Limnocythere curvispinosa, Jiang & Wang & Ge & Xie & Duan & Fan & Zhai, 2025

Jiang, Ping, Wang, Qianwei, Ge, Dingkuan, Xie, Manping, Duan, Lizeng, Fan, Jiawei & Zhai, Dayou, 2025, Limnocythere curvispinosa sp. nov. (Crustacea, Ostracoda) from two ancient lakes in the Xiaojiang Fault zone, Yunnan Province, southwestern China, Zoosystematics and Evolution 101 (4), pp. 2369-2386 : 2369-2386

publication ID	https://doi.org/10.3897/zse.101.168416
publication LSID	lsid:zoobank.org:pub:B1903CF4-5179-4208-A4FE-0EE920CFFADC
DOI	https://doi.org/10.5281/zenodo.17791676
persistent identifier	https://treatment.plazi.org/id/D66A354C-9813-5030-92C0-3A9BF8C0D5B1
treatment provided by	Zoosystematics and Evolution by Pensoft
scientific name	Limnocythere curvispinosa
status	sp. nov.

Treatment

Limnocythere curvispinosa sp. nov.

Figs 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7

? 1999 Limnocythere subornamenta Hou, 1982 — Liu and Lu: 411, pl. I, fig. 12.

Type locality.

Site Y 394 (Fig. 1 B View Figure 1 , Table 1 View Table 1 ), southern part of Fuxian Lake , Yunnan Province, China ( 24°27'00"N, 102°52'45"E, water depth 77.0 m) GoogleMaps .

Type material.

Holotype: dissected female ( WOC 441 ), from type locality GoogleMaps . Allotype: dissected male ( WOC 694 ), from site Y 474 . Paratypes: nine dissected females ( WOC 442 ‒ WOC 445 and WOC 451 ‒ WOC 455 ) from type locality (Fig. 1 B View Figure 1 , Tables 1 View Table 1 , 2 View Table 2 ) GoogleMaps .

Other material examined.

Twelve undissected females from type locality, one dissected female ( WOC 431 ) from site Y 404, two dissected females ( WOC 686 , WOC 687 ) and 41 undissected females from site Y 546, and one dissected female ( WOC 695 ) from site Y 474 (Fig. 1 B View Figure 1 , Table 1 View Table 1 ). A large number of valves from sediment cores YZHA and YZHB.

Derivation of name.

From Latin curva and spina, denoting the three posteriorly curved spines on the dorsal margin of RV.

Dimensions.

Female LVs (n = 15) L 404‒469 µm (averaging 436 µm), H 230‒257 µm (averaging 242 µm), H / L 0.535 ‒0.575 (averaging 0.556). Female RVs (n = 15) L 415‒465 µm (averaging 436 µm), H 227‒256 µm (averaging 241 µm), H / L 0.531 ‒0.573 (averaging 0.553). Female LVs 1 to 6 µm longer than RVs of same individual, averaging 3 µm. Male LVs (n = 2) L 411‒437 µm (averaging 424 µm), H 213‒233 µm (averaging 223 µm), H / L 0.518 ‒0.533 (averaging 0.526). Male RVs (n = 3) L 423‒430 µm (averaging 426 µm), H 219‒230 µm (averaging 225 µm), H / L 0.518 ‒0.535 (averaging 0.529). See Tables 2 View Table 2 , 3 View Table 3 for detailed measurements.

Diagnosis.

Small to intermediate-sized Limnocythere . Dorsal margin of valve inclined posteriorly (feature of L. stationis group). Posterior section of dorsal margin of RV with three prominent, posteriorly curved spines in adult and late juveniles, with less than three spines in instars younger than Ad- 3. Antero-dorsal corner of LV with one (rarely two or absent) small anteriorly curved spine. Male Cp more elongate than female, with less inclined dorsal margin. Posterior area of Cp not laterally inflated in either sex. Valve surface with reticulation, and sometimes with one prominent node in postero-ventral area. Sizes of thoracic legs L 6 > L 5 > L 7. Postero-ventral seta present on protopods of all thoracic legs. Male Hp slender, with triangular distal lobe. Female genital lobe saddle-shaped.

Description

(referring to female unless otherwise noted). Valves sub-reniform in lateral view (Fig. 2 A ‒ D View Figure 2 ). Dorsal margin straight or nearly straight, strongly inclined posteriorly. Posterior section of RV dorsal margin with three prominent, usually posteriorly curved spines. Length of spines usually 20‒30 μm. Antero-dorsal corner of LV with one small anteriorly curved spine (Fig. 2 A, C View Figure 2 ), rarely two (Fig. 3 I, K View Figure 3 ) or absent. Such rare morphological variations found in both juveniles and adults. Anterior margin broadly rounded. Posterior margin narrowly rounded. Ventral margin concave. Two shallow vertical sulci present. Anterior sulcus originating near antero-dorsal corner, short (Fig. 2 A, B View Figure 2 , white arrowheads). Posterior sulcus extending from dorsal margin to slightly above mid-height (Fig. 2 A, B View Figure 2 , yellow arrowheads). Anterior and posterior sides of posterior sulcus each with one blunt bulge. Adductor muscle scars situated in elongate depression immediately below posterior sulcus. Valve surface with sparsely or densely arranged reticulation. Postero-ventral area of valve sometimes with a prominent rounded node (Figs 2 A, B View Figure 2 , 3 H, J View Figure 3 ), a phenomenon comparable to variable noding in some other non-marine ostracods ( Yin et al. 1999; Van Harten 2000). Free valve margins with compressed zone, which is wider along anterior margin than along posterior margin. Radial pore canals straight and unbranched, sparsely distributed along compressed zone (Fig. 4 View Figure 4 ). False pore canals present. Sieve-type pore canals belonging to type C classified by Danielopol et al. (2018), consisting of sieve-plate and central seta (Figs 2 G View Figure 2 , 3 L View Figure 3 ). Proximal shaft of seta densely annulated (Fig. 2 G View Figure 2 ). Hinge lophodont (cf. Danielopol et al. 1989), consisting of undivided anterior and posterior teeth and median groove in RV (Fig. 2 D, H, I View Figure 2 ), and anterior and posterior sockets and fine median ridge in LV (Fig. 2 C View Figure 2 ).

Male valves more elongate than female (Fig. 2 E, F View Figure 2 ). Dorsal margin less inclined (Fig. 5 View Figure 5 ), with sloping angle of 13.5 ° ‒ 18.4 °, comparing to 17.6 ° ‒ 21.1 ° of female (Tables 2 View Table 2 , 3 View Table 3 ). Ventral margin of male more widely concave than female (Fig. 5 View Figure 5 ).

Brief description of ontogenetic change of valve morphology (Fig. 3 A ‒ H View Figure 3 ): From Ad- 7 (Ad- 8 not investigated) to the adult, valve shape generally becoming more elongate and dorsal margin becoming less inclined. RV of Ad- 7 already with one dorsal spine (Fig. 3 A View Figure 3 ). Second spine appearing in Ad- 6 (Fig. 3 B View Figure 3 ). Third spine appearing in Ad- 3 (Fig. 3 E View Figure 3 ). Proposed length ranges of different developmental stages as in Suppl. material 1.

A 1 (Fig. 6 A View Figure 6 ) with five segments. First segment robust, anteriorly directed. Other segments ventrally directed. Second segment elongate, carrying one postero-apical seta extending almost to distal end of fourth segment. Second segment with densely arranged short pseudochaetae along anterior margin. Third segment short, bearing one antero-apical seta. Fourth segment elongate, consisting of two sections. Proximal section short and stout, with one antero-apical and one postero-apical seta. Distal section more elongate and slightly narrower, with three antero-apical setae and one postero-apical seta. Fifth segment slender, with two antero-apical setae and branched postero-apical y 1. Aesthetasc branch of y 1 slightly shorter than setal branch.

Limb stem of A 2 (Fig. 6 B, C View Figure 6 ) consisting of coxa, basis, and three endopodal segments. Basis apically carrying spinneret seta (exopod) extending somewhat beyond terminal segment. First endopodal segment short and stout, with one ventro-apical setae. Second endopodal segment elongate, consisting of two sections. Proximal section with two dorso-apical setae and three ventro-apical setae, one being very weakly sclerotised aesthetasc (Y). Distal section with two unequal ventro-apical setae, one sometimes very small (hollow arrowhead in Fig. 6 C View Figure 6 ). Pseudochaetae present on dorsal areas of first and second endopodal segments and sometimes showing appearance of small setae (Fig. 6 C View Figure 6 , solid arrowheads). Third endopodal segment (distal segment) with three unequal claws (Fig. 6 B View Figure 6 ). Distal claws of male not preserved; therefore, potential sexual dimorphism [i. e., distally bifurcated claw of male Limnocythere stationis Vávra, 1891 recorded by Smith and Janz (2009)] not verified.

Md coxa (Fig. 6 D View Figure 6 ) elongate, endite distally with eight processes. First six processes tooth-like, strongly sclerotized and progressively shorter. Rest two processes slender, seta-like. One short seta present between two largest processes (lost in specimen illustrated in Fig. 6 D View Figure 6 due to preservation). Palp (Fig. 6 E, F View Figure 6 ) consisting of basis and three endopodal segments. Basis with one short ventro-apical seta. First endopodal segment with one dorsal seta and four ventro-apical setae. Second endopodal segment with four unequal dorsal setae, one short thick lateral seta, and one ventro-apical seta. Third endopodal segment with four unequal setae / claws.

Mx endopod (Fig. 6 G View Figure 6 ) 2 - segmented. First segment comparatively short, with three anterior setae and one posterior seta. Second segment with four setae. Protopod with three setose endites and one respiratory plate fringed with rays (not illustrated because of weak sclerotisation and overlap).

L 5 ‒ L 7 (Fig. 6 H ‒ L View Figure 6 ) with similar chaetotaxies. L 6 > L 5 > L 7 in length. Protopod robust, with two proximo-dorsal setae and two ( L 5) or one ( L 6 and L 7) apical seta, plus one proximo-ventral seta. Size of proximo-ventral seta somewhat variable among specimens (e. g., Fig. 6 View Figure 6 , I vs. J). First endopodal segment elongate, with one antero-apical seta. Second and third segments much shorter, without seta. Fourth segment very small, fused with distal claw.

GL (Fig. 6 M View Figure 6 ) of each side somewhat saddle-like, with simple half coil internally.

Hp of male (Fig. 7 View Figure 7 ) dagger-shaped, consisting of rounded proximal section and relatively slender distal section. Median area of inner margin with slightly curved sclerite [marked with asterisk in Fig. 7 C View Figure 7 , see also same structures of Limnocythere species illustrated by Smith and Janz (2009)]. A slender hkp with swollen base attached to distal end of this sclerite. Cop with one full coil medially and fine tube distally extending into dl, which is sub-triangular in shape and with nearly pointed end.

Brush-shaped organs of male not preserved.

Differential diagnosis.

The presence of posteriorly curving dorsal spines on RV distinguishes the new species from almost all congeners. The small spine on the antero-dorsal corner of LV is another diagnostic feature. Limnocythere dorsosicula De Deckker, 1981 from Australia also has dorsal spines on RV (De Deckker 1981). However, those spines are relatively shorter and thinner than the spines of L. curvispinosa sp. nov. and are variable in number (three to six). In our new species, no RV has more than three dorsal spines. A few RV from the core have less than three dorsal spines, but taphonomic loss of spines cannot be excluded. In addition, L. dorsosicula lacks the antero-dorsal spine on LV. But the most significant differences between L. dorsosicula and the new species are seen in the internal morphology. The A 1 of L. dorsosicula has six segments, compared to five in the new species. The proximo-ventral seta on the prodopodal segment of the walking legs is tiny or even absent in L. dorsosicula . Also, in L. dorsosicula , L 7 is longer than L 5 (fig. 1 F, G of De Deckker 1981; but see our Discussion section), while in the new species, L 5 is longer than L 7. The Hp of L. dorsosicula is stouter than that of the new species and has a curved appearance. The above differences unambiguously separate L. dorsosicula from the new species. Limnocythere xinanensis Zhao, 1987 , recovered from the Pleistocene to Recent strata of Caohai Lake of Guizhou Province adjacent to Yunnan, sometimes also carries three dorsal spines on RV (fig. 2 of pl. 14, 130 of Zhao 1987). However, our geometric morphometric analysis indicates that L. xinanensis is stouter than L. curvispinosa sp. nov. and has a less inclined dorsal margin (Suppl. material 2). Such differences create dissimilarities of 1.9 % ( RV) and 1.7 % ( LV) from the new species, values much higher than the intraspecific variation (0.9 %) of the new species (Suppl. material 3). In addition, the LV of L. xinanensis lacks the antero-dorsal spine seen in the new species.