Amphiplecta Haeckel 1881

Trubovitz, Sarah, Renaudie, Johan, Lazarus, David & Noble, Paula, 2022, Late Neogene Lophophaenidae (Nassellaria, Radiolaria) from the eastern equatorial Pacific, Zootaxa 5160 (1), pp. 1-158 : 13

Genus Amphiplecta Haeckel 1881 , emend. Petrushevskaya 1971 sensu Funakawa 1994

Type species: Amphiplecta acrostoma Haeckel, 1887

Description. A two-segmented lophophaenid with a conical cephalis that reaches maximum width at the top, can be left open, and often has a corona of spines. The thorax is widely flared and typically has an irregular termination. The internal skeletal structure of this genus includes an apical spine that runs along the side of the cephalis, a relatively short median bar, and dorsal, left lateral, and right lateral spines that extend from the base of the cephalis to run along the outside of the thorax as ribs ( Figure 5 ), similar to Lampromitra . The arches at the base of the apical spine, AD and AL are well defined and prominent in skeletal outline.

Remarks. This genus was briefly mentioned in Haeckel’s (1881) prodromus, but a more detailed description and illustrations were first published in Haeckel (1887). Amphiplecta amphistoma Haeckel, 1887 was designated as the type species by Campbell (1954). To clarify the genus concept, Petrushevskaya (1971) emended and clarified the genus description and redesignated the type species as Amphiplecta acrostoma Haeckel 1887 because A. amphistoma had not been illustrated. Petrushevskaya (1981) noted that Miocene species can have smaller,circular pores resembling those of the genus Lophophaena . Petrushevskaya (1971) also illustrated one specimen ( Amphiplecta sp. , Middle Miocene; pl. 54 fig. 1) with a closed cephalic apex. This characteristic would contradict the definition of the genus, as originally described by Haeckel (1881, 1887) and by Petrushevskaya (1971) herself. Funakawa (1994) uses a slightly looser definition of the genus, that does not require the cephalis to be open at the top. Two new Amphiplecta species without open tops have been described since Petrushevskaya’s (1971) emendation, Amphiplecta tripleura Funakawa, 1995b and Amphiplecta ? satoshii Renaudie and Lazarus, 2015. Funakawa’s major contribution was the recognition of internal skeletal elements in SEM photography. We adopt Funakawa’s (1994) revision as it is most congruent with common usage.

Here we observed the following species belonging to Amphiplecta : Amphiplecta acrostoma Haeckel, 1887 , Amphiplecta cylindrocephala? Dumitrica, 1973 , Amphiplecta kikimorae n. sp., and Amphiplecta tripleura? Funakawa, 1995b . Amphiplecta amphistoma Haeckel, 1887 is considered a nomen dubium because it has never been illustrated and the verbal description alone is not sufficient to identify the species. Amphiplecta callistoma Haeckel, 1887 is not included because it has a flat rather than conical cephalis, and was transferred to Lampromitra by Petrushevskaya (1971).

Range. Middle Miocene—Recent.

Figures

FIGURE 5. Internal skeletal structure of Amphiplecta acrostoma Haeckel, 1887.