barkerj Posted February 25, 2011 Share Posted February 25, 2011 I just discovered Spirula http://en.wikipedia.org/wiki/Spirula, and it got me wondering. Why do we assume that ammonites, but especially scaphites, lived inside their shells rather than around them like Spirula do? I can understand ammonites because they resemble the nautilus. A Scaphites shell, on the other hand, (especially one like my Scaphites warreni (or is it whitfieldi)) looks too clumsy to go on the outside of the animal. Can someone with more education on the matter enlighten me? Link to comment Share on other sites More sharing options...
Auspex Posted February 25, 2011 Share Posted February 25, 2011 Great question... Would external ornamentation on the shells counter indicate their being an internal structure? "There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant “Try to learn something about everything and everything about something.” - Thomas Henry Huxley >Paleontology is an evolving science. >May your wonders never cease! Link to comment Share on other sites More sharing options...
tracer Posted February 25, 2011 Share Posted February 25, 2011 a number of marine shelled inverts sort of flow out and around their shells partially. but it seems like most that do that have smooth, non-irritating external surfaces to the shells. some of the ammonites i've found have quite a bit of surface texture, and in some cases even seem "armored" with spines, like the trachyscaphites s. spiniger from the north sulphur river. it seems as if a frame of reference for what earlier creatures were like has been assumed by many from the characteristics of the extant chambered nautilus, but it would not surprise me to learn that there was a continuum of internal/external functioning by various creatures of ammonitic persuasion. i suspect those who figure stuff out and publish their figurings color outside the lines more as it pertains to soft-body-part hypothesizaliances than would be considered prudent if they were instead deciding whether to cut green wires or red ones. your mileage may vary Link to comment Share on other sites More sharing options...
Darwin Ahoy Posted February 25, 2011 Share Posted February 25, 2011 I've actually been wondering about this recently myself. Has there been a fossil of an ammonite with tentacles, etc. intact found? Something that actually shows us what they looked like? Link to comment Share on other sites More sharing options...
Aramon Posted February 25, 2011 Share Posted February 25, 2011 (edited) Has there been a fossil of an ammonite with tentacles, etc. intact found? No, never, and the why is a great mystery But Aptychus are considered as ammonites jaws and sometimes opercules. In situ Aptychus are inside the shell. Moreover muscles attachments are known inside the body chamber and not outside. Thus ammonites were probably not like Spirula but rather like Nautilus, even if they are considered close to the actual squids. Edited February 25, 2011 by Aramon Link to comment Share on other sites More sharing options...
barkerj Posted February 25, 2011 Author Share Posted February 25, 2011 But Aptychus are considered as ammonites jaws and sometimes opercules. In situ Aptychus are inside the shell. Moreover muscles attachments are known inside the body chamber and not outside. Thus ammonites were probably not like Spirula but rather like Nautilus, even if they are considered close to the actual squids. I probably shouldn't have mentioned ammonites since I was actually wondering about Scaphites. Most Ammonites seem pretty obviously similar to the nautilus. Sorry for being confusing:( Scaphites like the one in my profile pic, however, are puzzling to me. I have a hard time imagining them swimming around like that with their little heads bumping into their shells all the time. I can accept that the ornamentation in the form of ribs might indicate that the shell was on the outside. I wouldn't really know, but the ribs don't seem like they would be much of an inconvenience on the inside and may have given the animal some visible texture even there. Link to comment Share on other sites More sharing options...
Aramon Posted February 25, 2011 Share Posted February 25, 2011 I probably shouldn't have mentioned ammonites since I was actually wondering about Scaphites. Most Ammonites seem pretty obviously similar to the nautilus. Sorry for being confusing:( But Scaphites is an ammonite. Have I missed something in what you would meant? Link to comment Share on other sites More sharing options...
barkerj Posted February 25, 2011 Author Share Posted February 25, 2011 But Scaphites is an ammonite. Have I missed something in what you would meant? Right. But, I meant Scaphites specifically and not the more well known smooth, large and symmetrical ammonites. Link to comment Share on other sites More sharing options...
Aramon Posted February 25, 2011 Share Posted February 25, 2011 Ok! But this is exactly the same thing with Scaphites and the other Mesozoïc ammonites: jaws and radula are inside the body chamber Link to comment Share on other sites More sharing options...
tracer Posted February 25, 2011 Share Posted February 25, 2011 i believe i've read some of the ammonites with morphology like scaphites are more coiled as kids and then more opened up as they grow up. i originally thought that was so they could pedal aquacycles better, but i've since reconsidered and think they do in fact get tired of having their rear in their face all the time and so unwind a bit to lessen that effect. but their lot in life isn't really all that different from those dogs which are not the lead dog on a sled team. the view is always the same... i just can't imagine the shell having been an internal feature on scaphites, cuz they would have been sore and angry all the time. not sure what micro-environment they inhabited. if the shell was mainly for buoyancy and protection then maybe they didn't need to be very sleek and speedy and therefore poked along just fine until, um.....they became extinct, poor babies! Link to comment Share on other sites More sharing options...
barkerj Posted February 25, 2011 Author Share Posted February 25, 2011 But this is exactly the same thing with Scaphites and the other Mesozoïc ammonites: jaws and radula are inside the body chamber Jaws found inside shells is a good enough explanation for me. Thanks! Link to comment Share on other sites More sharing options...
Terry Dactyll Posted February 25, 2011 Share Posted February 25, 2011 It is a good question... Look at the oxycone shaped shells, its a tight fit to live inside that... Cheers Steve... And Welcome if your a New Member... Link to comment Share on other sites More sharing options...
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