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Ostracods are the most abundantly preserved arthropod group in the fossil record, but they are almost entirely represented only by their calcitic carapaces. In over two hundred years of fossil ostracod research, only about 33 occurrences of fossil ostracods that include preserved appendages, or soft parts, have been reported. These range from the Ordovician through to the Holocene, and are from a wide range of paleoenvironments, including the seas, brackish inlets, lakes, caves, and the edges of ancient forests. Preservation includes silica, phosphate, goethite, pyrite or calcite mineralization replacing or coating soft parts, or direct preservation of the chitinous body and appendages, such as with amber entombment and mummification. Although rare, they have provided information on the morphology of some of the earliest ostracods, given clues about phylogenetic relationships of extinct groups, and demonstrated remarkably long periods of evolutionary stasis. Preserved sexual organs, eggs, brooded juveniles and even spermatozoa have given valuable insights into the reproduction of the group. Technological advances, such as scanning electron microscopy and more recently micro- and nanotomography, have dramatically expanded our capabilities to study these specimens, even down to the sub-cellular level. This review presents these occurrences in a historical context, from the first to the most recently reported, and highlights how these discoveries have contributed to our understanding of ostracod evolution.

The bivalved crustacean ostracods have the richest fossil record of any arthropod group and display complex reproductive strategies contributing to their evolutionary success. Sexual reproduction involving giant sperm, shared by three superfamilies of living ostracod crustaceans, is among the most fascinating behaviours. However, the origin and evolution of this reproductive mechanism has remained largely unexplored because fossil preservation of such features is extremely rare. Here, we report exceptionally preserved ostracods with soft parts (appendages and reproductive organs) in a single piece of mid-Cretaceous Kachin amber (approximately 100 Myr old). The ostracod assemblage is composed of 39 individuals. Thirty-one individuals belong to a new species and genus, Myanmarcypris hui gen. et sp. nov., exhibiting an ontogenetic sequence from juveniles to adults (male and female). Seven individuals are assigned to Thalassocypria sp. (Cypridoidea, Candonidae, Paracypridinae) and one to Sanyuania sp. (Cytheroidea, Loxoconchidae). Our micro-CT reconstruction provides direct evidence of the male clasper, sperm pumps (Zenker organs), hemipenes, eggs and female seminal receptacles with giant sperm. Our results reveal that the reproduction behavioural repertoire, which is associated with considerable morphological adaptations, has remained unchanged over at least 100 million years—a paramount example of evolutionary stasis. These results also double the age of the oldest unequivocal fossil animal sperm. This discovery highlights the capacity of amber to document invertebrate soft parts that are rarely recorded by other depositional environments.

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 indi...

Pestenacker and the adjacent Neolithic wetland sites Unfriedshausen and Pestenacker-Nord in southern Germany belonged to the Altheim culture from around 5750–5350 years cal. BP. In contrast to contemporaneous pile dwellings, the houses of Pestenacker were constructed at ground level in a wetland environment. Only little is known about the environmental and hydrological conditions in the direct vicinity of the settlement and how they changed in time. To find detailed answers to these questions, stratigraphy, sedimentology, microfossils, geochemistry and stable isotopes of a sediment profile immediately to the west of the settlement were studied. An age model comprises five radiocarbon dates and dates the base of the profile to about 6600 years cal. BP. Ostracods and aquatic gastropods were frequent only in the basal part of the profile. Ostracod taxa typical for open-water conditions point to higher humidity especially at 6120–5860 years cal. BP and 5750–5370 years cal. BP. Sedimentology and organic carbon isotope data confirm this observation. Thereafter open-water habitats disappeared, while increasing numbers of non-aquatic gastropods occur and soil formation is indicated by elevated δ 15 N values. We conclude that during the time of settlement an open water body existed near-by that disappeared shortly after the settlement was abandoned. However, the spatial extent of this water body still remains to be clarified.

Length measurements of sperms of 51 species of Cypridoidea ostracods were taken to supplement the paucity of ostracod sperm data in the published literature. The lengths of the posterior regions (carrying the mitochondria) and the thinner anterior regions were also measured when appropriate. Maximum lengths of sperms for individual species varied from 268 mu m for Fabaeformiscandona velifera Smith and Janz, 2008 through to 11 787 mu m for Australocypris robusta De Deckker, 1974;these lengths represent the shortest so far recorded for the superfamily and the longest ever recorded in ostracods, respectively. There appears to be only a loose relationship between taxonomy and sperm lengths. Species of the subfamily Candoninae generally have the shortest sperms compared with other subfamilies, but one Candoninae species, Candona altoides Petkovski, 1961, has sperms longer than some species of the families Cyprididae, Ilyocyprididae and Notodromadidae. The family Cyprididae showed the most variation, with sperms ranging from 1000 mu m through to 11 787 mu m in length. No hypothesis satisfactorily explains the origin of giant sperms in ostracods or the longevity of this trait through geological eras, and their existence remains enigmatic.

‘Giant sperm’, in terms of exceptionally long spermatozoa, occur in various taxa in the animal kingdom, particularly in arthropods. In freshwater ostracods (Cypridoidea) reproducing with giant sperm, males are equipped with a pair of specialized ejaculators, or Zenker organs, located in the distal part of vas deferens. We observed adult postmoult specimens of a cypridoidean ostracod, Pseudocandona marchica, by SEM, TEM and CLSM and elucidated the formation process of their Zenker organs. This investigation shows that most of the formation process of the Zenker organ takes places after the moult to adulthood. In P. marchica this process can be divided into five stages, referring to consecutive differentiation steps of epithelia, musculature, and chitinous supports. The evolutionary significance of the Zenker organ's morphology in freshwater ostracods is discussed in the light of its maturation process, as well as the relevance of Zenker organs without chitinous spines that were reported in previous studies.

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...

During an ostracod sampling campaign in the city of Munich (Germany) samples were taken from containers in a greenhouse of the Munich Botanical Garden. Beside the ubiquitous speciesCypridopsis vidua(O. F. Müller, 1776), the samples contained four alien species, i.e.,Chlamydotheca arcuata(Sars, 1901),Strandesia bicuspis(Claus, 1892),Tanycypris centaChang, Lee & Smith, 2012, andTanycypris alfonsiNagler, Geist & Matzke-Karasz, 2014. While sorting the livingTanycyprisspecimens, a yet undescribed usage of the caudal rami was observed. Freshwater ostracods usually move on or in the sediment by using their first and second antennae, walking legs and — if not reduced — their caudal rami. During (non-swimming) locomotion of most freshwater ostracods with well-developed caudal rami, they help pushing the body forward by being used as a lever. This movement can be fast, but has never been reported to include sudden jumps. In contrast, both investigatedTanycyprisspecies show an extraordinarily fast movement, especially when disturbed. Recordings with a high-speed camera were made, shooting horizontally into a 1.5-mm-thick micro-aquarium. The fast movement could be identified as a powerful jump, much resembling the movement of a catapult, propelled by a very rapid repulsion of the caudal rami from the ground. Although sized only around 1 mm, the observed specimens reached top speeds of up to 0.75 ms−1. Anatomically, this speed is obtained by the exceptional length of the caudal rami inTanycypris, combined with a well-developed musculature, which stretches from a broadened posterior end of soft body along the so-called ‘caudal rami attachment’. The jump itself resembles that of springtails or fleas, where the jump is powered by the energy previously stored in an elastic proteinaceous material; however, inTanycyprisno such mechanism could be detected and thus the energy for the catapult-like jump must be considered muscular, possibly aided by tendon-like structures and/or a mechanism involving a muscular pre-tension by a click-joint as recorded for Squillids.

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 collaris sp. nov., Candonocypris fimibolus sp. nov. and Newnhamia mckenziana sp. 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 ...

Spermatozoa of the ostracod superfamily Cypridoidea include some of the longest in the animal kingdom, but unlike other so-called giant spermatozoa, they are aflagellate, probably evolved only once, and represent an exceptionally old trait. Sperm length variations within cypridoidean species remain poorly known, a lack that hinders the development of hypotheses to explain their length and variation. For this study, the lengths of 500 spermatozoa from each of five species of freshwater cypridoidean ostracods, Candonopsis tenuis (Brady, 1886), Fabaeformiscandona subacuta (Yang, 1982), Heterocypris rotundata (Bronshtein, 1928), Ilyocypris japonica Okubo, 1990, and Notodromas trulla Smith and Kamiya, 2014, were measured, including the lengths of the posterior and anterior regions. No overall pattern in sperm variation was discernible. Length variations between species, between males of the same species, and within individual males varied from low (Candonopsis tenuis) to extraordinarily large (Notodromas trulla and Fabaeformiscandona subacuta). Sperm competition, cryptic female choice, sperm heteromorphism, and testis size are unlikely to explain all of the variations observed. Age structures of the populations sampled might play a role in explaining some intraspecific variation. The differing amounts of variation in sperm characters revealed in this study suggest that multiple evolutionary trends and pressures shape sperm lengths in this superfamily.

Previous studies of cypridoidean ostracods have noted that (1) their giant spermatozoa are immotile inside the male, (2) these spermatozoa are motile in the female seminal receptacle and (3) these receptacles are often filled with empty sperm coats. Such findings have led previous authors to hypothesize that sperm must shed their coats in the female receptacle to become motile. We present light and electron microscopy results and video recordings of mating experiments with virgin specimens of Mytilocypris mytiloides. We show that the empty sperm coats frequently found in the female receptacles are not the result of sperm molting but are the resistant inner coats of exhausted sperm not used for egg fertilization. In contrast, we show that an outer granular coating material is successively removed from the sperm while resident inside the female receptacles before first oviposition occurs. During this period, previously immotile sperm gain motility, showing strong movement shortly before first oviposition takes place. By correlation of these phenomena, we suggest that dissolution of the outer coat material is required for motility to develop.

The Tabriz Basin is located in NW Iran within the collision zone of the Arabian and Eurasian plates. Its Upper Miocene and ?Pliocene basin fill, termed Lignite Beds and Fish Beds, can provide detailed insights into the Neogene environments and processes during a time of intense tectonics and volcanism. However, a modern re-evaluation of the Lignite Beds and Fish Beds is lacking. Here we present fission track (FT) data from the northern hinterland of the Tabriz Basin (Upper Red Formation) and from the Fish Beds, which support previous age assumptions for the Upper Red Formation, but, together with the new biostratigraphic data, point to an older stratigraphic age for the Lignite and Fish Beds than previously thought (Lignite Beds: 11.6–10.0 Ma; Fish Beds: 10.0–7.5 Ma). Furthermore, we describe for the first time the fossil fish and ostracod fauna and the diatom assemblages from both the Lignite Beds and Fish Beds. All fossil groups are characterized by the occurrence of freshwater and brackish forms; additional marine–euryhaline taxa appear among the fishes and diatoms. It can be assumed that the Lignite and Fish Beds represent deposits of a lacustrine to euryhaline Late Miocene Lake Urmia during the initial state of the Tabriz Basin subsidence, and that the ancient lake was located farther to the east and in a higher altitude than the present-day Lake Urmia. The fossil assemblages indicate a new palaeogeography for the Late Miocene of the study area, with temporary connections between the Tabriz Basin and the southern Caspian Sea, perhaps via an ancient Araks River passage.

A new anatomical interpretation of the skeleto-musculature of the mandible in podocopid ostracodes is proposed based on ultrastructural observations of Loxoconcha pulchra Ishizaki, 1968 and Fabaeformiscandona tyrolensis (Löffler, 1963). Attachment cells with their numerous microfibers anchor the sclerotized lamella cuticle (chitinous rod) to the outer lamella cuticle via intracuticular fibers. A pan-shaped structure develops at the attachment area in the outer lamella cuticle and is responsible for the mandibular scar. The sclerotized lamella cuticle is continuous with the dorsal apex of the mandibular coxa, which touches the fulcral point directly without intermediate epidermis. The calcification of the fulcral point starts immediately after ecdysis and this rapid calcification suggests that the fulcral point must play a significant role in functional morphology of podocopid ostracodes. After 3D-reconstruction of the set of mandibular extrinsic muscles in a podocopid ostracode, we suggest that the fulcral point is a key character for carapace opening by transmitting the force from the mandibular coxa to the valve and at the same time functions as the stable fulcrum for mandibular movement during mastication.

The antennule is the first appendage of ostracods and in the superfamily Cypridoidea is known to have two presumed chemical receptors, the ya aesthetasc on the final segment and the Rome organ on the ventral side of the second moveable segment.Wouters (1999) was the first to document a third presumed chemical receptor on the antennule, the ‘new’ organ, on the dorsal side of the first segment in 11 species of the subfamily Paracypridinae (Candonidae). Subsequently, this organ was also recorded inStrandesia kimberleyi (Cypricercinae, Cyprididae) (Karanovic 2005b). During a preliminary survey of the superfamily Cypridoidea, we found the ‘new’ organ in an additional 22 species, in seven subfamilies and two families, but were unable to find it in another 45 species. All species of the subfamily Candoninae of the family Candonidae checked show no evidence of the organ, and instead have a seta in a similar position. In contrast, all species of the subfamily Cyclocypridi-nae and most species of the subfamily Paracypridinae (both also subfamilies of the family Candonidae) checked have the organ present, but no seta. Scanning electron microscopy reveals that the ‘new’ organ shows a wide morphological variability. Light-microscopical studies show that inParacypria inujimensis (Okubo, 1980), in both the Rome organ and the ‘new’ organ, an internal tube runs through the length of the organ. At the base of the external protuberances, these internal tubes protrude into the antennule, heading proximally either into the middle of the precedent segment (Rome organ) or towards the labrium (‘new’ organ). Both these tubes become slightly wider at their proximal ends before they peter out. The ‘new’ organ first appears in the A-5 instar ofP. inujimensis and has a morphology similar to that of the adult’s by the A-4 instar. The seta of the Candoninae first appears a stage later, in the A-4 instar, and therefore may not be homologous with the ‘new’ organ. The present study gives a broader overview on the presence and absence of the ‘new’ organ in the Cypridoidea and its possible phylogenetic implications. The ‘new’ organ is herein renamed the Wouters organ, honouring Karel Wouters’ important contributions to ostracodology in general and the discovery of this organ in particular

[Afrocypris barnardi G. O. Sars, 1924, a giant temporary pool ostracode from South Africa, is here redescribed, based on new material. It is only the second time that this species has been found. The present morphological analyses show that the copulatory appendages of both sexes have unusual characteristics. In the female, at least three paired appendage-like structures (R-appendages) are associated with the Female Reproductive Organ (FRO). This is the second time that such structures are described from non-marine ostracodes, Liocypris grandis (G. O. Sars, 1924) having six pairs of such structures. The male copulatory organs have a Penile Attachment uniting the proximal sides of both hemipenes, and in Afrocypris barnardi an asymmetrical, finger-like structure is associated with this PA.The discovery of female R-appendages in a second species strengthen the interpretation of these structures as (part of) true appendages, and reinforces the hypothesis that the FRO is homologous to more than one ancestral somite. However, it remains unclear how many body segments are involved in the origin of the FRO, and three, five, or even six somites are all possible. In addition, these R-appendages can be ancestral, atavistic, or even apomorphic. The position of the two taxa with such appendages in a phylogeny of the Cyprididae as a whole will constitute a test to discriminate between these three possibilities. Basierend auf neuen Funden wird Afrocypris barnardi G. O. Sars, 1924, eine Gros-Ostracodenart aus ephemeren Kleingewassern Sudafrikas, hier wiederbeschrieben. Die Funde stellen erst den zweiten Nachweis dieser Art dar. Die neue morphologische Untersuchung zeigt, das die Kopulationsorgane beider Geschlechter ungewohnliche Merkmale aufweisen. Dem externen weiblichen Kopulationsapparat (FRO) sind mindestens drei paarige, extremitatenartige Anhange (R-Appendages) zugeordnet. Erst zum zweiten Mal werden solche Strukturen fur eine Suswasserostracodenart nachgewiesen: Liocypris grandis (G. O. Sars, 1924) besitzt sechs solcher Anhange.Das Kopulationsorgan des Mannchens besitzt einen Anhang (PA), welcher die proximalen Bereiche der beiden Hemipenes verbindet. Auf diesem Anhang inseriert bei Afrocypris barnardi zudem eine asymmetrische fingerformige Struktur.Die Entdeckung von zusatzlichen extremitatenartigen Anhange des weiblichen Kopulationsapparates in einer zweiten Ostracodenart verstarkt ihre Interpretation als (Teile von) echte(n) Extremitaten und unterstutzt die Hypothese, das der weibliche Kopulationsapparat mehr als einem ursprunglichen Segment homolog ist. Allerdings bleibt unklar, wieviele Korpersegmente in die Bildung des Kopulationsapparates involviert sind; drei, funf oder sogar sechs Segmente waren denkbar. Zudem konnen diese zusatzlichen Anhange sowohl ancestrale, als auch atavistische oder apomorphe Merkmale darstellen. Erst die Positionierung der beiden Taxa mit solchen Anhangen in einer Phylogenie der Cyprididae wird eine Entscheidung ermoglichen., Afrocypris barnardi G. O. Sars, 1924, a giant temporary pool ostracode from South Africa, is here redescribed, based on new material. It is only the second time that this species has been found. The present morphological analyses show that the copulatory appendages of both sexes have unusual characteristics. In the female, at least three paired appendage-like structures (R-appendages) are associated with the Female Reproductive Organ (FRO). This is the second time that such structures are described from non-marine ostracodes, Liocypris grandis (G. O. Sars, 1924) having six pairs of such structures. The male copulatory organs have a Penile Attachment uniting the proximal sides of both hemipenes, and in Afrocypris barnardi an asymmetrical, finger-like structure is associated with this PA.The discovery of female R-appendages in a second species strengthen the interpretation of these structures as (part of) true appendages, and reinforces the hypothesis that the FRO is homologous to more than one ancestral somite. However, it remains unclear how many body segments are involved in the origin of the FRO, and three, five, or even six somites are all possible. In addition, these R-appendages can be ancestral, atavistic, or even apomorphic. The position of the two taxa with such appendages in a phylogeny of the Cyprididae as a whole will constitute a test to discriminate between these three possibilities. Basierend auf neuen Funden wird Afrocypris barnardi G. O. Sars, 1924, eine Gros-Ostracodenart aus ephemeren Kleingewassern Sudafrikas, hier wiederbeschrieben. Die Funde stellen erst den zweiten Nachweis dieser Art dar. Die neue morphologische Untersuchung zeigt, das die Kopulationsorgane beider Geschlechter ungewohnliche Merkmale aufweisen. Dem externen weiblichen Kopulationsapparat (FRO) sind mindestens drei paarige, extremitatenartige Anhange (R-Appendages) zugeordnet. Erst zum zweiten Mal werden solche Strukturen fur eine Suswasserostracodenart nachgewiesen: Liocypris grandis (G. O. Sars, 1924) besitzt sechs solcher Anhange.Das Kopulationsorgan des Mannchens besitzt einen Anhang (PA), welcher die proximalen Bereiche der beiden Hemipenes verbindet. Auf diesem Anhang inseriert bei Afrocypris barnardi zudem eine asymmetrische fingerformige Struktur.Die Entdeckung von zusatzlichen extremitatenartigen Anhange des weiblichen Kopulationsapparates in einer zweiten Ostracodenart verstarkt ihre Interpretation als (Teile von) echte(n) Extremitaten und unterstutzt die Hypothese, das der weibliche Kopulationsapparat mehr als einem ursprunglichen Segment homolog ist. Allerdings bleibt unklar, wieviele Korpersegmente in die Bildung des Kopulationsapparates involviert sind; drei, funf oder sogar sechs Segmente waren denkbar. Zudem konnen diese zusatzlichen Anhange sowohl ancestrale, als auch atavistische oder apomorphe Merkmale darstellen. Erst die Positionierung der beiden Taxa mit solchen Anhangen in einer Phylogenie der Cyprididae wird eine Entscheidung ermoglichen.]

Ostracods of the superfamily Cypridoidea have giant spermatozoa. However, little data exist on the sperm-egg interaction in this group: only two publications have so far given the most ambiguous indication that the entire sperm enters the egg on fertilization. These assumptions have not yet been tested with modern techniques, nor has their putative value for developmental and evolutionary investigations been realized. The present paper gives the first, clear, light- and scanning electron microscopical evidence of the entire giant ostracod spermatozoon being incorporated into the egg. Coiling of the sperm underneath the egg shell is shown in the early zygotes of the species Mytilocypris praenuncia and Pseudocandona marchica. Additionally, data on the morphology of female and male reproductive tracts are given for M. praenuncia. Hypotheses on the evolution of giant filiform sperm in the Animal Kingdom are reviewed, and their applicability to ostracods is discussed. The demonstrated ingression of the entire sperm implies the entry of the two giant paternal mitochondrial derivates into the zygote in Cypridoidea and potentially casts doubt upon the dogma of strict maternal inheritance of mitochondrial DNA. Evidence of paternal inheritance of mtDNA in several organisms has recently given rise to a controversial debate on this issue; the possible significance of this phenomenon for molecular studies on ostracod phylogeny and evolution is discussed. J. Exp. Zool. 304B:129-149, 2005. r 2005 Wiley-Liss, Inc.

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 Krstic, 1995 is not a useful division of the genus.

Six charophyte, 13 mollusc, four ostracod and nine fish otolith taxa are taxonomically described, and one fruit, one seed and two foraminiferal taxa are briefly noted from the Lower Cyrena Beds and the Lower Coloured Molasse of the Sindelsdorf section near Penzberg (approximately 50 km south of Munich). Our palaeoecological and lithological data from the Lower Cyrena Beds suggest a delta plain with lagoons, estuaries, slowly flowing rivers, lakes and swamps. Faunal and floral elements of the Lower Coloured Molasse indicate lacustrine environments. The gastropod Tympanotonos and the tropical to subtropical fish fauna (Eleotridae, Ambassidae and Cyprinodontidae) suggest a warm, at least subtropical climate. Furthermore, Tympanotonos suggests comparisons with Recent molluscan faunas of the mangrove swamps of the West African coast, and thus hints at mangrove vegetation bordering the coasts of the Upper Bavarian Molasse Sea. A biostratigraphical classification for the Oligocene Molasse deposits of the Penzberg Syncline is established for the first time based on otoliths and charophytes. The Lower Cyrena Beds are attributed to the newly defined otolith zone OT-O1/2 and probably correspond to the oldest part of the Chara microcera Zone. The lowermost part of the Lower Coloured Molasse can be correlated both with otolith zone OT-O2 and the Chara microcera Zone. The Sindelsdorf section lies within the Rupelian–Chattian transition zone and thus the chronostratigraphic age is approximately 29–28 Ma.

Fossil spermatozoa are recorded for the first time in freshwater ostracods (small bivalved crustaceans) from Holocene sediments at sites in the United Kingdom and Germany. Exceptional conditions at these sites have resulted in the preservation of chitinous "soft parts", including limbs, the remains of Zenker's Organs (sperm pumps that are part of the male reproductive apparatus in cypridoidean ostracods) and spermatozoa from eight different species. Comparisons are made with spermatozoa from living ostracods and the implications of these discoveries for evolutionary studies of reproductive modes are discussed.

‘Giant sperm’, in terms of exceptionally long spermatozoa, occur in a variety of taxa in the animal kingdom, predominantly in arthropod groups, but also in flatworms, mollusks, and others. In some freshwater ostracods (Cypridoidea), filamentous sperm cells reach up to ten times the animal’s body length; nonetheless, during a single copulation several dozen sperm cells can be transferred to the female’s seminal receptacle. This highly effective ejaculation has traditionally been credited to a chitinous-muscular structure within the seminal duct, which has been interpreted as a sperm pump. We investigated this organ, also known as the Zenker organ, of a cypridoid ostracod, Pseudocandona marchica, utilizing light and electron microscope techniques and produced a three-dimensional reconstruction based on serial semi-thin histological sections. This paper shows that numerous muscle fibers surround the central tube of the Zenker organ, running in parallel with the central tube and that a thin cellular layer underlies the muscular layer. A cellular inner tube exists inside the central tube. A chitinous-cellular structure at the entrance of the organ has been recognized as an ejaculatory valve. In male specimens during copulation, we confirmed a small hole derived from the passage of a single spermatozoon through the valve. The new data allowed for proposing a detailed course of operation of the Zenker organ during giant sperm ejaculation.

The giant ostracod, Liocypris grandis, found in South African temporary pools, has five pairs of additional appendage-like structures, seemingly associated with the Female Reproductive Organ (FRO). Original investigations of these structures by light and scanning electron microscopy could not unequivocally determine whether or not these structures are homologous to genuine appendages and if so, to how many. The present paper investigates morphology and attachment of these structures by frontal and transversal micro-sectioning (thickness=1 μm) of the caudal soft parts of mature females of L. grandis. It is found that all five appendages (R1–R5) have one individual attachment point where they enter into the FRO. Also R3(I) and R3(II) have a single attachment only, these two parts thus represent one single appendage. Whereas R1–R4 have clear lateral insertions, R5 is caudally positioned. The fusion of this latter appendage with the FRO occurs internally, at the posterior edge of the bulge of the FRO and is not externally visible. It is herewith thus accepted that R1–R5 are genuinely endogenous structures (and not, for example, exogenous parasites), that the five structures are homologous to five appendages, and not for example to parts of biramous appendages. It follows from this that the female reproductive organ is homologous to at least five, not to one segment. This would bring the number of (original) thoracic segments in podocopid ostracods to at least 8. An additional pair of triangular structures, inserted in between the two FRO is here described as structures ‘X’. Their homology and function remain unknown.

Cypridoidean ostracods are one of a number of animal taxa that reproduce with giant sperm, up to 10 000 µm in length, but they are the only group to have aflagellate, filamentous giant sperm. The evolution and function of this highly unusual feature of reproduction with giant sperm are currently unknown. The hypothesis of long-term evolutionary persistence of this kind of reproduction has never been tested. We here report giant sperm discovered by propagation phase contrast X-ray synchrotron micro- and nanotomography, preserved in five Miocene ostracod specimens from Queensland, Australia. The specimens belong to the species Heterocypris collaris Matzke-Karasz et al . 2013 (one male and three females) and Newnhamia mckenziana Matzke-Karasz et al . 2013 (one female). The sperm are not only the oldest petrified gametes on record, but include three-dimensional subcellular preservation. We provide direct evidence that giant sperm have been a feature of this taxon for at least 16 Myr and provide an additional criterion (i.e. longevity) to test hypotheses relating to origin and function of giant sperm in the animal kingdom. We further argue that the highly resistant, most probably chitinous coats of giant ostracod sperm may play a role in delaying decay processes, favouring early mineralization of soft tissue.

A new species of the ostracod genus Scottia Brady and Norman, 1889 from Kanazawa, western Honshu, Japan is described. This species is only the third living representative of this genus. It is most similar to the populations of S. pseudobrowniana Kempf, 1971 from western Europe, but it is smaller, and has unique features of the hemipenes, Zenker organs, antennae and mandibles. A prominent projection on the dorsal lobe of the hemipenes gives this species its name, Scottia birigida sp. nov.. It lives in wet leaf litter around the discharge of a spring, leading a semi-terrestrial lifestyle. This is the first record of Scottia and the subfamily Scottiinae Bronstein, 1947 from Japan and North East Asia, and significantly increases the known distribution of these taxa. This record of Scottia from Japan, together with numerous reports from Europe and two areas in the USA, indicates that in the northern hemisphere this genus is probably widespread. A key to the subfamily Scottiinae is also provided.