Humerocyrtis avirostrum, 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 : 70

Humerocyrtis avirostrum n. sp.

Fig. 9c

Diagnosis. Shell large bell-shaped, with well-developed and pointed three-bladed apical and ventral spines. Cephalis short and globular with a few very small pores. Collar boundary marked by a depression on the dorsal side and under the ventral spine that correspond to the position of MB. Proximal part of thorax tronconical and short with elliptical pores of various sizes and irregular arrangement. Shoulder rounded or slightly acute but without a circumferential ring. It corresponds to the boundary between the first two circumferential rows of pores. Distal part of thorax with concave outline and with the minimum diameter under the shoulder. Distal part of thorax conical with 4 or 5 circumferential rows of larger pores of oval, elliptical or rounded quadrangular shape. Distal end of thorax with a circular band a little broader and thicker than the bars between the circumferential rows of thoracic pores. Under this band there is a narrowing row of rounded quadrangular pores with thin intraporal bars.

Studied material. One specimen in sample Rc4.

Holotype. One specimen, coll. MGL.110293.

Dimensions. Length of shell with apical horn and post thoracic additional shell 270 µm, without post thoracic shell 255 µm, diameter of cephalis 55 µm, of shoulder 83 µm, of distal part of thorax 108 µm.

Etymology. From the Latin avis – bird and rostrum – beak, due to the resemblance between the ventral spine and the beak of birds.

Remarks. Humerocyrtis avirostrum n. sp. resembles generally H. lahmi n. sp. in size and the type of distal thoracic pores from which it differs by not having the shoulder with a circumferential ring and by having the distal part of thorax well constricted and the distal thoracic border with an additional post-thoracic narrowing row of pores with thin interporal bars.

Stratigraphic range. A single specimen in the lower Ladinian from the Buchenstein Formation.

Figures

Fig. 9. a, b, f. – Humerocyrtis gracilis n. sp.: a. – paratype, Rc4; b. – holotype, BV 85-70, f.– Rc4. c. – Humerocyrtis avirostrum n. sp., Rc4; d, d1, e. – Humerocyrtis brevithorax n. sp., CRH: d, d1. – same specimen in lateral and basal view, respectively, showing the initial spicule without D ray, e. – holotype. Scale bar of 50 µm is for all figures, except fig. 7c for which the scale bar is of 75 µm.