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Amber inclusions of fully aquatic animals are rare, most of them isolated specimens of water-bound insect larvae. In contrast, we here describe an ample, speciose fauna of 262 fully aquatic individuals of Ostracoda (Crustacea) from Mexican amber of Early Miocene age. This fauna was trapped whilst under water swimming around trunks of resin-producing trees in a brackish lagoon. Ostracod crustaceans are typically around a millimeter in length, and are known for their mostly well-calcified bivalved carapaces that account for their unparalleled fossil record in arthropods. However, in the Chiapas amber we found representatives of the tribe Thalassocypridini, which are characterised by lightly calcified carapaces and therefore lack a substantial fossil record. Embedded in amber, this 'drawback' becomes a clear benefit because the unobstructed view onto the appendages otherwise hidden in the carapace allowed us to identify nine ostracod species, six of them new to science. The exceptional number of individuals permitted insights into population composition, reproduction, taphonomy and into micro-environmental parameters of the amber's place of formation. Based on ecological data available for Recent Thalassocypridini species, we posit that this tribe reached a peak radiation in open lagoonal settings during the Miocene, and shifted towards anchialine environments by the Recent. http://zoobank.org/lsid:zoobank.org:pub:3C93A06B-F86B-404F-985D-139897F97EF3 [ABSTRACT FROM AUTHOR]

In an extensive ostracod assemblage recovered from the Bitesantennary Site, an Early Miocene (23–16 Ma) cave deposit within the Riversleigh World Heritage Area in north-west Queensland, Australia, 26 specimens were found to have soft part preservation. This is the first known example of soft part preservation in ostracods that were living in a palaeo-subterranean habitat. These exceptionally preserved specimens represent three new species, described herein:Heterocypris collarissp. nov.,Candonocypris fimibolussp. nov. andNewnhamia mckenzianasp. nov. The appendages of a few of the specimens showed a highly detailed mode of preservation, typical of mineralization by Ca-phosphate (apatite). This preservation can be ascribed to an elevated supply of phosphate from guano derived from bats living in the cave. Two specimens feature an extraordinary mineral surface precipitation, partly embedding surface structures, such as fines setules on setae. After the decay or mechanical loss of the latter, only sharp imprints are left. Another specimen is characterized by a differential preservation of the ovaries and hepatopancreases, visible from outside the carapace as differences in coloration, a first in ostracod fossil preservation. [ABSTRACT FROM PUBLISHER]

In her publication on a Holocene sedimentary succession of the Eastern Adriatic coast, here in the same volume, the author V. Hajek-Tadesse describes a new ostracod (Crustacea) species. She assigns it to the previously monospecific genus Juxilyocypris Kempf, 2011, which is now holding the two fossil species J. schwarzbachi (Kempf, 1967) and J. kempfi Hajek-Tadesse, 2018. These three taxa, and their taxonomic proximity give a perfect memento of three palaeontologists of the Cologne University, whose lives and achievements were similarly interwoven. [ABSTRACT FROM AUTHOR]

Fossil Cyclocypris diebeli Absolon, 1973 from Europe are redescribed, utilizing material with chitinous preservation of the appendages and carapace. These are compared with living C. diebeli from Kushiro Marsh, Hokkaido, Japan, representing the first living population of this species ever found. The fossil material is associated with strongly calcareous sediments, whereas the living material is found in weakly calcareous to acidic waters. Reasons for the different ecological requirements are discussed. Detailed study of soft parts of both living and fossil material using SEM is compared with other Cyclocypris species and it is shown that C. diebeli is more closely related to the North American Cyclocypris cruciata Furtos, 1935 than to any European congeneric species. Furthermore, the comparison with other Cyclocypris species with left> right valve overlap results in the conclusion that the subgenus Laevicypris Krstić, 1995 is not a useful division of the genus. [ABSTRACT FROM AUTHOR]