Stephanoceras

Last updated

Stephanoceras
Temporal range: Aalenian–Bajocian [1]
Stephanoceras-1.jpg
S. humphriesianum,
(lower Bajocian, Middle Jurassic), Sherborne, Dorset, UK.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass:† Ammonoidea
Order:† Ammonitida
Family:† Stephanoceratidae
Genus:† Stephanoceras
Waagen, 1869

Stephanoceras (meaning crown horn) is an extinct genus of Stephanoceratoid ammonite which lived during the Bajocian (Middle Jurassic). [1] It is the type genus of the family Stephanoceratidae.

Contents

Type species

Ammonites humphriesianum J. de C. Sowerby, 1825, [2] subsequent designation by Buchman, 1898 [3]

Selected species

[4] [5]

Description

Stephanoceras has an evolute shell, as characteristic of the family, with well-developed ribbing and tubercles. The shell is coiled so whorls barely touch in most, but some have notable overlap. Primary ribs emerge from the umbilical seam, the line marking the inner edge of the particular exposed whorl, and divide on the flanks, usually in two, occasionally in three, forming secondary ribs that cross the outer rim of the shell, known as the venter, uninterrupted. Turbercles, elevated projections, form at the ends of the primary ribs where they bifurcate or sometimes trifurcate.

Stephanoceras grew to be fairly large with a shell diameter as much as 27 cm and width as much as 6 cm across the outer whorl. Like many ammonites, Stephanoceras is dimorphic with a large, macroconch, form thought to be female and a small, microconch, form thought to be male. In most aspects the microconch is simply a smaller version of the macroconch. The primary difference lies in the aperture, which in the microconch has planar extensions on either side, lappets. That of the macroconch is generally simple, preceded by a constriction.

Distribution

Fossils of Stephanoceras are found in the Jurassic marine strata of Canada, Mexico, Saudi Arabia and Spain. [4] Some species, including S.coronatus and S.humphriesianum can also be found in rocks of the same age from England and Germany. [6]

Related Research Articles

<i>Acanthohoplites</i> Extinct genus of Cretaceous ammonites

Acanthohoplites is an extinct genus of ammonites in the family Parahoplitidae that lived in the Aptian and Early Albian stages of the Early Cretaceous.

<i>Xipheroceras</i>

Xipheroceras is a Lower Jurassic ammonite belonging to the Eoderoceratidae, and sometimes placed in the subfamily Xipheroceratinae for which it is the namesake. It has been found in the upper Sinemurian of Europe and possibly Borneo.

Aioloceras is an ammonite, order Ammonitida, from near the end of the Early Cretaceous. The shell is compressed with the outer whorl covering much of the previous. Sides are slightly convex, converge toward a narrowly ached venter. Inner whorls have sharp falcoid ribs, outer are smooth. Umbilical tubercles are lacking. Similar related forms include Neosaynella and Cleoniceras.

<i>Alsatites</i> Genus of molluscs (fossil)

Alsatites is an extinct genus of cephalopod belonging to the Ammonite subclass. They lived during the Early Jurassic, Hettangian till the Sinemurian and are generally extremely evolute, many whorled. Keel broad and blunt organisms, they also exhibit a primary ribbing which is close and persistent.

<i>Audaxlytoceras</i> Genus of molluscs (fossil)

Audaxlytoceras is an extinct genus of lytoceratid ammonites.

<i>Arietites</i> Genus of molluscs (fossil)

Arietites is a genus of massive, giant evolute, psiloceratacean ammonites in the family Arietitidae in which whorls are subquadrate and transversely ribbed and low keels in triplicate, separated by a pair of longitudinal grooves, run along the venter. Fossils are known world wide from the lower Sinemurian stage of the Lower Jurassic. Safari Ltd made an Arietites bucklandi figurine in 2014.

<i>Arcticoceras</i>

Arcticoceras is an extinct ammonoid cephalopod genus from the late Middle Jurassic belonging to the ammonite family Cardioceratidae, more commonly found to high northern latitudes.

Balticeras is an involute, discoidal Upper Jurassic (Oxfordian) ammonite found in England, Germany, and Switzerland, belonging to the Perisphinctidae. The shell is strongly embracing, tending to be oxyconic. Sides are gently curved, converging on a narrow to sharp ventral rim.

<span class="mw-page-title-main">Lytoceratina</span> Extinct suborder of ammonites

Lytoceratina is a suborder of Jurassic and Cretaceous ammonites that produced loosely coiled, evolute and gyroconic shells in which the sutural element are said to have complex moss-like endings.

Euaptetoceras is an evolute hildoceratoid ammonite from the lower Middle Jurassic, included in the family Hammatoceratidae and the subfamility Hammatoceratinae. The genus may be a junior synonym for Eudmetoceras of Buckman, 1920.

Dorsetensia is a narrowly coiled discoidal ammonite from the early Middle Jurassic, lower Bajocian, belonging to the family Sonniniidae of the superfamily Hildoceratoidea. The inner whorls are ribbed or smooth, outer whorl is smooth. The outer rim (venter) is narrow, with a keel running along the middle. The umbilicus, the opening in the middle of the shell exposing inner whorls, is of moderate size with a sharp, sometimes undercut edge.

Phaulostephanus is an extinct genus from the ammonoid family Stephanoceratidae, which is part of the ammonitid superfamily Stephanoceratoidea, that lived during the early Middle Jurassic.

<i>Normannites</i>

Normannites is a strongly ribbed evolute Middle Jurassic genus of ammonite included in the stephanoceratoid family Stephanoceratidae.

<i>Hyperlioceras</i> Genus of molluscs (fossil)

Hyperlioceras is an extinct genus of cephalopod included in the ammonitid family Graphoceratidae that lived during the Bajocian stage of the Middle Jurassic. The type species is Hyperlioceras discites

<i>Hildoceras</i> Genus of molluscs (fossil)

Hildoceras is a genus of ammonite from the Jurassic period in the family Hildoceratidae. The shells are characterized by a narrow discoidal evolute shape, keeled venter, concave ribs along the outer flanks, and a shallow spiral groove running along smooth inner flanks. Whorls slightly overlap, cross sections are compressed. The ventral keel is bordered on either side by a shallow groove. The genus was named by Alpheus Hyatt after Saint Hilda in 1876.

<i>Peltoceras</i> Genus of molluscs (fossil)

Peltoceras is an extinct ammonite genus from the aspidoceratid subfamily Peltoceratinae that lived during the later part of the Middle Jurassic.

<span class="mw-page-title-main">Oxynoticeratidae</span> Extinct family of ammonites

Oxynoticeratidae is a family of true ammonites included in the superfamily Psiloceratoidea.

<i>Kepplerites</i> Genus of molluscs (fossil)

Kepplerites is a moderately evolute ammonite from the lower Callovian included in the Stephanoceratoidea.

Megalytoceras is an extinct genus of ammonite from the middle Jurassic, belonging to the suborder Lytoceratina.

<i>Euaspidoceras</i> Genus of molluscs (fossil)

Euaspidoceras is an extinct ammonoid cephalopod genus that lived during the Middle Jurassic.

References

  1. 1 2 Sepkoski, Jack (2002). "Sepkoski's Online Genus Database" . Retrieved 2014-05-28.
  2. ↑ Sowerby, J. de C. 1823 – 1846. Mineral Choncology, vols. 5 – 7. London.
  3. ↑ Arkell, W. J. 1957. In Moore, R. C. (ed.) Treatise on Invertebrate Paleontology. Part L: Mollusca 4: Cephalopoda, Ammonoidea. Geol. Soc. Am. and Univ. Kansas Press, Lawrence.
  4. 1 2 "Paleobiology Database" . Retrieved 17 December 2021.
  5. ↑ Global Names Index
  6. ↑ Cornelius Breckinridge Boyle (1893). "A Catalogue and Bibliography of North American Mesozoic Invertebrata, Vol. 8, Ed. 102" . Retrieved 22 May 2020.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.