TESTATE AMOEBAE FROM THE EARLY JURASSIC OF THE WESTERN TETHYS,NORTH‐EAST ITALY

Abstract: Fossil testate amoebae and their non‐marine finds are rare so their ecological importance through Earth history is poorly understood. The Lower Jurassic shallow water black‐shales of Trento Platform (north‐east Italy) are rich in micro‐organisms and contain a thecamoebian and ostracod assemblage representing the first known record of Early Jurassic oligohaline forms from the European mainland. The thecamoebians are represented by the genera Difflugia, Pontigulasia and Centropyxis. The present discovery of Lower Jurassic thecamoebians in fine carbonate organic‐rich deposits indicates, for the first time, that these sediments can preserve testate amoebae very well. The occurrence of difflugid testate amoebians confirm a transitional marine‐terrestrial habitat, outside large bodies of water, and suggests occasional eutrophication in ephemeral restricted aquatic environment in the Sinemurian–Pliensbachian Trento Platform.     

Dinosaurier aus Nordostdeutschland

Remains of dinosaurs in NE Germany The former clay pit of Grimmen (NE Germany) represents a glacially dislocated outcrop of upper Lower Jurassic shallow‐marine strata. Apart from typical marine organisms, the Lower Jurassic of Grimmen has also yielded the remains of the basal thyreophoran dinosaur Emausaurus ernsti. E. ernsti was a comparatively small dinosaur, generally characterized by a dermal armor composed of small isolated scutes. Recently, the remains of a second dinosaur belonging to the sauropod clade have been identified. The specimen represents the second Early Jurassic basal sauropod from Germany ever found. The sauropod was probably washed into the marine realm from nearby coastal land after its death, whereas the compacted pile of skeletal elements of E. ernsti found in a concretion is suspected to be a Speiballen produced by a large‐scaled marine reptile.     

Palaeoenvironment and taphonomy of a Late Jurassic (Late Tithonian) Lagerstätte from central Poland

A rich assemblage of exceptionally preserved marine and terrestrial fossils occurs in fine‐grained limestones in the upper part of the Late Tithonian (Middle Volgian) shallowing upward carbonate sequence in Central Poland. The richest horizon, a deposit known locally as the Corbulomima horizon, is named after the shallow burrowing suspension feeding bivalve Corbulomima obscura, moulds of which occur in densities of up to 500 per square metre on some bedding planes. The fauna in this bed also includes organic and phosphatic remains of a wide range of other creatures including the exuviae of limulids and decapods, disarticulated fish skeletons and rare isolated pterosaur bones and teeth. There are also perfectly preserved dragonfly wings and beetle exoskeletons. The average stable carbon and oxygen isotope values for ostracod shells and fine‐grained sediment from this horizon suggest precipitation of the calcium carbonate from warm seawater of normal marine salinity. The carbonate sediments overlying the fossiliferous horizon have been interpreted as nearshore to shoreface facies. These pass abruptly into coarse reworked intraclastic sediments interpreted as possible tsunami or storm surge over‐wash deposits. The clasts in this deposit have more positive oxygen isotope values than those in the underlying limestone, which may indicate that they were lithified in a slightly more evaporative, perhaps intertidal, setting. The succession terminates with silicified fine‐grained limestones likely to have formed in extremely shallow lagoonal environments. In contrast with the Solnhofen limestones of Lower Tithonian age in south‐central Germany the Corbulomima horizon is interpreted as a transitional deposit formed in a shallow marine setting by rapid burial with elements of both Konservat‐ and Konzentrat‐Lagerstätte preservation. □Konzentrat and Konservat‐Lagerstätte, Taphonomy, Palaeoenvironment, Paleogeography, Late Jurassic, Poland.     

Stratigraphic application of Thalassinoides ichnofabric in delineating sequence stratigraphic surfaces (Mid-Cretaceous), Kopet-Dagh Basin,northeastern Iran

This study integrates ichnological and sedimentological data to refine depositional sequences and interpretations of sea-level dynamics for the shallow marine, Albian–Cenomanian Aitamir Formation in northeastern Iran. Three ichnofabrics are present in a succession of glauconitic mudstone and sandstone. This is a sequence that grades upward from a lower glauconitic sandstone unit with trough cross-stratification, hummocky and ripple cross-lamination into a fining-up unit of mudstone with intercalated sandstone beds. The lower unit contains an ichoassemblage of the Ophiomorpha–Palaeophycus ichnofabric (upper shoreface), whereas the upper unit bears ichnoassemblages of the Thalassinoides ichnofabric (in a distinctive level at the top cycle which demarcates the base of the next cycle) (middle shoreface) and the Chondrites–Planolites ichnofabric (lower shoreface). An upper shoreface–lower shoreface trend from the Ophiomorpha–Palaeophycus ichnofabric to the Chondrites–Planolites ichnofabric represents a deepening-upward sequence. An integrated sedimentological and ichnological approach has allowed the recognition of the internal organization of the sequence and the characterization of significant discontinuity surfaces at sequence scales. Thalassinoides ichnofabric reveals colonization of firmgrounds during prolonged times between erosion and deposition related to transgressive surfaces. Transgressive surfaces (sequence boundaries) are generally well-cemented and marked by increased glauconite content, and densely crowded, predominantly vertical or oblique, relatively large, very distinct, unlined, and uncompacted burrows (omission suite) and are associated with rare highly abraded and fragmented shell remains.     

Cope's rule and the adaptive landscape of dinosaur body size evolution

The largest known dinosaurs weighed at least 20 million times as much as the smallest, indicating exceptional phenotypic divergence. Previous studies have focused on extreme giant sizes, tests of Cope's rule, and miniaturization on the line leading to birds. We use non‐uniform macroevolutionary models based on Ornstein–Uhlenbeck and trend processes to unify these observations, asking: what patterns of evolutionary rates, directionality and constraint explain the diversification of dinosaur body mass? We find that dinosaur evolution is constrained by attraction to discrete body size optima that undergo rare, but abrupt, evolutionary shifts. This model explains both the rarity of multi‐lineage directional trends, and the occurrence of abrupt directional excursions during the origins of groups such as tiny pygostylian birds and giant sauropods. Most expansion of trait space results from rare, constraint‐breaking innovations in just a small number of lineages. These lineages shifted rapidly into novel regions of trait space, occasionally to small sizes, but most often to large or giant sizes. As with Cenozoic mammals, intermediate body sizes were typically attained only transiently by lineages on a trajectory from small to large size. This demonstrates that bimodality in the macroevolutionary adaptive landscape for land vertebrates has existed for more than 200 million years.     

Palaeoecology of the mid‐Cretaceous siphonate bivalve genus Goshoraia (Mollusca,Veneridae) from Japan

Abstract: The mid‐Cretaceous bivalve Goshoraia Tamura, 1977, endemic to Japan, is an early example of shallow‐marine siphonate bivalves of the family Veneridae Rafinesque, 1815. Three species, including one new, are here described: Goshoraia minor Tashiro and Kozai, 1989 (Aptian), G. crenulata (Matsumoto, 1938; Albian–lower Cenomanian) and G. maedai sp. nov. (middle to ?upper Cenomanian). The habitats of Goshoraia have been extensively compared with those of common Cretaceous, nonsiphonate burrowers, such as trigoniids, which range from tidal flat and shoreface to shelf environments. Depth of burial, which can be estimated from the extent of the pallial sinus, increases from the ancestral G. minor to its descendants G. crenulata and G. maedai sp. nov., documenting that the ability to burrow within this genus improved in time. These morphological and palaeoecological changes may be related to the Mesozoic marine revolution during the mid‐Cretaceous.     

Ichnology of the Winnipeg Formation,southeast Saskatchewan: a glimpse into the marine infaunal ecology of the Great Ordovician Biodiversification Event

The ichnology of the Middle Ordovician Winnipeg Formation has been analysed based on the study of cores from five wells drilled in southeast Saskatchewan (Canada). Six sedimentary facies, ranging from upper shoreface to lower offshore settings in a shallow‐marine environment, have been characterized. Ichnological attributes are consistent with those in currently proposed models for shallow‐marine wave‐dominated settings, but ichnodiversity is lower than in post‐Palaeozoic settings. Low ichnodiversity in the Winnipeg Formation most likely reflects evolutionary factors rather than environmental controls. Interestingly, low‐energy, distal deposits of the Winnipeg Formation display intense degree of bioturbation, reflecting a well‐developed mixed layer and underscoring the importance of the Great Ordovician Biodiversification Event in terms of sediment mixing.     

Ichnological analysis of Jurassic shallow to marginal marine deposits: example from Wagad Highland,Western India

Abstract

Jurassic deposits of shallow to marginal marine (delta) environments are widely reported from different continents of the world. This study shows inter-relationship of the animal-sediment behaviours in shallow and marginal marine conditions, suggesting an interpretation of the possible ichnodisparity. The Jurassic succession exposed at Washtawa Dome and Adhoi Anticline of Wagad highland, Kachchh comprises an approximately 341 m thick succession, divided into two formations – Lower Washtawa and Upper Wagad Sandstone. Eight sparsely to highly bioturbated sedimentary units show twenty-three identifiable ichnospecies from fifteen ichnogenera representing five ichnoassemblages broadly attributable to the Skolithos and the Cruziana ichnofacies, and developed in shallow-marine strandplain shoreface and delta depositional facies. The relative frequency statistical data reveals the dominant occurrence of feeding structures generated by polychaetes preferentially in quartz arenites. These structures represent sub-horizontal, sub-vertical and complex burrows, and show twelve and six categories of architectural designing Callovian-Oxfordian of shallow-marine shoreface and Oxfordian-Kimmeridgian shallow-water delta successions, respectively. The lower ichnodiversity and ichnodisparity associated with the Oxfordian-Kimmeridgian deltaic intervals represents a decrease in the exploitation of under-used ecospace, due to unfavourable environmental conditions rather than an expression of evolutionary radiation.     

Las cerradicas tracksite (Berriasian,Galve, Spain): Growing evidence for quadrupedal ornithopods

Dinosaur footprints occur in shallow marine sedimentary units of the Berriasian Villar del Arzobispo Formation in the Aliaga basin, NE Spain. Las Cerradicas is a small outcrop (25 m²), near Galve, with four dinosaur trackways. Three tridactyl trackways indicate bipedal animals, and have parallel orientation. A fourth or‐nithopod trackway indicates a quadrupedal animal and is the smallest among any reported in the literature (L = 23 cm, W = 23 cm of pes tracks). It has manus prints that are oval‐shaped impressions. These and other recent discoveries shed much light on the abundance of quadrupedal ornithopods during the early Cretaceous.     

Spatial niche partitioning in dinosaurs from the latest cretaceous (Maastrichtian) of North America

We examine patterns of occurrence of associated dinosaur specimens (n = 343) from the North American Upper Cretaceous Hell Creek Formation and equivalent beds, by comparing their relative abundance in sandstone and mudstone. Ceratopsians preferentially occur in mudstone, whereas hadrosaurs and the small ornithopod Thescelosaurus show a strong association with sandstone. By contrast, the giant carnivore Tyrannosaurus rex shows no preferred association with either lithology. These lithologies are used as an indicator of environment of deposition, with sandstone generally representing river environments, and finer grained sediments typically representing floodplain environments. Given these patterns of occurrence, we argue that spatial niche partitioning helped reduce competition for resources between the herbivorous dinosaurs. Within coastal lowlands ceratopsians preferred habitats farther away from rivers, whereas hadrosaurs and Thescelosaurus preferred habitats in close proximity to rivers, and T. rex, the ecosystem's sole large carnivore, inhabited both palaeoenvironments. Spatial partitioning of the environment helps explain how several species of large herbivorous dinosaurs coexisted. This study emphasizes that different lithologies can preserve dramatically dissimilar vertebrate assemblages, even when deposited in close proximity and within a narrow window of time. The lithology in which fossils are preserved should be recorded as these data can provide unique insights into the palaeoecology of the animals they preserve.     

Two new dinosaur tracksites from the Lower Cretaceous Jiaguan Formation of Sichuan Basin,China: specific preservation and ichnotaxonomy

Two new dinosaur tracksites are reported from the Lower Cretaceous Jiaguan Formation in the Sichuan Basin, Qijiang District of Chongqing. These are the Gaoqing-Yongsheng and the Huibu tracksites, which represent the 13th and 14th reports from this formation. The Gaoqing-Yongsheng tracksite reveals the trackway of a large biped (ornithopod) in association with isolated sauropod tracks and large indeterminate undertracks with radial cracks. These features are preserved as natural casts with pebble infillings in a coarse, cross bedded and very thick bedded sandstone sequence. The Huibu tracksite reveals isolated theropod tracks and ornithopod tracks, the latter having a quadripartite, Caririchnium-like morphology, preserved in a thin bedded sandstone sequence with intercalated mudstone.     

Early jurassic (Upper Pliensbachian) gastropods from the Herforder Liasmulde (Bielefeld, Northwest Germany)

An Early Jurassic (Upper Pliensbachian) gastropod fauna from the Herforder Liasmulde (Herford Lias Syncline) near Bielefeld, Northwest Germany is described. This is one of the first detailed and illustrated reports of Pliensbachian gastropods from this area. Sixteen species are reported. Surface collecting yielded relatively large vetigastropods (pleurotomarioids amd trochomorphs). Bulk samples yielded abundant small caenogastropods (especiallyLevipleura blainvillei andKalchreuthia frankei) and cylindrobullinid opisthobranchs (e.g.Cylindrobullina dornend). These small species are also abundant in the Pliensbachian of South Germany (N Bavaria, Franconia). Therefore, this characteristic Pliensbachian microgastropod assemblage was widespread in Germany and probably also in other comparable marine deposits of Central Europe (e.g. the Paris Basin).      

An enigmatic early mesozoic dinosaur trackway from Zimbabwe

A trackway from Zimbabwe of probably the smallest dinosaur footprints recorded in Africa, is described and tentatively assigned to the Early Jurassic. The footprints are possibly those of a theropod and show strong negative (outward) rotation of the pes and are associated with manus prints. The shape of the footprints, unusual negative rotation, posterior curvature of digit IV and curious positioning of the manus prints in relation to the pes are enigmatic but somewhat reminiscent of Atreipus. Although a number of propositions are considered the most likely is that the animal was an immature dinosaur using a quadrupedal gait. A second trackway of slightly larger footprints of a bipedal theropod dinosaur is also recorded along with other diminutive tracks that suggest an early dinosaur assemblage, possibly dating from near the Trias‐sic‐Jurassic boundary.     

Reworked marine sandstone concretions: a record of high-frequency shallow burial to exhumation cycles

Concretions, with abundant calcite-dolomite cement-replacement textures originally hosted in shallow-marine sandstones, were reworked into Lower Cretaceous fluvio-deltaic conglomerates and shoreface sandstones (External Zones, Betic Cordillera). A cycle of host sand deposition, early diagenetic concretion formation and concretion reworking is documented: (1) Well-sorted shoreface sandstone deposited. (2) Spherical to ovoid, non-ferroan calcite-cemented concretions formed below flooding surfaces at shallow-burial depths during early eodiagenesis. Non-ferroan calcite cements were precipitated from the bicarbonate derived from seawater and from dissolution of marine bioclasts, as shown by isotope analyses. (3) Concretions were reworked and exposed on the seafloor in a high-energy setting as indicated by the presence of numerous bivalve borings (Entobia ichnofacies), laminated micritic microbial crusts around the concretions, and epilithobionts (oysters, barnacles and corals) on the concretion surface. Concretions also appear as erosional remnants on the floor of channels which were incised into the shoreline sandstone when sea-level fell. (4) The fluvio–deltaic channels were filled with sediment during flooding in the late lowstand of sea-level. (5) The concretions are partly dolomitized, and the presence of siderite, pyrite and barite in the outer part of the concretions precipitated before the dolomite, suggests that the latter formed during shallow burial.     

A late Pleistocene progradational clastic shoreface succession in Jamaica: Implications for the preservation potential of the echinoid Leodia

A section in the Late Pleistocene Port Morant Formation of Jamaica shows a progradational deltaic succession passing from offshore muddy sands, through shoreface to foreshore deposits. The transition zone/lower shoreface has abundant Ophiomorpha burrows and contains common examples of the echinoid Leodia cf. sexiesperforata (Leske). Modern Leodia occur in shallow marine carbonate sands, and the Port Morant occurrence is the first record of abundant Leodia in the geological record. Despite their strong test construction that should give Leodia a high preservation potential, these echinoids have a poor fossil record because the environments in which they lived are rarely preserved. Consequently, the fossil record is biased towards species that occur in environments with high preservation potential.     

The First Dinosaur from Washington State and a Review of Pacific Coast Dinosaurs from North America

We describe the first diagnostic dinosaur fossil from Washington State. The specimen, which consists of a proximal left femur, was recovered from the shallow marine rocks of the Upper Cretaceous (Campanian) Cedar District Formation (Nanaimo Group) and is interpreted as pertaining to a large theropod on the basis of its hollow medullary cavity and proximally placed fourth trochanter. The Washington theropod represents one of the northernmost occurrences of a Mesozoic dinosaur on the west coast of the United States and one of only a handful from the Pacific coast of Laramidia during the Cretaceous. Its isolated nature and preservation in marine rocks suggest that the element was washed in from a nearby fluvial system. If the femur pertains to a tyrannosauroid, which seems likely given its size and the widespread occurrence of the group across Laramidia during Late Cretaceous times, then it would represent an earlier occurrence of large body size than previously recognized (complete femur length estimated at 1.2 meters). Uncertainty surrounding the latitude of deposition of the Nanaimo Group (i.e., the Baja-British Columbia hypothesis) precludes assigning the Washington theropod to either of the putative northern or southern biogeographic provinces of Laramidia.     

Patterns of diversity, depth range and body size among pelagic fishes along a gradient of depth

Studies of geographical patterns of diversity have focused largely on compiling and analysing data to evaluate alternative hypotheses for the near‐universal decrease in species richness from the equator to the poles. Valuable insights into the mechanisms that promote diversity can come from studies of other patterns, such as variation in species distributions with elevation in terrestrial systems or with depth in marine systems. To obtain such insights, we analysed and interpreted data on species diversity, depth of occurrence and body size of pelagic fishes along an oceanic depth gradient. We used a database on pelagic marine fishes native to the north‐east Pacific Ocean between 40°N and 50°N. We used data from the Pacific Rim Fisheries Program that were obtained from commercial, management and scientific surveys between 1999 and 2000. Depth of occurrence and maximum body length were used to assess the distributions of 409 species of pelagic fishes along a depth gradient from 0 to 8000 m. A presence–absence matrix was used to classify the depth range of each species into 100‐m intervals. Atmar & Patterson's (1995 ) software was used to quantify the degree of nestedness of species distributions. Pelagic fish species diversity decreased steeply with increasing depth; diversity peaked at less than 200 m and more than half of the species had mean depths of occurrence between 0 and 300 m. The distribution of species showed a very strong nested subset pattern along the depth gradient. Whereas species with narrow ranges were generally restricted to shallow waters, wide‐ranging species occurred from near the surface to great depths. The relationship between maximum body size and mean depth range differed between teleost and elasmobranch fishes: being positive for teleosts, but negative for elasmobranches. Results support hypotheses that some combination of high productivity and warm temperature promote high species diversity, and reject those that would attribute the pattern of species richness to the mid‐domain effect, habitat area, or environmental constancy. The data provided a clear example of Rapoport's rule, a negative correlation between average depth range and species diversity.     

Osteology of Barapasaurus tagorei (Dinosauria: Sauropoda) from the Early Jurassic of India

Abstract: The sauropod dinosaur, Barapasaurus tagorei, is known from the Early Jurassic Kota Formation (Sinemurian to Pliensbachian) of India. The taxon is represented by c. 300 bones that were found associated with large fossilized tree trunks and were collected from the interface of sandstone and mudstone units covering an area of c. 276 m². The collection includes one partial skeleton; most of the remainder of the bones were disarticulated, disassociated and dispersed, but taphonomic analysis permits recognition of associated elements comprising several individuals. Skeletal anatomy of Barapasaurus includes several teeth, vertebrae from the caudal cervicals rearward to the terminal caudals, and most elements of the appendicular skeleton. Barapasaurus is characterized by spoon‐shaped teeth with bulbous bases and grooves on the anterolabial and posterolingual sides of the crown, coarse tubercles on the carina, acamerate cranial and dorsal vertebrae, lateral laminae of the middle and caudal dorsal neural spines composed of spinodiapophyseal and spinopostzygapophyseal laminae, neural canal of the mid‐dorsal vertebrae opens dorsally through a narrow slit into a large cavity and sacrum with four co‐ossified vertebrae. Phylogenetic analysis reveals that Barapasaurus is basal in comparison with Vulcanodon and is removed from Eusauropoda.     

Benthic foraminifers and paleoecology of a Holocene shelly concentration, Salado Basin, Argentina

Foraminiferal fossil assemblages of the shelly concentration, which represents the type section of Cerro de la Gloria Member of Las Escobas Formation, were analyzed for the first time. Taxonomic, quantitative and taphonomical analyses were made in order to obtain paleoenvironmental (physical as well biological) information. The complexity of the internal structure of the taphocoenoses was analyzed to infer the history of the final concentration process. The shell bed of Channel 15 corresponds to a shoreface longshore bar deposited in a brackish, unstable, wave-dominate coast. Shoreface and beach (foreshore) regressive facies were recognized. Taphonomic processes have modified the paleobiocoenoses by the selective preservation of autochthonous elements and by the addition of parautochthonous fauna from relict beachs and lagoons. Thus, the taphocoenoses is a within-habitat time-averaged assemblage composed of species that inhabit shallow shelf marine environments. Discrimination of autochthonous and parautochthonous fauna was possible based on taphonomic signatures of tests. The addition of the parautochthonous elements was related with longshore currents and littoral drift, and with high-energy events, probably with storm-waves, when erosion of the Pre-Mid Holocene substrate was more intense. Thus, the contribution of parautochthonous fauna is directly related with lithology and therefore, with dynamic of the paleoenvironment: in the shoreface, autochthonous fauna dominates in clastic sands with lamination and parallel stratification, whereas parautochthonous elements dominate in shoreface shelly gravels and in the foreshore sands. In the upper part of the section (beach facies), mainly parautochthonous elements related with erosion of the Pre-Mid Holocene substrate was recognized, since the shoreface was only periodically affected by marine processes, i.e., during storms.