also an Amatheus gibbosus, the spiny inner whorls had just been badly eroded which had made recognition difficult ! I  must have subconciously known it was something special though, since I held on to it for such a long time even though it´s just a fragment…

Amaltheus gibbosus (SCHLOTHEIM 1820), Staithes, width of fragment 5 cm

Amaltheus gibbosus (SCHLOTHEIM 1820), Staithes, width of fragment 5 cm

These 3 specimen really show that you learn so much more when you try to find an ammonite species yourself : First of all PATIENCE but secondly a lot more about the lithology of the beds you´re likely to find the ammonite in…

And then there´s the story behind the find, the memories and the “relationship” (I put this in quotes – it somehow sounds so nerdy) you build up when prepping the fossil.

I´m sure both Mike Marshall and Mike Forster did have the same sort of feelings when finding and prepping the fossils they´ve sold to me, since it shows in the quality of their prepwork. But this does not translate in any other way – memories can´t be sold – that´s why finding the fossil yourself is best, you just look at it differently, because you know it´s history from  when it just was a pebble on the beach to the final state when you put it in your drawer or display (or your blog…).

AndyS

No new species this time or Ammonite pathologies

Dactylioceras semipolitum, 6 cm, showing both sides

Hildoceras semipolitum, 6 cm, showing both sides

From time to time you might come across ammonites that look like a known species but then again they are different.
Just like the above ammonite. I had been looking at it when I was selecting the ammonites for one of the previous posts (it´s a Hildoceras semipolitum),
but something just wasn´t right :
It has a steep smooth (apart from growth lines) umbilical wall with a sharply angled edge. The ammonite is like that as far as one can see down the umbilicus.
I was looking through my books to see what it could be – H. semipolitum does not have such a sharply angled umbilical edge – until I realized it is “just” a pathology
when I turned the ammonite to the other side : There it´s just like a normal H. semipolitum should be.
Some pathologies are just like that, only a small change, a missing rib, a slight change in ribbing pattern on the body chamber, a healed fracture etc, but overall the species is still recogizable. For others the change is more drastic: a missing keel, a complete change in ribbing pattern starting very early in the shell, a completely asymmetric shell etc. leading authors in previous centuries to create new species for them, examples are Hildoceras walcotti, Monestieria errata .

"Monestieria errata", 4 cm, a Cleviceras sp. forma aegra circumdata

“Monestieria errata”, 4 cm, a Cleviceras sp. forma aegra circumdata HÖLDER 1956

Complete loss of keel or any other structural elements on the keel.

Today it is generally being recognized that these changes in the ammonite shell might have been caused by predators, parasites, diseases or interaction with other
hard-ground settling organisms like bivalves or tube worms and have set up so called “forma aegra” or “sick form” types, describing the pathologies as what they are.
“Sick” forms sometimes offer interesting glimpses into how ammonite shell growth worked and how amazingly adaptable these animals really were.
We may never fully know what caused them in all cases , only where an external cause like a settling oyster, is still preserved with the ammonite, the cause becomes obvious.

Androgynoceras lataecosta with "hook", overgrown bivalve or worm,  6 cm

Androgynoceras lataecosta with “hook”, overgrown bivalve or worm, 6 cm

A relatively common pathology : A bivalve or worm settled on the shell and was overgrown by the ammonite – a typical “bend” is created.

I´d like to show some that I have accumulated over the years, either found myself or bought from known fossil dealers.
They do represent only a portion of the described pathology types, I may add additional ones when I should find them…

forma aegra juxtacarinata HÖLDER 1956

Asteroceras sp. forma aegra juxtacarinata, cast, 5 cm

Asteroceras sp. forma aegra juxtacarinata, cast, 5 cm

Keel drawn out and relocated to the flank – it seems like the keel producing tissue was stretched to the flank and produced the keel there.
This specimen is a cast kindly given to me by my friend Klaus.

forma aegra cicatricocarinata HELLER 1964

Pleuroceras paucicostatum forma aegra cicatricocarinata HELLER 1964, 7 cm

Pleuroceras paucicostatum forma aegra cicatricocarinata HELLER 1964, 7 cm

Keel, visible on the right side, “inversed” on the left side – the exact part of the shell where it happened is eroded…

forma aegra substructa HÖLDER 1973

Catacoeloceras sp. forma aegra substructa HÖLDER 1973, 4 cm

Catacoeloceras sp. forma aegra substructa HÖLDER 1973, 4 cm

Broken out shell underlaid with new shell, bulbous shell growth at break point

forma aegra excentrica HÖLDER 1956

Zugodactylites braunianus forma aegra excentrica, 4.5 cm

Zugodactylites braunianus forma aegra excentrica, 4.5 cm, top side concave

Zugodactylites braunianus forma aegra excentrica, 4.5 cm, underside convex

Zugodactylites braunianus forma aegra excentrica, 4.5 cm, underside convex

Dactylioceras sp. forma aegra excentrica, 8 cm, showing the bowl shape from the side

Dactylioceras sp. forma aegra excentrica, 8 cm, showing the bowl shape from the side

Growth out of the normal shell symmetry into a bowl shaped form, presumably to correct a shell imbalance

forma aegra verticata HÖLDER 1956

Peronoceras fibulatum forma aegra verticata, 7 cm

Peronoceras fibulatum forma aegra verticata, 7 cm

A punctate permanent injury of the shell secreting part of the mantle probably caused by something like a lobster’s pinch with its claws creates a continuous groove across the ribs as the shell continues to be generated.

forma aegra pseudocarinata FERNÁNDEZ-LÓPEZ

Dactylioceras sp. forma aegra pseudocarinata, 7 cm

Dactylioceras sp. forma aegra pseudocarinata, 7 cm

Special form of forma aegra verticata, the adjoining ribs forming a keel like sculpture by themselves

forma aegra concreta HENGSBACH 1996

Dactylioceras sp. forma aegra concreta, pearl 2 mm diameter

Dactylioceras sp. forma aegra concreta, pearl 2 mm diameter

Pearl growth on the inside of the shell, probably similar to what happens with pearls in bivalves.

forma aegra inflata KEUPP 1976

Dactylioceras sp. forma aegra inflata, 4 cm

Dactylioceras sp. forma aegra inflata, 4 cm

Bulbous shell growth to heal a larger hole in the shell – this specimen even has septae build into the “bulb” as the animal continued to grow !

forma aegra undaticarinata HELLER 1958

Pleuroceras sp. forma aegra undaticarinata, 3 cm

Pleuroceras sp. forma aegra undaticarinata, 3 cm

Swinging keel, most often seen with Pleuroceras.

Left/right “hybrid”

Hildoceras bifrons, 12 cm  showing a strong difference between the sides

Hildoceras bifrons, 12 cm
showing a strong difference between the sides

One of the most intriguing types of pathologies : One side shows a normal Hildoceras sculpture, while on the other the spriral grove is completely missing, it looks like a bit like a Grammoceras.
This is of course no real hybrid, but the pathological side came to be through loss/damage/sickness of the spiral grove producing part of the mantle.

forma aegra undatispirata KEUPP & ILG 1992

Dactylioceras sp. forma aegra undatispirata, 6 cm (Col. D. Groocock)

Dactylioceras sp. forma aegra undatispirata, 6 cm
(Col. D. Groocock)

Dactylioceras sp. forma aegra undatispirata, 6 cm
(Col. D. Groocock)

Dactylioceras sp. forma aegra undatispirata, 6 cm (Col. D. Groocock), keel view

Dactylioceras sp. forma aegra undatispirata, 6 cm
(Col. D. Groocock), keel view

Swinging whorl, apparently to equalize an imbalance in the shell caused by e.g. an oyster settling on the shell

The mystery…

Amaltheus stokesi without keel, 11 cm

Amaltheus stokesi without keel, 11 cm

Amaltheus stokesi without keel, 11 cm, keel view

Amaltheus stokesi without keel, 11 cm, keel view

This pathology is still a mystery. What is hidden on the other side, still in the rock ?
Is is a forma aegra juxtacarinata, i.e. the keel has been dislocated to the (invisible) flank ?
Or is it a forma aegra circumdata, i.e. the keel is just not there ?
One of these days I will prep a window into the back of the matrix and see for myself…

AndyS

Literature :

Helmut Keupp : Atlas zur Paläopathologie der Cephalopoden, Berliner Paläobiologische Abhandlungen Band 12 – Berlin 2012