Arid and cool climate transition during the evolution of the Jehol Biota and its implications

New ephialtitid wasps (Hymenoptera) of the Early Cretaceous Jehol Biota from NE China

The Early Cretaceous Jehol Biota yielded exceptionally diverse and abundant insect fossils, yet its cicadomorphan record remains incompletely documented. Here, we describe new cicadomorphan specimens from the Lower Cretaceous Yixian Formation of Huangbanjigou, Beipiao City, northeastern China. The material includes Stellularis longirostris and Sinocercopis sp. (Procercopidae), a new species, Cretohylicella lambkini sp. nov., tentatively assigned to Hylicellidae, and a new specimen tentatively assigned to Cicadelloidea. This study enriches the cicadomorphan diversity of the Yixian Formation and provides new insights into the phytophagous insect assemblage of the Jehol Biota.

Cupedidae is the most species-rich family within the extinct beetle suborder Archostemata, noted for its abundance, diversity, and broad geographic distribution in the Mesozoic. Although archostematans are relatively common in the Jehol Biota of northeastern China, most records to date have been recovered from the Yixian Formation. In this study, we report a new cupedid beetle fossil from the Jiufotang Formation. The new species, Apriacma acoronata sp. nov., is characterized by an elongate body; long antennae with the pedicel distinctly shorter than the other antennomeres; large, flattened mandibles; a subrectangular prothorax slightly wider than the head, with gently curved lateral margins and lacking anterior corners; and distinctly stout profemora. This discovery constitutes the first record of Archostemata from the Jiufotang Formation, extending the stratigraphic and geographic distribution of cupedid beetles within the Jehol Biota, and contributes to our understanding of archostematan persistence and diversity in Early Cretaceous lacustrine ecosystems.

The first occurrence of the extinct cicadomorphan family Palaeontinidae from the Jiufotang Formation of China is reported based on a specimen assigned to Ilerdocossus cf. fengningensis. The genus Ilerdocossus Gomez Pallerola, 1984 is well known from the underlying Yixian Formation of northern China (Hebei, Liaoning provinces, and Inner Mongolia), as well as the Caliza con Caraceas Formation of Lerida, Spain and the Lower Weald Clay (Surrey, England), UK. The new record represents the stratigraphically youngest occurrence of the family in the Jehol Biota and extends the temporal range of Ilerdocossus into the Aptian (121–113 million years ago).

A 120-million-year-old fungal parasite from the Cretaceous Jehol Biota.

High-precision geochronology of the Early Cretaceous Jiufotang Formation: Temporal constraints on the late phase of the Jehol Biota

Morphology of the forelimb of <i>Confuciusornis</i> and its implications for early flight evolution

A combination of sectioning and microscopy techniques, along with the application of finite-difference-time-domain modeling on a fossil feather, results in the novel estimation of the range of iridescent colors from the fossilized melanosome type and organization preserved in the elongate head crest feathers of a new Cretaceous enantiornithine bird. The densely packed rod-like melanosomes are estimated to have yielded from red to deep blue iridescent coloration of the head feathers. The shape and density of these melanosomes also may have further increased the feather’s structural strength. This occurrence on a likely male individual is highly suggestive of both a signaling function of the iridescent crest and a potential behavioral role in adjusting the angle of light incidence to control the display of this iridescent structural coloration.

A combination of sectioning and microscopy techniques, along with the application of finite-difference-time-domain modeling on a fossil feather, results in the novel estimation of the range of iridescent colors from the fossilized melanosome type and organization preserved in the elongate head crest feathers of a new Cretaceous enantiornithine bird. The densely packed rod-like melanosomes are estimated to have yielded from red to deep blue iridescent coloration of the head feathers. The shape and density of these melanosomes also may have further increased the feather’s structural strength. This occurrence on a likely male individual is highly suggestive of both a signaling function of the iridescent crest and a potential behavioral role in adjusting the angle of light incidence to control the display of this iridescent structural coloration.

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

ABSTRACT New Ornithothoraces fossil material was recovered during a systematic survey of fossil and geological heritage resources from the Lower Cretaceous Yixian Formation of Chedaogou locality, Weichang County, Hebei Province, northeastern China. The specimen preserves several dorsal vertebrae and an articulated pelvic girdle. Detailed morphological analysis reveals a specimen with the following significant anatomical features: the synsacrum is composed of 8–9 fused vertebrae; the pelvic girdle is well fused with a developed antitrochanter; the ilium is relatively broad, with the postacetabular region significantly shorter than the pre-acetabular region; the ischium is broad and shallowly arcuate, slightly bending ventrally and lacking a distinct dorsal process in the middle and with a non-pointed distal margin; and the pubis is slender and cylindrical, with a relatively uniform diameter, lacking a pubic boot and with unfused distal ends. These features probably indicate a new ornithuromorph species. This discovery enriches our understanding of avian diversity in Jehol Biota, providing an important specimen for studying the evolution of the pelvic girdle in Mesozoic birds. Additionally, the result of this geological survey shows the Yixian Formation disconformity with the underlying Zhangjiakou Formation at Chedaogou locality, suggesting a discontinuous deposition in the research area.

Tritylodontids are close relatives of mammals with specialized teeth adapted for herbivory. Despite their diversification during the Jurassic, the fossil record of this clade suggests they declined significantly in the Cretaceous when they are mainly represented by fragmentary dental remains. The exception is the Early Cretaceous taxon Fossiomanus sinensis Mao et al., 2021. Here we describe a new mandible of this species from the same locality as the holotype specimen. The new specimen provides more complete information on mandible shape and tooth morphology, filling a knowledge gap for this iconic Cretaceous tritylodontid, given that cranial morphology in the holotype of F. sinensis remains insufficiently studied. Additionally, the fossil record of F. sinensis represents the youngest known tritylodontid (~119 Ma, Aptian) and the latest non-mammaliaform cynodont, shedding light on the evolutionary history of early mammalian relatives.

Liaoningotitan sinensis is one of three sauropod species found in the Jehol Biota. Liaoningotitan sinensis is from the Lower Cretaceous Yixian Formation in Liaoning, China. The discovery of Liaoningotitan sinensis was an important breakthrough for researching the diversity of giant herbivorous animals in the Jehol Biota. However, the research and analysis of Liaoningotitan sinensis are not yet complete. This study presents a comprehensive research and analysis of Liaoningotitan sinensis holotype. First, the skull, vertebrae, pelvic girdle, and appendicular elements of Liaoningotitan sinensis holotype were carefully reexamined, leading to the discovery of mosaic evolution occurring in the skull and the identification of one new autapomorphy of humerus of Liaoningotitan sinensis: the attachment point of coracobrachialis muscle on the anterior surface of the proximal end of the humerus is flat. Second, the characteristics of the Liaoningotitan sinensis holotype and other well-preserved sauropod dinosaurs were used to reconstruct the skull of Liaoningotitan sinensis. Next, Euhelopus zdanskyi was used to reconstruct the body type of Liaoningotitan sinensis holotype, the result indicating that Liaoningotitan sinensis was approximately 10 m in length. Finally, TNT software was utilized to analyze the phylogenetic position of Liaoningotitan sinensis, with the result indicating that Liaoningotitan sinensis can be classified into the Euhelopodidae.

New palynological data and U–Pb dating from the Jiufotang Formation: Implications for the late Jehol Biota

ABSTRACT The Hemeroscopidae Pritykina 1977 is a dragonfly family widely distributed in the Lower Cretaceous terrestrial strata of East Asia and Transbaikalia. However, the diversity is relatively low with only three genera and species previously recorded. In the present study, a new hemeroscopid dragonfly, Abrohemeroscopus yuanjiawaensis sp. nov. is described from the Lower Cretaceous Jiufotang Formation (yields the late Jehol Biota) of Chaoyang City, western Liaoning, northeastern China. Abrohemeroscopus yuanjiawaensissp. nov. differs from the type species (Abrohemeroscopus mengi Ren, Liu & Cheng 2003) in the pterostigma covering four cells, the oblique vein ‘O’ being four and a half cells distal of base of RP2 and the anal loop subdivided into nine cells. This discovery indicates that the genus Abrohemeroscopus Ren, Liu & Cheng 2003 is a typical dragonfly genus of the late Jehol entomofauna in western Liaoning.

ABSTRACTThe Compsognathidae was originally considered an early-diverging clade of coelurosaur theropods. However, recent study suggests that Compsognathidae is not monophyletic. Here, we describe two new compsognathid-like species, Sinosauropteryx lingyuanensis sp. nov. and Huadanosaurus sinensis gen. et sp. nov. from the Lower Cretaceous Yixian Formation of Dawangzhangzi (Lingyuan, Western Liaoning, China). The phylogenetic results indicate that all compsognathid-like theropods from the Early Cretaceous Jehol Biota form a monophyletic group Sinosauropterygidae nested among early-diverging coelurosaurs. Morphological comparison between various species of sinosauropterygids from the Early Cretaceous of Northeast China, combined with the phylogenetic results, suggests that at least three distinct hunting strategies were present among coeval species. The diversification of theropods should be attributed to the landscape caused by the destruction of the North China craton.

Here, two dinosaur teeth are discovered from the Lower Cretaceous Jiufotang Formation in Longcheng, Chaoyang, western Liaoning, China. This discovery marks a new fossil site for the Jehol Biota, characterized by three-dimensionally preserved fossils. Based on comprehensive morphological comparisons, the teeth can be assigned to Theropoda and early-diverging Titanosauriformes. The theropod tooth, with a preserved length of 47.8 mm, represents a distinct taxon separate from Sinotyrannus, which is the only known large theropod dinosaur from the Jiufotang Formation. The titanosauriform tooth represents the youngest sauropod record within the Jehol Biota. These findings contribute to an increased dinosaur diversity within the Jiufotang Formation from ten taxa to 12.

The Early Cretaceous pterosaur Sinopterus atavismus, from Northeast China, belongs to the Tapejaridae. The furrowed structure of its wing phalanges is relatively primitive, possibly indicative of atavism. New information of Sinopterus atavismus is therefore of great interest in studies of evolution among Tapejaridae, especially for interpreting some anatomical features of the holotype. In this paper, the distribution patterns and characteristics of chemical elements in the holotype specimen were analyzed by non-destructive micro-X-ray fluorescence (micro-XRF). The chemical mapping results show that the element Ca was significantly associated with pterosaur bones, showing residual traces of the left lower part of the humerus; Sr replaced Ca and the distribution was uniform, suggesting that phosphate recrystallization occurred in the specimen; Fe is concentrated in the soft tissue parts of the pterosaur fossil, which may be related to pyritization, and Mn appears as the alteration phase of the original iron-rich phase. The elemental migration and sedimentary environment of the fossil require further study. The XRF elemental imaging study of Sinopterus atavismus is helpful for explorations of the development and evolution of Tapejaridae, and also provides more chemical information on the taphonomy of the Jehol Biota.

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.