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Stylohelia

Fromentel, 1861, p. 180

Type Species

Stylohelia mamillata Fromentel, 1861, p. 180; Subsequent Designation

Type Specimen: Lectotype; MNHN M03921; Verified; Dry Preserved

Type Locality: “Corallien” from Gy (Haute Saône, France)

See Alloiteau 1956 in Palaeontologia Universalis Paris N.S. n°83-1956, Beauvais 1964, p. 147, Zaman 2012 (p. 83).

Classification

Description

Massive hummocky plocoid corallum with a wide peritheca. The axis of hummocks is occupied by an axial corallite. Other corallite appear near this corallite and radiate from there but the increase is extracalicular. The calicular longitudinal profile is vertical near the inner edge of the wall and horizontal in the calicular floor. Circular corallites in relief like small volcanoes. Epitheca not observed. Peritheca exclusively made of trabecular tissue (no exotheca preserved on the lectotype). These trabecules constitute very thin costae, they are arranged perpendicularly to the distal surface of peritheca, which is concave upward. So, within a costa, trabecules converge upward. Radial elements are compact straight costosepta. First cycle regularly anastomosed to the columella, other cycle free and often attenuated. Hexameral septal apparatus with a predominant radial symmetry. Lateral faces poorly ornamented. Inner edges of major septa with periodical auriculae. Septal trabecules diverging upward in the septal plan. Styliform columella very regularly connected to major septa by connecting rods. Endotheca made of regularly spaced tabulae. Synapticule-like structures regularly connect the very thin costae in the peritheca. The wall is etallonothecal. One septum corresponds to several rows of granules.

Remarks

The genus can be interpreted contradictorily as a junior synonym of Heliocoenia (Zaman 2012) or a valid genus characterised by the wide space between corallites, the synapticules-like structures in the peritheca and possibly the dominance of trabecular tissues in the peritheca. Four nominal species are reported in Jurassic and four others in the Cretaceous (Löser 2000)

Distribution

  • Western Europe; Late Jurassic - Late Cretaceous

This page has been in preparation since 21-Aug-2009 14:09

This version was contributed by Bernard Lathuilière on 03-Apr-2014 08:52.

Page authors are: Bernard Lathuilière Shaahin Zaman. Please contact the editor if you would like to contribute to the diagnosis of this taxon.

The editor is: Bernard Lathuilière


Lectotype of Stylohelia mamillata, the type species of the genus
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Lectotype of Stylohelia mamillata, the type species of the genus
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Lectotype of Stylohelia mamillata, the type species of the genus
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Lectotype of Stylohelia mamillata, the type species of the genus
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