Cretaceous Research最新文献

An ammonite biostratigraphic analysis was carried out for the La Peña del Águila section, Zacatecas State, northern Mexico, within Valanginian strata of the Taraises Formation. Bed-by-bed sampling yielded 208 ammonites identified in 13 taxa. The biostratigraphic analysis allowed us to identify two ammonite zones: Neocomites neocomiensiformis and Karakaschiceras inostranzewi; and one subzone: Neocomites platycostatus. These biostratigraphic units range within the lower Valanginian. The identified fauna in the La Peña del Águila section has been previously reported in the Mediterranean region. The faunal similarity allows us to employ the Standard Mediterranean Ammonite Scale for the analysis of the current section. This affinity between the Mexican and Mediterranean ammonite faunas could be explained by the proximity and communication between these two areas through the Hispanic corridor during the Valanginian.

Herein the epibiont agglutinated placopsilinid foraminifer Acruliammina longa from the upper Hauterivian of the Neuquén Basin is discussed. This is the first record from South America of A. longa, already known from the upper Valanginian to lower Turonian? of North America and Europe. The studied material consists of foraminiferal tests forming macroids and encrusting the valves of Ptychomya koeneni, coming from poorly lithified claystones/siltstones to marlstones forming high frequency (6th-order) depositional sequences within the upper Hauterivian Agua de la Mula Member of the Agrio Formation. This new record extends the paleobiogeographic distribution of A. longa, and allows us to investigate the paleoenvironmental and paleoecological significance of this species in a mixed carbonate and siliciclastic ramp. Energy dispersive spectroscopy and X-ray computed microtomography were used to evaluate taphonomic features of foraminiferal tests, highlighting differences between tests that encrust bivalves and those forming macroids, which also differ in their position within the 3rd-order sedimentary sequences. A. longa tests encrusting bivalves are less damaged, show coarser grain size, and occur throughout the 3rd-order regressive systems tracts, whereas tests forming macroids show higher breakage and finer grain size, occurring throughout the 3rd-order transgressive systems tracts. This distribution allows us to interpret changes in rates of terrigenous input at the time of encrustation, and also in energy conditions, highlighting the opportunistic behavior of A. longa. Low sedimentation rates represent the main paleoenvironmental condition that favored foraminiferal propagule settlement and the growth of A. longa, both on bivalve fragments exposed on the seafloor in the case of macroids, and on living Ptychomya koeneni shells.

Caenagnathid oviraptorosaurian dinosaurs, long considered enigmas, have now become relatively easy to recognize in the fossil record of Asia and North America. This has revealed their presence in several formations spanning the Late Cretaceous, providing new insights including showing that they were more widespread in the southern parts of North America than previously recognized. Here we add to this record by describing a nearly complete right tibia from the upper Campanian De-na-zin Member of the Kirtland Formation of New Mexico, which represents the first caenagnathid material from these beds. The bone is nearly identical in morphology and size to its counterpart in the Mongolian Elmisaurus rarus, reinforcing a suite of previously-identified features that allow for straightforward recognition of caenagnathid tibiae. The growing body of caenagnathid material continues to blur boundaries between features once considered distinct, raising doubts that some taxa established from sparse material, including Ojoraptorsaurus boerei, are actually valid.

The subfamily Mortoniceratinae comprises Albian to early Cenomanian ammonoids whose phylogeny forms the basis of a biozonation for the upper Albian due to their highly evolving nature and worldwide distribution. However, both morphological plasticity of the group and the known common occurrences in many condensed successions call for accurate taxonomy and stratigraphy in order to ascertain the phylogeny and temporal/spatial relationships. Here, early late Albian Mortoniceratinae from mostly uncondensed successions, with a continuous record, are described from a hyperextended pericratonic rift basin in the Western Pyrenees. Although quite rare in the study area, we can here provide a detailed taxonomic study of 55 specimens, representing 19 species, with a single new genus and five new subspecies, all recovered over a period of 30 years from upper Albian strata in eight sedimentary areas covering nearly 1000 square kilometres and more than 4000 m of measured logs. Most of these mortoniceratines show morphologies that are in agreement with their known and accepted phyletic lineage in which tuberculation stages are key; however, we also record tri- and quadrituberculate forms that depart from the main and represent unsuccessful offshoots. A reassessment of Mortoniceras (M.) fallax is presented, inclusive of a more complete, emended diagnosis, and referral of the eponymous biozone to the lower upper Albian. The palaeobiogeographical distribution of species studied corresponds to the western Mediterranean area, part of the central Tethyan Realm, in the Basque-Cantabrian Basin (Western Pyrenees) which faces the northern European basins of the Boreal Realm. This strategic location is interpreted to be a nexus between worldwide basins, as the striking cosmopolitan character of most species studied suggests. The ammonoid fauna studied is proposed as support of the western Mediterranean biozonation; it is tentatively correlated interregionally as well.

In the Baghin section, west of Kerman, Iran, Aptian scleractinian corals are described for the first time in relation to taxonomically related genera and species. The superfamilies are Actinastraeoidea, Cladocoroidea, Cyclolitoidea, Eugyroidea, Stylinoidea, Montlivaltioidea, Caryophyllioidea and Misistelloidea. Other macrofossil groups are echinoids, gastropods, brachiopods and bivalves and confirm the Aptian age. Regarding identified corals, it was concluded that the study area can be correlated with Aptian-Albian of other Lower Cretaceous coral faunas of Basque-Cantabrian Basin in the Central Tethys, and also most closely related to faunas of the Aptian Pelagonium South margin and the Aptian -Albian Bisbee Basin in the western Atlantic.

Rettenbacher Quarry carbonate sequence in the Northern Calcareous Alps represents highly dynamic pelagic carbonate sedimentation in the lower slope environment. The section spans from upper Tithonian Crassicollaria colomi Subzone to middle Berriasian Calpionella elliptica Subzone. Radiolarian samples belong to Pseudodictyomitra carpatica Zone. Considerable redeposition of calpionellids, organic walled dinoflagellate cysts, calcareous nannofossils and foraminifera in the allodapic layers, as well as extensive normal polarity remagnetisation event with substantial clockwise rotation is documented. Quantitative predominance of genera Watznaueria and Cyclagelosphaera indicate strong nannofossil modification during diagenesis. The almost straight trend in the δ¹³C with some slight carbon-isotope perturbations is recorded at Rettenbacher. Three significant and stratigraphically important negative excursions of the δ¹³C_carb values were identified — including tentative indication of a new “Negative peak 4” in the upper part of the Elliptica Subzone — and correlated with other sections confirming stability, respectively isochronity within carbon chemostratigraphy.

From mudstones and sandstones referred to as the Lower Idzików Beds, as exposed at Stary Waliszów (Upper Nysa Kłodzka Graben, south-west Poland), a rich assemblage of body fossils has been recovered. This comprises rare ammonites (Baculites incurvatus, Forresteria cf. petrocoriensis, ?Scalarites sp.), nautiloids (Anglonautilus sinuatoplicatus), numerous bivalves, inclusive of inoceramids such as Inoceramus frechi and Volviceramus involutus, oysters (Ceratostreon, Vultogryphaea and Hyotissa) and other common genera such as Scabrotrigonia, Protocardia, Cucullaea, Neithea, Pinna, Liopistha, Panopea and Goniomya. Gastropods include mainly aporrhaids, turritellids, naticids and ampullinids. Echinoids are rare and comparatively poorly preserved, comprising only irregular forms (cardiasterids, micrasterids and hemiasterids), some of them being recorded from the Upper Cretaceous of Poland for the first time. Decapod crustaceans are fairly abundant in the Lower Idzików Beds, with axiideans predominating. A taphonomic analysis shows that this assemblage is well preserved, suggesting rapid burial as a result of storm events, while a palaeoecological assessment of taxonomic composition and trophic modes implies that deposition took place in a shallow-marine, well-oxygenated environment with a soft-bottom substrate, rich in nutrients and close to the fair-weather wave base. The presence of stenohaline taxa such as ammonites and echinoderms provides evidence of normal salinity.

Kateretidae is a beetle family with 15 reported fossil species, four of them with specialized antennal scape. Specialized scape represents a rare form of sexual dimorphism in Kateretidae. Here we report two new species with a special scape in males of Protokateretes Zhao, Huang and Cai, 2023, and one female individual of an unnamed species of Protokateretes. The discovery of new species provides a supplementary diagnosis of Protokateretes, and increases the biodiversity of the fossil genus. The high diversity of species in Protokateretes provides new insights into sexual dimorphism of Kateretidae in mid-Cretaceous, enriching the knowledge of potential courtship strategy of kateretid beetles in the late Mesozoic.

Stegosaurs are a minor but iconic clade of ornithischian dinosaurs, and along with their sister taxon ankylosaurs form the clade Eurypoda, the major radiation of Thyreophora (armoured dinosaurs). We here report some stegosaurian materials from the Lower Cretaceous Hekou Group of the Zhongpu area, Lanzhou-Minhe Basin, Gansu Province, China. Most of the morphology of the specimen is similar to Stegosaurus stenops and Stegosaurus homheni. However, its dorsal vertebrae have a higher neural arch and smaller neural canal than Stegosaurus stenops. The neural arches of the dorsal vertebrae of Stegosaurus homheni are deeply excavated dorsal to the neural canal in anterior view, which is not present in GSAU 201201. Because the material is fragmentary, we consider the new specimen as Stegosaurus sp. In phylogenetic analysis, it is also recovered as the sister taxon of Stegosaurus stenops. This is the first stegosaurian dinosaur from Gansu Province, which extends the geographical range of Stegosauria and enriches the Cretaceous stegosaurian record. The Ankylosaur Taohelong jinchengensis is also from the same area and same layer as this stegosaur, which is new evidence that they lived in the same ecosystems alongside each other.

The search, over several decades, for overlap (if any) in the stratigraphical ranges of two common holasteroid sea urchin genera in the type area of the Maastrichtian Stage (south-east Netherlands, north-east Belgium), has come to an end. Here, the first examples of representatives of Echinocorys and Hemipneustes are recorded in situ from the middle portion (between flint levels 10 and 12/12a) of the Lanaye Member (Gulpen Formation) at the former ENCI-HeidelbergCement Group quarry (Maastricht, the Netherlands). At this level, the typically Tethyan genus Hemipneustes is accompanied by other echinoid ‘newcomers’ such as Nucleopygus scrobiculatus, N. coravium, Oolopygus pyriformis, Catopygus fenestratus, Bolbaster prunella, B. koninckanus and Leymeriaster eluvialis. Most of these genera can be linked to shallower settings, and two at least (Nucleopygus, Catopygus) connected with shallower, coarser-grained and more permeable facies. The ‘last’ Echinocorys and the ‘first’ Hemipneustes in the Lanaye Member are separated by a single flint/chalk couplet, indicative of the c. 21-kyr precession cycle. At flint level 10 of the Lanaye Member, a negative carbon isotope excursion, suggesting a regressive phase, has recently been determined and tentatively equated with M3-(b) in the Stevns-1 borehole (Denmark), situated within calcareous nannoplankton zone UC20a and close to the last appearance datum (LAD) of the dinoflagellate marker species Triblastula utinensis. The exchange in echinoid faunas at this level may thus have been controlled by bathymetry (and concomitant differences in temperature), as well as by increased nutrient levels on the seafloor.