Humerocyrtis infinita, 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 infinita n. sp.

Fig. 10a

Diagnosis. Shell bell-shaped dicyrtid consisting of cephalis and proximal part of thorax represented by the shoulder. Cephalis smooth with some rare sparse rounded and irregularly distributed pores especially on its lower part. Apical and ventral horns conical and thin and of similar length. Apical horn dorsally tilted and slightly curved in ventral direction. Ventral horn straight and obliquely directed. Collar stricture not marked, but it could be approximately established at the level of MB where the pore start becoming larger. Thorax represented by the shoulder of thorax which is very much expanded in lateral direction and has a rounded outline. Its wall has large subcircular or rounded triangular or quadrangular pores of irregular arrangement and sizes. Distal part of shoulder is short, constricted and its end is marked by a thin linear border.

Studied material. A single specimen in Rc4.

Holotype. Fig. 10a , coll. MGL110297 .

Dimensions. Length of shell without horns 88 µm, of thorax 55 µm, diameter of shoulder 96 µm, of its distal opening 74 µm.

Etymology. From the Latin infinitus – unfinished, because this species has no concave post shoulder part with flare-shaped end.

Remarks. Humerocyrtis infinita n. sp. resembles structurally H. brevithorax n. sp. by having the post-shoulder shell very short consisting of the narowing portion, but differs from it by missing the circumferential ring of the shoulder and by having a well-marked distal opening showing no possibility of developing a flare distal end.

Stratigraphic range. Very rare in the lower Ladinian sample Rc4 from the Buchenstein Formation 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.