Jehol Biota Research Articles

U–Pb SHRIMP age for the Tuchengzi Formation, northern China, and its implications for biotic evolution during the Jurassic–Cretaceous transition

The Late Jurassic–Early Cretaceous Tuchengzi Formation is widespread in North China. Its clastic deposits indicate a tropical, dry, and hot paleoclimate, different from the subtropical, humid, and seasonal climate in the early Middle Jurassic. The sudden environmental change from the Middle to Late Jurassic resulted in a rapid disappearance of the Yanliao/Daohugou Biota, with more than 90% of the species of the Yanliao/Daohugou Biota dying out and replaced by the Early Cretaceous Jehol Biota. Eolian sandstones with large-scale cross-bedding occur within the uppermost part of the Tuchengzi Formation in North China. The sandstones are stratigraphically higher than the tuff previously dated as 139Ma. We obtained two SHRIMP zircon U/Pb ages from the tuff beds. One sample was collected from the tuff in the basal Tuchengzi Formation in northern Hebei and the other from the tuff intercalated in the eolian cross-bedded sandstones in the uppermost Tuchengzi Formation in western Liaoning. Our results show that 154Ma is the oldest age constraint for the Tuchengzi Formation and 137Ma is the youngest age estimate of the formation, providing an age constraint for the transition from the Yanliao Biota to the Jehol Biota.

Chronological evidence for extension of the Jehol Biota into Southern China

The fossils of the Cretaceous Jehol Biota are magnificent, exquisitely preserved and extraordinarily diverse. Strata that may be correlative with the classic Jehol localities are known over much of Central and Eastern China, as well as Korea, Japan, Mongolia and Siberia. It has been previously hypothesized based on fossil assemblages that the Jehol Biota progressively expanded from the classic Jehol area, with younger representatives covering progressively larger geographic ranges. It has been interpreted that the youngest Jehol Biota bearing layers are in the East Anhui province of South China. Here we present robust 40Ar/39Ar dates of 129.0±0.2Ma for one rhyolite sample from the lower Longwanshan Formation and 127.1±1.3Ma and 128.0±0.9Ma for two volcanic samples from the upper Honghuaqiao Formation from the outcrops of Jehol fossils in East Anhui. Our age results indicate that fossils from these formations are time-equivalent to the second phase fossils from the lower Yixian Formation in the western Liaoning, NE China, and the deposition of these beds is at least 6Ma older than previously estimated. Therefore our results suggest that the hypothesis of the Jehol radiation and migration should be reevaluated.

A new species of Microraptor from the Jehol Biota of northeastern China

Herein we describe a new species of Microraptor from northeastern China that provides new information on the characteristics of the genus and anatomical details suggesting a gliding behaviour. Although specimens of Microraptor have been known for at least a decade, the completeness of the new fossil provides additional morphology that highlights the uniqueness of this taxon. The new specimen, Microraptor hanqingi, is the key to understanding the evolutionary significance of hindlimb wings. A four-winged structure present on an organism sharing an evolutionary lineage leading to modern birds implies that gliding was a stage in the development of avian flight. M. hanqingi represents the largest known microraptorian from China with a total length of approximately 1m, and was closely-related to the venomous form, Sinornithosaurus.

A sauropod rib with an embedded theropod tooth: direct evidence for feeding behaviour in the Jehol group, China

Xing, L, Bell, P.R., Currie, P.J., Shibata, M., Tseng, K. & Dong, Z. 2012: A sauropod rib with an embedded theropod tooth: direct evidence for feeding behaviour in the Jehol group, China. Lethaia, Vol. 45, pp. 500–506. A fragmentary rib from the Lower Cretaceous (Barremian) Yixian Formation in northeastern China preserves rare, direct evidence of feeding behaviour by an unidentified theropod. The rib, which comes from the holotype of Dongbetitan, preserves an embedded, broken theropod tooth. Comparison of the tooth with all known theropods from the Yixian Formation suggests that it belongs to a new taxon of medium-sized theropod. Given the large size difference between the sauropod and the theropod and the absence of reactive bone growth around the tooth, the bite likely occurred post-mortem during scavenging. Recognition of a new, medium-sized theropod increases the known diversity of taxa from the Yixian Formation and helps fill a gap in the theropod palaeoecology of that formation, which previously consisted of only small (<2 m) forms. □China, Cretaceous, feeding behaviour, theropod, titanosauriformes, sauropod.

Three new species of aneuretopsychids (Insecta: Mecoptera) from the Jehol Biota, China

Three new species of Jeholopsyche Ren, Shih et Labandeira in the family Aneuretopsychidae, Jeholopsyche completa sp. nov., J. bella sp. nov. and J. maxima sp. nov., are described and illustrated in this paper. These well-preserved specimens were collected from the Early Cretaceous of Yixian Formation, Jehol Biota, Huangbanjigou Village, Liaoning Province, China. The new species enhance our understanding and broaden the diversity of this family, and provide morphological characters for future phylogenetic studies of Aneuretopsychidae. These insects with siphonate proboscides support a previously documented finding that aneuretopsychids were fluid feeders on the secretions and exudates of contemporaneous gymnospermous reproductive structures coexisting in the Yixian Formation. From the proboscis structure and inferred ecological relationships, we believe that these three new species, with proboscid lengths ranging from 3.5 to 14.5 mm, were pollinators of gymnosperm hosts that bore a broad size-range of deep funnel or other tubular structures laden with nectar-like fluid rewards.

Late Jurassic salamandroid from western Liaoning, China.

A Jurassic salamander, Beiyanerpeton jianpingensis (gen. et sp. nov.), from a recently found site in western Liaoning Province, China is the earliest known record of Salamandroidea. As a Late Jurassic record of the group, it extends the range of the clade by ~40 Ma. The Late Jurassic taxon is neotenic and represented by exceptionally preserved specimens, including fully articulated cranial and postcranial skeletons and bony gill structures close to the cheek region. The fossil beds, consisting of dark-brown volcanic ash shales of the Upper Jurassic Tiaojishan (Lanqi) Formation (Oxfordian), underlie trachyandesite rocks that have yielded a SHRIMP zircon U-Pb date of 157 ± 3 Ma. The fossiliferous beds are substantially older than the Jehol Group, including the Yixian Formation ((40)Ar/(39)Ar dates of 122-129 Ma), but slightly younger than the Middle Jurassic Daohugou horizon ((40)Ar/(39)Ar date of 164 ± 4 Ma). The early fossil taxon shares with extant salamandroids derived character states, including: separated nasals lacking a midline contact, angular fused to the prearticular in the lower jaw, and double-headed ribs on the presacral vertebrae. In contrast to extant salamandroids, however, the salamander shows a discrete and tooth-bearing palatine, and unequivocally nonpedicellate and monocuspid marginal teeth in large and presumably mature individuals. The finding provides insights into the evolution of key characters of salamanders, and also provides direct evidence supporting the hypothesis that the split between Cryptobranchoidea and Salamandroidea had taken placed before the Late Jurassic Oxfordian time. In this aspect, both paleontological and molecular data now come to agree.

A neotenic salamander, Jeholotriton paradoxus, from the Daohugou Beds in Inner Mongolia

Over the past 10 years, there has been a wealth of discoveries of fossil salamanders from the Jehol Biota in northern China. These specimens have revealed many new species in addition to establishing probable divergence times and relationships among modern salamander families. Among these are numerous specimens of a neotenic species Jeholotriton paradoxus. In this study, we focused on this particular salamander species because its classification still remains enigmatic. The aim of this research was to determine the relationship of Jeholotriton with respect to other Jehol salamanders as well as modern salamander families. Although Jeholotriton has been described in previous studies, the discovery of new specimens and increasing knowledge of other Mesozoic salamanders has allowed for a more through description of the genus. Jeholotriton is known only from the Daohugou locality in Ningchen, south-eastern Inner Mongolia. It may be close to the base of the modern Urodele radiation, and might provide evidence of their transition from putative ancestors in the Permo-Triassic. We discovered that the fossil Kokartus (family Karauridae) and the living hynobiids (the most primitive group of modern salamanders) Ranodon sibiricus and Hynobius maculosus, as well as Dicamptodontidae tenebrosus all share some similarities with Jeholotriton. However, conclusive relationships could not be confidently established because of the unique combination of mature and larval characteristics in Jeholotriton. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164, 659–668.

Depositional evolution of the Early Cretaceous Sihetun Lake and implications for regional climatic and volcanic history in western Liaoning, NE China

Numerous well-known fossils of the Jehol Biota, including early birds, feathered theropods, primitive mammals, and putative early angiosperms, have been discovered in lacustrine deposits (Lake Sihetun) of the Lower Cretaceous Yixian Formation of western Liaoning province, NE China. Based on extensive field investigations and four high-resolution excavations, we document in detail the spatio-temporal changes of sedimentary facies, facies associations and limnic community relicts, reconstruct the depositional history, and discuss the significance of these deposits regarding the regional climatic and volcanic history. Four phases are recognized in the history of Lake Sihetun. They are: (1) a phase of fluctuating but gradually rising water level indicated by subaerial and shallow-water lacustrine deposits, (2) a lake with beach–nearshore facies along the marginal areas and suspension-dominated lake floor facies in central areas, (3) a lake phase with a lake floor dominated by hyperpycnal flows, and (4) progradation of a fan delta. Two distinct depositional conditions are observed: stratified and unstratified lake intervals. The former occurred mainly during the second phase and produced clay-poor and clay-rich laminae, whereas the latter developed during the other three phases, and were dominated by deposition of subaqueous sedimentary density flows. These alternations of depositional conditions in offshore lacustrine deposits suggest that the Yixian Formation may have formed under a transitional climate regime fluctuating gradually from warm and dry to warm and humid conditions. Resurgent volcanism is inferred to have become stronger during the late phase of lake development based on distribution of deposits characterizing the unstratified lake interval and volcanic rocks of the overlying Upper Lava unit, a higher content of primary pyroclastic fragments, and evidence of strong syndepositional disturbance.

Timing of the earliest known feathered dinosaurs and transitional pterosaurs older than the Jehol Biota

The Early Cretaceous Jehol Biota in China has produced numerous well preserved fossils of feathered theropods and early birds. Recent discoveries of feathered dinosaurs, as well as transitional pterosaurs and a sexually mature individual of Darwinopterus preserved together with an egg from the Daohugou Biota of an earlier age than the Jehol Biota, in northeastern China, have greatly enriched our knowledge of the transition from dinosaurs to birds and primitive to derived pterosaurs. The age estimate of fossils or host strata, however, has proven to be contentious and varies widely from the Middle Jurassic to the Early Cretaceous. Here, we report a SHRIMP U–Pb zircon date unambiguously associated with the fossil horizons, and thus, for the first time, provide an age calibration for the earliest appearance of feathered dinosaurs and transitional pterosaurs. Date results indicate that the feathered dinosaurs of China were present more than 161Ma ago, unquestionably older than Archaeopteryx in Germany, and are the earliest known feathered dinosaurs in the world. Furthermore, feathers appeared in ornithischians before 159Ma rather than late in the Early Cretaceous. The known transitional pterosaurs first emerged before 161Ma. The Daohugou Biota, containing mammals, primitive pterosaurs, insects and plants, in addition to the feathered dinosaurs, was living in Inner Mongolia ,western Liaoning and northern Hebei in northeastern China during the Middle Jurassic.

The first skiff beetle (Coleoptera: Myxophaga: Hydroscaphidae) from Early Cretaceous Jehol Biota

The first skiff beetle fossil and earliest myxophagan,Hydroscapha jeholensisn. sp., is described and illustrated on the basis of a single specimen from the Lower Cretaceous Yixian Formation at Huangbanjigou of Beipiao City, Liaoning Province, Northeastern China. Based on the combination of diagnostic characters of this specimen (e.g., minute and fusiform body, short elytra, tapered abdomen, separated meso- and metacoxae, and 3-segmented tarsi), we suggest that it is a definitive representative of Hydroscaphidae belonging to the widespread hydroscaphid genusHydroscaphaLeConte, 1874. It also represents the only impression fossil of the beetle suborder Myxophaga. This find displays great significance for shedding light on the preservation of the minute aquatic beetles, since it is the first well-preserved impression fossil reported for the suborder, rather than amber inclusion.

Insight into the early evolution of the avian sternum from juvenile enantiornithines

The sternum is one of the most important and characteristic skeletal elements in living birds, highly adapted for flight and showing a diverse range of morphologies. New exceptional material of young juvenile specimens from the Early Cretaceous Jehol Group in northeastern China reveals the unique sequence of development in the sternum of Enantiornithes, the dominant clade of Cretaceous birds. We recognize six ossifications that together form the sternum, three of which were previously unknown. Here we show that although basal living birds apparently have retained the dinosaurian condition in which the sternum develops from a bilateral pair of ossifications (present in paravian dinosaurs and basal birds), the enantiornithine sternal body primarily develops from two unilateral proximo-distally arranged ossifications. This indicates that although superficially similar, the sternum formed very differently in enantiornithines and ornithuromorphs, suggesting that several ornithothoracine sternal features may represent parallelism. This highlights the importance of ontogenetic studies for understanding homology and the evolution of skeletal features in palaeontology.

The evolution of the feather: Sinosauropteryx, life, death and preservation of an alleged feathered dinosaur

Among the spectacular dinosaur fossils reported from the Jehol Group of northeastern China is the most celebrated, Sinosauropteryx, which continues to excite interest in questions concerning feather origins—most recently with alleged identifications of melanosomes and colour in its integumental structures, which proved unfounded. The crucial significance of Sinosauropteryx is undoubtedly the focus on its basal theropod status and potentially pivotal position in informing models of the early evolutionary origin of modern feathers. On the basis of new evidence in Sinosauropteryx NIGP 127587 and GMV 2124, it is shown here that the alleged protofeathers were not free filaments but part of a composite tissue. It is shown that the tail terminates in a unique, smoothly edged, spatula-shaped structure. The dinosaurs died in the vicinity of a lake. For the first time, the taphonomy of Sinosauropteryx is investigated on the basis of aboveground decomposition experiments on living animals so as to get a better understanding of conditions preceding the death of the animal, its death, decomposition and finally preservation of soft tissue as manifested in the fossil. The signs point strongly to invertebrate colonization of the carcass of Sinosauropteryx rather than vertebrate predation or scavenging, with moderate decay associated with the purge fluids while major decay was forestalled by burial, at most a few days after death. Lastly, a theory that the opisthotonic posture of fossils such as Sinosauropteryx NIGP 127587 occurred perimortem as a consequence of neural spasms provides the basis for a forensic reconstruction of the stages leading to the dinosaur’s death and the final preserved position of the external, dorsally preserved soft tissue, which proves to be more consistent with a uniform crest than individual, free protofeathers.

Additional specimen of Microraptor provides unique evidence of dinosaurs preying on birds

Preserved indicators of diet are extremely rare in the fossil record; even more so is unequivocal direct evidence for predator-prey relationships. Here, we report on a unique specimen of the small nonavian theropod Microraptor gui from the Early Cretaceous Jehol biota, China, which has the remains of an adult enantiornithine bird preserved in its abdomen, most likely not scavenged, but captured and consumed by the dinosaur. We provide direct evidence for the dietary preferences of Microraptor and a nonavian dinosaur feeding on a bird. Further, because Jehol enantiornithines were distinctly arboreal, in contrast to their cursorial ornithurine counterparts, this fossil suggests that Microraptor hunted in trees thereby supporting inferences that this taxon was also an arborealist, and provides further support for the arboreality of basal dromaeosaurids.

Taphonomy of Early Cretaceous freshwater bivalve concentrations from the Sihetun area, western Liaoning, NE China

The Early Cretaceous Yixian Formation at Sihetun, Beipiao, western Liaoning, northeastern China, is well-known for yielding diverse and excellently preserved fossils of the Jehol Biota. The lower unit of Yixian Formation, dominated by lacustrine deposits, is rich in concentrations of two freshwater bivalves: Sphaerium anderssoni and Arguniella ventricosa. These bivalve concentrations can be divided into three types that comprise either paucispecific A. ventricosa or S. anderssoni, or both bivalves in similar amounts. The lithological, biotic, and taphonomic features of 12 bivalve concentrations are recorded, and the taphonomic signatures (such as shell articulation, size-frequency distribution, and orientation) are analyzed. Autochthonous as opposed to allochthonous bivalve concentrations are discriminated. A very short time-averaging effect is recognized in some concentrations, which was probably caused by seasonal or episodic water-level fluctuations and hypoxia. Three factors operated on the bivalve concentrations before final burial: in-situ reworking, transport, and time-averaging. Although time-averaging of the death assemblages was limited to several years, it is in this way that several generations of the two bivalve species could become preserved together. Reworking of the bivalve concentrations was most likely caused by storm action.

New material of the Early Cretaceous lizard Yabeinosaurus from China

The Early Cretaceous lizard Yabeinosaurus was one of the first taxa described from the now famous Jehol Biota of northeast China. Misinterpreted for more than 60 years and misclassified as a gekkotan based on juvenile specimens, it is now recognised to be a large, well-ossified lizard with an extended period of skeletal maturation. Here we describe two additional complete specimens of Yabeinosaurus that provide new information on skeletal morphology, most notably of the skull, pectoral girdle, and tail. Both specimens also preserve gut contents, showing that large individuals took vertebrate prey, including fish. A more complete understanding of Yabeinosaurus permits a review of the type specimen of Yabeinosaurus youngi. Skull traits used to distinguish Y. youngi from Yabeinosaurus tenuis are invalid but, as noted by Hoffstetter, the two species differ markedly in limb proportions. Attribution of Young’s specimen to Yabeinosaurus is equivocal, but could potentially extend the temporal range of the lineage into the Jurassic. A new phylogenetic analysis based on a morphological data set places Yabeinosaurus on the stem of Scleroglossa, as the sister taxon of the contemporaneous Japanese lizard Sakurasaurus.

Prophaenognatha, a New Aclopinae Genus from the Yixian Formation, China and Its Phylogenetic Position Based on Morphological Characters (Coleoptera: Scarabaeidae)

Prophaenognatha robusta gen. et sp. nov. (Scarabaeoidea: Scarabaeidae: Aclopinae), the best-preserved aclopine fossil so far, is described and illustrated from the Upper Jurassic-Lower Cretaceous Yixian Formation of the Jehol Biota, western Liaoning Province, NE China. The key to extinct and extant genera of Aclopinae is given and the monophyly of extant and fossil Aclopinae lineages is supported by five character states. The new taxon provides evidence about the evolution of Scarabaeoidea with its phylogenetic position inferred based on 68 morphological characters.

A New Brachyceran Family Origoasilidae Fam. Nov. from the Late Mesozoic of China (Insecta: Diptera)

Abstract:Lower brachyceran flies are abundant in the Late Mesozoic of China. Many extant and extinct members of that have been found in Inner Mongolia, Liaoning, Hebei and Shandong provinces. A new family, Origoasilidae fam. nov., belonging to the lower Brachycera, is built based on a new specimen from the Yixian Formation and is a representative of the Jehol Biota. The new endemic Mesozoic family possesses several unique characters in the wing. The relationship among the Origoasilidae fam. nov. and relative known lower brachyceran flies has been discussed.

Prophaenognatha, a New Aclopinae Genus from the Yixian Formation, China and Its Phylogenetic Position Based on Morphological Characters (Coleoptera: Scarabaeidae)

Abstract:Prophaenognatha robusta gen. et sp. nov. (Scarabaeoidea: Scarabaeidae: Aclopinae), the best‐preserved aclopine fossil so far, is described and illustrated from the Upper Jurassic‐Lower Cretaceous Yixian Formation of the Jehol Biota, western Liaoning Province, NE China. The key to extinct and extant genera of Aclopinae is given and the monophyly of extant and fossil Aclopinae lineages is supported by five character states. The new taxon provides evidence about the evolution of Scarabaeoidea with its phylogenetic position inferred based on 68 morphological characters.

A well-preserved aneuretopsychid from the Jehol Biota of China (Insecta, Mecoptera, Aneuretopsychidae)

The Aneuretopsychidae is an unspeciose and enigmatic family of long-proboscid insects that presently consist of one known genus and three species from the Late Jurassic to Early Cretaceous of north-central Asia. In this paper, a new genus and species of fossil aneuretopsychid is described and illustrated, Jeholopsyche liaoningensis gen. et sp. n. Fossils representing this new taxon were collected from mid Early Cretaceous strata of the well known Jehol Biota in Liaoning Province, China. This finding documents the first formal record of fossil Aneuretopsychidae in China. In addition, this well-preserved and new material reveals previously unknown and detailed morphological structure of the mouthparts, antennae, head, thorax, legs and abdomen of this distinctive insect lineage.

Dynamics of the lacustrine fauna from the Early Cretaceous Yixian Formation, China: implications of volcanic and climatic factors

Pan, Y., Sha, J., Fursich, F.T., Wang, Y., Zhang, X. & Yao, X. 2011: Dynamics of the lacustrine fauna from the Early Cretaceous Yixian Formation, China: implications of volcanic and climatic factors. Lethaia, Vol. 45, pp. 299–314. The taphonomy and palaeoecology of the famous Lower Cretaceous Jehol biota of northeastern China are two of its least resolved aspects. The biota occurs in lacustrine sediments characterized by abundant volcanic ash layers. The general view is that these tuff layers correlate strongly with vertebrate mass mortality events. However, though aquatic invertebrates also suffered mass mortality, in the majority of cases individuals tend to occur on bedding planes of finely laminated sediments, suggesting that each mass mortality event is not related to volcanic activity. Based on data collected in the course of two excavations at Zhangjiagou and Erdaougou, the role of volcanic activity and other factors that could have controlled the dynamics of the fauna were investigated. Cluster analyses of fossil assemblages from both localities show similar results, and eight fossil communities are recognized. In the lacustrine Yixian Formation, frequent and often severe volcanic activity represented by the abundant tuff layers influenced the water quality, causing repeated collapse of the aquatic ecosystem. Bedding planes with remains of the eight different communities were analysed, each recording the community dynamics of a shallow eutrophic lake system that was most probably controlled by fluctuations of oxygen level related to climate. A mortality model, in which oxygen-level fluctuations play the decisive role, is proposed to explain the existence and distribution of the fossil communities, as well as the unfossiliferous layers. □China, Jehol biota, lacustrine community, mass mortality, palaeoclimate, volcanic activity.