“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

Frechiella or A nautilus with an ammonite suture…

Frechiella subcarinata (YOUNG & BIRD, 1822), 8.5 cm diameter, Port Mulgrave, with a Dactylioceras fragment and a belemnite phragmocone in the aperture

Frechiella subcarinata (YOUNG & BIRD, 1822), 8.5 cm diameter, Port Mulgrave, with a Dactylioceras fragment and a belemnite phragmocone in the aperture

Frechiella is one of the rarest Yorkshire lias ammonites and in some respects also one of the oddest.

It comes from a so-called “aberrant” line of ammonites, previously thought to come from one subfamily Bouleiceratinae of the family Hildoceratidae,
but nowadays after some more analysis (Rouleau et al 2003) is being split up into the 3 subfamilies Bouleiceratinae (lower Toarcian),
Leukadiellinae (middle Toarcian) and Paroniceratinae (upper Toarcian, including Frechiella) but all still under Hildoceratidae.
All are much more common in the tethyan realm, and are rare “strays” into the north-west european faunal province.
All members show a characteristically reduced, sometimes “ceratitic” suture (named after the triassic ammonite genus Ceratites, which showed a similar suture).
Oxyparoniceras telemachi (RENZ), 2 cm This is a member of the same subfamily, but not found in Britain, but somewhat further south from Barjac in the south of France (and purchased by me).

Oxyparoniceras telemachi (RENZ), 2 cm
This is a member of the same subfamily, but not found in Britain, but somewhat further south from Barjac in the south of France (and purchased by me).

This is also the main diagnostic feature, otherwise one could easily confuse these very involute ammonites with a nautilus , especially when they are wave-rolled –
In fact, Frechiella subcarinata was originally called Nautilus subcarinatus YOUNG & BIRD, 1822 –
you can just believe that, if it weren’t for the very characteristic suture, and I guess some of you might now go checking the nautilus in their collections …
(and of course : Frechiella is an ammonite, not a nautilus !)
Well preserved specimen show a faint keel on a rounded, sometimes slightly rectangular venter, faint radial ribs, sometimes flat waves can be seen close to the umbilicus.
With almost all specimen I’ve seen (and that’s not many…) the body chamber is more or less crushed or imploded.
Frechiella subcarinata (YOUNG & BIRD, 1822), 10 cm, Hawsker Bottoms

Frechiella subcarinata (YOUNG & BIRD, 1822), 10 cm, Hawsker Bottoms

Frechiella subcarinata (YOUNG & BIRD, 1822) , the only Yorkshire species in the genus Frechiella found so far,
occurs only in the main alum shales, commune subzone, bed 54 (HOWARTH 1992).
It is one of the rarest Yorkshire coast lias ammonites, and many regard it as the “holy grail” of upper lias ammonites.
I had for a time almost given up on trying to find one myself, and bought an unprepared specimen, found at Port Mulgrave (the one pictured below the title),
from Mike Marshall in September 2003.
But as it happened – and doesn´t it always happen like this ?!  – a year later in September 2004 one twinkled up at me from the cliff debris on one of my favourite
spots around Hawsker Bottoms – this is the one pictured above – I have not found one since, not even a fragment.
AndyS

You can´t find everything or Buying fossils

Every collector endeavours to make his collection as complete as possible. Whatever your collection object, that goal becomes easier to achieve when you specialize on a certain sub-group. For me, this is ammonites, liassic ammonites, Yorkshire liassic ammonites. I do stray from that path once in a while and get tempted , e.g. when a species cannot be found in Yorkshire at all, for example Prodactylioceras davoei , or can be found in another preservation from another location, like the beautiful white Marston Magna Asteroceras, Xipheroceras and Promicroceras,  but that is really only the exception.

“Yorkshire liassic ammonites” is still large enough a topic to collect a lifetime and not find every species there is to find. Cycles in erosion patterns can mean that certain beds high up in the cliff will only fall every x years, and even then you have to be on the right spot at the right time. Some beds may not be accessible at all anymore, because they have been exploited a long time ago or it is forbidden to collect there anymore.  Some species may be that rare that only very few can be found at all. From the entries in my little red book  I have estimated that from October 1989 until April 2012 I spent 450 days collecting, spending our holidays in Yorkshire. Conservatively estimating 4 hours per day, I get around 1800 hours. Put this together with my other estimate that I´ve achieved to collect about 50 % of the known species so far, then you know what is possible when you do not live close to location…
Does the above all sound very apologetic to you ? OK, I admit it : I do buy fossils, especially ammonites from time to time. Nothing to be ashamed of, really. I´m just human.
When I buy, it´s usually from well-known UK dealers like
(Disclaimer : I do not get or expect any preferrential treatment from these guys to mention them here, so they enjoy a rare spot of free advertisement now !)
Here are a few of the ammonites I bought from them in the past :
Paltechioceras planum, 8 cm, from fossilsdirect

Paltechioceras planum, 8 cm, from fossilsdirect

This beautiful Paltechioceras planum from the Holderness Coast came from fossilsdirect. It is a species that should occur at Robin Hoods Bay as well, but I´ve never found it there yet.
The ribbing on this species is not as dense as on Paltechioceras tardecrescens.
Dactylioceras (Orthodactylites) cf. crosbeyi, 7 cm, from Yorkshire Coast Fossils

Dactylioceras (Orthodactylites) semicelatum, 7 cm, from Yorkshire Coast Fossils

This irresistible (I´m only human !) Dactylioceras (Orthodactylites) cf. crosbeyi came from Yorkshire Coast fossils. Those thick variants of the Dactylioceras (Ortodactylites) genus are ever so rare, this is a particularly nice specimen and also very nicely prepped.
Dactylioceras sp, 8 cm, from Natural Wonders / Fossils UK

Dactylioceras sp, 8 cm, from Natural Wonders / Fossils UK

 This Dactylioceras sp. (we´ll leave it there for the moment, that´s another story !) came from Natural Wonders / Fossils UK. It is a very interesting Dactylioceras variant with strong ribbing,
we think it comes from the ovatum beds and the type of nodule it´s in seem to confirm that- this is one I´d like to check against some museum holotypes.
I do sometimes buy from ebay as well, very occasionally you can get a bargain there, but you have to know what to look for, and bidding for really good stuff can sometimes be fierce, exceeding the price that you would pay in a shop, simply because the group of bidders is global.
AndyS