Humerocyrtis gracilis, 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 : 70-71

Humerocyrtis gracilis n. sp.

Figs. 9a, b, f

Diagnosis. Two-segmented bell-shaped nassellarian without dorsal ray in the initial spicular system. Cephalis ovoidal with partly imperforate wall and pyriform cavity with the acute end in the base of the apical horn. Apical horn more or less three-bladed to almost conical, subaxially disposed and usually slightly curved in ventral direction. Ventral spine very small outside cephalis and pyramidal. Thorax bell-shaped with a well-marked rounded shoulder and a rather deep concavity of its distal part. Pores circular or subcircular, relatively large and usually quincuncially arranged and increasing in diameter in distal direction. Intervening bars of pores relatively thin. Distal end flared with or without a narrow circular and imperforate band.

Studied material. Six specimens of which two in the sample Rc4 and four in BV 85-70.

Holotype. Fig. 9b , sample BV 85-70, coll. MGL.110294.

Paratype. Fig. 9a , sample Rc4, coll. MGL .110295.

Dimensions. Total length of shell with apical horn 80-86 µm, of thorax 40-42 µm, diameter of cephalis 17-20 µm, of shoulder 37-38 µm, of distal end 57-59 µm.

Etymology. From the Latin adjectiv gracilis – delicate.

Remark s. Morphologically, this new species is very close to the upper Longorbardian species Humerocyrtis pseudoillyrica ( Tekin & Mostler, 2005) from which it differs by having the thoracic skeleton with larger pores, the apical horn much longer and slightly curved in ventral direction, the collar structure less marked, and the distal end of thorax without a broad imperforate zone, which is a general characteristic of many species of the genus Goestlingella . Although the ventral spine of H. pseudoillyrica is not mentioned in their description and not visible on their images, it must exist because it is a characteristic element of the cephalis of the genera Goestlingella and Humerocyrtis . Its absence must be due to the dorsal position of the illustrated shells. The shape of this species is also very similar to the coeval species Goestlingella formosa Dumitrică 2017 , from which it only differs by having a three-bladed apical horn, and the distal border without a rather broad imperforate zone.

The specimen illustrated in Fig. 9f from the sample Rc4 is included in this species by its shape and disposition of pores, but difers from the holotype and all the other specimens from the sample BV 85-70 by having wider intervening bars and smaller pores due probably to its robust skeleton.

Stratigraphic range. Frequent in the lower Ladinian of the Livinallongo Formation, Marmolada Massif, sample BV 85-70, and rather rare in the Buchenstein Formation, Recoaro, sample Rc4.

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.