Humerocyrtis asymmetrica, Dumitrică, 2024

Dumitrică, Paulian, 2024, New Middle Triassic Bell-Shaped Nassellarian Radiolaria From Alpine And Carpathian Areas, Acta Palaeontologica Romaniae 20 (1), pp. 51-75 : 72

Humerocyrtis asymmetrica n. sp.

Fig. 10c .

Diagnosis. Shell bell-shaped with subrectangular cephalis in lateral view bearing a thin apical horn tilted dorsally and curved in ventral direction and a similar but straight ventral horn. Wall of cephalis perforated by a few circular or subcircular small and irregularly scattered pores. Collar boundary not marked externally but it seems to be below the ventral horn and at the contact of the secondary lateral rays with the shell, where an evident stricture is visible. Proximal part of thorax very short and wide conical, Shoulder asymmetrical, the ventral part more pronounced than in dorsal part. Pores of shoulder and proximal part of thorax relatively wide and divided into very small areas by a secondary network of very thin bars resembling a spider’s web. This network is also present on the distal part of thorax but become less frequent in distal direction. Distal part of thorax subcylindrical with a more or less pronounced concave outline. Pores large, oval, subcircular or rounded quadrangular or triangular. Distal end with a narrowing circular and irregular row of rounded rectangular or oval pores.

Studied material. A single specimen in sample Rc4.

Holotype. Fig. 10c , coll. MGL.110298.

Dimensions. Length of shell without apical horn 101 µm, of thorax 78 µm, diameter of shoulder 78 µm, of distal end 90 µm.

Etymology. From the Latin asymmetrica – asymmetric, because its thorax is asymmetric in lateral view.

Remarks. This species differs from the other species of this genus with conical spines by the narrowing distal end of thorax and the frequency of the secondary network of thin spider’s web inside the pores.

Stratigraphic range. Very rare in the sample Rc4 from the Buchenstein Limestone from Recoaro, North Italy.

Figures

Fig. 10. a – Humerocyrtis infinita n. sp, Rc4. b, d – Humerocyrtis brevithorax n. sp.: b – R78/1b, d – poorly preserved specimen, Rc4. c – Humerocyrtis asymmetrica n. sp., Rc4. f – Humerocyrtis marmoladensis n. sp., BV 85-70. e, g – Humerocyrtis mediotriassica n. sp.: e – CR25, g – Rc4. Scale bar of 50 µm is for all figures.