Editing Ammonoidea (section)

==Soft tissues, life appearance and ecology==
[[Image:Ammonite Asteroceras.jpg|thumb|''[[Asteroceras]]'', a Jurassic ammonite from England]]
Because ammonites and their close relatives are extinct, little is known about their way of life. Their soft body parts are very rarely preserved in any detail. Nonetheless, much has been worked out by examining ammonoid shells and by using models of these shells in water tanks.
[[File:Ammonite soft tissue diagram.png|thumb|330x330px|Diagram of ammonite soft tissue anatomy based on other cephalopods along with a cross section (right). Note that shape and length of tentacles are speculative.]]

Although ammonites do occur in exceptional [[lagerstatten]] such as the [[Solnhofen Limestone]], their soft-part record is surprisingly sparse. Beyond a tentative ink sac and possible digestive organs, no soft parts were known until 2021.<ref name="Wippich2004">{{Cite journal |last1=Wippich |first1=M. G. E. |last2=Lehmann |first2=J. |year=2004 |title=''Allocrioceras'' from the Cenomanian (mid-Cretaceous) of the Lebanon and its bearing on the palaeobiological interpretation of heteromorphic ammonites |journal=Palaeontology |volume=47 |issue=5 |pages=1093–1107 |bibcode=2004Palgy..47.1093W |doi=10.1111/j.0031-0239.2004.00408.x |doi-access=free}}</ref><ref name="Klug et al 2021">{{cite journal |last1=Klug |first1=Christian |last2=Schweigert |first2=Günter |last3=Tischlinger |first3=Helmut |last4=Pochmann |first4=Helmut |date=December 2021 |title=Failed prey or peculiar necrolysis? Isolated ammonite soft body from the Late Jurassic of Eichstätt (Germany) with complete digestive tract and male reproductive organs |journal=[[Swiss Journal of Palaeontology]] |volume=140 |issue=1 |pages=3 |bibcode=2021SwJP..140....3K |doi=10.1186/s13358-020-00215-7 |pmc=7813712 |pmid=33505352 |doi-access=free}}</ref> In this year an isolated specimen showing some of the internal soft anatomy including organs was described.<ref name="Klug et al 2021" /> When [[neutron imaging]] was used on a fossil found in 1998, part of the musculature became visible and showed they were able to retract themselves into the shell for protection, and that the retractor muscles and hyponome that work together to enable jet propulsion in nautilus worked independently in ammonites.<ref>{{Cite web |title=Neutron imaging reveals never-before-seen 3D muscle structure in rare Jurassic ammonite fossil |url=https://www.isis.stfc.ac.uk/Pages/SH21_Ammonites.aspx |publisher=Science and Technology Facilities Council}}</ref><ref>{{Cite news |last=Begum |first=Tammana |date=7 December 2021 |title=Exceptionally preserved ammonite shows its inner soft tissue in 3D |url=https://www.nhm.ac.uk/discover/news/2021/december/new-soft-tissue-analyses-show-how-ammonites-lived-in-jurassic-oc.html |publisher=[[Natural History Museum, London|Natural History Museum]]}}</ref> The soft body of the creature occupied the largest segments of the shell at the end of the coil. The smaller earlier segments were walled off and the animal could maintain its buoyancy by filling them with gas. Thus, the smaller sections of the coil would have floated above the larger sections.<ref>{{cite web |title=Introduction to Ammonoidea |url=http://www.bbm.me.uk/portsdown/PH_232_Ammonites.htm |url-status=dead |archive-url=https://web.archive.org/web/20070502202153/http://www.bbm.me.uk/portsdown/PH_232_Ammonites.htm |archive-date=2 May 2007 |access-date=2007-04-26 |work=The Geology of Portsdown Hill}}</ref> The reproductive organs show possible traces of spermatophores, which would support the hypothesis that the microconchs were males.<ref>{{cite journal |last1=Klug |first1=Christian |last2=Schweigert |first2=Günter |last3=Tischlinger |first3=Helmut |last4=Pochmann |first4=Helmut |date=2021 |title=Failed prey or peculiar necrolysis? Isolated ammonite soft body from the Late Jurassic of Eichstätt (Germany) with complete digestive tract and male reproductive organs |journal=[[Swiss Journal of Palaeontology]] |volume=140 |issue=1 |page=3 |bibcode=2021SwJP..140....3K |doi=10.1186/s13358-020-00215-7 |pmc=7813712 |pmid=33505352 |doi-access=free}}</ref> They likely bore a [[radula]] and [[Cephalopod beak|beak]], and marginal siphuncle.<ref name="Landman1996">{{cite book |last1=Landman |first1=Neil H |url=https://books.google.com/books?id=hKbkB4MzUIkC&pg=PA14 |title=Ammonoid paleobiology |last2=Tanabe |first2=Kazushige |last3=Davis |first3=Richard Arnold |publisher=Springer |year=1996 |isbn=978-0-306-45222-2}}</ref> They operated by direct development with sexual reproduction, were carnivorous, and had a [[Crop (anatomy)|crop]] for food storage. They are unlikely to have dwelt in fresh or brackish water.<ref name="Landman1996" />  Many ammonites were likely [[filter feeder]]s, so adaptations associated with this lifestyle like sieves probably occurred.<ref name="Kruta2011">{{cite journal |last1=Kruta |first1=Isabelle |last2=Landman |first2=Neil |last3=Rouget |first3=Isabelle |last4=Cecca |first4=Fabrizio |last5=Tafforeau |first5=Paul |date=Jan 2011 |title=The Role of Ammonites in the Mesozoic Marine Food Web Revealed by Jaw Preservation |journal=Science |volume=331 |issue=6013 |pages=70–72 |bibcode=2011Sci...331...70K |doi=10.1126/science.1198793 |pmid=21212354 |s2cid=206530342}}</ref>[[File:Reconstruction-of-two-Late-Volgian-ammonites-from-Craspeditidae-family-Kachpurites.png|thumb|Speculative life restorations of the [[Craspeditidae|craspeditid]] ammonites ''[[Garniericeras |Garniericeras catenulatum]]'' (left) and ''[[Kachpurites|Kachpurites fulgens]]'' (right)|320x320px]][[File:Rhaeboceras reconstruction.png|thumb|Life restoratios of ''[[Rhaeboceras]],'' which had a pair of tentacles tipped with hooks, largely uniquely among ammonites]]A 2021 study reported specimens of the [[Scaphitidae|scaphitid]] ammonite genera ''[[Rhaeboceras]]'' and ''[[Hoploscaphites]]'' with mineralised hooks, which were likely present on the ends of a pair of enlarged tentacles. However, these mineralised hooks appear to be present only in scaphitids and were not typical of ammonites as a whole.<ref>{{cite journal |last1=Smith |first1=C. P. A. |last2=Landman |first2=N. H. |last3=Bardin |first3=J. |last4=Kruta |first4=I. |date=4 June 2021 |title=New evidence from exceptionally "well-preserved" specimens sheds light on the structure of the ammonite brachial crown |journal=Scientific Reports |volume=11 |issue=1 |pages=11862 |bibcode=2021NatSR..1111862S |doi=10.1038/s41598-021-89998-4 |pmc=8178333 |pmid=34088905}}</ref> The number of arms has been subject considerable speculation, with different artists either opting for a nautilus-like restoration with many arms, or a more squid-like restoration with much fewer arms, with a 1996 study suggesting that they probably had 10 arms like modern squid, cuttlefish and octopuses, but that nothing could be said for certain.<ref name=":5">{{Cite journal |last=Allmon |first=Warren D. |date=2017-01-01 |title=Life-restorations of ammonites and the challenges of taxonomic uniformitarianism |url=https://meridian.allenpress.com/esh/article/36/1/1/205099/Liferestorations-of-ammonites-and-the-challenges |journal=Earth Sciences History |language=en |volume=36 |issue=1 |pages=1–29 |doi=10.17704/1944-6178-36.1.1 |issn=0736-623X}}</ref> Paleontologist [[Mark Witton]] has stated that "The basic details of ammonite life appearance are far from clear . . . While we can be certain that a squid-like organism lived in the last chamber of their shells . . . little else can be said with certainty about their appearance. ... Despite being creatures which occur so commonly as fossils that it seems like we should know everything about them, ammonites are creatures fraught with uncertainty for artists and palaeontologists alike. Until new data comes to light, all life reconstructions of ammonites should be taken as extremely tentative, almost speculative renditions of their actual appearance."<ref name=":5" />

Many ammonoids probably lived in the open water of ancient seas, rather than at the sea bottom, because their fossils are often found in rocks laid down under conditions where no [[benthic zone|bottom-dwelling]] life is found. In general, they appear to have inhabited the upper {{Convert|250|m}} of the water column.<ref>{{cite journal |last1=Lemanis |first1=R. |date=2020 |title=The ammonite septum is not an adaptation to deep water: Re-evaluating a centuries-old idea |journal=Proceedings of the Royal Society B: Biological Sciences |volume=287 |issue=1936 |doi=10.1098/rspb.2020.1919 |pmc=7657852 |pmid=33049174}}</ref> Many of them (such as ''[[Oxynoticeras]]'') are thought to have been good swimmers, with flattened, discus-shaped, streamlined shells, although some ammonoids were less effective swimmers and were likely to have been slow-swimming bottom-dwellers. [[Synchrotron]] analysis of an [[aptychus|aptychophoran]] ammonite revealed remains of [[isopod]] and [[mollusc]] larvae in its buccal cavity, indicating at least this kind of ammonite fed on [[plankton]].<ref name="Kruta2011" /> They may have avoided predation by squirting [[Cephalopod ink|ink]], much like modern cephalopods; ink is occasionally preserved in fossil specimens.<ref>{{Cite book |author=Doguzhaeva, Larisa A. |url=https://archive.org/details/cephalopodsprese00land |title=Cephalopods Present and Past: New Insights and Fresh Perspectives |author2=Royal H. Mapes |author3=Herbert Summesberger |author4=Harry Mutvei |publisher=Springer |year=2007 |isbn=978-1-4020-6806-5 |editor=N. H. Landman |location=Dordrecht |pages=[https://archive.org/details/cephalopodsprese00land/page/n234 221]–238 |chapter=The Preservation of Body Tissues, Shell, and Mandibles in the Ceratitid Ammonoid ''Austrotrachyceras'' (Late Triassic), Austria |doi=10.1007/978-1-4020-6806-5_11 |display-editors=etal |url-access=limited}}</ref>

Many ammonite shells have been found with round holes once interpreted as a result of limpets attaching themselves to the shells. However, the triangular formation of the holes, their size and shape, and their presence on both sides of the shells, corresponding to the upper and lower jaws, is more likely evidence of the bite of a medium-sized [[mosasaur]] preying upon ammonites.

Some ammonites appear to have lived in [[cold seep]]s and even reproduced there.<ref>{{cite journal |last1=Rowe |first1=Alison J. |last2=Landman |first2=Neil H. |last3=Cochran |first3=J. Kirk |last4=Witts |first4=James D. |last5=Garb |first5=Matthew P. |date=26 March 2020 |title=Late Cretaceous Methane Seeps as Habitats for Newly Hatched Ammonites |journal=PALAIOS |volume=35 |issue=3 |pages=151–163 |bibcode=2020Palai..35..151R |doi=10.2110/palo.2019.105 |s2cid=214718487}}</ref>