Cretaceous Research最新文献

The lake transgression event (LTE) associated with a lake anoxic event (LAE) has been reported previously from the Cretaceous Nenjiang Formation in the Songliao Basin, NE China. Detailed studies based on sedimentology, dinoflagellates, ostracods, and biomarkers have provided important evidence for this LTE in Member 1 of the Nenjiang Formation (K₂n¹). However, the related floristic record has not received enough attention. In this paper, palynological data of borehole Ji Tao Di-1 (JTD-1) from the western slope of the Songliao Basin were analyzed to investigate vegetation and climate changes associated with this Cretaceous LTE. Three palynological sub-assemblages reflect significant paleovegetation and paleoclimate changes through this LTE and reveal ecosystem fluctuations related to the global Cretaceous oceanic anoxic event (OAE3). A significant increase in the relative abundance of Schizaeoisporites and Cyathidites spores may represent the LTE in the Nenjiang Formation. Principal Components Analysis (PCA) and Sporomorph EcoGroup (SEG) model indicate that climate changed from cool and humid subtropical before the LTE, to relatively warm temperate during the LTE and temperate after the LTE in this area. The relatively warmer and drier climate during the later period of the LTE may be influenced by the contemporaneous OAE3. After the LTE, the highland mixed forests were dominant, and a large number of angiosperms (i.e., members of the Proteaceae) occupied the ecological niches of the middle canopy, indicating that the flourishing of angiosperms in the late Santonian may be closely related to environmental disturbances resulted from the LTE and OAE.

The Jehol Biota sensu lato has a very wide distribution in East Asia, providing palaeontological clues for recovering the Early Cretaceous terrestrial ecosystems. This Biota was considered to reach the Qinling Orogenic Belt but its reaching time remains unclear. In this study, we initially constrained the age of the Jehol Biota recovered from the Baiwan Formation of the Baiwan Basin, Zhenping County, southwestern Henan Province, which geographically lies in the North Qinling Orogenic Belt. LA-ICP-MS U–Pb analyses were conducted for the fossil-bearing layers, providing a maximum depositional age of ca. 123.6 Ma (early Aptian). This age is consistent with the biostratigraphic analyses, and can approximately constrain the fossil-bearing layers. This study confirmed that the Jehol Biota has already reached the Qinling Orogenic Belt during its secondary evolutionary stage, revealing the unique palaeogeographic position of this belt for the dispersal of the Jehol Biota in East Asia.

Cretaceous bryozoans from South America have received limited attention despite their sporadic documentation. The K/Pg boundary has been identified in numerous fossil-rich basins in Patagonia, where bryozoans are frequent components of the faunas. Material recovered from upper Maastrichtian outcrops of the Lefipán Formation in the Cañadón Asfalto Basin (Patagonia, Argentina) includes a unique species of cheilostome bryozoan, Conopeum foliorum n. sp., attached to leaf remains of terrestrial plants and associated with scarce euryhaline bivalves. It likely thrived in a warm climate, shallow, well-lit brackish environment influenced by tides, located along the northwest margin of the Paso del Sapo embayment. Conopeum foliorum n. sp. is currently among the earliest known bryozoans from brackish water environments, and the second oldest documented instance of a bryozoan encrusting leaves of terrestrial plants, representing the first of such finding in South America. Based on our findings and available sedimentological and paleoecological data from previous studies, we interpreted Conopeum foliorum n. sp. as a fast-growing opportunistic taxon displaying euryhaline habits and prone to colonize terrestrial plant leaves deposited in a brackish-water nearshore environment.

Although mushrooms are important components of ecosystems, their large-scale evolutionary history patterns are rarely known, mainly due to the limited fossil record and the lack of comprehensive phylogenetic studies. Here we present and depict two new species of mushrooms, Marasmiamimum cretaceum gen. et sp. nov. and Mesoagaracites burmitis gen. et sp. nov., based on amber specimens from the mid-Cretaceous period in Kachin State, Myanmar, suspected to belong to the Marasmiineae suborder. The two genera exhibit limited traits, such as ultraminiature basidiomata, a broadly convex pileus with a smooth surface and slightly incurved margin, and sparse lamellae, make it challenging to categorize them into exact families. Similar characteristics are also found in the family Agaricaceae, Mycenaceae, and Omphalotaceae. These new findings enhance our understanding of mid-Cretaceous mushroom biodiversity during the Mesozoic. Furthermore, we provide a catalog of mushroom records in deep time.

The relationship between the Middle–Late Jurassic Yanliao Biota and the Early Cretaceous Jehol Biota has long been unresolved due to an approximately 20 Ma “vertebrate fossil gap”. However, a large number of dinosaur tracks have been reported from the Tuchengzi/Houcheng Formation in northern Hebei–western Liaoning, which occupies the stratigraphic position between the Yanliao Biota and the Jehol Biota. This paper presents new discoveries of diverse dinosaur track assemblages from the Upper Jurassic–Lower Cretaceous Houcheng Formation in the Shangyi Basin, northwestern Hebei Province, China. Based on the ichnological analyses, tracks are assigned to the sauropod Parabrontopodus, theropod Grallator, Anchisauripus, Eubrontes, and Therangospodus. The theropod tracks were likely produced by small-sized feathered theropod dinosaurs (Coelurosauria) that thrived in both the Yanliao Biota and the Jehol Biota. These findings imply that these two biotas evolved successively, without evidence of a complete turnover or extinction of biotas. Sedimentological studies of the tracksites reveal their occurrence in diverse sedimentary environments, including braided sandbar, floodplain, and deltaic plain. The coexistence of highly diverse dinosaur tracks with various preservation environments indicates that the living environment during that time was relatively comfortable. The increased diversity of dinosaur tracks in the upper part of the Houcheng Formation closely aligns with the intense volcanic activity of the Zhangjiakou Formation in northwestern Hebei Province. This suggests that volcanic activity likely served a crucial function in the proliferation of the dinosaur fauna in the Shangyi Basin and northern North China during the earliest Cretaceous.

The braincase features appear phylogenetically informative and key in assessing the still contentious relationships within Crocodylomorpha. Yet, the neurocrania of many non-crocodylian taxa are imperfectly studied. In the present paper, we describe the braincase osteology and neuroanatomy of a paralligatorid crocodylomorph Kansajsuchus extensus from the Upper Cretaceous Kansai locality in Tadzhikistan based on CT-scanning, segmentation, and 3D modeling. The detailed comparison of K. extensus with other taxa expands our understanding of the neurocranial anatomy and evolution in Neosuchia. The braincase anatomy appears to be relatively consistent across most non-crocodylian neosuchians, but important changes in its structure are traced through the neosuchian–eusuchian transition and especially at the base of Crocodylia. We question the close affinities of Dyrosauridae and Pholidosauridae based on significant differences in their braincases.

Our calcareous nannofossil study focused on eleven samples from the lower Campanian (UC14a–UC14b) of the Loibichl section, located in the Rhenodanubian Flysch Zone of the Austrian Alps. Relative counts of calcareous nannofossil assemblages were followed by a morphometrical analysis on 1021 specimens belonging to the Aspidolithus genus (Aspidolithus enormis and Aspidolithus parcus). For this analysis, a light microscope was utilized to improve our understanding of the taxonomic concepts of this group during a phase of rapid morphological evolution. The analysis included the maximum length (L), the width of the outer rim versus the small diameter of the central area (b/a), and the number of perforations in the central area. The CaCO₃ content and bulk carbonate stable isotope ratios of δ¹³C and δ¹⁸O were analysed to facilitate stratigraphic and palaeoecological interpretations. Additionally, this study was to determine whether variations in nannofossil morphometrics were driven by changing palaeoenvironmental conditions. This study identified five morphotypes: A. enormis subsp. 1, A. enormis subsp. 2, A. parcus expansus, A. parcus parcus, and A. parcus constrictus. The morphometric analysis substantiated the differentiation between “small” morphotypes (L < 8.5 μm; A. enormis) and the “large” A. parcus group (L > 8.5 μm). However, the results did not show any significant patterns that would justify a natural separation of the “subspecies” within the A. enormis and A. parcus group. Our statistical analysis suggests that these morphometric changes may be related to various palaeoenvironmental proxies. Further high-resolution morphometric analysis is required to verify the impact of contrasting environmental factors on Aspidolithus-size variation.

This contribution presents a new palynological record from the uppermost Vaca Muerta Formation in the Picún Leufú area, Neuquén Basin, Argentina. A 76 m section was measured, and seven mudstone samples from the top of the Vaca Muerta Formation and the base of the Picún Leufú Formation were collected. Seventy-three palynomorph species were recognised and specimens of the dinoflagellate cyst genera Dingodinium, Gochteodinia, Ambonosphaera, Diacanthum, Systematophora, Tubotuberella, Wrevittia and Canningia were described and illustrated. The following taxa are mentioned for the first time: Tubotuberella in the Vaca Muerta Formation; Gochteodinia in Argentina; and Wrevittia in the Jurassic of Argentina. The dinoflagellate cyst content, integrated with previous studies, constrain the top of the Vaca Muerta Formation in the southern part of the basin, to the lower upper Tithonian. This study extends the basal limit of Pseudoceratium notiale to the lower upper Tithonian and Cribroperidinium reticulatum to the Tithonian. From a paleobiogeographic perspective, the presence of Thalassiphora robusta could provide evidence of its migration from the Volga Basin. Besides, taxa shared with the Tithonian of southeast Tanzania could be reflecting the connection between the Neuquén and the Mandawa basins via the Mozambique Corridor. The dinoflagellate cyst content of the uppermost Vaca Muerta Formation shows a relative decrease in previously reported species for this unit approaching the formational contact, alongside an increase in those species previously documented for the Picún Leufú Formation. The distribution of Pseudoceratium notiale, Dichadogonyaulax culmula and Pilosidinium cactosum was extended to the uppermost Vaca Muerta Formation.

Palynological investigations in the Sumbe region of the Kwanza Basin, Angola, have identified Albian to Turonian assemblages in four sections of the Quissonde Facies of the Mucanzo, Cabo Ledo, and Itombe formations. These studies aimed to determine their biostratigraphic ages and infer paleoenvironmental, paleoclimatic, and paleogeographic models. The presence of Odontochitina costata, Palaeohystrichophora infusorioides, and Xiphophoridium alatum cysts supports an upper Albian to lower Cenomanian age for the Mucanzo Formation. Litosphaeridium siphoniphorum cyst and the Elateroplicites africaensis pollen found In the Cabo Ledo Formation suggest a Cenomanian age, while Conosphaeridium striatoconum, Heterosphaeridium difficile, and Dinogymnium acuminatum supports a Turonian age for the lower part of the Itombe Formation. All samples predominantly contain fluorescent amorphous organic matter (AOM) derived from phytoplankton degradation, with increasing AOM in the uppermost units, indicating inner neritic marine deposition under dysoxic-anoxic conditions. During the Lower to mid-Cretaceous, the Gondwana breakup caused significant changes, with the palynological indicating a Tethyan affinity with some high-latitude taxa, suggesting a cosmopolitan distribution. The subtropical to tropical nature of the assemblages, along with high-latitude species, indicates a mid-Cretaceous water connection between the Central Atlantic and the South Atlantic oceans, extending to the Kwanza Basin.

The Tolmin Basin constitutes the western part of the Slovenian Basin, a large Mesozoic interplatform basin that was bounded to the north by the Julian Carbonate Platform and to the south by the Dinaric Carbonate Platform. Today, it is found along the structural boundary between the Southern Alps and the External Dinarides in northwestern Slovenia. After the drowning of the Julian Carbonate Platform, the Tolmin Basin was dominated by pelagic deposits, namely the Toarcian marlstones (Perbla Formation), the Aalenian to lower Tithonian siliceous limestones and radiolarites (Tolmin Formation), and the upper Tithonian to the Berriasian Biancone Limestone Formation. In this study, a basin-scale sedimentary evolution and calpionellid biostratigraphy of the latter is presented. The Biancone Limestone Formation is a calpionellid-bearing pelagic limestone typical of all deepened segments of the Adria microplate in this time interval. It is generally monotonous but shows considerable vertical and lateral variations. The lower boundary with radiolarites is sharp, revealing a pronounced and rapid overturn in pelagic sedimentation. The lower Berriasian slumps indicate a tectonic pulse. Rare beds of resedimented limestones, assigned to the middle Berriasian, are similar in composition to those intercalated in the underlying radiolarites. They thus show that the factors that led to a significant shift in pelagic sedimentation had little or no effect on shallow-marine carbonate production. In the upper Berriasian, an increase in clay content is evident in the formation, which is explained by the uplift and erosion of the propagating thrust belt in the Neotethys area, superimposed by humidification.