Tertonium curvicornum, 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

Tertonium curvicornum n. sp. ( Fig. 25 A-C, I, J)

? Nassellaria gen. et sp. indet. 4 – Hull 1997: 174, pl. 51, fig. 2.

HOLOTYPE. — Photo No. 58406; stub Mue 22/20; Musée de Géologie , Lausanne, No. 74403 ( Fig. 25A ). ETYMOLOGY. — From the Latin curvus: curved; and cornum: horn.

OCCURRENCE. — Upper lower Kimmeridgian? (Subzone 2 alpha 2, Hull 1997) to early Tithonian, Hybonotum Zone .

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

DIMENSIONS ( IN µM). — Total length 505-655 (av. 575), length of apical horn 140-200 (av. 165), of thorax 320-455 (av. 385), of upper thorax 105-175 (av. 130), of lower thorax 205-300 (av. 255), total width 370-515 (av. 400), width of upper thorax without spines 235-275 (av. 255), of lower thorax 240-315 (av. 275).

DESCRIPTION

Test large, composed of a conical proximal part including cephalis and upper thorax, and a cylindrical distal part. Cephalis and upper thorax with a double-layered wall. Apical horn thick, threebladed, with two blades on the dorsal part and one on the ventral part. Blades with broadened rim, separated by deep grooves. Horn with the proximal part straight, vertical, and the distal part pointed, strongly curved in dorsal direction at about its middle part. At this point the ventral blade gives rise to a ventrally directed thorn. Cephalis conical externally, perforated by small pores irregularly distributed within the meshes of the outer layer. Collar boundary marked by the onset of spinal prolongations on the outer surface (V, D, the two L). Upper thorax widely conical, rounded in cross section. Spinal prolongations are first integrated in the thoracic wall, with only the outer blade appearing at the surface. This blade is still connected to the neighbouring pore frames of the spongy outer layer of the wall. Lateral blades of the spinal prolongations are covered by the spongy layer, and appear late, usually at the level of a strong circumferential ridge. Beyond this ridge the spines are free, threebladed, straight, and directed obliquely downward at an angle of about 45°. Lower part of thorax generally cylindrical with wavy outline due to some circumferential ridges and/or constrictions. Outer layer of the wall still present on the upper part of this segment. Pores small, alternately disposed in circumferential rows, two, three or more in each interval between ridges. Distal part of thorax always corroded in our specimens.

REMARKS

Tertonium curvicornum n. gen., n. sp. differs from T. rectum n. gen., n. sp. by having a curved apical horn, shorter and straight spines diverging from the upper part of thorax, and by a cylindrical, spineless lower thorax. The specimen illustrated by Hull (1997) from the upper lower Kimmeridgian of the Taman Formation, eastcentral Mexico, might be related to this species, but it differs from the latter by seemingly having only two or three spines on thorax, and in having a segmented thorax with deep segmental constrictions. Since the apical horn of the Mexican specimen is broken, it is impossible to know whether it was originally curved or straight.

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.