Lophophaena ikota, Trubovitz, Sarah, Renaudie, Johan, Lazarus, David & Noble, Paula, 2022

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 : 59-60

Lophophaena ikota n. sp.

Plate 33, Figs. 1A – 7B .

urn:lsid:zoobank.org:act:ACF9629F-4970-42EE-ABE1-8F4E6A32EF32

unknown plagonid group C sp 16, Trubovitz et al., 2020, supplementary data 7.

Diagnosis. Lophophaena with a cephalis that is widest at its center and has a single conical spine on the apex, unrelated to any of the primary spines; thorax is broadly conical and has weak ribs but no appendages.

Description. This species has a thickly-silicified, kidney-shaped cephalis with a strong conical spine extending from the apex. This horn is not connected to the apical spine, which runs along the side of the cephalis and does not extend significantly through the shell wall. The cephalis of this species is widest near its center and tapers toward the top, rather than reaching its widest point in the top 1/3 (as it does in many other Lophophaena species). The thorax is long and generally cone-shaped, with several weak ribs but no spines extending outward from the primary spines. The thorax typically becomes more thinly silicified toward the base. Pore size tends to decrease both upward and downward from the neck area.

Remarks. This species differs from Lophophaena shishigae n. sp. (Pl. 35, Figs. 1–6B ) in that it is approximately twice its size, and has a more kidney-shaped cephalis that is widest at its middle. It differs from Arachnocorys jorogumoae n. sp. (Pl. 4, Figs. 1A –11) in that it does not develop several forked cephalic spines around the top third of the cephalis, and the cephalis wall tends to be thicker and more textured with strongly-framed pores. Another difference is that the thorax of Lophophaena ikota n. sp. usually has weaker ribs than Arachnocorys jorogumoae n. sp., and does not flare as widely outward. Despite its overall similar structure to A. jorogumoae , we place L. ikota in Lophophaena because it does not have any dendritic spines on the cephalis and lacks large pores at the base of the cephalis, excluding it from the definition of Arachnocorys . The cephalis shape of this species, which is slightly longer on the ventral side than the dorsal side, is common among Lithomelissa . However, since the apical spine is not free inside the cephalis, this species does not fit the definition of Lithomelissa and was placed in Lophophaena instead.

Material examined. 27 specimens observed from samples 321-1337D-26H-3W, 142–144cm (Late Miocene), 321-1337D-23H- 6, 134–137cm (Late Miocene), 321-1337A-12H-5, 23–26cm (Late Miocene), 321-1337A-10H-2, 91–94cm (Early Pliocene), 321-1337A-7H- 6, 104–107cm (Early Pliocene), and 321-1337A-6H-3, 29–32cm (Late Pliocene).

Holotype. Pl. 33, Figs. 2A–B ; sample 321-1337D-23H- 6, 134– 137cm ; ECO-145; W7-3 .

Paratypes. (1) Pl. 33, figs. 3A–B; sample 321-1337D-23H- 6, 134–137cm; ECO-145; P30-1. (2) Pl. 33, fig. 4; sample 321-1337D-23H- 6, 134–137cm; ECO-147; U11-1. (3) Pl. 33, fig. 5; sample 321-1337D-23H- 6, 134–137cm; ECO-146; Z20-4. (4) Pl. 33, figs. 7A–B; sample 321-1337D-23H- 6, 134–137cm; ECO-146; N33-3. (5) [not figured] sample 321-1337D-23H- 6, 134–137cm; ECO-145; M28-1. (6) [not figured] 321-1337D-23H- 6, 134–137cm; ECO-146; Q39-2.

Measurements. Cephalis height 52–61 (57)μm; cephalis width 38–48 (43)μm; width of neck constriction 36–43 (39)μm. Based on 14 specimens.

Etymology. Named for the ikota, a possession spirit in Russian folklore.

Range. Lower Late Miocene—Pliocene, EEP ( Table 1 ).

Figures

FIGURE 1. Diagram illustrating the general skeletal morphology of Lophophaenidae, and terminology used in this manuscript. Dashed lines indicate spines that are not visible from the angle shown, as they extend into the skeleton. An example specimen of Lophophaena casperi n. sp. is included for comparison to the diagrams.

FIGURE 2. Relative abundance of specimens and taxa belonging to Plagiacanthoidea and Lophophaenidae per sample, from IODP Site U1337 in the EEP over the last ~10 Ma. The relative percentages of total taxa are represented by the blue lines and the red lines represent the percentages of total specimens (triangles = Plagiacanthoidea; circles = Lophophaenidae). The Plagiacanthoidea was among the most abundant and speciose of radiolarian groups encountered in Trubovitz et al. (2020), with at least 10% of the specimens and 20% of the taxonomic richness in every sample. Within the Plagiacanthoidea, lophophaenids consistently made up the majority of specimens (~67%) and taxa (~61%). Data are from Trubovitz et al. (2020).

FIGURE 3. Locality map of IODP Site U1337, where all samples for this study were collected. Map from Google EarthTM.

FIGURE 4. Examples of specimen measurements discussed in the Systematic Paleontology section of this study.

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

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

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