Pleuroceras – the other amaltheid ammonite

Pleuroceras paucicostatum, 90 mm, Hawsker Bottoms

Pleuroceras paucicostatum, 90 mm, Hawsker Bottoms

The Yorkshire ammonites of the genus Pleuroceras have for some reason given me more
of a headache than other genera (not as much as the Aegoceras/Androgynoceras though !),
over the years I’ve made multiple attempts to get my head around the differences between
the species, but only the most recent and most thorough attempt has resulted in an
understanding satisfactory to me. At first glance, the species seem to be very similar, and
only when you dig deeper into morphological measurements such as rib count, relative
whorl height/breadth and most importantly, their stratigraphical position and  appearance
of their surrounding matrix, their differences and development become clear.

As M.K. Howarth noted in his 1958 monograph about the Amaltheidae, some of the
species appear to have evolved in Yorkshire and therefore, transitional specimen are
common, which adds to the difficulty distinguishing some of them.

The following species occur in Yorkshire :

  • P. solare
  • P. solare var. solitarium
  • P. apyrenum
  • P. hawskerense transient elaboratum
  • P. hawskerense
  • P. paucicostatum
  • P. birdi

For completeness, I’ve added one more species, which does occur in Britain,
though due to a non-sequence in the relevant beds, not in Yorkshire :

  • P. salebrosum
There potentially is a small overlap between genera Amaltheus and Pleuroceras,
but again it is  relatively unlikely to find those genera together due to a non- sequence,
i.e. missing beds in Yorkshire – find a list of all Amaltheus and Pleuroceras species and
the bed numbers for Hawsker Bottoms (compiled from Howarth 1958, Page 2004)
below :
Occurrence of Amaltheidae in Yorkshire

Occurrence of Amaltheidae in Yorkshire

This post also took longer to create due to the fact that I re-prepped a large portion of
the specimen, which predominantly have been found more than 10 years ago – that´s
not to say that chances to find specimen like these are lower today for most species,
though probably in no way as good as they were when M.K. Howarth wrote his
Amaltheidae monograph in 1958.
I had tried to air abrade a specimen that had a lot of fractured and torn light brown
shell and the result was so convincing (and addictive) that I did most of the specimen
in my collection.  Here is an example of the transformation :
Pleuroceras paucicostatum, 60 mm, before and after air abrading with iron powder

Pleuroceras paucicostatum, 60 mm, before and after air abrading with iron powder

But let´s get to the description of the different species, ordered more or less in ascending stratigraphical order.

Pleuroceras solare (PHILLIPS)

Pleuroceras solare, 80 mm, Hawsker Bottoms

Pleuroceras solare, 80 mm, Hawsker Bottoms

Pleuroceras solare for me is a rare species – I´ve only got one in my collection,
and I´ve only realized I´ve had it during the research for this post.
It is significantly bigger than the neotype shown by Howarth, which added to
the difficulty in correctly assigning it. Preservation is markedly different from all
the other species, most significantly the matrix it is embedded in is oolitic,
typical for Hawsker bed 25, and the internal mould is preserved in
light brown / light grey calcite.
Pleuroceras solare, detail of ribs & keel

Pleuroceras solare, detail of ribs & keel

Ribs are sharp and swing forward at the edge of the venter, they do not meet the even
on the internal mould strongly crenulated keel, smooth areas at the side of the keel
remain. On the bigger outer whorls of this specimen the ends of ribs at the are slightly
heightened.
Rib density appears to be relatively constant, the cast of the neotype I´ve procured
from GeoEd (see also here) has the same 28 ribs as myspecimen at almost double
the size.
Pleuroceras solare, 40 mm, cast of neotype, Hawsker Bottoms

Pleuroceras solare, 40 mm, cast of neotype, Hawsker Bottoms

Perceived rarity of these ammonites may also have something to do that Hawsker
bed 25, the “Pecten Seam” is only about 40 cm thick – my find did not come from
in situ, note to myself : Goal for 2016 = find bed 25 in situ…

 

Pleuroceras solare (PHILLIPS) var solitarium (SIMPSON)

Pleuroceras solare var. solitarium, 41 mm, Kalchreuth/Germany

Pleuroceras solare var. solitarium, 41 mm, Kalchreuth/Germany

This ammonite, though it should occur in Yorkshire, has not (yet) been found by me,
so I´ve procured a specimen from the german Kalchreuth quarry.
The only difference between this one and P. solare is that the var. solitarium has
larger tubercles on the inner whorls, and therefore a lower rib density up to 25 mm.
A specimen in the Whitby museum is displayed here :
http://www.whitbymuseum.org.uk/type/grp11/wm500.htm

 

Pleuroceras paucicostatum HOWARTH

Pleuroceras paucicostatum, 80 mm, with slight pathology, Hawsker Bottoms

Pleuroceras paucicostatum, 80 mm, with slight pathology, Hawsker Bottoms

P. paucicostatum has less dense ribs than P. hawskerense, especially visible on
the inner whorls. Ribs are straight and strong, there is a sharp bend forward
at the edge of the venter, the keel is strong and almost smooth on the internal
mould. Especially on the inner whorls the ribs are a little thicker and slightly
raised on both ends.
I my collection this appears to be the most common species, but I´m sure this
is due to severe collecting bias – once you know what nodules from Hawsker
bed 33 look like, and that they often contain ammonites, you´re more likely
to look for them again…
Detail of Pleuroceras paucicostatum, showing sutures and ribbing

Detail of Pleuroceras paucicostatum, showing sutures and ribbing

 

Pleuroceras birdi (SIMPSON)

I have not yet found P. birdi, which is very similar to P. paucicostatum in everything
except whorl breadth – the whorls of P. birdi are significantly thicker.
Only 2 specimen were known at the time of writing of Howarth´s monograph,
one from Hawsker Bottoms, one from Raasay.
The holotype is in Whitby museum (WM278) and can be seen on their website at

I have to look at that specimen “live”, from the picture there appears to be a bit of a
bend at about 1 o´clock in the shell and a successive increase in whorl thickness –
a possible parasitic growth on the shell and  potential cause of a forma aegra augata ?
The specimen seems to be preserved on one side only, the other side appears
to be eroded – if indeed the specimen is pathological, a possible structural
compensation cannot be estimated.

 

Pleuroceras salebrosum (HYATT)

Pleuroceras salebrosum, 60 mm, Holderness Coast (coll. A. Tenny)

Pleuroceras salebrosum, 60 mm, Holderness Coast (coll. A. Tenny)

Pleuroceras salebrosum is unlikely to occur in Yorkshire – both the transiens and
salebrosum zonules appear to be missing in the beds (PAGE 2004).
Nevertheless, a magnificent specimen has been found by A. Tenny
(superb prepwork by M. Marshall) on the Holderness coast – it´s pre ice age origin
is unclear.
Many thanks to Andy Tenny for letting me photograph this great specimen.

 

Pleuroceras apyrenum (BUCKMAN)

Pleuroceras apyrenum, 81 mm, cast of holotype

Pleuroceras apyrenum, 81 mm, cast of holotype

I´ve shown the GeoEd cast of the holotype before,  the main reason to procure
this cast was of course to verify identification of my Hawsker specimen
of P. apyrenum. Over the 27 years of collecting on the Yorkshire coast,
not many specimen of P. apyrenum have found the way into my collection,
and it is the Pleuroceras species I´ve had the most trouble of getting it
identified to an acceptable degree of probability.

With P. apyrenum, there appear to be 2 variants; one where the ribs get reduced
to a fine striation from up to 30-40 mm, and another one where this does not
happen, like in the holotype. I have so far at Hawsker only found specimen up
to 60 mm and a large fragment, where no reduction of the ribs takes place,
and some smaller specimen with an early reduction of ribs.

Measurements of P. apyrenum specimen

Measurements of P. apyrenum specimen

All specimen have been measured and fall into the variation breadth of P. apyrenum.
One specimen is somewhat closer to Pleuroceras quadratum, especially to the
specimen on table VIII, 4a,b which unfortunately has no measurements listed in
Howarth´s monograph and was not available as a cast.

Some of the specimen are also available on GB3D at http://www.3d-fossils.ac.uk/,
a great initiative making museum specimen available as high-resolution 2D and 3D
pictures.

At the moment I´m not totally convinced that P. quadratum is only occurring outside
of Yorkshire, or for that matter that some of the specimen listed in Howarth´s
monograph  as P. quadratum should not really be P. apyrenum.

A note for my continental readers who wonder about what P. apyrenum looks like in the UK –
the continental “version” of the same age indeed looks slightly different,
and often develops tubercles which are unknown in the Yorkshire population.

 

Pleuroceras hawskerense (YOUNG & BIRD)

Pleuroceras hawskerense, 107 mm

Pleuroceras hawskerense, 107 mm

The Hawkser Pleuroceras – an iconic ammonite, evolved in Yorkshire – so truly
born and bred Yorkshire !
P. hawskerense has characteristic densely ribbed inner whorls, strong radial
ribs and a stong keel, rib density is always bigger than P. paucicostatum apart
in large body chambers of both species. P. hawskerense is best preserved in
bed 42 (shown here (link)) and 43 at the top of the hawskerense subzone,
the specimen pictured above is from bed 43.
These beds, especially bed 43, where exposed, have been more or less exploited
over the centuries, so that well-preserved new finds are rare.

 

Pleuroceras hawskerense (YOUNG & BIRD) transient elaboratum (SIMPSON)

 
Pleuroceras hawskerense transient elaboratum, 82 mm, Hawsker Bottoms

Pleuroceras hawskerense transient elaboratum, 82 mm, Hawsker Bottoms

 
P. hawskerense transient elaboratum, in newer literature just P. elaboratum,
is a Pleuroceras population ancestral to P. hawskerense, specimen have the
same densely ribbed inner whorls, but higher rib density
(30 – 38 ribs instead of 25-30 in P. hawskerense) on whorls of more than
40 mm. Both the specimen in Whitby museum (WM:SIM302) displayed here :
and the specimen in my collection display a slightly sunken in keel on the
outermost whorl.
Pleuroceras hawskerense transient elaboratum, 130 mm, Hawsker Bottoms

Pleuroceras hawskerense transient elaboratum, 130 mm, Hawsker Bottoms

 

Summary of measurements
All measurements for the Pleuroceras species mentioned here, both for the specimen in Howarth´s monograph and the specimen in my collection
can be found here :
Measurements of Pleuroceras species

Measurements of Pleuroceras species

Rib density curves showing the complete variation of the species´rib density based
on ammonite diameter can be found in Howarth´s monograph.

So far this has been the blog post I invested the most work in – both in terms of
re-prepping specimen in my collection, and the amount of research needed until
I myself was happy with the result.
I´ve got a feeling that Pleuroceras is somewhat under-represented in Yorkshire
collections, may be because the ironstone nodules containing the ammonites
can be excruciatingly hard and tough – the name “ironstone” already says it,
I´ve many times given up on large nodules myself.
Therefore they rarely “pop open” with a perfectly preserved fossil, and
subsequently require significant work to prep the fossil – if at all possible,
when the inner whorls are preserved in a single “crystal” of solid calcite.

I hope I´ve shown that the result can be well worth the effort –
Pleuroceras is a stunning ammonite and some species are more or less
unique for Yorkshire.

AndyS

Literature

M.K. Howarth : The Ammonites of the Jurassic Family Amaltheidae in Britain, Palaeontographical Society London, 1958
K.N. Page : Castlechamber to Maw Wyke, North Yorkshire in : British Lower Jurassic Stratigraphy, JNCC Peterborough, 2004

Gemmellaro*´s ammonite – scratch one off the “Wanted” list !

Gemmellaroceras rutilans (SIMPSON, 1843), diameter 40 mm

Gemmellaroceras rutilans (SIMPSON, 1843), diameter 40 mm

 

In May this year, Byron messaged me a picture of an ammonite which had been found
by Ricky at Ravenscar (presumably the side towards Robin Hoods Bay, i.e. Wine Haven),
asking me for an identification.

The small ammonite has a diameter of exactly 40 mm and is preserved as a somewhat
pyritic internal mould on a small block of shelly matrix.

Significantly, this matrix also contains pieces of Pinna bivalves which is usually indicative
of the jamesoni zone, taylori subzone, of the lower lias – so no guessing necessary for
identifying the stratigraphy, which can be a big bonus when identifying ex-situ ammonites
from the Yorkshire coast.

At that point I was prepping another small specimen from this zone with an Apoderoceras
so I figured it had to be the same thing and identified it as such…

A few days later Byron put this ammonite up for sale and (you know me) I could not resist….
The ammonite was picked up from Byron´s shop in Whitby this summer and went home
with me. Usually, ready-for-drawer ammonites like this one queue up on my desk for final
identification and a label.

A few months later, until this weekend in fact, it was still sitting on my desk for
identification…It had turned out that identification was not as easy as I had hoped,
it was not an Apoderoceras, no nodes on the thin ribs, and from the small remaining
bits of shell it looks like the ribs would barely be visible under the shell…

The ammonite at 40 mm diameter is a mostly complete adult, as the crowding of the sutures
suggests, and has about half a whorl of body chamber preserved.

Trifid lateral lobe of the suture (marked L) and crowding of sutures towards the aperature, indicating an adult specimen

Trifid lateral lobe of the suture (marked L) and crowding of sutures towards the aperature, indicating an adult specimen

I had identified a possible match with Epideroceras sociale, especially with the style of
ribbing on the inner whorls, but since Epideroceras is getting much larger and develops
much thicker whorls when adult, this match fell through…

Having about half an hour to kill before lunch would be ready this Sunday,  I was
browsing Howarth´s 1962 “The Yorkshire Type Ammonites and Nautiloids of YOUNG
and BIRD, PHILLIPS, and Martin SIMPSON”, looking for something entirely different
and stumbled across the pictures of Polymorphites rutilans (SIMPSON, 1843)
(now Gemmellaroceras rutilans) on table 15 – a perfect match with the crenelated keel
of my ammonite.

The ribs crossing the venter created a crenelated keel

The ribs crossing the venter created a crenelated venter

I had not had Gemmellaroceras on my list assuming they would only be much smaller
(like Gemmellaroceras tubellum), but reading HOWARTH´s
“The Lower Lias of Robin Hood´s Bay, Yorkshire, and the work of Leslie Bairstow” again,
found that this is indeed the larger species and can be found,
(how blind can one sometimes be…)  explicitly mentioned, in Bairstow bed 530,
associated with Pinna folium…

There is another subgenus which is apparently similar, just stratigraphically slightly
older – Leptonotoceras – in which the lateral lobe of the suture is only split twice
(bifid) instead of three times (trifid) as in Gemmellaroceras – the lateral lobe is trifid
in this ammonite so we´re also clear about this.

So that´s about enough to round up this identification, and it´s also a species that can be
scratched off my “Wanted” list – done !

Scratched off the "Wanted..." list !

Scratched off the “Wanted…” list !

Now let´s see if I have the smaller species of this genus, G. tubellum, hiding in my collection
somewhere…

AndyS

* Gaetano Giorgio Gemmellaro (1832-1904) was an italian paleaontologist and geologist,
founder of the Palermo Geological museum and researcher, among many other topics,
on sicilian pygme elephants. Alpheus Hyatt named the genus after him in 1900, presumably
to reciprocate for an honour which  Gemmellaro had bestowed upon him in 1887 by naming
a permian ammonite genus (Hyattoceras) after him…

Crinoid and starfish travel for a prep and a loan

Crinoid unprepped, picture courtesy of R. taylor

Crinoid unprepped, picture courtesy of R. Taylor

Another fossil travel story – but this time a crinoid and some associated starfish.

The story began when Robert posted a picture of a crinoid he found on the Yorkshire coast
in the Yorkshire Fossil Collectors facebook group. It looked very large and quite interesting,
so I asked him if we could meet when I would come to Yorkshire for our summer holidays
and take a “live” look. We agreed on a date and Robert came visiting with his crinoid,
see a pre-prep picture of it above.

Robert had protected the surface of the fossil with a thin coat of paraloid, but I could
instantly see the potential of this fossil, and also that there might be more in the rock –
starfish !

The surface of the slab was relatively soft, I could scratch it with a fingernail, which is a
good sign that this fossil can be easily prepared using an air abrader with iron powder
as an abrasive. I offered to prep it for Robert without charge and give it back to him on
our next visit to Yorkshire.

Now don’t get me wrong here – I neither do preparation as a business, nor do I encourage
readers to ask me to prep something for them -if I see a fossil that I see potential in and
I’m sure I can prep it well, I will offer to do so. So don’t ask me, I will ask you…

Anyway, Robert agreed to my offer and I took the fossil home to Germany with me at the
end of our holidays.Preparation commenced relatively soon after our return from
Yorkshire and it was as simple as I had hoped, the matrix covering the fossil melted
like butter under the low pressure stream of the abrasive.

When I first directed the abrasive across the crinoid remains, I was somewhat taken
aback because the crinoid arms suddenly appeared in a creamy white when the matrix
and the paraloid covering it were removed – I feared they would be soft crystallized
calcite, but they turned out to be stable and just fine.
Crinoid and starfish prepped
Crinoid and starfish prepped
Additionally, as suspected, the slab also contain the remnants of up to 6 starfish, with
two very decayed ones on top of the crinoid and 4 on the side of it. When most of the
matrix and paraloid was removed, which took about 4 hours of prep time,
I sent some pictures to Robert.

In September, Robert went to the Scarborough Fossil Festival at the Rotunda and
showed the pictures to Dr. Timothy Ewin, senior curator for Echinoderms at the
London Natural History Museum, who, in Robert’s words, got “very exited” seeing
the pictures and asked if he could see more detailed pictures of the crinoid and
of the starfish.

The Rotunda in Scarborough

The Rotunda in Scarborough

I sent some more pictures and an e-mail discussion between the 3 of us ensued with
the result that the crinoid has tentatively been identified as a large Isocrinus robustus
and the starfish needing a detailed inspection on the “live” specimen to identify them.

Since my family and I had planned a visit in London in October anyway,
I offered (of course conditional on Robert’s agreement to do so) to take the specimen
to London for Dr Ewin to see it.

Robert and Dr. Ewin agreed, so I finished the preparation of the specimen in an
additional 2 hours and packaged it very safely for the journey
(I luckily still had some foam left from the Ichthyosaur donation…)

Packaging material
Packaging material
Crinoid ready to go
Crinoid ready to go

The transport was relatively straightforward, of course you get the
“what the heck have you got in there ?” question from the x-ray folks at the airport,
but after opening the case and allowing a swab for explosives,the crinoid went
on the flight to London.

Natural History Museum, London
Natural History Museum, London

Later in the week, we met with Dr. Tim Ewin in the Natural History Museum, and after
a quick inspection we agreed that this was indeed a very complete and large
Isocrinus robustus, and the starfish were not Tropidaster, but maybe Uraster or
something similar but that would require further detailed inspection.

The material is surprisingly similar to the legendary Mickleton tunnel fossils,
which I could see later on in the collections.
Specimen will be on loan to NHM and be given back to Robert, maybe on occasion of the
next Fossil festival ? According to Dr Ewin, there’s  a good chance you might see this
specimen pictured in the upcoming Yorkshire Lias guide…

 

Many many thanks to Robert for entrusting  me with his crinoid, both for the preparation
and the transport to the NHM, it was a pure pleasure to prep. Many thanks to
Dr. Timothy Ewin for keeping the important contact with us collectors and of course
for the tour of the NHM crinoid and starfish collections :)

And the next post will again be an ammonite one, I promise :)

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

 

From wreck to study ammonite or An Inbetweener

On days when I do not find very much, I tend to also take fossils with me that normally
would not be taking,  this wreck of an Amaltheus is such a case,  found in early April this year :

A wreck of an Amaltheus as found - hope for a salvagable inner whorl ?

A wreck of an Amaltheus as found – hope for a salvagable inner whorl ?

I was hoping for a good inner whorl to salvage and may be something subconsciously
registered as  interesting with this ammonite.I prepped the ammonite this weekend
and noticed (apart from it being a rather nice inner whorl) that it does have
rather strong ribbing :

A 7.4 cm Amaltheus stokesi/bifurcus "inbetweener"

A 7.4 cm Amaltheus stokesi/bifurcus “inbetweener”

So a candidate for Amaltheus bifurcus ?

The “Schlegelmilch” lists the variation for ribs/whorl for Amaltheus bifurcus as from
17 to 26,  and this ammonite fits right in there with 25 ribs at 7.5 cm
(Amaltheus stokesi, the other option, has a lot finer ribbing with 31-44 ribs/whorl)

So case closed – or is it ?

The “Schlegelmilch” also list the umbilical width of the ammonites, with
Amaltheus bifurcus at 34-45 %  and Amaltheus stokesi with 25 – 28 % –
and this ammonite has exactly 28 % !

So it looks like this ammonite is something of an in-betweener, a late A. bifurcus or an
early A. stokesi or even a hybrid, since these ammonite species did occur together.

Whatever it is, I´ve had so much fun prepping and wondering about it, that it´s been
really worth taking the chance with the wreck that it was. It´s so much better not
expecting a lot from a fossil and finding a little jewel hiding in there than expecting
a lot and finding it´s a wreck…

AndyS

 

Mostly wishful thinking – Hildaites murleyi

Small 2.5 cm Hildaites murleyi next to a small Cleviceras and a few ammonite aptychi and possibly belemnite hooklets (!)

Small 2.5 cm Hildaites murleyi next to a small Cleviceras and a few ammonite aptychi and possibly belemnite hooklets (!)

When it comes to filling a gap in our collection, we collectors become a bunch of wishful thinkers, easily taking the slightest hint that a specimen might be the sought after species as fact.  Please note that this explicitly includes myself, and I´ve got a feeling it is directly proportional to the time that gap is perceived to be open.

One of my examples in this area is the below ammonite, found in October 2010 at Hawsker Bottoms.
I was so ready to call it Hildaites murleyi, believe me, mainly for the fact that it exhibits a finer ribbing than the usual Hildoceras lusitanicum (see here). But a final niggle remained, the preservation just did not fit – it was a typical commune zone Hildoceras lusitanicum preservation, with a sugary pyrite/calcite shell, that was almost gone, and a pyritic internal mould with some replacement shell.

Finely ribbed 8.5 cm Hildoceras lusitanicum MEISTER from the commune subzone at Hawsker Bottoms

Finely ribbed 8.5 cm Hildoceras lusitanicum MEISTER from the commune subzone at Hawsker Bottoms

Hildaites murleyi is an exaratum/falciferum subzone ammonite on the Yorkshire coast and in my experience relatively rare.
I´ve only really got one Yorkshire specimen I´m 100 % sure of that it is Hildaites murleyi, and it is the one shown in the title picture.
You can´t beat a good ammonite association, even better one that is so diagnostic as the above one : The small ammonites next to the Hildaites murleyi are Cleviceras, this small 10 x 5 cm matrix sliver also has many small shiny black ammonite aptychi and possibly belemnite hooks, which are so typical for certain exaratum subzone beds.

When the opportunity came up to purchase a better sized, verified Hildaites murleyi from well known collector Arno Garbe via eBay,
I just had to take it, even though it is not a Yorkshire specimen, one has to do something to close that burning gap…

It was found at Hildesheim in Germany in the so called “borealis” nodules of the exaratum subzone, Hildoceras murleyi was previously named “Ammonites borealis”
by SEEBACH in 1864. Arno is well known for his craftsmanship in preparing shelled liassic ammonites and this one comes in a beautiful chocolate and
caramel coloured calcite shell:
Beautiful 8.5 cm Hildaites murleyi (MOXON) in a borealis nodule from Hildesheim/Germany

Beautiful 8.5 cm Hildaites murleyi (MOXON) in a borealis nodule from Hildesheim/Germany

Now when you closely compare the two ammonites you can see the difference immediately:

Direct comparison of inner whorls of Hildaites murleyi (left) and Hildoceras lusitanicum (right)

Direct comparison of inner whorls of Hildaites murleyi (left) and Hildoceras lusitanicum (right)

Hildoceras lusitanicum has a much more visible groove , and the smooth area next to the umbilical wall is much wider than in Hildaites murleyi, where the groove is almost non-existent and the ribs don’t fade out towards the umbilical wall – you see the same on the small specimen in the title picture.
Arno´s Hildaites murleyi certainly is a very beautiful (maybe even more beautiful than a Yorkshire specimen can be), well prepared ammonite, and very educational in showing the typical Hildaites murleyi features as well.
But, you know, it´s not from Yorkshire, and it´s not the same as found by myself … I´ll continue looking… :)
(and no, if you were going to ask, I did not get the Hildaites murleyi that Mike -by pure coincidence – posted earlier in his web shop – someone was faster !)

AndyS

 

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

Taking stock – Merry Christmas, but never mind the R, the Y and the I…

Santa is having a small Coroniceras sp. (left) and a Grammoceras thouarsense (right) leaned against his knees. Ravenscar in the background.

Santa is having a small Coroniceras sp. (left) and a Grammoceras thouarsense (right) leaned against his knees.
Ravenscar in the background.

Well, it’s that time of the year again, time for looking back, taking stock…
I often get asked, when the book will be ready…
2014 has been an extremely busy year for me professionally, with the effect that I
did not have much spare time to work on the book, and I’ve been to the UK only once
this year for collecting (strong withdrawal symptoms…).
Nevertheless I tried keeping up the work, doing at least 1 blog post in a month,
photographing and writing, though I’m not entirely happy with the progress,
but what can you do, the money has to keep coming in…and there are also limits,
how much time you can spend on the computer.
Short answer : It will probably take another year to finish all material,
so I need to look at 2016 as a rough estimate for publishing.

On a lighter note, on that one visit we met old and new friends,
photographed some stunning new specimen and became a fan of the lowest of the lias.
It was the 25th year we´ve been coming to Yorkshire and it continues to feel like
home from home, we can´t wait to be back in 2015 (hopefully at least twice !).

I have a few days off now, so I sat down before my drawers and looked for what genera
we have not covered so far (and the names mysteriously arranged themselves in a certain order) :

 

Mucrodactylites
Euagassiceras
Renziceras
Radstockiceras
Yet more :

 

Cymbites
Haugia
Riparioceras (synonym)
Incidentally also :
Schlotheimia (redcarensis)
Tropidoceras
Microderoceras
Angulaticeras
Schlotheimia (angulata)

 

Apoderoceras
Nodicoeloceras (incrassatum/crassoides)
Dactylioceras (the ones we have not covered yet)

 

Agassiceras

 

Harpoceras (subplanatum)
Arietites
Promicroceras
Pleuroceras
Yet more :

 

Nodicoeloceras (puteolum)
Eteoderoceras
Waehneroceras

 

Yet more :
Epophioceras
Androgynoceras
Rakusites (synonym)

 

By now of course you´ve got the message :) and you probably also noticed that
I had to include some that we did in fact cover or might not even occur in Yorkshire
(look in the R´s)and that I did particularly struggle with the I and the Y´s
(there´s just no species names starting with those letters in the lias…)
but there are also some that did not fit in :

 

Liparoceras, Oistoceras :
We´ll have a lot of fun with these, including Androgynoceras, heavy stuff, and a
fellow countryman to thank for that…
Psiloceras, Caloceras, Coroniceras, Vermiceras, Alsatites  :
Some of the earliest lias ammonites, very interesting stuff, but so difficult to ID
when they´re small…
Crucilobiceras, Xipheroceras, Platypleuroceras, Bifericeras, Phricodoceras :
Finally – Spiny, spikey cephalopods !

 

Grammoceras, Phlyseogrammoceras  :
Together with Haugia and Harpoceras subplanatum the last of the Hildoceratidae
we´ll have to cover

 

Epophioceras :
Looks like an Echioceras, but seems to be related more to Asteroceras…

 

Leptechioceras :
A rare, almost smooth  member of the Echioceratinae

 

Catacoeloceras (crassum, raquinianum) :
Real “Fat Dacs” – we´ll have to work out their differences to Nodicoeloceras

 

So you see there´s still a lot to be done, chiefly in the Psiloceratidae, Arietitidae,
Cybitidae, Polymorphitidae ,Liparoceratidae, and we´ll have to finish off the
Dactylioceratidae and the Hildoceratidae – and that of course guarantees
that you´ll see some more blog posts next year !

 

In terms of visitors of the blog, it was another great year, getting close to 40.000
views in total,  about 15.000 this year. In terms of geography I guess by now we´ve
had visitors from most countries with Jurassic deposits, all though readers from
Greenland stubbornly refuse to visit :) :

 

All time visitors by geography - not many white spaces left !

All time visitors by geography – not many white spaces left !

 

Not on the top 22, but all the same : Seasons greetings to a friend reading these pages
doing a gap year in Cambodia.

 

With best wishes for a peaceful, happy time for you and yours, wherever you are.

AndyS

Recognize it, peel it, glue it, bag it or The secret to complete ammonites is knowing when to stop…

Androgynoceras maculatum, 8 cm, split nodule as found. The end part of the body chamber is on the negative part of the nodule and had to be transfered to the positive side.

Androgynoceras maculatum, 8 cm, split nodule as found. The end part of the body chamber is on the negative part of the nodule and had to be transfered to the positive side.

Androgynoceras maculatum, 8 cm, with complete mouth border after preparation

Androgynoceras maculatum, 8 cm, with complete mouth border after preparation

The secret to achieving completely preserved ammonites is – do as little as possible in the field. The highest risk of loosing bits of the ammonite is when you work it with the crudest tool you have : Your hammer !

The ratio of ammonites on the Yorkshire coast preserved completely is relatively high, so here are some clues to increase your success rate of getting them into your collection that way :
  • Recognize it as early as possible : When you find a likely looking nodule, don’t just whack it, instead take your time looking at it from all sides to see if any part of an ammonite is showing. If it does, and the nodule is not too heavy to carry, just bag it and take it home.
  • If there is no outward sign of an ammonite in a likely looking nodule, don’t just whack it to split it through the middle : A perfect split is a very rare thing, and beach prepping is the worst sin an ammonite collector can commit IMHO (and I´m guilty of trying it myself sometimes, but less so in the last years). Instead try to “peel” the ammonite : Whack it very slightly around the edges, splitting off only small amounts of matrix, preferably in shards, turning it while you do so and observe if an ammonite becomes visible after every blow of your hammer. If it does, bag it and take it home
  • And one of the most important advice of all : Stop hammering before the last blow :)
  • Should during this process any part of the ammonite be split off : Do not throw the split off pieces away, even if they seem insignificant, try to glue them back on right away , if it’s a simple break. I carry both liquid and gel type super glue with me for this purpose in my collecting rucksack. I have found that many times the split off piece contained the mouth border, because I misjudged its position in the matrix. Don’t try to glue complex breaks in the field though, instead carefully wrap the broken off pieces and take them with you.
  • Complete the job, when you find a likely looking nodule – don´t stop after the first blow of the hammer does not reveal anything interesting.
    I´ve found many nice ammonites in half nodules that still had plenty of room, but had been left “for dead” by other collectors. It can sometimes also be interesting to split large solitary body chambers of nautiloids or large ammonites looking for smaller, potentially well-preserved, washed in ammonites or even inhabiting crustaceans…
Haugia in discarded nodule after another exploratory blow with the hammer...

Haugia in discarded nodule after another exploratory blow with the hammer…

Prepped Haugia variabilis, 7.5 cm, in 16 cm nodule

Prepped Haugia variabilis, 7.5 cm, in 16 cm nodule

  • Use enough wrapping material so that the pieces don’t rattle against each other in your bag/rucksack/etc. I’m using bubble wrap recycled from used jiffy bags – they make a nice pouch to put your fossil into.
  • Once you are at home, you have all the time in the world to glue any complex breaks, wash the nodule, think about your prep strategy and execute it leisurely. It can sometimes help to mark the position of the ammonite on the outside of the nodule before you glue any pieces back on, especially when the nodule completely hides the ammonite when the pieces are glued back on. Who knows when you will find the time to prep it – until then you might have forgotten what the position of the ammonite is in the nodule.
Nodule with Zugodactylites - approximate position of the ammonite marked before glueing the nodule.

Nodule with Zugodactylites – approximate position of the ammonite marked before glueing the nodule.

Nodule with Zugodactylites braunianus, 8cm, complete with mouth border after preparation

Nodule with Zugodactylites braunianus, 8cm, complete with mouth border after preparation

  • While prepping, try to find  the position of the aperture first. Always prep the outermost whorl following the direction of the aperture, not against the open aperture – you would not be the first one to find you’ve just prepped away the aperture while following the next whorl in the wrong direction…
  • Take your time prepping the specimen. Sometimes, especially when you’re relatively new to prepping, it is better to practise on not so well-preserved specimen, and leave the better preserved ones til later, when you have gained more experience.
Double Ovaticeras ovatum (8 & 7.5 cm) from the core of a septarian nodule. The smaller specimen split off with the wrong side and had to be re-affixed to the matrix after prepping from the other side as well - it was found in 2000 and finally prepped complete in 2014...

Double Ovaticeras ovatum (8 & 7.5 cm) from the core of a septarian nodule. The smaller specimen split off with the wrong side and had to be re-affixed to the matrix after prepping from the other side as well – it was found in 2000 and finally prepped complete in 2014…

  •  It takes time getting used to an air pen, and I’ve ruined many good ammonites because I was too eager to try the new tool…
  • Don’t prep in a rush – it’s no good trying to finish that ammonite in the short timeframe before you need to pick up your kids/lunch starts/your favourite TV series starts etc… I’ve found that my prepping is best when I’m relaxed and my mind is at peace.
  • If there are other faunal elements like bivalves, gastropods, crinoid pieces etc on the piece – leave them there, don´t try to get your ammonite on as little matrix as possible, sometimes these combinations of different types of fossils are much more beautiful (and scientifically interesting) than a single ammonite.
Nodule with 1 Eparietites ammonite and 1 Cardinia bivalve showing after first blow with hammer. The soft nodule would have been obliterated after another blow...

Nodule with 1 Eparietites ammonite and 1 Cardinia bivalve showing after first blow with hammer.
The soft nodule would have been obliterated after another blow…

Nodule with multiple Eparietites ammonites, Cardinia bivalves and a Hispidocrinus crinoid stem, width of nodule 11 cm

Nodule with multiple Eparietites ammonites, Cardinia bivalves and a crinoid stem, width of nodule 11 cm

It only takes a little more care and a little more patience, but it can mean the difference between a mediocre and a great ammonite specimen…
AndyS
Follow

Get every new post delivered to your Inbox.

Join 44 other followers