Gerhard Becker

Aurikirkbya wordensis (hamilton): ein vermutlich filtrierender palaeocopider ostracode

The valves ofAurikirkbya wordensis (Hamilton, 1942) from the Upper Permian, Word Formation of W Texas (USA), show a crenulated contact groove in the larger valve and smooth contact list in the smaller one. The right valve is usually the larger but occasionally inversion of valves take place. The contact elements of the free margin of valves are discussed in terms of functional morphology. In addition, the muscle-scar areas and the carapace outline have also been regarded. Based on the new discoveries, it is suggested thatA. wordensis was a nectobenthonic filter-feeder. The evidence from the valve interiors is not consistent with a platycopine position for the kirkbyacean taxa.KurzfassungAurikirkbya wordensis (Hamilton 1942) aus der oberpermischen Word-Formation von W-Texas (USA) hat eine krenulierte Kontaktfurche in der größeren Klappe und eine glatte Kontaktleiste an der kleineren Klappe. Gewöhnlich ist die rechte Klappe die größere, aber auch Klappen-Inversion kommt vor. Die Kontakt-Strukturen des freien Klappenrandes werden funktionsmorphologisch interpretiert. Einbezogen in die Diskussion werden auch die Narbenfelder und die Gehäuseform. Geurteilt nach den neuen Beobachtungen handelt es sich beiA. wordensis vermutlich um einen nekto-benthontischen Filtrierer. Auch nach den Innenmerkmalen sind die Kirkbyacea Ulrich & Bassler 1906 keine Platycopina.

Ventrale Inzisuren bei paläozoischen Podocopida (Ostracoda) und ihre funktionelle Deutung

Ventral incisures, till now not really functionally interpreted, are described in three genera of the Family Pachydomellidae (Podocopida, Ostracoda). The functional meaning of these structures (respiration and locomotion when the carapace is closed, special behavior of reproduction or brood care, etc.) and resulting taxonomic conclusions are discussed in detail. All specimens were found in basinal faciès.KurzfassungVom ventralen Klappenrand werden bei drei Gattungen der Familie Pachydomellidae (Podocopida, Ostracoda) bislang kaum funktionell interpretierte Inzisuren beschrieben. Die funktionelle Bedeutung dieser Strukturen (Atmung bzw. Fortbewegung bei geschlossenem Gehäuse, besondere Verhaltensweisen bei der Fortpflanzung oder Brutpflege, usf.) sowie die sich ergebenden taxonomischen Folgerungen werden ausführlich diskutiert. Alle Stücke entstammen der Beckenfazies.

Devonian ostracods from western Canada — palaeozoogeographic implications

The stratigraphical significance, evolutionary pathways and distribution patterns of Devonian (with emphasis on Middle Devonian) ostracods occurring in western Canada are reviewed. The overall faunal appearance is Devonian in aspect. Typical Eifelian-Givetian markers are ascertainable at the generic level, and occasionally resemble known species. Recognised genera mostly comprise cosmopolitan forms indicating (close or loose) faunal connections to both north and south, but also representing either Old World or true New World forms. A “core group”, however, shows a particular bauplan giving a unique aspect, mainly discrete palaeocopine genera, provided with particular extradomiciliar dimorphic features and considered to be endemic for the Middle Devonian of western Canada. In terms of palaeozoogeography, faunal relationships inside Canada and to Devonian occurrences overseas are demonstrated. Connections between sedimentary transgressive-regressive and evolutionary cycles are demonstrated in terms of event-stratigraphy. Against the background of plate tectonic analyses, assumed migration paths are considered, probably northward via the Uralian Sea to Siberia, but certainly and on a larger scale southward across the Rheic Ocean to North Africa (southwestern Morocco, central Sahara) and Europe (Eifel region, eastern Thuringia, Holy Cross Mountains). As a result, the faunal relationship to the adjacent Great Lakes region appears to be much closer than originally predicted, while only loose contacts are traceable to the North American Midcontinent region. The North African and central European relationships are revealed by few, but conspicuous genera and, to some extent, this may be true of the Russian Platform and Bashkiria.

Eine eigentümliche schalen-struktur bei bewegtwasser-arten vonPolyzygia Gürich (Ostracoda, Metacopina)

A peculiar extramarginal, internal structure observed in two species of the metacopine ostracod genusPolyzygia GüRICH 1896 is described and discussed in terms of functional morphology (questionably muscle attachment points).Both Polyzygia species are from a high-energy, nearshore shallow-water environment. New isP. symmetrica triebeli n.subsp. from the uppermost Santa Lucía Formation (topmost Upper Emsian) of the Cantabrian Mountains, northern Spain.KurzfassungVon zwei Arten der metacopinen Ostracoden-GattungPolyzygia GüRICH 1896 wird eine eigentümliche, extramarginale Innenstruktur beschrieben und funktionsmorpnologisch interpretiert (fragliche Muskel-Ansatzstellen). Beide Polyzygia-Arten entstammen hoch-energetischer, küstennaher Flachwasser-Fazies. Neu istP. symmetrica triebeli n. subsp. aus der höchsten Santa Lucía-Formation (Top Oberemsium) des südlichen Kantabrischen Gebirges (N-Spanien).

Extra-lobal and complex dimorphic features in Middle Devonian palaeocopine ostracods

With respect to Middle Devonian ostracods from western Canada, special cases of palaeocopine extradomiciliar dimorphism are discussed, as in the opinion of many workers are unusual for younger hollinoideans and, in particular, primitiopsoideans. Although the general view that velar dimorphism is the main characteristic of Mid Palaeozoic Palaeocopina is basically not wrong, dimorphic histial structures, even though less conspicuous in aspect, have been recognised in some Mid-Devonian hollinoideans, specifically hollinids and ctenoloculinids. This is now also proven to be true of distinct hollinellids and, by the way, discrete primitiopsids, while distinguishing between narrow-based projections (ridges, flanges, spines) and broad-based protrusions (e.g. lobes). Whereas the former may occur in velar as well as histial situations, lobal features are especially found in the histial position. Special attention is paid to false primitiopsids, being (with some caution) grouped in the Hollinoidea (Family unknown). Essentially, three genera are new or redefined (former left under open nomenclature): Gen. aff. Abditoloculina: multilobate in aspect, lobal (histial) dimorphic; Gen. aff. Gravia: coalesced velar dimorphic; Bisphenella: histial dimorphic. With respect to the hold discussion about ostracod phylogeny, the updated standard classification scheme is given, as applied to Palaeozoic, non-myodocopine ostracods. Reduction of dimorphism in palaeocopines is considered to be an apomorphic character, lack of dimorphism assumed to indicate asexual reproduction. At the same time, a plea is made in favour of reviving Treatise revision.

Nomenclatural state of selected ostracod taxa (an antedated note)

In the course of studies on ostracod material stored with the collections of the University of Saskatoon, some taxa need formal nomenclatural status. The necessary data required by the Code [ICZN 1999] are given below. For further and more detailed information, seeBecker &Braun (in prepn).

Schalenmerkmale verkieselter Ostracoden: Sind die ordovizischen Duplikaturen nur Artefakte oder eher evolutionäre Vorversuche?

KurzfassungDie post-silurische podocopine Duplikatur (verkalkte Innenlamelle) wird besprochen, deren Phylogenie sowie ökologische Bedeutung dargestellt. Unter Einbeziehung entsprechender detaillierter Vorarbeiten wird das Phänomen ordovizischer, nachGramm „mesostener“ Duplikaturen diskutiert. Bei den an diagenetisch veränderten (sekundär verkieselten) und/oder präparativ umgewandelten (flourisierten) Materialien (Flinte) beobachteten Randstrukturen handelt es sich entweder um Zufälligkeiten (Artefakte) oder um optische Täuschungen. DieGramm’schen Vorstellungen „mesoplater“ Duplikaturen, d.h. randlicher Verdickungen bei palaeocopinen Ostracoden, decken sich indessen mitBeckers Modell der evolutionären Vorversuche, wonach zu Zeiten von erhöhtem phylogenetischen Stress das Art-Niveau das bevorzugte evolutionäre Experimentier-Feld (konkret zur Optimierung des freien Rands) ist.AbstractThe post-Silurian, podocopine duplicature (calcified inner lamella) is reviewed, its phylogeny and ecological importance are shown. Taking the relevant literature into account, the phenomenon ofGramm’s Ordovician, “mesostene duplicature” is discussed. Features of the free margin shown in some Ordovician, podocopine species which were obtained from silicified (or silicified and calcium fluorite converted) shells, are either artefacts or results of optical illusions.Gramm’s conception of the “mesoplatic duplicature”, i.a. the marginal thickening in palaeocopine species, however, corresponds toBecker’s model of evolutionary dead-ends, after which the species level is determined to be the favoured experimental stage of the evolution (in concrete terms, the development of the free margin) in times of increased phylogenetic stress.