Youngibelus

Youngibelus Temporal range: Jurassic
Two Youngibelus, showing the male on the bottom with an epirostrum
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
(unranked):	Belemnoidea
Family:	Belemnitidae
Subfamily:	Megateuthidinae
Genus:	Youngibelus Riegraf, 1980
Type species
†Youngibelus tubularis (Young & Bird, 1822)
Other species
†Y. levis(Simpson, 1855)

Youngibelus is a genus of belemnite, an extinct group of cephalopods. ^[1]

Sexual Dimorphism

Y. tubularis and Y. levis are two species from Toarcian aged rocks in Yorkshire. It has been suggested that these two species are actually morphs of the same species. The divergence in morphology occurs in the gerontic stage of development, characterised by differences in the rostrum. In Y. levis, the rostrum thickens, whilst in Y. tubularis, an epirostrum develops. Peter Doyle proposed that the epirostrum developed as either a counterbalance for a sexual adaptation, or for display in courtship. ^[2]

See also

• Paleontology portal

• Belemnite
• List of belemnites

References

1. Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Cephalopoda entry)". Bulletins of American Paleontology. 364: 560. Retrieved 10 April 2009.
2. Doyle, Peter (1985). "Sexual dimorphism in the belemnite Youngibelus from the Lower Jurassic of Yorkshire". Retrieved 13 May 2020

• Riegraf, W. (1980). "Revision der Belemniten des Schwäbischen Jura. Teil 7". Palaeontographica Abteilung A (in German). 169 (4–6): 128–206.
• Simpson, M. (1855). The Fossils of the Yorkshire Lias Described from Nature. Whitby & London. pp. 256 pp.
• Young, G.; Bird, J. (1822). A Geological Survey of the Yorkshire Coast. Whitby: Clark. pp. 335 pp.