Lithomelissa dybbuki, 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 : 43-44

Lithomelissa dybbuki n. sp.

Plate 19, Figs. 1–7 .

urn:lsid:zoobank.org:act:9E726441-61BB-47AB-8B7B-B29E7A84ADBD unknown plagonid group C sp 24, partim., Trubovitz et al., 2020, supplementary data 7.

unknown plagonid group C sp 26 cf, partim., Trubovitz et al., 2020, supplementary data 7.

unknown plagonid group C sp 43, Trubovitz et al., 2020, supplementary data 7.

Diagnosis. A small Lithomelissa with a hemispherical cephalis that exhibits only one spine—the apical horn, and has a thorax ~1.5x the width of the cephalis.

Description. This species has a very small hemispherical cephalis and an apical spine passing freely through it, which extends as an apical horn that is at least as long as the cephalis itself. In some specimens, the apical horn has a bulb of extra silica at the tip (i.e., figs. 2, 5, and 6). The collar structure is sunken into the thorax, so that this species lacks the long neck constriction present in many other Lithomelissa species. The pores on the cephalis and thorax are approximately consistent in size and shape, except for the ring of enlarged pores present at the top of the thorax where it meets the cephalis. The thorax is roughly conical in shape, though may taper slightly toward the base. If present, appendages originating from the lateral and dorsal spines are very short and weak. The thorax has a jagged termination with short feet, when fully preserved (fig. 7).

Remarks. This species has somewhat similar segment proportions to Lithomelissa babai n. sp. (Pl. 18, Figs. 1A – 5B .), but is smaller overall and is usually more weakly silicified. It also differs from L. babai in that it has only one spine (the apical horn) on the cephalis. These two species share the characteristic of having a collar structure sunken into the thorax, differentiating them from many other Lithomelissa taxa that exhibit a distinct neck constriction, and suggesting a possible close relationship between them. This species differs from Lithomelissa sirin n. sp. (Pl. 17, Figs. 1 –11B) and L. mitra (Pl. 15, Figs. 4A – 6 ) in that and the cephalis is smaller in both absolute size and proportion, with the thorax being significantly wider than the cephalis.

Material examined. 84 specimens observed from samples 321-1337A-14H-7, 39–42cm (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), 321-1337A-6H-3, 29–32cm (Late Pliocene), 321-1337A-5H-5, 11–14cm (Late Pliocene), 321-1337A-4H- 6, 115–118cm (Early Pleistocene), 321-1337A-4H-2, 16–19cm (Middle Pleistocene), 321-1337A-3H- 2, 103–106cm (Middle Pleistocene), and 321-1337A-2H-3, 76–79cm (Late Pleistocene).

Holotype. Pl. 19, Figs. 5A–B ; sample 321-1337A-4H- 6, 115– 118cm ; ECO-132; C25-1.

Paratypes. (1) Pl. 19, fig. 3; sample 321-1337A-4H- 6, 115–118cm; ECO-131; C38-2. (2) Pl. 19, fig. 1; sample 321-1337A-4H- 6, 115–118cm; ECO-131; O34-1. (3) Pl. 19, figs. 4A–B; sample 321-1337A-4H-2, 16–19cm; ECO-127; X18-3. (4) Pl. 19, figs. 6A–B; sample 321-1337A-4H- 6, 115–118cm; ECO-132; Y35-2. (5) [not figured] sample 321-1337A-4H-2, 16–19cm; ECO-128; E20-4. (6) [not figured] sample 321-1337A-4H-2, 16–19cm; ECO-127; F21-1.

Measurements. Cephalis height 28–32 (30)μm; cephalis width 25–29 (27)μm; width of thorax at shoulder area 41–48 (44)μm.

Etymology. Named for the evil wandering spirit of Jewish folklore, the dybbuk.

Range: Upper Late Miocene—Late Pleistocene, 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.