Pseudodiplocoenia
Alloiteau, 1958: 74
Type Species
Pseudodiplocoenia lazarivensis Alloiteau 1958: 74, pl. 8, fig. 9; pl. 13, fig. 4.; Monotypy Alloiteau, 1958: 74
Type Specimen: Holotype; MNHN ; Not Traced; Dry Preserved
Type Locality: Lazariva , Madagascar. Callovian, Middle Jurassic
The type specimen belongs to the coll. Collignon.
Diagnosis
Corallum cerioid; wall tectiform; septal arrangement radial-bilateral, anastomosis among the S2 septa and S3 septa; septal sides with oblique ranges of sharp granules, internal border regularly denticulated; columella of septal origin, rudimentary, eccentric; endotheca made of large, oblique, peripheral dissepiments and rare, horizontal pseudotabulae traversing the lumen; increase by septal division of the adult calice into 2-4 descendant calices. Microstructure: trabeculae thick, set off from the wall at obtuse angle and then declining toward the corallite axis; thick mural spines of radial structure compose the wall; stereomal peripheral deposit makes the upper dissepimental layer massively thickened. Remark: If the centers of mural spines are dissolved, a characteristic fissure appears at the middle of the wall that resembles that observed in the colonies of Amphiastrea.
Description
In addition to the type species, described and illustrated by Alloiteau 1958, other descriptions concerning the genus are known. In the Callovian of Tunisia, Beauvais 1966: 19, pl.1, fig.7 described and illustrated P. soltanensis. The northernmost site of the genus is Scottland, Navidale, where Kimmeridgian deposits occur containing Oxfordian coral clasts, among others the corals determined as Enallocoenia callomoni by Beauvais 1977: pl. 1, fig. 3a-c, presenting typical features of Pseudodiplocoenia. Portlandian species, P. oblonga (Fleming, 1827), described and illustrated in Roniewicz 1970:527,text-fig. 3-5; pl. 2, fig. 1-3; pl. 3, fig. 1-3; pl. 4, fig. 1-4, based on thin sections, provided with the most complete information on the genus.
Comparisons
In external morphological features similar to Connectastraea Koby, 1905. In the fissure observed in the middle of the wall, and in eccentric axial pit, Pseudidiplocoenia is somewhat similar to Amphiastrea from which it differs, as well as from all amphiastreid corals, in the microstructure of septa and in the way of budding. From microstructural point of view, the genus has no counterparts and for this reason it falls into the cathegory of genera of uncertain position.
Remarks
Three or four species are known.
Distribution
- North Africa; Middle Jurassic
- Western Europe; Late Jurassic
The earliest, Callovian species are known in Madagascar and North Africa. The latest occurrence, Portlndian, is known in the Western Europe.This page has been in preparation since 19-Aug-2009 17:23
This version was contributed by Ewa Roniewicz on 28-Nov-2010 17:53.
Page authors are: Ewa Roniewicz. Please contact the editor if you would like to contribute to the diagnosis of this taxon.
The editor is: Bernard Lathuilière
|