Skeletal anatomy of the extinct shark Paraorthacodus jurensis (Chondrichthyes; Palaeospinacidae), with comments on synechodontiform and palaeospinacid monophyly

The skeletal morphology of Paraorthacodus jurensis, a Late Jurassic neoselachian from Nusplingen, is described based on the incomplete holotype and a newly discovered almost complete specimen. For the first time, the postcranial skeleton could be investigated. Paraorthacodus is characterized by a monognath dental heterodonty and tearing‐type dentition. The number of lateral cusplets in the lateral teeth differs between the holotype and the new specimen, possibly indicating sexual dimorphism. Clasper organs are not preserved in either of the two specimens. The notochord is sheathed by about 123 well‐calcified vertebral centra. The posterior‐most caudal vertebrae are lacking. The transition from monospondylous thoracic to diplospondylous abdominal vertebrae occurs at centra 48 and 49. The origin of the caudal fin is at the 80th centrum. Most conspicuous is the presence of a single spineless dorsal fin. In this respect, Paraorthacodus differs from most palaeospinacids, but resembles Macrourogaleus. Palidiplospinax possibly is sister to a group comprising Synechodus, Paraorthacodus, and Macrourogaleus (the Palaeospinacidae). A reinterpretation of dental and skeletal characters of synechodontiform taxa indicates that Synechodontiformes and Palaeospinacidae are monophyletic groupings of basal neoselachians. Synechodontiformes is probably sister to all living elasmobranchs.     

Early Cretaceous Ferns From Lacustrine Limestones At Las Hoyas, Cuenca Province, Spain

A brief outline is presented of the geological conditions prevailing in the hard-water lake that produced the Las Hoyas fossiliferous site in the Serranía de Cuenca (north-east central Spain). The corresponding Barremian laminated limestones contain varied fossil remains including plants. The fern component of the assemblage is described in the present paper. Ten taxa are referable to the families Matoniaceae, Dicksoniaceae and Schizaeaceae, whilst eight are unclassified. A new species of Dicksoniaceae is described: Coniopteris laciniata. Three species, Pelletixia valdensis, Cladophlebis albertsii, and Sphenopteris fontainei, are recorded here for the first time outside the English Wealden; one species, Acrostichopteris foliosa, is new to the Barremian of Europe. The fern assemblage from the Las Hoyas site is most similar to that of the English Wealden. The xeromorph character of some species is noted.   Although the specimens from Las Hoyas are generally small, even tiny, most are still identifiable leaf fragments preserved as imprints on platy limestone. Epidermal detail has been obtained from a few impressions. Some rather delicate remains, such as indusia, a crozier with pinnules, and fragments of Pelletixia valdensis occur, thus suggesting limited residence time in water.     

THE IDENTITY AND REPRODUCTIVE STRUCTURES OF A MISPLACED SOLENOPORA (RHODOPHYCOPHYTA) FROM THE ORDOVICIAN OF SOUTHWESTERN OHIO AND EASTERN INDIANA1

A study of certain fossil, limestone-forming algae in upper Ordovician beds (Elkhorn and Whitewater Formations of the Richmond Subseries of the Cincinnati Series) in southwestern Ohio and adjacent eastern Indiana culminated with the conclusion that an organism originally described as a sponge, and later placed in the genus Girvanella Nicholson and Etheridge (Cyanochloronta), should in fact be transferred to the genus Solenopora Dybowski (Rhodophycophyta), A calcified reproductive layer was discovered in one of the specimens sectioned. These structures are interpreted as either sporangia or as sporangial chambers, and occur in a sorus rather than a conceptacle type of arrangement. This find has an important bearing on the phylogenetic history of the Solenoporaceae.     

Storm-dominated deposition of the Lower Jurassic crinoidal limestones in the Krížna unit, Western Tatra Mountains, Poland

The Lower-Middle Jurassic of the Krína unit in the Western Tatra Mts. (southern Poland) shows considerable facies variation. Crinoidal grainstones of variable thickness (up to 12 m) are one of characteristic facies. They occur above spiculites which were deposited below storm wave base on the slopes of elevated horsts. First single beds of crinoidal limestones occur within spiculites. They were deposited as event beds, generated probably by storms. The overlying thick complex of well-sorted grainstones composed almost entirely of crinoidal ossicles display widespread erosional bed amalgamation, hummocks and locally wave-formed ripples. The above characteristics are the effects of multiple reworking and winnowing of fine crinoidal material by oscillatory currents related to storms. This proves that the sedimentation of the crinoidal grainstones took place between the storm and the fair-weather wave bases. The vertical transition from spiculites with intercalations of crinoidal limestone beds towards the crinoidal grainstones is interpreted as the result of a shallowing upward trend. Since this trend is opposite to the global Early Toarcian transgression, this could be related to an uplift due to local block tectonic activity. The evidence for that is diversification of facies in the Krína Basin, as well as submarine slumps recorded in spiculites. The location of Krína Basin on relatively low northern latitude and on western edges of great Tethys Ocean during Early Jurassic enabled the formation of the crinoidal tempestites.     

The late jurassic ‘Massenkalk fazies’ of Southern Germany: calcareous sand piles rather than organic reefs

Summary Upper Jurassic (Malm δ to ζ1) massive limestones (‘algal-sponge-reefs, sponge-reefs, reef-complexes, reefs, algal-sponge-bioherms, biolithites, Massenkalk, bioherms, Stillwasser-Mudmounds’) were analyzed in the Southern Swabian Alb, the Southern Franconian Alb and in drilling wells in the Molasse basin (Southern Bavaria). This analysis was carried out within the frame of a multidisciplinary DFG-study with the objective of decifering the controls on the development of Upper Jurassic spongiolites, their three-dimensional distribution, their characteristic faunal composition, and the diagenetic trends of the different primary facies. The data base consists of detailed facies mapping in the areas of the Eybtal and the Blautal (1300 samples) as well as comparative studies in the Upper Donautal (Swabian Alb) and the Southern Franconian Alb (400 samples). All together about 500 thin sections were studied. The distribution of the most important components (ooids, intraclasts, peloids, corals, sponges, sponge spicules, cyanobacterial crusts, brachiopods, molluscs, echinoids, bryozoans, serpulids,Terebella, Tubiphytes), and diagenetic features (dolomite, dedolomite, silicification, stylolites, clay flasers, hematite patches) results in a spatial distribution pattern of facies types. The largest part (70 %) of the massive limestones consists of a peloid-lithoclast-ooid sand facies rich in completely or partly micritized ooids. These ooids, especially in beds of the Malm δ to ε, might be the clue to a reinterpretation of the water depth. True biogenic constructions occur (about 30 % of the volume; sponge-algalmudmounds, algal-sponge-boundstones, and brachiopod-algal-sponge-mounds) within and at the margins of this facies and are interpreted as platform sands. The spatial distribution of the buildups in relation to the sand facies was probably controlled by hydrodynamic conditions. In addition, zoned sponge-algal-mounds occur in intraplatform channels and nodular sponge-algal-mudmounds in the marly basin sediments between platform sand areas. Breccias and slumpings in beds older than the Malm ζ have to be reinterpreted. Most of the breccias found originated from the flanks of the sand platforms, reflecting the faunal composition of the algal-sponge-boundstones which stabilized the flanks. Breccias of this composition occur throughout the Malm δ-ζ1 and differ markedly in their composition from the sand facies. The boundary breccia (Malm ε/ζ1) is interpreted as marking a regressive maximum. The increasing growth of buildups, rich in brachiopods in the Malm ζ1, is ascribed to an increase of reef growth at the beginning of a transgression. Detailed facies analyses necessary for the reconstruction of the spatial distribution of different facies types are in progress. Most of the older data on faunal distributions cannot be used for detailed facies analysis because they differentiated only between massive facies and bedded facies. Therefore Upper Jurassic limestones of Southern Germany should be restudied in order to recognize the volumetric importance of sand facies and buildups within massive limestones.     

A new look at the Late Jurassic Canjuers conservation Lagerstätte (Tithonian,Var, France)

The Canjuers conservation Lagerstätte represents a Late Jurassic lagoonal environment. The sedimentology and stratigraphy of the locality show three different depositional sequences. Fossils are mainly found in the basalmost layers that correspond to the first phase of deposition in the lithographic limestones sensu stricto. The fossil biodiversity is rich. So far, more than 1000 specimens including 38 invertebrate and 18 vertebrate taxa have been recovered from the limestones. The depositional information suggests that most invertebrates and vertebrates were not autochthonous to the lagoon, but swept in during storm events from the open sea or nearby emerged reef environments.     

Diversity and palaeoecology of the enigmatic genus Knebelia (Eucrustacea,Decapoda, Eryonidae) from Upper Jurassic plattenkalks in southern Germany

For a long time, the genus Knebelia Van Straelen, 1922 has comprised two species of eryonid lobster, K. bilobata (Münster, 1839) and K. schuberti (Meyer, 1836), both recorded exclusively from Late Jurassic Lagerstätten in southern Germany. Recently, the latter has been suggested to represent a juvenile individual of Cycleryon propinquus (Schlotheim, 1822). A re‐examination of the type and new material has led to our rejection of that interpretation and confirmation of assignment of this species to Knebelia. Two specimens, both possessing short frontal lobes, from plattenkalks at Nusplingen (late Kimmeridgian) and at Solnhofen (early Tithonian), respectively, are here assigned to a new species, K. totoroi sp. nov. This new species and a review of K. bilobata have furnished new insights into the origin and function of the frontal lobes, which are expansions articulated to the front of the carapace. They probably functioned as rudders facilitating ‘tail‐flip swimming’ as observed in the paddle‐like antennae of extant scyllarids (Eucrustacea, Decapoda, Scyllaridae). The rudder‐like lobes identified in Knebelia may therefore represent a case of convergent evolution.     

Bioconstructions bajociennes a madréporaires et faciès associés dans l'Île Crémieu (Jura du Sud; France)

First of all this study brings necessary details aboutregional stratigraphy. It goes on to reconstitute the paleobiocenoses and the environmental conditions of bajocian coral limestone deposits: weak currents, fairly high depth, varied substrates, low relief. In the low areas scleractinians disappear and are replaced by sponges, Pseudomelania or pholadomyes communities. In order to explain the particularities of bajocian constructions, some hypothesis have been put forward, mentioning the slope of the platforms, the speed of the growth of organisms and the stability of the sea-level.