Early Cretaceous Yixian Formation Research Articles

A new fossil genus of Mesochrysopidae (Neuroptera) from the Early Cretaceous Yixian Formation of China

Longicellochrysa yixiana gen. et sp. nov. (Neuroptera: Mesochrysopidae) is described from the Mesozoic Yixian Formation (China). Allopteridae and Tachinymphidae of Nel et al. (2005) are considered subfamilies of Mesochrysopidae, along with Mesochrysopinae. Longicellochrysa gen. nov. displays a mixture of character states of Mesochrysopinae and Allopterinae and can not be assigned to any subfamily, indirectly supporting a family status of Mesochrysopidae sensu lato.

A New Boreopterid Pterodactyloid Pterosaur from the Early Cretaceous Yixian Formation of Liaoning Province, Northeastern China

Abstract:A new boreopterid pterosaur: Zhenyuanopterus longirostris gen. et sp. nov. from the Yixian Formation of western Liaoning is erected, based on the complete skeleton with a skull and lower jaws preserved. It is characterized by: a large boreopterid pterosaur with a high number of teeth, where the anterior teeth are much larger than posterior ones; the length of the dorsal + sacral vertebrae is nearly half the length of the skull; ratio of the length of the humerus to metacarpal IV is approximately 91% and the, humerus, femur and third wing phalanx are all equal in length and the feet are specially small. It represents the largest boroepterid pterosaur discovered from western Liaoning and its surrounding areas so far

A new early Cretaceous relative of Gnetales: Siphonospermum simplex gen. et sp. nov. from the Yixian formation of northeast China.

BackgroundKnowledge on fossil and evolutionary history of the Gnetales has expanded rapidly; Ephedra and ephedroids as well as the Gnetum-Welwitschia clade are now well documented in the Early Cretaceous. However, hypotheses on evolutionary relationships among living and fossil species are hampered by restricted knowledge of morphological variation in living groups and recent studies indicate that gnetalean diversity and character evolution may be more complex than previously assumed and involve additional extinct groups (Bennettitales, Erdtmanithecales and unassigned fossil taxa).ResultsHere we describe a new fossil related to Gnetales, Siphonospermum simplex from the Early Cretaceous Yixian Formation, an impression/compression of a reproductive shoot. The slender main axis bears one pair of opposite and linear leaves with primary parallel venation. The reproductive units are ovoid, without supporting bracts and borne on one median and two lateral branches. The most conspicuous feature of the fossil is the long, thread-like micropylar tube formed by the integument. Each ovule is surrounded by two different layers representing one or two seed envelopes; an inner sclerenchymatous layer and an outer probably parenchymatous layer.ConclusionsThe vegetative and reproductive features of Siphonospermum simplex exclude a relationship to any other group than the Gnetales. A combination of opposite phyllotaxis, linear leaves and ovules surrounded by seed envelope(s) and with a long exposed micropylar tube are known only for extant and extinct Gnetales. Siphonospermum simplex constitutes a new lineage within the Gnetales. Its morphology cannot be directly linked to any previously known plant, but the organization of the reproductive units indicates that it belongs to the Gnetum-Welwitschia clade. Based on the absence of cone bracts and the inferred histology of the seed envelope(s) it could be related to Gnetum, however, there are also affinities with the ephedran lineage, some of which are likely plesiomorphic features, others perhaps not. Phylogeny and character evolution in the Bennettitales, Erdtmanithecales and Gnetales are currently only partly understood and under debate; the exact systematic position of Siphonospermum simplex, i.e., its position within the Gnetales, cannot be resolved with certainty.

The first Praesiricidae (Hymenoptera) from Northeast China

A new subfamily Rudisiricinae Gao, Rasnitsyn, Ren & Shih, n. subfam. and a new genus Rudisiricius Gao, Rasnitsyn, Ren & Shih, n. gen. with three new species R. belli Gao, Rasnitsyn, Ren & Shih n. sp., R. crassinodus Gao, Rasnitsyn, Ren & Shih, n. sp., and R. celsus Gao, Rasnitsyn, Ren & Shih, n. sp. are described and illustrated from the family Praesiricidae. The type specimens were collected from the Late Jurassic to Early Cretaceous Yixian Formation, northeastern China. The new subfamily also includes Aulidontes Rasnitsyn from the Upper Jurassic of Karatau in Kazakhstan. This is the first record of Praesiricidae in China. These well-preserved nearly-complete new fossils reported here provide additional material and structure characters about this family, which helps filling some gap in the evolution of Lower Hymenoptera.

A Life Table for Psittacosaurus lujiatunensis: Initial Insights Into Ornithischian Dinosaur Population Biology

Very little is known about nonavian dinosaur population biology. Multi-individual sampling and longevity estimation using growth line counts can be used to construct life tables-the foundation for population analyses in ecology. Here we have determined the size and age distribution for a sample consisting of 80 individuals of the small ornithischian, Psittacosaurus lujiatunensis from the early Cretaceous Yixian Formation of China. Their ages ranged from less than a year to eleven years and the distribution was strongly right-skewed. This is consistent with taphonomic interpretations that these animals derive from a catastrophic death assemblage. The static life table analysis revealed the same general pattern of survivorship as tyrannosaurs including increased attrition before the attainment of full adult size. This may reflect increased physiological demands and/or predation exposure associated with reproduction. Collectively these findings suggest that most nonavian dinosaurs may have had a similar life history strategy.

A short-armed dromaeosaurid from the Jehol Group of China with implications for early dromaeosaurid evolution

Recent discoveries of basal dromaeosaurids from the Early Cretaceous Jiufotang and Yixian formations of Liaoning, China, add significant new information about the transition from non-avian dinosaurs to avians. Here we report on a new dromaeosaurid, Tianyuraptor ostromi gen. et sp. nov., from the Early Cretaceous Yixian Formation of western Liaoning, China, based on a nearly complete skeleton. Tianyuraptor possesses several features only seen in other Liaoning dromaeosaurids, although to a less developed degree, and it also exhibits features unknown in Laurasian dromaeosaurids but present in the Gondwanan dromaeosaurids and basal avialans, thus reducing the morphological gap between these groups. Tianyuraptor possesses a comparatively small furcula and proportionally short forelimbs. This lies in stark contrast to the possible capacity for flight in the microraptorines, which have proportionally long and robust forelimbs and large furculae. The presence of such striking differences between the Early Cretaceous Jehol dromaeosaurids reveals a great diversity in morphology, locomotion and ecology early in dromaeosaurid evolution.

Diversification in an Early Cretaceous avian genus: evidence from a new species of Confuciusornis from China

A new species of Confuciusornis, the oldest known beaked bird, is erected based on a nearly complete fossil from the Early Cretaceous Yixian Formation of western Liaoning, northeast China. C. feducciai is the largest and shows the highest ratio of the forelimb to the hindlimb among all known species of Confuciusornis. The skeletal qualitative autapomorphies, including a V-shaped furcula, a rectangular deltopectoral crest, the absence of an oval foramen at the proximal end of the humerus, the very slender alular digit, a relatively much longer ischium which is two-thirds the length of the pubis, and the morphology of sternum, strongly suggest the new specimen is a valid distinctive taxon. Detailed comparison with other described species provides sound evidence for diversification in the Early Cretaceous avian genus Confuciusornis. Anatomical features suggest an arboreal habit of the new bird.

Pristinochterus gen. n. (Hemiptera: Ochteridae) from the Upper Mesozoic of northeastern China

A new genus of velvety shore bugs, Pristinochterus gen. n., with one new species, Pristinochterus zhangi sp. n., are described. The specimens were collected from the Late Jurassic to Early Cretaceous Yixian Formation and Early Cretaceous Jiufo- tang Formation in northeastern China. This finding represents the first record of fossil velvety shore bugs from China. Among the specimens, four well-preserved nymphs are reported for the first time. The placement of the new genus within Ochteridae is briefly discussed. A key to the world genera of Ochteridae is provided.

A New Enantiornitine Bird with Four Long Rectrices from the Early Cretaceous of Northern Hebei, China

Abstract: Paraprotopteryx gracilis, a new enantiornithine bird from the Early Cretaceous Yixian Formation in Fengning, northern Hebei Province is erected, based on the following characters: Y‐shaped furcula with a long hypocleidum and a much narrow interclavicular angle, and the morphology of the sternum are different from other enantiornithines. Additionally, alular digit bearing the biggest manual claw extends distally to the distal end of the major metacarpal; the minor metacarpal is slender than the major metacarpal. Carpometacarpus only fused proximally; astragalus and calcaneum partially fused to one another but unfused to the tibia. This is the first record of Mesozoic birds in having four long rectrices, which may represent morphologically a secondary sexual character, an intermediate stage from elongated scale to branched feather, and possess functional advantage in supplementing the lifting surface to compensate the unskilled flight.

New Material of Sinosauropteryx (Theropoda: Compsognathidae) from Western Liaoning, China

Abstract: An incomplete specimen of Sinosauropteryx prima collected from the Early Cretaceous Yixian Formation of the Dawangzhangzi area in Lingyuan, western Liaoning is depicted. It represents the first systematically described material of this feathered compsognathid outside the Sihetun area in Beipiao. This specimen shows some diagnostic features of Sinosauropteryx prima, such as the very short forelimb in relation to hindlimb with the length ratio of humerus plus radius to femur plus tibia just around 30%, and the long and massive first manual ungual subequal in length to radius. The presence of Sinosauropteryx prima only at Sihetun and Dawangzhangzi supports the suggestion that the fossil‐bearing beds in the Sihetun and Dawangzhangzi areas are equivalent to each other within the Yixian Formation.

Juvenile Birds from the Early Cretaceous of China: Implications for Enantiornithine Ontogeny

Mesozoic remains of embryonic and early juvenile birds are rare. To date, a handful of in ovo embryos and early juveniles of enantiornithines from the Early Cretaceous of China and Spain and the Late Cretaceous of Mongolia and Argentina have comprised the entire published record of perinatal ontogenetic stages of Mesozoic birds. We report on the skeletal morphology of three nearly complete early juvenile avians from the renowned Early Cretaceous Yixian Formation of Liaoning Province in northeastern China. Evidence of the immaturity of these specimens is expressed in the intense grooving and pitting of the periosteal surfaces, the disproportionately small size of the sterna, and the relative size of the skull and orbits. Size notwithstanding, anatomical differences between these three specimens are minimal, leaving no basis for discriminating them into separate taxa. Numerous osteological synapomorphies indicate that they are euenantiornithine birds, the most diverse clade of Enantiornithes, but their identification as members of a particular euenantiornithine taxon remains unclear. Their early ontogenetic stage, however, provides important information about the postnatal development of this specious clade of Cretaceous birds. The presence of pennaceous wing feathers suggests that fledging occurred very early in ontogeny, thus supporting a precocial or highly precocial strategy for enantiornithine hatchlings. The morphology of these new early-stage juveniles is also significant in that they allow a better understanding of the homologies of several avian compound bones because the components of these skeletal compounds are preserved prior to their coossification. The general morphology of the wrist and ankle of these juveniles highlights once again the striking similarity between nonavian theropods and early birds.

Liaoxia Cao et S.Q. Wu (Gnetales): ephedroids from the Early Cretaceous Yixian Formation in Liaoning, northeastern China

Gnetalean compression-impression fossils are described from the Early Cretaceous Yixian Formation, Liaoning Province, north-eastern China, and assigned to six species of Liaoxia Cao et S.Q. Wu. The fossils have opposite-decussate phyllotaxis and cones comprising 2–12 pairs of bracts. Ovulate cones have seeds typically in a distal position. The species differ from each other and from previously described fossils in the absence or presence of leaves, shape of cones and seeds, and shape and position of cone bracts. The species of Liaoxia are probably close relatives of extant species of Ephedra L., but diagnostic reproductive details that could confirm this hypothesis are not preserved. The restricted information in the fossils and the poorly understood morphological diversity of extant Ephedra, prevent assignment of the fossils to any particular subgroup of Ephedra, as well as an explicit exclusion of them from the extant genus.

Geochemistry of high-Mg andesites from the early Cretaceous Yixian Formation, western Liaoning: Implications for lower crustal delamination and Sr/Y variations

85 volcanic rocks of the Yixian Formation from the Sihetun type section were collected and analyzed for geochemical and isotopic compositions. Major element compositions indicate that the Sihetun volcanic rocks are high magnesium andesites with some basalts occurring at the bottom of section. The Sihetun high magnesium andesites (SiO 2 = 52.82―59.31wt%, Al 2 O 3 = 14.15―16.35wt%) show many characteristics of adakites such as depletion in heavy rare-earth elements (HREE; Yb = 1.03―1.88 μg/g) and Y(12―20 mg/g) and high Sr (620―1323 μg/g) and Sr/Y(32―88), with high La N /Yb N ratio (10―25). They share similar major and trace element characteristics to volcanic rocks from the Xinglonggou Formation except their lower Nd isotope ratios ( 143 Nd/ 144 Nd (130Ma) = 0.5118―0.5119, e Nd (130 Ma) = -11.6―-13.8, 87 Sr/ 86 Sr (130 Ma) = 0.7058―0.7064. They were interpreted in a way that eclogite that formed at the base of thickened Archean lower crust of the North China craton foundered into the convecting mantle and subsequently melted and interacted with peridotite. However, compared to the Xinglonggou volcanic rocks, the source of the Sihetun magma contained more ancient continental crustal material in order to explain its evolved Nd isotopes. The age of the Sihetun Formation was 120 to 130 Ma, and this indicates that delamination lasted to the early Cretaceous period. The Sr contents and Sr/Y ratios of the Sihetun high-Mg andesites show significant negative correlations with SiO 2 for samples with SiO 2 > 56%. These suggest that the Sr and Sr/Y values were reduced due to fractional crystallization of plagioclase. Accordingly, the effect of crystallization on volcanic Sr and Sr/Y ratio has to be taken into account.

New fossil ommatid (Coleoptera: Archostemata: Ommatidae) from Jehol Biota of Western Liaoning, China*

Abstract In this paper one new genus and one new species of fossil ommatid, Odontomma trachylaena gen. et sp. nov., is described and illustrated from the Late Jurassic or Early Cretaceous Yixian Formation of western Liaoning, China. Based on wide epipleural space of elytron with several rows of cells, the new taxa is attributed to tribe Brochocoleini of Ommatidae and compared with genus Brochocoleus. Due to the fact that most other Chinese Mesozoic ommatids are not complete, the complete preservation of the new specimens reported here enabled us to determine the characteristics of the body of these ancient ommatid. Moreover, based on the well-preserved individual of this new genus, we may suppose the affinities of the new species with extant and extinct groups. Supported by National Natural Science Foundation of China (Grant Nos.30025006, 30370184, 30430100, 30200025), the Beijing Natural Science Foundation. (Grant No. 5032003), Beijing Municipal Commission of Education (Grant No. KZ200410028013) and RCQJ...

A new species of Psittacosaurus (Dinosauria: Ceratopsia) from the Early Cretaceous Yixian Formation, Liaoning, China

Newly discovered, well-preserved skulls and mandibles from the lowest part of the Early Cretaceous Yixian Formation, western Liaoning Province, China, document the earliest known record of psittacosaurs and provide the basis for recognition of a new species, Psittacosaurus lujiatunensis. This discovery increases the taxonomic diversity of psittacosaurs to eight valid species and extends the stratigraphic range of the family Psittacosauridae from late Barremian-Albian to Hauterivian. Comparative study of the new species with other well-known psittacosaurs indicates that the new taxon is probably the most basal member of the psittacosaur clade now known. This interpretation is in agreement with the temporal distribution of the clade and supports the hypothesis that the Psittacosauridae originated from the basal ceratopsian stem no later than the earliest part of the Cretaceous.

Early Cretaceous sarraceniacean-like pitcher plants from China

This paper reports fossil plants of Archaeamphora longicervia gen. et sp. nov. Li from the Early Cretaceous Yixian Formation, northeastern China. The plants are herbaceous and similar to modern sarraceniaceans in having spirally arranged developed/underdeveloped pitchers and phyllodia-like leaves that have parallel major veins and reticulate meshes, distinctive honey-spoon-like structures and porous glands. The intimately associated seeds are reticulate-tuberculate and winged, resembling sarraceniacean seeds. The unique pitcher and characteristic seed suggest a relationship to Sarraceniaceae. The relationship to Angiosperms is also supported with fossil molecule oleanane found from Archaeamphora, using GC-MS. Archaeamphora demonstrates the earliest carnivorous plant and the only fossil record of pitcher plants. Also, as the third genus of the oldest Angiosperms, the existence of such a derived taxon suggests that flowering plants should have originated much earlier.

A new early cretaceous lizard with well-preserved scale impressions from western liaoning, China

A new small lizard, LiaoningoZacerLa brevirosLra gen. et sp. nov., from the Early Cretaceous Yixian Formation of western Liaoning is described in detail. The new specimen was preserved not only by the skeleton, but also by the exceptionally clear scale impressions. This lizard can be included within the taxon Scleroglossa based on its 26 or more presacrals, cruciform interclavicle with a large anterior process, moderately elongated pubis, and slightly notched distal end of tibia. The scales vary evidently in size and shape at different parts of body: small and rhomboid ventral scales, tiny and round limb scales, and large and longitudinally rectangular caudal scales that constitute the caudal whorls. This new finding provides us with more information on the lepidosis of the Mesozoic lizards.

A new troodontid dinosaur from China with avian-like sleeping posture.

Discovering evidence of behaviour in fossilized vertebrates is rare. Even rarer is evidence of behaviour in non-avialan dinosaurs that directly relates to stereotypical behaviour seen in extant birds (avians) and not previously predicted in non-avialan dinosaurs. Here we report the discovery of a new troodontid taxon from the Early Cretaceous Yixian Formation of western Liaoning, China. Numerous other three-dimensionally preserved vertebrate fossils have been recovered recently at this locality, including some specimens preserving behavioural information. The new troodontid preserves several features that have been implicated in avialan origins. Notably, the specimen is preserved in the stereotypical sleeping or resting posture found in extant Aves. Evidence of this behaviour outside of the crown group Aves further demonstrates that many bird features occurred early in dinosaurian evolution.

Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids.

Tyrannosauroids are one of the last and the most successful large-bodied predatory dinosaur groups, but their early history remains poorly understood. Here we report a new basal tyrannosauroid from the Early Cretaceous Yixian Formation of western Liaoning, China, which is small and gracile and has relatively long arms with three-fingered hands. The new taxon is the earliest known unquestionable tyrannosauroid found so far. It shows a mosaic of characters, including a derived cranial structure resembling that of derived tyrannosauroids and a primitive postcranial skeleton similar to basal coelurosaurians. One of the specimens also preserves a filamentous integumentary covering similar to that of other coelurosaurian theropods from western Liaoning. This provides the first direct fossil evidence that tyrannosauroids had protofeathers.

A new frog (Amphibia: Anura) from the Lower Cretaceous of western Liaoning, China

Based on a nearly complete skeleton, an archaic frog is described from the Early Cretaceous Yixian Formation near Yixian, western Liaoning Province, China. The new frog shows several peculiar morphologies including the presence of a co-ossified parahyoid bone with a V-shaped configuration. Such a parahyoid was previously known only for the problematic taxon Neusibatrachus from the Lower Cretaceous of Spain. A phylogenetic analysis was performed with the inclusion of the new taxon and Neusibatrachus. This analysis suggests that the new taxon is a primitive archaeobatrachian closely related to Notobatrachus and Vieraella, while Neusibatrachus is placed as a basal member of the Pipoidea. The suggested relationships of the new frog with South American forms reveal a biogeographic enigma that cannot be resolved until there is more fossil evidence and current phylogenetic hypotheses are further evaluated.