Four new specimens of Anchiornis huxleyi (PKUP V1068, BMNHC PH804, BMNHC PH822, and BMNHC PH823) were recently recovered from the Late Jurassic fossil beds of the Tiaojishan Formation in northeastern ...China. These new specimens are almost completely preserved with cranial and postcranial skeletons. Morphological features of Anchiornis huxleyi have implications for paravian character evolution and provide insights into the relationships of major paravian lineages. Anchiornis huxleyi shares derived features with avialans, such as a straight nasal process of the premaxilla and the absence of an external mandibular fenestra in lateral view. However, Anchiornis huxleyi lacks several derived deinonychosaurian features, including a laterally exposed splenial and a specialized raptorial pedal digit II. Morphological comparisons strongly suggest Anchiornis is more closely related to avialans than to deinonychosaurians or troodontids. Anchiornis huxleyi exhibits many conservative paravian features, and closely resembles Archaeopteryx and other Jurassic paravians from Jianchang County, such as Xiaotingia and Eosinopteryx. The other Jianchang paravian, Aurornis xui, is likely a junior synonym of Anchiornis huxleyi.
Non-avian theropod dinosaurs with preserved integumentary coverings are becoming more common; but apart from the multiple specimens of Caudipteryx, which have true feathers, animals that are ...reasonably complete and entirely articulated that show these structures in relation to the body have not been reported. Here we report on an enigmatic small theropod dinosaur that is covered with filamentous feather-like structures over its entire body.
Flexible, or soft-shelled, eggs are almost unknown in the fossil record, leaving large gaps in our knowledge of the reproductive biology of many tetrapod clades. Here, we report two flexible-shelled ...eggs of the hyphalosaurid choristodere Hyphalosaurus baitaigouensis from the Early Cretaceous of China, one containing an embryo and the second associated with a neonate. Choristoderes are an enigmatic group of aquatic reptiles that survived the K–T extinction but died out in the Miocene. Hyphalosaurids, a specialized clade of Choristodera, resemble miniature plesiosaurs and are considered to be primarily aquatic in habit. Scanning electron microscopy of samples from the eggs reveals a thin, non-columnar external mineralized layer characterized by rounded nodes and tentatively identified poorly structured irregular pores, with an underlying amorphous layer presumably representing decomposed protein fibrils. While the relationships of Choristodera remain controversial, eggshell microstructure more closely resembles that of Lepidosauromorpha (the lineage including lizards) as opposed to that of Archosauromorpha (the lineage including birds and crocodiles).
Flying fishes are extraordinary aquatic vertebrates capable of gliding great distances over water by exploiting their enlarged pectoral fins and asymmetrical caudal fin. Some 50 species of extant ...flying fishes are classified in the Exocoetidae (Neopterygii: Teleostei), which have a fossil record no older than the Eocene. The Thoracopteridae is the only pre-Cenozoic group of non-teleosts that shows an array of features associated with the capability of over-water gliding. Until recently, however, the fossil record of the Thoracopteridae has been limited to the Upper Triassic of Austria and Italy. Here, we report the discovery of exceptionally well-preserved fossils of a new thoracopterid flying fish from the Middle Triassic of China, which represents the earliest evidence of an over-water gliding strategy in vertebrates. The results of a phylogenetic analysis resolve the Thoracopteridae as a stem-group of the Neopterygii that is more crown-ward than the Peltopleuriformes, yet more basal than the Luganoiiformes. As the first record of the Thoracopteride in Asia, this new discovery extends the geographical distribution of this group from the western to eastern rim of the Palaeotethys Ocean, providing new evidence to support the Triassic biological exchanges between Europe and southern China. Additionally, the Middle Triassic date of the new thoracopterid supports the hypothesis that the re-establishment of marine ecosystems after end-Permian mass extinction is more rapid than previously thought.
Early limb skeletogenesis in salamanders is characterized by preaxial elements, digits I and II forming earlier than their postaxial counterparts (digits III to V), a phenomenon known as preaxial ...dominance, whereas in amniotes and anurans, these developmental sequences are reversed. This pattern characterizes the late skeletogenesis of digits and zeugopodium of anamniote tetrapods but remains unknown in carpals/tarsals. To correct this gap in knowledge, we investigate the ossification patterns of the carpals/tarsals in six salamander families/clades based on micro-computed tomography scans. We found that preaxial dominance is seen in the distal carpals/tarsals of several salamander clades and diverse early tetrapods, such as temnospondyls and amniotes. This distribution suggests that preaxial dominance is a primitive developmental pattern in tetrapods. Our results demonstrate that the distal carpals/tarsals are developmentally and evolutionarily independent in the autopodium, and preaxial dominance facilitates stabilization of the number of distal carpals/tarsals during fin-to-limb transition and digit reduction in early tetrapods.
The ray-finned fish Plesiofuro mingshuica from the Triassic non-marine deposits of northern Gansu Province, China, was previously misidentified as a caturid halecomorph. This erroneous taxonomic ...assignment contributed to the misinterpretation of the age of the Plesiofuro-bearing fossil beds as Early Jurassic. Here, we provide a taxonomic revision of this problematic taxon based on a comparative study including over 500 new specimens. The revised description of Plesiofuro accommodates significant changes to the reconstruction of the snout, skull roof, cheek, circumorbital, and operculogular series, as well as the lower jaw. Results of a cladistic analysis incorporating these new data place Plesiofuro as a stem-group neopterygian. Additionally, phylogenetic results show that both ‘Perleidiformes’ and ‘Peltopleuriformes’ are paraphyletic, encompassing several independent stem-neopterygian subclades. As such, this study sheds new light on one of the least resolved areas of osteichthyan phylogeny: the so-called ‘subholosteans’ of the neopterygian total group.
The scanilepiform ray-finned fish Fukangichthys longidorsalis, from the Middle Triassic non-marine Kelamayi Formation of Xinjiang, China, was previously described incompletely, with many of its ...morphological characteristics unnoticed or misidentified. This study provides a revision of this problematic taxon based on an extensive reexamination of the original fossil material. Newly recognized anatomical information includes a plate-like quadratojugal, a triangular dermohyal, a wedge-shaped angular, two infraorbitals, three supraorbitals, fringing fulcra on the pectoral fins, and conical, acrodin-capped teeth in the jaws. Results of a phylogenetic analysis confirmed Fukangichthys as a scanilepiform within the Neopterygii, and provided new insights into the evolution of early actinopteran fishes. Cosmoptychius, previously regarded as the oldest stemgroup neopterygian, and Brachydegma, previously hypothesized to be the oldest halecomorph, are here reinterpreted as a stem-group actinopteran and a stem-group neopterygian, respectively. Additionally, Discoserra, previously hypothesized in a position close to the Holostei/Teleostei split, is now recovered in a clade with Ebenaqua, Bobasatrania and Platysomus gibbosus, and is therefore phylogenetically distant from crown neopterygians. As a consequence, fossil candidates for divergence time calibrations within the Actinopteri require reconsideration.
Microraptor zhaoianus is known from several specimens collected in western Liaoning Province, China. However, several aspects of the morphology of Microraptor remain unknown or ambiguous due to poor ...preservation of the described specimens. A well-preserved new specimen of Microraptor zhaoianus is described in this study. This specimen preserves significant morphological details that are not present or are poorly preserved in the other Microraptor specimens including aspects of the skull, the rib cage, and the humerus. These new characters corroborate Microraptor as a member of the Dromaeosauridae as previously suggested and support the close relationship of troodontids and dromaeosaurids (Deinonychosauria). The morphology of the rib cage also suggests Microraptor and the early volant avialans very likely may have shared a similar mechanism to assist respiration.
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Epaxial tendons play an important role in the study of the musculoskeletal system and locomotory style of dinosaurs. Although the ossified epaxial tendon lattice is fairly well known in ...Iguanodontoidea, only recently has knowledge of this complex been extended to ceratopsians. This study concerns the gross morphology and microstructure of the tendon lattice in Psittacosaurus, a basal ceratopsian. As in the neoceratopsian Chasmosaurus, the ossified tendons of Psittacosaurus form a three‐layered, lattice‐like structure. The microstructure of the tendons in large psittacosaur individuals retains an early stage of ossification, as in juvenile birds and nestling hadrosaurs, suggesting a slow developmental rate of ossification of the tendons in psittacosaur ontogeny. Comparative study indicates that a lattice‐like arrangement of three‐layered epaxial tendons is widely distributed in Cerapoda. This pattern also extends to Ankylosauria, implying a similar pattern of the epaxial muscles through the ornithischian clade. In addition, comparison with crocodiles implies that the different morphology of ossified tendons in dinosaurs may be associated with adaptive aspects of their paleobiology, not simply a side effect of skeletal ossification. In contrast to the short tendons in quadrupedal Chasmosaurus and Protoceratops, the elongated tendons in Psittacosaurus may be related to the bipedal locomotion characteristic of this taxon.
Here we describe a new diminutive varanoid from the Late Cretaceous Djadoktha Formation of Omnogov, Mongolia. The new taxon, Ovoo gurval, was found in the Nemegt Basin at the locality of Little ...Ukhaa, a locality adjacent to the rich fossil beds of Ukhaa Tolgod. The new varanoid is similar to Aiolosaurus oriens, another small varanoid from the Ukhaa Tolgod locality and several diagnostic characters of Ovoo gurval are shared with Aiolosaurus oriens. Ovoo gurval also has a pair of unusual neomorphic ossifications on the skull roof overlying the frontonasal contact. Positionally, these are unlike any neomorphic ossifications in other squamates, and certainly can be distinguished from osteoderms found in some varanoids.
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