Nautiluses have suckerless tentacles as described above so perhaps ammonites had the same arrangement. Whether they had suckers at all or not is hard to say. Given that these have never been found in association with ammonite fossils, they probably did not possess them. Hooks and beaks are found in stomach contents of marine reptiles like plesiosaurs and ichthyosaurs. These hard parts do preserve in the fossil record and are sometimes the only evidence of cephalopod species. ![]() Did they have hooked or toothed suckers?Īs mentioned above hooks have been found in the extinct belemnites and living species of squids sometimes possess hooks or suckers with toothed chitinous rings. There was probably a great diversity of arm types and number across the group as we see in modern cephalopods which have specialised webbed arms like in Argonauta, suckerless lure tentacles as in Grimalditeuthis and retractile filaments as in vampire squid. It’s likely that the ammonites possessed multiple paired appendages but paired clubbed tentacles is highly speculative. In terms of adaptation, tentacles in free swimming squid and cuttlefish are used for ambushing or snatching prey and have been lost in bottom dwelling octopuses. Although superficially the chambered shelled nautiluses resemble the fossils of ammonites, they are different groups so a similar arrangement shouldn’t be assumed. Belemnites, an extinct group of cephalopods, had small hooks on their arms which are sometimes preserved and from these fossils it appears that they had ten arms but no tentacles. ![]() In nautiluses it refers to the 90+ arm like appendages arranged around the mouth and under the eyes. In ten-appendaged cephalopods like squids and cuttlefish, tentacles refers to the the two long arms with suckers only present on a club at the end. Even within living cephalopods it is inconsistently used. Did they have suckers and/or tentacles?Ĭonfusingly, tentacle is a very widely used anatomical term and not a strictly consistent one. So it falls to looking at the distant living relatives and some of the better known fossil cephalopods to speculatively inform how ammonites may have looked and lived to explore some basic questions about these animals. Image modified by the author- cropped and enlarged section to show detail. Widely reproduced and copied image Duria Antiquior: Animals and Land Plants of Dorset in the Liassic Period this version by Henry Thomas De la Bèche. Exceptional trace fossils like the ‘zombie’ ammonite give us an incite into tiny moments of the geological past. Ammonite stomach and crop analysis suggests that bivalves, crustaceans, sea urchins, sea lilies (animals related to sea urchins and starfish) and other ammonites were what they fed on (Jager and Fraaye 1997). 1998) and it has been hypothesised that empty ammonite shells were the first group of molluscs that hermit crabs adapted to inhabit (Fraiije 2003). Their beaks have been found in the stomach contents of plesiosaurs (Sato and Tanabe 1998), their shells are sometimes encrusted by other inverterbates (Kase et al. Ammonites were widely distributed and have been found globally in marine deposits.Īmmonite fossils tell us a lot about ecosystems and other animals that inhabited the same environment. It’s difficult to estimate the number of described species of ammonites and few sources even attempt to do so.Īs fossils, ammonites are found in Jurassic and Cretaceous rocks and found in such abundance with rapid evolution of forms that make them useful in biostratigraphy a branch of stratigraphy that uses fossil organisms to date, correlate and interpret the geological record. Ammonitida, is the order most commonly used synonymously with ammonites. Scientific naming conventions are such that technically, ammonites are ammonoidean, ammonitidan, and sometimes strictly ammonitinan cephalopods. Taxonomically, ammonites are just one group of ammonoids, a group which includes other shelled cephalopods which first appear in the Devonian period 410 million years ago. ![]() Early 20th Century reconstructions showing very nautilus-like fleshy hoods, tentacle mass and colouration Photograph: Ammonoid by Heinrich Harder
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