Early Cretaceous Yixian Formation Research Articles

Extremely rapid, yet noncatastrophic, preservation of the flattened-feathered and 3D dinosaurs of the Early Cretaceous of China

Northeast China's Early Cretaceous Yixian Formation preserves spectacular fossils that have proved extraordinarily important in testing evolutionary hypotheses involving the origin of birds and the distribution of feathers among nonavian dinosaurs. These fossils occur either flattened with soft tissue preservation (including feathers and color) in laminated lacustrine strata or as three-dimensional (3D) skeletons in "life-like" postures in more massive deposits. The relationships of these deposits to each other, their absolute ages, and the origin of the extraordinary fossil preservation have been vigorously debated for nearly a half century, with the prevailing view being that preservation was linked to violent volcanic eruptions or lahars, similar to processes that preserved human remains at Pompeii. We present high-precision zircon U-Pb geochronology from cores and outcrops, demonstrating that Yixian Formation accumulation rates are more than an order of magnitude higher than usually estimated. Additionally, we provide zircon provenance and sedimentological data from 3D dinosaur fossils, which imply that their death and burial occurred in collapsed burrows, rather than via a catastrophic volcanogenic mechanism. In the studied area, the three principal fossil-rich intervals of the Yixian occur as a cyclic sequence that correspond to periods of high precipitation. Using Bayesian-Markov Chain Monte Carlo approaches, we constrain the total duration of the sequence to less than ~93,000 y and suggest that climatic precession paced the expression of these cyclic sediments. Rather than representing multiple, Pompeii-like catastrophes, the Yixian Formation is instead a brief snapshot of normal life and death in an Early Cretaceous continental community.

Early Cretaceous solar cycles recorded in lacustrine laminations in North China

Solar cycles are important moderators of the Earth’s global climate system. Although modern-day solar cycles are well known, they have been less studied over geological time. High-resolution records such as varves have been previously used for reconstructing solar cycles from the Paleoproterozoic through Quaternary. In this paper, very fine (<1 mm) sedimentary laminations of the Early Cretaceous Yixian Formation in Xiushui Basin were studied in Northern Liaoning Province, North China. Two different microfacies of the striped shale in the Third Member of the Yixian Formation were identified. These include the light-gray to gray siltstone (Mf 1) and the gray to black organic-rich mudstone (Mf 2). Laminations of Mf 2 are mainly made of biofilms. Sub-millimeter scaled couplets of biofilm and siliciclastic-rich sublamina record seasonal growth and withering of microbial mats during the warm season (summer) and cold season (winter), respectively. Evolutionary spectral analyses of three binary rank series (the binary boxcar series, triangle series, and midpoint-triangle series), varve couplet thickness and gray scale image data (gray data) show multiple periodicities consistent with solar cycles, including the robust Schwabe sunspot cycle (10.0–10.6 year) and solar Bruckner cycle (31.0–40.6 year), and relatively weaker signals for the solar Hale cycle (21.9 year) and 16.5-year solar cycles that have been linked to solar magnetic activity. Solar cycles recognized in this paper indicate the total solar irradiance (TSI) influenced microbial mat growth in the Early Cretaceous in North China. Further, we extend our new record with a compilation of varve-recorded sunspot cycles throughout geological time to show that the 11-year Schwabe sunspot cycle and the 22-year Hale cycle have persisted since the Paleoproterozoic.

Gemological Characteristics and Origin of the Zhanguohong Agate from Beipiao, Liaoning Province, China: A Combined Microscopic, X-ray Diffraction, and Raman Spectroscopic Study

The Zhanguohong agate from Beipiao (Liaoning province, China), which occurs in the intermediate–felsic volcanic breccias of the Early Cretaceous Yixian Formation, generally shows massive and banded structures, with red, yellow, and/or white layers or zones. Little research has been done on its mineralogical and gemological characteristics or its genesis. In this study, we present petrographic and spectroscopic constraints on the mineral composition and micro-texture of the silica matrix, as well as the ferruginous inclusions within the agates, in order to deduce the origin of the Zhanguohong agate. According to the microscopic observations, sandwich-like interlayered micro-granular quartz, fibrous chalcedony, and jigsaw quartz bands are common in the banded agates. X-ray diffraction (XRD) and Raman spectroscopic analyses revealed that all of the samples were mainly composed of α-quartz and moganite, with minor hematite and goethite. The moganite content (17–54 wt%) of the silica matrix decreases by varying degrees from the outermost to the innermost part of the banded agates. The crystal defects and ferric iron in the microcrystalline silica grains probably contributed to the moganite crystallization. The red, yellow, and orange zones are rich in hematite, goethite, and their mixtures, respectively. The ore-forming fluids fluctuated between acidic and alkaline within a temperature range of 100–200 °C and at a sustained positive Eh. Combined with the field observations, these results suggest that the multiperiod precipitation of the agates probably resulted from the episodic volcanic activity during the Early Cretaceous lithospheric extension in eastern China.

A new cockroach (Insecta: Blattaria: Blattulidae) from the Lower Cretaceous Laiyang Formation of China

The Blattulidae is an extinct family of cosmopolitan Mesozoic cockroaches with a low generic diversity. Habroblattula laiyangensis sp. nov. from the Lower Cretaceous Laiyang Formation of Shandong Province of China with well-preserved both hind wings is only closely related to the H. drepanoides Wang, Liang & Ren, 2007 from the Early Cretaceous Yixian Formation, sharing the venation pattern, while being significantly smaller, and provides new characteristics of ancient Blattulidae. In addition, H. laiyangensis sp. nov. resembles distribution patterns of a closely related complex of “Piniblattella” yixianensis Gao, Shih & Ren, 2018 with “Mesoblattina” sinica Ping, 1928, suggesting a spatiotemporal paleobioprovincial relation among Laiyang and Yixian formations, former probably representing more warmer southern localities. Laiyangia Grabau, 1923 and Sinoblatta Grabau, 1923 are indigenous to Laiyang and lack analogues also in numerous Cretaceous Mongolian and Russian sites evidencing a degree of isolation.

Phylogeny of Evanioidea (Hymenoptera, Apocrita), with descriptions of new Mesozoic species from China and Myanmar

AbstractThe phylogeny of the superfamily Evanioidea is presented using morphology and DNA sequence data of selected extant and fossil genera by employing two phylogenetic methods, maximum parsimony and Bayesian inference. Based on our new results, the monophyly of Evanioidea is corroborated. Evanioidea, Anomopterellidae, Othniodellithidae, Andreneliidae and Evaniidae are monophyletic families, while Praeaulacidae, Aulacidae, Baissidae and Gasteruptiidae are paraphyletic families. In addition, four new genera (Sinuevaniagen.n.,Curtevaniagen.n.,Exilaulacusgen.n.,Heterobaissagen.n.) with five new species (Sinuevania mirasp.n.,Curtevania enerviasp.n.,Exilaulacus loculatussp.n.,Exilaulacus latussp.n.,Heterobaissa apetiolasp.n.), and five additionally new species (Newjersevania longasp.n.,Newjersevania brevissp.n.,Cretevania tenuissp.n.,Cretevania venaesp.n.,Praeaulacus rectussp.n.) and one new combination [Cretevania mitis(Li, Shih & Ren, 2014a)comb.n.] are described based on well‐preserved fossils from the Middle Jurassic Jiulongshan Formation in Inner Mongolia, China, the Early Cretaceous Yixian Formation in Liaoning, and mid‐Cretaceous amber from Myanmar. This study documents the diversification of one major lineage of the mid‐Mesozoic parasitoid revolution that dramatically changed food‐web relationships in terrestrial ecosystems.This published work has been registered in ZooBank,http://zoobank.org/urn:lsid:zoobank.org:pub:CBC04ADA‐0176‐402D‐9B43‐E1B3CDA080E1.

Cranial morphology of Sinovenator changii (Theropoda: Troodontidae) on the new material from the Yixian Formation of western Liaoning, China.

A new three-dimensionally preserved troodontid specimen consisting of most of the skull, partial mandibles and six articulated cervical vertebrae (PMOL-AD00102) from the Early Cretaceous Yixian Formation of Beipiao, western Liaoning, China is identified as Sinovenator changii on the basis of a surangular with a “T”-shaped cross-section. High-resolution computed tomographic data for the skull of this new specimen facilitated a detailed description of the cranial anatomy of S. changii. New diagnostic features of S. changii include a well-developed medial shelf on the jugal, a slender bar in the parasphenoid recess, a lateral groove on the pterygoid flange of the ectopterygoid, and the lateral surface of the anterior cervical vertebrae bearing two pneumatic foramina. Our new observation confirms that the braincase of Sinovenator is not as primitive as previously suggested, although it still shows an intermediate state between derived troodontids and non-troodontid paravians in having an initial stage of the subotic recess and the otosphenoidal crest. Additionally, this new specimen reveals some novel and valuable anatomical information of troodontids regarding the quadrate-quadratojugal articulation, the stapes, the epipterygoid and the atlantal ribs.

Maternal care by Early Cretaceous cockroaches

Most cockroaches produce a special capsular structure, the ootheca, to enclose eggs for protection and maternal brood care. However, the origin and early evolution of the cockroach ootheca is poorly known, attributable to a lack of fossil evidence from the Mesozoic. Here, we report the earliest known cockroach fossil possessing an internally partitioned ootheca: Piniblattella yixianensis Gao, Shih & Ren sp. nov. is described from the mid Early Cretaceous Yixian Formation of China. The ootheca of this species measures 46–62% of its body length, contains 60–70 eggs, and exhibits the oviparity B reproduction mode, similar to that of the extant ectobiid and blattid cockroaches. In conjunction with several isolated ootheca specimens preserved in the mid-Cretaceous Myanmar amber (Burmite), we infer that the cockroach reproductive mode using the complete oothecate structure occurred during or before the mid Early Cretaceous. Maternal care associated with the oothecate condition in these Cretaceous cockroaches added a unique and major life-history trait, later resulting in true viviparity. This new life-history trait providing maternal protection and care may have been a key factor in the subsequent evolutionary diversification and ecological expansion of modern cockroach lineages.http://zoobank.org/urn:lsid:zoobank.org:pub:588C91F4-FB8D-43E5-8C2D-86D50393B851

The source and paleoclimatic implication of hydrogen isotopic composition of n-alkanes in sediments from the Yixian Formation, western Liaoning Province, NE China

Hydrogen isotopic composition of n-alkanes was measured in sediments from an excavated profile of the Early Cretaceous Yixian Formation in Liaoning Province, NE China, aiming to assess the significance of the δD value of n-alkanes in ancient lacustrine sediments as the indicator for determining the source inputs of organic matters and paleoclimatic conditions. The δD values of n-alkanes are in the range of −250‰ to −85‰ and display an obvious three-stage variation pattern through the profile, which is consistent with the distribution of the dominated n-alkanes and the profile of their δ13C values. The δD and δ13C values of n-alkanes suggest that short-chain n-alkanes are primarily derived from photosynthetic bacteria and algae; n-C29 and n-C31 are mainly originated from terrestrial higher plants; n-C28 and n-C30 may be derived from the same precursor but via the different biological mechanism of hydrogen isotopic fractionation; while the source inputs of medium-chain n-alkanes are more complicated, with n-C23 being derived from some specific algae or biosynthesized by various aquatic organisms. The paleoclimatic conditions are reconstructed via two approaches. The reconstructed hydrogen isotopic values of lake water and meteoric water (expressed as δDLW and δDMW, respectively) were at the intervals of −51.8‰ to 17.0‰ and −118.1‰ to −43.5‰, respectively, indicating a general climate transition from semi-arid to arid. The calculated ΔδDLW-MW values vary from 37.0‰ to 89.1‰ and display a similar but a significant large-scale variation trend with the ΔδDC23‐long (−28.8‰ to 85.0‰; long represents long-chain n-alkanes) and ΔδDmid-long (−15.4‰ to 43.4‰; mid represents medium-chain n-alkanes) values. The discrepancy may be attributed to the source input overlap for n-alkanes and the uncertainties of εwater/lipid values. The coupling of ΔδDC23‐long, ΔδDmid-long and ΔδDLW-MW values with the paleoclimatic evidence indicates that the δD values of n-alkanes could be more sensitive to the change of paleoclimatic conditions.

Microbial–caddisfly bioherms in the Early Cretaceous Yixian Formation in the Yixian Basin, Western Liaoning, China

Microbial–caddisfly bioherms have recently been discovered in the Early Cretaceous Yixian Formation in Western Liaoning, China. They consist of thousands of aggregated caddisfly larval cases that are generally vertically oriented and parallel to each other. These cases are similar in size, 12–14 mm long with an inside diameter of 2 mm and an outside diameter of 3–4 mm. Three kinds of particles were principally identified occurring on the case surface and were used as the basis for dividing them into three types. In addition to biohermal cases, there are single caddisfly cases that are widely distributed in the Yixian Basin. Nevertheless, the identity of the environmental conditions responsible for fabrication is difficult to establish. An analysis of microbial–caddisfly bioherms globally revealed that their formation occurs under dry conditions within warm-temperate to xeric climates.

ADichocarpum-like Angiosperm from the Early Cretaceous of China

The Yixian Formation (the Early Cretaceous) of China has yielded a diverse group of early angiosperms, revealing the charm of angiosperms from the formation is far from finishing. Here we report a fossil angiosperm, Nothodichocarpum gen. et sp. nov, with physically connected female parts, male parts, branches, and leaves with pinnate reticulate venation from the Yixian Formation of Liaoning, China. In addition to the previous reports, this report underscores the diversity of angiosperms in the Early Cretaceous Yixian Formation and earlier origin of angiosperms. The morphological variations in the reproductive parts in different stages allow us to infer the development of this early angiosperm. This fossil plant demonstrates a unique character assemblage that sheds new light on the origin and evolution of carpels.

A new species of Lasiosmylus from the Early Cretaceous, China clarifies its genus-group placement in Ithonidae (Neuroptera).

A new species, Lasiosmylus longus sp. n., is described from the Early Cretaceous Yixian Formation of Huangbanjigou Village, Liaoning Province, China. Based on the characters of the new species and nine new specimens of Lasiosmylus newi Ren & Guo, 1996, the generic diagnosis of Lasiosmylus is emended and the taxonomic position of Lasiosmylus Ren & Guo, 1996 is re-evaluated, and Lasiosmylus should be assigned to the ithonid genus-group.

Phylogenetic position of the extinct insect family Vetanthocoridae (Heteroptera) in Cimiciformes

The extinct fossil family Vetanthocoridae, with the tribes Vetanthocorini and Crassicerini, was considered a member of the Cimicoidea. Because the tribe Vetanthocorini has been transferred to Nabidae, the systematic position of Vetanthocoridae is in doubt. Punctivetanthocoris pubens gen. et sp. nov. from the Early Cretaceous Yixian Formation of China is assigned to Vetanthocoridae. Based on the combination of fossil and extant taxa, two cladistic analyses were conducted to confirm the phylogenetic position of the fossil family Vetanthocoridae within Cimiciformes and Cimicoidea. The monophyly of Cimiciformes and Cimicoidea is supported. The fossil family Vetanthocoridae is included in Cimicoidea, and forms a monophyletic group with the extant flower bugs.http://zoobank.org/urn:lsid:zoobank.org:pub:404279F9-D9F7-4871-A7C7-9839E62139BD

Sedimentary organic matter record of Early Cretaceous environmental changes in western Liaoning Province, NE China

The abundance and composition of organic matter and the δ13C compositions of some specific individual compounds were analysed in sediments collected from an excavated profile of the Early Cretaceous Yi-xian Formation in Liaoning Province, NE China, in order to provide organic geochemical information on palaeoclimate and environmental changes. The distribution of n-alkanes varies steadily through the profile, with long-chain n-alkanes dominating in the lower and upper sections, and medium chain-length n-alkanes dominating in the middle section of the profile. The δ13C values of n-alkanes, hopanes and steranes show similar upward positive trends through the profile, suggesting that these compounds originated from the same source material and also reflect consistent changes in the environment of the sedimentary basin. The C24 17,21-secohopane was only detected in the lower and middle sections of the profile and has a more positive carbon isotopic composition by about 3.7–6.7‰ than that of associated n-alkanes, hopanes, steranes and C30 8,14-secohopane. This implies that the C24 17,21-secohopane had a different origin, possibly connected with the volcanic ash deposits and massive vertebrate remains. Reconstruction of the δ13C composition of atmospheric CO2 based on plant-derived C29 and C31n-alkanes shows a change from −10‰ to −3‰ from the bottom to the middle of the profile. This upward positive excursion through the profile is consistent with the worldwide variation of atmospheric CO2 during the Early Cretaceous and indicates an upward warming trend, likely related to globally intensified volcanic activity.

Parallel evolution of leaf morphology in gnetophytes

In the present paper, an ephedroid macrofossil species from the Early Cretaceous Yixian Formation of western Liaoning of China is described as new to science: Ephedra multinervia Yang et Lin, sp. nov. This species has typical ephedroid morphology, e.g. the dichasial branching shoot system, swollen nodes, internodes having many fine longitudinal striations and opposite phyllotaxy. Ephedra multinervia has strap-shaped leaves with multiple dichotomizing veins and reduced female cones with a single pair of fertile bracts forming a cupule enclosing two inner seeds. Ephedra multinervia is similar to Ephedra archaeorhytidosperma Yang et al. and Ephedra hongtaoi Wang et Zheng in its reduced bi-ovulate female cone, but differs from the latter two species by the lengthy strap-like leaves bearing multiple parallel veins and its sessile female cones. A new evolutionary hypothesis of the gnetophytes is proposed based on a synthesis of reproductive morphology of macrofossils from the Early Cretaceous and modern representatives. A Chengia-like precursor might have given rise to the Gnetum-Welwitschia clade by diversification of leaf morphology and female reproductive organs. According to this new explanation, the Welwitschia-like strap-like leaves with multiple parallel veins in E. multinervia result from convergence.

Macrofossil evidence unveiling evolution and ecology of early Ephedraceae

The Early Cretaceous Yixian Formation from western Liaoning in northeastern China is well known for its extremely high diversity of plant macrofossils including important basal members of the Gnetales. The Gnetales from the Yixian Formation currently play a significant role in our present understanding of evolution and adaptation within the group. In the present paper the ephedroid macrofossil genus Prognetella Krassilov et Bugdaeva previously known from the Early Cretaceous of Transbaikalia in southern Russia is revised based on additional specimens from the Yixian Formation. Baicarpus Gang Han et al., a recently described genus interpreted as an angiosperm is reduced to synonymy and reinterpreted as a member of the Gnetales, and placed within the genus Prognetella. Reproductive shoots of Prognetella consist of nodes and internodes, and each of these constitutes a lax compound female spike; foliar bracts are paired at each node, and each foliar bract usually encloses a reproductive unit; the paired female reproductive units together with their subtending bracts and the supporting peduncle constitute a diaspore. The diaspore was abscised from the lower node and disseminated when the plant ripened. A cladistic analysis was conducted based on morphological characters of reproductive organs to understand the evolution of early Ephedraceae. The result suggests that Prognetella is transitional between the genera Siphonospermum Rydin et Friis and Chengia Yang et al. and further illustrates the reduction and sterilization hypothesis previously proposed within the Ephedraceae. In addition, this study discovered a new and unusual dispersal mechanism within the basal members of the Ephedraceae.

Early Cretaceous Archaeamphora is not a carnivorous angiosperm.

Archaeamphora longicervia H. Q. Li was described as an herbaceous, Sarraceniaceae-like pitcher plant from the mid Early Cretaceous Yixian Formation of Liaoning Province, northeastern China. Here, a re-investigation of A. longicervia specimens from the Yixian Formation provides new insights into its identity and the morphology of pitcher plants claimed by Li. We demonstrate that putative pitchers of Archaeamphora are insect-induced leaf galls that consist of three components: (1) an innermost larval chamber; (2) an intermediate zone of nutritive tissue; and (3) an outermost wall of sclerenchyma. Archaeamphora is not a carnivorous, Sarraceniaceae-like angiosperm, but represents insect-galled leaves of the previously reported gymnosperm Liaoningocladus boii G. Sun et al. from the Yixian Formation.

Exceptional preservation of clam shrimp (Branchiopoda, Eucrustacea) eggs from the Early Cretaceous Jehol Biota and implications for paleoecology and taphonomy

AbstractFossil eggs of clam shrimps (Spinicaudata) are rare and little attention has been paid to the study of their shape and microstructures. Here, we report the discovery of exceptionally preserved three-dimensional eggs from numerous specimens ofEosestheria ellipticaChen, 1976 from the lacustrine Early Cretaceous Yixian Formation in western Liaoning, China. These three-dimensionally preserved fossil eggs display a spherical shape with smooth surface, part of the tertiary envelope, and possibly the first embryonic cuticle, which were previously unknown or ambiguous. The eggs are abundant and assumed to be attached to the exopod as in extant Spinicaudata. Moreover, the exceptional three-dimensional preservation and delicate preparation of slices of the eggs allowed us to document the microstructures and elemental composition of fossil eggs of clam shrimps from the Jehol Biota. Energy dispersive spectroscopy of the fossilized envelope revealed a calcium phosphate composition. However, the egg contents display two completely different elemental compositions. Some exhibit the same elemental composition as the envelope, whereas others has been replaced by alumino-silicate. The taphonomic process is also briefly discussed in this paper.

New fossil ephialtitids elucidating the origin and transformation of the propodeal-metasomal articulation in Apocrita (Hymenoptera).

BackgroundApocrita has a special structure that its first abdominal segment has been incorporated into the thorax as the propodeum. The remaining abdomen, metasoma, is connected to this hybrid region via a narrow propodeal-metasomal articulation forming a “wasp waist”, which serves an important function of providing maneuverability, flexibility and posture for oviposition. However, the origin and transformation of the propodeal-metasomal articulation are still vague. Ephialtitidae, as the basal group of Apocrita from the Early Jurassic to the Early Cretaceous, have shown various types of propodeal-metasomal articulations.ResultsThis study describes and illustrates two new genera with three new species, Acephialtitia colossa gen. et sp. nov., Proephialtitia acanthi gen. et sp. nov. and P. tenuata sp. nov., collected respectively from the Early Cretaceous Yixian Formation at Liutiaogou and the Middle Jurassic Jiulongshan Formation at Daohugou, both in Inner Mongolia, China. These genera are assigned to the Ephialtitidae based on their complete wing venation, e.g. 2r-rs, 2r-m, 3r-m and 2 m-cu always present in the forewings and Rs, M and Cu in the hind wings. These new fossil ephialtitids have well-preserved propodeal-metasomal articulations indicating metasoma is broadly attached to propodeum.ConclusionThe broad articulation between the propodeum and metasoma in basal Ephialtitidae, likely passed on from a still more basal family Karatavitidae, suggests three separate pathways of the transformation of the “wasp waist” in three different derived lineages leading from Ephialtitidae to: (i) Kuafuidae and further to the remaining Apocrita, (ii) Stephanidae, and (iii) Evanioidea. In addition, the demise of ephialtitid wasps lagging behind the flourishing of angiosperms suggests that ephialtitid extinction might have been mainly driven by competition with numerous new taxa (eg. the abundant Cretaceous xylophilous Baissinae and Ichneumonoidea) appeared just before or/and soon after the J/K boundary.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0317-1) contains supplementary material, which is available to authorized users.

Biostratinomic analysis of Lycoptera beds from the Early Cretaceous Yixian Formation, western Liaoning, China

AbstractLittle is known about the palaeoenvironments of the Early Cretaceous lakes of western Liaoning. Uncertainties exist especially about the water depth, water temperatures and annual temperature fluctuations. Here, we analyse the preservation of the most abundant fish of the lakes, the teleost Lycoptera, articulated skeletons of which occur in large concentrations suggestive of mass mortality. Taphonomic features such as degree of disarticulation, orientation patterns and displacement of skeletal elements reveal distinct preservational patterns. They suggest that the water temperature was low during winter and exhibited pronounced seasonal fluctuations. The depth of the lakes was not deep. Possible causes of the fish mortality are discussed, of which anoxia is favoured. This leads to a more refined palaeoenvironmental model for these palaeolakes, which harbour one of the most important Mesozoic Lagerstätten.

Mesozoic cribellate spiders (Araneae: Deinopoidea) from China

This study describes a new spider with the most numerous specimens (c. two-thirds) known from the Middle Jurassic Jiulongshan Formation of Daohugou, China, as Zhizhu daohugouensis gen. et sp. nov, together with a related form from the Early Cretaceous Yixian Formation of Huangbanjigou, Zhizhu jeholensis sp. nov., and another, unnamed, specimen known only from an immature female from Daohugou. These spiders are all placed in the stem-Deinopoidea. Two recent studies of the phylogeny of spiders using phylogenomics have shown that deinopoids may be closer to non-orb-weaving cribellates than to ecribellate orbicularians, and that if the evolution of the orb web is a unique event, then it occurred deeper in time, perhaps among early Mesozoic cribellates such as these. The new spiders described here contribute to knowledge of the biodiversity and palaeoecology of the forested lake margins of the North China Block in mid-Mesozoic times.http://www.zoobank.org/urn:lsid:zoobank.org:pub:53C1BDD0-C9A9-4E9D-8515-A57BE437581F