Colossal Ammonite from Canada

Wow! :shock:

Have to say, I wouldn't want to be the student who'd made the truck tire ID... though it does lend support to the Monster Truck Formation theory!! :wink:

If they raised a mammoth why can't they raise an ammonite (funds for extracting something like this should be simple to generate)???? I'd be getting a helicopter in there and extracting that thing in no time!!!! How could they leave it there?

That’s quite an interesting question. Most people are aware of the spiral forms of ammonite but there were plenty of other forms known as heteromorphs that adopted all sorts of unusual shapes. Some resembled corkscrews, such as Bostrychoceras, others, such as Hamites were bent in a U shape, and some, such as Lytocrioceras, looked like a safety pin! Probably the strangest ammonite was Nipponites which just looked like a twisted mass, like some form of plumbers’ nightmare.

Most of these forms, though by all means not all, date from the late Cretaceous period (145-65mya) and are widespread across the world. It is difficult to think of an particular ecological niche that these peculiar forms could have filled but obviously there must have been some ecological advantage to be gained by attaining these forms. Certainly there have been studies undertaken in attempting to ascertain the angle of floatation of these creatures in order to determine lifestyle and behaviour. The helically coiled ammonite such as Bostrychoceras mentioned above is thought to have corkscrewed its way through the water, perhaps ascending to the surface during the night and descending during the day as do so many cephalopods today.

It is difficult to imagine our Antarctic friend here adopting this method of lifestyle due its size and bulk so perhaps it was a bottom feeder, head on the seafloor with that peculiar tube jutting upwards to keep it buoyant. (That’s my speculation, by the way!).

I believe that it used to be thought that these peculiar ammonites were bizarre inadaptive evolutionary dead-ends but that is a view that is no longer widespread. Some of the uncoiled or partially coiled Early Cretaceous heteromorphs then led on to produce descendants with almost ‘normal’ coiling proving that if the ecological niches were there, the ammonite was eminently adaptable.
Steve O'Shea said:
How could they leave it there?
Looking at the picture, there is not much there to really study. The septate coils are missing, only an external mold remains. And there is an Internal mold of the Living Chamber. No shell or sutures to be seen, there might be a mold of the last chamber on the end of the Living Chamber mold, but it dont look like its there. Several latex casts have been made, according to the article, so any exhibition piece (or Monster Truck Tire molds) could be made and painted up from them (a common practice for paleontological exhibitions). Invertebrate paleontologists don't seem to get as much funding as vertebrate paleontologists (a pair of dinosaurs beats a royal flush of ammonoids for some reason). I believe that is why they have left it there.

Well, I noticed all the diversity in ceph designs across the entire Class, from basic form to suckers, etc. and I think that the Class is experiencing an explosive evolutionary time. But why did the shelled cephs suffer so badly? How long have the "unshelled" forms existed, and why are they doing so well now?

Sushi and Sake
I'm not entirely convinced that one could argue that cephalopods are undergoing an evolutionary explosion. After all, one could argue that the class has been somewhat reduced since the Cretaceous period following the disappearance of the ammonites and belemnites. Indeed, the nautiloids dominated the worlds oceans during the Ordovician period, covering quite a number of orders, but are now reduced to just five species. They certainly have not undergone any evolutionary explosion and have barely changed in over 100mya or so.

The problem in attempting to ascertain prehistoric cephalopod diversity is that fossils of squid and octopi are extremely rare, obviously soft-bodied creatures require very specific environmental conditions to fossilise, and we require a great deal of luck in being able to find the deposits. (The Solnhofen Jurassic squids are a notable example of when this does happen). Hence it is difficult to ascertain how diverse the coleoids were in the past to make comparison to the present. There were certainly giant squids in the late Cretaceous, and squid and octopi appear to have evolved in the Jurassic. (There is an extremely controversial 'squid' from way back in the Devonian called Eoteuthis, but whether or not this really was a squid and the interpretation of the soft bodied parts, if that is what the staining on the fossil is, has been the subject of much debate).

Personally I think the class cephalopoda has not shown any great
evolutionary leaps in the last 140 million years or so and has been somewhat reduced, largely due to a mass extinction and the explosive radiation of the fish in the early Tertiary world providing direct competition in many ecological niches. This is not to say that they are not a success, on the contrary the Teuthoidea seem to be very diverse group, but, unless fish disappeared from the oceans I cannot really see the cephalopods exploiting new niches and adapting and evolving new forms at an order level. (That's just my opinion, by the way)!

That’s the best thing about soft-bodied cephalopod fossils, there is so little known, you can theorise all you like!

Off to the pub now!

I see your point, but I think that the discovery of large teuthoids seems to indicate an ecological importance in the modern day oceans. I see what you mean about theorizing all we like; truth is, I see a lot of diversity between various species themselves, but little across the board class-wise. Yeah, the vertebrate rule has put the cephs on the back burner apparently, but I'm not entirely convinced that its so cut and dry.

Thanks for the great info! You've given me a lot to think about.

Sushi and Sake,

Phil said:
I'm not entirely convinced that one could argue that cephalopods are undergoing an evolutionary explosion. After all, one could argue that the class has been somewhat reduced since the Cretaceous period following the disappearance of the ammonites and belemnites.

Oh gawd, did I really write that a year ago? Can I take it back? I really don't agree with much of that post of mine after reading bits and pieces over the last year. It was somewhat limited perspective, cephalopods positively bloomed in the Tertiary, even if the variety of basic cephalopod body plans is currently less than it was....

Oh well, you live and learn, I suppose.
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