The earliest ostracods: The geological evidence

Palaeobiodiversity and Palaeoenvironments 04/2008; 88(1):11-21. DOI: 10.1007/BF03043974


The oldest assumed ostracods appear in the fossil record from the TremadocianPaltodus deltifer conodont Biozone. Although geographically widespread these early ostracods have no obvious Cambrian antecedents. Their first
appearance at ca. 485 Ma contrasts with molecular evidence that suggests a much earlier (latest Proterozoic or Cambrian) origin
for ostracods. Some Cambrian bivalved arthropods such asAltajanella andVojbokalina, conventionally referred to the Bradoriida, have carapace morphologies that resemble Ordovician palaeocopid ostracods, though
such a relationship is unproven without soft part anatomy. Evidence from preserved soft anatomy demonstrates that Bradoriida,
such asKunmingella, and Phosphatocopida, essentially the Cambrian ‘ostracod’ record of traditional usage, belong outside the Eucrustacea. Early
Ordovician ostracods appeared first in shallow marine, oxygenated environments on shelf margins, in a similar setting to other
elements of the ‘Paleozoic fauna’. Their biodiversity was low (3 named genera and ca. 12 species), though some taxa such asNanopsis andEopilla achieved widespread dispersal between major Ordovician palaeocontinents. As bradoriids were largely extinct by the Late Cambrian,
ostracods do not appear to have directly competed with them for shallow marine environments. The rapid colonisation of these
settings by ostracods may have been facilitated by the available ecospace vacated by Bradoriida.

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    • "Bradoriida, Phosphatocopida and Leperditicopida, are all characterised by having a calcified, bivalved carapace, but their systematic position remains unclear. The oldest carapaces of ostracods (Palaeocopida) are found in the early Ordovician (Williams et al. 2008). Early myodocopes appeared in the Silurian, but because of their poorly mineralised valves the early fossil record of this group is sparse (Siveter 2008). "
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    ABSTRACT: In marine environments Ostracoda and Foraminifera have been very successful invaders. During the Phanerozoic they colonised the majority of shallow, marginal to deep water, fully marine habitats. Both groups had developed physiological adaptations which pre-adapted them to the invasion of new marine habitats. They adopted a broad range of feeding strategies and reproduction modes. The production of resting stages and brood care may also have contributed to them being efficient invaders. They are also both highly tolerant to variations in salinity. The first invasions of non-marine habitats by ostracods appear to have taken place at the turn of the Devonian and Carboniferous. It is estimated that there had been between 9 and 12 independent invasions of fresh waters by the ostracods. In contrast Foraminifera are typically marine organisms, and only a few species of agglutinated and organic-walled Foraminifera are to be found in brackish and freshwater environments. Agglutinated species build their test using ambient components but are not commonly regarded as calcifying organisms. An impact of salinity on foraminiferal calcification has been observed in several studies. It seems that Foraminifera are incapable of constructing a fully calcified test in low salinity regimes; they use sea water not only as a source of ions to construct shell, but also as a biomineralisation solution. Thus, the success of ostracods in invading freshwater habitats can be attributed to their development of a more effective mechanism of calcification in low mineralisation waters. The core question of this study is to examine possible causes for the differences in success between the two taxa.
    Full-text · Chapter · Feb 2015
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    • "This information was transmitted to ostracodologists during various ISO and EOM meetings (Müller, 1979; Maas and Waloszek, 2005; Siveter, 2008). The revolutionary approach of Müller allowed recovery of phosphatised fossil ostracods with limbs from Late Palaeozoic strata, Devonian (Olempska et al., 2012) and post-Palaeozoic deposits, (Bate, 1972; Smith, 2000; Williams et al., 2008; Matzke-Karasz et al., 2013). Here again IRGO-members (palaeontologists and neoontologists) cooperated in networks for description and interpretation of their material. "
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    ABSTRACT: The 1st International Symposium on Ostracoda (ISO) was held in Naples (1963). The philosophy behind this symposium and the logical outcome of what is now known as the International Research Group on Ostracoda (IRGO) is here reviewed, namely ostracodology over the last 50 years is sociologically analysed. Three different and important historic moments for the scientific achievements of this domain are recognised. The first one, between about 1963-1983, is related to applied research for the oil industry as well as to the great interest in the better description of the marine environment by both zoologists and palaeontologists. Another important aspect during this period was the work by researchers dealing with Palaeozoic ostracods, who had their own discussion group, IRGPO. Gradually, the merger of this latter group with those dealing with post-Palaeozoic ostracods at various meetings improved communication between the two groups of specialists. A second period was approximately delineated between 1983 and 2003. During this time-slice, more emphasis was addressed to environmental research with topics such as the study of global events and long-term climate change. Ostracodologists profited also from the research “politics” within national and international programmes. Large international research teams emerged using new research methods. During the third period (2003-2013), communication and collaborative research reached a global dimension. Amongst the topics of research we cite the reconstruction of palaeoclimate using transfer functions, the building of large datasets of ostracod distributions for regional and intercontinental studies, and the implementation of actions that should lead to taxonomic harmonisation. Projects within which molecular biological techniques are routinely used, combined with sophisticated morphological information, expanded now in their importance. The documentation of the ostracod description improved through new techniques to visualise morphological details, which stimulated also communication between ostracodologists. Efforts of making available ostracod information through newsletters and electronic media are evoked.
    Full-text · Article · Aug 2014 · Palaeogeography Palaeoclimatology Palaeoecology
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    • "Historically, phosphatocopines were considered members of the Ostracoda due to the similarity of their carapaces (M€ uller, 1964), particularly before exceptionally preserved (limb-bearing) phosphatocopines were discovered in the Orsten (Maas et al., 2003; Williams et al., 2008; Hou et al., 2010). Once limbs were described, an important issue became apparent: the phosphatocopine maxillule and maxilla remain undifferentiated from the trunk limbs, unlike those in most other pancrustaceans (Maas et al., 2003). "
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    ABSTRACT: The study of ontogeny as an integral part of understanding the pattern of evolution dates back over 200 years, but only recently have ontogenetic data been explicitly incorporated into phylogenetic analyses. Pancrustaceans undergo radical ontogenetic changes. The spectacular upper Cambrian ‘Orsten’ fauna preserves phosphatized fossil larvae, including putative crown-group pancrustaceans with amazingly complete developmental sequences. The putative presence and nature of adult stages remains a source of debate, causing spurious placements in a traditional morphological analysis. We introduce a new coding method where each semaphoront (discrete larval or adult stage) is considered an OTU. This avoids a priori assumptions of heterochrony. Characters and their states are defined to identify changes in morphology throughout ontogeny. Phylogenetic analyses of semaphoronts produced relationships of each Orsten fossil to the crown-group clade expected from morphology shared with extant larvae. Bredocaris is a member of the stem lineage of Thecostraca or (Thecostraca + Copepoda), and Yicaris and Rehbachiella are likely members of the stem lineage of Cephalocarida. These placements rely directly on comparisons between extant and fossil larval character states. The position of Phosphatocopina remains unresolved. This method may have broader applications to other phylogenetic problems which may rely on ontogenetically variable homology statements.
    Full-text · Article · Jul 2014 · Cladistics
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