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Stylina

Lamarck, 1816

Lamarck (1816) presented Stylina as an oceanic Recent form. Milne-Edwards (1848) mentioned that the fossil came in fact from Dun and the original quotation "ocean austral" by Lamarck 1816 was a mistake.

Type Species

Stylina echinulata Lamarck, 1816, p. 221,; Monotypy

Type Specimen: Holotype; ; Not Traced; Unknown

Type Locality: Oxfordian near Verdun (Meuse France)

The type species was described in Milne-Edwards and Haime, 1848, 1857. Alloiteau (1947) described several samples as a neotype of Stylina echinulata the type species of the genus (only thin sections are preserved in MNHN). Unfortunately, the neotype is not correctly established as we don’t know which of the samples is the neotype. Additionally these samples correspond to the concept of Heliocoenia Etallon. As no more topotypic material is available and in order to preserve the stability (there are hundreds of species of Stylina, Stylina is also the type-genus of a family and even of a suborder), we intend to ask the ICZN the change of type-species for the genus Stylina.

Classification

Synonyms

Description

Corallum massive with different forms, ramose, dome shaped, hummocky, irregular, lamellar and encrusting with different sizes, plocoid and, with cylindrical circular to subcircular corallites. Extracalicinal increase quasi exclusive. Peritheca well developed with vesicular and trabecular layers covered by mostly confluent costae. Costae vertically continuous or not. Radial elements are bicuneiform costosepta poorly ornamented with few thorns on lateral faces. Inner margin with koutaliform auriculae (rhopaloid, T shaped or forked in tranverse section). Radial symmetry dominant, usually hexameral, octameral or decameral with well organised size orders of septa. In some stages, 1, 2 or some septa join to the columella, (but it is less common than in Heliocoenia). Columella strong and styliform or sometimes compressed, often free. Endotheca vesicular to tabulate climbing against the columella in the columellar space. Wall parathecal, paraseptothecal or etallonothecal. Septa made of ramified trabeculae. In transverse section, primary trabecular axes are aligned in a straight or zigzag mid-septal plan.

Comparisons

Stylina is very close of Heliocoenia. Nevertheless, a careful observation allows the distinction (Zaman 2012) if several characters are taken into account. Stylina has a wide costulate peritheca in place of a less developed, granulated, in Heliocoenia. Stylina has a radial symmetry , (in place of a bilateral symmetry in Heliocoenia) (a mostly free columella and wide columellar space with endotheca climbing against the columella (in place of a columella always connected at some S1 in Hzeliocoenia). Stylina has a variable structure of its theca compared to Heliocoenia in which the etallonotheca mostly envelopes costae that are shorter than in Stylina. The auriculae of S2 in Stylina are less auriculate than in Heliocoenia_. See also Decacoenia.

Remarks

Up to 186 Jurassic nominal species were reported (many with doubts) and 60 Cretaceous nominal species are cited in Löser 2009.

This page has been in preparation since 19-Aug-2009 13:25

This version was contributed by Bernard Lathuilière on 02-Apr-2014 17:14.

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

The editor is: Bernard Lathuilière

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