Hamites
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Hamites Temporal range: Early Cretaceous–Late Cretaceous |
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| reconstruction of a Hamites species | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | †Ammonoidea |
| Order: | Ammonitida |
| Suborder: | Ancyloceratina |
| Family: | Hamitidae |
| Genus: | Hamites |
| Subgenera | |
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Eohamites |
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Eohamites
Hamitella
Helicohamites
Lytohamites
Planohamites
Psilohamites
Sziveshamites
Hamites ("") 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. The genus is almost certainly paraphyletic but remains in wide use as a "catch all" for heteromorph ammonites of the superfamily Turrilitaceae that do not neatly fit into the more derived groupings. 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 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. 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.
Hamites species are characterised by a shell that began with an open, sometimes helical, regular spiral that either opened into a single large hook [1], or else formed three parallel shafts that gave the mature shell the approximate appearance of a paper clip [2]. 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. These have been observed on other ammonites as well, and are assumed to be signs of sexual dimorphism.
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