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Nipponites - The Ultimate Weird Ammonite?

Phil

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It’s been a while since we had a new topic here so I’d thought I’d post an image of Nipponites, arguably the weirdest and most derived form of ammonite that evolved.

Nipponites is known from the Late Cretaceous period from Japan (approx 93-85 mya) and is clearly peculiar as the shell did not grow in the usual spiral shape but in a series of ‘U’ bends alternating in the X, Y and Z axis. The result was a shell resembling a nightmarish twisted mass. The shell still contained the complex ammonite suture lines between the body chambers and had simple ribs. The final chamber of the shell was slightly recurved and would have hung below the shell so that the head of the animal would have been angled somewhat downwards.

As one can imagine, the ammonite would have been a very poor swimmer as demonstrated by its non-streamlined shell. Some researchers think that Nipponites would have been jellyfish-like in its feeding habits, hanging and drifting in the open water, ensnaring small animals with long trailing tentacles.
 

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Phileas, how bizarro. caught my 1st look at 1 of these just couple of days ago in part of my new biblioteque. you're well tuned in to the needs of your knicker throwing fanclub & old gits like me alike ! :notworth:

Obvious that sometimes hydrodynamics aren't an issue
 

Steve O'Shea

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Re: Nipponites - The Ultimate Weird Ammonite?

Phil said:
It’s been a while since we had a new topic here so I’d thought I’d post an image of Nipponites, arguably the weirdest and most derived form of ammonite that evolved.
Inconceivably bizarre Phil! OK - internal/external shell, who knows ... but I can't imagine that being a pelagic beast if external. What chance is there that the 'shell' was soft/non-calcified, and what you are looking at is the thing all collapsed on itself (excuse the analogy, but like a 'turd' coils, or a long corrugated plastic tube coils [eg, vacuum cleaner hose] all over the show). If the shell was buoyant, whether fluid or air, not- or only very weakly calcified, and buoyancy was slowly lost, post mortem, over time, then the buoyant parts would slowly collapse on top of the latter chambers, with accelerated sedimentation contributing to the 3D x/y/z shape - a coiled/collapsed turd-like multi-dimensional structure.

Just doesn't look right ... and the rendition, animal in situ .... albeit a great pic .... I'm afraid I just can't see that happening (although I can see why you/someone has done this). Oh for that time machine! Was it benthic (what other fossils are associated with an ammonite like this ... sponge spicules?); did it drill into something; did it 'drill' into the mud, with all but the last chamber protruding through, with a little octopus-like thing that could crawl about, actually leaving the last chamber, in search of foodstuff (when it got dark). Questions, questions, questions ...... Aptychii known from this thing? Radula? Muscle scars in last chamber?

How similar are the shells of this beast - are they all so irregular (consistently so), or are they all over the show?
 
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Re: Nipponites - The Ultimate Weird Ammonite?

Steve O'Shea said:
Phil said:
It’s been a while since we had a new topic here so I’d thought I’d post an image of Nipponites, arguably the weirdest and most derived form of ammonite that evolved.
Inconceivably bizarre Phil! OK - internal/external shell, who knows ... but I can't imagine that being a pelagic beast if external. What chance is there that the 'shell' was soft/non-calcified, and what you are looking at is the thing all collapsed on itself (excuse the analogy, but like a 'turd' coils, or a long corrugated plastic tube coils [eg, vacuum cleaner hose] all over the show). If the shell was buoyant, whether fluid or air, not- or only very weakly calcified, and buoyancy was slowly lost, post mortem, over time, then the buoyant parts would slowly collapse on top of the latter chambers, with accelerated sedimentation contributing to the 3D x/y/z shape - a coiled/collapsed turd-like multi-dimensional structure.

Just doesn't look right ... and the rendition, animal in situ .... albeit a great pic .... I'm afraid I just can't see that happening (although I can see why you/someone has done this). Oh for that time machine! Was it benthic (what other fossils are associated with an ammonite like this ... sponge spicules?); did it drill into something; did it 'drill' into the mud, with all but the last chamber protruding through, with a little octopus-like thing that could crawl about, actually leaving the last chamber, in search of foodstuff (when it got dark). Questions, questions, questions ...... Aptychii known from this thing? Radula? Muscle scars in last chamber?

How similar are the shells of this beast - are they all so irregular (consistently so), or are they all over the show?
Yup, I wondered if it were benthic. Are there a lot of these beasties? are they consistantly found like this, i.e. the same general shell morphology? Do you ever find encrusting 'stuff' on the shells?

On a lighter note a friend of mine has this theory that when god first started creating animals he wasn't too good at it and had a few shockers, he didn't want to kill them, so he put those at the bottom of the ocean where no one could see them.
 
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I was just thinking a little farther and you do get this kind of loose coiling in the New Zealand members of the Vermetidae and Siliquariidae.

These animals are all sessile to the best of my knowledge, the Vermetdae tend to be attached to rocks and shell and the Siliquariidae encased in sponge.

I get to talk about shells 8)
 

Phil

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Thanks for the replies Matt and Steve. Interesting to draw parallels with marine gastropods, Matt. I know nothing about how they grow, any chance you could shed some light? I looked up Vermetidae, and I see exactly what you mean!

Steve, I am sure that the unusual shape of Nipponites mirabilis is an accurate reflection of its original shape and not caused by the collapse of a soft shell. Many specimens have been found in different locales (mainly Japan, but also Kamchatka and the USA) and all seem to exhibit the same shape and structure, i.e an interconnecting series of U-bends. If this was a collapsed shape then I would have thought there would be more variety in the shape of the fossils, and the specimens would be more fragmented; from the photos I’ve seen of these specimens the cross section of the shell seems to retain its near-circular shape along the length of the conch without obvious deformation in places that one would expect from a collapsed structure.

In addition, Nipponites shells were composed of aragonite, the same as most other ammonites and obviously a tough substance. As far as I have been able to determine, I don't think the mineral composition of the shell was any different to most other ammonites of the period. A fragment of this can be seen in the image below. The ammonite has also been explained via computer modelling; this link clearly demonstrates that there is indeed a regularity to the construction. The link above shows that during its growth the animal rotated within the shell by 2 radians every 0.6 whorl; if a constant growth rate is maintained the shape of the shell is, in fact, perfectly predictable.

Interesting that the earliest interpretation of Nipponites was that it was a diseased example of another form of heteromorph ammonite.

As for benthic/pelagic, well that has been the subject of much debate amongst researchers. Admittedly it is very hard to imagine this animal swimming, as it clearly is totally unstreamlined. Apparantly most ammonites do not even display a hyponomic sinus, including, I think, Nipponites. Without a siphon, an irregular shape and a mantle cavity of inefficient shape to generate a jet of water it is unlikely that this ammonite could have swum at all. It is much easier to imagine it either as a passive drifter in the plankton, or as a benthic creature crawling along the substrate using the shell as a form of mobile burrow. It would be interesting to find out what sort of sediment these ammonites are preserved in as that might indicate what sort of habitat this animal lived in. (Will try and find out).

By the way, this text by Neale Monks may be in interest as it sheds a great deal of light on heteromorph ammonite orientation.
 

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Snafflehound

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Genetics?

What is the possibility that the weird shell is the result, not of a "disease" but a recurring mutation - for instance, something like acromegaly in humans - where instead of coiling normally like the other ammonites, the shell curls in the bizarre manner shown. What I'm asking is, could these be not a new species, but an occasionally occurring variant of some existing species, that have an extra or missing chromosome, or two copies of a shell-curling gene, or something like that?
 

Phil

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Hi Snafflehound,

Nipponites is certainly regarded as an species in its own right. You may well be right about mutation, makes sense to me. Unfortunately what I know about the mechanisms of genetics I could write on the back of a postage stamp (in large letters) so I can only speculate too!

The ammonite order Ancyloceratina, which appeared in the Late Jurassic, produced most of these peculiar heteromorphs, maybe as you say, from mutations within the Lytoceratina, some of which were developing uncoiled shells at that time. There was a huge explosion of ammonite forms, especially the Ancyloceratina, in the Lower Cretaceous as the Earth underwent a global rise in temperature.

The Ancyloceratina remained widespread throughout the rest of the Cretaceous, unlike the other ammonite orders which declined markedly. Most members of the Ancyloceratina are, I believe, distinguishable by a hook shaped body chamber hanging beneath the shell. Nipponites probably evolved from a helically coiled ammonite similar to Bostychoceras (pictured here). It does not take a huge leap of imagination to envisage an uncoiled ammonite similar to this one mutating and developing into a form similar to Nipponites. As an aside, it has been speculated that the Turrilitaceae, such as Bostychoceras, may have cork-screwed their way through the water undertaking the daily vertical migration from the depths sweeping the water for plankton with their delicate tentacles as they spun.

It used to be thought that these heteromorphs were degenerate in some manner, or over-specialised, but the fact that they became one of the widespread and successful ammonite groups by the late Cretaceous would seem to belie that idea. The peculiar fact is that later in the Cretaceous some members of the Ancyloceratina actually reverted back to the more traditional spiral ammonite form and their suture patterns actually simplified, indeed at the very end of the Cretaceous most of the few remaining ammonite groups had near normal coiling. The overall decline in ammonite numbers and forms is thought to have been due to environmental conditions as opposed to a weakened genetic stock.

Sorry that’s not exactly the answer you were looking for!

Phil
 

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Neale Monks

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Phil,

Thanks for the heads-up on this thread. Nipponites is certainly one of the oddest looking heteromorph ammonites, but if you look at in in the context of the family of heteromorphs it belongs to (the Nostoceratidae) it becomes a bit less bizarre. It also helps to know something of the origins of the group.

The Nostoceratidae are an offshoot of the Turrilitidae, which come from the Hamitidae. Now, the Hamitidae as adults were flat, either open spiral or paper-clip shaped beasts. But soon after hatching, many of them became helically coiled. The helix went on for two or three complete whorls, then straightened out.

http://homepage.mac.com/nmonks/ammonites/hamites.html
http://homepage.mac.com/nmonks/ammonites/hamites_attenuatus.html

You also see the same basic shape appearing among another family, the Anisoceratidae, apparently independently.

http://homepage.mac.com/nmonks/ammonites/heteroclinus.html
http://homepage.mac.com/nmonks/ammonites/anisoceras.html

My guess is the helix was a pre-requisite to the paper-clip shape, allowing the two or three straight shafts to be tucked neatly under the helix. If the helix wasn't there, the shell would bump into itself as the ascending arm of the "u bend" came back to where the spiral was. As luck would have it, the spiral also served the juveniles well during the early drifting stage of their life. It held the animal head downwards, and ambient water currents would cause the shell to rotate, allowing a much more efficient sweeping of the water for food.

Anyway, as time wore on, some ammonites 'concentrated' on this helical phase of life, becoming neotenic, that is, the adult morphology became increasingly similar to the juvenile one. The earlier members of this line (like Hamitella) of evolution had extended helical phases followed by a much shorter final hook than their ancestors. One lineage led to species that lost virtually all traces of the final hook, the only evidence of adulthood being maybe a loosening of the helix and the presence of apertural modifications such as constrictions and thickened ribs. The helix also became increasingly close and pointed.

http://homepage.mac.com/nmonks/ammonites/hamitella.html
http://homepage.mac.com/nmonks/ammonites/turrilitoides.html

This lineage eventually gave rise to the Turrilitidae including things like Turrilites and Mariella. In parallel, the Anisoceratidae produced their own fully-helical forms (the genus Pseudhelicoceras) but apparently that didn't lead to anything and died out at the end of the Albian. See Text Figure 6 in my paper on Albian heteromorph radiations for a summary of this. It's interesting that both groups did this helical coiling thing at the same time, the middle part of the Albian.

http://homepage.mac.com/nmonks/Resources/cladistics_albian_heteros.pdf

The Turrilitidae, with their simple helical shells, do seem to have had functioning siphons for jet propulsion (their shells had "spouts" coming from the aperture like truncated versions of the siphons seen on gastropod shells).

The Nostoceratidae are a specialised offshoot of the Turrilitidae that appeared somewhere close to the Cenomanian - Turonian boundary and survive right to the end of the Cretaceous. They are generally helical initially but then have a hook-shaped living chamber. Unlike the hooks of the Hamitidae, which are in the same plane as the helical coiling, the hooks of the Nostoceratidae are perpendicular to the helix and sort of hang underneath the spiral like a gondola. There are all sorts of variations, but what does appear to be happening is the animals have become completely specialised for a planktonic lifestyle with little if any swimming ability. They do not have the "spouts" seen in the Turrilitidae and in many the final aperture is recurved into the main whorl of the shell.

While the shell coiling was weird, in other regards these are conventional ammonites. The shell is solid, not flexible, and the chambers have the same complex quadrilobate sutures as the other heteromorphs. This is good evidence that they retained the same buoyancy function as other ammonites (so they weren't benthic crawlers at least).

Nipponites is a lot _less_ weird when you see it in context of the entire family it belongs to, the Nostoceratidae. There are clear 'experiments' in finding the right balance between shell shape and orientation, and presumably defence and cost of construction as well. Most the Nostoceratidae (and indeed many other heteromorphs) have shells that can be considered as "stable" -- that is, like a balloon, they are self righting, so that if a water current pushed the aperture upwards, gravity would bring it back down again. Why stability was such a big deal is unclear.

Many also coil in such a way that the initial spirals are hidden inside the later ones, so perhaps defence was an issue. Maybe the thinner, early shell was more vulnerable than the later, thicker shell, and so Nipponites kept the early whorls tucked away inside. Often overlooked is the effect of size on predation: a small but globose shell is less easily attacked than a big, flat one. Midwater predators need to take the thing into their mouths whole, so if something was ball shaped (like Nipponites) it would be difficult to bit compared to something that was flat (like Hamites) that could be bitten much more easily. Among gastropods, this does seem to be the reason for spines rather than spikiness _per se_.

Anyway, the bottom line does seem to be that Nipponites is a genuine species (not a freak) and simply a more extreme example of a family that was doing all kinds of odd things. While they look strange, the fact that the Nostoceratidae were doing so well in the latest Cretaceous does seem to indicate that they were adapting to a changing world that the other ammonites, which were doing badly, were unable to do.

Cheers,

Neale
 

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