Tertoniidae Dumitrica & Zügel 2003, n. fam.

Family TERTONIIDAE n. fam.

TYPE GENUS. — Tertonium n. gen.

RANGE. — Lower Pliensbachian-Tithonian.

DIAGNOSIS. — Dicyrtid nassellarians with small cephalis and large conical thorax. Thorax with an indefinite number of circumferential ridges separated by two or more rows of alternate pores. Initial spicule with MB, A, V, two L, two l, and D. L and l sometimes prolonged outside test wall.

REMARKS

This family is erected to define a group of Jurassic species resembling somehow the Parvicingulidae Pessagno, 1977 by the presence of circumferential ridges separated by rows of transverse pores, but differing from them in that these ridges do not correspond to internal planiform partitions which are missing. The large postcephalic segment is therefore interpreted herein as representing a single chamber – the thorax.

This group of species seems to predominantly occur in the Kimmeridgian-Tithonian. Hull (1997: 174, pl. 51, figs 1, 2, 20) illustrated two undetermined and undescribed species from this interval in California, and Kiessling (pers. comm.) found a species in the lower Tithonian of the Antarctic Peninsula. A species assignable to this family was also illustrated by Takemura (1986), Hattori (1989), and Yao (1997) as Parvicingula (?) obesa Takemura, 1986 from probably Bajocian manganese concretions (Unuma echinatus Zone) of Japan, and a specimen assignable to Toritenum n. gen. was found by us in the very rich material from the lower Pliensbachian of Turkey partly studied by De Wever (1982).