Lophophaena laticeps ( Jørgensen, 1905 ) Kurihara and Matsuoka, 2010

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 : 61

Lophophaena laticeps ( Jørgensen, 1905) Kurihara and Matsuoka, 2010

Plate 23, Figs. 6A – 7B .

Lithomelissa laticeps n. sp., Jørgensen, 1905, pl. 16, fig. 84.

Lithomelissa laticeps Jørgensen, Schröder, 1914 , text-figs. 58–59.

Lithomelissa laticeps Jørgensen, Benson, 1966 , pl. 24, figs. 14–15.

non Botryopera laticeps Jørgensen, Petrushevskaya, 1975 , pl. 20, fig. 3.

Lithomelissa laticeps Jørgensen, Benson, 1983 , pl. 9, fig. 3.

Lophophaena laticeps Jørgensen, Kurihara and Matsuoka, 2010 , fig. 3.7.

Lithomelissa laticeps Jørgensen, Trubovitz et al., 2020 , supplementary data 7.

Remarks. This species was originally described under the genus Lithomelissa , but it does not have an apical spine passing freely through the cephalis and thus does not satisfy modern usage of this genus definition. Kurihara and Matsuoka (2010) listed this species in Lophophaena but did not discuss the genus transfer. We agree that this species best fits the definition of Lophophaena because the cephalis is relatively high with maximum width near the top, and the apical spine runs along the shell wall.

This species could be closely related to some morphotypes of Stichopilium bicorne , the notoriously cryptic group that is characterized by two strong spines running along opposite sides of the cephalis and has a wide variety of thorax shapes and sizes. In this paper, Plate 23, Figs. 8A–8B illustrate one such morphotype that is often identified (sometimes tentatively) as Stichopilium bicorne in the literature (e.g., Lazarus 1992, pl. 9, fig. 14). Comparison of this morphotype with Lophophaena laticeps (Pl. 23, Figs. 6A – 7B ) yields some striking similarities, such as the structure of the cephalis and pronounced lobe on the dorsal side of the neck area, suggesting a possible link between Stichopilium bicorne and the lophophaenids. However, even the most lophophaenid-like morphotype of Stichopilium bicorne figured in pl. 23, figs. 8A–B, differs in that it has a more reduced cephalis with relatively longer cephalic horns, lacks buttressing of the cephalic horns, and has a proportionally larger lobe in the neck region. Thus, we are not suggesting these specimens are conspecific, but rather that they could have an evolutionary relationship that justifies further study to potentially resolve this enigmatic group.

Range. Early Pliocene, EEP ( Table 1 ).

Figures

FIGURE 6. Internal skeletal structure of Arachnocorallium calvata (Haeckel, 1887) Petrushevskaya, 1971.

FIGURE 7. Internal skeletal structure of Arachnocorys umbellifera (Haeckel, 1862) Petrushevskaya, 1971.

FIGURE 8. Internal skeletal structure of Botryopera amabie n. sp.