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Thamnasteriidae

Vaughan and Wells, 1943

Synonyms

Diagnosis

Radial elements are compact or subcompact biseptal sheets (presently we know only thamnasterioid candidates for this family) frequently anastomosed at their inner edge or in a contratingent manner. The inner edge of septa is thinned or rhopaloid, often attached to the columella by a trabecular lobe for larger septa. The lateral faces are covered by granules. The more common situation is an arrangement of flattened granules pointing horizontally (never upward as in typical pennulae) more or less horizontally and vertically aligned. But variations are wide and the horizontal alignment is far from strict, granules are sometimes not flattened but a sharp point. These granules do not alternate in level between neighbouring septa as it is the rule in typical pennular models. The distal edge shows regular small teeth. Trabecules are arranged in fan system and their structure is branching. Branches of trabeculae are not systematically aligned perpendicularly to the septal plan as in Montlivaltiidae. Diameter of trabeculae: 75-225 _m. Septa are organised in radial symmetry in which the hexameral arrangement cannot be easily recognised. A bilateral symmetry is often marked by anastomosing septa. This bilateral distortion is more accentuated in stretched thamnasterioid structures than in isotropic thamnasterioid ones. Synapticulae present, especially in the outer region of the corallite. Vesicular dissepiments constitute a superficial floor for the soft body that deepens around the styliform columella.

Contains

This page has been in preparation since 02-Oct-2009 17:15

This version was contributed by Ken Johnson on 02-Oct-2009 17:15.

Page authors are: 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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