Silicotintinnabulum formosum, 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 : 55-56

Silicotintinnabulum formosum n. sp.

Figs. 2 a-d

Diagnosis. Shell dicyrtid, campanulate. Cephalis globular, imperforate or bearing sparse and very small circular or oval pores, especially on its distal part. Apical horn relatively long, cylindrical and hollow on its proximal third and three-bladed and pointed on its distal part. Blades thin or thick separated by wide grooves, and bearing a few short teeth or, very rarely, numerous and very short spinules on their distal end. Initial spicule with apical ray vertically positioned and prolonged into the apical horn, and ventral ray not extended outside into a spine or horn. Thorax conical with about two or three irregularly disposed ranges of large pores that increase in size very fast distally so that on the distal part only about five large pores can be seen on half the perimeter. Pores circular, oval or rounded polygonal and commonly intricately arranged (fig. 1a-d). Distal end well-marked by a thin circumferential ring disposed in horizontal plane and another circumferential ring with the blade in vertical plane, both originated in the same region of the distal end of shell. Collar boundary marked by a slight constriction and considered as being situated at the appearance of larger pores, a little below the level of the median bar of the initial spicule.

Studied material. Nine specimens in the samples Rc1, Rc4, and SMF4 from the Buchenstein Formation , and two in the sample FÖ 87, from Hungary .

Holotype. Figure 2d , sample Rc1, coll. MGL.110268.

Paratype. Figure 2c , sample FÖ 87, coll. MGL .110269.

Dimensions. Total length of shell 100-104 µm, of cephalis with apical horn 65-70 µm, of apical horn 40 µm, of thorax 30-40 µm; diameter of cephalis 35-40 µm, of distal part of thorax 83-95 µm.

Variability. As the drawings show, the variability of this species is especially visible in the shape and arrangement of pores and less in the size of specimens.

Etymology. From the Latin formosus, - a, - um – beautiful.

Remarks. The apical part of shell, including cephalis and apical horn, has a rather constant morphology, except a single specimen ( Fig. 2c ) of Illyrian age from the sample FÖ 87 that bears a bunch of short spinules on its distal end. Interestingly, that a rather similar type of short distal spinules is present on the apical horn of the species Gorispela mimetica n. sp. and Gorispela hungarica n. sp. (see below), two species occurring in the same sample FÖ 87 from the Felsőörs section. Pores of thorax are very variable in shape and arrangement but are always very large.

Stratigraphic range. Upper Anisian (Illyrian) from Hungary and lower Ladinian (Fassanian) of the Buchenstein Formation from Recoaro area, Vicentinian Alps, Italy.

Figures

Fig. 2. a-d. – Silicotintinnabulum formosum n. sp.: a, a1, b. – sample Rc4; a1. basal view of fig. a. showing the initial spicule without D ray; c. – paratype, FÖ 87; d. – holotype, Rc1. 2e. – Silicotintinnabulum transitum n. sp., holotype, Rc4; f, g. – Colpotrelus campanuliformis n. sp., Rc4. Scale bar of 50 µm is for all figures.