Cretaceous Research最新文献

Here we report tetrapod tracks from a stratigraphic level of Maastrichtian age in the Yacoraite Formation (Maimará ichnosite, Jujuy Province, Argentina). The ichnological material consists of convex hyporeliefs whose formation was induced by growth of microbial mats in an upper subtidal-lower intertidal setting. Ichnological features that are recognized in tracks and traces allowed to include them into the categories of ‘punting tracks’ and ‘buoyancy tracks’. These categories suggest swim behaviours of the producers, which are tentatively interpreted as crocodylomorphs. Reconstruction of the filling process leading to tracks preservation and inclusion into the geological record enabled reconstructing at least two different phases of mats development, one dominated by chemical precipitation and the other by trapping and binding of coated grains and other particles. These two phases of mat growth are related to slightly changing energetic conditions of the palaeoenvironment and further support a marine origin for the unit. Finally, it is suggested that biologically induced, in-situ mineral precipitation promotes fast formation of overtracks through early lithification achieving preservation of tetrapod tracks well before their complete filling.

The late Campanian-Maastrichtian in the Ibero-Armorican domain is rich in titanosaurian fossils. The sauropod remains exhibit a high degree of morphological variability, especially in the commonly-found appendicular elements. The phylogenetic relationships of the Ibero-Armorican titanosaurs are still uncertain but we do know that they experienced a Campanian-Maastrichtian herbivorous faunal turnover. It is probable that the small-to-medium-sized Lirainosaurinae-dominated faunas of the Campanian were replaced by late–early Maastrichtian large-bodied lithostrotian dominated faunas. In this context, the Villalba de La Sierra Formation has yielded an abundant sample of medium-to-large sized titanosaurs. In this study we analyze the morphological variability in the appendicular skeleton of the titanosaurs from the Campanian-Maastrichtian Ibero-Armorican domain. We follow previous attempts to classify the commonly-found isolated titanosaurian femora and expand the proposed methodology. The use of combined phenotypic characters and linear morphometrics can be helpful to analyze the morphological variability and diversity of the Ibero-Armorican titanosaurs. Our findings corroborate the presence of at least two exclusive morphotypes in the Lo Hueco fossil site and one exclusive morphotype in the Poyos site, as well as the presence of previously defined Lirainosaurinae across the Pyrenees during the Campanian-Maastrichtian. The Villalba de La Sierra Formation titanosaurs are also clustered with large-bodied late Maastrichtian titanosaurs. It is possible that either the large-bodied late–early Maastrichtian immigrants, with possible Gondwanan affinities, entered the Iberian Peninsula much earlier or that this group was already present at least during the Campanian-Maastrichtian transition, as the small-sized Lirainosaurinae declined.

Here, we report the occurrence of a large number of fossil fruits with distinctive germination pores along with a petrified stem, resembling morphologically and anatomically the extant palm tribe Cocoseae Mart. ex Dumort. of the subfamily Arecoideae. The permineralized fruits and locule casts, assigned to Palmocarpon drypeteoides (Mehrotra, Prakash, and Bande) Manchester et al., and the stem of Palmoxylon sp. were recovered from the Deccan Intertrappean Beds (late Mastrichtian–early Danian sediments; c. 66–65 Ma) of Umariya Ryt. village in Dindori District, Madhya Pradesh, Central India. Using micro–computed tomography (mCT) and standard thin section methods, we observed for the first time that these fossil palm fruits have a persistent basal trimerous perianth. These fossils, along with other reports in the literature, suggest that cocosoid palms were dominant among the arecoid palms of the Deccan Intertrappean beds in Madhya Pradesh. At present, the modern relatives do not grow in the same area but they occur in tropical forests of southeastern and eastern India as well as other regions including parts of South America, Asia, Europe, and Africa. The expansions and retraction of the cocosoid palms likely coincide with climate change. The recovery of cocosoid fossils (present and earlier reported) and previously described tropical elements from the same fossil locality suggest the existence of tropical climatic conditions during the period of depositions. We also revisit the historical phytogeography of the cocosoid palms.

Fossil caddisfly larval cases (CLCs) are of great significance for reflecting the habits of ancient caddisfly and indicating the paleoenvironment. Multiple layers with bioherms formed by fossil CLCs and stromatolites were found to be distributed in the Lower Cretaceous in Liupanshan Basin, Central China. In order to deeply understand the characteristics and formation environment of the CLCs-stromatolite bioherms, a series studies were conducted on the Yaoshan section in the northeastern of the basin. Morphological anatomy, mineralogy, element geochemistry, and isotope geochemistry are included in the studies. It reveals that the CLCs-stromatolite bioherms in Yaoshan are mainly composed of calcite and dolomite mineralogically, and CLCs and stromatolite morphologically.

In the bioherms, a large number of fossil CLCs stacked orderly, with a conical shape perpendicular to the stratum distribution. The bioherms were deposited in a semi-enclosed saline lake in hot and dry paleoclimate, and they were mainly formed during the periods when the evaporation increased, the water body became shallower, and the supply of terrestrial material increased.

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.