Lophophaena shishigae, 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 : 65-66

Lophophaena shishigae n. sp.

Plate 35, Figs. 1–6B .

urn:lsid:zoobank.org:act:A289D1AC-8B84-406E-B5E7-C6CF4358263F

unknown plagonid group C sp 17 (partim.), Trubovitz et al., 2020, supplementary data 7.

Diagnosis. Lophophaena with a small, balloon-shaped cephalis that has numerous conical spines, and a flared conical thorax that has multiple strong ribs.

Description. The cephalis of this species is narrow at its base and reaches its widest point about ⅔ of the way up, giving it a balloon-like shape. There are many conical spines protruding from the cephalis, one of which is the apical spine, though it is not differentiated from the others. The small pores on the cephalis are about the same size, shape, and density as those on the thorax. The thorax extends down from the neck constriction in a roughly conical shape, flaring outward to varying degrees among specimens. The thorax has multiple strong ribs, and may become hyaline toward the base in some individuals (i.e., fig. 2).

Remarks. This species is similar to Lophophaena variabilis (Pl. 22, Figs. 9A –11C), except that the cephalis is always heavily-silicified, rounded, and closed at the top. It reaches its widest point about 2/3 up from the base of the cephalis. On the thorax, the numerous spines have a tendency to form long ribs, rather than protruding through the thorax wall as they commonly do in L. variabilis. It differs from L. casperi (Pl. 28, Figs. 1A–9B) in that the cephalis is relatively narrower, particularly at its widest point, and the thorax flares outward in a roughly conical shape, rather than expressing sharp shoulders before tapering inward toward the base. The more widely flared thorax, strong ribs, and more balloon-shaped cephalis also distinguish this species from L. rusalkae n. sp. (Pl. 29, Figs. 1A – 6 ). This species differs from Arachnocorys jorogumoae n. sp. (Pl. 4, Figs. 1A –11) in that it is consistently much smaller in size, has relatively smaller pores, and does not have dendritic spines on the cephalis.

Material examined. 14 specimens observed from Late Miocene samples 321-1337D-23H- 6, 134–137cm and 321-1337A-21H-1, 33–35cm.

Holotype. Pl. 35, Fig. 1 ; sample 321-1337D-23H- 6, 134– 137cm ; ECO-146; W4-2.

Paratypes. (1) Pl. 35, figs. 2A–B; sample 321-1337D-23H- 6, 134–137cm; ECO-146; W37-1. (2) Pl. 35, fig. 3; sample 321-1337A-21H-1, 33–35cm; ECO-144; V 2-2. (3) Pl. 35, fig. 4; sample 321-1337D-23H- 6, 134–137cm; ECO-147; W30-4. (4) Pl. 35, fig. 5; sample 321-1337D-23H- 6, 134–137cm; ECO-146; Y6-1. (5) Pl. 35, figs. 6A–B; sample 321-1337D-23H- 6, 134–137cm; ECO-146; A34-4.

Measurements. Cephalis height 33–41 (37)μm; cephalis width 25–30 (27)μm; width at neck 19–25 (23)μm; width at shoulders 39–68 (51)μm. Based on 8 specimens.

Etymology. Named for Shishiga, the troublesome female swamp creature in Russian mythology.

Range. Late Miocene in the EEP, range not well constrained ( 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 9. Internal skeletal structure of Ceratocyrtis sp. C.