Dactylioceratidae
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The family Dactylioceratidae comprises Early Jurassic
ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...
genera with ribbed and commonly tuberculate shells that resembled later Middle Jurassic stephanoceratids and Upper Jurassic perisphinctids. Shells may be either evolute or involute.


Description

Ammonites with evolute, serpenticone to cadicone shells with ribs, sometimes with tubercules. Members of this family had no keels. while homeomorphic with stephanoceratids and perisphinctids, they had unique shell structure with double shells and flat-topped ribs on the inner shell. Based on suture differences, they are divided into 2 subfamilies. Reynesocoeloceratinae possess two major secondary lobes in dorsal side of external saddle. This saddle is not divided this way in Dactylioceratinae, while lateral lobe is deeply trifid.


Evolution

It has been suggested, that this family is polyphyletic, but this is now considered to be false. Reynesocoeloceratinae evolved in lower
Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 192.9 ±0.3 Ma and 184.2 ±0.3 Ma (million years ago). The Plie ...
from '' Metaderoceras'' and died out in upper Pliensbachian. ''Reynesoceras'' oldest member of Dactylioceratinae evolved in upper Pliensbachian from ''Cetonoceras'', or ''Prodactylioceras''. This subfamily died out in middle
Toarcian The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...
, during Variabilis zone.M. K. Howarth 2013. Treatise on Invertebrate Paleontology, Part L, Revised, Volume 3B, Chapter 4: Psiloceratoidea, Eoderoceratoidea, Hildoceratoidea.


Taxonomy

*Dactylioceratidae Hyatt, 1867 ** Reynesocoeloceratinae Dommergues, 1986 ***'' Reynesocoeloceras'' Géczy, 1976 ***'' Bettoniceras'' Wiedenmayer, 1977 ***'' Prodactylioceras'' Spath, 1923 ***'' Cetonoceras'' Wiedenmayer, 1977 ** Dactylioceratinae Hyatt, 1867 ***'' Reynesoceras'' Spath, 1936 ***'' Dactylioceras'' Hyatt, 1867 ****''D. (Dactylioceras)'' Hyatt, 1867 ****''D. (Orthodactylites)'' Buckman, 1926 ****''D. (Iranodactylites)'' Repin, 2000 ****''D. (Eodactylites)'' Schmidt-Effing, 1972 ***'' Nodicoeloceras'' Buckman, 1926 ***'' Peronoceras'' Hyatt, 1867 ***'' Zugodactylites'' Buckman, 1926 ***'' Porpoceras'' Buckman, 1911 ***'' Septimaniceras'' Fauré, 2002 ***'' Catacoeloceras'' Buckman, 1923 ***'' Collina'' Bonarelli, 1893 ***'' Tokurites'' Repin, 2016


References

;Notes ;Bibliography * W. Arkell ''et al.'', 1957. Mesozoic Ammonoidea, ''
Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...
, Part L.'' Geological Society of America and University of Kansas, Press. Ammonitida families Eoderoceratoidea Early Jurassic ammonites Early Jurassic first appearances Early Jurassic extinctions {{ammonitina-stub