Tonnacypris glacialis (Ostracoda, Cyprididae): taxonomic position, (palaeo-) ecology, and zoogeography

Abstract. The freshwater ostracod Tonnacypris glacialis (Sars, 1890) is reported from the European Pleistocene for the first time. The historical allocation of the species is discussed, and the species composition and characteristics of Tonnacypris Diebel & Pietrzeniuk (1975) and its phylozoogeography are considered. The significance of T. glacialis is reviewed, particularly from the viewpoint of the possible implications of parthenogenesis (and occasional-male production) for the Quaternary history of the genus, and for the use of the species in palaeoenvironmental reconstruction. It is suggested that the Pleistocene fossil occurrence of T. glacialis in modern temperature latitudes is a robust indicator of mean summer temperatures of 6°C.     

The muscle scar in cavellinids and its importance for the phylogeny of platycope ostracodes

The adductor muscle scars of cavellinids from the Visean (in one case from the Upper Devonian) of the European part of the RSFSR have revealed a significant diversity in their morphology. Aggregate, multiserial with up to five series, bi- to triserial and nearly biserial muscle scars existed simultaneously. The verticaliserial muscle scars were initiated by a biserial larval group which in the course of evolution may have passed, due to neoteny, into the adult stage. Together with Cytherella sp. from Syria, the new data show that the genus Cytherella appeared not in Triassic nor Jurassic time, hut originated among cavellinids possibly in the Early Carboniferous. A new genus is Borovitchella , with the type species B. egorovi n. sp.     

Microreticulation in Cambrian Ostracoda and its relation to similar patterns in tertiary and Recent Ostracoda

The Cambrian bradoriid ? Parahoulongdongella sp. is shown to have a microreticulate (2nd order) surface sculpture. A possible organic sheet‐like origin is proposed for this reticulation. The relation between this second order pattern and those found in tertiary to Recent Ostracoda is discussed.     

An ostracod-based calibration function for electrical conductivity reconstruction in lacustrine environments in Patagonia,Southern South America

In the Patagonian region (∼37–56°S) E of the Andes, the salinity and solute composition of lakes is strongly related to their location along the marked W-E decreasing precipitation gradient that is one of the main climatic features of the area. A calibration function (n = 34) based on 12 ostracod species (Ostracoda, Crustacea) was developed by WA-PLS to quantitatively reconstruct electrical conductivity (EC) values as a salinity proxy. The selected one component model had a r² = 0.74 and RMSEP and maximum bias equal to 16% and 31% of the sampled range, respectively, comparable to other published ostracod-based calibration functions. This model was applied to the ostracod record of the closed lake Laguna Cháltel (49°58′S, 71°07′W), comprising seven species and dominated by two species of the genus Limnocythere. In order to evaluate the calibration function’s robustness, the obtained EC values were compared with qualitative lake level and salinity variations inferred through a multiproxy hydrological reconstruction of the lake. Both reconstructions show good overall agreement, with reconstructed EC values in the oligo-mesohaline range (average: 11 060 ± 680 μS/cm) between 4570 and 3190 cal BP, corresponding to the ephemeral and shallow lake phases, and a marked decrease in EC concurrent with a lake level rise, reaching an average EC of 1140 ± 90 μS/cm during the deep lake phase (1720 cal BP to present). The variability in the reconstructed EC values for the ephemeral lake phase showed some inconsistency with the expected trend, which was attributed to time-averaging effects; for its part, the pace of the decrease in EC during the medium-depth phase (3190–1720 cal BP) differed from the expected, which could be due to autigenic effects (redissolution of salts) at the onset of this phase. This comparison not only lends support to the adequacy of the calibration function, but also suggests that its application in the context of a multiproxy study can greatly contribute to distinguish between autigenic and climatic-related controls of paleosalinity in closed lakes, allowing performing more accurate paleoenvironmental inferences on the basis of paleohydrological reconstructions.     

Ilyocypris bradyi的轮廓分析

本文试图通过对若尔盖盆地晚新生代非海相介形类化石Ilyocypris bradyi(Sars)的轮廓分析来介绍几何形态测量法在介形类化石的形态分析中的应用。分析对比后发现,虽然Ilyocypris bradyi(Sars)居群内的个体在形态上存在或多或少的差异,但这些差异之间存在连续过渡的关系,并未出现明显的分异,说明此种的种内变异是连续的。     

菲律宾海北部底质沉积中的深海介形类

对琉球群岛东侧的菲律宾海北部海区(27.0°-30.0°N,129.5°-135.5°E)水深1 666 m至6 616 m的123个表层沉积物样品进行了定量微体古生物学研究.仅在38个样品中发现介形类,主要分布在4 000 m以浅水深区.初步鉴定有21属35种,其中Krithe在样品中的出现率和丰度最高,其次常见的还...     

河南西峡盆地晚白垩世含恐龙蛋地层中的介形类

河南西峡盆地含恐龙蛋地层高沟组、马家村组和寺沟组共发现介形类13属(亚属)20种,其中高沟组和寺沟组的介形类为首次报道.文章重点讨论了介形类Talicyridea动物群,其中Talicypridea,Altanicypris,Ruficypris和Lunicypris属的地质历程均限于晚白垩世.依据Talicyprid...     

A high-precision global biostratigraphy of myodocope ostracods for the Silurian upper Wenlock Series and Ludlow Series

The wide, trans-oceanic geographical distribution of myodocope ostracods during the Silurian (especially during the Ludlow and Pridoli epochs), and their widespread preservation in rocks of that age, permits the establishment of a transcontinental biostratigraphy of comparable resolution to coeval graptolite/chitinozoan/conodont biozones. Seven myodocope biozones, extending from the Homerian Stage, upper Wenlock Series Cyrtograptus lundgreni graptolite biozone to the middle part of the Ludfordian Stage of the Ludlow Series, enable a time-resolution for each biozone of circa 1 million years. These biozones can provide high-resolution correlation across Europe into Arctic Russia and Central Asia. There is also the potential for a myodocope biostratigraphy applicable from the uppermost Silurian (Pridoli) to the Carboniferous.     

Site prioritisation for the protection of rare subterranean species – the cases of two ostracods from south-western France

1. Delineation of protected areas for rare subterranean species is a key problem for groundwater biodiversity conservation, because of practical difficulties in implementation. Criteria for site selection are presented that are derived from studies on two remarkable Ostracoda, Dolekiella europaea Gidó, Artheau, Colin, Danielopol & Marmonier (Limnocytheridae) and Vestalenula carveli Artheau (Darwinulidae) discovered in south-western France.
2. Arguments for natural heritage value and protection of subterranean species are proposed and illustrated by using information on these two ostracod species. The proposed criteria are: (i) local and/or regional endemism; (ii) known occurrence of the species at a few localities only; (iii) representativeness for ancient phylogenetic lineages with wider geographical distributions in the past; and (iv) suitability for scientific study because of unique morphological or biological traits.
3. It is also proposed to prioritise the protection of subsurface sites using the following criteria: (i) type locality for newly described species; (ii) presence of other rare stygobiotic taxa; and (iii) high population densities of the primary target species.
4. Development and implementation of protection strategies at local scale are likely to benefit from collaboration between scientists, policy makers and stakeholders. The measures taken should complement existing national and/or international attempts at large-scale protection of groundwater biodiversity.     

Extinction pattern of marine Ostracoda across the Pliensbachian-Toarcian boundary in the Cordillera Ibérica, NE Spain: Causes and consequences

This paper discusses the extinction pattern of the Pliensbachian-Toarcian boundary (PTB) ostracod assemblages at the Almonacid de la Cuba section (Cordillera Ibérica, NE Spain), which has been recently proposed as auxiliary boundary stratotype for the PTB. The ostracod record shows that the main Early Jurassic ostracod extinction event occurred not at the end of the Pliensbachian, but near the top of the Mirabile ammonite Subzone, Tenuicostatum ammonite Zone (Early Toarcian). On the basis of the evaluation of PTB ostracod record, a new causal explanation for the Early Toarcian ostracod turnover is proposed. This paper suggests that a reorganization of surface and deep-water circulations caused by the opening of the Hispanic Corridor could have generated a mild cooling episode, finally affecting the survival of healdioid ostracods.