This is an Asteroceras blakei
SPATH, 1925 from Robin Hoods Bay, found by Keeley and Adrian on the 20th of April, 2011 (guess what, my little red book
told me that…).
They entrusted this 10 cm ammonite to me for the preparation using my air abrader. After securing the remaining shell with a bit of liquid super glue, to stop it from flying away in the air stream (it easily does that by the way) , I prepped it and it came out like this.
Asteroceras blakei SPATH, 1925, 10 cm
But this is not all that this little story is about, it´s more about finding out more about Asteroceras blakei.
I usually at least try to take a look at the original description of the author. As you can see from the name, the original describer of this species, Leonard Frank Spath, did name this ammonite in 1925.
In HOWARTH 2002 the ammonite was pictured and full details were given for the original describer and the year, a list of synonyms (Asteroceras marstonense SPATH is one), some museum references, and, in the references the name of the publication where SPATH described the ammonite :
“Notes on Yorkshire ammonites. The Naturalist, Hull, 1925”. The Naturalist, as I found out, is the periodical publication of the West-Riding Consolidated Naturalists’ Society and, later, the Yorkshire Naturalists’ Union. Some volumes (between 1865 and 1921) can be found at Archive.org :
They´re delightful reading, most is about fungi, lichen, spiders, birds, etc. but sometimes there is something about geology or fossils. If you open one of the volumes in Acrobat reader and search for “ammonite”, in the 1921 volume for example you´ll find some not so pleased remarks on BUCKMAN´s then new nomenclature in his “Yorkshire type ammonites” or the prohibitive cost of printing for some of his volumes, in the 1909 volume a short arcticle about “The ammonites called A. serpentinus”, some species of the Harpoceras genus, including a picture of the giant Harpoceras (then called H. mulgravium) that is now exhibited in Whitby museum. But no luck with the 1925 volume…
I sent out severall calls of help to the various forums I visit, but first to no avail. I had almost given up, when after almost 5 months later out of the blue I received a note from Dr. Rene Hoffmann, from the Ruhr University at Bochum, sending me copies of the two pages describing Asteroceras blakei – thanks again for that !
So here is that first picture of Asteroceras blakei SPATH, 1925 :
Asteroceras blakei, the original picture from “The Naturalist”, 1925
But that´s almost all that SPATH writes about this new species – I must admit I was somewhat underwhelmed for all the trouble it took to find this description !
Thanks of course to Keeley and Adrian, for letting me borrow, prep & photograph the ammonite !
Posted by andysfossils on June 27, 2012
Microderoceras birchi, width of view 4 cm
A Microderoceras birchi, shell fully preserved, with a tiny little ammonite sitting on one of the spines.
The most difficult way to prep an ammonite is to try to keep its shell on – making it look almost like it used to when the animal was still alive. The ability to do so of course depends on a few things. First and foremost : The shell has to be preserved (obvious). Then there has to be a way to separate shell and matrix without the internal mould inside the shell separating from the shell first. For this to be possible there are a few conditions :
- The shell has to be relatively solid
- There has to be a difference between matrix and shell, be it in terms of hardness or chemistry
- There has to be a way to use this difference to remove the matrix without damaging the shell too much.
For shell preserved ammonites in soft clays, washing and brushing is the easiest version where these conditions are true. The only problem is : None of the beds in the Yorkshire liassic are soft clays…
Most shell preserved ammonites in Yorkshire come from more or less hard nodules that formed around the decaying animal. With some of the nodules, especially from some beds in the upper sinemurian, it is the hardness difference between shell and nodule that can be used to extract an ammonite with shell more or less intact.
Generally ammonite shells are most commonly preserved in calcite that was transformed from the original aragonite. Calcite has a Mohs hardness (a relative scale of hardness from 1 to 10 with diamond being 10) of 3 – not really all that much, considering that the steel of a chisel or a prep needle has a Mohs hardness of between 5.5 and 6.5.
So using a prep needle, you can scrape softer matrix off the shell, but you will always scratch it more or less, depending how careful you work.
In recent years, air abrasive techniques have become affordable for collectors, in essence shooting small abrasive medium particles at the fossil using a compressed air stream, like a million tiny needle-pricks. The elegant thing about air abrasive technique is that you can (within boundaries) tailor your air abrasive medium to the hardness difference between matrix and fossil. A more commonly used abrasive medium is iron powder with a hardness of about 4, but almost anything is possible e.g. walnut shell powder , glass, aluminium oxide. Iron powder is quite popular in Germany because it is just slightly harder than calcite (it will “smear” ammonite shell just a bit) but harder than most soft shales, or oolithic sediments with a high silt content, is relatively cheap, and quite recyclable, i.e. you can re-use it many times. Another quite commonly used medium is aluminium oxide which you can use on harder matrices like limestone nodules as well, but with a Mohs hardness of 9, it will easily shoot holes through your fossil if you’re not really careful.
Here are some more examples of what can be done using iron powder air abrading:
Angulaticeras sulcatum, 7 mm
Asteroceras obtusum, 6 cm
Gagaticeras neglectum, 5 cm
Microderoceras birchi, width of view 4 cm
Oxynoticeras simpsoni, 5 cm
Gagaticeras sp., encrusted with tubeworms, 5 cm
When there are chemical differences between fossil and matrix they can sometimes be used to prep fossils as well – which we’ll explore sometime later…
Posted by andysfossils on June 24, 2012
Every collector endeavours to make his collection as complete as possible. Whatever your collection object, that goal becomes easier to achieve when you specialize on a certain sub-group. For me, this is ammonites, liassic ammonites, Yorkshire liassic ammonites. I do stray from that path once in a while and get tempted , e.g. when a species cannot be found in Yorkshire at all, for example Prodactylioceras davoei
, or can be found in another preservation from another location, like the beautiful white Marston Magna Asteroceras, Xipheroceras and Promicroceras
, but that is really only the exception.
“Yorkshire liassic ammonites” is still large enough a topic to collect a lifetime and not find every species there is to find. Cycles in erosion patterns can mean that certain beds high up in the cliff will only fall every x years, and even then you have to be on the right spot at the right time. Some beds may not be accessible at all anymore, because they have been exploited a long time ago or it is forbidden to collect there anymore. Some species may be that rare that only very few can be found at all. From the entries in my little red book
I have estimated that from October 1989 until April 2012 I spent 450 days collecting, spending our holidays in Yorkshire. Conservatively estimating 4 hours per day, I get around 1800 hours. Put this together with my other estimate that I´ve achieved to collect about 50 % of the known species so far, then you know what is possible when you do not live close to location…
Does the above all sound very apologetic to you ? OK, I admit it : I do buy fossils, especially ammonites from time to time. Nothing to be ashamed of, really. I´m just human.
When I buy, it´s usually from well-known UK dealers like
(Disclaimer : I do not get or expect any preferrential treatment from these guys to mention them here, so they enjoy a rare spot of free advertisement now !)
Here are a few of the ammonites I bought from them in the past :
Paltechioceras planum, 8 cm, from fossilsdirect
This beautiful Paltechioceras planum from the Holderness Coast came from fossilsdirect. It is a species that should occur at Robin Hoods Bay as well, but I´ve never found it there yet.
The ribbing on this species is not as dense as on Paltechioceras tardecrescens.
Dactylioceras (Orthodactylites) semicelatum, 7 cm, from Yorkshire Coast Fossils
This irresistible (I´m only human !) Dactylioceras (Orthodactylites) cf. crosbeyi came from Yorkshire Coast fossils. Those thick variants of the Dactylioceras (Ortodactylites) genus are ever so rare, this is a particularly nice specimen and also very nicely prepped.
Dactylioceras sp, 8 cm, from Natural Wonders / Fossils UK
This Dactylioceras sp. (we´ll leave it there for the moment, that´s another story !) came from Natural Wonders / Fossils UK. It is a very interesting Dactylioceras variant with strong ribbing,
we think it comes from the ovatum beds and the type of nodule it´s in seem to confirm that- this is one I´d like to check against some museum holotypes.
I do sometimes buy from ebay as well, very occasionally you can get a bargain there, but you have to know what to look for, and bidding for really good stuff can sometimes be fierce, exceeding the price that you would pay in a shop, simply because the group of bidders is global.
Posted by andysfossils on June 24, 2012
This is my little red book. I use it to keep track of all the finds I make during a collection day. Not when I´m out in the field (my memory is not that bad yet), but when I unwrap the fossils in the evening. I jot down the date, every fossil I found, it´s size, where I found it, any further interesting facts, since March 1991.
My little red book
In the last couple of years, after digital cameras became affordable, I´ve also made a picture of every fossil I have found to keep a photographical record of what the fossil
looked like before I prepped it. When later you have to e.g. remove the matrix of the fossil for whatever reason, you can still reconstruct what it looked like originally.
Digital pictures cost nothing unless you have them printed, so I have a database of fossil pictures on my PC´s hard drive (and I do backup regularly).
Digital pictures also do have the nice feature to tell you their “date of birth”, i.e. the creation date of their file from their so called “exif” (for exchangable image file format) data. If you set the date on your camera correctly (!), you can use this information embedded in the picture to “find” every picture you made on a specific date on your computer´s hard disk. Together with the notes from my little red book, that makes it very easy to later on put the right information on the label of the fossil in the collection.
And since I know that you like those before / after prep photos, here are two sets of them…
Crucilobiceras densinodulum, as found
Crucilobiceras densinodulum, prepped, 5.5 cm
This Crucilobiceras densinodulum was found on July 13, 2008 at Boggle Hole.
Amaltheus margaritatus, as found
Amaltheus margaritatus, prepped, 7 cm
This Amaltheus margaritatus was found on March 29, 2012 at Hawsker Bottoms
Posted by andysfossils on June 20, 2012
The title of this article is not only part of the conlusion of Charles Darwin´s “On the Origin of Species…”, (and derived thereof the title of Sean B. Carrolls excellent book on “Evo Devo”),
but also very true for the next group of ammonites I´d like to show you : The genus Polymorphites.
The name says, translated, “of multiple form”, and this alludes to the large variety of species / intra-species variation in this genus.
Polymorphites polymorphus , intermediate form, 2 cm
Polymorphites polymorphus lineatus, 1,8 cm
Polymorphites polymorphus interruptus, 1.8 cm
I´ve followed HOFFMANN 1982´s naming of the ammonites as subspecies. These are just the ones I could relatively easily put a name to since their relatively characteristic representatives, there are some more in my drawers that need sorting through and grouping.
On the Yorkshire coast these can be found in the lower lias, jamesoni zone, polymorphus subzone, and their phragmocone is usually relatively small and preserved in stable pyrite while the body chamber is flattened or not preserved at all.
I add the word “stable” here without parentheses or doubt, since this pyrite really seems to be stable, I´ve seen Polymorphites specimen in Whitby museum that probably have been found 100 years or longer ago and show no sign of the dreaded pyrite decay.
Due to more or less oxidization, and probably some intricacies in the composition of the pyrite, the ammonites show a natural light copper colour on the side embedded in the rock, while the upper side is usually poslihed to a more golden tone. On the ammonites shown I’ve only removed some small surplus of matrix with a needle, carefully brushed them under water with an old soft tooth-brush and gave them a good thorough but thin varnishing – they’ve kept their colour for many years. One where I did add the toothpaste to the toothbrush when cleaning it (it is really one of the best polishes !) of course lost its copper colour, but also stayed “silver” and decay-free after varnishing.
It´s a special delight to seem them magnified on the screen at approx. 5 x, most papers only picture them “life-size”, and this is, as you see from the pictures titles, usually only between 2 and 3 cm.
Posted by andysfossils on June 19, 2012
Over the last couple of years, a couple of friends and myself have, more or less independently, found relatively substantial blocks with nicely preserved, large Echioceras raricostatum
, always at around the same spot, in Bay. Echioceras is rather rare by itself in Bay, if found, mostly flattened, so a find of a 3D calcite-preserved Echioceras block is something quite rare. We´ve been discussing the question if the blocks are
- glacial drift, derived from the boulder clay
- or special preservation e.g. from a localized lens, from an old cliff fall in that area
Unless we find such a lens in-situ, the question will probably remain un-answered.
Whatever the source, the ammonites are rather nice, but relatively difficult to prep. The matrix is full of small and large ammonites, crinoid remains, bivalves etc and is rather sticky. Here is an example that a friend (you know who you are) presented to me as a (generous) gift.
Echioceras raricostatum, 6 cm
Echioceras raricostatum, keel detail
Interestingly, HOWARTH notes that for the holotype of SIMPSON´s Echioceras cereum (a synonym for E. raricostatum), that the exact bed ist not known – the preservation looks exactly like the ones from the block !
This is a block I´ve found myself, and begun preparation, a large E. cf. raricostatoides (about 8 cm) is visible.
Block with Echioceras cf. raricostatoides, ammonite about 8 cm
This is another one, awaiting preparation, found on my birthday this year !
Block with Echioceras sp., size about 40 x 20 cm
Not breaking these kinds of blocks on the beach is always some kind of gamble, you have to carry it a long way, but you might end up with a block with only the partial, ground down ammonites showing on the surface… we´ll see how this one turns out…
Posted by andysfossils on June 17, 2012
I see similar Ammonites like this one sometimes sold on eBay as “Dactylioceras sp.” – but it is in fact a Zugodactylites braunianus.
Zugodactylites braunianus, 7 cm
This misidentification does not happen only to sellers on eBay, in fact Zugodactylites was not known to occur in Yorkshire until the late 1960s (HOWARTH 1978) – I´m sure someone must have found it before ! HOWARTH in his “The Liassic Ammonite Zones and Subzones of the North-West European Province” in 1961 still lists it to be found in Britain exclusively in Northamptonshire.
In my collection I did actually recognize it to be something different when I saw the ammonites in the drawer side by side with other Dactylioceratids, and did see the picture in HOWARTH 1961 pl. 73.1 as the closest match I could find. HOWARTHs 1978 paper about “The stratigraphy and ammonite fauna of the Upper Lias of Northamptonshire”, which I got somewhat later, then “officially” confirmed it´s occurrence in Yorkshire.
The ammonite is much rarer than the Peronoceras it is usually associated with, using HOWARTHs numbers by a factor of more than 10. Once you´ve found one, you´ll always recognize it again : I always look for the inner whorls, if you see very sharp, pronounced ribs, with tiny spines where the whorl meets the umbilical wall, it´s most likely to be a Zugodactylites. The preservation and “behaviour” when being prepped can also give a clue : I´ve found that with Zugodactylites the “lid” on the inner whorls “pops out” very easily and usually most perfectly. Whether this has to do with the matrix it usually is preserved in or it´s shell structure I do not know…
Other characteristica include it´s flatter whorl section, the fine spines at the outer edge of the whorl and it´s pronounced constriction at the aperture.
Zugodactylites braunianus inner whorl, view 3 cm wide
Edit 17.09.2012 : Added a detail pictures of spines & constriction at aperture
Zugodactylites braunianus, detail of spines & constriction at aperture
While looking through the Zugodactylites in one of my drawers and comparing them it suddenly dawned on me that there was another species there as well : A Zugodactylites rotundiventer.
Zugodactylites rotundiventer, 9 cm
This one is rather large with 90 mm compared to the Northamptonshire ones that HOWARTH mentions – the early jurassic “Yorkshire” seas apparently fed the ammonites better ! As the name suggests, it has a more rounded venter and the whorl is definitely thicker when looking at specimen of same sizes.
Comparison of Z. braunianus (top) and Z. rotundiventer (bottom)
There´s potentially another species in that drawer : A Zugodactylites thompsoni.
Zugodactylites thompsoni, 6 cm
It is half an ammonite that I picked up at Ravenscar, nicely showing the wider than high inner whorl.
As usual: If you have a better specimen, please let me know (+ let me borrow and photograph it !)
Posted by andysfossils on June 15, 2012
A few years back, shortly before Christmas 2009, a friend of ours, who we had been collecting with a couple of times, asked for my address to send me a small parcel with ammonites. Reading back through the old e-mails I think she actually got them from someone who now has read some of my first blog entries and asked if I was planning to include liassic Scunthorpe ammonites
(that´s you, David) in the book. Small world…
I was quite excited then (who doesn´t like a surprise parcel !) and I´m still very grateful to this (incidentally very camera-shy) friend of ours, because some of the ammonites, while falling into generally the same sort of geology as the North Yorkshire ones e.g. from Robin Hoods Bay, are usually extremely rare at Robin Hoods Bay or don´t occur there at all (or have not been found there). Here they are :
A surprise parcel with Scunthorpe ammonites
They are :
- 3 in left upper corner : Phricodoceras sp.
- 2 in right lower corner : Tragophylloceras sp.
- 1 in left lower corner and 1 in upper right corner : Coeloceras sp.
The larger Coeloceras is about 3 cm in diameter. I´m not aware of any Coeloceras having been found at Robin Hoods Bay, so these would certainly fill a gap, especially since they are early Dactylioceratids. I know there are many other species that have been found in the vicinity of Scunthorpe.
Getting back to the question of whether to include Scunthorpe ammonites in the book…
Scunthorpe is not exactly Yorkshire, not even South Yorkshire, but North Lincolnshire. But I could certainly waive that rule given it´s only a few miles away 😉
My only problem is that the stratigraphy around Scunthorpe does not seem to have been described a lot (at least I do not know any descriptions…).
So I could certainly photograph and describe the ammonite species (if you meet me when I´m in the UK or let me borrow some of them), but – this is where you folks with the local knowledge about these disused quarries come in – I need you to fill in my gaps about the local geology to make sure we have the correct information to go with the ammonites.
So that´s a preliminary “Yes, they´re in”.
Posted by andysfossils on June 12, 2012
When collecting fossils, especially in a beach environment like the Yorkshire coast, where you often have to deal with a huge variety of different rocks from different layers, sometimes intermixed with all sorts of glacial drift, recognizing the fine differences of colours of the rocks is of some importance – it helps you pick out the rocks that (from experience) most likely contain fossils, even if they don´t show on the outside. For example when you´re red/green colour blind you´ll have more difficulty picking out subtle greenish shades of some lower liassic rocks.
Rock colours on the beach, a toarcian mudstone in the middle
As a collector I find colour equally important in identifying fossils and judging their provenance. Consider these two ammonites :
Two ammonites in black & white
Of course I tricked you here : I intentionally converted the photographs of the two ammonites to black and white, even then I had to modify the exposure of the second picture somewhat to make it look more than the first one.
Here is what they really look like :
Two ammonites, natural colour
What a difference ! The left ammonite looks very much like a Yorkshire one now, while the right ammonite which is preserved in a strikingly light grey marl is actually from near Cingoli, Italy (specimen swapped against some Yorkshire material with an Italian member of the UKFOSSILS forum – thanks again !).
I guess one of the main reasons why many professional palaeontologists in their publications almost exclusively use greyscale photographs is just that : It eliminates colour variations. Sometimes fossils are even coated in white ammonium chloride smoke to further eliminate potential reflections, translucency, and greatly enhace surface detail.
This way you make specimen more comparable with ones from other areas, removing the unwanted effects of colour due to different preservation.
Other reasons may include the relative simplicity of the B/W photographic process compared to colour and the past cost of colour printing.
Now are the photographs in my book going to be black and white ? No – this is not going to be a book fulfilling all scientific standards, I want to show colour differences, I want to show you what the matrix in the luridum subzone looks like compared to the maculatum subzone, the golden shine of a pyrite ammonite, the deep black of a Gagaticeras´shell, or the chocolate-brown of a Yorkshire Zugodactylites. While the effects of whitening the fossils using ammonium chloride can have a dramatic effect on visibility of detail, it adds huge complexity due to necessity of a lab. Digital photography has eliminated many difficulties in the colour process (and printing in colour is not as cost-prohibitive as it used to be), but it has brought new ones as well – more on that later…
Posted by andysfossils on June 10, 2012
I showed you a relatively large Radstockiceras buvignieri (from the collection of my friend Klaus) in an earlier post, now here´s the smaller Radstockiceras from my own collection :
Radstockiceras buvignieri, pyrite, 3 cm
This one is preserved in solid (stable) pyrite and came from the polymorphus subzone, together with a few other finely pyritized ammonites like Tragophylloceras numismale and Polymorphites sp. (more on these later…) Is this the same species as the larger version ? Preservation is certainly very different, the large Radstockiceras is preserved in grey limestone. I doubt my friend Klaus would forgive me if I broke open the large Radstockiceras he loaned me to check if the inner whorls are the same as (the outer whorls) of the smaller pyrite ammonite (if preserved at all…) – Imagine me giving him back a small bag of rubble, saying “Thankyou, here´s your ammonite back, I ckecked something on it, but it came to no result…” ! I guess there would have been a chance to do this – the large ammonite had been broken in the middle when found – but there is no photographic record of what the inner whorls looked like (I feel yet another blog article coming up – photographing your finds shortly after you´ve made them…).
I had put the pyrite ammonite towards Radstockiceras complanosum, especially since I had seen a picture of one extremely similar ammonite in HOFFMANN´s 1982 publication about the lower Pliensbachien of North-West Germany. There it was listed as Radstockiceras oppeli, a few years later SCHLEGELMILCH 1992 lists this as a later synonym of Radstockiceras complanosum :
Radstockiceras oppeli (SCHLOENBACH, 1863)
Radstockiceras complanosum (SIMPSON, 1855) -> since described earlier, this species has priority
HOWARTH 2002 goes even further and lists Radstockiceras complanosum as a synonym for Radstockiceras buvignieri :
Radstockiceras buvignieri (D´ORBIGNY, 1844) -> since described even earlier, this has priority
Since HOWARTH obviously had the opportunity to compare against SIMPSON´s holotype, this is what it is labeled now as well : Radstockiceras buvignieri
The full list of synonyms even contains different genera (Ammonites, Retenticeras, Metoxynoticeras) as well, painting a picture of more than 150 years of different authors in different locations working on potentially differently preserved ammonites, of (early) branching and (final ?) joining of species names.
Posted by andysfossils on June 9, 2012