SPONGOBRACHIIDAE Haeckel, 1882

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 : 428-429

Family SPONGOBRACHIIDAE Haeckel, 1882

sensu Suzuki emend. herein

Spongobrachida Haeckel, 1882: 461 [as a tribe]; Haeckel 1887: 575 [as a subfamily]. — Schröder 1909: 50 [as a subfamily].

Spongobrachinae [sic] – Clark & Campbell 1942: 49 (= Spongobrachiinae); Clark & Campbell 1945: 26. — Campbell & Clark 1944a: 28; 1944b: 20. — Chediya 1959: 149.

Spongobrachiinae – Campbell 1954: D94. — Kozur & Mostler 1978: 140-142 ( sensu emend. ).

Spongobrachiidae – Kozur & Mostler 1978: 139-140 ( sensu emend. ).

TYPE GENUS. — Spongobrachium Haeckel, 1882: 461 [type species by subsequent designation ( Campbell 1954: D94): Spongodiscus ellipticus Haeckel, 1861b: 844 ].

INCLUDED GENERA. — Spongasteriscus Haeckel, 1862: 474 (= Spongasterisculus with the same type species; Dictyocorynium n. syn.). — Spongastromma Haeckel, 1887: 598 . — Spongobrachium Haeckel, 1882: 461 .

DIAGNOSIS. — Flat shaped Polycystinea with a circular center and a spongy disk with an irregular outline. Central part is a convex lensshaped structure (margarita) which includes a spinose microsphere and four to five densely-concentric, convex lens-shaped crusts. The center of the margarita is thick. The periphery of the margarita is more transparent than its center. A spongy structure surrounds the margarita and its outline varies from elliptical to rounded rectangle. The peripheral ends of the corners tend to be thicker than the central part; other remaining parts tend to be thin. The thicker, spongy part resembles an arm whereas the thinner part more closely resembles a patagium. These parts are intimately connected without a distinguishable boundary. Both polar sides of the margarita extend outwards or in certain cases are covered with fine appendages.

The endoplasm is bright red in color whereas the central part is discolored appearing as transparent or white. The peripheral region of the shell does not appear in red. A robust, long axoflagellum extends from the pylome and is located on the shortest line of the shell. No color is recognized along the central part to the exit of the pylome. The pylome is not walled.

STRATIGRAPHIC OCCURRENCE. — early Middle Miocene-Living.

REMARKS

Spongobrachiidae was first recognized as an independent Clade E1 when Dictyocoryne and Spongaster were placed into another independent Clade E 3 in a molecular phylogenetic study ( Sandin et al. 2021). As explained in the remarks regarding Spongodiscoidea , an appropriate family needed to be applied to Clade E. Originally, the Dictyocorynium - form of Spongasteriscus was informally known as “strange Dictyocoryne ” or was wrongly identified as “ Dictyocoryne perforatum (Popofsky) ” (see figs 8.8.3, 8.8. 4 in Suzuki & Not 2015). This illustrated specimen is actually conspecific with specimens coded as Vil449 and Mge17-17 by Sandin et al. (2021). These specimens coded as Vil449 and Mge17-17 are the Clade E 3 specimens. To maintain consistency between morphological and molecular phylogenetic classification, the genus Dictyocorynium -form of Spongasteriscus should be re-validated as a genus having an ambiguous disk with many concentric fine ambiguous hoops and spongy triangular-like external triangular parts. The importance of the disk’s lateral profile was largely ignored in the taxonomic works of classic Spongodiscoidea (see remarks in Trematodiscoidea ); however, it was an important character to define and differentiate this family. A detailed skeletal image in scanning electron microscopy (SEM) has been captured for the Dictyocorynium -form of Spongasteriscus ( Matsuoka 2009: fig. 3.30). Fine protoplasmic structure is illustrated in Spongasteriscus ( Hollande & Enjumet 1960: pl. 23, fig. 3), but protoplasmic structures particular to the Spongobrachiidae , or differences from Euchitoniidae , are unknown due to there being no section image of the protoplasm of Euchitoniidae .

Validity of genera

Spongasteriscus

This genus has been separated from the Euchitoniidae and Spongodiscidae in consideration of the molecular phylogeny observations published by Sandin et al. (2021). Until the molecular phylogenetic differences were pointed out, they have been identified as other genera of the Euchitoniidae , Spongodiscidae and other spongy discoidal groups. For instance, probable Spongasteriscus specimens might have been mixed with true Spongaster representatives in a previous study ( Riedel & Sanfilippo 1978a: pl. 2). In consideration of the wide variation in the development of the arms and their number, the four-armed Spongasteriscus is the oldest synonym of the three-armed Dictyocorynium .