The fossils of the Cretaceous Jehol Biota exhibit excellent preservation and extraordinary diversity. Terrestrial fossils, including plants, insects, dinosaurs, birds, mammals and freshwater ...invertebrates have been discovered from the Dabeigou, Yixian and Jiufotang Formations (and correlative strata) in Central and East Asia. Significant specimens have been recovered from the Yixian Formation of Inner Mongolia, Hebei Province, western Liaoning Province of NE China. The Yixian Formation is generally divided (from bottom to top) into the Lujiatun Unit, Lower Lava Unit, Jianshangou Unit, Upper Lava Unit, Dawangzhangzi Unit and Jingangshan Unit. However, previously reported age data obtained through a range of methods and applied to different units of the Yixian Formation do not consistently integrate with the Yixian's commonly accepted stratigraphic interpretation. Here we summarize previous age data for the Yixian Formation and recalibrate previously reported 40Ar/39Ar ages by using new age interpretations for the same standard (i.e. FCs=28.294). We also present new high-precision 40Ar/39Ar ages of 125.8±1.0Ma and 126.0±0.8Ma for two basaltic samples from the Lujiatun Unit, a unit of previously uncertain age. The new age data and re-calibrated published data indicate that the Lujiatun Unit was deposited contemporaneously with the Jianshangou Unit. The widely accepted stratigraphic column for the Yixian Formation therefore requires reinterpretation. Our study provides significant clues for reconstructing sedimentary environment for the fossil-rich Yixian deposits and allows to constrain evolutionary rates for early mammals, primitive birds and feathered dinosaurs.
•We report robust 40Ar/39Ar age for samples from a dinosaur-rich outcrop.•The stratigraphic correlation for the Yixian Formation is wrong.•Our data allow reconstructing stratigraphic column around the classic Jehol outcrops.•Our study allows constraining evolutionary rates for Jehol animals.
Basal Ornithuromorpha, until recently, was one of the most poorly documented segments of early avian evolution. The known species diversity of the ornithuromorph clade has increased rapidly with the ...addition of new discoveries from the Early Cretaceous deposits of northeastern China. Reported in this paper is the discovery of a new bird from the Lower Cretaceous Yixian Formation, Liaoning Province, China. The specimen represents a new species, Longicrusavis houi, but bears similarities to Hongshanornis longicresta from the same formation of Inner Mongolia. The two birds are comparable in size and share an unusual sigmoid mandible and elongate hindlimbs relative to their forelimbs. Together these taxa represent a clade (Hongshanornithidae, new taxon) of specialized 'shorebirds' whose elongate hindlimbs indicate ecological adaptations different from those of other Jehol ornithuromorphs. Phylogenetic relationships of Mesozoic birds are discussed based on the results of a comprehensive cladistic analysis. New morphological information on Ornithuromorpha is provided through the detailed description of the new taxon together with new information on Hongshanornis.
gliding lizard from the Early Cretaceous of China Li, Pi-Peng; Gao, Ke-Qin; Hou, Lian-Hai ...
Proceedings of the National Academy of Sciences - PNAS,
03/2007, Volume:
104, Issue:
13
Journal Article
Peer reviewed
Open access
Gliding is an energetically efficient mode of locomotion that has evolved independently, and in different ways, in several tetrapod groups. Here, we report on an acrodontan lizard from the Early ...Cretaceous Jehol Group of China showing an array of morphological traits associated with gliding. It represents the only known occurrence of this specialization in a fossil lizard and provides evidence of an Early Cretaceous ecological diversification into an aerial niche by crown-group squamates. The lizard has a dorsal-rib-supported patagium, a structure independently evolved in the Late Triassic basal lepidosauromorph kuehneosaurs and the extant agamid lizard Draco, revealing a surprising case of convergent evolution among lepidosauromorphans. A patagial character combination of much longer bilaterally than anteroposteriorly, significantly thicker along the leading edge than along the trailing edge, tapered laterally to form a wing tip, and secondarily supported by an array of linear collagen fibers is not common in gliders and enriches our knowledge of gliding adaptations among tetrapods.
Hynobiids are a group of small- to moderate-sized salamanders living primarily in Asia. They are a primitive crown-group clade, with a poor fossil record. Several hynobiid-like taxa have been ...discovered from the Lower Cretaceous strata of northern China during the last 20 years, with Liaoxitriton zhongjiani and Nuominerpeton aquilonaris identified as the oldest known stem hynobiids. However, the record of pre-Cretaceous hynobiid-like taxa is only known by Liaoxitriton daohugouensis, of which both the morphology and the congeneric status with L. zhongjiani remain problematic. Here, we report on a new hynobiid-like salamander, Linglongtriton daxishanensis, gen. et sp. nov., on the basis of two specimens from the Upper Jurassic Lanqi/Tiaojishan Formation (∼160 Ma) of Liaoning Province, China. Linglongtriton is diagnosed by a unique combination of features revealed by both observation under microscope and micro-computed tomography (µCT) scan of the holotype, including nasals separated from each other at the midline; prootic, opisthotic, and exoccipital retained as discrete elements; dentary with a lateral groove; articular not ossified; metacarpal III enlarged; a single centrale; and distal tarsals 4 and 5 fused into a single element. Phylogenetic analysis identified Linglongtriton and several other hynobiid-like taxa, including Liaoxitriton daohugouensis, as stem hynobiids, thereby extending the temporal range of the stem by at least 40 Ma—from the Early Cretaceous (Aptian–Barremian) to the Middle Jurassic (Bathonian). Comparative study of Linglongtriton with living and fossil hynobiids sheds new lights on the evolution and developmental mechanisms of several characters, including nasal separation and tarsal elements.
Although the long‐necked choristodere Hyphalosaurus is the most abundant tetrapod fossil in the renowned Yixian Formation fossil beds of Liaoning Province, China, the genus has only been briefly ...described from largely unprepared specimens. This paper provides a thorough osteological description of the type species Hyphalosaurus lingyuanensis and the con‐generic species Hyphalosaurus baitaigouensis based on the study of fossils from several research institutions in China. The diagnoses for these two species are revised based on comparison of a large sample of specimens from the type area and horizon of each of the two species. The skull, better known in H. baitaigouensis, exhibits key choristodere synapomorphies including an elongate contact between the prefrontals and posteriorly expanded supratemporal fenestrae that strongly support the placement of the highly derived hyphalosaurids within Choristodera. Both species of Hyphalosaurus share a proportionally small head, an elongate neck, a relatively unspecialized appendicular skeleton and a long, dorsoventrally heightened tail. Soft tissue preservation in several specimens provides rare insight into the integument of an extinct group. The integument of Hyphalosaurus is made up of small polygonal scales with several parasagittal rows of large, keeled, ovoid scutes. These possibly ornamental scutes bear a strong resemblance to the rows of large scutes in the monjurosuchid choristodere Monjurosuchus splendens. Observations from a variety of growth stages reveal that significant ontogenetic change in the proportions of the body and limb bones occurred in both species of Hyphalosaurus.
Flawed Analysis? A Response to Myhrvold Erickson, Gregory M.; Makovicky, Peter J.; Inouye, Brian D. ...
Anatomical record (Hoboken, N.J. : 2007),
October 2015, 2015-Oct, 2015-10-00, 20151001, Volume:
298, Issue:
10
Journal Article
With ten extant families, salamanders (urodeles) are one of the three major groups of modern amphibians (lissamphibians). Extant salamanders are often used as a model system to assess fundamental ...issues of developmental, morphological and biogeographical evolution. Unfortunately, our understanding of these issues has been hampered by the paucity of fossil evidence available to assess the early history of the group. Here we report the discovery of an extraordinary sample of salamander fossils, some with rare soft-tissue impressions, from the Upper Jurassic of China. With over 500 articulated specimens, this assemblage documents the morphological diversity of early urodeles and includes larvae and adults of both neotenic and metamorphosed taxa. Phylogenetic analysis confirms that these salamanders are primitive, and reveals that all basal salamander clades have Asian distributions. This is compelling evidence for an Asian origin of Recent salamanders, as well as for an extensive and early radiation of several major lineages. These discoveries show that the evolution of salamanders has involved phylogenetic and ecological diversification around a body plan that has remained fundamentally stable for over 150 million years.
DNA hypomethylation plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). Here we investigated whether 3-hydroxy butyrate dehydrogenase 2 (BDH2), a modulator of ...intracellular iron homeostasis, was involved in regulating DNA hypomethylation and hyper-hydroxymethylation in lupus CD4+ T cells. Our results showed that BDH2 expression was decreased, intracellular iron was increased, global DNA hydroxymethylation level was elevated, while methylation level was reduced in lupus CD4+ T cells compared with healthy controls. The decreased BDH2 contributed to DNA hyper-hydroxymethylation and hypomethylation via increasing intracellular iron in CD4+ T cells, which led to overexpression of immune related genes. Moreover, we showed that BDH2 was the target gene of miR-21. miR-21 promoted DNA demethylation in CD4+ T cells through inhibiting BDH2 expression. Our data demonstrated that the dysregulation of iron homeostasis in CD4+ T cells induced by BDH2 deficiency contributes to DNA demethylation and self-reactive T cells in SLE.
Choristoderes are a group of extinct diapsid reptiles that once occupied the freshwater systems in the Northern Hemisphere from the Middle Jurassic through the Miocene. The Early Cretaceous ...monjurosuchid Philydrosaurus from western Liaoning, China, represents a transitional morphotype between a broad-snouted (crocodile-like) and a narrow-snouted (gavial-like) skull during the evolution of Choristodera. New specimens of the taxon from the Early Cretaceous Jiufotang Formation include an incomplete braincase and a nearly complete juvenile skeleton; the study of these specimens provides new information on the braincase and ontogenetic change of the skeleton of this transitional monjurosuchid. In the braincase floor, the foramen internus canalis caroticus externus opens in a groove lateral to the constricted lateral aspect of the parasphenoid, and ventral exposure of this foramen differs from Champsosaurus, in which parasphenoid/pterygoid fusion completely encloses the canal. On the occiput, the vagus nerve foramen penetrates the basioccipital, while the two foramina for the hypoglossal nerve open at the exoccipital/basioccipital suture. Comparative study of the new juvenile specimen with adult Philydrosaurus reveals previously unknown developmental changes of the cranial and postcranial skeleton of this monjurosuchid. Ontogenetically, Philydrosaurus underwent a dramatic change of skull proportions, including elongation of the antorbital and postorbital regions, and elongation of the jaws, with a great increase of the number of marginal teeth. The lower temporal fenestra is entirely closed in early ontogeny, as in large, fully-grown adults.
•We present detailed anatomic description of Philydrosaurus as a key component of the Jehol Biota.•We examine and discuss ontogenetic changes of the taxon.•New information increases knowledge on braincase of the fossil taxon.•Philydrosaurus underwent a dramatic change of skull proportions ontogenetically.•Supratemporal trough and closed infratemporal fenestra are known in both juvenile and adults.
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