Late Neogene Lophophaenidae (Nassellaria, Radiolaria) from the eastern equatorial Pacific
Author
Trubovitz, Sarah
Author
Renaudie, Johan
Author
Lazarus, David
Author
Noble, Paula
text
Zootaxa
2022
2022-07-04
5160
1
1
158
http://dx.doi.org/10.11646/zootaxa.5160.1.1
journal article
10.11646/zootaxa.5160.1.1
11755334
10544058
A9179C79-EE43-44E4-8723-919505500049
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
).