5/17/2023 0 Comments Heteromorph ammonite![]() ![]() E-mail: new heteromorph ammonite genus, Tarrantites, is proposed for Hamites adkinsi Scott, 1928. E-mail: Research Institute, Austin, 415 Crystal Creek Drive, Austin TX78746, U.S.A. E-mail: University Museum of Natural History, Parks Road, Oxford 0X1 3PW, U.K. Box 61, Cape Town, 8000 South Africa and Department of Geological Sciences, University of Cape Town, Private Bag, Rondebosch, 7701 South Africa. INatural History Collections Department, Iziko South African Museum, P.O. Herbert Christian Klinger I William James Kennedy II Keith P. 36 (9–12): 195–200.Tarrantites, a new heteromorph ammonite genus from the Albian of Texas and Pakistan "The functional morphology of Hamites and Stomohamites and the origins of the Turrilitidae". "Functional morphology, ecology, and evolution of the Scaphitaceae Gill, 1871 (cephalopoda)". "Mid Cretaceous heteromorph ammonite shell damage". Quarterly Journal of the Geological Society of London. "The ammonite body-chamber, with special reference to the buoyancy and mode of life of the living animal". "Cladistic analysis of Albian heteromorph ammonites" (PDF). Archived from the original (Reproduced\) on. "Cladistic analysis of a problematic ammonite group: the Hamitidae (Cretaceous, Albian - Turonian) and proposals for new cladistic terms" (PDF). "Heteromorphs of the Tata Limestone Formation (Aptian - Lower Albian), Hungary" (PDF). The lineage that gave rise to the helical Turrilitidae, for example, had a shell that initially grew as a helix before straightening out the Turrilitidae thus appear to have been derived from neotenic Hamites that retained the helically-coiled juvenile morphology of Hamites into adulthood. The genus rapidly diversified during the Albian into a number of morphologically distinct lineages that seem to have given rise to at least three other families of heteromorphs, the Baculitidae, Turrilitidae, and Scaphitidae. The genus Hamites is of particular interest to palaeontologists because the species included in the genus span a wide range of morphologies including ones apparently similar to several more derived groups of heteromorph ammonites. It is widely assumed that they were planktonic, perhaps catching small prey in the manner of jellyfish, but repaired shell damage apparently caused by crabs may indicate that they spent at least some time close to the sea floor. The open shell of these ammonites would have made them poor swimmers because of drag, but beyond that fact, very little is certain about their mode of life. ![]() These have been observed on other ammonites as well, and are assumed to be signs of sexual dimorphism. ![]() No Hamites had spines or other such ornamentation on the shell, but several species appear to have developed apertural modifications when mature that is, once the ammonite had grown to its final size, the aperture became constricted and was bounded by one or two thickened ribs, known as collars. Hamites species are characterised by a shell that began with an open, sometimes helical, regular spiral that either opened into a single large hook, or else formed three parallel shafts that gave the mature shell the approximate appearance of a paper clip. This James Parkinson is best known as the first scientific description of a disease he called the Shaking Palsy, now referred to as Parkinson's disease in his honour. The type species is Hamites attenuatus from the early Albian, named by James Sowerby in his Mineral Conchology of Great Britain of 1814, although the genus itself was created by James Parkinson in his 1811 book Organic Remains of the Former World. In an attempt to identify clades within the genus, it has been divided up into a series of new genera or subgenera by different palaeontologists, including Eohamites, Hamitella, Helicohamites, Lytohamites, Planohamites, Psilohamites, and Sziveshamites. The genus is almost certainly paraphyletic but remains in wide use as a "catch all" for heteromorph ammonites of the superfamily Turrilitoidea that do not neatly fit into the more derived groupings. Hamites (" hook-like") is a genus of heteromorph ammonite that evolved late in the Aptian stage of the Early Cretaceous and lasted into the Cenomanian stage of the Late Cretaceous. ![]()
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