Tetrarchiplagia ramosa, 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 : 16-18

Tetrarchiplagia ramosa n. sp. ( Fig. 9 A-I)

HOLOTYPE. — Photo No. 58432; stub Mue 22/21; Musée de Géologie , Lausanne, No. 74376 ( Fig. 9A ).

ETYMOLOGY. — From the Latin ramosus: branched.

MATERIAL EXAMINED. — 16 specimens from the type horizon (sample Mue 22).

DIMENSIONS ( IN µM). — Length of apical spine 140- 235 (av. 195), of dorsal spine 190-245 (av. 225), of primary lateral spines 160-245 (av. 210), of ventral spine 20-75 (av. 50), of median bar 4-6; distance of first verticil from MB on D and L 30-50 (av. 40), on A 55-80 (av. 65).

DESCRIPTION

Spicule with apical, dorsal, ventral, and both primary lateral spines originating in a very short median bar. A, D, and L stout, long, subequal, with a number of verticils oriented at about right angles to the spines, and generally decreasing in length to the distal part of the spines. Ventral spine small, thin, directed obliquely upward, distally slightly curved downwards when longer. Apical spine straight with three verticils of which the first has generally five branches, the second three, rarely more, and the third two or three. Branches of first and second verticils with one or two verticils of spinules. Dorsal and primary lateral spines equal, longer than A, and curved downward. They bear four verticils of which the first has generally three branches, the second two or three, and the third and fourth two branches. Branches of first verticil, rarely of the second, bear spinules. Except V all spines increase slowly in diametre to the last verticil, then taper distally.

REMARKS

Tetrarchiplagia ramosa n. sp. resembles somehow the Triassic species T. verticillata Dumitrica, 1982 and T. abietinoides Dumitrica, 1982 by having verticils of three or four branches, but differs from both by the number of verticils, size of branches, presence of spinules on some branches, etc. Together with the following species, this is the first Jurassic species of the family Plagiacanthidae so far described bridging the preexisting long gap between the Middle Triassic and the Paleogene. It is noteworthy, however, that they are not the only species of the family occurring in the Jurassic. Work in progress of the senior author proves that, although much sparser than in the Middle Triassic, at least three more species occur in the Lower and Middle Jurassic.

D

Figures

FIG. 9. — A-I, Tetrarchiplagia ramosa n. sp.; A, holotype, right lateral view; B-I, paratypes; B, C, left lateral and apical views of the same specimen; D, E, left lateral view and detail of apical spine of the same specimen; F, right lateral view of a specimen showing a smaller angle between D and L; G, oblique ventral view; H, dorsal view of a small specimen with strongly curved D and L; I, left lateral view, detail of the central part showing the slender ventral spine and Ll broken off; J, Tetrarchiplagia tithoniana n. sp., paratype, apical view. Abbreviations: D, dorsal spine; L, primary lateral spine; Ll, left primary lateral spine. Scale bars: A-D, F-H, J, 100 µm; E, I, 30 µm.