LITHOSTROBIDAE Petrushevskaya, 1975

Suzuki, Noritoshi, Caulet, Jean-Pierre & Dumitrica, Paulian, 2021, A new integrated morpho- and molecular systematic classification of Cenozoic radiolarians (Class Polycystinea) - suprageneric taxonomy and logical nomenclatorial acts, Geodiversitas 43 (15), pp. 405-573 : 474

Family LITHOSTROBIDAE Petrushevskaya, 1975

Lithostrobiidae [sic] Petrushevskaya, 1975: 582 (= Lithostrobidae ).

TYPE GENUS. — Lithostrobus Bütschli, 1882: 529 [type species by subsequent designation ( Campbell 1954: D141): Eucyrtidium argus Ehrenberg, 1874: 225 ].

INCLUDED GENUS. — Lithostrobus Bütschli, 1882: 529 (= Cornustrobus synonymized by Petrushevskaya 1981: 173; Cyrtostrobus synonymized by Petrushevskaya 1981: 171; Eostichomitra n. syn.).

DIAGNOSIS. — Lithostrobidae are multisegmented Nassellaria whose proximal part consists of a long apical horn, a poreless small cephalis, a latticed thorax, and a large thorax. The collar stricture between cephalis and thorax is unclear. The abdomen is distinctive from the cephalon-thoracic part by significant width differences. Subsequent segments below the abdomen are similar in height and are latticed with pores that are nearly equal in size. The exact structure of the cephalic spicular system is unknown. A-rod is upright in the cephalic cavity and is attached to the cephalic wall. A narrow tunnel typical to the A-rod extends to the stem of an apical horn. A basal ring-like structure is visible inside the bottom part of the cephalis.

STRATIGRAPHIC OCCURRENCE. —Early Turonian-late Late Miocene.

REMARKS

As Lithostrobus is the only member of the Lithostrobidae , the particular characteristics common to this family are partially understood. Lithostrobus was placed in the Stichocorythidae (originally Stichocoridae) ( Campbell 1954), Stichocapsidae ( Petrushevskaya 1981: 171-173) , and Eucyrtidiidae ( Hollis 1997: 79) . However, these three families are now synonymized to Eucyrtidiidae (see synonym of Eucyrtidiidae ). The cephalic structure of the type species lectotype of Lithostrobus ( Eucyrtidium argus ) was illustrated in Ogane et al. (2009b: pl. 48, figs 8d-8f). As described in the diagnosis, the presence of a basal ring-like structure is common in the Eucyrtidiidae . It should be noted that the segmentation patterns on the proximal part of the Lithostrobus are different from the Eucyrtidiidae .

VALIDITY OF GENERA

Lithostrobus

As the type specimen of Lithostrobus was found from the Ehrenberg collection ( Ogane et al. 2009b: pl. 48, figs 8a-c), its drawing in Ehrenberg (1876: pl. 9, fig. 1) appeared to be partly wrong as for the first three segments. Referred to this lectotype and type-illustrations, the segmentation patterns and a non-bladed robust apical horn are common among Lithostrobus , Cornustrobus and Cyrtostrobus ( Campbell 1954: D141). Cornustrobus is marked by the horn-shaped shell with similar segmentations and Cyrtostrobus is distinguished by a conical shell with a straight axis and dissimilar segmentations. The differences noted here are not so significant among them. Eostichomitra is defined by a conical multi-segmented shell, a small cephalis with an elongate apical horn, a simple initial spicule system in the cephalis, segments increasing in width and height, a smooth or slightly papillose surface and a large circular aperture on the distal end of the test. These characteristics are slightly different in the type species of Lithostrobus ; but this difference can be explained by different stratigraphic ranges because Eostichomitra was initially found from the lower Turonian and the lectotype of Lithostrobus was found from the upper Eocene from Barbados. The robust long, un-bladed apical horn, the simple cephalis, the conical multi-segmented shell similar to Eostichomitra and Lithostrobus is limitedly recognized in multi-segmented Nassellaria from the Upper Cretaceous to the upper Eocene so that these two genera should be linked by a single phylogeny at generic level. The oldest available name is Lithostrobus .