An Ordovician ostracod palaeopsychrosphere?

Ostracods are tiny bivalved crustaceans with a fossil record extending into rocks of the Lower Ordovician. They occupy almost all aquatic environments today, from the ocean abyssal planes to damp forest leaf litter. Their stratigraphical record suggests they had diversified into a wide range of marine and non-marine habitats already during the Palaeozoic. Through the Ordovician, ostracods are mostly known from marine shelf depositional settings. These are mostly podocope ostracods that appear to have had a benthic mode of life like their modern counterparts; myodocope ostracods, though known from the Ordovician, likely became pelagic only in the Silurian. As they are considered benthic, and possessed no pelagic larval stage, Ordovician podocope ostracods have been widely used as key biogeographical index species for much of the early Palaeozoic. A fundamental question in the oceanographic evolution of ostracods is: when did a psychrosphere evolve (a fauna inhabiting cool waters below the thermocline)? A psychrospheric ostracod fauna in the Ordovician would question some of their biogeographic utility, given that such taxa might have a much wider dispersal capability than more shallow shelf faunas. Here we describe a new ostracod fauna from a palaeotropical South China plate setting, preserved in Upper Ordovician mudstones and siltstones from northern Vietnam. The fauna contains taxa endemic to the South China palaeoplate, but also yields several taxa at the generic level that are known from European and North American Ordovician settings. We discuss whether these latter taxa might be indicative of a more widely dispersed deeper marine psychrospheric Ordovician ostracod fauna, and the implications this would have on traditional biogeographic models. We also discuss other possibilities for these apparently more cosmopolitan taxa, including homeomorphy, previously unknown palaeogeographical connections, and the possibility of pelagic podocope taxa

Exites in Cambrian arthropods and homology of arthropod limb branches

Abstract: The last common ancestor of all living arthropods had biramous postantennal appendages, with an endopodite and exopodite branching off the limb base. Morphological evidence for homology of these rami between crustaceans and chelicerates has, however, been challenged by data from clonal composition and from knockout of leg patterning genes. Cambrian arthropod fossils have been cited as providing support for competing hypotheses about biramy but have shed little light on additional lateral outgrowths, known as exites. Here we draw on microtomographic imaging of the Cambrian great-appendage arthropod Leanchoilia to reveal a previously undetected exite at the base of most appendages, composed of overlapping lamellae. A morphologically similar, and we infer homologous, exite is documented in the same position in members of the trilobite-allied Artiopoda. This early Cambrian exite morphology supplements an emerging picture from gene expression that exites may have a deeper origin in arthropod phylogeny than has been appreciated.Copyright © The Authors, 2021. This is an open access article, available to all readers online, published under a creative commons licensing (https://creativecommons.org/licenses/by/4.0/). The attached file is the published version of the article

Three new species of non-marine ostracods (Crustacea, Ostracoda) from small water bodies of northern China

Three new species, Pseudocandona cheni sp. nov., Cyclocypris pangi sp. nov., and Tonnacypris rectangularis sp. nov., collected from northern China, are described in this study. Pseudocandona cheni, of the compressa group, is difficult to be distinguished from other members of the same group by carapace morphology alone, but can be readily recognised by the structure of the hemipenis comprised of a long lobe a, distally inflated lobe h, and exteriorly pointed lobe b, as well as thick trunks of the male fifth limb endopodites. Cyclocypris pangi, despite its similarity in carapace morphology to its congeners, can be identified based on the morphology of the hemipenis, which bears a slender, slightly curved lobe h, and an S-shaped process accompanying lobe b, in addition to the rectangular trunk of the male fifth limb endopodite. On the other hand, Tonnacypris rectangularis, described on the basis of females only, can be distinguished from other Tonnacypris Diebel & Pietrzeniuk, 1975 representatives by its distinct sub-rectangular carapace alone. Other differences include the length of the swimming setae, the length of the distal claws on the second antennae, and the morphology of the pincer organ on the seventh limb. This study contributes to the poorly known extant non-marine ostracod fauna of Inner Mongolia and Beijing, and generally to the central-eastern Palaearctic region. In addition, the known distribution range of Tonnacypris is extended eastwardly by T. rectangularis. The valve-morphology data are useful for identifying fossil/sub-fossil representatives

Ilyocypris (Crustacea: Ostracoda) species in North East Asian rice fields description of one new species, and redescriptions of Ilyocypris dentifera Sars 1903 and Ilyocypris japonica Okubo, 1990

Smith, Robin James, Zhai, Dayou, Chang, Cheon Young (2019): Ilyocypris (Crustacea: Ostracoda) species in North East Asian rice fields description of one new species, and redescriptions of Ilyocypris dentifera Sars 1903 and Ilyocypris japonica Okubo, 1990. Zootaxa 4652 (1): 56-92, DOI: https://doi.org/10.11646/zootaxa.4652.1.

A review of rice field ostracods (Crustacea) with a checklist of species

Ostracods are very common in rice fields and they can have a significant influence on the rice field ecosystem. They can reach very high densities, often higher than other meiofauna, and their activities can have both positive and negative effects on rice harvests. They directly affect nutrient recycling through excretion, and indirectly by physically disturbing the soil and releasing minerals, thus improving rice growth. On the other hand, ostracods grazing on nitrogen-fixing cyanobacteria potentially reduce rice yields. Rice is a primary staple food for over half of the world’s population, and therefore ostracods can have a significant impact on human food supply. The origin of the rice field ostracod fauna is poorly known, but many rice field ostracods are considered invasive, especially in southern Europe, and from rice fields they have the potential to spread to surrounding natural habitats. Despite their invasive potential and ecological effects on the rice field ecosystem, very little is known about the diversity, ecology and impacts of rice field ostracods in many rice-producing countries. One hundred and ninety-two named ostracod species/subspecies have been reported from rice fields in 26 countries and states worldwide in the published literature; for over three-quarters of rice-producing countries, no data are readily available, and for most of the countries that have available data, diversity is clearly under-reported. Most species that have been documented from rice fields belong to the Cyprididae (78%), a family that makes up approximately 43% of the 2500+ non-marine ostracod species. A further six families (Candonidae, Darwinulidae, Entocytheridae, Ilyocyprididae, Limnocytheridae and Notodromadidae) form the remainder of rice field ostracods. Twenty-two percent of the species reported from rice fields are sexually reproducing, 18% have mixed reproduction, but are mostly asexual, and for 60% males are unknown, and are probably entirely asexually reproducing species. This review and checklist of rice field ostracods are presented to facilitate further research on this group in rice field habitats, research that is crucial for food security in many regions

Discovery of diverse Pectocaris species at the Cambrian series 2 Hongjingshao formation Xiazhuang section (Kunming, SW China) and its ecological, taphonomic, and biostratigraphic implications

Pectocaris species are intermediate- to large-sized Cambrian bivalved arthropods. Previous studies have documented Pectocaris exclusively from the Cambrian Series 2 Stage 3 Chengjiang biota in Yu’anshan Formation, Chiungchussu Stage in SW China. In this study, we report Pectocaris paraspatiosa sp. nov., and three other previously known Pectocaris from the Xiazhuang section in Kunming, which belongs to the Hongjingshao Formation and is a later phase within Cambrian Stage 3 than the Yu’anshan Formation. The new species can be distinguished from its congeners by the sparsely arranged endopodal endites and the morphologies of the abdomen, telson, and telson processes. We interpret P. paraspatiosa sp. nov. as a filter-feeder and a powerful swimmer adapted to shallow, agitated environments. Comparison among the Pectocaris species reinforces previous views that niche differentiation had been established among the congeneric species based on morphological differentiation. Our study shows the comprehensive occurrences of Pectocaris species outside the Chengjiang biota for the first time. With a review of the shared fossil taxa of Chengjiang and Xiaoshiba biotas, we identify a strong biological connection between the Yu’anshan and Hongjingshao Formations

CLUSTER ANALYSES OF OSTRACODA BASED ON DIMENSIONS OF BODY STRUCTURES: IMPLICATIONS FOR TAXONOMIC CLASSIFICATION

We measured selected podomeres, setae and claws in different ostracods and calculated the between-specimen morphological difference, which is expressed as a Canberra dissimilarity index. Our data indicate that morphological differences between ostracods increase with their taxonomic distance. Cluster analyses of ostracod specimens based on Canberra dissimilarity are able to discriminate different species and concur with existing classifications. We suggest that the dimensions of body structures are taxonomically valuable, and that ostracod species identification can be assisted based on the dimensional data of body structures. Species discrimination with such a method does not rely on explicit morphological hiatuses, such as the presence/absence of particular setae, but instead utilizes measurable morphological differences. Our numerical methods also show good potential for studying phenotypic diversity. Analyses on ostracod populations from isolated temporary pools and those from permanent but geographically distant habitats indicate that dispersal improbability is responsible for the observed morphological differentiation

Ilyocypris tibeta Peng & Zhai & Smith & Wang & Guo & Zhu 2021, n. sp.

<i>Ilyocypris tibeta</i> n. sp. <p>(Figs 18–22)</p> <p> ? 2009a <i>Ilyocypris</i> cf. <i>mongolica</i> Martens, 1991 —Wrozyna <i>et al.</i>: 8, 12, 14–17, plate 1: 1–8, figs 6–8.</p> <p> ? 2009b <i>Ilyocypris</i> cf. <i>mongolica</i> Martens, 1991 —Wrozyna <i>et al.</i>: 672, 673, plate 3: 7–11.</p> <p> ? 2013 <i>Ilyocypris</i> cf. <i>bradyi</i> Sars, 1890 —Zhang <i>et al</i>.: 40–43, 45, figs 2, 4, 6 (6–10).</p> <p> ? 2015a <i>Ilyocypris bradyi —</i> Song <i>et al</i>.: 587, 589–592, figs 1 (1&2), 3, 4 table 1.</p> <p> ? 2016 <i>Ilyocypris</i> sp.— Akita <i>et al</i>.: 27–30, 35, 37, 38, Figs 3 (16–18), 7, 9, 10, 12, tables 4, 5, 6.</p> <p> <b>Type locality.</b> A shallow pond in Rutog, Ngari, Tibet, China (32.93723ºN, 79.80317ºE, altitude 4390 m) (OS11-14, Table 1).</p> <p> <b>Type material.</b> Holotype: a dissected male (WOC39) from type locality (Table 1). Allotype: a dissected female (WOC38) from type locality. Paratypes: two dissected females (WOC40, WOC45) and two dissected males (WOC36, WOC37) (Table 1). Carapace of WOC40 damaged during dissection.</p> <p> <b>Other material examined.</b> One dissected, probably male specimen (WOC 35) with soft parts deteriorated (only Md coxa remained).</p> <p> <b>Derivation of name.</b> From name of the province where the specimens were collected.</p> <p> <b>Dimensions.</b> Male (LV, n = 3, WOC35 not included) length 0.77–0.89 mm, H/L ratio 0.52–0.54. Female (LV, n = 3) length 0.83–0.98 mm, H/L ratio 0.51–0.52.</p> <p> <b>Diagnosis.</b> Medium-sized <i>Ilyocypris</i>. Shell surface covered with small, rounded pits. In interior view, LV with numerous sparsely distributed marginal ripplets in distal area of posterior inner calcified lamella. A2 natatory setae extending to tips of terminal claws. Male L5 palps sub-equal, with sub-apical part of fingers slightly inflated. L6 penultimate segment divided. L7 penultimate segment with two setae (f and g) and apically bearing ca. four unequal length, hook-like structures. Inner lobe (b) of Hp elongate and slender, distally curved towards middle lobe. Middle lobe (h) with relatively narrow neck distally widening to sub-triangular distal part, distal inner corner sharply angled, outer edge angled to rounded. Outer lobe (a) short, distally evenly rounded and partly overlapping middle lobe. Copulatory process (st) slender, with pointed end. ZO with 16–17 internal rosettes of spines.</p> <p> <b>Description.</b> Carapace (Figs 18 & 19) sub-rectangular in lateral view. Dorsal margin nearly straight, only slightly concave at immediately posterior of mid-length. Highest point situated at 1/4 of valve length from anterior end. Anterior margin broadly rounded. Posterior margin slightly less arched than anterior margin. Ventral margin concave. Anterior sulcus situated at ca. 1/3 of valve length from anterior. Posterior sulcus situated at mid-length. Carapace sub-elliptical in dorsal view. Anterior end bluntly pointed, posterior end more rounded. Greatest width situated immediately behind posterior sulcus. Shell surface densely covered with small, shallow, rounded pits and two tubercles, one in postero-ventral area, and one in anterior dorsal margin, immediately anterior of sulcus. LV with more than 25 short marginal ripplets and number of striations in distal area of calcified inner lamella of posteroventral margin, and more than 15 short, weakly developed marginal ripplets and number of striations along calcified inner lamella of antero-ventral margin.</p> <p> A1 (Fig. 20A) with eight segments, first two of which fused, carrying one slightly setulous dorsal seta and two unequally long, smooth ventral setae. Third segment short and stout with one dorso-apical seta extending beyond fourth segment. Fourth segment sub-squarish with one fine dorso-apical seta extending to mid-length of seventh segment and one fine ventro-apical seta reaching mid-length of sixth segment. Fifth segment quadrate with two long dorso-apical setae extending beyond terminal segment with about half of length and two shorter, unequal ventroapical setae, one of which reaching beyond terminal segment, other one to terminal end of seventh segment. Sixth segment quadrate with two dorso-apical setae extending well beyond terminal segment and two ventro-apical setae, one of which extending beyond terminal segment with 1/5–1/4 of length, other one shorter and claw-like. Seventh segment sub-quadrate with five apical setae, shortest one (seta α) situated at exterior side of segment and extending almost to tip of aesthetasc y a. Eighth segment slightly elongate with three apical setae and aesthetasc y a situated at dorsal corner, shorter than claw-like seta at ventral corner. Two medial setae unequal in length.</p> <p>A2 (Fig. 20B, C) penultimate segment undivided in both sexes. First segment with one ventro-basal seta and two ventro-apical setae, shorter one of which sparsely plumose. Second segment with one ventro-apical seta extending to or slightly beyond mid-length of penultimate segment. Longest exopodal seta reaching distal end of third segment (first endopodal segment). Aesthetasc Y situated at mid-length of third segment, nearly reaching terminal end of third segment (first endopodal segment). Five long swimming setae on third segment reaching terminal claws or only slightly beyond, while sixth one only beyond middle of penultimate segment. Seta t1 extending somewhat beyond terminal segment. Setae t2 to t4 shorter, sub-equal in length, not reaching to end of segment. Seta z1 of male short, slightly claw-like. Setae z2 and z3 not transformed, extending to tips of claws. Female z-setae untransformed. G2 longest and most robust claw. G1 slightly shorter than G2. Male G3 very thin. Female G3 claw-like. Aesthetasc y2 very fine, reaching end of terminal segment. Male terminal segment with GM claw reaching tip of G2. Gm slightly shorter than GM. Aesthetasc part of y3 ca. 1/3 length of GM.</p> <p>Md and Mx (not shown) typical of genus, with few specific features. Vibratory plate of Mx with four robust reflexed setae.</p> <p>Male L5 palps (Fig. 20D, E) sub-equal, 2-segmented. Basal segment (i.e., trunk) elongate with two ventro-apical setae. Terminal segment (i.e., finger) narrower at middle, with one robust apical seta and one short dorso-subapical seta.</p> <p>L6 (Fig. 20F) five-segmented. Seta d1 short, d2 absent, e, f and g sub-equal in length. Seta h1 longer than h3. Claw h2 faintly serrated along distal part.</p> <p>L7 (Fig. 21A, B) with four segments. Seta d1 robust, somewhat claw-like. Setae e and f sub-equally long, shorter than g. Penultimate segment apically with group of small, hook-like structures, two large, one intermediate, and one small sized. Seta h1 shorter but more robust than h2. Seta h2 shorter than h3.</p> <p>Ur (Fig. 21C) ramus comparatively robust for genus. Sp situated at ca. 2/3 length of ramus, extending to base of claws. Distal half of ramus with fine, long pseudochaetae. Ga and Gp slightly longer than half of ramus length.</p> <p>Hp (Figs 21D & 22A) inner lobe (b) elongate and slender, distally curved towards middle lobe. Middle with relatively narrow neck distally widening to sub-triangular distal part, distal inner corner sharply angled, outer edge angled to rounded. Outer lobe (a) short, distally evenly rounded and partly overlapping middle lobe. Copulatory process (st) slender, with pointed end.</p> <p>ZO (Fig. 22D) with ca. 16–17 internal rosettes of spines, both ends inflated but proximal end much larger.</p> <p>Female reproductive organ (Fig. 21E) with one elongate, ovate lobe.</p> <p> <b>Remarks.</b> The five-segmented L6, inflated proximal end of the ZO, and ‘blade-type’ copulatory process of the Hp indicates that <i>Ilyocypris tibeta</i> <b>n. sp.</b> belongs to the <i>Ilyocypris japonica</i> Okubo, 1990 group of Asian species as defined by Smith <i>et al.</i> (2019). The new species is particularly similar to <i>Ilyocypris japonica</i>, <i>Ilyocypris mongolica</i> Martens, 1991 and <i>Ilyocypris innermongolica</i> Zhai & Xiao, 2013 in terms of carapace, L7 (with apical hook-like structures on the third segment) and Hp morphologies (Okubo 1990; Martens 1991; Zhai & Xiao 2013; Smith <i>et al.</i> 2019). Differences include the following: The A2 natatory setae of <i>Ilyocypris tibeta</i> <b>n. sp.</b> reach to about the tips of the terminal claws, while these are much longer in the other three species extending significantly beyond the terminal claws by almost 1/2 of their lengths. The setae on the three distal-most segments of the A1 of <i>Ilyocypris tibeta</i> <b>n. sp.</b> are also much shorter than those of <i>I. japonica</i>, <i>I. mongolica</i> and <i>I. innermongolica</i> (Smith <i>et al.</i> 2019; D. Zhai, unpublished data; Zhai & Xiao 2013). The copulatory process (st) of the Hp of <i>Ilyocypris tibeta</i> <b>n. sp.</b> is distally more slender than those of both <i>I. mongolica</i> and <i>I. japonica</i>, and most similar to <i>I. innermongolica.</i> The outer lobe (a) is small, narrow and evenly rounded in <i>Ilyocypris tibeta</i> <b>n. sp.</b>, while more angular in <i>I. innermongolica</i> and wider in both <i>I. japonica</i> and <i>I. mongolica.</i> The Hp middle lobe (h) of <i>Ilyocypris tibeta</i> <b>n. sp.</b> is similar to those of <i>I. japonica</i> and <i>I. mongolica</i>, although this lobe is slightly more rounded on the outer distal edge and less inflated in <i>Ilyocypris tibeta</i> <b>n. sp.</b> The Hp middle lobe of <i>I. innermongolica</i> is significantly different to <i>Ilyocypris tibeta</i> <b>n. sp.</b> and the other two species, being distally much less inflated. The ZO of all the male <i>I. mongolica</i> specimens (Zhai & Zhao 2014) have 13–14 rows of spines; while the number is larger in <i>Ilyocypris tibeta</i> <b>n. sp.</b> (16–17), similar to <i>I. japonica</i> (15–17) and <i>I. innermongolica</i> (17–21). The hook-like structures of the L7 are well-developed in <i>Ilyocypris tibeta</i> <b>n. sp.</b>, similar to those of <i>I. mongolica,</i> and more pronounced than those of <i>I. japonica</i> and <i>I. innermongolica</i>.</p> <p> The type locality of <i>Ilyocypris tibeta</i> <b>n. sp.</b> is a small, shallow pond with a soft, yellowish substrate, a few macrophytes and animal footprints around the edges. It was also found in two other places, a pond with a soft mud substrate, and in the riffle zone of a slowly flowing river (Table 1). Altitudes of these sites ranges from 4325 to 4593 m.</p> <p> Several reports of <i>Ilyocypris</i> species from the Tibetan Plateau figure valves that are very similar to <i>Ilyocypris tibeta</i> <b>n. sp.</b> (e.g. Wrozyna <i>et al</i>. 2009a; 2009b; Zhang <i>et al</i>. 2013; Song <i>et al</i>. 2015a; Akita <i>et al</i>. 2016; see synonymy list above). The carapaces of <i>Ilyocypris</i> species generally show a strong resemblance to each other, but can also show high amounts of intraspecific variation (e.g. tubercle development, and lateral view of the carapace), complicating identification on valves alone (e.g. Mazzini <i>et al.</i> 2014; Smith <i>et al.</i> 2019). The most reliable characters for identification are found on the appendages and male sexual organs. Thus it is not possible to determine if valves previously figured are definitely conspecific with <i>Ilyocypris tibeta</i> <b>n. sp.</b>, and highlights the importance of soft part examination when possible.</p> <p>The scattered known localities of living (and possible conspecific sub-fossil) material of this species suggests that it could be widespread at least in the southern and western parts of Tibet, and it probably favours shallow, muddy habitats.</p>Published as part of <i>Peng, Ping, Zhai, Dayou, Smith, Robin J., Wang, Qianwei, Guo, Yun & Zhu, Liping, 2021, On some modern Ostracoda (Crustacea) from the Tibetan Plateau in SW China with descriptions of three new species, pp. 501-542 in Zootaxa 4942 (4)</i> on pages 520-526, DOI: 10.11646/zootaxa.4942.4.2, <a href="http://zenodo.org/record/4612066">http://zenodo.org/record/4612066</a&gt

Fabaeformiscandona monticulus Peng & Zhai & Smith & Wang & Guo & Zhu 2021, n. sp.

<i>Fabaeformiscandona monticulus</i> n. sp. <p>(Figs 23–26)</p> <p> <b>Type locality.</b> A pond in Kangding, Garze, Sichuan, China (30.07745ºN, 101.79605ºE, altitude 4207 m) (OS09-1, Table 1).</p> <p> <b>Type material.</b> Holotype: one dissected male (WOC14) from type locality (Table 1). Allotype: one dissected female (WOC15) from type locality. Paratype: one dissected male (WOC17) from type locality (Table 1).</p> <p> <b>Derivation of name.</b> From the Latin <i>monticulus</i>, the diminutive form of mountain, and referring to the large and triangular a lobe of the Hp, which is reminiscent of a mountain peak. The name is a noun in apposition.</p> <p> <b>Dimensions.</b> Male (LV, n = 2) length 0.82–0.84 mm, H/L ratio 0.55. Female (LV, n = 1) length 0.79 mm, H/L ratio 0.54.</p> <p> <b>Description of male.</b> Carapace (Fig. 23) sub-reniform in lateral view. Dorsal margin nearly evenly arched, with highest point at about 1/3 of length from posterior end. Both anterior and posterior ends broadly rounded, maximum curvature of anterior margin in antero-ventral area. Ventral margin significantly concave. Valve surface sparsely covered with fine setae. In dorsal view, carapace moderately compressed, with anterior end more pointed than posterior end. In interior view, antero-ventral area of calcified inner lamella unusually wide in LV of both sexes, with inner margin straight or even slightly curved inwards.</p> <p> A1 (Fig. 24A, B) with eight segments, first two fused forming large base, carrying two dorsal setae and two unequally long ventro-apical setae. Third segment short and rectangular, with one dorso-apical seta. Fourth segment short, with one dorso-apical seta. Fifth segment sub-quadrate, with one dorso-apical seta extending beyond terminal segment with about half of length, and one short ventro-apical seta. Sixth segment sub-quadrate, with two long dorso-apical setae and one short ventro-apical seta. Seventh segment elongate, with two long dorso-apical setae and two short ventro-apical setae. Eighth segment slender, with three unequally long setae and dorso-apically situated aesthetasc y a.</p> <p>A2 (Fig. 24C, I, J) first segment (coxa) with one long posterior seta and two unequal ventral setae, shorter one of which robust and plumose. Second segment (basis) robust, with one slender ventro-apical seta extending beyond terminal of next segment. Exopod plate small, carrying three progressively long setae, longest of which extending to about end of first endopodal segment. Endopod with penultimate segment sub-divided. Third segment (first endopodal segment) robust, with slender aesthetasc Y situated behind mid-length, extending to about ventro-apical end of this segment, and with two sub-equal ventro-apical setae extending slightly beyond terminal segment. Fourth segment sub-rectangular, ventrally carrying small aesthetasc y1, distally carrying three t-setae, two of which transformed into male bristles, and one dorso-apical seta. Fifth segment quadrate, ventro-apically with small aesthetasc y2. z1 and z2 transformed into robust claws, with z2 longer and thicker than z1. z3 small, claw-like. G2 longest claw, two times length of G1. G3 slender. Terminal segment small. Gm extending to about tip of G2. Gm less than half length of GM. Aesthetasc part of y3 slender.</p> <p>Md (Fig. 24D, E) coxa elongate, interiorly bearing ca. eight slender teeth. One stout seta present on antero-subapical part of coxa. Palp four-segmented. First segment robust, with four ventral setae, including smooth unnamed seta, plumose seta S1, short plumose seta S2, and thin, smooth seta α. Second segment short, with two dorso-apical setae and ventro-apically, group of four smooth setae, shorter accompanying seta and tiny seta β. Third segment with three slender dorso-subapical setae, two stiff intero-apical setae (including seta γ) and one long and one tiny ventro-apical setae. Fourth segment slightly elongate, with two more robust setae/claws and two slender setae.</p> <p>First segment of Mx palp (Fig. 24F) with four dorso-apical setae. Second segment elongate, with two more robust claws/setae and two smaller setae. Tooth bristles on distal gnathobasic endite smooth. Two robust setae present on proximal side of proximal endite.</p> <p>L5 (Fig. 24G, H) gnathobasic endite with ca. 14 apical setae, two of which bifurcate distally (one observed in left L5 of holotype). Right L5 palp progressively slenderer distally, bearing two sub-apical setae. Right L5 palp with blunt dorsal bump on median part of trunk, finger slender and elongate, one of two sub-apical setae claw-like.</p> <p>L6 (Fig. 25A) with five segments. First segment elongate and less sclerotized, carrying intermediately long seta d1. Second segment long, with seta e reaching distal part of third segment. Third segment and fourth segment subequally long, each with one distal seta. Fifth segment elongate and trapezoidal, with seta h1 longer than h3. Claw h2 much longer than total length of three terminal segments, slightly serrated at sub-apical part.</p> <p>L7 (Fig. 25B) generally well sclerotized, with four segments, penultimate segment undivided. First segment with setae d1 and dp. Second segment without seta. Third segment distally with curved seta g. Fourth segment elongate and rectangular, with setae h1, h2 and h3 progressively longer. Seta h3 only faintly curved at sub-apical part.</p> <p>Ur (Fig. 25C, D) ramus stout and robust, basal part swollen. Sa slim. Ga sub-equally long to Gp but slightly more robust, both serrated. Sp situated at ca. 1/4 length of ramus from distal end, longer than Sa. Ur attachment medially with two branches and proximally with tri-ramous branch.</p> <p>Hp (Fig. 25E) with large, triangular outer lobe a, small, triangular median lobe h, and interiorly, pointed, setalike structure. M-process only slightly enlarged distally.</p> <p>ZO (Fig. 26) with 5+2 rosettes each bearing numerous spines.</p> <p> <b>Additional description of female.</b> Carapace (Fig. 23B & G) dorsal margin nearly straight and sloping anteriorly. Posterior end narrowly rounded (not broadly rounded as in male), with maximum curvature at postero-ventral area, postero-dorsal margin gently curving up to hinge. Anterior margin similar to that of male. Calcified inner lamella wide, especially in antero-ventral area; here inner edge of calcified inner lamella almost straight. Posterior part of both valves with polygonal pattern (Fig. 23G).</p> <p>Distal morphology of A2 (Fig. 24I). t-setae subequally long but with t2 slightly longer, extending beyond terminal segment with half of length. z-setae extending slightly beyond terminal segment. G1 and G3 longest claws. G2 about half length of G1, slender. GM extending to or slightly beyond G1. Gm about 3/4 length of GM.</p> <p>GL (Fig. 25C) very small and narrowly rounded.</p> <p> <b>Remarks.</b> The smooth γ seta on the Md and the relatively laterally compressed carapace indicates that this species belongs to the genus <i>Fabaeformiscandona.</i> Of the 55 species in this genus, most have carapaces noticeably different in shape to those of <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b>, but three do show a resemblance in the lateral view of the female: <i>Fabaeformiscandona balatonica</i> (Daday, 1894), <i>Fabaeformiscandona levanderi</i> (Hirschmann, 1912) and <i>Fabaeformiscandona danielopoli</i> Yin & Martens, 1997. The wide calcified inner lamella in the anteroventral area of the female valves of <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> is a feature not seen to such an extent in the other species; it is also wide here in <i>F. levanderi</i> but not as wide as in <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> and it does not have an almost straight edge in <i>F. levanderi</i>. Males of all three species are sufficiently different in carapace and Hp morphologies to clearly distinguish them from <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> In particular the lobe a of the Hp of <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> is very large and triangular, much larger than the a lobes of the other species, and the posterior margin of the male more evenly rounded.</p> <p> The arrangement of 4+1+β setae on the inner edge of the second Md palp segment indicates that <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> belongs to the <i>acuminata</i> -group of <i>Fabaeformiscandona,</i> the same as <i>F. levanderi</i> and <i>F. danielopoli,</i> but different to <i>F. balatonica</i> (<i>balatonica</i> -group).</p> <p> The polygonal pattern on the posterior part of the female carapace is a feature shared by some other Candonidae, such as <i>Fabaeformiscandona myllaina</i> Smith & Kamiya, 2007, <i>Neglecandona angulata</i> (G.W. Müller, 1900), <i>Candona muelleri jakutica</i> Pietrzeniuk, 1977, and <i>Candona xizangensis</i> Huang, 1982 (in Huang <i>et al.</i> 1982).</p> <p> Although in a different genus, <i>Candona xizangensis</i>, also reported from the Tibetan Plateau, shows some similarity to <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> in overall carapace shape and the presence of a polygonal pattern in the female carapace (see figs in Akita <i>et al</i>. 2016). The female of <i>C. xizangensis</i> is more tightly curved posteriorly and the postero-dorsal margin longer than those in <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> The male carapaces of both species are similar, but the male of <i>C. xizangensis</i> is slightly more rounded posteriorly, and has a small convex expansion in the mouth region (absent in <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b>). The appendages of <i>C. xizangensis</i> remain unknown, hindering further comparisons and confirmation of its generic status.</p> <p> <i>Fabaeformiscandona monticulus</i> <b>n. sp.</b> was collected once during this study, from a pond with sparse aquatic plants near the shore at an altitude of 4207 m (Table 1).</p>Published as part of <i>Peng, Ping, Zhai, Dayou, Smith, Robin J., Wang, Qianwei, Guo, Yun & Zhu, Liping, 2021, On some modern Ostracoda (Crustacea) from the Tibetan Plateau in SW China with descriptions of three new species, pp. 501-542 in Zootaxa 4942 (4)</i> on pages 526-531, DOI: 10.11646/zootaxa.4942.4.2, <a href="http://zenodo.org/record/4612066">http://zenodo.org/record/4612066</a&gt

Potamocypris variegata

<i>Potamocypris variegata</i> (Brady & Norman, 1889) <p>(Figs 16, 17)</p> <p> <i>Cypridopsis variegata</i> Brady & Norman, 1889</p> <p> <b>Material examined.</b> One dissected female (WOC 57) (Table 1).</p> <p> <b>Dimensions.</b> Female (LV, n = 1) length 0.60 mm, height 0.35 mm, H/L ratio 0.58.</p> <p> <b>Description of female.</b> Carapace (Fig. 16) sub-triangle in lateral view. Dorsal margin strongly arched with highest point near mid-length. Anterior margin broadly rounded with maximum curvature at antero-ventral area. Postero-dorsal angle prominent with central posterior margin slightly curved and running down to tightly curved postero-ventral margin. Ventral margin concave. Valve surface densely pitted and covered with fine setae; pits slightly smaller towards periphery of valves compared with central area. In interior view, selvage displaced inwards. Anterior inner list running along medial part of calcified inner lamella. Posterior inner list situated very close to inner margin of calcified inner lamella.</p> <p> A1 (Fig. 17A) with eight segments. First two segments fused into elongate base, supporting one short dorsal seta and two long ventral setae. Third segment sub-trapezoidal, with one short dorsal seta. Fourth segment slightly elongate, with one dorso-apical seta extending well beyond end of fifth segment, and one tiny ventro-apical seta not reaching to end of fifth segment. Fifth segment stout, with two unequal dorso-apical setae, and two very short, unequal ventro-apical setae. Sixth segment slightly elongate, with two very long, dorso-apical setae of sub-equal length, and two ventro-apical setae of different lengths, one of which claw-like. Seventh segment with four apical setae reaching tips of longest apical seta of sixth segment. Seta α not observed. Eighth segment slender, with slender aesthetasc y a, about twice as long as eighth segment, ventro-apical seta, slightly longer than y a, and two medial, much longer setae.</p> <p>A2 (Fig. 17B) basal segment with one slender latero-posterior seta and two unequal ventro-apical setae. Second segment with one long ventro-apical seta. Longest exopodal seta with very fine distal part, reaching mid-length of penultimate segment or beyond. Aesthetasc Y situated proximal to mid-point of first endopodal segment, slender, 2- or 3-segmented, reaching beyond mid-length of segment. Natatory setae extending beyond terminal claws with ca. half of length. Sixth seta reaching to about end of terminal segment. Ventro-apical seta of this segment reaching to about tip of aesthetasc y3. Penultimate segment with two medio-dorsal setae of slightly unequal length. t-setae unequal in length, with t2 and t3 longest, extending beyond terminal segment with more than half length. Aesthetasc y1 situated proximally of t setae, extending slightly beyond penultimate segment. z-setae unequal, with z3 longest and z2 shortest. G claws serrated. G1 longest claw, G2 most robust and most serrated. GM slender and finely serrated at distal part, only slightly longer than G2. Gm 3/5 length of GM. Aesthetasc part of y3 extending slightly beyond mid-length of Gm.</p> <p>Md palp (Fig. 17C) 4-segmented. S1 and S2 robust, covered with long pseudochaetae. Accompanying seta slender and smooth. Seta α not observed. Setal group of second segment with three sub-equally long, slightly plumose setae extending to about mid-length of terminal claws. Accompanying seta shorter, plumose. Seta β short, stout, plumose. Second segment with three slender antero-apical setae one of which plumose. Third segment with about nine apical setae: Four antero-apical, slender, smooth, unequally long setae, one latero-exterior, plumose seta extending beyond mid-length of terminal claws, two slender, smooth latero-interior setae, and about two slender, smooth postero-apical setae. Fine pseudochaetae present at antero-medial part of penultimate segment. Terminal segment with two long, robust claws, one shorter, robust claw, and one short, slender seta. Vibratory plate with two tiny setae and four long rays.</p> <p>First segment of Mx palp (Fig. 17D) with one short latero-interior seta and five anterior setae. Second segment of Mx palp spatulate, with four claws. Two largest tooth bristles of third endite lobe slightly unequal in length and smooth.</p> <p>Setae a of L5 (Fig. 17E) protopod tiny. Setae b, c, and d absent. Palp poorly sclerotized, with very long h2 and unequally long h1 and h3. Vibratory plate with two unequal setae.</p> <p>L6 (Fig. 17F) with four endopodal segments. Seta d1 absent. Seta d2 well developed. Setae e, f, g, and h1 subequally long. Claw h2 robust, serrated. Seta h3 tiny.</p> <p>L7 (Fig. 17G) with three segments. Seta d1 slightly shorter than d2. Seta dp comparatively short, only slightly longer than d2. Seta e short, not extending to mid-length of terminal segment. Seta f very short. Pincer organ small. Seta h3 slightly S-shaped.</p> <p>Ur (Fig. 17H) with slightly swollen base, carrying long flagelliform structure and short sub-apical seta.</p> <p> <b>Remarks.</b> The one specimen of this species recovered during this study is tentatively assigned to the species <i>Potamocypris variegata</i> based on the following characters: pitted carapace, long swimming setae, four setae on the terminal segment of the maxillula palp, and two rays on the maxillula branchial plate (Fig. 17). The LV is noticeably more elongate (height / length = 0.56) compared to some other figured specimens of <i>P. variegata</i> (height / length = 0.64, Meisch 1985; 0.60, Fuhrmann 2012), and is similar to <i>Potamocypris smaragdina</i> (Vávra, 1891). However, <i>P. smaragdina</i> has only one ray on the maxillula branchial plate (Meisch 1985). <i>Potamocypris variegata</i> has been previously reported from North America and western parts of Eurasia, including western Russia and Iran (see review in Meisch 1985; 2000). The records of this species from Tibet in this study and those from Beijing (Zhai <i>et al.</i> 2017, specimens not illustrated) are therefore much further east than previous records. The solitary specimen herein was collected from a small, turbid pond at an altitude of 3075 m.</p>Published as part of <i>Peng, Ping, Zhai, Dayou, Smith, Robin J., Wang, Qianwei, Guo, Yun & Zhu, Liping, 2021, On some modern Ostracoda (Crustacea) from the Tibetan Plateau in SW China with descriptions of three new species, pp. 501-542 in Zootaxa 4942 (4)</i> on pages 518-520, DOI: 10.11646/zootaxa.4942.4.2, <a href="http://zenodo.org/record/4612066">http://zenodo.org/record/4612066</a&gt