Triangocypretta angustus, Ferreira & Higuti & Martens, 2023

Ferreira, Vitor Góis, Higuti, Janet & Martens, Koen, 2023, On a new genus and four new species of the subfamily Cyprettinae (Crustacea, Ostracoda) from Brazilian floodplains, Zootaxa 5343 (5), pp. 401-438 : 418-425

publication ID	https://doi.org/ 10.11646/zootaxa.5343.5.1
publication LSID	lsid:zoobank.org:pub:24E92041-4F5C-42E2-B7A3-401BEA46D2C8
DOI	https://doi.org/10.5281/zenodo.8345969
persistent identifier	https://treatment.plazi.org/id/E2037D4C-B78F-45FA-90B3-2B2C95EEBC07
taxon LSID	lsid:zoobank.org:act:E2037D4C-B78F-45FA-90B3-2B2C95EEBC07
treatment provided by	Plazi
scientific name	Triangocypretta angustus
status	gen. et spec. nov.

Treatment

Triangocypretta angustus View in CoL gen. et spec. nov.

( Figs. 10– 13 View FIGURE 10 View FIGURE 11 View FIGURE 12 View FIGURE 13 , 18E–F View FIGURE 18 )

urn:lsid:zoobank.org:act:E2037D4C-B78F-45FA-90B3-2B2C95EEBC07

Diagnosis

CpD relatively narrow; Cp surface with long setae and deep pits; CpLl with a sub-triangular shape and with ventral margin slightly concave; RV clearly overlapping LV along anterior, dorsal, and posterior margins; T2 with d 1 half-length of d 2.

Type locality

Brazil • Amazon River floodplain. Poraquequara Lake IV (AMA87), in the roots of Eichhornia crassipes , Pistia stratiotes and Salvinia spp. in the Amazon River floodplain. Leg. JH, collected on May 18 th, 2012. Coordinates: 03°02’20.7”S, 59°47’54.0”W.

Type material

Holotype: A female with soft parts dissected in glycerin in a sealed slide and valves stored dry in a micropaleontological slide (MZUSP 44395).

Paratypes: Three female specimens dissected and stored as the holotype (MZUSP 44396, MZUSP 44397 and MZUSP 44398). Five specimens with valves stored dry in micropaleontological slides (MZUSP 44399, MZUSP 44400, MZUSP 44401, MZUSP 44402 and MZUSP 44403).

Etymology

This species was named after the characteristic narrow carapace in dorsal and ventral view (narrow is “angusto” in Latin).

Other localities

Triangocypretta angustus gen. et spec. nov. is restrict to the Amazon River floodplain, occurring only in lentic environments (see Table 2 View TABLE 2 ).

Measurements

See Table 1 View TABLE 1

Description

LVi ( Figs. 10A, C View FIGURE 10 , 18E View FIGURE 18 ) highly arched (H ca. 2/3 of L), of a more sub-triangular shape, with greatest height situated in the middle; calcified inner lamella wide along anterior margin and narrow along ventral and posterior margins; anteriorly with incomplete inner list (running halfway up the anterior margin); postero-ventrally ( Fig. 10C View FIGURE 10 ) with a reduced inwardly displaced selvage, not running parallel to valve margin, and with inner margin of the calcified inner lamella fortified by an inner list; few setae present along posterior margin; ventral margin slightly concave; ca. 15 well-developed seta along anterior margins.

RVi ( Figs. 10B, D View FIGURE 10 , 18F View FIGURE 18 ) with similar shape as LVi; with a submarginal groove along ventral margin; ca. 14 septa along anterior margins.

CpLl ( Figs. 10E, H View FIGURE 10 ) with a sub-triangular shape; strongly arched dorsally, with greatest height also situated in the middle region; external surface ( Fig. 10H View FIGURE 10 ) set with long setae and deep pits; RV overlapping LV at the dorsal; posterior and ventral margins. CpD and CpV ( Figs. 10F, G View FIGURE 10 ) relatively narrow, W less than 2/3 of L, anterior and posterior margins with blunt ends. CpV with RV overlapping LV on all sides, especially in the middle region with a flap.

A1 ( Fig. 11A View FIGURE 11 ) consisting of seven segments. The first segment with three setae (two long ventro-apical and one shorter mid dorsal); Wouters organ not seen. Second segment with one dorsal seta, reaching middle of third segment; Rome organ not seen. Third segment with one short dorso-apical setae and one short ventro-apical (both reaching beyond tip of fourth segment). Fourth segment with two unequal short ventro-apical short setae and two long dorso-apical setae. Fifth segment with two short (almost reaching tip of the terminal segment) and two long dorso-apical setae. Sixth segment with four long apical setae, and a short α-seta reaching tip of the terminal segment. Terminal segment apically carrying one long aesthetasc y a, one medium length seta (with half-length of y a) and two long setae.

A2 ( Figs. 11B, C View FIGURE 11 ) composed of six segments (two-segmented protopodite, one-segmented exopodite and threesegmented endopodite). Protopodite carrying four ventral setae, one with medium length, located close to the base of the protopodite, two mid-ventral (unequally with medium length) and one long apical setae (ca. three times length of the short ones). Exopodite consisting of a short plate with three setae, two unequal but short and one long (reaching middle of second endopodite). First endopodal segment with one mid-ventral aesthetasc Y (ca. half-length of segment); one medium length and hirsute ventro-apical seta (ca. length of segment), five long hirsute natatory setae (reaching beyond tips of G claws) and one short seta accompanying the natatory setae (almost reaching tips of second endopodal segment). Second endopodal segment with two equal medium dorsal setae, and a group of four mid-ventral t-setae (three equally medium length and one short); three unequally long z setae (z 1, z 2 and z 3); and three claws (G 1 and G 3 equally long; G 2 slightly longer); one short aesthetasc y 2. Terminal segment ( Fig. 11C View FIGURE 11 ) with one long claw G M, and one medium length claw G m; one aesthetasc y 3 and accompanying seta (slightly longer than y 3); seta g not observed.

MdCoxa ( Fig. 12A View FIGURE 12 ) consisting of an elongated plate with ca. six apical teeth intercalated with short setae; one hirsute sub-apical seta on dorsal margin. MdPalp ( Fig. 12C, D View FIGURE 12 ) consisting of four segments. First segment with long setae S 1 and S 2; one long smooth seta and short, narrow, smooth α-seta. Second segment ventrally with a cone-shaped and hirsute β seta and three long and one short hirsute setae; dorsally with a group of two unequal but long setae and one short seta (ca. half-length of long ones). Third segment dorsally with a group of four long setae; apically with three long and one medium length setae and a cone-shaped, hirsute γ seta. Last segment ( Fig. 12D View FIGURE 12 ) with three claws and three setae.

Mx1 ( Fig. 12B View FIGURE 12 ) with a respiratory plate (not illustrated), three endites (chaetotaxy not fully illustrated) and a two-segmented palp. First palp segment with a lateral seta of medium length, and six apical setae unequally long. Second palp segment rectangular, c. 1.5x as long as basal width; apically with one long claw, and two long and three shorter setae. Third endite with one very long lateral seta and two smooth claws (Zahnborsten). First endite with two subequal but long “sideways directed bristles”. Two basal setae subequal and of medium length.

T1 ( Figs. 13A, B View FIGURE 13 ) composed of an endopodite and a protopodite. Endopodite ( Fig. 13B View FIGURE 13 ) a palp with three unequally short apical hirsute setae. Protopodite with two equally short a-setae and one short d seta, b seta missing; 10 apical hirsute and unequally short setae and three equally short sub-apical setae.

T2 ( Fig. 13C View FIGURE 13 ) composed of five segments. First segment with seta d 1 short. Second segment with seta d 2 of medium length, c. 3x the length of d 1. Third segment with seta e long. Fourth segment medially divided into a and b segments; a segment with long apical f seta; b segment apically with a short g seta. Terminal segment apically with two short setae h 1 and h 3 (ca. half-length of h 1); and a long claw h 2 weakly serrated in its distal part.

T3 ( Fig. 13D View FIGURE 13 ) composed of four segments. First segment with three setae of medium length, slightly unequal (d 1, d 2 and d p; almost as long as second segment). Second segment with a short apical e seta (reaching halfway third segment). Third segment with short sub-apical f seta. Third segment fused with fourth segment, forming a pincer-shaped organ,; with a short seta h 1; longer h 2 claw; medium length and hirsute h 3 seta.

CR ( Fig. 13E View FIGURE 13 ) with long and stout ramus, two long claws (one apical G a shorter than ramus; and one shorter sub-apical G p, slightly longer than half G a,); one short and sub-apical seta S p (half-length of G p), apical seta S a absent.

CR attachment ( Fig. 13F View FIGURE 13 ) a single short and narrow rod, without bifurcation.

Differential diagnosis

Of the four new species described here, Triangocypretta angustus gen. et spec. nov. is the smallest one (see Table 1 View TABLE 1 ), and with the most distinguishable carapace shape. It also has the RV overlapping LV, but without a pointed anterior margin of the RV, as observed in Triangocypretta labiata gen. et spec. nov. The carapace surface is covered with deep pits and a relatively few setae. In dorsal view, Triangocypretta angustus gen. et spec. nov. is quite distinguishable: whereas the other three species described here share a rounded and broad dorsal shape, Triangocypretta angustus gen. et spec. nov. is much narrower, while anterior and posterior ends are bluntly pointed.

The soft part morphology is quite similar to the three other new species described here, the only differences being noticed are in the MdPalp, T2 and CR. The MdPalp has four dorsal setae on the third segment (as in Triangocypretta nates gen. et spec. nov. see below), which is different from Triangocypretta labiata gen. et spec. nov., which has three dorsal setae. On the T2, the d 1 seta is only half the length of the d 2 seta in Triangocypretta labiata gen. et spec. nov. (subequal in T. hirsuta and T. labiata ).

Ecology

This species was recorded in a narrow range of environmental variables: water temperature of 31.5ºC; pH range was 9.5–9.7; electrical conductivity range was 51.3–51.5 μS. cm-1; dissolved oxygen range was 2.1–2.9 mg. L- 1 (see Table 2 View TABLE 2 , not all localities included)