Tertonium rectum, Dumitrica & Zügel, 2003

Dumitrica, Paulian & Zügel, Peter, 2003, Lower Tithonian mono- and dicyrtid Nassellaria (Radiolaria) from the Solnhofen area (southern Germany), Geodiversitas 25 (1), pp. 5-72 : 49-50

Tertonium rectum n. sp. ( Fig. 25 D-H)

Nassellaria gen. et sp. indet. 1 – Hull 1997: 174, pl. 51, figs 1, 20.

HOLOTYPE. — Photo No. 45630, 45633; stub Mue 22/16; Musée de Géologie , Lausanne, No. 74404 ( Fig. 25D, E ).

ETYMOLOGY. — From the Latin rectus: straight.

OCCURRENCE. — Early Tithonian, Hybonotum Zone to upper Tithonian, subzone 4 beta.

MATERIAL EXAMINED. — Nine illustrated specimens and many others not illustrated from the type horizon (sample Mue 22).

DIMENSIONS ( IN µM). — Total length 645-710, total width 565-780 (av. 655), length of upper thorax without spines 110-215 (av. 170), of lower thorax 145-215 (av. 185), maximum width of upper thorax 235-345 (av. 285), of lower thorax 240-290 (av. 270), length of apical horn 190-325 (av. 240), of spines of upper thorax 170-345 (av. 270), of spines of lower thorax 210.

DESCRIPTION

Test composed of a small cephalis and a twopartite thorax. Cephalis short-conical externally, porous, partly covered by the broad base of a long three-bladed apical horn. Pores of cephalis small, open within irregular areas formed by a network of transversal and longitudinal ridges. The latter ridges coalesce apically to form the three blades of the apical horn. Boundary between cephalis and thorax marked at the inner side by weak arches, and on the outer surface by the onset of the four spines – D, V, and two L at the top of the thorax. Upper part of thorax rapidly increasing in width, rectangular in cross section, forming a well marked pyramid whose edges are represented by the downward prolongations of the ventral, dorsal, and primary lateral spines. At the base of this upper part these prolongations emerge from the test wall forming four long three-bladed spines. Spines recurved and distally pointed. Lower part of thorax slowly increasing in diametre, rectangular in cross section with edges formed by four secondary spines arising from the thoracic wall and extended distally into three-bladed spines. Compared to the primary spines, these spines are straight and less divergent. Wall of thorax thin, supported by continuous circumferential ridges. Ridges follow each other at irregular intervals and correspond internally to grooves. Wall between ridges convex externally with variable number (two to six) of transverse rows of alternate pores. Especially on the upper part of thorax ridges bear small thorns, probably remains of an external spongy layer.

REMARKS

Tertonium rectum n. gen., n. sp. differs from T. curvicornum n. gen., n. sp. especially by having four spines on the lower thorax. Although its distal part is missing, the specimen illustrated by Hull (1997) from the upper Tithonian of the California Coast Ranges is rather similar to the specimens from the sample Mue 22. The preserved part of that specimen only differs from our specimens in having straight primary spines extended from the upper thorax.

Figures

FIG. 25. — A-C, I, J, Tertonium curvicornum n. gen., n. sp.; A, holotype, right latero-dorsal view; B, C, I, J, paratypes; B, C, right lateral views; I, J, basal view showing details of initial spicule; D-H, Tertonium rectum n. gen., n. sp.; D, E, holotype, dorsal and basal views; F-H, paratypes; F, G, right lateral and apical views; H, detail of surface of proximal part of thorax. Scale bars: A-G, 100 µm; H, I, 30 µm; J, 10 µm.