Ewa Olempska

First record of preserved soft parts in a Palaeozoic podocopid (Metacopina) ostracod, Cytherellina submagna : phylogenetic implications

The metacopines represent one of the oldest and most important extinct groups of ostracods, with a fossil record from the Mid-Ordovician to the Early Jurassic. Herein, we report the discovery of a representative of the group with three-dimensionally preserved soft parts. The specimen—a male of Cytherellina submagna—was found in the Early Devonian (416 Ma) of Podolia, Ukraine. A branchial plate (Bp) of the cephalic maxillula (Mx), a pair of thoracic appendages (walking legs), a presumed furca (Fu) and a copulatory organ are preserved. The material also includes phosphatized steinkerns with exceptionally preserved marginal pore canals and muscle scars. The morphology of the preserved limbs and valves of C. submagna suggests its relationship with extant Podocopida, particularly with the superfamilies Darwinuloidea and Sigillioidea, which have many similar characteristic features, including a large Bp on the Mx, the morphology of walking legs, Fu with two terminal claws, internal stop-teeth in the left valve, adductor muscle scar pattern, and a very narrow fused zone along the anterior and posterior margins. More precise determination of affinities will depend on the soft-part morphology of the cephalic segment, which has not been revealed in the present material.

Morphology and affinities of Eridostracina: Palaeozoic ostracods with moult retention

Ostracods are by far the most abundant living group of arthropods in the fossil record. Traditionally, eridostracines were classified as members of the Class Ostracoda. They have also been considered to represent extinct marine spinicaudatan (conchostracan) branchiopods. The ostracod affinity of the Eridostracina is evident in a number of features such as the muscle scars pattern, the hinge structure, the presence of an adductorial sulcus reflected as a ridge on the internal surface and the separation at the dorsal margin of successive valves. The eridostracines might be a polyphyletic group, containing aberrant representatives of ostracods, with ancestors probably among the conchoprimitid, leperditellid and beyrichioidean ostracod species. The Eridostracina represent an extinct group of small marine crustaceans with a multilayer structure of the calcified carapace, formed through the retention of unshed moults during the growth process. Details of the morphology of the eridostracine Cryptophyllus socialis from the Upper Devonian of Russia are reconstructed using the process of exfoliation of successive exuviae. ‘Double-sided’ hingement structures were found in the accumulated exuviae. It is suggested that the main function of these structures was the strengthening of the connection between the accumulated valves. The hingement of Cryptophyllus represents a vestigial structure, which has lost its original function as a pivot, a role documented in the ancestors of that genus. Tubular structures were found attached to the internal side of the calcite layer. It is suggested that they also represent vestigial pore canals, having lost their original function as sensory receptors. External surfaces of the attached exuviae bear imprints of the tubular structures of the overlying exuviae. These imprints originated probably due to the strong pressure of the new cuticle against the old one, during the very short moulting time. During this process, the freshly formed cuticle was at its final size, but still soft and non-calcified. A number of three-dimensionally preserved cell-like structures were recovered inside the interlayer chambers.

Ontogeny and sexual dimorphism in the Middle/Late Devonian rhomboentomozoid ostracod Franklinella

A large number of three-dimensionally preserved, pyritized specimens of different instars of the rhomboentomozoid ostracod Franklinella (Franklinella) lysogorensis n. sp. were recovered from a mudstone of the Givetian/Frasnian transition beds at Wzdół in the Holy Cross Mountains, Poland. Seven growth stages are identified. Sexual dimorphism is manifested by differences of ribbing pattern in adults. Within the superfamily Entomozoacea, the presence of two types of sexual dimorphism is suggested: ornamental in rhomboentomozoids and domiciliar in entomoprimitiids. Formerly poorly known morphological features of the rhomboentomozoids, including the anteroventral indentation and a contact list ornamented by fine striation, are described.

Exceptional soft-tissue preservation in boring ctenostome bryozoans and associated "fungal" borings from the Early Devonian of Podolia, Ukraine

Colonies of boring ctenostome bryozoans and microborings of “fungi” that occur in the Early Devonian (Lochkovian, ∼416 Ma) of Podolia, western Ukraine, have soft-tissue preserved by phosphatization. These comprise exceptional three-dimensional body walls of feeding zooids with probable parietal muscles inserted on the cystid wall, and setigerous collars twisted within the vestibulum. The presence of collars in this Early Devonian ctenostomes proves the existence of this feature for more than 416 Ma of ctenostome evolution. Phosphatized remains of the zooid walls are interpreted as relicts of the originally chitinous cystid walls. This is the first record of soft-tissue fossilization in a boring bryozoan. The presence of cavities (specialized heterozooids), empty or filled with laminated calcium phosphate, is also documented in bryozoans for the first time. These cavities are interpreted as “store-rooms” in which the bryozoans accumulated nutrients. The new taxon, Podoliaporu doroshevi gen. et sp. nov. is described. In additional, phosphatised fungi-like endoliths co-occur with bryozoans.

Palaeozoic roots of the sigilliid ostracods

Abstract Podocopine ostracods rapidly increased in species diversity after the Palaeozoic, and 32 out of the 36 podocopine families are extant ( Whatley et al., 1993 ), but the phyletic origins are known for only a few. The Sigilliacea are unique in having a long and detailed fossil record. The Sigilliidae known from the recent and Mesozoic faunas differ from others ostracods in having large adductor muscle scars with many spots, a character typical rather to Palaeozoic forms. Paleozoic Microcheilinellidae were morphologically close to the sigilliids, but details of their hingement and carapace margin structures were unknown until now. Silicified specimens of Microcheilinella mendelgrammi, new species, from the Early Carboniferous of southern China and Microcheilinella mandelstami, from the Middle Devonian of north-western Poland show merodont hingement and narrow calcified inner lamella. This makes their relationship to the Mesozoic, Tertiary, and recent sigilliids Saipanetta, Cardobairdia, Sigillium, and Kasella likely. The sigilliid lineage was thus established already in the Devonian. Tubulibairdia, with adont hingement and tubulous shell wall, and Microcheilinella s. s., with merodont hingement and no tubules, are distinct genera in different families.

Ostracodes of the Maple Mill Shale Formation (Upper Devonian) of southeastern Iowa, U.S.A.

The Upper Devonian Maple Mill Shale Formation in southeastern Iowa, U.S.A., has yielded a diverse and unusual ostracode fauna consisting of eighteen benthic species and one (probably planktonic) entomozoacean species. Only two species have been previously described. Although the remaining species are considered new, because of poor preservation only three are named herein: Triceratina lethiersi n. sp., Graphiadactylloides kalonaensis n. sp. and Entomozoe (Nehdentomis?) kindlei n. sp. At the species level the fauna is unique. The absence of Bairdiacea suggests a low oxygen (hypoxic) environment. Conodonts indicate that the ostracode-bearing layer correlates with the Scaphignathus velifer Zone and fragments of cephalopods indicate the Platyclymenia do III-IV Zone.

Lower Devonian ostracods from the Istanbul area, Western Pontides (NW Turkey): Gondwanan and peri-Gondwanan affinities

A Lower Devonian silicified ostracod fauna has been recovered from limestone interbeds in the Buyukdere section of the Kozyatagi Member of the Pendik Formation. Forty-one species belonging to 33 genera have been recognized. Twenty-three are already known, and 15 are described in open nomenclature. One genus and three species ( Omerliella rectangulata gen. et sp. nov., Microcheilinella istanbulensis sp. nov. and Roundyella goekchenae sp. nov.) are described. Silicified larval stages of trilobites, agglutinated foraminifers and conodonts co-occur with the ostracods. The ostracod assemblages are ‘mixed faunas’, between the epineritic Eifelian Mega-Assemblage, representative of high-energy environments, and the basinal Thuringian Mega-Assemblage, representative of low-energy environments. The conodont faunas of the Pendik Formation represent the serotinus , patulus and partitus biozones of the late Emsian – earliest Eifelian. The Emsian ostracods of NW Turkey show numerous species-level links between the Western Pontides (Istanbul Terrane) and assemblages of contemporaneous faunas of the Cantabrian Mountains (Spain), Morocco and Thuringia (Germany), and of similar biofacies. This supports the notion that the Istanbul Terrane, Armorican terrane-collage and northern margins of Gondwana were in geographical proximity in late Early Devonian time.

Early Frasnian ostracods from the Arche quarry (Dinant Synclinorium, Belgium) and the Palmatolepis punctata Isotopic Event

Ostracods from the Arche quarry at Frasnes are analysed. Twenty-seven species are recognised in the Chalon Member and in the very base of the Arche Member of the Moulin Liénaux Formation. Three new species: Scrobicula gracilis, Microcheilinella archensis, and Bairdia (Rectobairdia) chalonensis, and one subspecies Plagionephrodes laqueus praelaqueus, are proposed. The fauna is in the Favulella lecomptei Zone based on metacopid ostracods and belongs to the Eifelian Mega-Assemblage. Ostracods are indicative of a regressive trend from a moderately deep poorly oxygenated marine environment below fair weather wave base to very shallow well oxygenated and agitated environments. Comparison of the ostracod fauna present in the Arche quarry with faunas described from the Frasnes railway section and from the Lion quarry shows that ostracods did not suffer a crisis during the Palmatolepis punctata Conodont Zone and close to the Early—Middle Frasnian boundary.

Affinities of Palaeozoic encrusting ascodictyid ‘pseudobryozoans’

Small encrusting marine organisms belonging to the genera Ascodictyon, Eliasopora and Vinella were originally described as ctenostome bryozoans. Well-preserved ascodictyid specimens from the Early and Middle Devonian of Poland allow us to exclude such an affinity due to the absence of any aperture in the ascodictyid vesicles for the protrusion or withdrawal of the lophophore during feeding. The ctenostome bryozoans are soft-bodied, but the ascodictyid vesicles and filaments have calcified walls. Reinterpretation of Eliasopora stellata (Nicholson & Etheridge, 1877), Eliasopora sparsiforme (Kiepura, 1965) and ‘Ascodictyon’ venustum Kiepura, 1965, provides a basis for the recognition of a new group of extinct Palaeozoic organisms, defined by a combination of morphological features including the presence of a thread-like network of perforate branching filaments, perforate vesicles formed by swollen tips of the filaments, and the ability of filaments to fuse. This distinguishes Ascodictyidae from all other known extant microorganisms. The shape, size and perforated walls of vesicles make ascodictyids similar to the Palaeozoic tuberitinid ‘foraminifers’. It remains to be determined which morphology is plesiomorphic and which is derived.

Late Silurian and Devonian ostracods of the Istanbul Zone (Western Pontides) and the Taurides: palaeogeographical implications

Non-metamorphic Palaeozoic sedimentary successions without major breaks exist in the Istanbul Zone of the Western Pontides (northern Turkey) and in the Taurides (southern Turkey). Based on different proxies, a Gondwanan affinity has been determined for the Taurides; however, the palaeogeographical position of the Istanbul Zone is still controversial. The aim of this paper is to discuss possible contributions of late Silurian and Devonian ostracods to the palaeogeographical assignment of the Western Pontides (Istanbul Zone). Furthermore, ostracods of the Taurides have also been evaluated in terms of the palaeogeographical setting of this terrane. Late Silurian ostracods of the Istanbul Zone (Western Pontides) show close similarities at the species level with the assemblage from the upper Silurian (Ludlow) rocks of Baltica. This Laurussian affinity indicates a palaeogeographical setting to the north of the Rheic Ocean for the Pontides during the late Silurian. The Devonian ostracod assemblages of both the Taurides and the Istanbul Zone have an affinity to both Laurussia and Gondwana. Therefore, a faunal link should exist during this long period between Laurussia and Gondwana. The faunal link between the two palaeocontinents can be explained on the one hand by a narrow ocean with shallow pathways. On the other hand, a wider ocean with long-shore currents, with broad and shallow shelf areas and/or islands functioning as stepping stones would also allow a faunal link for benthic ostracods.