Mrabella Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell and Lara 2016

 

Description. Test elongated-pyriform, laterally compressed, with the lateral sides gradually tapering toward the pseudostome. Lateral margins distinctly compressed giving the impression of a thick and wide hollow keel. Because of this, the test is elongated elliptical with the pointed end in the profile. Test colourless, composed of quadrangular shell plates similar to those in Quadrulella species.
Type species. Mrabella subcarinata comb. nov. (Gauthier-Lievre, 1957) Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell and Lara 2016.
Included taxa: Q. subcarinata Gauthier-Lievre, 1957 and the similar taxa Q. plicata Hoogenraad et de Groot 1940.

 

 

Mrabella subcarinata Gauthier-Lievre

M. subcarinata - From Gauthier-Lièvre, 1957

 

 

Mrabella subcarinata (Gautier-Lièvre 1957) Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell and Lara 2016

Description: Test elongated-pyriform, laterally compressed, with the lateral sides gradually tapering toward the pseudostome. Lateral margins distinctly compressed giving the impression of a thick and wide hollow keel. Because of this, the test is elongated elliptical with the pointed end in the profile. Test colourless, composed of quadrangular shell plates similar to those in Quadrulella species. Aperture curved and bordered by a think organic lip.

 

Dimensions: L: 201–218 µm, B: 105–127 µm. Aperture 35– 37.5 µm wide (n=3).

 

Differential diagnosis. M. subcarinata is similar to Gibbocarina galeata in general shape of the test and in the presence of a wide, hollow, tuberous keel. Gibbocarina galeata is generally larger, but sizes overlap: L: 180–283 µm, B: 94–190 µm in G. galeata versus L = 201–218 µm, B = 105–127 µm in M. subcarinata. As far as known, G. galeata never presents a shell composed entirely of rectangular plates, as is the case in M. subcarinata. M. subcarinata may be confused with M. plicata, which has a similar shape and keel, but it is smaller (L: 111–135 µm, B: 49–62 µm).