A Nice Gault Clay Ammonite


TONMO Supporter
Nov 19, 2002
This is going to be a cracker of an ammonite (Hoplites/Euhoplites?) when it gets cleaned up. A friend discovered it this afternoon at Folkestone; at present I am not sure how complete or stable it is as it was removed with a large piece of surrounding matrix. Will post photos of the cleaned ammonite as I receive them (thanks in advance Robert!).

Also, here is a nice Hoplites dentatus from the Gault. Apologies I did not take the name of the chap who found it, (please drop me a line if you read this and I'll credit you).


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ooooooooooooooooo beautiful!

Say Phil when you find these are they in association with other groups???? Just curious cos when we get fossil bryozoans often we seen brachipod and crinoids. Also in a valley north of here there is a jumble of extinct Dolphin ( Waipatia sp) bones found with whale bones and bizarre sponges.

Yes, that is the original shell material, Kevin. It's amazing that most of these fossils are preserved in their original shape, not crushed.

Jean said:
Say Phil when you find these are they in association with other groups????

Oh most certainly Jean! The site really is nicely representative of a 100 million year old shallow-sea tropical marine community.

Most of the fossils from the clay are of the small invertebrate variety. It may seem from these pages that all we find are ammonites but this really isn't the case, it's just this being a cephalopod website I've only really ever posted pictures of ammonites as I didn't think the other stuff would be of much interest.

In fact, the most common fossils are bivalves, especially 'nut' shells and 'Devils' Toenails', whch are usually concreted and in preserved in nodules, but sometimes are very well preserved. One can also find crinoid stems, sharks teeth, gastropods in a number of varieties. Belemnites literally litter the site, though to be honest they are not that impressive, being the smallest known species.

Myself and Roy of Discovering Fossils took fifty or so people around there yesterday and we had some nice bits and pieces. One lucky chap with eagle eyes found part of a fish jaw with a tooth in situ, and we had a few finds of marine reptile bone fragments and turtle shell fragments. At least two broken nautilus pieces were found (unusual) and some pieces of concreted crustaceans.

The large ammonite found above was found by Robert Randell of the excellent British Chalk Fossils site.

Here's a couple more ammonites for you, though they were not found yesterday but were collected on a couple of previous trips earlier in the year. Ammonites didn't come much more ornamented than some of these.....


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Hi Phil,

I was on the Folkestone trip yesterday with my son and a mate. A great, if slippery, time was had by all. The rain held off just long enough.

Robs find pictured above looks amazing. I hope it stays intact.

Here's a pic of some of some samples we collected:


I think I may have caught the bug...

Hi Rob,

Nice to hear from you, and welcome to TONMO.

I’m very pleased that you had a good time and had some nice finds; this was the first such trip we had organised and I think it went well. I can only apologise that there was a slight confusion about the meeting spot, though. As you say, I think we were very lucky with the weather; if the heavens had not opened about three-ish I think we may have stretched out the day by another hour or so; but that’s the vagaries of British weather for you! I was completely caked in clay by the end of the day, I’m sure you most have been too!

Nice finds. I think what you have there (clockwise from the large lumpy ammonite) are:

1) Euhoplites armatus, a particularly spiky and robust ammonite
2) Possibly Hoplites, but hard to tell.
3) A subspecies of Euhoplites or Dimorphoplites, but again its hard to tell exactly which.
4) Heteromorph ammonite Hamites, which grew in a paperclip shape
5) Hard to say, but I suspect it might be Hysteroceras orbignyi.

In the middle:

Left) Hmm…foxed, I’m afraid. I’m not sure if its smoothness is because the specimen is worn down or not. I suspect that it could be a gastropod of some type, but really need another picture to tell.
Right) I almost certain that is Hysteroceras orbignyi again; heavily pyritised.

I’m basing these by comparisons with images on www.gaultammonite.co.uk ; you might like to have a look yourself for a second opinion. Anyway, nice to hear from you and perhaps we’ll do it again one of these days. Drop me a line sometime if you fancy it!

4) Heteromorph ammonite Hamites, which grew in a paperclip shape

Don't know much about the curly ammonites, but for the straight fragment, I can tell you for certain it isn't Hamites. It appears to have tubercles, and basically none of the Hamitidae have tubercles (one species, Metahamites might do, but that depends if you include in the Hamitidae).

There are three general of heteromorph that you find in the Gault Clay that have tubercles and paperclip shape: Protanisoceras (essentially only at the base, Beds 1 and 2 I think, but maybe a tiny bit higher), and then two that are found much higher up (bed 10 upwards), Anisoceras and Idiohamites.

All three are members of the Anisoceratidae. Protanisoceras is basically a Upper Aprian, Lower Albian genus, whereas Idiohamites and Anisoceras are Upper Albian, Lower Cenomanian genera. None of them occur commonly (if at all) in the middle part of the Albian in the UK, though presumably there are species that swam about in Middle Albian times since Protanisoceras is ancestral to Anisoceras and Idiohamites.

The best way to tell them apart quickly is size. Protanisoceras tend to be small, the longest dimension of the paperclip being something of the order of 10 to 20 cm. Idiohamites tend to be about twice that size, and Anisoceras even larger (some specimens exceeding 60 cm in length). Translating that into thickness, Protanisoceras is about the girth of your little finger, Idiohamites something between your forefinger and your thumb, and Anisoceras anything up to the thickness (and oval shape) of a hockey stick.

Spines and ribs are useful too. In almost all cases the spines themselves have snapped off or been eroded so what you have are the spine bases, known as tubercles, looking like round knobs. Anyway, Protanisoceras spines are on the edges of the ribs, sometimes one pair, sometimes two. The ribs may be flattened a bit between the spines as well, giving this ammonite a distinctive polygonal whorl section. Anisoceras have one or more commonly two pairs of spines, but instead of simple or flattened ribs the rib loop into ovals between the two ventral spines (the ones on the "back" of the fossil rather than the sides). This is called the "loop and button" morphology, and once you see it, you'll see the resemblance. Finally, Idiohamites only ever have a single pair of spines and the ribs are not flattened or looped (though two or three ribs may "bunch" at a spine base, they don't form loops or ovals). In all cases the spines may weaken on the later part of the shell. In Anisoceras and Idiohamites especially, the rib bearing the spines become extra thick compared to the 2-4 ribs in between them that lack spines. You do see this in Protanisoceras as well, just not so profoundly.

Looking at the picture, I think what you have is a species of Idiohamites. There are three species from the Gault that are most commonly seen, of which Idiohamites spiniger is the most common. It has 2-3 plain ribs between the thick ones bearing the spines. Idiohamites subspiniger is a doubtfully distinct species with coarser ornamentation. The species that is definitely different is Idiohamites ellipticoides that has very weak plain ribs between the spiny ones, and, as the name suggests, a strongly elliptical whorl section.


Thanks for the info chaps.

Phil said:
Left) Hmm…foxed, I’m afraid. I’m not sure if its smoothness is because the specimen is worn down or not. I suspect that it could be a gastropod of some time, but really need another picture to tell.

Interestingly, and hard to see in the pic, the smoothie has on off-centre curl, unlike the ammonites which have a 'flat' spiral (if you see what i mean). I'll take another couple of pics and post 'em.

For the time being, a bit OT, here's a photo I took in the carpark just after you went to collect the mis-placed attendees from the tower :smile:

Thank you Neale for another fascinating post. I'll have to reexamine my heteromorph fragments and see if I have any items of interest to post here.

Thanks pocketmoon!

Here's a picture or two of the beach. Can you see yourself? Was the factsheet useful?


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I have a question about the Hoplitidae, or at least the Hoplitinae.

Is there any sign of sexual dimorphism or polymorphism? I have not had a real good look, but they all seem to have the same basic sculpture, just different amounts of sculpture strength and conch compression. Are the different shapes found at different horizons, or beds, is the difference biostratigraphical? Has this something to do with Lumpers and Splitters?

An example, and I am not saying it is right, is the Early Triassic ammonoid Anasibirites. It was divided into two or three different genera with about 35 different species based on different amounts of sculpture strength and conch compression. Then they were all put in synonomy with one nominal specie. These were not all from a single bed, but they were from a single horizon.

Just wondering if the same thing could or should or should not be done with the Hoplitids :?:

I'm really sorry but I do not have any literature specific enough to answer those questions, unfortunately. You might find this short extract of some interest as an overview of Gault Ammonoidea:

Introduction to the Gault Ammonoidea.

One I can answer is, yes, the Gault is divided into sub-zones based on specific ammonite species. The zonation system, mostly via Hoplitid ammonites, is viewable at the links at the bottom of the page:

Gault Stratigraphy.
Re: the large ammonite in the clay bed that started this thread, Robert has now cleaned up the specimen and identified it as Hoplites spathi. This places it in the lowest bed, i.e Bed I of the Middle Albian Gault which is dominated by Hoplites dentatus, such as the example pictured at the top of this thread.

Here are a couple more pictures of the ammonite in situ and cleaned up shots including a close up where one can see crystals on the surface of the ammonite (thanks, Robert):


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Thanks Phil, that answered alot. It shows how collecting fossils from deposits of differing sedimentation rates can skew your perception of things. In your outcrop you have several biozones in a 100 meter thick outcrop, some places over here I have collected fossils from one sub-zone in about the same thickness.

That is a very nice fossil, Robert should be very happy with it. What kind of crystals are they, and will they be left on the fossil or cleaned off?

and :welcome: to Pocketmoon

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