Apiaromitra Dumitrică, 2022

Dumitrica, Paulian, Dieni, Iginio & Massari, Francesco, 2022, Valanginian Radiolarians Of Ne Sardinia (Italy) In The Frame Of The Weissert Event, Acta Palaeontologica Romaniae 18 (2), pp. 97-159 : 141-142

Genus Apiaromitra Dumitrică n. gen.

Type species. Lithocampe apiarium Rüst, 1885 .

Diagnosis. Multisegmented conical or conico-cylindrical nassellarians with continuous longitudinal costae and without apical horn. Segments separated by planiform partitions usually marked on the surface by more or less evident circumferential ridges. Pores arranged in longitudinal and transversal rows; each intercostal longitudinal row has a single row of pores and each postabdominal segment has two rows, one above and one below planiform partitions, separated by a central imperforate circumferential band. Costae continuous along the test.

Etimology. From Latin apiarium = been hive and mitra = mitre

Remarks. The type species of this new genus was assigned in modern literature to the genus Archaeodictyomitra Pessagno, 1976 , because of its continuous and longitudinal costae with a single intercostal row of pores. However, comparing it with the type species of Archaeodictyomitra , which is the Cretaceous A. squinaboli Pessagno, 1976 , and with many other congeneric taxa, one can see that there is quite a big difference between them. Although Apiaromitra n. gen. has longitudinal costae as in Archaeodictiomitra, it has more or less expanded circumferential ridges as external expressions of the inner planiform partitions, and only two rows of pores in each segment, of which one above the planiform partition and one below it; conversely, Archaeodictyomitra has more pores on segments, not aligned in transversal rows, and the intersegmental partitions are either not marked outside or correspond to external constrictions.

By its wall structure Apiaromitra n. gen. seems to be close to the genus Wrangellium Pessagno & Whalen, 1982 , to species like Praecaneta mimetica Dumitrică, 1997 , Tethysetta pygmaea Dumitrică, 1997 and others, and to the genus Svinitzium Dumitrică, 1997 . All these Upper Jurassic or Lower Cretaceous species have in common the following characters: nodose circumferential ridges with H-linked structure corresponding to intersegmental partitions, one row of pores on each side of these partitions, and a median transversal band that can be simple and smooth ( Svinitzium ), with depressed costae, or with a row of elongate pores on longitudinal ridges, Pseudocrolanium puga (Schaaf, 1981) , Praecaneta mimetica Dumitrică, 1997 , Tethysetta pygmaea Dumitrică , in Dumitrică et al., 1997, etc.). These pores seem to derive from the middle row of the characteristic porous bands of the Parvicingulidae .

If this disposition of pores is taken into account, this genus should probably include the following species assigned until present to Archaeodictyomitra Pessagno , or to Svinitzium Dumitrică : Archaeodictyomitra apiarium (Rüst, 1885) , A. cf. apiarium (Rüst) of Ishida (1985, pl. 4, figs. 7, 8), A. apiarium of Dumitrică 1997, A. minoensis (Mizutani, 1981) , A. sp. cf. shengi Yang (1993, p. 112, pl. 21, fig. 14), A. masirahensis Dumitrică, 1997 , A. leptocostata (Wu & Li, 1982) , A. conica Dumitrică, 1997 , etc.

Range. Middle Jurassic to late Barremian-early Aptian.