Scaphitidae

Abstract: The Hamitidae are a family of mid–Cretaceous heteromorph ammonites including lineages leading to four other families. Problems are outlined in trying to describe the phylogeny of completely extinct groups such as these heteromorph ammonites using the existing cladistic terminology, which is largely concerned with extant taxa and their ancestors. To solve these problems, two new terms are proposed: †crown groups and †stem groups, which are equivalent to crown and stem groups in terms of the evolutionary history of a clade, but are not defined on the basis of extant taxa. Instead they are defined by the topology of the phylogenetic tree, the †crown group being a clade defined by synapomorphies but which gave rise to no descendants. A †stem group is a branch of a phylogenetic tree which comprises the immediate sister groups of a given †crown group but is not itself a clade. Examples of these terms are described here with reference to the phylogeny of the Hamitidae and their descendants. The Hamitidae are paraphyletic and form †stem groups to a number of †crown groups, namely the Anisoceratidae, Baculitidae, Scaphitidae, and Turrilitidae. The definitions of the genera and subgenera are refined with respect to the type species and the clades within which they occur, and four new genera are described: Eohamites, Helicohamites, Sziveshamites, and Planohamites.

Abstract: A computer-based parsimony analysis of Albian heteromorph ammonites from the Tethyan and European faunal provinces is demonstrated. The results indicate that whilst Anisoceratidae, Baculitidae, Scaphitidae and Turrilitidae are monophyletic, Hamitidae is not. Previous studies of ammonite phylogenetics have used the coiling mode, ornamentation of the shell and the suture line as sources of characters. Comparison of the consistency and retention indices of these character suites indicates that whereas ornamentation is relatively consistent within clades, suture line morphology is highly homoplastic. The earliest known Sciponoceras, S. skipperae sp. nov., is described.

Abstract: The paper deals with the Upper Albian ammonites occurring in the transgressive deposits of south-western Crimea in the Soviet Union. On the basis of faunistic and lithological criteria, the stratigraphic subdivision of these deposits is presented, and its scheme compared with those of the platform and geosynclinals areas of Europe and adjacent regions of Asia. In the paleontological part, described are 30 ammonite genera or species, one of which is new: Prohysteroceras ( Goodhallites ) tauricense sp. n. The investigated ammonites represent the families Hamitidae, Scaphitidae, Desmoceratidae, Hoplitidae, Brencoceratidae and Lyelliceratidae, and they bear close resemblances to the assemblages known from western and central Europe.

Abstract: (1953). XLV.—Notes on cretaceous Ammonites. I. Scaphitidae. Annals and Magazine of Natural History: Vol. 6, No. 66, pp. 473-476.