Ceratocyrtis Bütschli 1882

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 : 30-31

Genus Ceratocyrtis Bütschli 1882 , emend Sugiyama, 1993

Type species: Cornutella ? cucullaris Ehrenberg, 1874

Description. Two-segmented lophophaenid with a small cephalis relative to the width of the thorax. The thorax is usually conical in shape. The dorsal and lateral spines protrude from the base of the cephalis rather than forming thoracic ribs, differentiating this genus from Lampromitra . The dorsal spine points downward relative to the nearhorizontal lateral spines. The lateral spines are oriented at nearly a right angle from the dorsal spine, making them difficult to identify in the same plane as the dorsal, ventral, and apical spines. Ceratocyrtis also has a distinctively elongated axobate, which extends straight downward from near the junction of the median bar and lateral spines into the interior of the thorax. The axobate is often dendritic.

Remarks. Ceratocyrtis was first described by Bütschli (1882). He recognized two separate forms in the previously described genus Cornutella ( Ehrenberg, 1839) , and broke out several species as belonging to the new genus Ceratocyrtis . Bütschli (1882) described this genus as having a muted cephalis that is difficult to distinguish in exterior outline, primary spines likely corresponding to those of Lithomelissa , and a downward-pointing apophyse (referred to as the axial spine by Sugiyama (1993), and the axobate in this paper). This definition has remained fairly consistent in the literature, with subsequent authors adding clarification to the internal skeletal characteristics. However, there has been some disagreement as to the higher-level taxonomy and the species that should be included in this genus.

Petrushevskaya (1971) considered Ceratocyrtis to be a lophophaenid, and designated the type species of Ceratocyrtis as Cornutella ? cucullaris Ehrenberg 1874 . She determined that the type species of Ceratocyrtis , Helotholus , and Bathrocalpis were not sufficiently different to justify separate genera, so she synonymized these three genera under the senior name Ceratocyrtis . Although we agree that the type species of Helotholus , H. histricosa Jørgensen, 1905 , should be in the genus Ceratocyrtis , we do not consider all species in Helotholus to fit this definition. H. praevema Weaver, 1983 , for example, we do not consider to be Ceratocyrtis , but a revision of its taxonomy is outside the scope of this paper. Nishimura (1990) considered Ceratocyrtis to belong to Sethophormidae rather than Lophophaenidae . However, she accepted the genus concepts of Bütschli, 1882, Haeckel, 1887, Petrushevskaya, 1971, Petrushevskaya and Kozlova, 1979, and Bjørklund, 1976. Like Petrushevskaya (1971), Nishimura (1990) considered Ceratocyrtis to be synonymous with Helotholus (sensu Jørgensen, 1905, and Campbell, 1954) and Bathrocalpis ( Clark and Campbell, 1942, and Campbell, 1954). Sugiyama (1993) closely followed the genus concept of Petrushevskaya (1971), but included detailed diagrams illustrating and clarifying the internal skeletal structure of Ceratocyrtis (figs. 21–22). Matsuzaki et al. (2015) remarked that Ceratocyrtis species often have a large or wide thorax with a small cephalis, whereas Helotholus species have a shorter thorax and more distinct cephalis. Therefore, they consider these to be two separate and valid genera. In the present study, we consider the type species of Helotholus ( H. histricosa ) to be within the range of variation among our other observed Ceratocyrtis species, and thus follow Petrushevskaya (1971) ’s synonymy.

Here we observed the following species belonging to Ceratocyrtis : Ceratocyrtis ? chimii n. sp., Ceratocyrtis cucullaris (Ehrenberg) Petrushevskaya, 1971 , Ceratocyrtis histricosus ( Jørgensen 1905) Petrushevskaya, 1971 , Ceratocyrtis spinosiretis ( Takahashi, 1991) Matsuzaki et al., 2015 , and Ceratocyrtis vila n. sp. Ceratocyrtis ? pseudoadvena Kozlova, 1999 is poorly documented, but does not appear to fit the description of Ceratocyrtis due to the nature of the cephalis. Ceratocyrtis erosa (Cleve) Petrushevskaya, 1971 was transferred from Cleve’s designation as Lampromitra , but it is our opinion that it should remain in Lampromitra . Similarly, Ceratocyrtis sinuosa (Popofsky) Petrushevskaya, 1971 was also transferred from Lampromitra by Petrushevskaya, but we consider it to fit better in Lampromitra than Ceratocyrtis so do not accept this transfer.

Range.?Eocene—Recent