Cretaceous Research最新文献

Acanthopteris is a fossil fern genus that was established by H.C. Sze in 1931 based on leaf remains from the Lower Cretaceous of the Fuxin Basin in Liaoning Province, China. Traditionally, Acanthopteris is considered to belong to the tree fern family Dicksoniaceae and has been mainly found in the Lower Cretaceous of Fuxin Basin, Huolinhe Basin, and other coeval basins in Northeast China. Since this genus was founded, five fossil species have been described, including A. gothani Sze, A. acutata (Samylina) Zhang, A. alata (Fontaine) Zhang, A. onychioides (Vassilevskaja et Kara-Mursa) Zhang, and A. szei Cao. Based on the investigations on the newly collected fossil specimens and the examinations of other specimens, a reassessment of the systematics and fossil record of Acanthopteris is performed by using both morphological and cluster analysis approaches. The emendation of generic diagnosis of Acanthopteris is provided herein. Geographically, Acanthopteris shows limited distribution in North and NE China, Siberia, Russia and the Inner Zone of Japan. Temporally, Acanthopteris is restricted to the Aptian-Albian period, representing a climate index fossil for a warm and humid climate condition of tropical to subtropical zones during the Early Cretaceous.

Knowledge of continental faunas and floras from the Jurassic–Cretaceous transition in Gondwana, and especially in Africa, is limited. Here, we report the discovery of a rare assemblage of plants and aquatic reptiles from the Tithonian–Berriasian interval of the Anoual syncline in southeastern Morocco. Our preliminary field investigations led to the discovery of a disarticulated skeleton of a goniopholidid crocodylomorph, of a single fragment of a turtle plate, and of abundant plant remains, inviting further exploitation of the fossiliferous horizon. This assemblage indicates a freshwater habitat bordered by a lush moist conifer forest. Its taxonomic composition shows a strong similarity with better known contemporaneous Laurasian assemblages and stresses the paucity of coeval Gondwanan assemblages. Our discovery highlights that peri-Tethys continental assemblages may have shared common taxa and raises the question whether Laurasian and Gondwanan taxa from the Jurassic-Cretaceous transition were cosmopolitan, before they diverged later during the Cretaceous.

The Cretaceous/Paleogene boundary (K/Pg) event, associated with a meteorite impact at Chicxulub, Mexico, is globally recognized as one of the largest mass extinctions in natural history, marking the end of the Mesozoic Era. However, most of the outcrops with records and geochemical evidence of this boundary are distributed in the Northern Hemisphere and at mid-latitudes. Here, aiming to contribute to the knowledge of this event at high southern latitudes, we characterize a single iridium anomaly correlated with the K/Pg boundary, present within a carbonaceous mudstone level in a continental depositional environment in the Río de las Chinas Valley, Chilean Patagonia. High-resolution geochemical and palynofacies analyses were performed on a stratigraphic section from the top of the Dorotea Formation. Results showed that the iridium enrichment coincides with an anomaly of other platinum group elements. In addition, the palynofacies analysis showed a disturbance in the depositional environment, marked by an abrupt change from non-degraded phytoclasts (e.g., cuticles) to pseudoamorphous and degraded cuticles, and by an increase in the abundance of spores at the same level. The Río de las Chinas Valley locality provides new evidence for the comprehensive study of the end-Cretaceous event, from the poorly represented continental environments of high southern latitudes.

Acanthohoplites aschiltaensis, a late Aptian ammonite originally described from the Caucasus of Dagestan, is recognised from the British Isles for the first time. A study of the full ontogenetic development of this species is enabled owing to the preservation of a mature body-chamber, not previously known. Stratigraphically, it confirms the correlation of the Fullers' Earth deposits within the Parahoplites nutfieldiensis Zone at Baulking, Oxfordshire, with strata of the Parahoplites melchioris Zone at the type locality and elsewhere. Palaeobiogeographically, it underlines the strong relationship between the Boreal fauna of western Europe and that of the Mediterranean-Caucasian Subrealm of the Tethyan realm. Additionally, a small Hypacanthoplites spp. fauna is described from the H. rubricosus Subzone of the Hypcanthoplites jacobi Zone at the Aptian/Albian boundary interval exposed in the Shanklin area, Isle of Wight. From this locality, otherwise almost devoid of ammonite remains, we present fairly well-preserved specimens of ‘Hypacanthoplites’ elegans, H. plesiotypicus, H. pricei, H. tenuiformis, H. rubricosus, H. sigmoidalis and H. sp. 1 indet., only known thanks to some decades of intensive collecting. In addition to the other members of this genus previously described from the British Isles, the occurrence of ‘H.’ elegans and H. plesiotypicus further supports the existence of narrow sea connections eastwards onto the European continent.

The Dipsocoromorpha is a small modern heteropteran infraorder, with some fossils documented in Mesozoic amber in recent years. We herein report a new remarkable specimen trapped in mid-Cretaceous Kachin amber, which can be attributed to Dipsocoromorpha: Schizopteridae. Kuanzuia cavanii gen. et sp. nov. is erected for the new specimen on the basis of the following unique autapomorphic characteristics amongst known dipsocoromorphans: pronotal second and third lobes completely fused together and embowed, metafemora nearly triangular in lateral view and with one row of c. 20 strong ventral spines, and metatibiae greatly curved at about its 2/3 length. Mesozoic dipsocoromorphan fossils reported in America, Lebanon, France and Myanmar provide paleontological evidences that this ancient heteropteran insect lineage had probably been distributed worldwide at latest in the Early to mid-Cretaceous. Our new finding further indicates that compared to their modern descendants, early dipsocoromorphans in the late Mesozoic were flourishing and also likely with high morphological disparity.

Stromatolites are organo-sedimentary structures, internally laminated, which grow attached to the substrate. This lamination mirrors the dynamic interaction of environmental and biological factors where its formation takes place. However, some stromatolites from the Yacoraite Formation, from Amblayo locality, in northwestern Argentina, present an unconventional internal structure characterized by bilateral symmetry, where the development of lamination extends towards both sides of an imaginary plane.

This contribution reports a multi-scale analysis of these particular stromatolites, with the aim of determining the extent to which environmental factors have influenced their internal structure. In addition to this, a sequence of stages that gave rise to these organo-sedimentary structures will be proposed.

Results suggest a microbialitic growth by in-situ biologically induced, carbonate precipitation, which was carried out in a shallow intertidal environment with good luminosity and significant sedimentary input. However, the stromatolitic growth occurred over two stages, interrupted by a stochastic event that generated a overturning of the structure, providing a new colonizing surface for growth of microorganisms and resulting in a bilateral internal structure.

The characterization of these stages, including the overturning of the structure, not only provides a highly accurate proxy for reconstructing punctual environmental conditions of the Yacoraite Formation, but also opens up a field of discussion focused on the resilience and recolonization capacity of stromatolite-producing microorganisms after stochastic events.

Chilinia is an extinct genus of cycads, established by Li and Ye in 1964 based on leaf fossils from the Lower Cretaceous in Jilin Province, China. Morphologically, the genus Chilinia closely resembles Ctenis, another cycad foliage genus, in having pinnately divided leaves with laterally inserted pinnae on the rachis and reticulate venation but differs mainly from the latter in having toothed or irregularly lobed rather than entire-margined pinnae. Fossil records show that up to now, nine species of Chilinia have been reported worldwide, representing an index fossil plant in the Jurassic to Early Cretaceous. In this study, we present a comprehensive overview of all reported Chilinia fossils from a systematic palaeobotanical perspective. Fossil records indicate that Chilinia mainly occurred in the middle–high latitudes of the northern and southern hemispheres in Pangea from the Middle Jurassic to Middle Cretaceous. Combined evidence from the morphology of Chilinia and its floral patterns suggests that the genus probably lived in humid warm-temperate palaeoclimatic conditions with brief seasonal variations.

The jaws of cephalopods, ammonites and especially coleoids, are rarely met in fossil state. The localities with diversified jaws, belonging to various groups of fossil cephalopods are even less common. We describe a diversified complex of cephalopod jaws from the upper Cenomanian–middle Turonian of Northern Siberia, which include the upper and lower jaws of Placenticeras ammonites (the oldest placenticeratid jaws known to date) and large-sized jaws of octobrachian coleoids. Although the lower jaws of Placenticeras belong to the aptychus type of ammonoid jaw apparatuses, they are characterized by the thickening of an inner organic layer in their anterior part, with a shape resembling a calcified conchorhynch known in the anterior portion of the lower jaws of Mesozoic nautilids and lytoceratid and phylloceratid ammonoids. The presence a conchorhynch-like structure supports the assumption that the feeding function in placenticeratid lower jaws most likely prevailed over the protective one. The upper jaws of Placenticeras show structure, typical for the jaws of aptychophoran ammonites: an inner lamella, divided into two wings, and a pointed outer lamella. Large-sized upper jaws of octobrachian coleoids demonstrate close affinities with the jaws of Octopoda suggesting that they could have belonged to representatives of this order, probably to large-sized gladius-bearing teudopseins. Judging by the jaws' size, both ammonites and octobrachians, which inhabited the marine basin in the Northern Siberia, were characterized by large body size. The cephalopod assemblage remained unchanged throughout the end of the Cenomanian and the first half of the Turonian.

Late Cretaceous-Early Palaeocene geo-climatic events played an important role in the diversification of the modern ichthyofauna. Lepisosteiformes and Siluriformes are two diverse clades of freshwater fishes, poorly known from India in this time interval. Their fossil record documents their early diversification and can be used to reconstruct palaeobiogeographic relationships among the continental masses during the Late Mesozoic. Indeed, the Cretaceous-Palaeocene is an exceptional time span for the Indian plate as it underwent a primary spatial reorganisation and remarkable geologic and climatic changes with extensive outpouring of the Deccan basaltic magma. Field investigation in a Deccan sedimentary sequence at Kisalpuri, Central India has yielded new, rich, and taxonomically important fossil material of Lepisosteiformes (Lepisosteus indicus, Lepisosteidae) and Siluriformes (Siluriformes indet.), which significantly improves their Cretaceous-Palaeocene fossil record from the Indian subcontinent. These fish lived in freshwater environments such as large rivers, lakes, and coastal areas. Their presence along with other aquatic biotic elements suggests that the Kisalpuri was an abundant aquatic ecosystem rich in nutrients, which attracted a diverse range of organisms to live together with fish. Biostratigraphically, these fishes first emerged in the Late Cretaceous-Early Palaeocene on the Indian subcontinent, and later, they spread to other parts of subcontinent throughout the Cenozoic. Their earliest intra-continental distribution was controlled by the palaeodrainage network influenced by the volcanic flows of the Deccan traps. Their inter-continental palaeobiogeographic distribution was broadly controlled by the sequential break-up of Pangaea. There appear to be close palaeobiogeographic linkages between South America and India during the Cretaceous-Palaeocene era based on the similarity between the Lepisosteiformes and Siluriformes remnants from India and those reported from the Upper Cretaceous of the Bauru Group, Brazil.

The Gobi Desert of southern Mongolia is home to an incredibly rich record of dinosaurs and other vertebrate fossils from the latest Cretaceous Period. Together, more than a dozen sites in several basins have produced one of the richest palaeofaunas known from this interval anywhere in the world. Most of this diversity has been recovered from the fluvial deposits of the Nemegt Formation. Despite historic and ongoing research in southern Mongolia, accurate maps and geological data for the main fossil sites are still lacking, limiting our ability to investigate how local palaeoecological dynamics influenced Nemegt taxa, their geographic distribution, and their evolutionary patterns. One of these sites, Guriliin Tsav, has produced more than a hundred significant fossil specimens to date, but still remains one of the lesser known Nemegt localities. In part this is because many expeditions have instead focused on the nearby Bügiin Tsav, one of the largest and richest localities for the Nemegt Formation. To address this gap, a project was initiated in 2018 to produce a high-resolution topographic map of Guriliin Tsav using Unmanned Aerial Vehicles (UAV), and consequently, to plot the geographic and stratigraphic distributions of palaeontological resources on this map. In so doing, we also collected stratigraphic and taphonomic data from the area, allowing for the first detailed palaeoecological interpretation of Guriliin Tsav and a comparison with other localities of southern Mongolia. Here we present the results of this project, and also discuss new topographic and stratigraphic data from Bügiin Tsav. This sheds new light into the temporal and geographic distribution of vertebrate taxa in the latest Cretaceous of Mongolia.