Harpoceras

Harpoceras; Temporal range: Early Toarcian to Middle Toarcian PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Fossil shell of Harpoceras subplanatum from Isère (France), on display at Galerie de paléontologie et d'anatomie comparée in Paris
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Ammonoidea
Order:	†Ammonitida
Family:	†Hildoceratidae
Subfamily:	†Harpoceratinae
Genus:	†Harpoceras; Waagen 1869
Type species
	Ammonites falcifer; Sowerby, 1820
Species
	Harpoceras falciferum Sowerby, 1820; Harpoceras kisslingi Hug, 1898; Harpoceras lassum Buckman, 1927; Harpoceras mediterraneum Pinna, 1968; Harpoceras pseudoserpentinum Gabilly, 1973; Harpoceras rulleaui Bécaud, 2006; Harpoceras serpentinum Schlotheim, 1813; Harpoceras strangewaysi Sowerby, 1820; Harpoceras subexaratum Bonarelli, 1899; Harpoceras subplanatum Oppel, 1856; Harpoceras loeve Gabilly, 1975;
Synonyms
	Falcifericeras Breistroffer, 1949; Gallitellia Venturi and Ferri, 2001; Glyptarpites Buckman, 1927; Harpoceratoides Buckman, 1909; Kolymoceras Dagis, 1970; Lioceras Bayle, 1878; Maconiceras Buckman, 1926; Phaularpites Buckman, 1928; Tardarpoceras Buckman, 1927;

Harpoceras is an extinct genus of ammonite belonging to the family Hildoceratidae. These cephalopods existed in the Jurassic period, during the Toarcian age from the Falciferum zone to the Commune subzone of the Bifrons zone.^[3] They were fast-moving nektonic carnivores.^[2]

Description

Shells of Harpoceras species show strong dimorphism in their size. While microconchs reach 24–51 mm in diameter, macroconchs shells width is 115–430 mm. They are moderately evolute to involute and compressed. Whorl sides are flat and there is strong keel. Ribs are falcoid or falcate and thus biconcave, strong and projected. Sometimes, ribs can be broad and flat topped on outer part of whorl and in some species they can be striate on inner part of whorl. Some species have midlateral groove, or series of undulating depressions on inner half of whorl.^[1]^[2]

Distribution

Fossils of species within this genus have been found in the Lower Jurassic rocks of Europe, Northern Africa, Russia, Japan, Borneo, New Zealand, Indonesia, North and South America (Argentina; El Cholo and Los Molles Formations).^[1] Two species, Harpoceras serpentinum and Harpoceras falciferum, are index fossils used for stratigraphic correlation and dating of rocks of the Toarcian stage of the Lower Jurassic.^[4]

References

^ ^a ^b ^c M. K. Howarth 2013. Treatise on Invertebrate Paleontology, Part L, Revised, Volume 3B, Chapter 4: Psiloceratoidea, Eoderoceratoidea, Hildoceratoidea.
^ ^a ^b ^c Paleobiology Database - Harpoceras. 2017-10-16.
^ Sepkoski, Jack Sepkoski's Online Genus Database – Cephalopoda
^ Ogg, J.G.; Hinnov, L.A.; Huang, C. (2012). "Jurrasic". In Gradstein, F.M.; Ogg, J.G.; Schmitz, M.D.; Ogg, G.M. (eds.). The Geologic Timescale 2012. Elsevier. p. 766. ISBN 978-0-44-459390-0.

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[Howarth2013-1] M. K. Howarth 2013. Treatise on Invertebrate Paleontology, Part L, Revised, Volume 3B, Chapter 4: Psiloceratoidea, Eoderoceratoidea, Hildoceratoidea.

[paleodb-2] Paleobiology Database - Harpoceras. 2017-10-16.

[fb-3] Sepkoski, Jack Sepkoski's Online Genus Database – Cephalopoda

[Gradstein_et-al_2012-4] Ogg, J.G.; Hinnov, L.A.; Huang, C. (2012). "Jurrasic". In Gradstein, F.M.; Ogg, J.G.; Schmitz, M.D.; Ogg, G.M. (eds.). The Geologic Timescale 2012. Elsevier. p. 766. ISBN 978-0-44-459390-0.

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