Silicotintinnabulum transitum, 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 : 57

Silicotintinnabulum transitum n. sp.

Fig. 2e

Diagnosis. Shell bell-shaped with a relatively large spherical and poreless cephalis with a relatively long three-bladed, axially directed and pointed apical horn. Collar boundary with a well-marked depression due to the spherical shape of the cephalis and its bigger size. Thorax short, wide conical bearing a distal row of around 12 wide elongate pores or windows and an irregular row of smaller, circular or oval pores above it, below the collar boundary. A few much smaller and irregularly arranged pores may also occur above these smaller pores. Distal end with a circular horizontal platy ring and, below it, a circular band with smaller diameter. Initial spiculat system not known, but should be similar to that of the type species.

Studied material. A single specimen in sample Rc4.

Holotype. Fig. 2e , sample Rc4, coll. MGL.110270.

Dimensions. Total length of shell 107 µm, of thorax 37 µm, diameter of cephalis 44 µm, of distal end of thorax 98 µm.

Etymology. From the Latin transitus, - a, -um – transitional, this species being considered transitional between the genus Silicotintinnabulum and the genus Pseudosaturniforma .

Remarks. Although this species is only based on the holotype, it differs essentially from the type species of the genus Silicotintinnabulum by its morphology and especially by the larger size and spherical shape of the cephalis and the appearance of the row of wide and logitudinally elongated distal pores that suggest the beginning of the transition to the genus Pseudosaturniforma . As remains of the genus Silicotintinnabulum we can mention the small pores from the base of the cephalis and the long and three-bladed apical horn.

Stratigraphic range. Very rare in the lower Ladinian of the Buchenstein Formation, Recoaro.

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.