New Evidence for a Cretaceous Age for a Mesozoic Nonmarine Bivalve Assemblage from Paekto-dong, Sinuiju City, The Democratic People’s Republic of Korea

The Sinuiju Formation in Paekto-dong, Sinuiju City in the Democratic People's Republic of Korea has yielded Mesozoic nonmarine bivalve fossils, which is the first occurrence of such in the DPRK. Based on these fossil specimens, a new Cretaceous bivalve assemblage, the Arguniella yanshanensis-Sphaerium anderssoni Assemblage is erected. This assemblage includes Arguniella yanshanensis, A. lingyuanensis and Sphaerium anderssoni and can be compared with the Jehol Biota. The age of the Sinuiju Formation is also clarified and on the basis of the bivalves and the presence of a Eosestheria–Ephemeropsis–Lycoptera(E–E–L) assemblage, the formation is not Upper Jurassic, but Lower Cretaceous in age.     

Paleoecology of Inoceramus amakusensis Nagao et Matsumoto, 1940 (Bivalvia) in a Late Cretaceous shallow clastic sea: The Himenoura Group,Kyushu, Japan

The taphonomic features and paleoecology of this species were investigated focused on vertically embedded individuals of articulated Inoceramus amakusensis Nagao et Matsumoto. In the Hinoshima Formation, Himenoura Group of Kyushu, Japan, this Santonian (Late Cretaceous) inoceramid bivalve characteristically occurs in incised-valley fill siliciclastic marine deposits. Modes of I. amakusensis occurrence and preservation, from in situ (= occurrence in life position) to allochthonous shell fragments, are strongly affected by its paleoecology and depositional environments. Several I. amakusensis (up to 25 cm in shell height) were recovered from bioturbated sandstones associated with storm-influenced deposits. Their commissural planes are almost perpendicular to the bedding plane, with the anterior face oriented downward and the posteroventral portion extending upward. Furthermore, I. amakusensis is morphologically comparable to endobyssate mytilid bivalves today. These results suggest that this Cretaceous species was an orthothetic sand sticker at least during mid-ontogeny that preferentially inhabited a well-oxygenated, nearshore seafloor. I. amakusensis was distributed in various depositional environments and has been regarded as a recliner in offshore muddy substrate. However, the present discovery suggests that it was also well adapted, with an upright life position, to high-energy shallow clastic environments characterized by high sediment supply.     

Untold muddy tales: Paleoenvironmental dynamics of a “barren” mudrock succession from a shallow Permian epeiric sea

During the late Paleozoic, the intracratonic Paraná Basin, Brazil, in central Gondwanaland, was covered by a huge (>1.600.000 km²), shallow and isolated epeiric sea. Within the Permian succession, oxygen-deficient facies are commonly recorded in the Mesosaurus-bearing Irati Formation (Cisuralian, Artinskian/Kungurian) and the overlaying Serra Alta Formation (Guadalupian, Wordian/Capitanian). Barren, dark-grey mudstones are the main facies preserved in this last unit, which has usually discouraged extensive and detailed stratigraphical and paleontological investigations. However, exhaustive sedimentological, taphonomic and paleontological surveys in those deposits reveal a dynamic and complex depositonal history. Based on sedimentary fabric, autochthonous to parautochthonous occurrences of shelly benthic invertebrates (bivalves) and the presence/absence of concretion-bearing and phosphate-rich layers, we report variations in the oxygen levels of bottom and pore waters, in bathymetry, sedimentation rates, and changes in benthic colonization. Our data indicate that the deposition of this “apparently barren” mudstone-dominated succession was driven by a complex interplay of variations in sedimentation rate and oxygen pulses tied to tectonic and climate changes. Three distinct populations or invertebrate paleocommunities were recorded, which were adapted to (a) normal background low-oxygen (dysoxic) conditions (i.e., minute infaunal suspension-feeding bivalves associated with the trace fossil Planolites), (b) chemically toxic (anoxic/extreme dysoxic) substrates, including gigantic burrowing bivalves (probable chemosymbiotic taxa), and (c) oxic/dysoxic substrates following short-term bottom disruptions.     

Taphonomy of a Baurusuchus (Crocodyliformes,Baurusuchidae) from the Adamantina Formation (Upper Cretaceous,Bauru Basin), Brazil: Implications for preservational modes,time resolution and paleoecology

Upper Cretaceous vertebrate accumulations from the Adamantina Formation are known due to their high taxonomic diversity. On the other hand, taphonomic analyses still are rare, limiting the understanding of processes related to the biostratinomic and fossildiagenetic histories of this lithostratigraphic unit. In 2005, fossils were collected from an outcrop located at Jales municipality, state of São Paulo, southeastern Brazil. From this outcrop, a well-preserved Baurusuchus was recovered, which displays a peculiar set of taphonomic signatures. This paper identifies and interprets taphonomic features of a specimen of Baurusuchus (Crocodyliformes, Baurusuchidae; UFRJ DG 418-R) from the Adamantina Formation (Upper Cretaceous of the Bauru Basin), in Jales municipality, state of São Paulo. Brief taphonomic comparisons with other specimens previously studied (crocodiles and dinosaurs) and a lithofaciological analysis of the outcrop were undertaken in order to enhance the knowledge of the stratigraphy and paleoenvironment and improve the time resolution for the Adamantina Formation in the region of Jales. Furthermore, paleoecological data were interpreted based on the taphonomic analysis.The fossil is composed of an articulated segment of vertebral column, ribs, part of the pelvic girdle and gastralia. There is no hydraulic equivalence between both the specimen of Baurusuchus and the size of quartz grain predominant in the fossiliferous layer, suggesting death in situ or short transport as a “water carcass”. Teeth marks identified on the pubes were assigned to a small/juvenile baurusuchid crocodyliform or a theropod dinosaur. The repositioning of some elements (ribs and dorsal osteoderms) is suggestive of mummification. Desiccation marks were observed and attributed to the stage 1 of weathering. These features suggest subaerial exposure of the carcass prior to burial, however, probably after the mummification. On the other hand, the subaerial exposure was short, because the individual was not fully disarticulated. Furthermore, the degrees of articulation and preservation of the specimen nullify the hypothesis of reworking.Lithofaciological and taphonomic analyses suggest a well-drained floodplain as the burial environment and an arid or semi-arid climate in the region of Jales outcrop. In addition, the taphonomic signatures seem to indicate a time resolution about 10⁰–10⁴ years for the layer where the crocodyliforms were collected, but it seems to have, within this time limit, temporal-mixing among terrestrial crocodiles and dinosaurs collected from the same layer, suggesting time-averaging in this outcrop.     

Fossil coniferous wood from the Early Cretaceous Jehol Biota in western Liaoning,NE China: New material and palaeoclimate implications

The Early Cretaceous Jehol Biota, one of the most important Mesozoic lagerstätten in East Asia, is especially well-known for occurrences of fossil feathered dinosaurs and early angiosperms. However, the terrestrial biodiversity, especially the fossil wood record, is poorly known. In this study, several structurally preserved coniferous wood specimens from the Lower Cretaceous Yixian Formation are investigated, based on collections from the Heichengzi Basin in Beipiao of western Liaoning, Northeast China. Four species referred to four genera of fossil wood are described, including Taxodioxylon heichengziense sp. nov., Thujoxylon beipiaoense sp. nov., Sciadopityoxylon liaoningense Ding and Protocedroxylon shengjinbeigouense sp. nov. These new records enlarge the fossil wood diversity of the Yixian Formation up to 10 species in 9 genera, and provide further insights into the forest vegetation composition of the Early Cretaceous Jehol Biota. Systematic analysis of the floral constitution indicates that the petrified forests of the Yixian Formation are dominated by conifers, represented by Araucariaceae, Podocarpaceae, Sciadopityaceae, Pinaceae and Cupressaceae in the western Liaoning region. Palaeoclimatical analysis of the fossil wood assemblage implies that the western Liaoning region was dominated by a cool temperate, wet and seasonal climate with variable interannual water supply in the western Liaoning region during the Early Cretaceous.     

Paleoecology of Inoceramus amakusensis Nagao et Matsumoto, 1940 (Bivalvia) in a Late Cretaceous shallow clastic sea: The Himenoura Group, Kyushu, Japan

The taphonomic features and paleoecology of this species were investigated focused on vertically embedded individuals of articulated Inoceramus amakusensis Nagao et Matsumoto. In the Hinoshima Formation, Himenoura Group of Kyushu, Japan, this Santonian (Late Cretaceous) inoceramid bivalve characteristically occurs in incised-valley fill siliciclastic marine deposits. Modes of I. amakusensis occurrence and preservation, from in situ (= occurrence in life position) to allochthonous shell fragments, are strongly affected by its paleoecology and depositional environments. Several I. amakusensis (up to 25 cm in shell height) were recovered from bioturbated sandstones associated with storm-influenced deposits. Their commissural planes are almost perpendicular to the bedding plane, with the anterior face oriented downward and the posteroventral portion extending upward. Furthermore, I. amakusensis is morphologically comparable to endobyssate mytilid bivalves today. These results suggest that this Cretaceous species was an orthothetic sand sticker at least during mid-ontogeny that preferentially inhabited a well-oxygenated, nearshore seafloor. I. amakusensis was distributed in various depositional environments and has been regarded as a recliner in offshore muddy substrate. However, the present discovery suggests that it was also well adapted, with an upright life position, to high-energy shallow clastic environments characterized by high sediment supply.     

First record of the beetle family Lasiosynidae (Insecta: Coleoptera) from the Lower Cretaceous of China

A new genus, Cretasyne gen. nov., in the family Lasiosynidae, with two species C. lata sp. nov. and C. longa sp. nov., is described from the Lower Cretaceous Yixian Formation of Inner Mongolia, China. These fossils are the first record of the family from the Yixian Formation and provide significant information on lasiosynid morphology and diversity. The fossil record of Lasiosynidae is also reviewed.     

Propeamussiidae,Inoceramidae, and other Bivalvia from the Lower Cretaceous Puez Formation (Valanginian–Cenomanian; Dolomites,South Tyrol,Italy)

A bivalve assemblage from the Lower Cretaceous Puez Formation at the type locality, Piz de Puez (Dolomites, South Tyrol, northern Italy) is described. Given the large amount of sedimentary rock screened during the course of this study, the <50 bivalves examined here, although occurring in very low abundance, are considered to represent a reasonably comprehensive sample. The assemblage provides insight into an autochthonous, Mesozoic, deep-water bivalve community, which was dominated by glass scallops. Two species are described as new, Parvamussium pizpuezense n. sp. and the giant P. mordsdrum n. sp. Presumably, they lived as epifaunal-reclining carnivores and preyed on various meiofauna, occupying a similar ecologic niche as their modern counterparts. Scarce epifaunal, suspension-feeding Inoceramidae entered only by occasional recruitment of larvae into an environment that is inferred to have been characterised by low levels of suspended nutrients.     

Bivalves and oncoids as palaeoenvironmental indicators at Late Jurassic and Early Cretaceous dinosaur sites from Spain

Bivalves from the Late Jurassic and Early Cretaceous stratigraphic section at Las Zabacheras (Galve Sub-basin Teruel, northern Spain), are reviewed from both systematic and palaeoautoecological perspectives. For this study the Villar del Arzobispo Formation, well known for important dinosaur occurrences, was sampled from the boundary with the underlying Higueruelas Formation (Late Jurassic), to the first levels of the overlying El Castellar Formation (Early Cretaceous). The bivalve taxa have Late Jurassic affinity, pointing to a possible Jurassic-Cretaceous boundary towards the top of the Villar del Arzobispo Formation. We have sampled oncoids, whose nuclei are bivalves, through the section to study environment change in this lithostratigraphical formation. Geochemical trace elements and δ¹³C and δ¹⁸O stable isotope analysis of the oncoids enable us to determine the conditions in which the microbialites were formed and provide further palaeoenvironmental data from the deposits containing the bivalves. Bivalve taxa change from the lower part of the Villar del Arzobispo Formation, where Ceratomya excentrica and Unicardium cf. subregulare are characteristic of marine conditions, becoming more continental towards the top of the formation with the presence of Unionoidean bivalves, and in the “Wealden” facies of the El Castellar Formation, where Teruella gautieri, has been found. Bivalves and oncoids allow us to recognize continental conditions where the first dinosaur of Spain, the sauropod Aragosaurus ischiatus was found, in an open water system, where there was limited evaporation, and with enough energy to produce well oxygenated water.     

On the Lower Cretaceous in Yixian County of Jinzhou City, Western Liaoning, China

Traditionally, the lacustrine deposits in Yixian County of Western Liaoning have been assigned to either “the Dakangpu Bed” of the Yixian Formation or the Jiufotang Formation. However, a 206Pb/238U age of 126.47±0.87 Ma is newly obtained from the tuff sample (06051) of the lacustrine deposits in the Baitaigou fossil site of Potaizi village, Yixian County, indicating that the lacustrine deposits in Potaizi area are approximately equivalent to the Wumingshan volcanics of the Sihetun Bed of the Yixian Formation in Beipiao. From our new dating data have arisen some new problems: Where could we find the Jiufotang Formation in Yixian County? How widely distributed is the Jiufotang Formation in Western Liaoning? Could the traditionally named Jiufotang Formation somewhere in Western Liaoning be the synchronous deposits of other litho-units (e.g. the Yixian Formation) in different facies? Could some lacustrine deposits somewhere in Western Liaoning have been assigned to the Jiufotang Formation?     

Upper Cretaceous depositional environments and bivalve assemblages of far-east Asia: the Himenoura Group, Kyushu, Japan

The depositional environments and bivalve assemblages are determined for the Upper Cretaceous Hinoshima Formation of the Himenoura Group, Kamishima, Amakusa Islands, Kyushu, Japan. The Hinoshima Formation is characterized by a thick transgressive succession that varies from incised-valley-fill deposits to submarine slope deposits with high aggradation rates of depositional systems. The incised valley is filled with fluvial, bayhead delta, brackish-water estuary, and marine embayment deposits, and is overlain by thick slope deposits.Shallow marine bivalves are grouped into five fossil assemblages according to species composition: Glycymeris amakusensis (foreset beds of a bayhead delta), Nippononectes tamurai (foreset beds of a bayhead delta), Ezonuculana mactraeformis–Nucula formosa (central bay), Glycymeris amakusensis–Apiotrigonia minor (slope), and Inoceramus higoensis–Parvamussium yubarensis (slope). These bivalve assemblages all represent autochthonous and parautochthonous conditions except for a Glycymeris amakusensis–Apiotrigonia minor assemblage found in debris flow and slump deposits. The life habitats of these bivalves and the compositions of the assemblages are discussed in terms of the ecological history of fossil bivalves of the mid- to Late Cretaceous.     

Systematic and taphonomic insights of fossilized feathers: A new occurrence from the Oligocene of Taubaté Basin (SE,Brazil)

Feathers are rare in the fossil record because they have a low fossilization potential. Despite their palaeobiological significance, they also provide important palaeoecological and taphonomic information. Here, we report a new occurrence of three isolated feathers from the shales of the Oligocene Tremembé Formation (Taubaté Basin, SE Brazil). Their possible taxonomic affinities and taphonomic features are also discussed. Analyses identified the specimens as representatives of two pennaceous morphotypes (i.e., a contour and a rectrice feather). Both are preserved as carbonized traces, although, due taphonomic processes, they show different degrees of preservation. Since the Tremembé Formation is responsible for the most diverse record of Cenozoic birds, and because water-adapted birds (e.g., anseriformes and phoenicopteriformes) occur in this unit, it is highly possible that these feathers belonged to these aquatic taxa. Further investigations should concentrate on geochemical and microscopic techniques in order to reveal additional taxonomic and paleoecological features currently unknown in Paleogene birds of Brazil.     

Late Cretaceous (Campanian/Maastrichtian) freshwater to restricted marine mollusc fauna from the Loncoche Formation,Neuquén Basin,west-central Argentina

This study is the first detailed account of freshwater to restricted marine molluscs from the Upper Cretaceous sedimentary rocks in the northern sector of the Neuquén Basin. The fossils are from the Campanian–Maastrichtian Loncoche Formation in southern Mendoza, west-central Argentina, which records the initial connection of the Neuquén Basin to the Atlantic Ocean. Six species of bivalves (Diplodon bodenbenderi, Pleiodon? sp., Isognomon? mechanquilensis, Mactridae? indet., Panopea? sp., and Laternula sp.) and three of gastropods (Paleoanculosa macrochilinoides, Paleoanculosa ameghiniana, and a possible cerithioidean) are described. Specimens were collected from fine to coarse sandstones, which may be massive or with planar stratification, planar-cross stratification or trough-cross stratification, and a few from bioclastic limestones and mudstones. Although the sections are from 50 to 300 m thick, the specimens are found only in the lower 120 m. Molluscs represent autochthonous/parautochthonous assemblages composed of mostly non-broken gastropods and articulated bivalve specimens, some of which show signs of postmortem transport; however, they were not removed far from their original habitat. Review of the habitats of living genera supports the inference of dominantly freshwater palaeoenvironments in the lower and middle part of the Loncoche Formation, with restricted marine influence in the southernmost localities studied where there are a few samples that contain specimens belonging to predominantly marine groups (e.g., Laternula, Panopea).     

Probable tsunami origin for a Shell and Sand Sheet from marine ponds on Anegada, British Virgin Islands

A distinctive Shell and Sand Sheet found beneath the marine ponds of Anegada, British Virgin Islands, was formed by a post-1650 AD overwash event, but its origin (tsunami or hurricane) was unclear. This study assesses the taphonomic characters of the shell and large clast material (>2?mm) to determine its provenance and origin. Pond-wide stratigraphic units (Shelly Mud, Shell and Sand Sheet, Mud Cap) were analyzed (12 samples) at four sites in Bumber Well and Red Pond along with eight samples from the Shell and Sand Sheet in a 2-km transect of Bumber Well. Mollusks in the pond muds include Anomalocardia spp. and cerithids with no allochthonous shells from the offshore reef-flat. Results show that the shells and clasts (>2?mm) are derived from the erosion and winnowing of the underlying Shelly Mud of the former marine pond, forming a distinctive sheet-like deposit with Homotrema sand. The Shell and Sand Sheet contains articulated Anomalocardia bivalves and moderate numbers of angular fragments (approximately 35%) that are likely from crab predation. Radiocarbon dates of articulated Anomalocardia specimens from the Shell and Sand Sheet range widely (approximately 4000?years), with shell condition (pristine to variably preserved) showing no correlation with age. The articulated condition of the bivalves with the wide-ranging dates suggests erosion and winnowing of the underlying Shelly Mud but minimal transport of the bivalves. The Shell and Sand Sheet has taphonomic characteristics indicative of a widespread tsunami overwash (sheet-like extent and articulated specimens) but lacks allochthonous reef-flat shells. Reef-flat shell material may not have penetrated the pond, as a tsunami would have to cross the reef-flat and overtop high dunes (2.2?m) hindering transport of larger shell material but allowing the Homotrema sand to penetrate. Processes including hurricane overwash, pond wave action, or tidal channel opening and closure are not favoured interpretations as they would not produce extensive sheet-like deposits. Taphonomic analysis is hampered by the limited (400?C500?years BP) depositional history from Anegada??s ponds and the lack of comparative data from other Caribbean locations.     

Solemys (Chelonii,Solemydidae) remains from the Maastrichtian of Pyrenees: evidence for a semi-aquatic lifestyle

We report on a turtle from the Mina Esquirol site (Vallcebre basin), a new locality of early Maastrichtian age in the south-eastern Pyrenees. Fossils were located in the basal Tremp Formation, which was deposited in a littoral marsh. The material consists of a cast of a carapace including peripheral fragments and partial neural plates. The carapace exhibits a vermiculate ornamentation that is characteristic of genus Solemys and a histological bone structure similar to that of terrestrial taxa. However, taphonomic data indicates little transport and a short biostratinomic history, whereas palaeontological and sedimentological context indicates that the specimen was preserved in a shallow brackish water environment. Based on this taphonomic and sedimentological evidence, we suggest that at least some species of genus Solemys had a lifestyle similar to extant fresh or brackish water turtles (terrapins) and that the histological evidence alone for a terrestrial lifestyle is misleading.     

Functional morphology of Grammatodon inaequivalvis (Goldfuss) and implications for evolutionary pathways in arcoidean bivalves

Secondary soft-bottom dwellers evolved several times in the Arcoida. These include semi-infaunal endobyssate taxa and free-burrowing species. The Jurassic arcoid bivalve Grammatodon inaequivalvis (Goldfuss, 1837) is remarkable for showing different sculptures on its left and right valve. A functional analysis of the shell points to a reclining mode of life on soft bottoms. This interpretation is corroborated by the occurrence of this species in very fine-grained sediments, and by taphonomic patterns such as “butterflied” preservation. It is proposed here that this species was resting on its left valve on the sediment, probably without byssal attachment. This reclining mode of life of G. inaequivalvis was hitherto undescribed from soft-bottom dweller arcoid bivalves.     

Stratigraphy of the Triassic?Jurassic Boundary Successions of the Southern Margin of the Junggar Basin, Northwestern China

The Triassic?Jurassic (Tr?J) boundary marks a major extinction event, which (~200 Ma) resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr?J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key-species and abundance of spores and pollen, three zones were erected: the Late Triassic (Rhaetian) Aratrisporites?Alisporites Assemblage, the Early Jurassic (Hettangian) Perinopollenites?Pinuspollenites Assemblage, and the Sinemurian Perinopollenites?Cycadopites Assemblage. The Tr?J boundary is placed between bed 44 and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds with Ferganoconcha (?), Unio?Ferganoconcha and Waagenoperna?Yananoconcha bivalve assemblages are recognized. The Ferganoconcha (?) bed is limited to the upper Haojiagou Formation, Unio?Ferganoconcha and Waagenoperna?Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algae Tasmanites and the marine?littoral facies bivalve Waagenoperna from the Badaowan Formation indicate that the Junggar Basin was influenced by sea water caused by transgressions from the northern Tethys, during the Sinemurian.