Jehol Biota Research Articles

Tooth replacement of the filter-feeding pterosaur Forfexopterus and its implications for ecological adaptation

Abstract A “comb-dentition”, characterized by long, needle-like, and closely-spaced teeth, is found in the ctenochasmatid pterosaurs as an adaptation for filter-feeding. However, little is known about their tooth replacement pattern, hindering our understanding of the development of the filter-feeding apparatus of the clade. Here, we describe the tooth replacement of the pterosaur Forfexopterus from the Jehol Biota based on high-resolution X-ray Computed Tomography (CT) reconstruction. As in the ornithocheirid Coloborhynchus, the tooth germs are relatively medially positioned along the middle line; the replacement teeth erupt at the posteromedial side of the functional tooth; no more than one replacement tooth present in each alveolus. The replacement teeth are less than half of the length of the full-grown tooth, and alternatively positioned along the tooth row. The alternatively-positioned young and mature functional teeth are dominant and abrased, maintaining the active tooth-tooth occlusion of the filter-feeding apparatus. Reconstruction of Zahnreihen shows an average Z-spacing of 2.02, comparable to that of the simple alternate replacement (Z-spacing = 2) between odd- and even-numbered tooth positions in reptiles. Based on comparisons with Balaenognathus, Ctenochasma, and Pterodaustro, the tooth replacement pattern appears to be varied in ctenochasmatids, and needs to be further studied in the future.

A new diminutive species of bohaiornithid enantiornithine (Aves: Ornithothoraces) from the Lower Cretaceous Jehol Group, northern China

Enantiornithes are the most successful early-diverging avian clade, their fossils revealing important information regarding the structure of Cretaceous avifaunas and the parallel refinement of flight alongside the ornithuromorph lineage that includes modern birds. The most diverse recognized family of Early Cretaceous enantiornithines is the Bohaiornithidae, known from the Jehol Biota in northeastern China. Members of this clade enhance our understanding of intraclade morphological diversity and elucidate the independent evolution of this unique lineage. Here, we report on a new specimen of bohaiornithid, Neobohaiornis lamadongensis gen. et sp. nov., from the Lower Cretaceous Jiufotang Formation in western Liaoning, China. The holotype specimen is considerably smaller than all other known bohaiornithids (roughly half the size of Bohaiornis). The presence of complete fusion in compound elements strongly suggests it represents a mature or nearly mature individual, and therefore substantially increases the known size range of this clade. This specimen further differs from known bohaiornithids in that it exhibits reduced manual unguals and an increased number of sacral vertebrae, which indicates bohaiornithids evolved increased flight capabilities in parallel to other enantiornithine lineages, such as the Longipterygidae. Traces of the plumage, which are rarely preserved in bohaiornithids, reveal the presence of remiges with rounded distal margins and short crural feathers.

High-precision age constraint for the Xiyingzi Bed of the Jiufotang Formation in western Liaoning, Northeast China

The Jehol Biota includes exceptionally well-preserved fossils that are major components of Early Cretaceous land ecosystems. The youngest example of the Jehol Biota occurs in the Jiufotang Formation, which potentially records palaeoenvironmental factors triggering evolutionary turnover. However, the lack of stratigraphic correlations and uncertain age horizons for many fossil taxa lead to conflicting interpretations of events. This study describes a new significant fossiliferous bed (Xiyingzi Bed) from the upper Jiufotang Formation of the Baomayingzi-Yuanjiawa outcrop in western Liaoning, Northeast China. High-precision CA-ID-TIMS U-Pb analysis of a tuff sample from the Xiyingzi Bed provides an age of 121.272 ± 0.040/0.068/0.15 Ma, representing the first reliable age for the upper Jiufotang Formation in western Liaoning.Vertebrate fossils preliminarily reported from this bed include the confuciusornithid and enantiornithine birds, the istiodactylid pterosaur, the non-hadrosaurid iguanodontian dinosaur, the long-necked choristoderan reptiles, the sinemydid turtles, and the polyodontid and sinamiid fish. These fossils were previously reported from the lower horizons, indicating stable development of the late Jehol Biota. New results from the Xiyingzi Bed provides a glimpse of the late Jehol biota before transforming into a typical mid-Cretaceous biota in western Liaoning. Systematic biostratigraphic and chronostratigraphic analysis of the Xiyingzi Bed helps the evolutionary interpretations of the late Jehol Biota and the correlation of the Jiufotang Formation within different basins of western Liaoning.

Cretaceous stratigraphy in the Songliao Basin, NE China

The Songliao Basin is one of the largest non-marine oil- and gas-bearing basins that developed during the Cretaceous period, recording an almost complete Cretaceous stratigraphy. With oil and gas exploration, as well as the Continental Scientific Drilling Project of Cretaceous Songliao Basin (CCSD-SK) (2006–21), significant progress has been made on the stratigraphy of the Songliao Basin. The Songliao Basin is therefore important for understanding the non-marine Cretaceous system. Based on lithostratigraphy, sequence stratigraphy, biostratigraphy, geochronology, magnetostratigraphy and cyclostratigraphy, a comprehensive stratigraphical framework of the Songliao Basin has been established in this study. The Lower Cretaceous strata (Hauterivian–Albian) of the basin are dominated by volcanic–sedimentary deposits, while the lower-middle Upper Cretaceous (Cenomanian mid-Campanian) strata are dominated by lacustrine deposits. The upper Upper Cretaceous strata (late Campanian–Maastrichtian) are dominated by fluvial–lacustrine deposits. Fossils are very abundant in the Songliao Basin, and three biotas – the Jehol Biota sensu lato , the Songhuajiang Biota and the Mingshui Biota – are recognized in the Songliao Basin. Furthermore, several important geological events, such as lake anoxic events, seawater incursion events and the K/Pg boundary extinction events are all recorded in the Songliao Basin.

New investigations on Cretaceous woods from the Jiaolai Basin, Shandong Province and their palaeoclimate relevance

The Jiaolai Basin of China is the southernmost edge of the distribution of the northern Jehol Biota and an important area which bears both the northern and southern palaeogeographical fauna representative species. The Laiyang flora in the Jiaolai Basin is located in the transitional region between the Early Cretaceous southern and northern flora of China. Currently, research on the plants in the transitional region between the northern and southern flora are relatively weak. Our study of specimens has enriched our understanding of the floral landscape in the transitional region between the north and south flora. Cretaceous wood fossils are well preserved in China and 66 species of 29 genera have been reported up to now, which are widely distributed in China. However, in the Cretaceous Shandong Province, there are few records of wood fossils. So far, only one genus and two species have been reported. In this paper a new material of fossil wood is described from the Early Cretaceous Zhifengzhuang Formation of Laiyang Group in Jingzhi area of Anqiu City, Jiaolai Basin, Shandong Province. The present specimen has uniseriate to triseriate pits on the radial walls of tracheids, taxodioid cross-field pitting and other characters. This discovery contributes to a better understanding of fossil wood diversity in Jiaolai Basin during the Cretaceous. Through the well preserved growth rings of the specimens, it can be inferred that the environmental paleoclimate of the Early Cretaceous in Shandong Province was generally arid, with some areas being humid.

A new gansuid bird (Avialae, Euornithes) from the Lower Cretaceous (Aptian) Jiufotang Formation of Jianchang, western Liaoning, China

The study of the Cretaceous birds closest to the living euornithine species has mainly focused on the evolutionary patterns leading to the modern group. Yet, the morphological and ecological diversity of the euornithine branches not directly ancestral to the crown-group is probably underestimated. A new euornithine bird, Shuilingornis angelai gen. et sp. nov., is erected based on a nearly complete skeletal material from the Early Cretaceous (Aptian) Jehol Biota in western Liaoning, China. The new taxon is similar to the penecontemporary gansuids, yet it differs in the smaller body size and in the retention of plesiomorphic features widespread among non-gansuid euornithines. The osteohistological analysis indicates that Shuilingornis gen. nov. represents an early adult stage at the time of death. The phylogenetic analysis robustly supports the referral of Shuilingornis gen. nov. to Gansuidae. Except for the controversial Hollanda, the gansuids have been uncovered from four Aptian basins deposited under similar paleoclimatic conditions. Gansuid success in the middle part of the Cretaceous demonstrates that the exploration of semi-aquatic ecologies was a consistent euornithine pattern which preceded the later ornithurine radiation.

Bio-molecular analyses enable new insights into the taphonomy of feathers.

Exceptionally preserved feathers from the Mesozoic era have provided valuable insights into the early evolution of feathers and enabled color reconstruction of extinct dinosaurs, including early birds. Mounting chemical evidence for the two key components of feathers-keratins and melanins-in fossil feathers has demonstrated that exceptional preservation can be traced down to the molecular level. However, the chemical changes that keratin and eumelanin undergo during fossilization are still not fully understood, introducing uncertainty in the identification of these two molecules in fossil feathers. To address this issue, we need to examine their taphonomic process. In this study, we analyzed the structural and chemical composition of fossil feathers from the Jehol Biota and compared them with the structural and chemical changes observed in modern feathers during the process of biodegradation and thermal degradation, as well as the structural and chemical characteristics of a Cenozoic fossil feather. Our results suggest that the taphonomic process of feathers from the Cretaceous Jehol Biota is mainly controlled by the process of thermal degradation. The Cretaceous fossil feathers studied exhibited minimal keratin preservation but retained strong melanin signals, attributed to melanin's higher thermal stability. Low-maturity carbonaceous fossils can indeed preserve biosignals, especially signals from molecules with high resistance to thermal degradation. These findings provide clues about the preservation potential of keratin and melanin, and serve as a reference for searching for those two biomolecules in different geological periods and environments.

The smallest known specimen of Microraptor (Dinosauria: Dromaeosauridae) from the Jiufotang Formation in northeastern China

ABSTRACT The Early Cretaceous Jehol Biota in northeastern China has yielded a diversity of feathered dromaeosaurid dinosaurs and expanded our knowledge of avian origin and flight evolution. However, histology-based ontogenetic references and detailed morphological studies remain limited relative to the abundant fossils. Here, a new specimen of microraptorine from the Lower Cretaceous Jiufotang Formation is described. This specimen includes a nearly complete postcranial skeleton and inferred as a Microraptor based on revised osteological characters. The femoral length of the new specimen is less than 5 cm, making it the smallest dromaeosaurid individual reported from the Jehol Biota until now. Osteohistological analysis reveals that this individual was a juvenile that is less than one-year old. The new specimen provides additional morphological details that are poorly preserved in the other Microraptor specimens, including aspects of the coracoid, ilium, and tail. Additionally, the sacrals and pubic symphysis of the new specimen have respectively fused at the juvenile stage. This phenomenon suggests caution should be taken in using skeletal fusion for assessing the ontogenetic stage of Microraptor specimens, highlighting the importance of histological analysis.

Jurassic–Cretaceous boundary theropod tracks from the slope of the Fallen Feng, Chicheng, China: review and new observations

ABSTRACT The Tuchengzi Formation represents a Jurassic – Cretaceous boundary regional lithological unit that bridges the temporal gap between the Yanliao biota and the Jehol biota. Tetrapod tracks represent the most significant vertebrate fossil records in the formation, and can be employed to supplement the Late Jurassic fauna and palaeoecological data from northern China. Here, we present a re-analysis of the theropod tracks from the Luofenggou site in northern Hebei Province, utilising an additional 3D model and a locomotory analysis to provide further insights into the ecological context. A morphological analysis indicates that these tracks are more similar to Grallator than to the previously proposed Therangospodus. The latter is diagnosed by coalesced, elongate, oval digital pads lacking a separation in distinct phalangeal pads, whereas these are clearly defined in the presented Tuchengzi material. They can therefore be assigned to the widespread G. ssatoi ichnospecies from the Tuchengzi Formation, although they are longer and more variable in size than other G. ssatoi. A general consideration of speed-related locomotive parameters, trackway morphology, and superposition allows for the speculation of the existence of cooperative or predatory relationships between theropod trackmakers that were differentiated by size or stages of ontogeny, but had similar foot structures.

Calibrating the Jehol Biota in the Baiwan Basin of the North Qinling Orogenic Belt, central China

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.

Late Jurassic–Early Cretaceous dinosaur track assemblages from northwestern Hebei Province, China: Implications for paleoenvironment and paleoecology

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.

Taphonomy and Paleoecology of Lycoptera: A Case Study from the Lower Jehol Group in Western Liaoning, Northeastern China

Taphonomy and Paleoecology of Lycoptera: A Case Study from the Lower Jehol Group in Western Liaoning, Northeastern China

Siberian Jehol Biota

Abstract Volcanogenic-sedimentary and coal-bearing deposits, which contain abundant fossils of a lacustrine fauna and terrestrial flora, are widespread in the territory of Transbaikalia (Russia), Mongolia and Northeastern China. These ecosystems are known under the name ‘Jehol Biota’, which occurs in the Yixian and Jiufotang formations. The discovery of ‘feathered’ dinosaurs and of the earliest angiosperms in western Liaoning Province (China) made them world famous. The history of this biota began in the nineteenth century, when the discoveries in Transbaikalia of the remains of conchostracans, ostracods, insects, fish and plants collected during the expedition of A.F. Middendorf were described. The Barremian–Aptian sedimentary sequences of Transbaikalia (Russia), Mongolia and Northeastern China are very similar. The appearance and evolution of the Jehol Biota occurred against the background of extensive volcanism and tectonic revival, after which normal sedimentary rocks were deposited, culminating in relief peneplanation, swamp development and peat formation. The northern limit of the distribution of this biota is determined to be up to c. 54° modern north latitude. The existence of the Siberian Jehol Biota in extreme climatic conditions is confirmed, as was indicated for the Jehol Biota from NE China.

Discovery of the choristodere Hyphalosaurus baitaigouensis from the Lower Cretaceous Jiufotang Formation of western Liaoning, China and its paleobiogeographic significance

The water-living reptile genus Hyphalosaurus was previously discovered in the Lower Cretaceous Yixian Formation bearing the middle Jehol Biota in western Liaoning, China. Two complete skeletons of Hyphalosaurus are reported for the first time from the Jiufotang Formation bearing the late Jehol Biota at two sites in western Liaoning. They show the typical characteristics of Hyphalosaurus baitaigouensis in terms of the contact between some cranial bones and the number of cervical and dorsal vertebrae, and therefore are assigned to H. baitaigouensis. This discovery extends the stratigraphic range of this species from the Yixian Formation to the overlying Jiufotang Formation. This paper further briefly compares the main characteristics of the two skeletons, summarizes the temporal and spatial distribution of Hyphalosaurus, and discusses the palaeogeographic evolution of western Liaoning at the middle and late Jehol Biota stages based on the aquatic habits of Hyphalosaurus and the geological background of western Liaoning. The analytical results show that the volcanic downwarped lakes, with distinct geographical divisions in western Liaoning during the deposition of the Yixian Formation, had not completely disappeared till the deposition of the Jiufotang Formation. The palaeo-lake in the Fuxin-Yixian Basin underwent the process of generation, expansion and shrinkage during the depositional period of the Yixian Formation and finally merged into a large lake. The palaeo-Dalinghe River, which connected the main basins in western Liaoning during the depositional period of the Jiufotang Formation, was formed simultaneously.

Lacustrine varves in the Lower Cretaceous Yixian Formation of western Liaoning, Northeast China: Implications for seasonal to sub-decadal palaeoclimate variability associated with the Jehol Biota and “Dinosaur Pompeii”

The Lower Cretaceous Yixian Formation in western Liaoning, China contains the exceptionally well-preserved Jehol Biota, and includes the famous assemblages known as “Dinosaur Pompeii”. In this study, we focus on the fossil-rich Zhuanchengzi Bed near Yingwoshan, and describe laminated lacustrine successions that show prominent rhythmites to understand subdecadal palaeoclimate variability. We highlight the cyclicity preserved at a millimetre-scale based on analysis of the rhythmic alterations between the light- and dark-coloured carbonate-siliciclastic layers. Coupling petrographic with phase-specific geochemical analyses, we infer these laminated successions represent varves. The light-coloured layers of the couplets, containing dolomite-dominated carbonates, developed during warm seasons as a result of chemical precipitation enhanced by photosynthetic activities and rhythmic changes in the ambient water properties. The dark-coloured layers are mostly composed of siliciclastic and clay minerals representing terrestrial input during cold seasons. Varve thickness variations likely record seasonal climate changes regulated by ancient Asian Monsoons and decade-level cyclicities, such as ENSO-like and solar cycles. Overall, the varve records in the Yixian Formation offer a novel perspective on the palaeoseasonality of the Jehol Biota and provide insights into the dominant climate mode over interannual time scales of the Early Cretaceous greenhouse world.

Source rock and climate model for the Cretaceous Jiufotang Formation, Kazuo Basin, China: Geochemistry and petrography

The Lower Cretaceous Jiufotang Formation, situated in western Liaoning Province, China, has attracted attention for abundant Jehol Biota fossils and the potential to improve understanding of the relationships among climate change, evolution of terrigenous organisms, and organic matter (OM) enrichment in lake systems during the Early Cretaceous. Based on organic petrology and biomarker analyses, this study investigated the depositional environment, OM sources, and enrichment mechanism of Jiufotang mudstone in the Kazuo Basin. Maceral composition shows that the OM source of Jiufotang mudstone shifted from mainly aquatic to terrigenous, and biomarkers such as abundant diterpenoids and retene indicate that terrigenous higher plants were mainly conifers during deposition of the Jiufotang Formation. Pr/Ph ratios (0.07–0.65) show that the studied section was deposited in anoxic bottom water that may be necessary for OM enrichment in lake systems. Gravity flows were accompanied by input of many clastic minerals and oxygenation of bottom waters, which is unfavorable for OM enrichment. Therefore, the best OM enrichment model for lake systems includes anoxic bottom water, stable water column stratification, low sedimentation rates, and high phytoplankton contributions. The climate changed from relatively dry to humid, which drove changes in the OM enrichment model in the lake. More importantly, the climate and terrigenous plant information obtained by biomarkers is useful to reconstruct the ecological environment of the Jehol Biota.

Development of fluvial‐lacustrine systems in the rift basins fostered Jehol Biota origin: Palaeobiogeographic insights on Dabeigou‐type ostracod fauna

The Lower Cretaceous Dabeigou Formation (135–130 Ma) in the Luanping Basin, associated with its contemporary strata in northeastern China, contains the earliest documented fossils of the Jehol Biota. This includes the Luanpingella—Eoparacypris—Ocrocypris ostracod assemblage, referred to in this study as the Dabeigou‐type ostracod fauna (DOF). Ostracods, which are small (0.5–2 mm) aquatic crustaceans, are abundant and easily preserved as fossils. Outlining a clear palaeobiogeographic range of the DOF can help expand the distribution range of the early Jehol Biota, providing valuable information on its origin. Results show that the DOF is mainly distributed in a series of rift basins along the Yanliao area of China to the eastern Transbaikal region of Russia, with a roughly narrow north‐south distribution. Rift basin development in the eastern part of the North China Craton, combined with humid climatic conditions, provided a suitable environment (e.g., fluvial‐lacustrine systems) for the emergence of the Jehol Biota.

Tooth replacement in the early-diverging neornithischian Jeholosaurus shangyuanensis and implications for dental evolution and herbivorous adaptation in Ornithischia

BackgroundTooth replacement patterns of early-diverging ornithischians, which are important for understanding the evolution of the highly specialized dental systems in hadrosaurid and ceratopsid dinosaurs, are poorly known. The early-diverging neornithischian Jeholosaurus, a small, bipedal herbivorous dinosaur from the Early Cretaceous Jehol Biota, is an important taxon for understanding ornithischian dental evolution, but its dental morphology was only briefly described previously and its tooth replacement is poorly known.ResultsCT scanning of six specimens representing different ontogenetic stages of Jeholosaurus reveals significant new information regarding the dental system of Jeholosaurus, including one or two replacement teeth in nearly all alveoli, relatively complete tooth resorption, and an increase in the numbers of alveoli and replacement teeth during ontogeny. Reconstructions of Zahnreihen indicate that the replacement pattern of the maxillary dentition is similar to that of the dentary dentition but with a cyclical difference. The maxillary tooth replacement rate in Jeholosaurus is probably 46 days, which is faster than that of most other early-diverging ornithischians. During the ontogeny of Jeholosaurus, the premaxillary tooth replacement rate slows from 25 days to 33 days with similar daily dentine formation.ConclusionsThe tooth replacement rate exhibits a decreasing trend with ontogeny, as in Alligator. In a phylogenetic context, fast tooth replacement and multi-generation replacement teeth have evolved at least twice independently in Ornithopoda, and our analyses suggest that the early-diverging members of the major ornithischian clades exhibit different tooth replacement patterns as an adaption to herbivory.

Cretaceous fossil birds from China

Abstract The explosive radiation of early birds has been well documented by the extraordinary discoveries of the Early Cretaceous fossil birds in China in the past three decades. They have greatly expanded the diversity, disparity and temporal distribution of Mesozoic birds, refining our knowledge of the evolutionary path leading to the characteristic avian body plan, including feathers and powered flight, locomotion and habitat differentiation, diet and digestion, reproduction and development, feather colours and display. In addition, studies on the geological background of the Jehol Biota that produced the majority of the Chinese Cretaceous birds have provided important clues to our understanding of the taphonomy as well as the interaction between deep geological process and biological evolution in northeastern China and East Asia during the Early Cretaceous. Future multidisciplinary studies are expected to advance our knowledge of the palaeogeography of Early Cretaceous birds, what impacted the changes in the diversity of early birds in China, and the roles that early birds played in the Early Cretaceous terrestrial ecosystem.

冀北四岔口盆地早期热河生物群的埋藏环境分析

冀北四岔口盆地早期热河生物群的埋藏环境分析