Robert´s Hammatoceras – a Yorkshire first ?

After I had met Robert for the crinoid & starfish block (see here), he also showed
me an ammonite he had found at Blea Wyke in situ on facebook :
Hammatoceras ammonite in situ, picture courtesy of R. Taylor

Hammatoceras ammonite in situ,
picture courtesy of R. Taylor

It came from the Grey Sandstone beds of the Grey Sandstone member of the upper lias,
?dispansum Zone.

We had briefly discussed it over facebook and consensus was that it could be a
Hammatoceras. I offered to prep it as well, price as usual – a photo for the book.
Unfortunately we had at that time already left Yorkshire again, so Robert posted
the ammonite to me, and after arrival  I could confirm that it is actually a
Hammatoceras.

I took a good look and did some exploratory prep of the inner whorls on one side.
Unfortunately it did not look so good, no inner whorl became visible, there were
only slight brown discolorations so I put it on side for a while.

All literature available to me did not mention any Hammatoceras from Yorkshire
so I contacted the Zoé Hughes, curator for ammonites at the NHM,
and Crispin Little, senior lecturer at Leeds University who had a project
cataloguing some finds of a student of his from the Ravenscar area,
but both confirmed they had not seen a Yorkshire Hammatoceras.

So when the time came to do the final prep on the ammonite
(I had promised to give it back to Robert this summer 🙂 ),
I decided to check the other side, where a part of the inner whorl was visible.

Hammatoceras ammonite as found, picture courtesy of R. Taylor

Hammatoceras ammonite as found,
picture courtesy of R. Taylor

Since most of the outer whorl on this side was eroded away, it was an easy decision to
remove the remnants of the outer whorl, bowling it out so it could still be seen from
the other side.

After about 10 hours total this is how it looks now :

Hammatoceras cf. semilunatum, 10 cm inner whorl

Hammatoceras cf. semilunatum, 10 cm inner whorl

It was relatively difficult to prep, what is preserved of the shell is mostly sideritic, at the
surface probably converted to limonite,  but overall very soft and brittle. The innermost
whorls are mostly not there.

But at  it´s still a very nice and especially rare ammonite – looks like a Yorkshire first !
Hammatoceras cf. semilunatum, 15 cm, keel view

Hammatoceras cf. semilunatum, 15 cm, keel view

Diameter of the inner whorl is 10 cm, including the crushed outer whorl it is about 15 cm.
I would tentatively put this towards Hammatoceras cf. semilunatum (QUENSTEDT, 1885)
– it has about 46 ribs on the whorl, and an umbilical width of about 30 %, which fits nicely.

Congratulations to Robert on this rare find – just goes to show what still can be found by
persistent collecting and a bit of luck !

And of course thanks very much for the opportunity to prep & photograph this ammonite !

AndyS

Addendum :
It looks like it was not actually the first Hammatoceras found in Yorkshire 😦 – Tate & Blake mention finds by Wright and Leckenby (from the Holderness coast), Wright describes finds from both the Grey and the Yellow sandstone beds at Ravenscar, but does not figure them. Since none of the newer literature mentions this, these finds may have either not been entered into a collection, lost or insufficiently documented.

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

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

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

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

It’s all in the umbilicus (and in the provenance) – Pseudolioceras

Pseudolioceras lythense, 7.5 cm, phragmocone only

Pseudolioceras lythense, 7.5 cm, phragmocone only

Pseudolioceras boulbiense, 7 cm

Pseudolioceras boulbiense, 7 cm

Pseudolioceras is a relatively common ammonite with 2 to 3 Yorkshire species, with P. lythense from the bifrons zone (commune & fibulatum subzones) being considered the ancestor of the later, thouarsense zone (striatulum and above subzones) P. boulbiense.

P. subconcavum is at the moment considered to be a synonym of P. lythense but may also be an early form from lower in the commune subzone –
more zonally aligned material is needed for a statistically safe distinction.
The holotype of “P. subconcavum”, which can be seen at Whitby museum, differs from P. lythense in having thicker whorls and deeper furrows along the keel.
This form seems to be relatively rare – I may have a very small one in my collection, but as with most small non-adult ammonites,
this identification is really more wishful thinking than fact – I will not post it here, for a good picture see the excellent Whitby museum type & figured fossils catalog web page for this ammonite at

http://www.whitbymuseum.org.uk/type/grp04/sim214.htm

Large, complete, uncrushed specimen of Pseudolioceras are rather rare due to the apparent fragility of the body chamber –
most of the time you find only specimen with an uncrushed phragmocone and a crushed body chamber

Pseudolioceras lythense, 10.5 cm, with mostly intact body chamber

Pseudolioceras lythense, 10.5 cm, with mostly intact body chamber

 

Telling the difference between P. lythense and P. boulbiense is really rather simple and apart from the umbilicus also involves the bed and location you found it.

The following probabilities give some kind of a guideline :

  • If it´s above 7 cm, it is more likely to be a P. lythense – P. boulbiense above this size is rare.
  • If you found it in a striatulum subzone nodule at Ravenscar, it is most likely P. boulbiense
  • If you found it anywhere else other than Ravenscar it is most likely to be P. lythense
    since the striatulum subzone is only really well exposed at Ravenscar – of course there may be exceptions.
  • If you find it together with other ammonites of the same species, or even ammonite of other species, it is most likelyP. boulbiense.
    This is really somewhat obvious considering the previous critera – P. lythense is most often a “one ammonite per nodule” find,
    as they typically are in the alum shales (I can’t really remember if I have ever seen a Pseudolioceras lythense with another ammonite, I’m sure there must be some…)
    whereas P. boulbiense occurs most often associated with other specimen of the same species, sometimes even dozens or Grammoceras or even the odd Nodicoeloceras.
Pseudolioceras boulbiense loves company : Small Nodicoeloceras (2 cm) sitting on top of 5.5 cm P. boulbiense + severall small Pseudolioceras

Pseudolioceras boulbiense loves company : Small Nodicoeloceras (2 cm) sitting on top of 5.5 cm P. boulbiense + severall small Pseudolioceras

The U/D ration (width of umbilicus / diameter of shell) is usually smaller with P. boulbiense, with P. lythense´s wider umbilicus (with quite some variation) you can usually see more of the inner whorls when you look into the umbilicus as with P. boulbiense, where the inner whorls are just to be seen as a thin ledge inside the umbilicus, with the 7 cm specimen shown above, the width of this ledge is just 1 mm.

Pseudolioceras lythense, 7.5 cm, extra wide umbilicus, probably fibulatum subzone

Pseudolioceras lythense, 7.5 cm, extra wide umbilicus, probably fibulatum subzone

Pseudolioceras boulbiense, 4 cm, showing beveled umbilical wall and suture

Pseudolioceras boulbiense, 4 cm, showing beveled umbilical wall and suture

The umbilical walls of P. boulbiense are just slightly beveled, visible best with smaller specimen, whereas the umbilicals walls of P. lythense are vertical or even undercut.

Comparison of umbilici for P. lythense (left) and P. boulbiense (right)
Comparison of umbilici for P. lythense (left) and P. boulbiense (right)

Ribbing is also different, with P. lythense the ribs visibly swing forward towards the venter, whereas with P. boulbiense, you have to look very hard to see that –
the ribs “stop” more abruptly before the venter, there is only a hint of a rib swinging forward.
You can see this best in a direct comparison :

Pseudolioceras lythense, showing ribs swinging forward at the venter

Pseudolioceras lythense, showing ribs swinging forward at the venter

Pseudolioceras boulbiense, ribs do not visibly swing forward at venter

Pseudolioceras boulbiense, ribs do not visibly swing forward at venter

I’ve been prepping lots of Pseudolioceras these past few weeks – as so often, looking at ammonites again for research of a blog post,
I found the preparation of my specimen of this genus, some of which have already spent more than 20 years in the drawer,
somewhat lacking and not up to what I today regard as my standards for preparation.

And I can tell you, there’s nothing better than prepping for getting “close” to the fossils and understanding their morphology and species differences –
slowly peeling it out of the encapsulating rock makes it easier to capture and understand the essence of the ammonite.

AndyS

Transitions or A late “straight-fingered” survivor on an upper toarcian bed of belemnites ?

Dactylioceras (Orthodactylites) cf. semiannulatum, as found

Dactylioceras (Orthodactylites) cf. semiannulatum, as found

This 7 cm ammonite sits above (or below ? – I have found no indication like e.g. a fossilized level that would allow this decision) a bed of belemnites and was found
at Hawsker March 13, 2008. The matrix around the ammonite was full of brownish-black glistening fragments of what I assume are belemnite hooks.
I seem to remember that the ammonite was not visible initially, and that I split the rock to make it smaller for the sole purpose of grinding and polishing the beautiful other side of the rock displaying the belemnite sections – the entry in my little red book seems to corroborate that – I found very little else on that day and must have been desperate 😉
It shows again you sometimes need to look in unusual places to find something special…

Block with belemnites from other side

Block with belemnites from other side

 

This matrix almost shouts “falcifer” zone, more specifically this could be from a belemnite accumulation usually associated with the ovatum band of the upper falciferum subzone, although this is only an educated guess, since the matrix block was found ex situ and could also come from a slightly lower bed. It´s composition and appearance, however, matches very well with one given in the paper : DOYLE, MACDONALD, 1993: Belemnite battlefields.

Dactylioceras (Orthodactylites) cf. semiannulatum on belemnite block

Dactylioceras (Orthodactylites) cf. semiannulatum on belemnite block

 

What makes this ammonite interesting is that it has some of the characteristics of the Orthodactylites (literally translated from the latin as “straight-fingered”) subgenus of Dactylioceras that I described from the lower toarcian in an earlier post (link) which predominantly have straight, single, usually non-bifurcating ribs, including the classical preservation with “capped” ribs that have a kind of predetermined breaking point, as the outer shell stayed in the negative and took the top of the ribs with it.

 

Howarth described a similar type of ammonite as Dactylioceras (Orthodactylites) semiannulatum in his 1978 paper “The stratigraphy and ammonite fauna of the Upper lias of Northamptonshire”.   It is a late survivor of the Orthodactylites subgenus, in later beds replaced by ammonites with mostly bifurcating ribs of the Dactylioceras genus. I´m hesitant to attribute this specimen to this species, however, since the measurements – apart from the whorl width, which is much smaller – would rather point to Nodicoeloceras. Howarth´s D. semiannulatum specimen were also a bit smaller, though.

There is one other option, which is Dactylioceras consimile (BUCKMAN), of which I´ve got conflicting descriptions/pictures – I need to take a look at one of these in a museum.

 

The conundrum presenting itself of course is a pattern that applies to most of the Dactylioceratidae, especially the lesser known species :

  • You can’t always rely on morphology alone, you need to know the bed from which the ammonite originates to verify the species
    and this can be surprisingly difficult when you mostly collect from the cliff debris, i.e. ex situ
  • There are transitions between the different species, as this probably is. And mutations, pathologies…
  • There is always variation within a species that can not be fully recognized when you look at a small number of specimen.
  • Early descriptions  (BUCKMAN, WRIGHT, SIMPSON…) often relied on single specimen – see above.

 

No clear solution this time, then – I will however label this one, to point out my conviction that this ammonite is closer to D. semiannulatum than to Nodicoeloceras :

Dactylioceras (Orthodactylites) cf. semiannulatum HOWARTH.

 

As promised earlier, the next couple of posts (too much for just one !) will predominantly deal with the upper toarcian Dactylioceratidae – hopefully with less undefined identifications like this one – sorry you had to wait until after the 50th post (which is this one, hurrah !)  – thanks for bearing with me for so long !

 

AndyS

What´s in the egg ?

"Boiling" sea in Robin Hoods Bay - March 23,2013

“Boiling” sea in Robin Hoods Bay – March 23,2013

I know this is kind of silly and it´s also a little late, but the opportunity is just so tempting…

We´ve just returned home from a fortnight’s holiday on the Yorkshire coast,  and most of the time it was bitterly cold and the sea looked
just like on the picture above. This usually is good for fossil hunting, since it turns the beaches around and exposes fresh material,
but can be a little problem at times, when a strong easterly wind keeps you from getting to the locations you want to go, even at low tide.

Anyway, on one of these days I found this little nodule at Bay Ness :

Egg shaped nodule as found with an ammonite just showing, height = 9 cm / 3.5 "

Egg shaped nodule as found with an ammonite just showing, height = 9 cm / 3.5 “

There are some nodules, in which the fossil is just under the surface and some exposure to seas like shown above,
where the nodule is frequently and violently bashed against other rocks, will sometimes break out a little window
showing the fossil inside.

Now when I unpacked my finds yesterday, that little egg of a nodule had to be made into an Easter greeting :

Aegoceras (Androgynoceras) maculatum (YOUNG & BIRD, 1822) , 4.5 cm / 1.75 " diameter

Aegoceras (Androgynoceras) maculatum (YOUNG & BIRD, 1822) , 4.5 cm / 1.75 ” diameter

Happy Easter !

AndyS

 

 

 

 

Recent prep results and What´s in the queue ?

Recent prep results, numbers see text

Recent prep results, numbers see text

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

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

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

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

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

Another article that´s in the “unfinished posts” queue for a long time already is about pathologies on Yorkshire coast liassic ammonites, for the simple reason that
literature about pathologies was somewhat thinly spread across a wide range of publications, most of the time with few pictures (so important for the amateur collector !).
But thanks to Prof. Dr. Keupp from FU Berlin this has now changed (http://www.geo.fu-berlin.de/geol/fachrichtungen/pal/eigenproduktion/Band_12/index.html) :
A brand new copy of his almost 400 page thick, large format, just released new atlas on cephalopod palaeopathologies has landed on my desk, I had only very little time to study it yet, but what I´ve seen so far is
spectacular (pictures galore !) and will surely set the scientific standard on this topic for years to come (unfortunately it is currently only available in german).
So through this new publication my “sick ammonites from Yorkshire” post will take a giant leap forward and will be published after the first part of the Dac post…

AndyS

 

 

 

 

 

 

 

 

 

A moment frozen in time, part II

In the first part of this blog post I described the Yorkshire liassic crinoids, now´s the time to show you the starfish.
It feels like starfish are even a bit more rare than crinoids – at least with crinoids you get the obvious isolated segments (ossicles) in most sediments.
Disarticulated starfish remains are less obvious, though I guess they must be there as well, most Yorkshire lias sediments are just difficult to prepare for microfossil analysis.
Most articulated starfish remains in my collection are from the figulinum – stokesi subzones of the Yorkshire coast, as are the first three.

Palaeocoma milleri (PHILLIPS,1829)
This is the most “common” brittle star from the Yorkshire coast and can reach considerable size – my largest specimen has an arm length of 6″ / 15 cm –
 “Yorkshire” seas also fed the brittle stars better 😉 – Dorset specimen of the same species are usually considerably smaller.
(In his 1964 revision of the brittle stars of the british jurassic (“Die Ophiuren des Englischen Jura”) HESS sums some davoei/margaritazus zone
Palaeocoma species  (P. egertoni, P. gaveyi) under one species P. milleri.)
Palaecoma milleri, 9 cm diameter

Palaecoma milleri, 9 cm diameter

This one was found in a fresh cliff fall on a block of softer sediment, sensitive to both drying out/cracking and falling apart when subjected to water.
Mike Marshall kindly dry-cut the block to size and stabilized it with some epoxy putty. Having thus safely arrived home, a couple of minutes of
air abrading brought the winding arms of the 9 cm diameter brittle star to light.
Palaecoma milleri, width of view = 24 cm

Palaecoma milleri, width of view = 24 cm

Palaecoma milleri, detail of center

Palaecoma milleri, detail of center

This is the said large specimen of Palaeocoma with the arm length of 15 cm (stretched out)  and an “arm span” (as embedded) of more than 22 cm.
The long arms sink deep into the thinly bedded sandstone with harder and softer layers, with the very tips less than 0.5 mm thick.
This fossil was prepped with alternating runs of air pen (for breaking through the harder layers) and air abrader (for the detailed work around the fossil).
There is a little curiosity at the missing arm (5 o´clock position) : There is a small very thin little arm seemingly coming out of the stump, it is tempting to assume
it could be a replacement arm (allthough it looks too small for it).
I have not seen any pictures of what replacement arms with brittle stars look like, I you have, please let me know…
Palaecoma milleri, block as found

Palaecoma milleri, block as found

Palaecoma milleri, width of block 22 cm

Palaecoma milleri, width of block 22 cm

This starfish was found in March this year. It sits in a little block about 23 cm wide and was again prepped with air pen / air abrader.
The central disc is about 3.5 cm wide – the arms must have really been long on this one, if they had been preserved…
While prepping it I mistakenly thought the arm in the 4 o´clock position was connected to the end coming up in the 5 o´clock position – they are not,
as I had to notice when finding that the arm in the 5 o´clock position grew thinner while it was going down, instead of thicker to connect with the other arm…
The embedding rock seems to originate from beds around the oyster bed, showing some oysters as well.
Palaecoma milleri, width of view approx. 20 cm

Palaecoma milleri, width of view approx. 20 cm

Recent brittle stars are known to gather where there is a large supply of nutrients, i.e. in the deep sea on decaying whale carcasses.
This picture shows a section of a larger slab that contains such a fossilized gathering – the reason for it is not known (I can safely say it wasn´t a whale, though…)
The slab was found in 1999 on the way back from a long day out at Hawsker (I told you, it always happens to me like this…);
as the tide came in already, it had to be left on the beach and was hidden in a secretively marked spot.
After a very restless night and anxiously awaiting the next low tide, the 40 kg slab was carried back to Robin Hoods Bay in a large Rucksack and carried up the hill in a fishermen´s box with the help of my friend Klaus…
The reddish covering sediment was found to be preppable using potassium hydroxide (KOH) pellets, and over the course of some months
it was treated in a large cement tub. It is now awaiting finishing touches in a big enough air abrading chamber (planned for 2013…)
The slab had an eroded Amaltheus stokesi on the back, so it must originate from the stokesi subzone.

Tropidaster pectinatus FORBES, 1850
Tropidaster pectinatus, 4 cm wide

Tropidaster pectinatus, 4 cm wide

This small starfish sits on the same slab as the Palaeocoma specimen of the last picture. It is only relatively small (4 cm diameter) and very fragile.
While looking at some photographs of the slab some time ago, I notied a second Tropidaster specimen on the slab as well which I had not seen when looking at it with the “naked” eye…

Luidia murchisoni (WILLIAMSON, 1836)
This is the elusive sun starfish. I have only ever found one specimen myself, but could not salvage it without risk (huge block, last day of the holiday…)
I notified a local collector who had it cut out of the block with a diamond still saw and had it prepped professionally ,it is now on public display in a shop in Robin Hoods Bay.
Luidia murchisoni in situ (center), to the right the snout of dear beach dog Lucy

Luidia murchisoni in situ (center), to the right the snout of dear beach dog Lucy

As a surrogate, here´s an eroded specimen I got off Mike Marshall :
Luidia murchisoni, 10 cm diameter

Luidia murchisoni, 10 cm diameter


?Sinosura sp.
 
Bilder kl. brittle stars
The small brittle stars associated with the Hispidocrinus scalaris crinoid I showed you in the previous post are just too small to be identified – a little over 1 cm diameter.
I have tentatively put them towards Sinosura, since larger specimen of Sinosura have been found with these crinoids.
?Sinosura sp., 1 cm diameter

?Sinosura sp., 1 cm diameter

?Sinosura sp., 1 cm diameter

?Sinosura sp., 1 cm diameter

These tiny little brittle stars are preserved so life-like, with even some of the finest hairs still attached, truly a moment frozen in time.

Addendum November 25, 2012 :

I´ve recently had the opportunity to prep a beautifully preserved P. milleri which is, unlike all the other P. milleri shown here before (did you notice ?) not prepped in oral aspect (from the underside),
but in aboral aspect (like you would see it crawling around in and over the sediment). It is perfectly preserved and could be teased out of the relatively soft shale with low air abrader pressure in about 45 minutes.
Congratulations to the finder (D. Clark) and thanks again for letting me picture it here !

Brittle star Palaeocoma milleri, width approx. 20 cm, collection D. Clark

Brittle star Palaeocoma milleri, width approx. 20 cm, collection D. Clark

AndyS