Ostracod Genus Research Articles

10.1007/s11506-008-1005-z

Stages in evolution of the Early Jurassic to Aalenian foraminifers and ostracodes are established based on the analyzed diversity dynamics of respective microfauna associations. Evolution of foraminifers is divided in two, the Hettangian-initial early Toarcian and the late early Toarcian-Aalenian stages, while the identical first stage in evolution of ostracodes has been followed by the late early Toarcian-Callovian stage. During the Jurassic, periodic migrations of foraminiferal and ostracod genera and species, which were interrelated with large transgressions and climatic changes, took place in the initial late and mid-late Pliensbachian, initial early Toarcian, and the late Toarcian-early Aalenian. Being isolated to the maximum extent in the second half of the late Aalenian, the Arctic basin lost connections with seas of northwestern Europe. The Early Jurassic to Aalenian biogeography of the Arctic basin is established based on the results of cluster analysis (group average link method, Jaccard coefficient, presence or absence of foraminifers and ostracodes genera) with due account for preceding and subsequent formation history of microbenthos structure in biochores. The distinguished biochores are ranked as realms and provinces of foraminifers and ostracodes. As is established, contours of the realms and provinces populated by different groups of microbenthos did not coincide and changed with time. Ecotones between the realms (e.g., the North Sea province) changed their localitization to be a part of the Arctic or Boreal Atlantic realms in different epochs. The Early-Middle Jurassic sedimentary successions of the Arctic basins reveal several levels of sharp taxonomic changes in composition of microbenthos under influence of the first-order abiotic factors.

<i>Oculobairdoppilata</i> gen. nov. (Ostracoda, Bairdiidae): a new genus from the Paleocene of Tunisia

Abstract. A new marine ostracod genus, Oculobairdoppilata, belonging to the family Bairdiidae, is described from Paleocene deposits in Tunisia. Its main characteristic is the occurrence of an eye tubercle in the anterodorsal part of the valves. Internally, small denticles and corresponding sockets are present at the terminal parts of the dorsal edge of the right and left valves, respectively. It is the first bairdiid with an external eye structure to be described, although the existence of such a genus was predicted previously.

MORPHOLOGY, ONTOGENY, AND PHYLOGENETICS OF THE GENUS POSEIDONAMICUS (OSTRACODA: THAEROCYTHERINAE)

Abstract The ostracode genus Poseidonamicus has been widespread and abundant in deep-sea sediments since the Eocene. Despite its prominent role in a number of evolutionary studies, species identification in this genus is often difficult and phylogenetic relationships among its species are not well understood. Here I present the findings from a comprehensive study of this genus with the purpose of discovering novel phylogenetic characters and clarifying species relationships. I briefly describe the adult carapace and trace some of the major morphological changes that occur over the last several instars. I focus particular attention on the arrangement of fossae in the reticulate mesh; these features have been shown in other ostracodes to correspond to underlying epidermal cells. I describe the development of fossae in the region posterior to the adductor muscle scars, and hypothesize a sequence of specific cell divisions to account for the addition of fossae over ontogeny. Phylogenetic characters were deriv...

EVOLUTIONARY DIVERGENCE IN DIRECTIONS OF HIGH PHENOTYPIC VARIANCE IN THE OSTRACODE GENUS POSEIDONAMICUS

Trait variation and covariation are understood to influence the response of populations to natural selection on generational time scales, but their role, if any, in shaping long-term macroevolutionary divergence is still unclear. The present study uses the rich fossil record of the ostracode genus Poseidonamicus to reconstruct in great detail the evolutionary history of a set of landmark-based morphometric characters. This reconstruction included two kinds of evolutionary inferences: ancestor-descendant transitions among populations repeatedly sampled at the same location and divergence between lineages measured as independent contrasts on a phylogeny. This reconstructed history was then used to test if evolutionary changes were concentrated in directions (traits or combinations of traits) with high phenotypic variance. Two different statistics of association between evolution and variation tested the null hypothesis that evolutionary changes occur in random directions with respect to trait variability. The first of these measured the similarity between the directions of evolutionary change and the axis of maximum variance, and the second measured the degree to which evolutionary changes were concentrated in directions of high phenotypic variation. Randomization tests indicated that both kinds of evolutionary inferences (ancestor-descendant and phylogenetic contrasts) occurred preferentially in directions of high phenotypic variance (and close to the axis of maximal variation), suggesting that within-population variation can structure long-term divergence. This effect decayed after a few million years, but at least for one metric, never disappeared completely. These results are consistent with Schluter's genetic constraints model in which evolutionary trajectories on adaptive landscapes are deflected by variation within and covariation among traits.

On a new species and genus in the Cypridini (Crustacea, Ostracoda, Cyprididae) from South Africa, with a phylogenetic analysis of the tribe and a discussion on the genus concept in this group

The present paper describes Mnementh brennei n. sp. n. gen., a new non‐marine ostracod species and genus from temporary wetlands in the Western Cape Province (South Africa). The new genus is the fifth in the subfamily Cypridinae and a phylogenetic analysis using morphological characters demonstrates that it is most closely related to its putative sister taxon Pseudocypris. Apart from this cluster, the phylogenies are not at all robust and this is to all probability due to the incongruent (mosaic) evolution amongst the different characters in valve and soft part modules. Implications of such incongruent evolution of characters for the concept of genera in this group are discussed.

Geographical review of the ostracod genus Vestalenula (Darwinulidae) and a new subterranean species from southern France

A new species of Vestalenula is described. Vestalenula carveli, sp. nov. was found in the interstitial habitat of rivers during the PASCALIS European program when sampling three sites on the Aude River and Tech River basins (Roussillon region, southern France). With its large caudal brooding cavity, the presence of an external keel on the right valve and an internal tooth on the left valve, V. carveli is a typical representative of the genus. This new record brings the worldwide number of Vestalenula species to 24. Vestalenula representatives are known from the Lower Miocene to the present. A review of present-day knowledge of the geographical distribution of the genus and a cladistic analysis are presented in order to assess the biogeography of this genus and the importance of the discovery of a new subterranean species in southern France. The geographical review of the genus showed that most species of Vestalenula occur in subtropical regions. However, V. cylindrica, V. boteai and V. danielopoli lived, or are living, in the Palearctic. Vestalenula pagliolii occurs in both hemispheres. Many of the Recent species live in semiterrestrial and/or interstitial habitats and occur in geographically restricted areas. The distribution of the species of Vestalenula suggests independent colonisation of the subterranean environment by several species; this hypothesis is supported by the cladistic analysis.

Size, shape and development time are plastic traits in salt lake ostracods of the Mytilocypris mytiloides (Ostracoda:Cyprididae) species complex

The taxonomy of the ostracod genus Mytilocypris is based in part on characters of shell morphology. Specifically, M. minuta, M. mytiloides and M. tasmanica chapmani lack distinctive internal characters and are differentiated largely on size and shape of the shell. The three taxa also differ in the salinity of the habitats they occupy. A field study showed a steady decrease in adult size, spanning the size range of all three taxa, over the course of a season within single lakes, in association with changing salinity and other environmental variables. The present study was conducted to investigate whether each phenotype could be produced under laboratory conditions of variable salinity. Offspring of the three parental phenotypes were raised under high and low salinity. Regardless of parental type, offspring grew more quickly, but reached a smaller size at high salinity, and grew more slowly, but reached a larger size at low salinity. The shape of the shell was found to have a significant size component. Plasticity in size and shape suggests these are unreliable characters for taxonomy. Accelerated development may be an adaptation to living in an ephemeral habitat, with salinity being one of the cues Mytilocypris uses to gauge habitat duration.

The Mesozoic ostracod genus Arculicythere Grékoff: further evidence for the southern Gondwana seaway

This paper demonstrates that Arculicythere Grékoff is a widespread taxon in the uppermost Upper Jurassic and Lower Cretaceous of Gondwana. It occurs in Madagascar, India, Israel, South Africa, the Falklands Plateau, Argentina and Australia. The earliest record is from the Upper Tithonian of Madagascar but the most profuse occurrences are in the Albian, when the genus was very widespread around Gondwana. Its distribution seems to be associated with a major southern Gondwana seaway, and the genus provides additional proof of the existence of this corridor. Unlike another endemic gondwanine genus, Majungaella Grékoff, which ranged from earlier in the Jurassic but extended into the Neogene in the Antarctic, or Rostrocytheridea Dingle that survived into the Campanian of the Antarctic, Arculicythere seems to have become extinct in the Albian.

The ostracod genus <i>Paijenborchella</i> and some of its species in the Early Tertiary of Pakistan

Abstract. Six species of the genus Paijenborchella are described. Five of these species are new, namely Paijenborchella (Eopaijenborchella) angulosa, P. (E.) viriosa, P. (E.) ventricaudata, P. (E.) noar and P. (Paijenborchella) inponticulata. The stratigraphic distribution of these species in the Early Tertiary of Pakistan is given; they range from the Lower Eocene to the Upper Eocene in the Sulaiman Range and one species occurs in the Upper Paleocene of the Sor Range.

Appendage Homologies and the First Record of Eyes in Platycopid Ostracods, with the Description of a New Species of Keijcyoidea (Crustacea: Ostracoda) from Japan

A median nauplius eye is reported for the first time in a platycopid ostracod, a group hitherto considered to be blind. A new species of the platycopid ostracod genus Keijcyoidea is described from coastal rocky marine habitats on the Pacific coast of Japan. Observations of living specimens in the laboratory show that it is capable of burrowing to a depth of several millimeters in sandy sediment, using the first two head appendages (antennulae and antennae) and the furca. Females brooded a maximum of five eggs in the posterior brood space of the carapace. The homologies and phylogenetic implications of the trunk segmentation and limbs are discussed, paying particular attention to the sexually dimorphic fifth and sixth limbs; the copulatory appendages of both sexes are interpreted as being attached to trunk segments T6–T7 (counting from the posterior; T1 = posteriormost segment).

Velatomorpha, a new healdioidean ostracode genus from the early Pennsylvanian Joggins Formation, Nova Scotia, Canada

Internal features of the smooth, traditionally nonmarine ostracode Carbonita altilis (Jones and Kirkby 1879) are re- ported in detail for the first time. Based on the 26-28 stigmata within the adductor muscle scar (AMS) field, a ridge and groove contact margin, and an adont hinge, we establish the new genus Velatomorpha. Included within this genus are taxa previously assigned to Carbonita, Healdia?, and Microcheilinella. The characters diagnosed for this new genus warrant placement in the Suborder Metacopina, Superfamily Healdioidea. The associated biota and sedimentary facies indicate that Velatomorpha lived in a mixed freshwater-marine (brackish) estuarine environment. The implication of our taxonomic revision for Velatomorpha altilis underscores the necessity to care- fully evaluate the internal features of smooth, podocopid and metacopine ostracodes reported from Paleozoic strata before making taxo- nomic assignments and generalized paleoecological inferences.

Ostracods from the yola arm, Upper Benue Trough, Nigeria

A total of nine genera of ostracods from the Yola Arm in the north-east of Nigeria are described. The various species, though from outcrop sections, supplement the list from the Upper Benue Trough already reported from Ashaka quarry and borehole (BH 2340) of the Gongila and Pindiga Formations respectively. The species described belong to six families namely; Brachicytheridae, Bythocytheridae, Cyprididae, Trachyleberididae, Cytherideidae and Cytherellidae . Some of the species are evidence of faunal dispersion during the Mid-Cretaceous marine transgression of the North and West African basins. Keywords : biostratigraphy, systematics, ostracod, taxonomy Global Journal of Geological Sciences Vol. 3(2) 2005: 179-185

First occurrence of the genus <i>Sclerocypris</i> Sars, 1924 (Ostracoda) in the ?Pleistocene of Western Europe (Portugal)

Abstract. The Recent distribution of the freshwater ostracod genus Sclerocypris Sars, 1924 (type species Sclerocypris clavularis Sars, 1924; synonyms Bharatcypris Battish, 1978 and Candonopsis Sars, 1894 pro parte), subfamily Megalocypridinae Rome, 1965, is restricted to Africa and India (Martens, 1986; Martens & Coomans, 1990).Recovery of fossils of Sclerocypris are not frequent and are restricted to Plio-Quaternary deposits of Kenya, with Sclerocypris clavularis Sars, 1924 from Lakes Turkana and Bogoria (Carbonel & Peypouquet, 1979; Carbonel et al., 1983, 1987; Cohen et al., 1983) and Sclerocypris jenkinae Klie, 1933 from Lakes Elmenteita and Naivasha (Lindroth, 1953; Cohen & Nielsen, 1986) and the Pliocene basal member of the Omo Series, Lake Turkana (Peypouquet et al., 1979). Sclerocypris bicornis (G. W. Müller, 1900) has been recorded (identified as Chlamydotheca sp.) in the Pleistocene of Egypt (Boukhari & Guernet, 1985).Recent field work in Algarve, southern Portugal (Cabral et al., 2003, 2004, 2005), recorded the presence of Sclerocypris. It was represented by numerous juvenile specimens of a species related closely to the Recent species Sclerocypris bicornis in a probable Pleistocene lacustrine ostracod assemblage at Bolqueime associated with other Cypididae, Candonidae, Darwinulidae, Limnocytheridae and Cypridopsidae. The instars are characterized by the presence of long spines on the margins, as is common in many species of this genus (Martens, 1986, 1991), such as Sclerocypris tuberculata (Methuen, 1910), Sclerocypris venusta (Vavra, 1897) [illustrated in Martens, 1986] and Sclerocypris clavularis Sars, 1924 (Pl. 1, fig. 2). They also possess three large conical tubercles not present on adults, an important . . .

Mid-Pliocene deep-sea bottom-water temperatures based on ostracode Mg/Ca ratios

We studied magnesium:calcium (Mg/Ca) ratios in shells of the deep-sea ostracode genus Krithe from a short interval in the middle Pliocene between 3.29 and 2.97 Ma using deep-sea drilling sites in the North and South Atlantic in order to estimate bottom water temperatures (BWT) during a period of climatic warmth. Results from DSDP and ODP Sites 552A, 610A, 607, 658A, 659A, 661A and 704 for the period Ma reveal both depth and latitudinal gradients of mean Mg/Ca values. Shallower sites (552A, 610A and 607) have higher mean Mg/Ca ratios (10.3, 9.7, 10.1 mmol/mol) than deeper sites (661A, 6.3 mmol/mol), and high latitude North Atlantic sites (552A, 610A, 607) have higher Mg/Ca ratios than low latitude (658A: 9.8 mmol/mol, 659A: 7.7 mmol/mol, 661A: 6.3 mmol/mol) and Southern Ocean (704: 8.0 mmol/mol) sites. Converting Mg/Ca ratios into estimated temperatures using the calibration of Dwyer et al. (1995) [Dwyer, G.S., Cronin, T.M., Baker, P.A., Raymo, M.E., Buzas, J.S., Corrège, T., 1995. North Atlantic deepwater temperature change during late Pliocene and late Quaternary climatic cycles. Science 270, 1347–1351] suggests that mean middle Pliocene bottom water temperatures at the study sites in the deep Atlantic were about the same as modern temperatures. However, brief pulses of elevated BWT occurred several times between 3.29 and 2.97 Ma in both the North and South Atlantic Ocean suggesting short-term changes in deep ocean circulation.

The affinities of the ostracod genus Cypridea Bosquet, 1852, and its allies, with consideration of implications for the phylogeny of nonmarine cypridoidean ostracods

The nonmarine ostracod genus Cypridea s.l., characterized by an antero-ventral “beak” (rostrum and alveolus) in both valves, achieved high diversity and global distribution in the Early Cretaceous but declined in the Late Cretaceous and became extinct during the Paleogene. Although it clearly belongs to the Superfamily Cypridoidea (Order Podocopida, Suborder Cypridocopina), the precise affinities of Cypridea s.l. have been controversial, different authors variously suggesting it to be most closely related to the cypridoidean families Ilyocyprididae, Cyprididae or Notodromadidae. Since Cypridea s.l. was responsible for much of the explosive radiation of nonmarine cypridoidean taxa during the Mesozoic, a clear understanding of its affinities is crucial to the elucidation of nonmarine ostracod phylogeny. We evaluate some of the key morphological features of cypridoidean carapaces as indicators of phylogenetic affinity, paying special attention to adductor muscle scar patterns and the structure of the anterior marginal zone. The morphology of Cypridea s.l. is compared with certain cypridoideans that bear similar beak-like or lip-like antero-ventral marginal structures, notably genera of the Family Cyprididae such as Bennelongia, Chlamydotheca, Cypris and Talicypridea, and consider whether these similarities represent close phylogenetic relationships or homeomorphy.

Sur l'origine du genre Microceratina Swanson, 1980 (Ostracoda, Eucytherurinae) et sa présence téthysienne dès le Jurassique supérieur

The discovery in the uppermost Jurassic of Lebanon of a species of the ostracod genus Microceratina Swanson, 1980 (Eucytherurinae), of which the oldest known species was until now of Maastrichtian age, confirms the Tethyan origin of this genus. Two new species are created: Microceratina bhannesensis nov. sp. from the Upper Jurassic (Kimmeridgian) of Lebanon, and Microceratina azazoulensis nov. sp. from the Cenomanian of Morocco. The genera Chapmanicytherura Weaver, 1982 and Erratacytheridea Herrig et al., 1997, are considered as probable junior synonyms of Microceratina. An exhaustive bibliographical analysis allowed to identifying several other Cretaceous species susceptible to be assigned to the genus Microceratina.

<i>Ankumia</i> van Veen, 1932 retained and not replaced by the junior taxon <i>Platella</i> Coryell & Fields, 1937 (Ostracoda, Platycopina, Cytherelloidea)

Abstract. Recently, the monotypic ostracod genus Ankumia van Veen, 1932 was abandoned as nomen dubium by Jones (2003, p. 85) in favour of Platella Coryell & Fields, 1937 and a new combination was proposed for the type species of Ankumia, i.e. Platella bosqueti (van Veen, 1932). However, Ankumia bosqueti from the Maastrichtian of The Netherlands was introduced as an available taxon and, as documented by Jones (2003), the specific name is valid for recognizing the species in which ‘pathological individuals with retained moults’ occur. Therefore, there is no reason to treat Ankumia as nomen dubium. Yet, although there is no doubt about the cytherellid relationship of the species, two taxonomical questions still remain.(1) Do pathological individuals of cytherellids justify specific and/or generic ranking? Certainly they do not, and demonstration of a corresponding ‘normal’ species (including ‘pathological individuals’) among the associated cytherellids is wanting. On the other hand, if these pathological individuals can be proven as representing a discrete pathological genus, Ankumia remains as a valid genus to characterize the available species name bosqueti.(2) Why should Ankumia be abandoned in favour of Platella? When van den Bold (1967, pp. 306, 308) compared Coryell & Fields’ original Gatún ostracod fauna with his own collection from the Neogene Gatún Formation in the Panama Canal Zone, he recognized the type species, Platella gatunensis, as a small-sized cytherellid moult. Over the years about a dozen small- and normal-sized cytherellid species from all over the world have been assigned to Platella, ignoring the questionable taxonomic . . .

Evolutionary trends and biostratigraphic significance of the ostracode genus Stigmatocythere in the Cenozoic succession of India

Stigmatocythere Siddiqui is an important ostracode genus and occurs profoundly in sediments of marginal marine to shallow inner neritic origin in the Cenozoic succession of western India. Its species have short stratigraphic ranges and wide geographic distribution, which makes them good markers and helps in finer subdivision of the Cenozoic strata. Nineteen species including one new species Stigmatocythere (Bhatiacythere) khoslai have been recognized from Lower Eocene to Middle Miocene sediments of western India. Of these, Stigmatocythere (S.) obliqua Siddiqui is restricted to the upper part of the Lower Eocene. Stigmatocythere (S.) lumaria Siddiqui morphotype A and S. (S.) portentum Siddiqui are restricted to the upper part of the Middle Eocene (Bartonian) and Stigmatocythere (S.) lumaria Siddiqui morphotype B to the Upper Eocene. Stigmatocythere (Bhatiacythere) khariensis Khosla and Pant is restricted to the Lower Oligocene, while S. (S.) bermotiensis Khosla and Pant ranges from Lower Oligocene to Upper Oligocene and Stigmatocythere (S.) reticulata Khosla and Pant from Oligocene to Lower Miocene (middle part of Aquitanian). Stigmatocythere (S.) khoslai sp. nov. ranges from Aquitanian to lowermost Burdigalian, S. (S.) chaasraensis Guha ranges from uppermost Lower Oligocene to Lower Miocene (middle Burdigalian), and S. (B.) reversa Khosla, S. (S.) quilonensis Khosla and Nagori range from Aquitanian to middle Burdigalian, while S. (S.) latebrosa Lyubimova and Guha, S. (B.) spinosa Khosla and Nagori and S. (B.) interrupta Khosla and Nagori are confined to the Lower Miocene (lower to middle Burdigalian). S. (B.) rete Khosla and Nagori and S. (B.) arcuata Khosla and Nagori are confined to middle Burdigalian and S. (S.) multicostata Khosla and Nagori ranges from middle to upper Burdigalian. S. (S.) colini Bhandari is confined to the lowermost Middle Miocene and S. (S.) keeni Bhandari ranges up to the top of the Middle Miocene. The above species of the genus Stigmatocythere belong to five evolutionary lineages. They are: 1- Stigmatocythere (S.) obliqua – S. (S.) portentum, 2- S. (S.) reticulata – S. (S.) latebrosa – S. (S.) multicostata – S. (S.) keeni, 3- S. (S.) bermotiensis – S. (S.) quilonensis – S. (S.) chaasraensis, 4- S. (B.) khariensis – S. (B.) khoslai – S. (B.) reversa – S. (B.) rete – S. (B.) arcuata, 5- Stigmatocythere (B.) reversa – S. (B.) interrupta. These lineages are briefly discussed here.

On the origin and evolution of a new anchialine stygobitic <i>Microceratina</i> species (Crustacea, Ostracoda) from Christmas Island (Indian Ocean)

Abstract. Marine species of the ostracod genus Microceratina Swanson (Cytheruridae, Eucytherurinae) were until now known only from their hard parts, the valves and carapaces, as no living animals have been described. Here we report the first living population, from a tropical anchialine cave. The description of the limbs and hard parts of this new taxon, M. martensi sp. nov., enhances our understanding of the origin and evolution of the cave-dwelling Microceratina – the new species and M. pseudoamfibola (Barbeito-Gonzalez) from an anchialine cave in Southern Italy – and clarifies their affinities with other Eucytherurinae species. Microceratina is known from both Recent and fossil species (Quaternary, Tertiary and Late Cretaceous) from shelf and deep-sea habitats and/or sedimentary facies, located in the Pacific Ocean (along the Australian and New Zealand coasts), the Mediterranean (Greece and Italy), the North Atlantic (British Isles) and the Baltic Sea (Rügen Island). This suggests that the Microceratina group spread through the expanding Tethys Ocean. The morphological traits of the two cave-dwelling species reflect their ecological conditions. Cave-dwelling Microceratina species appear to have originated from epigean shallow water species predisposed to colonize subterranean habitats.

A Review of the Mesozoic Ostracod Genus Lophocythere and Its Close Allies

The progonocytherid cytheracean ostracod genus Lophocythere and its immediate allies in the Jurassic are reviewed. All known species of 16 genera are considered. We consider that only eight of these genera (Acanthocythere, Afrocytheridea, Aulacocythere, Fuhrbergiella, Lophocythere, Neurocythere, Terquemula and Trichordis) remain valid; the eight rejected genera are Crucicythere, Cuvillierella, Dhrumaella, Infacythere, Nophrecythere, Paralophocythere, Pokornya and Tropacythere.