A new species of Platanus from the Cenomanian(Upper Cretaceous) in eastern Heilongjiang,China

The stratigraphic division and sequence of the Upper Cretaceous sediments in eastern Heilongjiang Province,China,have been ambiguous and controversial,mainly due to a lack of biostratigraphically useful fossils and related radiometric dating.A new species of angiospermous fossil plant.Platanus heilongjiangensis sp.nov.,from Qitaihe in eastern Heilongjiang has been found in sediments conformably above which zircons from a rhyolitic tuff has been dated by U-Pb radiometric methods as 96.2± 1.7 Ma.indicating that the Upper Houshigou Formation is of Cenomanian age.This discovery not only provides new data to improve our stratigraphic understanding of the Houshigou Formation,but also shows that Platanus flourished in the early Late Cretaceous floras of the region.This new study also indicates active volcanism taking place in the eastern Heilongjiang region during the Cenomanian of the Late Cretaceous.     

Lamniform sharks from the Cenomanian (Upper Cretaceous) of Venezuela

Sampling of Cenomanian fossil-rich horizons within the La Luna Formation of two localities in the Zulia and Trujillo states (northern Venezuela) yielded numerous shark teeth belonging to various species within the order Lamniformes (Mackerel sharks). Twelve lamniform species were identified including three new species (Squalicorax lalunaensis sp. nov., Squalicorax moodyi sp. nov., Acutalamna karsteni gen. et sp. nov.) and the genus Microcarcharias gen. nov. is proposed to accommodate with the peculiar morphology of the small-sized odontaspidid M. saskatchewanensis. Other taxa reported here include Cretoxyrhina mantelli, Cretolamna sp., cf. Nanocorax sp. and five Squalicorax species left in open nomenclature. This is the first report of chondrichthyans from the mid-Cretaceous of Venezuela and one of the few records of this group from the Cenomanian of South America. The composition of these assemblages suggests some degree of endemism in the La Luna Sea but also possible connexions with the Western Interior Seaway. One of the most striking features of these assemblages is the high anacoracid diversity (eight species) despite the corresponding outer shelf/upper slope palaeoenvironments of the La Luna Formation. The high diversity of these opportunistic predators is probably related to the high diversity of medium to large marine vertebrates that provided food resources.     

Cenomanian Turrilitidae (Cretaceous heteromorph ammonites) from the Koppeh Dagh,northeast Iran: Taxonomy and stratigraphic implications

Early and early middle Cenomanian turrilitid ammonoids from the upper part of the Albian–Cenomanian Aitamir Formation of the Koppeh Dagh (northeast Iran) are described, illustrated and placed in an integrated stratigraphic context. The Aitamir Formation represents a graded siliciclastic shelf system and the turrilitid faunas comprise eight different species. Representatives of Mariella and Hypoturrilites have been recorded from a lower Cenomanian horizon in the Ghorghoreh section, corresponding to the Mantelliceras mantelli ammonite biozone. Mariella bicarinata (Kner, 1852) and H. wiedmanni Collignon, 1964 are recorded for the first time from Iran and the larger palaeobiogeographical area, respectively. The horizons with Turrilites costatus and T. scheuchzerianus at Taherabad can be dated as early middle Cenomanian Acanthoceras rhotomagense Zone, T. costatus Subzone. Concentrations of ammonoids commonly occur above regressive sandstone units, at the transition into overlying deeper marine shale units and in their lower parts, respectively. Such intervals represent the early transgressive systems tract of depositional sequences and may thus be regarded as early transgressive, slightly condensed shell accumulations. The uppermost lower to lower middle Cenomanian succession at Taherabad is of striking bio-, event- and sequence stratigraphic similarity to contemporaneous sections in northwest Europe. It reflects deposition during falling and low sea-level associated with the latest early Cenomanian unconformity SB Ce 3 as well as the pulsating transgressive development during the early middle Cenomanian, including levels correlative to the arlesiensis, primus and Mid-Cenomanian events in northwest Europe.     

Sequence stratigraphy of the Mancos Shale,lower Tres Hermanos Formation,and coeval middle Cenomanian to middle Turonian strata,southern New Mexico,USA

Sequence stratigraphic analysis of four widely spaced outcrops of middle Cenomanian to middle Turonian strata deposited in the Western Interior foreland basin in southern New Mexico, USA, defines ten sequence boundaries in a marine shale‐rich interval ca 200 m thick. The majority of sequence boundaries are based on basinward shifts in lithofacies characterized by either a non‐Waltherian contact between distal‐bar or lower shoreface sandstone and underlying lower offshore shale, or an erosional contact between distal‐bar or lower shoreface sandstone and underlying upper offshore shale. The sequence boundaries commonly correlate basinward to packages of storm‐deposited sandstone and to beds of sandy grainstone composed of winnowed inoceramid shell fragments. In several cases, however, the sequence boundaries pass basinward into presumably conformable successions of lower offshore shale. Maximum flooding surfaces within the sequences are represented by one or more beds of locally phosphatized globiginerid wackestone and packstone or exist within a conformable succession of lower offshore shale. Following initial south/south‐westward transgression into the study area, the regional trend of palaeoeshorelines was north‐west to south‐east, although isopach data indicate that lobes of sandstone periodically spread south‐eastward across the study area. The ten sequences in the study area are arranged into a third‐order composite megasequence that is characterized by overall upward‐deepening followed by upward‐shallowing of sequences. The composite megasequence is similar but not identical to the previously established T‐1 transgression and R‐1 regression in New Mexico. Based on radioisotopic dates of bentonites, the average frequency of the sequences within the study area was ca 327 kyr, which is consistent with fourth‐order cycles of ca 400 kyr interpreted in coeval marine strata elsewhere in the world.     

A new genus of Tanyderidae (Insecta: Diptera) from Myanmar amber,Upper Cretaceous

A new genus and species, Similinannotanyderus lii gen. et sp. nov., is described from Myanmar amber. It differs from other genera of Tanyderidae based on special characters of wing venation and male genitalia. This new taxon broadens the diversity of Tanyderidae in the Cretaceous, and its morphological characters enhance our understanding of the development and evolution of the primitive crane flies.     

Permian (Leonardian) brachiopods from Paso Hondo Formation,Chiapas, southern Mexico. Paleobiogeographical implications

One of the most important marine sequences of calcareous rocks from the Paleozoic of Mexico outcrops in southern Chiapas. It is composed by different units from Early Permian, being the Paso Hondo Formation the youngest with a Leonardian age. Different groups of marine invertebrates as corals, bivalves, gastropods, bryozoans, brachiopods and crinoids have been previously reported of this unit. Five brachiopod species of the orders Productida, Athyridida, Spiriferida and Spiriferinida from the Barrio Allende section of this unit are herein described. The new species Dyoros (Lissosia) maya and Hustedia shumardi are proposed. Sedimentology and paleoecology of the Paso Hondo Formation, suggest a well-lighted shallow lagoon environment with continuous terrigenous input. The subgenus Dyoros (Lissosia), the genus Paucispinifera and the species Hustedia shumardi, Spiriferella propria and Spiriferellina tricosa are typical taxa from Permian localities of Texas, New Mexico and Coahuila. Their presence in the studied area suggests that during Early Permian there was a geographic connection between the different localities of the biotic Grandian Province (southern USA, northern Mexico and Venezuela) and southeastern Chiapas.     

Reappraisal of Fresnosaurus drescheri (Plesiosauria; Elasmosauridae) from the Maastrichtian Moreno Formation,California, USA

The elasmosaurid Fresnosaurus drescheri, Welles from the contact between the Tierra Loma/Marca members of the Moreno Formation (Maastrichtian), California, USA is reviewed. Most of the features included in Welles's original diagnosis are considered related only to the juvenile ontogenetic stage of the holotype and only specimen. The new diagnosis is based on diagnostic characters of the ilia, including long rectangular shaped sacral facets located in the dorsal part of the shaft, two gentle knobs in the shafts and unexpanded dorsal end. Additional material from the Moreno Formation (numbered under the same number as the F. drescheri holotype but not mentioned by Welles and therefore considered part of a different specimen) are described for the first time. The latter are referred to the aristonectine, being the first evidence of aristonectines from the North Hemisphere.     

First pachycephalosaurid (Dinosauria: Ornithischia) from the Frenchman Formation (upper Maastrichtian) of Saskatchewan,Canada

Compared to earlier representatives of the family, pachycephalosaurids are less well known from upper Maastrichtian deposits around the world. Here, we report on a nearly complete left postorbital attributable to the pachycephalosaurid Sphaerotholus cf. Sphaerotholus buchholtzae from the upper Maastrichtian Frenchman Formation of Saskatchewan. This marks a probable northern range extension for the species into Canada, and the first occurrence of a pachycephalosaurid from this formation. We further demonstrate the taxonomic distinction between Stegoceras edmontonense and S. buchholtzae, which has been debated, based on postorbital sutural proportions. The northerly occurrence of Sphaerotholus cf. S. buchholtzae is consistent with the hypothesis of low beta diversity during the late Maastrichtian of North America, and its high stratigraphic incidence documents the persistence of non-pachycephalosaurin pachycephalosaurines in a critical interval for understanding the end-Cretaceous mass extinction event.     

Further evidence of marine Cenomanian,lower Turonian and Maastrichtian in the Upper Benue basin of Nigeria (West Africa)

Field investigations in the Upper Benue rift basin of Nigeria highlight the necessity for a review of the Cenomanian-Turonian biostratigraphy of the area. Three ammonite zones of Vascoceras bulbosum (Reyment), Paravascoceras costatum (Reyment) and Pseudotissotia (Bauchioceras) nigeriensis (Woods) have been recognized at sections exposed at the quarry of the cement factory near the village of Ashaka. The sediments within the Vascoceras bulbosum zone also contain specimens of Exogyra olisiponensis (Sharpe), Kanabiceras septemseriatum (Cragin) and Epengonoceras dumbli (Cragin). These are all indicative of an uppermost Cenomanian age and reveal that at least the lower portion of the Gongila Formation as exposed at Ashaka is faunistically equivalent to the Pindiga Formation as exposed in the type section at Pindiga.The shales in the Gombe region in which Libycoceras ismaeli (Zittel) was found are probably part of the Maastrichtian Fika shales outcropping extensively in the northern part of the area. The discovery of Cyclolithes nov. sp. within Gombe sandstones at Dakiti near Kumo confirm that they are at least partially marine in origin and Maastrichtian in age. This could be considered as an additional evidence in favour of the presence of marine waters in the Upper Benue during the last part of the Cretaceous.     

The carinate bird Ichthyornis from the Upper Cretaceous of Mexico

A well-preserved right humerus collected from the upper Austin Group at Ejido Piedritas in Coahuila, Mexico is referable to the carinate bird Ichthyornis. This occurrence extends the known distribution of Ichthyornis to the southwest, and is among a younger (Coniacian-Campanian) group of specimens, recovered generally to the south of older (Cenomanian-Turonian) Ichthyornis specimens. The southward shift in occurrence of Ichthyornis may accord with the withdrawal of subtropical marine biota from the Western Interior Seaway of North America during the Late Cretaceous.     

New abelisaurid remains from the Anacleto Formation (Upper Cretaceous), Patagonia,Argentina

New theropod remains with abelisaurid affinities from the Upper Cretaceous (Anacleto Formation, lower Campanian), NW Patagonia, Argentina, are here described. The specimen (MPCN-PV 69) consists of a partial premaxilla, fragmentary vertebrae, proximal portion of both humeri, distal portion of the pubis, and an incomplete pedal ungual. Characters linking with Abelisauridae are a premaxilla with a subquadrangular body, externally ornamented, and paradental plates with a striated surface; and humerus with bulbous proximal head, conical internal tuberosity, and reduced greater tubercle. The humerus is similar to those of Carnotaurus and Aucasaurus, due to the presence of a bulbous head and a discontinuity between the head and the internal tuberosity, but also differs from both taxa in the more distal location of the greater tubercle with respect to the internal tuberosity. Aucasaurus also comes from Anacleto Formation, but differences in the humeri suggest that MPCN-PV 69 is a different taxon. The phylogenetic analysis performed supports the affiliation to Abelisauridae, but fails to determinate a more precise relationship with others abelisaurids. However, a majority rule consensus of the analysis shows a position within Brachyrostra. Despite being fragmentary, MPCN-PV 69 probably represents a new abelisaurid from the Anacleto Formation, thus increasing the knowledge and diversity of Late Cretaceous South American abelisaurids.     

松辽盆地东南隆起区上白垩统嫩江组泥页岩段地球化学特征与物源分析

嫩江组泥岩的地球化学分析结果表明:泥岩中含有一定量的铁镁质组分和较多的稳定组分。微量元素和稀土元素分析结果显示,嫩江组含油页岩段沉积时期存在多个物源。CIA和PIA值没有随着埋深的减少而增加,说明嫩江组泥岩受后期风化影响很小。CIA值为70.5~77.0,Th/U值为2.67~3.98,说明泥岩源区经历了中等强度风化作用。Zr/Sc—Th/Sc图解表明泥岩的化学成分受源岩成分控制。通过源岩和构造背景判别图以及前人资料可知,松辽盆地嫩江组母岩主要为海西期花岗岩,源岩的构造背景为大陆边缘造山带火山岛弧岩系。物源中输入较多的铁镁及含钙物质,促进油页岩的形成。     

Evolution of an ancient coastal plain: palaeosols, interfluves and alluvial architecture in a sequence stratigraphic framework, Cenomanian Dunvegan Formation, NE British Columbia, Canada

To date, discussion of changes in alluvial style and in the character of palaeosols in relation to changes in accommodation and sediment supply on floodplains has primarily been from a conceptual standpoint: few case studies are available against which to test ideas. One hundred and thirty metres of non-marine strata of the Dunvegan Formation were examined in 14 closely spaced sections in the canyon of the Kiskatinaw River, NE British Columbia, Canada. This site was located about 120 km inland from the transgressive limit of the contemporary marine shoreline and represents almost exclusively freshwater environments. Fluvial channels in the Kiskatinaw River section are of two types. Small, single-storey, very fine- to fine-grained sandstone ribbons with W/T ratios <30, encased in fine-grained floodplain sediments are interpreted as anastomosed channels. Fine- to medium-grained, laterally accreted point-bar deposits forming multistorey sand bodies with individual W/T ratios >30 are interpreted as the deposits of meandering rivers filling incised valleys. Interchannel facies include the deposits of crevasse channels and splays, lakes, floodplains and palaeosols. Floodplain palaeosols consist of laterally heterogeneous, simple palaeosol profiles and pedocomplexes similar to modern Entisols, Inceptisols and hydromorphic soils. Interfluve, sequence-bounding palaeosols adjacent to incised valleys are laterally continuous, up to 3 m thick and can be reliably identified using a combination of (1) stratigraphic position; (2) field observations, such as thickness, structure, colour, degree of rooting; and (3) micromorphological features, such as evidence of bioturbation, clay coatings, ferruginous features and sphaerosiderite. Interfluve palaeosols are similar to modern Alfisols and Ultisols. Correlation of the local stratigraphic succession with the regional sequence stratigraphic framework, based on 2340 well logs and 60 outcrop sections, shows that the vertical changes in coastal plain character (more coals and lakes vs. more pedogenesis) can be related to relatively high-frequency base level cycles (eustatic?) that are expressed as transgressive–regressive marine cycles in downdip areas. Regional isopach maps show that these cycles were progressively overprinted and modified by an increasing rate of tectonic subsidence in the north and west. The character of palaeosols developed on aggrading floodplains primarily reflects local sediment supply and drainage. In contrast, well-developed interfluve palaeosols record pedogenesis during periods of reduced or negative accommodation (base level fall). Vertical changes in floodplain palaeoenvironments and palaeosol types reflect changes in accommodation rate. The detailed micromorphological analysis of interfluve palaeosols represents a powerful application of an under-used technique for the recognition of key surfaces in the geological record. This has broad implications for non-marine sequence stratigraphy.     

Dentaries of a caenagnathid (Dinosauria: Theropoda) from the Nemegt Formation of the Gobi Desert in Mongolia

A symphyseal region of the fused dentaries of a caenagnathid theropod is described from the Upper Cretaceous Nemegt Formation at the Bugin Tsav locality in the Mongolian Gobi Desert. In contrast to the high diversity of Caenagnathidae in the upper Campanian to Maastrichtian in North America, only specimens of a single caenagnathid, Elmisaurus raurus, have been reported in the coeval strata in Asia. Although dentaries are commonly-found bones in the fossil record of Caenagnathidae, the present specimen is the first discovery of caenagnathid dentaries from the upper Campanian to Maastrichtian in Asia. The Nemegt Formation is unique for its diverse oviraptorosaurian fauna that includes both Caenagnathidae and Oviraptoridae as well as the non-caenagnathoid Avimimus portentosus. Hypothesized coexistence of eolian and fluvial environments in the Gobi Basin during the deposition of the Nemegt Formation might explain such co-occurrence of Caenagnathidae and Oviraptoridae.     

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.     

The Geologic Evolution of the Southern Sierra de Guanajuato,Mexico: A Documented Example of the Transition from the Sierra Madre Occidental to the Mexican Volcanic Belt

Geologic mapping and new K-Ar and ⁴⁰Ar/³⁹Ar geochronology of the southeastern Sierra Madre Occidental (SMO), at its intersection with the northern margin of the Mexican Volcanic Belt (MVB), indicate the occurrence of three volcanic groups. The oldest group corresponds to the SMO, and includes 29 to 22 Ma voluminous ignimbrites and 30 Ma andesites and rhyolites. The youngest group includes widespread basaltic-andesitic lava plateaus that yielded ages from 14.6 to 8.8 Ma and are interpreted as the beginning of the MVB. From 22 to 14.6 Ma, volcanic activity in the area was significantly reduced, but did not cease entirely. We refer to the third group as transitional volcanism, which is dominated by andesitic and rhyolitic lava domes but also includes high-grade andesitic ignimbrites. We conclude that the change from volcanism proper of the SMO to that of the MVB was gradual with respect to age and drastic with respect to composition and style, from a voluminous-silicic-ignimbrite domain to a widespread basaltic-andesitic-lava plateau domain. This change may have been related to major plate tectonic reorganizations within the interval from 25 to 12 Ma that involved the waning of subduction of the Farallon plate west of northern Mexico and the associated southward migration of the triple junction of the Pacific-Farallon-North America plates, the subsequent break-up of the Farrallon plate into the Guadalupe and Cocos plates, and the counterclockwise and clockwise rapid rotation of the ridge between them around 16 to 12.5 Ma.     

Orbitolinidae and Alveolinidae (Foraminiferida) from the uppermost Albian-lower Cenomanian of Monti d'Ocre (Abruzzi, Italy)

A biostratigraphic study carried out in the Monti d'Ocre area, Abruzzi, Central Apennines, allowed us to recognize Orbitolina (Conicorbitolina) moulladei ‘Strata 5 (1985) 1’, Praealveolina iberica Reichel and Praealveolina simplex Reichel in uppermost Albian–lower Cenomanian shelf-edge deposits of the Fossato Machè succession. These foraminifers have now been found for the first time in the Apennines of central Italy; their finding is quite important from a palaeobiogeographic viewpoint, as it contributes to the improvement of our knowledge on facies distribution in the circum-Mediterranean regions during the Cretaceous Period. In the study area, the coeval Monte Rotondo and Monte Orsello sections also crop out; these are characterized by bauxite deposits and stratigraphic gaps reflecting episodes of emergence on the carbonate platform. The Monte Rotondo and Monte Orsello sections accumulated in a platform back-reef environment; consequently, in this sector of the Monti d'Ocre area, the depositional environment shifted from a back-reef westward and southward to a shelf-edge northward, during the latest Albian–early Cenomanian. Owing to synsedimentary tectonics, the area investigated underwent differential subsidence: westward and southward, wide areas were uplifted and subjected to emergence, karstification and bauxite accumulation, whereas sedimentation continued in a shelf-edge environment in the north-eastern area.