Arachnocorys jorogumoae, 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 : 20

Arachnocorys jorogumoae n. sp.

Plate 4, Figs. 1A –11.

urn:lsid:zoobank.org:act:37C96B78-C0AF-40C6-8914-BE371896442F

unknown plagonid group C sp 1, partim., Trubovitz et al., 2020, supplementary data 7.

Diagnosis. Arachnocorys with a relatively elongated cephalis that reaches maximum width ~3/4 of the way up and has several branching spines; the thorax is broad, ribbed, with irregular pores and no distinct gaps near the base of the cephalis.

Description. Arachnocorys with a well-developed, relatively long balloon-shaped cephalis that has several ridges and spines that can be branching. The cephalis has a narrow constriction at the neck area. The gaps/large pores between cephalis and thorax are diminished compared to other species in this genus. The thorax is broad, can grow up to twice the length of the cephalis, and has numerous strong ribs that form teeth at the base of the shell.

Remarks. This species is similar to Arachnocorys umbellifera (Haeckel) Petrushevskaya, 1971 (Pl. 3, Figs 6A – 8B ), except that the cephalis is proportionally longer and has a more distinct neck area. In the material we observed, this species also tends to be more heavily silicified and overall more robust than A. umbellifera . Although these two species have overlapping stratigraphic ranges, A. umbellifera was more common in the Pleistocene and Pliocene whereas A. jorogumoae was more common in the Late Miocene. A. jorogumoae differs from A. circumtexta (pl. 3, figs. 4–5) in that there are diminished gaps between cephalis and thorax, making it uncertain whether this species should be considered Lophophaena or Arachnocorys . However, many A. umbellifera specimens also have diminished gaps between cephalis and thorax. We place it into Arachnocorys due to its shared characteristics with A. umbellifera and A. circumtexta , which both also have dendritic spines on the cephalis and strong ribs on the thorax, diagnostic characteristics of Arachnocorys .

Material examined. 34 specimens; most were from Late Miocene samples 321-1337A-14H-7, 39–42cm and 321-1337A-16H- 6, 121–124cm, and some were from samples 321-1337A-21H-1, 33–35cm (Late Miocene) and 321-1337D-30H-3, 103–104 (Middle Miocene).

Holotype. Pl. 4, figs. 2A–B; sample 321-1337A-14H-7, 39–42cm; ECO-138; X12-1.

Paratypes. (1) Pl. 4, figs. 1A–B; sample 321-1337A-16H- 6, 121–124cm; ECO-141; L11-3. (2) Pl. 4, fig. 3; sample 321-1337A-14H-7, 39–42cm; ECO-138; Q20-3. (3) Pl. 4, figs. 4A–B; sample 321-1337A-21H-1, 33–35cm; ECO-144; E18-4. (4) Pl. 4, fig. 8; sample 321-1337A-16H- 6, 121–124cm; ECO141; K29-1. (5) Pl. 4, fig. 9; sample 321-1337A-16H- 6, 121–124cm; ECO-142; N34-3. (6) Pl. 4, fig. 7; sample 321-1337A-16H- 6, 121–124cm; ECO-143; W5-1.

Measurements. Height of cephalis 53–68 (62), maximum width of cephalis 41–55 (48), width at neck constriction 28–40 (35). Based on 13 specimens.

Etymology. Named for the deadly spider-woman yokai of Japanese folklore, Jorôgumo.

Range. Middle—Late Miocene in the EEP, precise upper and lower limits not certain ( 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 6. Internal skeletal structure of Arachnocorallium calvata (Haeckel, 1887) Petrushevskaya, 1971.

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