Arachnocorallium calvata sensu Petrushevskaya 1971
Creators: name: Trubovitz, Sarah
name: Renaudie, Johan
name: Lazarus, David
name: Noble, Paula
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Chromista
Radiozoa
Polycystina
Nassellaria
Plagiacanthidae
Arachnocorallium
Arachnocorallium calvata

description: Arachnocorallium calvata (Haeckel, 1887) Petrushevskaya, 1971   
Plate 3, Figs. 1A – 3B.  
 Arachnocorys circumtexta (juv.?), Hertwig, 1879, p. 79, pl. 8, fig. 2a.   
 Arachnocorys hexaptera n. sp., Haeckel, 1887, sp. 1271.   
 ? Lychnodictyum scaphopodium n. sp., Haeckel, 1887, pl. 56, fig. 4.   
 Psilomelissa calvata n. sp., Haeckel, 1887, p. 1212, pl. 56, fig. 3.   
 Peridium spinipes Haeckel, Popofsky, 1913, text-figs. 33–34 (non text-figs. 31–32).   
 Arachnocorallium calvata Haeckel, emend., Petrushevskaya, 1971, pl. 70, figs. 1–8.   
 Arachnocorallium calvata Haeckel group, Boltovskoy and Riedel, 1987, pl. 3, fig. 24.   
 Arachnocorallium calvata Haeckel, Itaki et al., 2008b, pl. 4, fig. 27 (? fig. 26).   
 Arachnocorallium calvata Petrushevskaya, Bjørklund et al., 2012, pl. 4, figs. 8–9.   
 Arachnocorallium calvata Petrushevskaya group, Matsuzaki et al., 2019, pl. 2, figs. 6–9.   
 Arachnocorallium calvata Haeckel, Matsuzaki et al., 2020, pl. 6, fig. 7, 9–10 (?figs. 6, 8).   
 Arachnocorallium calvata Haeckel, Trubovitz et al., 2020, supplementary data 7.   
 ? Arachnocorallium cf. calvata Haeckel, Trubovitz et al., 2020, supplementary data 7.   
 Remarks. This species appears to be often confused with species of Archiperidium (formerly Peridium), another lophophaenid that lacks a thoracic segment, in the literature. Here we follow Petrushevskaya’s (1971) concepts of Arachnocorallium and Archiperidium. Archiperidium differs from the former in that the apical spine is more clearly expressed, usually with a set of relatively large, paired pores on the cephalis running along the apical spine. However, even ignoring the confusion regarding Archiperidium and Arachnocorallium, Arachnocorallium calvata (Haeckel) Petrushevskaya, 1971, seems to have highly variable development and/or preservation of cephalic horns and the thoracic segment. In the material we observed, some Arachnocorallium specimens had short spines on the cephalis, or none at all, which we identified as Arachnocorallium calvata sensu Petrushevskaya (1971), pl. 70, figs. 1–6, 8 (Pl. 3, Figs. 1A–B in this manuscript). Other specimens we observed resembled Arachnocorallium calvata in most characteristics, except that these specimens exhibited three long, thin cephalic horns, that extended upward by approximately the same length as the cephalis (Pl. 3, Figs. 2A–B). Petrushevskaya (1971) mentioned observing an alternate form of Arachnocorallium calvata with three horns on the cephalis. She illustrated one such specimen on pl. 70, fig. 7, but this individual differs from our specimens in that its spines are shorter and relatively weaker. In Trubovitz et al. (2020) these 3-horned specimens were considered Arachnocorallium cf. calvata; however, it is possible that spine development could constitute intraspecific variation or be a preservational artifact. Future work involving well-preserved specimens and genetic diversity within this genus is needed to determine whether specimens showing different types of cephalic spines, and different levels of thorax development should be considered multiple species.   
 Range. Arachnocorallium calvata was present from the early Late Miocene—Recent in the EEP. The form of this species exhibiting three equally-prominent spines on the cephalis was observed only from the Early Pleistocene– Recent in the EEP. See Table 1.
description: Published as part of Trubovitz, Sarah, Renaudie, Johan, Lazarus, David & Noble, Paula, 2022, Late Neogene Lophophaenidae (Nassellaria, Radiolaria) from the eastern equatorial Pacific, pp. 1-158 in Zootaxa 5160 (1) on page 17, DOI: 10.11646/zootaxa.5160.1.1, http://zenodo.org/record/10544058