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|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
Rhynchonellata - Pentamerida - Virgianidae
If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
|C. M. O. Rasmussen et al. 2010||Medium to large. Ventribiconvex, transverse in outline. The specimens are about 70–80 per cent as long as wide, with obtuse cardinal extremities. Anterior commissure strongly parasulcate. Ventral valve strongly convex with wide, deep depression (sulcus) that is developed near the beak and continues through the entire valve length to develop a tongue- like extension of the anterior commissure that occupies almost half of the anterior margin. Medianly, the sulcus is interrupted by a weak elevation. Umbonal zone positioned posterior of hinge-line with small palintrope developed. Interareas are either lacking or well developed as a low, wide and curved surface that does not extend to the cardinal extremities.
Dorsal valve moderately convex to equibiconvex having a pronounced fold, extending to approximately one-third of entire width at the anterior margin. Except for the above mentioned morphological features the material possess a few very characteristic growth rings along the entire shell margin. Except for these, the shells are smooth.
Ventral interior possesses a short, narrow spondylium with a medial spondylial groove (Fig. 7N). Ventral median septum very short and does not extend to the anterior end of the spondylium but the anterior end of the septum is curved so that the attachments to the valve floor and spondylium extend further anteriorly than the middle part of the septum (see Fig. 8).