Lophophaena rusalkae, 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 : 64-65

Lophophaena rusalkae n. sp.

Plate 29, Figs. 1A – 6 .

urn:lsid:zoobank.org:act:ABD2BBA6-AD2F-4F87-BFE1-2489F79257E8

unknown plagonid group C sp 51, Trubovitz et al., 2020, supplementary data 7.

unknown plagonid group C sp 53 cf, Trubovitz et al., 2020, supplementary data 7.

Diagnosis. A small Lophophaena with many thin spines on the thumb-shaped cephalis, and a thorax with distinct shoulders that tapers toward the base.

Description. This species has a small, thumb-shaped cephalis that has many thin spines extending from the sides and top. The apical spine is embedded in the cephalis wall and is diminished to the point of being difficult to detect. The thorax is slightly wider than the cephalis, and reaches its widest point at the shoulders, where more thin spines extend downward. Pores on the cephalis and thorax are the same size, shape, and density. Both the cephalis and thorax show approximately the same degree of silicification. When the full skeleton is preserved, the thorax has a smooth termination at its base.

Remarks. This species differs from Botryopera babayagae n. sp. (Pl. 9, Figs. 1A – 8 ) in that it has thin conical spines on top of the cephalis, and a longer, more narrow neck area. It differs from Lophophaena cylindrica (Pl. 22, Figs. 1A – 4 ) and Lophophaena hispida (Pl. 22, Figs. 5–8B ) in that it has a smaller, more thumb-shaped cephalis, with less of a constriction at the neck. It differs from Lophophaena nadezdae (Pl. 23, Figs. 1A – 2C ) in that it has fewer spines, and the cephalis is smaller, and more rounded at the top. The top of the cephalis is never open, differentiating this species from Lophophaena variabilis (Pl. 22, Figs. 9A –11C) and Lophophaena buetschlii (Pl. 24, Figs. 1A – 2B ). This species has similar overall structure to Lophophaena casperi n. sp. (Pl. 28, Figs. 1A – 9B .), but differs in its smaller size and cephalis shape ( Figure 12 ).

Material examined. 33 specimens observed from samples 321-1337D-23H- 6, 134–137cm (Late Miocene), 321-1337A-18H-6, 77–80cm (Late Miocene), 321-1337A-14H-7, 39–42cm (Late Miocene), 321-1337A-12H-5, 23–26cm (Late Miocene), 321-1337A-7H- 6, 104–107cm (Early Pliocene), and 321-1337A-6H-3, 29–32cm (Late Pliocene).

Holotype. Pl. 29, Fig. 4 ; sample 321-1337A-14H-7 , 39–42cm; ECO-138; N20-4 .

Paratypes. (1) Pl. 29, figs. 5A–B; sample 321-1337A-12H-5, 23–26cm; ECO-136; X10-2. (2) Pl. 29, figs. 2A–B; sample 321-1337A-14H-7, 39–42cm; ECO-140; Z14-2. (3) Pl. 29, figs. 1A–B; sample 321-1337A-14H-7, 39–42cm; ECO-139; Y39-3. (4) Pl. 29, figs. 2A–B; sample 321-1337A-14H-7, 39–42cm; ECO-139; X7-2. (5) Pl. 29, fig. 3; sample 321-1337A-12H-5, 23–26cm; ECO-136; Z5-4. (6) Pl. 29, fig. 6; sample 321-1337A-14H-7, 39–42cm; ECO-139; O25-3. (7) [not figured] sample 321-1337A-14H-7, 39–42cm; ECO-138; C25-4.

Measurements. Cephalis height 34–40 (37)μm; cephalis width 25–32 (28)μm; width at neck 25–31 (28)μm; width at shoulders 36–44 (41)μm. Based on 10 specimens.

Etymology. Named for the malicious female water spirit in Russian folklore, the rusalka.

Range. Late Miocene—Pliocene, in the 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 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.

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

FIGURE 9. Internal skeletal structure of Ceratocyrtis sp. C.

FIGURE 12. Chart illustrating the different cephalis dimensions of Lophophaena casperi n. sp. (blue squares) and L. rusalkae n. sp. (red triangles). L. rusalkae has a cephalis height ranging from 34-40 microns, and an average cephalis width:neck ratio of 1. By contrast, L. casperi has a higher cephalis, ranging from 44- 58 microns, and a cephalis width:neck ratio averaging 1.3. The specimen with a cephalis width:neck ratio of 1.7, which is visually the outlier on this chart, has a particularly narrow neck (23 microns), but a cephalis of typical width for this species (40 microns).