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Bugg
wow, seems to have started an interesting discussion 

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Olenus
Hello Ryan and Adrian, the ammonite in question Arnioceras semicostatum oneside shows the typical Arnioceras  the other side is different. This we can agree on. If it could be a so called Hybrid ? Why should only one side be different? The liger is not one half lion and the other side half Tiger. its a mixture of both features. Same with the polar bear and grizzly bear. You dont get one side white and the other side brown. That would be like Freddy Star taking off two people at once and turning side veiw on.  So if the Ammonite was a hybrid it should show the mixture of features on both sides, not just one side. It just not believable. I would rather believe it was gods will. I know you both think its more like to be down to mutation. I do have a open mind but silly theories like that. What next.. it was inpregnated by an alien
The Ace of Spades,,,







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Ivano Ferri
Hello everybody!
been away a couple of days and missed the whole discussion! In a couple of days i'll be able to take decent pics of my sample and put them here to show! The ammonite i have is a "russian  aptian pinky", maybe quenstedtoceras ...don't remember but we'll all see....it has one convex and one concav side...do u say so in english??...and in this case i believe it could be pathological, in the case of the "hybrid" that started thrilling all our minds that should stay as open as possible, though scientifically based, i wonder if it couldn't be a case o gene codominance effect.
i have seen more than one person with one thumb like dad's and one like mom's and sometimes it is really great difference, or if u look at ears, it happens quite often they are different, like the thumb's case. So is it always true that mixed genes will give mixed results and in all parts of the body?? Nope!
I have met 2 people with one blue eye and one brown ( common in husky dogs).....normally brown is a dominant gene on blue, sometimes brown does not dominate on blu, they exist together, the person has an eye like dad and one like mom,  and the genes are codominant ( one will not silence the other, but they both express), could this be the case??? And what if ammonites reproduced like corals...just spreading all out in the stream and very close species( or subspecies in one same species group) could interbreed??? i don't know if a dog can with a fox, but surely with a wolf, and very different dog species give puppies...so?? R we sure ??? Curious to know your ideas.....Ciao for now!

ivano
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quagga
Hi ivano,
A variety of conditions cause heterochromia iridum ( different coloured irises http://en.wikipedia.org/wiki/Heterochromia_iridum ),It  can be inherited or due to injury, but does not appear to be due to codominance.  Dogs and wolves are essentially  the same species, so by that definition of course they can interbreed. [ and very different dog species give puppies...so??] I assume by this you mean dog breeds?  they too are all the same species.  If ammonites reproduced like corals, and very close species could interbreed, they would not form separate species.  Different species form, when differences prevent interbreeding happening, either behavioural or physical.
I would have thought that codominance would produce a blending of traits, not a bilateral division of traits.
Al

Time is nature's way of stopping everything happening at once.
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Bugg
i think olenus has hit the nail on the head, its def alien cross ammonite 

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ryanc
Olenus wrote:
Why should only one side be different? The liger is not one half lion and the other side half Tiger. its a mixture of both features. Same with the polar bear and grizzly bear. You dont get one side white and the other side brown.


 

Those are both mammals from the modern era and not a good basis for homology - I still think its most likely not the product of hybridisation but it would be foolish to rule it out based on our huge ignorance of how ammonites lived.

 

The history of science is littered with people who's 'common sense' idea's about things proved to be wrong and the long odds outsider won.

 

Regards,

 

Ryan
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fossils-uk
the history of science may well be littered with outsiders being right, but only after proving their theories throu scientific procedure and experiementation. With the history of science and in particular the history and study of palaeontology/palaeobiology the words "the presnt is the key to the past" is always taught from a very early stage. So from looking at the modern processes in landcsape formation or biological process we have to "safely assume" that the same processes have been going on for as long as the earth has been here. This can then be proven throu scientific analysis and experimentation. 
Therefore... there has been alot of research into the Modern Nautilus. its life habits, its biology, probably its mating cycles, damage and diesease of the shell. We know from looking at the structure of ammonite shells that they are very closely related to the modern nautilus. Ergo, ammonites must have lived and been biologically simliar to a nautilus. Therefore the answer we all seek is in the study of the modern nautilus. 
Both are closely related right.. do you ever see a Nauty-ammonite ? (only if its been bad eh? lol)
do you ever see a nautilus with nautilus features one side and ammonite on the other? But do you see pathologically deformed nautilus where the soft mantle has been diseased and the shell regrown in a funny way? 
I think it would be foolish to rule in hybridisation on this case.. as it seems like it was due to this pathological regrowth. like lee said you are you might as well say it was an intelligent designer that did it. lol ;-)
byron

fossils-uk, whitby
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fossil mad
I'm used to being the "black sheep "anyway everybody is entitled to their opinion,and i stick by it.
Poeple laughed at Darwin when he proposed his theory of evolution remember.

Byron, safe assumptions are just those assumptions.

I agree nauts and ammonites were closely related but you have to remember only one is now alive so they must have been significantly different for one to survive and the other to die out.

So you can't assume from studying one that's alive now,the dead one behaved exactly the same,it gives you an idea,but that is all,an idea.

 

The trouble with people is they want to believe a hybrid must be a mix of both parents producing offspring that is somewhere in the middle of each for size and looks etc.i.e very easy for the human mind to comprehend.

This is usually the case so no  problem,but what if once in one hundred million the mix of genes produced what we are discussing in this topic!

Too much for some minds?

Adrian
"When can we go fossil hunting again?"
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Olenus
Byron i could not of said it better myself! God be with you my son!
The Ace of Spades,,,







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ThomasM
A similar one can be seen on the old forum here.
Thomas

If you don't look, you won't find.
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ryanc
fossils-uk wrote:

Therefore... there has been alot of research into the Modern Nautilus. its life habits, its biology, probably its mating cycles, damage and diesease of the shell. We know from looking at the structure of ammonite shells that they are very closely related to the modern nautilus. Ergo, ammonites must have lived and been biologically simliar to a nautilus. Therefore the answer we all seek is in the study of the modern nautilus. 



 

No - it's now thought that Coleoidea (squids, cuttlefish and octopuses) are their closest living relatives  - the nautilus shared quite a distant ancestor with the ammonites.

 

Homology is somewhat better than nothing its not actual proof of how another organism lived especially an organism like the ammonite where you have no fossils preserving the soft tissue in great detail. 

 

It's not a good idea to assume that things that look similar must live similarly - the platypus looks a lot like an otter - if it was extinct we might assume a similar lifestyle yet it is venemous and lays eggs Tongue

 

Regards,

 

Ryan
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fossils-uk
okay being totally argumentive for augmentative sake now.. lol lol lol ;-) (tongue in cheek). 
so if coleoids were closer relatives how come you don't see a cuttlefish with an ammonite shell? or cuttlefish/octopus hybrid?
by assumptions (in particularly homology/comparative biology) i was referring to the fact that for instance a leg on a terrestrial animal was used in locomotion... therefore a leg in extinct animals must also functioned in a similar way. it is a "safe assumption"
a wing was used for flying.. therefore if you find a fossiised wing it was used for flying. 
therefore ammonites had a radula (fossils preserved ) as do coleiods and nautilus, a beak-like mouth (fossils preseved), an ink sac (fossils preserved), locomotion similar to coeloids and modern nautilus (ammonite trace fossils preserved). So is it presumptious to say that it is a "safe assumption" that we know a heck of a lot about an ammonite lifestyles. if we in fact observed these modern day animals? 
Therefore observing them cope with various pathologies we may well have a better idea on how ammonites coped with similar pathological situations.
The present is the key to the past.... or were my palaeontological lecturers making this statement up? lol 
a playpus and an otter is not a good example of homology sorry lol lol :-) anatomically very different comparatively speaking of course. ;-)
Sorry guys i am sitting in the damaged mantle caused the pathology on this particular ammonite. :-)
byron 
 
fossils-uk, whitby
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Olenus
Ryan... Quote... the platypus looks a lot like an otter - if it was extinct... would someone then say i have a theory! Its a hybrid with a otter and a duck. Lol this is Quackers.
The Ace of Spades,,,







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Ivano Ferri
Genetics have evolved quite a lot since i did my studies and medical degree!! That's a good thing to know, LOL!
I've been looking through my books and must say that though pathology is the appointed reason, it is supposed that the reasons why ammos are extinct while nauts are still alive are supposed to be bound somehow to the reproduction cycle, larvae were more delicate or had slower growth ..whatever. I find this discussion is very stimulating for fantasy as well as scientific speculation, though i believe we'll not get further than we have come so far. maybe one idea could be to send out a message to try find as many samples as possible, the germans are good at collecting pathological specimens and then try to differentiate in groups what may be what, this could lead to discovery of differencies we so far don't know about....i believe i have an ammonite with the siphuncle not being along the keel but moved on one side....for example....

ivano
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fossil mad
I agree,it is good to discuss different possibilities even though i don;t think we can go much further.
People will still be on one side of the fence or the other.I see there aren't many on my side though,but some are willing to think about the possibility.

Others just want to poke fun at a serious discussion or some of the people involved,never mind that is their choice and it certainly doesn't bother me or put me off.

I look forward to any other views and imput for either side of the discussion.

Adrian
"When can we go fossil hunting again?"
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ryanc
fossils-uk wrote:

by assumptions (in particularly homology/comparative biology) i was referring to the fact that for instance a leg on a terrestrial animal was used in locomotion... therefore a leg in extinct animals must also functioned in a similar way. it is a "safe assumption"

a wing was used for flying.. therefore if you find a fossiised wing it was used for flying. 

 

Ah - like in penguins

 

The closest relative of the elephant is the rock hyrax - http://en.wikipedia.org/wiki/Hyrax a small mammal that spends a lot of time up trees - the closest relative isnt neccesarily the species that looks most like them.

 

That ammonites closest relative is the coleoids opens up lots of interesting possibilities like the use of colour. Coleoids have fantastic colour vision and also have the capability to change their own colour by expanding/contracting bags of pigment in their skin for camouflage,defense and communication.

 

 
fossils-uk wrote:
So is it presumptious to say that it is a "safe assumption" that we know a heck of a lot about an ammonite lifestyles.

 

We arent even sure what they looked like, how many tentacles they had, arrangement of tentacles, whether they could use their siphons to propel themselves with a jet of water, how they bred, what stages their young went through, whether they were predators or scavengers etc. etc.

 

Those are just the basic questions that we cannot yet answer.

 

Regards,

 

Ryan
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spider
Some good points and 'extremes' to try and prove a point.  Without the evidence to back up any of the arguments though everybody is right (in their personal opinions) and until the next piece of the jigsaw is found, it could be a hybrid, or it could be a genetic mutation developing on an earlier shell form, and without the fossil record to prove either way, it may just stay an opinion :o)
Have a nice day :0)
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spider
PS. No one has mentioned the 'scientifically accepted' Androgynoceras hybridiforme as yet, widely thought to be the hybrid of Androgynoceras and Liparoceras where the inner whorls develop like an Androgynoceras then the outer whorl inflates developing Liparoceras type characteristics. oos for thought ;o)
 
Have a nice day :0)
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fossil mad
I've just read and seen these pictures,another very good argument for the cause!
strange its gone quite now!

Byron,Lee?explanations please?

Adrian
"When can we go fossil hunting again?"
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fossils-uk
Amaltheus, pleuroceras, Androgynoceras, oistoceras, and liparoceras are part of the same family the liparocertidae, with one evolving into to the other. It really is a great evolutionary chain to study. Spath did a wonderful monograph on this family with excellent plates. Androgynoceras hybridiforme is one of these species. But even though it displays a liparoceras body chamber it is not a liparoceras but an androgynoceras. I have also seen liparoceras looking body chambers on androgynoceras latecosta, and many oistoceras species from lyme regis. I would suggest that this is not a rare occurance and in fact probably androgynoceras hybridiforme is actually a diamorph of andogynceras maculatum (in fact possibly the macroconch female). Very little is know about sexual diamorphism in ammonite species to say one is a "hybrid" of another just cos it looks like it and as we know people used to put a species name to everything purely to out do their competing academic fellows. (Chapman andrew is one of them). even tough there are 20 different types of dactylioceras on the yorkshire coast i think half of these could be reduced down into a single diamorph species if give the time, money and study. The name hybridiforme is therefore misleading. However, androgynoceras maculatum is a transitional species toward liparoceras though. Evolutionary transitional species could be viewed as "hybrids" but i guess it would depend on how you would define a hybrid thou. Is this an adequate explanation adrian? 
 
fossils-uk, whitby
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fossil mad
I bow to superior knowledgeApprove
adrian
"When can we go fossil hunting again?"
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fossils-uk
 
fossils-uk, whitby
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ryanc
fossils-uk wrote:
I would suggest that this is not a rare occurance and in fact probably androgynoceras hybridiforme is actually a diamorph of andogynceras maculatum (in fact possibly the macroconch female). Very little is know about sexual diamorphism in ammonite species to say one is a "hybrid" of another just cos it looks like it and as we know people used to put a species name to everything purely to out do their competing academic fellows. (Chapman andrew is one of them). even tough there are 20 different types of dactylioceras on the yorkshire coast i think half of these could be reduced down into a single diamorph species if give the time, money and study.


 

Excellent and I think you are almost certainly right about the number of species that we could remove by a better understanding of sexual dimorphism in ammonoids. 

 

It's quite exciting to think how much basic science there is left to do in Palaeontology - there's so much more we can learn Smile

 

Regards,

 

Ryan
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spider
fossils-uk wrote:
Evolutionary transitional species could be viewed as "hybrids" but i guess it would depend on how you would define a hybrid thou.
 

 

So its thought that changes in the characteristics of ammonites could take place through hybridisation which is basically the possibility I outlined the beginning, the cross breeding of two species resulting in visible changes in shape of shell and these changes can occur gradually over a long period of time resulting in the small differences. Yep, thats what I thought was a possibility :o)
Have a nice day :0)
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fossils-uk
hi spider... well er... no.  Small changes could be the result in genetic mutations that accumulate over long period to create the new species. Like i said it depends how you term hybrid. you term hybrid as cross breeding of two species resulting in a brand new species. I don't think this way and i am sure there is a lot more to the creation of a new species than just simple cross breeding and you have a new species. If it did occur you would surely have to have fair number of this new species occur and both male and females to make this a viable breeding species in its own right. That is why genetic mutation is more likely to produce a new species over a long period of time compared to "hybridisation". sorry. 
byron
fossils-uk, whitby
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Olenus
Hello Adrian,...strange its gone quite now! Sorry i have been out collecting . Androgynoceras hybridiforme.. Liparoceras and Androgynoceras are ammonites belonging to the family Liparoceratidae have morphologically very heterogeneous shells. Intermediate forms between various types can also be observed during the ontogeny of individual species. Now if it was another family of ammonites with a Liparoceratidae . Then i would be a bit surprised.
As Byron says the name hybridiforme is therefore misleading!

 


Steves.. changes in shape of shell and these changes can occur gradually over a long period of time resulting in the small differences. Could this be Evolution! Yep i think so. Edited by Olenus 2011-05-01 22:18:55
The Ace of Spades,,,







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Naze Dave
Morphological classification has a lot to answer for lol.
Thanks
Dave
Still Life
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heath

I've been following this fascinating topic. Thanks Cambrian Rockhound for the interesting info. As the morphotypes appear to be grouped around male(micro) and female (macro conches), back to the original photos of bilaterally asymetrical ammos, could it be that one side is female, the other male? Perhaps a response to environment and breeding populations, such as some fish (guppies...) which can try to adjust the population sex balance when certain conditions apply. This would require genetics and hormones, rather than the idea of pathology/disease. I know nothing about the breeding of nautiloids, ammos!! Probably quite another story to my mental ramblings!


However I do agree that there's heaps of research to do, with no resources....but  with our enthusiasm... exciting perhaps!!!!!

over to you      Heath

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spider
Heath, very interesting thoughts and none of us are qualifed to comment really, no one has done any research in this area etc, its just all personal thoughts and ideas. I find it quite bizzare when you get a shell demonstrating the characteristics of 2 known species of ammonite, like the dac/hildy mutations. To do this the creature must of obtained the genes to enable this to happen. Its as simple as that. It cant happen by chance hence cant be the result of evolution. If it was evolution im sure there would be much more evidence to draw upon to follow these changes.  
Have a nice day :0)
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fossils-uk
we still havent seen a picture of this so called dac/hildy so i am afraid the jury is still out as i am sure you could easily get a dac with one side deformed (as seen in the arnioceras) but it has deformed in such a way (the shell that is, on one side) to RESEMBLE a hildy. I can see this happening. I cant for the moment see that it is dac one side and hildy the other unless faked at the moment and therefore i will reserve judgement until i see the facts. Also spider how many of these dac/hildys have you seen. I have seen one but again it was just a badly deformed dac that happened to deform in such a way that it resembled a hildy. 
If andyS can supply a picture for us that would be great. :-)
byron
fossils-uk, whitby
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Bill G
If they are x-breeds, they are very important fossils. If there has been no research carried out on the said specimens, (or similar ones if they exist), why have they not been submitted to a museum, so that they can be studied? If the owners don't wish to part with them, they can still be examined by experts and returned. They won't be described as new sp. though, unless given to the museum.
Cheers, Bill
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beatpete
Hi all
At university, a long time ago, I was told that evolution is about populations, hybridisation is about single specimens. That means that when you find, for example, weird ammonites with hybrid features, either you are lucky enough to have found the exact specimen that has been generated through cross-breeding (very unlikely) or you've come across a different species (most probable), whose features would be transmitted to the offspring; these features would respond to some external evolution-driving factor, such as different environment, large scale tectonic phenomena, etc. In any case, according to me, neither hybridisation nor evolution could be accounted for the abnormal, differentiated and asymmetrical growth of spines or other ornamentation on each side of the ammonite, that would definitely have problems in surviving, let alone transmit its new features to its offspring. One of the main distinctive features of ammonites is their symmetrical planispiral growth, and shells with asymmetrical ornamentation would be doomed to very quick extinction.

That means, making a long story short, that it is most probably pathology or damage that causes the strange growth.

On the other hand, it may happen that abnormal growths can result in making one specimen resemble some other species or genus, but I think that it does happen by chance, and that it could be the result of evolution - I think they called it "convergent evolution" when two different species, or genera, or even families or phyla, evolved into very similar forms - they gave us the example of a Brachiopod being exactly identical in shape to a Bivalve, can't remember the name, though.

 
Beatpete
----------------
Anywhere for little ammonites, twice as far for big ones!
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AndyS

Guys,

No need for a heated discussion here, the weird Arnioceras is just the result of a rare pathology where the shell secreting mantle was somehow injured to produce this "two face" result.

Here is a similar example that I posted some years back in the old forum :
It is a "two face" Hildoceras that has one normal side and one side that has lost the spiral groove and has some normal ribs instead :

twoface_hildoceras_veryverysmall.jpg 

This has happened early in the development of the animal, but the point in the shell where it happened is not preserved.

Another example is this (cast of an) Asteroceras that has the keel secreted on the side of the shell, thus producing a spiral appearance. It was caused by an injury to the mantle, the mantle was then stretched. The mantle location genetically programmed to produce a keel continued to do so, but was now on the side of the shell. With this specimen you can clearly see at what point in time in
the development of the shell the problem occurred, since the inner whorls up to about 1 cm are identical on both sides.

asteroceras_twoface.jpg 

Hereƒâ€š‚´s another example where a small Catacoeloceras started (symmetrically on both sides of the shell) to produce thicker & more wide spaced ribs after an injury :

Catacoeloceras_patholog.jpg 


As you can see from these examples, all sorts of weird pathologies can occur. The mantle of the animal seemed to be flexible enough to compensate for certain "gaps" or injuries. Even pathologies caused by parasites would seem possible.

It would be interesting to see if that Arnioceras had identical inner whorls.

AndyS

Visit my liassic ammonites (+ other fossils) blog at andysfossils.com
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fossils-uk
thanks andy,
nice pathological specimens there. I have had many pathological dacs in my time some with a saddle like injury, also i have had ammonite that have a smooth bevel area on the inner part of the whorls which was caused by a parasitic worm growing within the mantle as the ammonite grew also. these are very distinctive when found. 
So the dac/hildy of myth and legend (lol ) is simply a hildy that has a deformity to one side of the shell caused by mantle deformation (as suspected).

Has anybody else got pathological ammonites to show. I will see if i have pics in a mo.
cheers
byron


fossils-uk, whitby
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Bill G
Yes, thanks for showing them Andy.
Cheers, Bill
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beatpete
Hi all
Thanks, AndyS, that is exactly what I meant, pathology and not evolution or cross-breeding

---

Here is a pathological Dact, the ribbing is more proverse half way the last whorl (I had already posted it some time ago)

 

Dactylioceras_commune_path.jpg 

 

Cheers
Beatpete
----------------
Anywhere for little ammonites, twice as far for big ones!
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spider
Very strange how the deformity caused it to have dac like characteristics dont you think, but we shall completely ignore that, were back to 'pathalogical damage' explains everything, any deviation in normal shell growth, where infact it really explains nothing. What would cause a shell to completely change or alter its genetic profile apart from say producing a bulbous area to over come some form of damage?
Have a nice day :0)
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AndyS

Spider,

Both sides are not so different, really. A normal Hildoceras does have ribs, broken only by the spiral groove.
Take out the region of the mantle that produces the spiral groove (e.g. by a fish biting out that bit, or a virus infection or missing activation of the "spiral groove" gene on one side...), stretch the rest a little and youƒâ€š‚´ve got the "Dac" side. No need for genetic alteration / mutation, itƒâ€š‚´s all there - and sometimes the easiest solution is the most plausible.

Now that does not say that any sort of genetic failure in producing the sculpture of the "not normal" side can be ruled out, but it can not be proven. 

Looking at the pictures in the original post again, I find that the "not normal" side of the Arnioceras does indeed have "normal" inner whorls.

AndyS


Reading recommendation :
Sean B. Carroll : Endless Forms Most Beautiful. The New Science of Evo Devo.







Visit my liassic ammonites (+ other fossils) blog at andysfossils.com
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spider
spider wrote:
its just a thought and I havent seen it written anywhere.

 

Thanks Andy, Its a plausable explanation although I would of thought it would revert back to 'normal growth' soon after the pathalogical damage was repaired and the transition to the normal shell more gradual and less defineable, its been a good discussion :o)
Have a nice day :0)
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fossil mad
I can follow all this,but the dac characteristics are produce in its youngest stage,on the otherside i see a hildi in its youngest stage.
As the ammonite matures the "Dac side seems to turn more hildi looking,surely if damage caused to the dac side was done at a young age this would have carried on into sub adulthood/maturity.

 

Or could this be because the hildi was maturing and different hormones made it produce a different shell type.

Or was it a hybrid between the two and the hildi hormones won as it matured?
"When can we go fossil hunting again?"
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AndyS

Fossil Mad,

I guess we can agree on that the "normal" Hildoceras (and thatƒâ€š‚´s true for all lias ammonites known to me) is a fully symmmetrical shell ?
Remember, hybridization is a normal egg & sperm process, which again normally creates a fully
symmetrical shell
- because itƒâ€š‚´s in the genes (called the HOX genes) setting up the "general design" of the animal. So what is true for one species on ammonite we can see, must normally be true for other species as well (that symmetrical "bauplan" only deviates towards the end of the evolution of the ammonites - which must have had some evolutionary advantages or was simply an unimportant factor in an abundant ecological niche) so the hybrid would also be symmetrical. An asymmetry can for liassic ammonites to my mind only be created by pathologies - however they came to being, but not through a genetic setup that produces asymmetry.

The spiral groove does actually not re-appear on the outer whorl, only the overall characteristics fade (the sculpture gets less pronounced) on both sides of the shell as we normally see with Hildoceras.

AndyS

Visit my liassic ammonites (+ other fossils) blog at andysfossils.com
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Olenus
So its not a hybrid. They are pathological specimens. Thank you for showing them Andy they are very interesting.
The Ace of Spades,,,







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Naze Dave
Hi Andy
I agree with your view that genetics wouldn't be the reason for this asymmetry. Looking at modern day organisms, hybrids usually show a blend of the parent characteristics, so in this case surely the ammonite would have rib patterns that are a blend of Dac and Hildy but still symmetrical, rather than an assymetrical shell with half Dac and half Hildy.
Thanks
Dave
Still Life
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tortoise

This has been an interesting discussion. While I'm not suggesting that this is the cause here, there is a condition which can result in dramatic variations between one side of an animal and the other - bilateral gynandromorphy where one half of the individual is male and one half is female. Its been documented in birds and crustaceans (don't know if its been recorded in Cephalopods) There's an article with pictures here


Andy

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spider
Andy, definately another possibility thanks for the article,  pathalogical deformity seems to be the most popular 'theory' although still impossible to prove or substantiate either way, just like the rest of the ideas Wink
Have a nice day :0)
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AndyS

Andy(T),

Thanks for the pointer - very interesting indeed !

If it existed in ammonites and gynandromorph ammonites would be found
it would certainly solve some of the microconch/macroconch riddles...

but wait...

I read something about 200 gynandromorphs in 9 million butterflies in the NHM collections.
Take into account a big collection bias for these rare creatures, i.e. almost all gynandromorphs found will be preserved, drastically misrepresenting the true ratio.
For the sake of calculation, say itƒâ€š‚´s 1 in 100 million.

Assuming it existed in ammonites :
Odds of preservation of ammonite shells : 1 : 10000 ?
Multiply that by 100 million, I make that 1 : 1000 billion
Multiply that by your chances of being at the right spot at the right time (bed with fossil is exposed, is not eroded yet, youƒâ€š‚´re at the spot and you actually SEE it....)

Pfffft...almost impossible.
But still, fossils like Archeopterx have been found, so itƒâ€š‚´s not ZERO.
Iƒâ€š‚´d like to see a soft tissue preservation ammonite first, please...

AndyS 


Edited by AndyS 2011-05-07 19:16:41
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quagga
Interesting idea Andy, however, I believe extant cephalopods only have a single gonad, so a bilateral gynandromorph would seem an unlikely occurrence (assuming the same for ammonites), but who knows eh?.
Al

Time is nature's way of stopping everything happening at once.
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