Thamnasteria
Lesauvage, 1823, p. 243
Type Species
Astrea dendroidea Lamouroux, p. 85, pl. 78, fig. 6.; Monotypy
Type Specimen: Neotype; ?; Not Traced; Unknown
Type Locality: Initially described from the « Terrain à polypiers des environs de Caen » the type-locality can be situated in the Oxfordian (upper Jurassic, Coral Rag) of Normandy.
Lesauvage made an objective synonym of Astrea dendroidea: Thamnasteria lamourouxii. Alloiteau (1957, p. 201) designated a neotype figured pl. 1 fig. 5. This neotype is presently lost.
Classification
Synonyms
Description
Lamellar, dome-shaped, hummocky or ramose thamnasterioid corallum. Variation from isotropic to stretched thamnasterioid. Epitheca present. Intracalicular increase. Radial elements are compact biseptal sheets, anastomosed, often sinuous and subequal. Distal edge with regular small teeth, lateral faces covered of small horizontally flattened dentate expansions never turned upward and not alternating from a septum to the neighboring one. Acute granules also present. Granules with a tendancy to be aligned in two perpendicular directions on the lateral faces. Inner edge attenuated or rhopaloid often attached to the columella with a trabecular lobe for the longer septa. Microstructure made of simple to compound trabeculae. In transverse section of thick septa, the trabecular axes are not strictly aligned. Hexameral symmetry generally not deciphered, bilateral symmetry generally marked by the anastomosing pattern. Endotheca made of dissepiments close of the distal edge, a little deeper around the styliform columella. Synapticulae or adtrabecular bars present, especially in the peripheral region of corallites, wall absent.
Comparisons
Periseris and Astraeomorpha have a really pennular structure with outer rims of menianae oriented upward Kobyastraea has not these flattened ornamentions of septa. Stereocoenia is very close but perhaps has septa thickened by irregular multiple series of large trabeculae Mesomorpha has enclosed petaloid septa Pamiroseris has a papillar columella
Remarks
Aragonitic very well preserved samples are described in Roniewicz 1982. a topotypic material is described in Lathuilière 1990. Variability of a Bajocian species is studied in Lathuilière 2000. An ecological review of the genus is given in Bertling (1993, 1995). 37 nominal species were counted for the Triassic, 167 in the Jurassic and 90 in the Cretaceous (Löser 2000). A high number of these nominal species have already been reclassified but a lot remain to be revised to get a significant distribution. Thamnasteria in the present conception is known at least from the Bajocian.
This page has been in preparation since 20-Aug-2009 09:19
This version was contributed by Bernard Lathuilière on 17-Mar-2013 10:23.
Page authors are: Ewa Roniewicz Bernard Lathuilière. 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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