[Old Board Archive] Vampyroteuthis Question (and ammonites)


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May 30, 2000
Quite the classic thread here from the "old" TONMO.com Message Board. Enjoy!


Vampyroteuthis Question|phil_eyden|
I was wondering how exactly Vampyroteuthis is classified. Is this creature actually a squid despite its resemblance to an octopus? Or is it neither of these but a seperate group descended from the common ancestor of the squid and octopus. If so, when did the lineage split?

Hope you don't mind all these questions. I'm sure Steve will know!


Re: Vampyroteuthis Question|pikaia|
Some scientist say that the vampyromorphs are the ancesters of all squid and octopi.
They have found fossils of a squid/octopi that very closly resemble vampyroteuthis,Loligosepiina (e.g.,mastigophora) having eight arms and two long filaments(corisponding to feeding tenicles of squid)
since the are in the middle i believe they have their own class.
like squid they have a gladius(or at least i think they do?????), but like octopi they have the eight arms.
I'm not entirely sure what era they are said to have split.

Re: Vampyroteuthis Question|steve_oshea|
Hi Phil, Serena. It's position in the overall scheme of things is rather interesting, but instead of me writing something here and now, working from memory ... which has its faults sometimes, let me check out a recent article on it and the systematic position of Mastigophora (actually sitting on the desk at work). Sounds like you have this paper too Serena.

I've long-wanted some of these more bizarre cephalopods to be extant representatives of ammonites (minus the shell) .... but all of the work being done on them, morphological and genetic, is pointing to their having common, quite recent ancestry.

It would be fantastic is something other than 16S and CO1 sequences showed a completely different relationship between cephalopod taxa. I do believe we should embark on a 'Map-the-squid Genome project', but itsy bitsy might have to do for the meantime.

Re: Vampyroteuthis Question|phil_eyden|
Thanks for the info Steve and Serena. Just one question, and pardon my ignorance, but what exactly are 16S and CO1 sequences. I wonder if anyone has attempted a cladistic analysis of cephalopod features?



Re: Vampyroteuthis Question|steve_oshea|
Sorry, the 16S and CO1 are just two regions of DNA (of the squillions) that can be readily sequenced. That's a rather simplistic statement to make, but I think it will do for this.

Re the cladistic analysis query, yes, there have been quite a few studies undertaken now. But I'm not a big fan of cladistics ... and that's really putting my neck on the chopping block. To me it's just another tool, but not the final say on any matter by any stretch of the imagination. It is supposed to stabilise nomenclature and give us a better understanding of systematic relationships amongst taxa ... but I've seen a lot of destability, and different people proposing different classifications based on the same, similar or quite modified cladistic techniques. Who do we believe? The latest revision/review? No. You'll just have to make the value judgement yourself and believe what you feel is right.

Re: Vampyroteuthis Question|fujisawas_sake|
Sweet~! So they ARE conducting genetic phylogeny on Cephs?! That's great!

My question about the cephalopod evolution is "what exactly did happen to the ammonites?". Yeah, I know, "they're extinct", but why so? I mean, they had a bauplan that let them be very successful for hundreds of millions of years. Shouldn't they still be around, in some form? If Limulus (the horseshoe crab) can make it, then what about the Ammonites?

Yeah, I'm sure the oceans were different in their time - its probably some ecological factor. Are there any theories?

Is there a good place where I can see the latest papers on Cephs?

Have a great day!

Re: Vampyroteuthis Question|pikaia|
you know there are chambered nautiluses that are very distant relatives of the ammonites
When you see an artists rendition of a living ammonite they always apear to look like nautiluses even though they have no idea what they really looked liked.

And they are always finding new things in the briny deep so what if one day they found a living population of ammonites.Kinda like when they found those ceolacanths(i doubt it but who knows):smile:

Re: Vampyroteuthis Question|steve_oshea|
Hi Serena. Regarding an earlier posting of yours where you refer to Mastigophora,I believe what I have here, and am about to paste below (abstract anyway) is a more recent look at these fossils.

The guts of it is that Mastigophora is likely a squid, and not a vampyromorph/octopod.

The paper is titled:
Re-evaluation of coleoid cephalopod relationships based on modified arms in the Jurassic coleoid Mastigophora.
Vecchione, M.; Young, R.E.; Donovan, D.T.; Rodhouse, P.G. 1999.
Lethaia, 32: 113-118.

...and the abstract:
Mastigophora brevipinnis Owen, 1856, is a 'fossil teuthid' presently considered to be a member of the coleoid cephalopod Suborder Loligosepiina Jeletzky, which in turn has been placed by various authors in or near the Vampyromorpha Grimpe. Recent morphological and biochemical analyses indicate that vampyromorphs are more closely related to the Octopoda than to the Decapodaformes. Fossils of Mastigophora from the Oxford Clay (Jurassic: Callovian) show soft-tissue preservation and evidence of arm-crown specialisation. Some of these fossils have up to eight short, thick arms with circular-like sucker structures and filiform distal extensions, plus what appear to be the bases of two thinner ventrolateral arms. The latter lack proximal suckers and curve medially to insert into the arm crown, similar to the tentacles that are the modified ventro-lateral arms of living squids and cuttlefishes. This suggests that the thinner structures were decapod-like tentacles. If Mastigophora had tentacles homologous with those of modern decapods, then it was a decapod, because this synapomorphy defines the Decapodiformes. This indication of decapod affinities for Mastigophora brings into question the relationships of the other 'fossil teuthids'. The inferred relationship of the Loligosepiina, including Mastigophora, with the Vampyromorpha, based largely on similarities of gladius morphology with that of living Vampyroteuthis, may reflect shared plesiomorphic characters.

Nobody ask me to translate the big words ok;D! Cheers, O

The interesting thing here is that the 'new mystery squid' had 10 similar arms, with none noticeably differentiated to form tentacles. Now I wonder whether this mystery squid is a 'living fossil', the likes of Mastigophora, as opposed to it being a large Magnapinna. Who knows ... guess we'll have to wait for that animal to be caught.

I can see you're all going to keep me busy checking out the literature! Interesting this. And yes, wouldn't it be superb to find a live ammonite; this is one of those dreams in the back of my head every time a deep-sea dredge full of goodies tips on the deck. I'm not convinced that the shell was external at all. Those aptychii have me quite confused - they're more akin to gizzard plates than beaks.

Re: Vampyroteuthis Question|phil_eyden|
Following on from the above question as to why the ammonites became extinct as oppposed to the nautilus, one theory holds that whereas the nautilus produces offspring 25mm long, the ammonite's were planktonic in size. The nautilus leads a scavanging lifestyle largely feeding on detritus raining down from above into deep water onto the continental shelves it inhabits, thus a food supply is always plentiful. The ammonite's offspring, being part of the planktonic chain would be extremely vunerable to slight changes in the climate. If the sky was obscured for months or years following the impact of a meteorite 65 million years ago, this would have caused a devastating effect on the phytoplankton which requires energy from the sun to survive. Obviously this would have a knock on effect on the zooplankton slightly further up the food chain. Thus, the poor animal was doomed.

It's an interesting theory though it does not explain why the ammonites were declining in family and species numbers towards the end of the Cretaceous even before the asteroid hit (if that's what happened). A similar scenario happened to the trilobites before they disappeared at the end of the Permian. Perhaps they'd just had enough!

It's a pity that no soft bodied ammonite parts have yet been found so noone knows if they had dozens of arms as per the nautilus or eight or ten as per the squid or octopus. However, occasional soft bodied belemnites have been found which seem to have eight (if I remember correctly) covered in hooks.

Hope that theory makes sense. I'm afraid I can't remember where I read it, but it seems to be logical enough!

Re: Vampyroteuthis Question|steve_oshea|
Phil, if you ever track that theory to its source I'd sure appreciate a posting here (author, book/journal title, date and pagination). It sure sounds plausible.

Does Nautilus really eat 'raining detritus'?
Cheers, O

Re: Vampyroteuthis Question|phil_eyden|
Hi Steve.

Sorry about the 'raining detritus'. I wrote this after being up for 22hours after a night shift and I think I was going a bit mad. I know the nautilus is an active hunter and a scavenger; I think I meant it was an opportunist feeding on whatever it comes across but I wasn't thinking coherantly. Please correct me if I am wrong!

As for the theory that ammonite had planktonic offspring, try C.H. Holland (1987) 'The nautiloid cephalopods: a strange success' published by the Journal of the Geological Society of London 144, 1-15. I have not read this as I'm sure it would be well above my head, but it was referenced as a theory in E.N.K Clarksons's 4th edition of 'Invertebrate Palaeontology and Evolution'.(1979, 4th ed.1998), which I am using as a source.

I hope that is of some help.

All the best,


Re: Vampyroteuthis Question|pikaia|
Thats the first time I've ever heard any one suggest that the ammonite shells may not be external(you just always think outside the box Steve:smile:)

I never even thought of that

I was wondering how would one find these publiished papers ( i know that there are some Ceph base) I always try looking and never find much. Although I might be giving up to easy.

And i have good news... Well i dont know if i told any of you this before but in my "free time" I have been working on a Time Machine.
It should be done soon - all I really have to do is calibrate my googleatore and get that darn time gauge fixed.

When Its ready I plan on doing a nice time lapse thingy on the history of life. I 'll send you a copy when i can:smile::smile:

Also on a side note i would like to thank you guys for really making me relize(yet again) how much i will have to learn.

Being more articulate would be enouph for me now69)
but as Colin once said "you learn as you go" I just want to learn it all now;D

Re: Vampyroteuthis Question|steve_oshea|
Re keeping up with the literature ... well, when you find a way to do this please let me know!!! It is hard, but generally speaking I send my reprints to others and they in turn send me theirs. It's one of those nice little reciprocated arrangements. Of course it doesn't always work, and so often you'll pick up a journal and find something you never knew existed. It's never ending actually.

For the meantime if there's anything you want to know just fire away a post here and if I cannot help then surely someone else will come to the rescue.

Re: Vampyroteuthis Question|pikaia|
Hey again

Well I was doing some searching and came upon this interesting page, that shows the phylogenetic tree of cephs

phylogentic tree of cephs

I found this quite interesting, albiet a little confusing

I also found some neat vampyromorph hachling pics and info

vampyromorph hachling pics

talk to ya latter:smile:

Re: Vampyroteuthis Question|phil_eyden|
Regarding the reasons why ammonites became extinct and the nautilus did not, I've just come across an interesting theory on BBC site. In case he finds this, the chaps name is Joe Botting who posted the theory. Here's a quote....

...and it's worth remembering that the ridiculous volumes of acid rain resulting from shock atmospheric heating, and vapourisation of calcium sulphate at the impact site would have dramatically affected surface waters (acidification of the upper 100 m of the water column, according to some calculations). The pH would be neutralised at depth by reaction with the slightly alkaline seawater. Since ammonoids and nautiloids had/have aragonitic shells, this would generally have been a Bad Thing for surface organisms. It's worth noting that belemnites also went extinct, but squid and octopus survived.

....sounds plausible! Any thoughts, anyone?


Re: Vampyroteuthis Question|tani|
Hey Steverino, how're your artistic skills? Because I'd be interested to see how you envision an ammonite with an internal shell. Would the body be just a circular mass covered with skin, or would the skin be differentiated into a spiral to conform to the shape of the shell? (I don't know if I phrased that clearly, but hopefully you can visualize what I mean.) Either way, that would be one weird-looking ceph.

"Thinking outside the box," for certain! That's why our Doc O' remains the Best of the Best.

Re: Vampyroteuthis Question|phil_eyden|
Hi Tani,

I would assume that Steve's theory is that the shell would be internal as in Spirula.

I would have a couple of concerns about this:

1) A number of the ammonites I have found have been coated in mother-of-pearl. Are there any examples of the internal secretion of this substance in the mollusca? I have always assumed, probably incorrectly, that this was a protective external coating.

2) Some of the Jurassic and Cretaceous Ammonites exhibit spines though these are almost invariably snapped off during the process of fossilisation. The spines often leave raised bumps along the shell in one or two rows known as tubercles. If the shell was indeed internal, the spines would have had to protrude through the enveloping mantle to be effective. I don't think that this is a feature known from any other mollusc that I can think of, but please correct me if I anm wrong.

3) A have a lovely photo of the Lower Jurassic ammonite 'Liparoceras naptonensis' that actually still displays pigmentation. It has a number of very thin brown/black lines that run parallel to, and either side of, the keel of the ammonite. There would be little use of such pigmentation if the shell was internal as presumably coloration would be used to break up the outline of the creature to predators.

If I can find a photo of this ammonite anywhere I'll try and post a link.

These are just ideas. Please feel free to correct me as I'm not 100% sure I know what I'm talking about!


Re: Vampyroteuthis Question|steve_oshea|
That pigment reference is rather interesting Phil!! Brown/black .... what about a sepia stain (from something like an ink sac/paired ink sacs even (for bilateral symmetry). I'm just playing devils advocate here ... but real/true pigmentation???? After all those millions of years? Sensational!

Tani, I'd liek nothing more than to sit down and reconstruct the ammonite animal .... but I'm like way behind on simple things like those illustrations of octopus and squid for the site (despite my best of intentions I just don't have a lot of time at present).

Phil, really coloured????? Like I'm sitting here wondering if any other fossils have retained colour after all those years (other than amber-bound insects etc.) ... and have any of them got any colour?? Not sure.

Spines/internalised. Hmmmmm. Good point. You're 100% certain they are spines? Do they articulate or are they fully attached to the knobs? Hmmmmmm.

Yes, I'd make the animal a bit like Spirula, were I to reconstruct it, except I've a feeling the body might be relatively more massive.

Interesting; I must go pour a glass of wine and ponder this 'mother of pearl' business too.

Re: Vampyroteuthis Question|amniote|
Mother of pearl is generally secreted from the foot/mantle. Oysters only secrete it on the inner walls of their shells, and also around any bits of grit etc. which lodge uncomfortably close to their body tissues (hence pearls). Molluscs such as cowries, which have a smooth outer shell, need to extend the mantle right around the outside of the shell in order to deposit the substance.

If a nacreous ammonite shell was external, it would presumably have required the same sort of procedure, i.e. the ammonite would extend the mantle (modified tentacles?) right around the shell to deposit the mother-of pearl.

Re: Vampyroteuthis Question|steve_oshea|
....and the ammonite becomes more like a floating slug, maybe something akin to a pteropod, every day (partly in jest).

I suppose the mantle need only extend over the amonite shell - the shell need not be fully internalised. Irrespective, the live ammonite must differ remarkably from any extant nautiloid.

Anyone have any aptychii, or know of any image of these 'beak' structures in situ within the last chamber of the ammonite shell - or removed for that matter - that could be linked to this site? And of the remarkable calcified beaks of Nautilus (relative to the last chamber of the Nautilus shell would be superb).

Check out also in your text books for structures referred to as gizzard plates in the likes of Opisthobranchs (eg. Philine). You might also happen upon some references to these remarkable 'radula' structures from the ammonites (outrageously massive teeth). Now imagine the basal subradular ribbon and musculature required to operate a set of teeth like that. THEN, considering the food must be quite coarsely masticated, and given the oesophagus of the animal passes straight through the cephalopods brain, imagine the diameter of the brain/head in order to accommodate the entire structure. NONE of this, including the buccal-bulb musculature required to operate those 'aptychii' (if they are beaks) is going to fit inside that last chamber - not in my lifetime anyway - unless you got a sledge hammer and pummeled it all in!!!

....now, if those aptychii were actually gizzard plates, and SOME of the structures described as 'radula' teeth (these seriously ungainly huge things) were actually gizzard teeth, then the 'gizzard would fit nicely inside the last chamber of the ammonite shell (and you shouldn't be surprised to learn this is approximately the position of the stomach in Nautilus... I recall looking into this several years ago - I hope my memory is not putting me and everyone else wrong).

I must add that some teeth reported as radular teeth are truly radular structures. But not all (some are also likely to be palatine palp teeth). In the fossilised condition (loss of soft parts) these palatine teeth, placed on palps lateral to the odontophore/radula mass (true buccal mass), assume a position homologous to the marginal teeth of extant cephalopods (hence some extinct cephalopods seem to have many more rows of teeth on their radula than has been described for extant ones). Surprisingly nobody has done a survey of palatine teeth morphology in extant cephalopods ... they are very poorly known .. but in some species they are of equivalent size and shape to those of the true radula. Anyone want an interesting research topic?

...did I lose anybody?

...then you've got those rather bizarre uncoiling asymmetrical ammonites. What to make of those in a symmetrical swimming world?

What say people?

Re: Vampyroteuthis Question|steve_oshea|
My, things really have gone quiet on this thread!! Frighten you all away?

Actually, Phil shot me through some most stunning photographs of aptychii in situ, from a new book released in 2002 by Neale Monk, titled, I believe, 'Ammonites'. Now, I'm an extant cephalopod person (meaning Recent (capitalised, as in time period, or now)), but I have to say that what Phil sent me has me absolutely hooked on fossil cephalopods!!!. I'll be buying a copy of this book, and I'd suggest anyone else wanting to broaden their horizons should look at a copy also. Well done Neale! (and thanks buckets Phil).

Well, if only Neale would post ..... but let's see. I'd swear, on the basis of those stunning shots, that these 'aptychii' are not beaks, rather that they are gizzard plates; what a discussion we could have here!!. Moreover, if an animal is going to be eating 'tough stuff' requiring such serious grinding surfaces in its gut, then it has to have a few arms only (not a multitude like Nautilus) - interesting reference to 'raining detritus' earlier on Phil; I must admit I haven't followed up on this ... though have meant to. Phil also sent me a rather sensational plastic ammonite (reconstructed)....and some superb fossils, for which I am in his debt.

I'd just like to say thanks for the posts in this thread, everyone. A fossil freak has been born as a consequence.

Re: Vampyroteuthis Question|phil_eyden|
I can recommend Neale Monks’ book ‘Ammonites’ (Natural History Museum 2002) if anyone is interested in fossil cephs. It has some superb photos of these beautiful creatures (how many variations on a spiral can there be?) and the discussion is basically about the biology and lifestyle of these ancient beasts. The book is aimed at the interested layman level and is not too technical as to be inaccessible, in other words, just right! If you have ever found one and want to know more about it, then this is the book for you.

The aptychus is a strange structure that looks like a bivalve found, rarely, wedged in the last chamber of the ammonites shell and is in two distinct halves. Looking at the photo of the atychus in situ in a specimen of Neochetoceras, I can see what you are saying Steve, it really is too massive to be a set of jaws. I thought it was far too receded in from the shell aperture. From the source material I have here, a grand total of two books, no-one has ever suggested that the aptychus structure may have been gizzard plates. So I think Steve has made a brilliant suggestion!

The interpretation of the function of the aptychus seems to fall into two camps; either it was a massive set of jaws (Steve’s done away with that one, methinks) or it was an ‘operculum’ or lid with which the ammonite could close off the shell to protect itself. However in some species the aptychus does not fit with the opening to the chamber though I suppose this would not necessarily be a problem if fleshy muscle closed the gap. Lehmann and Kulicki’s 1990 paper suggested that the structure was of dual pupose, that the aptychus was a huge lower jaw that could also function as a lid. Weird!

Steve, please ignore my statement about ‘raining detritus’; that’s what happens if you rely on a jaded memory without looking things up before you post! And I’d been up 23 hours. Any old excuse……..

Re: Vampyroteuthis Question|steve_oshea|
H all; this is an excerpt from a message from Neale Monk regarding the ammonite book, and the aptychi

Anyway, on the topic of aptychi, the examples we showed do look rather big to be jaws. Personally, I don't think they are jaws, but many people do. I think the problem comes down to some aptychi not
fitting the aperture neatly as opercula would, so an alternative function was sought.

It should be noted that the aptychi are not supposed to be the 'points' to the jaws, i.e. the beaks, per se but rather the plates behind them to which the muscles were attached. Even so, the jaws would be MASSIVE compared to the body of the ammonite.

Gizzard plates is an interesting idea, and one I haven't heard talked about before. The problem is that there doesn't appear to be wear on any of the surfaces as you would expect if they were rubbing against each other or hard foodstuffs (though I suppose they could have been covered in some organic material in life). Also, some aptychi are
spiny and rather delicate looking - frustratingly for the operculum theory the spines point outwards! Finally, in earlier ammonites there is only a single aptychus (called the "anaptychus"), rather like a
half-moon shaped lid or trapdoor. This couldn't grind against anything.

The fundamental problem is that no one explanation fits for all aptychi or anaptychi; indeed, it seems more probable that like jaw bones in vertebrates they were used for different things. For example: in primitive reptiles, the jaw bones connected the mandibles, while in mammals those same bones are in the ear transmitting sound from the outer to inner ear!

Furthermore, we simply don't have enough data on ammonite soft body parts. At a guess, we can say they were more like squids than nautiluses, but really it is a 50:50 bet which is correct. The fossils just aren't there. In itself this is interesting, because we have many soft body squids from ammonite rich formations. There was something about ammonites that precluded soft body preservation.

One last thing. I can't give you permission to reproduce images from the book on the web site since I don't own the copyright to them. The Nat. Hist. Museum does. However, I doubt they would be too bothered about small, low res scans being used for academic purposes. But that's not permission, just an opinion!

Best wishes,

Now, we haven't quite got permission to 'reproduce' those images Phil, but I suppose the next step is to contact the BM and see what I can do. It would be sensational to get them online.
Ammonite Spines

Somewhere in this old thread there was some talk about spines on ammonites. The following picture shows a few crushed spines. Most of the fossils I find around here are internal molds and the shell has long since disolved away, but these are preserved in shale (crushed by the weight of sediments). The spines seem to be hollow and as the ammonite finished making the spine, it sealed it off on the inside. There is clearly a different kind of material used on the outside of the shell than the nacreous material on the inside (maybe just an artifact of preservation).
A couple of questions Kevin. Are we looking at the casts of spines, and if so, is it usual for a cast to be hollow? If not casts, can you see any muscle attachment surfaces on those spines? (I know, I know, the shell is supposed to be external, I'm just playing devils advocate; I would not expect to see any scar on the spine if what you have photographed is a cast). It looks like there's some sort of concentric layering there ... that's interesting for an 'external' shell, unless the animal had a rather substantial mantle of some description (or the concentric layers are also an artefact ... if this is a cast). Questions, questions, questions...

Nice pics! Thanks, O
Hi Steve and Kevin. Just a thought but if the shell of the ammonite was indeed internal then what would be the advantage of the lateral extensions of the shell known as lappets? These are two flanges that protrude either side of the aperture of the ammonite but are only only usually displayed on the microconch (the smaller of the two forms in a sexually dimorphic species and probably the male).

If the shell was internal then such a structure would be a waste of resources for the creature to produce as such a structure would serve no obvious function.

As far as I am aware the lappets are not visible in all ammonite species but surely this would present a problem for those species that do have them. (I'm guessing in the dark here!).
Someone's got a flash new avatar!!!!

Phil said:
If the shell was internal then such a structure would be a waste of resources for the creature to produce as such a structure would serve no obvious function.

You know I know nothing about ammonites Phil :wink: I'm an octopus man (not even squid). What function to they presently attribute to the lappets, and do you know of a web link to/pic of these structures? I just did an ammonite search and was pretty blown away by some of the online info ... but unfortunately none that I looked at had a ref to lappets. I'll keep on looking in the interim.
Well, Steve, this may be an example of where the book is better than the web! There are several references to lappets (and photos) in Neale Monks book Ammonites.

Wifey was s'posed to get me that book for christmas, but she went on holiday instead ... and forgot both me and the book :frown: I shall do so via CSIRO publishing Monday (and charge it to her credit card :biggrin2: )
Ta, O
Here’s a link to the best picture of an ammonite bearing lappets that I have found, absolutely enormous in this case:frown:Kosmoceras):

Sorry, that's a dead link (404)

In others, such as Grossouvria, the lappets seem to be strange leaf shaped protrusions from the aperture, but I’m afraid I couldn’t find a picture of that one. Neale Monks is of the opinion that these structures were used for display purposes on the microconch (male) and as they are not found on the macroconch (female) then it is difficult to think of an alternative explanation. He suggests that they may have been an indication of virility and sexual maturity, much like a peacocks tail. It used to be thought that lappets were some form of clasper used during mating but that idea has apparently gone out of fashion.

I’ve just ordered an ammonite from a fossil shop that has clearly defined lappets so when it arrives I’ll post a photo of it here if you like.

Glad you like my new avatar! Got a bit fed up with the old one.

This is the actual shell material (or a replacement). The bottom photo is a section of the whorl crushed flat, what I refer to as the bottom is the part of the shell that was resting on the sea floor, the top side was crushed down and the whorl flattened. There may be some remineralization taking place. Only the outside of the shell is visible except where parts have been broken away, so I dont have a good look at the inside for muscle scars, the inside is pressed against itself.

By the way, another good book on ammonites is "Ammonoid Paleobiology" a little more technical and a lot more pricey, but worth it. A few papers of interest in it are "Morphology of the Jaws and Radula in Ammonoids" "Attachment of the Body to the Shell in Ammonoids" "Ammonoid Shell Microstructure" and "Color Patterns in Ammonoids" all by leading ammonoid workers.
OMG Phil, those lappets are ginormous (they remind me of handles on a chariot, with the ammonite wrapping arms around them and carting his shell about)! If they were used in some form of sexual display/symbol of 'masculinity'/fertility, then there must have been a bit of social structure in the ammonite community - and females must have been doing a spot of mate selection, and accordingly had pretty good brains to differentiate lesser from 'greater' males ..... and I'm not sure whether this sort of 'mate selection/discrimination' occurs today in Recent cephs (Colin, what happens in Sepia - do you get dominant males or fussy females? :wink: ). I can't help but think that those structures would 'get in the way' of any up-close-and-personal business. But why otherwise in one morph/sex only?

Kevin, thanks for the book ref ... will go order another for my library.

I'm off to think
This is something I have just made up so please utterly dismiss this if you think that is appropriate!

If the lappets were indeed used for display purposes in order to attract a mate, then it naturally follows that the ammonite must have had well developed eyes in order to recognise visual signals and, as Steve suggests, a well developed brain able to interpret these signals. Species with lappets must have been fairly shallow water creatures as a physical display structure would be pointless in the abyss with little light to penetrate in order for the structure to be seen. Can we therefore assume that the fleshy head of the ammonite must have had a much closer affinity to the coleoids in structure? Eyes such as possessed by the nautilus would, I assume, be unable to determine fine detail due to their basic structure yet the much more advanced squid or octopus type eyes would be able to do so.

The soft body part of the belemnite certainly bears a close resemblance to the squid. It would be interesting to know how closely the two groups are related to see if any parallels could be drawn in their respective soft-bodied anatomies.

I know my little theory of the ammonite possessing a coleoid head as opposed to a nautiloid rests on a number of assumptions, what does anyone else think?

Kevin - I did some hunting around for the book you mentioned. The cheapest I could find was over $200! Ouch. A bit out of my price range, unfortunately.

Confused, as ever,

Totally logical stuff Phil!

I've probably asked this before, but are there any traces of muscle-attachment scars inside the aperture of ammonite shell (to have held the animal in)?
Steve, apparantly muscle scars are occasionally found and present the only direct evidence we have as to the soft bodied creature itself. These scars are normally located at the rear of the final septum. There is a brief reference to them here: (go to the end of the article). Muscles are allegedly attached in long and thin strips though I've yet to find a photo of this:

Sorry, that's a dead link (404)

Alternatively, an obscure paper was written on scar attachments in 1898 by a Victorian gentlemen known as Crick:

Crick G. C. 1898. On the muscular attachment of the animal to its shell in some Fossil Cephalopoda (Ammonoidea). Transactions of the Linnaean Society of London (Zoology), 7: 71-113

As this paper was quoted in the above recent article it must still be of great value beside being over a century old.

I hope that this is a useful pointer. I'm sure Kevin can provide some interesting info!

Phil said:
These scars are normally located at the rear of the final septum. Muscles are allegedly attached in long and thin strips though I've yet to find a photo of this:

Real interesting Phil. Having found these muscle scars I'm sure there's another set to be located. The scars at the rear of the final septum, if the animal was encased within the shell, would have to be the points of attachment of some retractor muscle system (to pull the rear on the animal, or part of its anatomy, likely the gizzard, inside the last chamber). To counter this, if the animal was truly encased within that last chamber, there must also be an opposing set of muscles, protractors, with points of attachment (and associated muscle scars) probably located towards the edge of the last chamber (to pull the animal back out again). Are you familiar with any reference to these/any such scars?

Sorry to keep asking these questions ... real nice link you gave by the way!
attachment scars

The photos below show possible muscle scars. The small arrows point to the approximate location of the last septum, or at least the point where the mature modifications of the shell begin. So this would be the back of the final living chamber. I am not sure these are muscle scars but there is some kind of structure there made before the animal had finished the shell, as if it knew where it was going to finally attach it's muscles. These are internal molds without any shell material left.

An interesting note about Phils avatar. Until recently parts of anomalocaris were parts of 3 different animals, the body was one animal, the mouth another and the appendages another. until the complete animal fossil was found. Someday someone will find the fossil or fossils of an ammonoid that will clarify all.

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