Article

A new compsognathid theropod dinosaur from the oldest assemblage of the Jehol Biota in the Lower Cretaceous Huajiying Formation, northeastern China

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Abundant, mostly well-preserved plant, invertebrate, and vertebrate specimens in these lacustrine deposits imply short transport distances of organisms into large lake environments facilitated by low-energy currents and slack levels of fluvial and deltaic sedimentation (Ding et al., 2014), occasionally interrupted by storm events that create disorganized bedding Li et al., 2007). Stratigraphically, the DW locality is considered part of the lower Yixian Fm that consists of 100-150 m of thick shale and intercalated tuff (Chang et al., 2017;Xing et al., 2020;Yang et al., 2020;Zhang et al., 2020) (Appendix S2). The age of the DW deposit is ca. ...
Article
The Early Cretaceous terrestrial revolution involved global shifts from gymnosperm to angiosperm dominated floras. However, responses of insect herbivores to these changes remain unexamined. We evaluated 2176 highly sampled plant specimens representing 62 species/morphotypes from the 126 Ma Dawangzhangzi plant assemblage of Northeastern China. Our study consisted of horsetails, ferns, ginkgoaleans, czekanowskialeans, conifers, and an angiosperm. Their herbivory was evaluated by the functional feeding groups of hole feeding, margin feeding, and surface feeding (ectophytic feeders); piercer and suckers, and ovipositing insects (ectoendophytic feeders); mining, galling, and borings (endophytic feeders); and pathogens, collectively constituting 65 damage types (DTs). The plant assemblage was assessed for herbivory richness by DT richness, component community structure, and DT specialization on plant hosts; for herbivory intensity, it was evaluated for DT frequency, herbivorized surface area, and feeding event occurrences. Using feeding event occurrences, the data supported seven species/morphotypes as most intensely herbivorized: Liaoningocladus boii (76.6%), Czekanowskia sp. 1 (8.4%), Czekanowskia rigida (4.10%), Lindleycladus lanceolatus (3.5%), Ginkgoites sp. 2 (2.0%), Podozamites sp. 1 (1.1%), and Solenites sp. 1 (0.9%). The most herbivorized taxa were pinaleans (conifers), then czekanowskialeans, and lastly ginkgoaleans; the monodominant component community was the conifer Liaoningocladus. DT host specialization levels were low. The plant assemblage had an overall low 0.86% of foliage removed by herbivores, explained by physical and chemical antiherbivore defenses, and parasitoid attack. Although Paleozoic, gymnosperm-dominated assemblages had greater herbivory, component community structure of the three most herbivorized taxa are more similar to modern bracken fern and willow than modern gymnosperm taxa. This article is protected by copyright. All rights reserved
... Conservation of the dt2 embryonic cartilage in both birds and crocodilians implies this cartilage has likely remained present since early archosaurs, including the entire dinosaur-bird transition, despite the fact it did not ossify: only dt3 and dt4 were present as adult bones (Figure 5a-c). A small putative dt2 bone has been reported in some coelurosaurian dinosaurs (Xing et al., 2020;Supporting Information). This would be consistent with the inferred presence of a dt2 cartilage, that could ossify occasionally. ...
Article
The adult ankle of early reptiles had five distal tarsal (dt) bones, but in Dinosauria, these were reduced to only two: dt3 and dt4, articulated to metatarsals (mt) mt3 and mt4. Birds have a single distal tarsal ossification center that fuses to the proximal metatarsals to form a new adult skeletal structure: the composite tarsometatarsus. This ossification center develops within a single large embryonic cartilage, but it is unclear if this cartilage results from fusion of earlier cartilages. We studied embryos in species from four different bird orders, an alligatorid, and an iguanid. In all embryos, cartilages dt2, dt3, and dt4 are formed. In the alligatorid and the iguanid, dt2 failed to ossify: only dt3 and dt4 develop into adult bones. In birds, dt2, dt3, and dt4 fuse to form the large distal tarsal cartilage; the ossification center then develops above mt3, in cartilage presumably derived from dt3. During the entire dinosaur-bird transition, a dt2 embryonic cartilage was always formed, as inferred from the embryology of extant birds and crocodilians. We propose that in the evolution of the avian ankle, fusion of cartilages dt3 and dt2 allowed ossification from dt3 to progress into dt2, which began to contribute bone medially, while fusion of dt3 to dt4 enabled the evolutionary loss of the dt4 ossification center. As a result, a single ossification center expands into a plate-like unit covering the proximal ends of the metatarsals, that is key to the development of an integrated tarsometatarsus.
Article
The publisher regrets that this article has been temporarily removed. A replacement will appear as soon as possible in which the reason for the removal of the article will be specified, or the article will be reinstated. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
Article
Full-text available
Megaraptora is a clade of mid to large-sized theropods that are long-snouted, large-clawed, highly pneumatized, and have long and gracile metatarsals. The basal member was reported from the Barremian of Japan. A more derived clade, the Megaraptoridae, is known from the Cenomanian to Santonian of Gondwana. Here two new basal coelurosaurs from the Lower Cretaceous Sao Khua Formation of Thailand are described and named as Phuwiangvenator yaemniyomi gen. et sp. nov. and Vayuraptor nongbualamphuensis gen. et sp. nov. Phuwiangvenator is a megaraptoran coelurosaur and diagnosed by the ventrally flat sacral vertebrae with sulci in the anterior and posterior region of the centra and the anterior rim of metatarsal IV sloping proximolaterally to distomedially and being much lower than that of metatarsal III anteriorly. Vayuraptor is a basal coelurosaur and diagnosed by its astragalus which has two horizontal grooves, two fossae at the base of the ascending process, the ascending process being straight laterally and straight and parallel medially with the medial rim sloping to the tip laterally, and a long and slender astragalar ascending process. Although the position of the basal coelurosaur Vayuraptor remains unclear and must await further discovery, megaraptoran affinities are likely. The Early Cretaceous megaraptoran fossil record has been recovered from the Barremian to Aptian of Asia. All Asian megaraptorans might be a monophyletic clade or a paraphyletic series relative to the Megaraptoridae. Several specimens have been reported from the Aptian to mid-Cretaceous of Australia, and one report from the Albian of South America. These fossils show a high diversity of the Early Cretaceous megaraptorans and a wide distribution during that time. The clade then became more provincial in the Late Cretaceous.
Article
Full-text available
To date, eco-evolutionary dynamics in the ascent of tyrannosauroids to top predator roles have been obscured by a 70-million-year gap in the North American (NA) record. Here we report discovery of the oldest Cretaceous NA tyrannosauroid, extending the lineage by ~15 million years. The new taxon—Moros intrepidus gen. et sp. nov.—is represented by a hind limb from an individual nearing skeletal maturity at 6–7 years. With a ~1.2-m limb length and 78-kg mass, M. intrepidus ranks among the smallest Cretaceous tyrannosauroids, restricting the window for rapid mass increases preceding the appearance of colossal eutyrannosaurs. Phylogenetic affinity with Asian taxa supports transcontinental interchange as the means by which iconic biotas of the terminal Cretaceous were established in NA. The unexpectedly diminutive and highly cursorial bauplan of NA’s earliest Cretaceous tyrannosauroids reveals an evolutionary strategy reliant on speed and small size during their prolonged stint as marginal predators.
Article
Full-text available
Maniraptora includes birds and their closest relatives among theropod dinosaurs. During the Cretaceous period, several maniraptoran lineages diverged from the ancestral coelurosaurian bauplan and evolved novel ecomorphologies, including active flight, gigantism, cursoriality and herbivory. Propagation X-ray phase-contrast synchrotron microtomography of a well-preserved maniraptoran from Mongolia, still partially embedded in the rock matrix, revealed a mosaic of features, most of them absent among non-avian maniraptorans but shared by reptilian and avian groups with aquatic or semiaquatic ecologies. This new theropod, Halszkaraptor escuilliei gen. et sp. nov., is related to other enigmatic Late Cretaceous maniraptorans from Mongolia in a novel clade at the root of Dromaeosauridae. This lineage adds an amphibious ecomorphology to those evolved by maniraptorans: it acquired a predatory mode that relied mainly on neck hyperelongation for food procurement, it coupled the obligatory bipedalism of theropods with forelimb proportions that may support a swimming function, and it developed postural adaptations convergent with short-tailed birds.
Article
Full-text available
Enantiornithes are the most successful clade of Mesozoic birds. Here, we describe a new enantiornithine bird, Cruralispennia multidonta gen. et sp. nov., from the Protopteryx-horizon of the Early Cretaceous Huajiying Formation of China. Despite being among the oldest known enantiornithines, Cruralispennia displays derived morphologies that are unexpected at such an early stage in the evolution of this clade. A plough-shaped pygostyle, like that of the Ornithuromorpha, evolved convergently in the Cruralispennia lineage, highlighting the homoplastic nature of early avian evolution. The extremely slender coracoid morphology was previously unknown among Early Cretaceous enantiornithines but is common in Late Cretaceous taxa, indicating that by 131 million years ago this clade had already experienced considerable morphological differentiation. Cruralispennia preserves unusual crural feathers that are proximally wire-like with filamentous distal tips, a new morphotype previously unknown among fossil or modern feathers, further increasing the known diversity of primitive feather morphologies.
Article
Full-text available
Background Late Cretaceous terrestrial strata of the Neuquén Basin, northern Patagonia, Argentina have yielded a rich fauna of dinosaurs and other vertebrates. The diversity of saurischian dinosaurs is particularly high, especially in the late Cenomanian-early Turonian Huincul Formation, which has yielded specimens of rebacchisaurid and titanosaurian sauropods, and abelisaurid and carcharodontosaurid theropods. Continued sampling is adding to the known vertebrate diversity of this unit. Methodology/ Principal Findings A new, partially articulated mid-sized theropod was found in rocks from the Huincul Formation. It exhibits a unique combination of traits that distinguish it from other known theropods justifying erection of a new taxon, Gualicho shinyae gen. et sp. nov. Gualicho possesses a didactyl manus with the third digit reduced to a metacarpal splint reminiscent of tyrannosaurids, but both phylogenetic and multivariate analyses indicate that didactyly is convergent in these groups. Derived characters of the scapula, femur, and fibula supports the new theropod as the sister taxon of the nearly coeval African theropod Deltadromeus and as a neovenatorid carcharodontosaurian. A number of these features are independently present in ceratosaurs, and Gualicho exhibits an unusual mosaic of ceratosaurian and tetanuran synapomorphies distributed throughout the skeleton. Conclusions/ Significance Gualicho shinyae gen. et sp. nov. increases the known theropod diversity of the Huincul Formation and also represents the first likely neovenatorid from this unit. It is the most basal tetatanuran to exhibit common patterns of digit III reduction that evolved independently in a number of other tetanuran lineages. A close relationship with Deltadromaeus from the Kem Kem beds of Niger adds to the already considerable biogeographic similarity between the Huincul Formation and coeval rock units in North Africa.
Article
Full-text available
Our understanding of coelurosaurian evolution, particularly of bird origins, has been greatly improved, mainly due to numerous recently discovered fossils worldwide. Nearly all these discoveries are referable to the previously known coelurosaurian subgroups. Here, we report a new theropod, Fukuivenator paradoxus, gen. et sp. nov., based on a nearly complete specimen from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. While Fukuivenator possesses a large number of morphological features unknown in any other theropod, it has a combination of primitive and derived features seen in different theropod subgroups, notably dromaeosaurid dinosaurs. Computed-tomography data indicate that Fukuivenator possesses inner ears whose morphology is intermediate between those of birds and non-avian dinosaurs. Our phylogenetic analysis recovers Fukuivenator as a basally branching maniraptoran theropod, yet is unable to refer it to any known coelurosaurian subgroups. The discovery of Fukuivenator considerably increases the morphological disparity of coelurosaurian dinosaurs and highlights the high levels of homoplasy in coelurosaurian evolution.
Article
Full-text available
Megaraptoridae comprises a clade of enigmatic Gondwanan theropods with characteristic hypertrophied claws on the first and second manual digits. The majority of megaraptorids are known from South America, although a single genus (Australovenator) plus additional indeterminate material is also known from Australia. This clade has a controversial placement among theropods, and recently has been interpreted alternatively as a carcharodontosaurian or a tyrannosauroid lineage. We describe new fragmentary but associated postcranial remains from the opal fields of Lightning Ridge (middle-Albian, Griman Creek Formation) in north-central New South Wales. The new unnamed taxon exhibits a number of unusual features that suggest the presence of a hitherto unrecognized Australian megaraptorid. From an Australian perspective, the Lightning Ridge taxon predates Australovenator by c.10Ma and is minimally coeval with megaraptoran material reported from the Eumeralla Formation of Victoria (but potentially 6.1–9.5 Ma younger). It is also notable as the largest predatory dinosaur yet identified from Australia and is only the second theropod known from more than a single element. A Bayesian phylogenetic approach integrating morphological, stratigraphic and palaeogeographic information tested both the carcharodontosaurian and tyrannosauroid placements for Megaraptora. Regardless of the preferred placement among Tetanurae, rigorous palaeobiogeographic analyses support an Asian origin of Megaraptora in the latest Jurassic (about 150-135 Ma), an Early Cretaceous (about 130-121 Ma) divergence of the Gondwanan lineage leading to Megaraptoridae, and an Australian root for megaraptorid radiation. These results indicate that Australia’s Cretaceous dinosaur fauna did not comprise simply of immigrant taxa but was a source for complex two-way interchange between Australia-Antarctica-South America leading to the evolution of at least one group of apex predatory dinosaurs in Gondwana.
Article
Full-text available
Ornithuromorpha is the most inclusive clade containing extant birds but not the Mesozoic Enantiornithes. The early evolutionary history of this avian clade has been advanced with recent discoveries from Cretaceous deposits, indicating that Ornithuromorpha and Enantiornithes are the two major avian groups in Mesozoic. Here we report on a new ornithuromorph bird, Archaeornithura meemannae gen. et sp. nov., from the second oldest avian-bearing deposits (130.7[thinsp]Ma) in the world. The new taxon is referable to the Hongshanornithidae and constitutes the oldest record of the Ornithuromorpha. However, A. meemannae shows few primitive features relative to younger hongshanornithids and is deeply nested within the Hongshanornithidae, suggesting that this clade is already well established. The new discovery extends the record of Ornithuromorpha by five to six million years, which in turn pushes back the divergence times of early avian lingeages into the Early Cretaceous.
Article
Full-text available
Coelurosauria is the most diverse clade of theropod dinosaurs. Much of this diversity is present in Paraves—the clade of dinosaurs containing dromaeosaurids, troodontids, and avialans. Paraves has over 160 million years of evolutionary history that continues to the present day. The clade represents the most diverse living tetrapod group (there are over 9000 extant species of Aves—a word used here as synonomous with “bird”), and it is at the root of the paravian radiation, when dromaeosaurids, troodontids, and avialans were diverging from one another, that we find the morphology and soft tissue changes associated with the origin of modern avian flight. Within the first 15 million years of known paravian evolutionary history members of this clade exhibited a difference of nearly four orders of magnitude in body size, a value that is similar to the extreme body size disparity present today in mammalian carnivorans, avians, and varanoid squamates. In this respect, Paraves is an important case study in characterizing the patterns, processes, and dynamics of evolutionary size change. This last point is of particular interest because of the historical significance placed on the role of body size reduction in the origin of powered avian flight.Our study reviews and revises the membership of Dromaeosauridae and provides an apomorphy-based diagnosis for all valid taxa. Of the currently 31 named dromaeosaurid species, we found 26 to be valid. We provide the most detailed and comprehensive phylogenetic analysis of paravians to date in order to explore the phylogenetic history of dromaeosaurid taxa. The general pattern of paravian relationships is explored within the broader context of Coelurosauria with an emphasis on sampling basal avialans, because of their importance for character optimizations at the base of Paraves.A large dataset was constructed by merging two datasets, one examining coelurosaur relationships broadly (based on previous TWiG datasets) and the other examining avialan relationships specifically (Clarke et al., 2006). This merged dataset was then significantly revised and supplemented with novel character analysis focusing on paravian taxa. During character analysis, particular attention was given to basal members of Dromaeosauridae, enigmatic basal paravians such as Jinfengopteryx elegans and Anchiornis huxleyi, and the incorporation of new morphological information from two undescribed troodontid species from the Late Cretaceous of Mongolia. A final dataset of 474 characters scored for 111 taxa was used to address paravian evolution. This dataset is important in that it bridges a phylogenetic gap that had persisted between studies on birds and studies on all other coelurosaurs. Most scorings in this matrix were based on the direct observation of specimens.All most parsimonious trees recovered in the cladistic analysis support the monophyly of Paraves, Troodontidae, Dromaeosauridae, and Deinonychosauria. A new clade of basal troodontids is discovered including two undescribed Mongolian troodontids and Jinfengopteryx elegans. Xiaotingia and Anchiornis form a clade at the base of Troodontidae. Recently proposed relationships within Dromaeosauridae are further supported and a succession of clades from Gondwana and Asia form sister taxa to a clade of Laurasian dromaeosaurids. Avialan monophyly is strongly supported with Archaeopteryx, Sapeornis, Jeholornis, and Jixiangornis forming the successive sister taxa to the Confuciusornis node. This topology supports a more basal position for Sapeornis than previous phylogenetic analyses and indicates a progressive acquisition of a fully “avian” shoulder morphology.
Article
Full-text available
In this article, we develop a new reconstruction of the pelvic and hindlimb muscles of the large theropod dinosaur Tyrannosaurus rex. Our new reconstruction relies primarily on direct examination of both extant and fossil turtles, lepidosaurs, and archosaurs. These observations are placed into a phylogenetic context and data from extant taxa are used to constrain inferences concerning the soft-tissue structures in T. rex. Using this extant phylogenetic bracket, we are able to offer well-supported inferences concerning most of the hindlimb musculature in this taxon. We also refrain from making any inferences for certain muscles where the resulting optimizations are ambiguous. This reconstruction differs from several previous attempts and we evaluate these discrepancies. In addition to providing a new and more detailed understanding of the hindlimb morphology of T. rex--the largest known terrestrial biped--this reconstruction also helps to clarify the sequence of character-state change along the line to extant birds.
Article
Full-text available
Recent discoveries of spectacular dinosaur fossils overwhelmingly support the hypothesis that birds are descended from maniraptoran theropod dinosaurs, and furthermore, demonstrate that distinctive bird characteristics such as feathers, flight, endothermic physiology, unique strategies for reproduction and growth, and a novel pulmonary system originated among Mesozoic terrestrial dinosaurs. The transition from ground-living to flight-capable theropod dinosaurs now probably represents one of the best-documented major evolutionary transitions in life history. Recent studies in developmental biology and other disciplines provide additional insights into how bird characteristics originated and evolved. The iconic features of extant birds for the most part evolved in a gradual and stepwise fashion throughout archosaur evolution. However, new data also highlight occasional bursts of morphological novelty at certain stages particularly close to the origin of birds and an unavoidable complex, mosaic evolutionary distribution of major bird characteristics on the theropod tree. Research into bird origins provides a premier example of how paleontological and neontological data can interact to reveal the complexity of major innovations, to answer key evolutionary questions, and to lead to new research directions. A better understanding of bird origins requires multifaceted and integrative approaches, yet fossils necessarily provide the final test of any evolutionary model. Copyright © 2014, American Association for the Advancement of Science.
Article
Full-text available
The evolution of birds from theropod dinosaurs was one of the great evolutionary transitions in the history of life [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and 22]. The macroevolutionary tempo and mode of this transition is poorly studied, which is surprising because it may offer key insight into major questions in evolutionary biology, particularly whether the origins of evolutionary novelties or new ecological opportunities are associated with unusually elevated “bursts” of evolution [23 and 24]. We present a comprehensive phylogeny placing birds within the context of theropod evolution and quantify rates of morphological evolution and changes in overall morphological disparity across the dinosaur-bird transition. Birds evolved significantly faster than other theropods, but they are indistinguishable from their closest relatives in morphospace. Our results demonstrate that the rise of birds was a complex process: birds are a continuum of millions of years of theropod evolution, and there was no great jump between nonbirds and birds in morphospace, but once the avian body plan was gradually assembled, birds experienced an early burst of rapid anatomical evolution. This suggests that high rates of morphological evolution after the development of a novel body plan may be a common feature of macroevolution, as first hypothesized by G.G. Simpson more than 60 years ago [25].
Article
Full-text available
The Early Cretaceous Jehol Biota of northeastern China has become famous over the last two decades as a source of feathered avialan and non-avialan theropods, preserved alongside an array of other fossil vertebrates, invertebrates, and plants. Still more recently, a rich assemblage referred to in this paper as the Daohugou Biota has begun to emerge from Jurassic strata in the same region. Like their counterparts from the Jehol Biota, Daohugou Biota vertebrate specimens are typically preserved in fine-grained lacustrine beds and often retain feathers and other soft-tissue features. At present, 30 vertebrate taxa (five salamanders, one anuran, two lizards, 13 pterosaurs, five dinosaurs, and four mammals) are known from the Daohugou Biota, which was first recognized at the Daohugou locality in Inner Mongolia. The presence of the salamander Chunerpeton tianyiensis, proposed in this paper as an index fossil for the Daohugou Biota, links the Daohugou locality to five other fossil-producing areas in the provinces of Hebei and Liaoning. The strata containing the Daohugou Biota are close to the Middle–Upper Jurassic boundary and belong at least partly to the regionally widespread Tiaojishan Formation. In general, the vertebrate fauna of the Daohugou Biota is strikingly different from that of the Jehol Biota, although paravian dinosaurs, anurognathid pterosaurs, and salamanders with cryptobranchid and hynobiid affinities occur in both. Nevertheless, the Daohugou Biota and the Jehol Biota are two successive Lagerstätte assemblages that collectively offer a taphonomically consistent window into the Mesozoic life of northeast Asia over a significant span of geologic time.
Article
Full-text available
We describe the anatomy of a new coelurosaurian theropod Aorun zhaoi gen. et sp. nov., from the Middle–Late Jurassic of Xinjiang, China. Histological analysis of the holotype and only known specimen shows that the new taxon is represented by the skeleton of a juvenile individual aged no more than one year. A phylogenetic analysis of theropod relationships places Aorun as a basal member of the Coelurosauria. Although the sole use of a sub-adult ontogenetic exemplar is potentially problematic for phylogenetic reconstruction, we show that the phylogenetic position of Aorun as a member of Coelurosauria is robust to the exclusion of characters known to change during theropod ontogeny. Aorun is the seventh theropod taxon, and temporally oldest coelurosaur, known from the Shishugou Formation, which has one of the most taxonomically diverse Jurassic coelurosaurian theropod faunas in the world.http://zoobank.org/urn:lsid:zoobank.org:pub:5CC73577-9EB3-47AB-9983-1677B278EFFD
Article
Full-text available
A new, large compsognathid theropod, Huaxiagnathus orientalis gen. et sp. nov., from the Early Cretaceous Yixian Formation deposits of Liaoning Province, People's Republic of China is described. The holotype specimen is nearly complete, lacking only the distal portion of the tail. It is the second largest theropod taxon discovered from Jehol Group sediments. Like all compsognathids, Huaxiagnathus has short forelimbs and a relatively unspecialised coelurosaur body plan. Previously, fairly complete skeletons existed for only two small‐bodied taxa of compsognathids, Compsognathus longipes from the Late Jurassic of Western Europe and Sinosauropteryx prima, also from the Yixian. The phylogenetic position of Huaxiagnathus orientalis was analysed using an extensive matrix of theropod characters from many taxa. Huaxiagnathus orientalis fell out at the base of the Compso‐gnathidae, as it lacks the forelimb adaptations of more derived compsognathids. The addition of Huaxiagnathus and the two other compsognathid species to our data matrix resulted in the placement of Compsognathidae near the base of Maniraptora. Furthermore, Alvarezsauridae, Paraves, and a monophyletic Therizinosauroidea + Oviraptorosauria clade fall out in an unresolved trichotomy in the strict consensus of our most parsimonious trees.
Article
Full-text available
The lower Cretaceous Yixian and Jiufotang formations contain numerous exceptionally well-preserved invertebrate, vertebrate and plant fossils that comprise the Jehol Biota. Freshwater and terrestrial fossils of the biota usually occur together within some horizons and have been interpreted as deposits of mass mortality events. The nature of the events and the mechanisms behind the exceptional preservation of the fossils, however, are poorly understood. Here, after examining and analysing sediments and residual fossils from several key horizons, we postulate that the causal events were mainly phreatomagmatic eruptions. Pyroclastic density currents were probably responsible for the major causalities and for transporting the bulk of the terrestrial vertebrates from different habitats, such as lizards, birds, non-avian dinosaurs and mammals, into lacustrine environments for burial. Terrestrial vertebrate carcasses transported by and sealed within the pyroclastic flows were clearly preserved as exceptional fossils through this process.
Article
Full-text available
The Late Cretaceous (∼95-66 million years ago) western North American landmass of Laramidia displayed heightened non-marine vertebrate diversity and intracontinental regionalism relative to other latest Cretaceous Laurasian ecosystems. Processes generating these patterns during this interval remain poorly understood despite their presumed role in the diversification of many clades. Tyrannosauridae, a clade of large-bodied theropod dinosaurs restricted to the Late Cretaceous of Laramidia and Asia, represents an ideal group for investigating Laramidian patterns of evolution. We use new tyrannosaurid discoveries from Utah-including a new taxon which represents the geologically oldest member of the clade-to investigate the evolution and biogeography of Tyrannosauridae. These data suggest a Laramidian origin for Tyrannosauridae, and implicate sea-level related controls in the isolation, diversification, and dispersal of this and many other Late Cretaceous vertebrate clades.
Article
Full-text available
We performed additional preparation on the holotype skeleton of Nqwebasaurus thwazi and discovered new skeletal material. We describe this material, which includes a maxilla with small, conical, unserrated teeth and bones of the braincase, as well as parts of the holotype postcranial anatomy that were previously poorly documented. We incorporate this new anatomical information into a broadly sampled matrix designed to test theropod relationships. Our phylogenetic results hypothesize that Nqwebasaurus is the basalmost ornithomimosaur, and recover numerous characters supporting this relationship, including features of the maxilla, frontal, dentition, axial skeleton, forelimb and hindlimb. Nqwebasaurus is the first African ornithomimosaur and the first Gondwanan member of this group known from articulated skeletal material, supporting the hypothesis that coelurosaurian groups were cosmopolitan during their early evolutionary history. The presence of reduced dentition and a gastric mill in Nqwebasaurus strongly suggest that this taxon was herbivorous.
Article
Full-text available
: We report on a new species of enantiornithine bird from the Lower Cretaceous Qiaotou Formation of northern Hebei, China. The new taxon, Shenqiornis mengi gen. et sp. nov., possesses several enantiornithine synapomorphies but is unique from other known species. The specimen has a well-preserved skull that reveals new information about enantiornithine cranial morphology. The new taxon possesses a large postorbital with a long tapering jugal process indicating that some enantiornithines may have had a fully diapsid skull, as in Confuciusornis. The tooth morphology of the specimen is unique and likely represents a previously unknown trophic specialization within Enantiornithes.
Article
Full-text available
We describe a new coelurosaurian theropod, Zuolong salleei, gen. et sp. nov., from exposures of the upper part of the Shishugou Formation at the Wucaiwan locality, Xinjiang Autonomous Region, People's Republic of China. Zuolong has a large, inclined quadrate foramen that extends onto the medial surface of the quadratojugal, an unusually large fovea capitis on the femoral head, and an apomorphically large distal condyle of metatarsal III with a medially projecting flange on the extensor surface. Radiometric dating of the Shishugou Formation constrains the age of the specimen to the beginning of the Late Jurassic (Oxfordian). A cladistic analysis of Zuolong salleei in a broadly sampled theropod data matrix recovers it as a basal coelurosaur. These data make Zuolong one of the oldest coelurosaur fossils yet known that preserves both cranial and postcranial bones.
Article
Full-text available
The bird fossil-bearing deposits at the Jiecaigou section, correlative to the Dabeigou Formation, in Fengning, Hebei Province, northern China, is well known for yielding a fossil assemblage representing the earliest evolutionary stage of the Jehol Biota. The precise age of the fossil-bearing deposits, however, is unknown. The 40Ar/39Ar age spectrum obtained on bulk K-feldspars from the tuff layer about 2 m below the bird fossil-bearing layer gave a plateau age of 129.0 +/- 1.3 Ma (2sigma, full external error) and an isochron age of 132.3 +/- 4.5 Ma (2sigma, full external error). Seventeen total-fusion 40Ar/39Ar ages on K-feldspars from the interbedded tuff about 6 m below the fossil-bearing layer resulted in a weighted mean of 130.7 +/- 1.4 Ma (2sigma, full external error). These dates suggest an age of ~131 Ma for the early Jehol Biota and combined with previous dating indicate that this biota lasted at least from 131 Ma to 120 Ma (Late Hauterivian to Aptian). These dates also represent the earliest absolute age for known enantiornithine birds in the world.
Article
Full-text available
The theropod dinosaur Aniksosaurus darwini gen. et sp. nov. has been recovered from the Upper Cretaceous, Bajo Barreal Formation, of Central Patagonia. Aniksosaurus darwini gen. et sp. nov. was a small tetanurine, approximately 2 meters long. Aniksosaurus exhibits several unique traits (e.g., cranial cervical ver- tebrae with dorsoventrally deep neural arches, provided with a pair of cavities at their cranial surfaces; neural canal wide; cranial caudals with ventral sagittal keel, and transverse processes triangular-shaped in dorsal view; manual ungual phalanges robust; ilium with extremely expanded brevis shelf; femur with deep notch for M. Iliotrochantericus; metatarsal and digit IV of pes transversely narrow). Available postcranial bones of Aniksosaurus exhibit derived features of Coelurosauria (e.g., ilium with well developed cuppedicus fossa; femur with anterior trochanter proximally projected, almost reaching the level of the articular head; greater tro- chanter craniocaudally expanded; femoral head rectangular-shaped in cranial aspect; and fibular shaft craniocaudally narrow), as well as characteristics suggesting that the new Patagonian taxon is more derived than some basal coelurosaurians such as compsognathids, Ornitholestes, and coelurids. Comparisons with maniraptoriforms (a clade including Ornithomimosauria, Tyrannosauridae, Oviraptorosauria, Alvarezsauridae and Paraves) support that Aniksosaurus is less derived than these theropods. In sum, Aniksosaurus is here considered as a Late Cretaceous survivor of a basal coelurosaurian radiation.
Article
Full-text available
constraints reveal that the opisthotonic posture is not a peri-but a postmortem phenomenon. By analysing the timeline of decomposition, it is possible to recognise different stages of decay, depending on the varying decay resistance of soft tissues. Adipocere formation must have blocked further decay until embedding was completed by minimal sedimen-tation. Analyses of the palaeoenvironment of the basins of the Solnhofen Archipelago show that the conditions of deposition of individual basins cannot be considered to be similar, even inside the same time frame. Therefore, a gen-eralised approach of looking at the depositional setting must be excluded. Assumptions by Faux and Padian (2007) that the accepted palaeoenvironmental reconstruction of the Solnhofen Fossillagerstätte has to be questioned in the light of the opisthotonic posture hypothesis enforce the need for a review of palaeoecological factors of the Franconian Plat-tenkalks from a taphonomic perspective.
Article
Full-text available
We provide a detailed study of the morphology of the holotype of Juravenator starki from the Late Jurassic of the Solnhofen area of southern Germany. The incompletely ossified surface of multiple bones and lack of several skeletal fusions indicate that Juravenator starki is based on an immature specimen. Nonetheless, numerous unique morphologies and bone proportions distinguish this taxon from Compsognathus longipes, the only previously named non-avian theropod dinosaur from the Late Jurassic of the Solnhofen Archipelago. Yet, its skeletal anatomy is most similar to that of Compsognathus and other theropods that have often been regarded as closely related to the latter - sometimes within a monophyletic Compsognathidae. Juravenator is characterized by having a small size (∼ 0.75-meter-long in the holotype) with few maxillary teeth, lack of a premaxillary-maxillary diastema, an antorbital fenestra subequal in length to orbit, an elongate scapula that is narrowest at its neck, a proportionally short humerus and high and abruptly tapered manual claws, and bow-like zygapophysial articulations in the mid-caudal vertebrae. Portions of the epidermis preserved mainly along the tail provide the only glimpse of the morphology of the skin of basal coelurosaurs, and structures newly revealed under UV light hint at the possibility of filamentous integumentary structures - akin to those interpreted as proto-feathers in other basal coelurosaurs - also covering the body of this dinosaur. The discovery of Juravenator has provided evidence of morphologies - from details of the skull to the epidermis - that are poorly known in other theropods interpreted as at or near the base of Coelurosauria, and thus contributes significantly to our understanding of the evolutionary history of this clade. The exquisitely preserved holotipic skeleton adds significantly to the meager record of small-bodied Late Jurassic theropods.
Article
Full-text available
A new ornithomimosaur from the Yixian Formation of Liaoning Province People's Republic of China is described. These beds are near the Jurassic-Cretaceous boundary. This specimen is interesting because it has several primitive characters for ornithomimosaurs such as teeth and a short first metacarpal. This taxon is placed in a phylogenetic analysis of Coelurosauria and shown to be near the base of the ornithomimosaur clade. Using this phylogeny we comment on the biogeographic history of this group.
Article
Full-text available
Data from vertebrate microsites are important in paleoecological reconstructions, but their usefulness has been limited because of undemonstrated repeatability of sampling data and the time- and labor-intensive nature of their retrieval. Re-examination of a previously studied vertebrate microsite revealed that repeatable diversity and abundance data are obtainable using a controlled sorting methodology. It was found that a curve fitted to a plot of empirical diversity vs. sampling frequency will tend toward an asymptote as sampling frequency increases, indicating that the likelihood of discovery of new taxa having a major impact upon a paleoecological interpretation is diminishing. Rarefaction analysis was applied to the data obtained, and the rarefaction curve provided support for the behavior of the empirical diversity curve. It was also found that as sampling frequency increases, rank orders of relative abundance stabilize among the most common taxa in the sample, indicating that the likelihood of discovery of highly abundant taxa is diminishing. Adequate sampling of a vertebrate microsite can thus be achieved by dividing the original field sample into many small subsamples, and additively plotting diversity and relative abundance data. Once the diversity curve begins to tend toward an asymptote, and the abundance ranks among the most common taxa have stabilized, it is necessary to continue sampling only until double this number of subsamples has been analyzed in order to confirm the established patterns. Proceeding in this fashion will verify that ostensible exhaustion of the taxa present has been achieved. Standardization of sampling methodology will allow similarly compiled data to be compared, both from a single site and among multiple sites, improving the reliability of palaeoecological interpretations generated from vertebrate microsites.
Article
Full-text available
Two skeletons of the large compsognathid Sinocalliopteryx gigas include intact abdominal contents. Both specimens come from the Jianshangou Beds of the lower Yixian Formation (Neocomian), Liaoning, China. The holotype of S. gigas preserves a partial dromaeosaurid leg in the abdominal cavity, here attributed to Sinornithosaurus. A second, newly-discovered specimen preserves the remains of at least two individuals of the primitive avialan, Confuciusornis sanctus, in addition to acid-etched bones from a possible ornithischian. Although it cannot be stated whether such prey items were scavenged or actively hunted, the presence of two Confuciusornis in a grossly similar state of digestion suggests they were consumed in rapid succession. Given the lack of clear arboreal adaptations in Sinocalliopteryx, we suggest it may have been an adept stealth hunter.
Article
Phylogenetic relationships of megaraptorid theropods are under intense debate. Some authors interpret them as archaic allosauroids that survived up to Late Cretaceous, whereas others consider megaraptorids as basal tyrannosauroids. The recently described Patagonian taxon Murusraptor barrosaensis offers novel information on skull, axial and hind limb anatomy, all of which may help in elucidating the phylogenetic affinities of megaraptorids as a whole. Murusraptor is particularly similar to juvenile specimens of tyrannosaurids; both share: 1) lacrimal with a long anterior process; 2) corneal process and; 3) lateral pneumatic fenestra; 4) square and dorsoventrally low frontals; 5) parietals with well-developed sagittal and nuchal crests, among other features. The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affiliation with Tyrannosauroidea (supported by >20 synapomorphies).
Article
Dinosaurs were large-bodied land animals of the Mesozoic that gave rise to birds. They played a fundamental role in structuring Jurassic-Cretaceous ecosystems and had physiology, growth, and reproductive biology unlike those of extant animals. These features have made them targets of theoretical macroecology. Dinosaurs achieved substantial structural diversity, and their fossil record documents the evolutionary assembly of the avian body plan. Phylogeny-based research has allowed new insights into dinosaur macroevolution, including the adaptive landscape of their body size evolution, patterns of species diversification, and the origins of birds and bird-like traits. Nevertheless, much remains unknown due to incompleteness of the fossil record at both local and global scales. This presents major challenges at the frontier of paleobiological research regarding tests of macroecological hypotheses and the effects of dinosaur biology, ecology, and life history on their macroevolution.
Article
A spectacular pair of Sinosauropteryx skeletons from Jurassic-Cretaceous strata of Liaoning in northeastern China attracted worldwide notoriety in 1996 as the first dinosaurs covered with feather-like structures. Sinosauropteryx prima is important not only because of its integument, but also because it is a basal coelurosaur and represents an important stage in theropod evolution that is poorly understood. Coelurosauria, which includes (but is not limited to) dromaeosaurids, ornithomimosaurs, oviraptorosaurs, troodontids, and tyrannosaurids, formed the most important radiation of Cretaceous carnivorous dinosaurs in the Northern Hemisphere. It also includes Aves. Sinosauropteryx prima has a number of characters that were poorly preserved in known specimens of the closely related Compsognathus longipes from Europe. These include the longest tail known for any theropod and a three-fingered hand dominated by the first digit, which is longer and thicker than either of the bones of the forearm. Both specimens have a thick coat of feather-like structures, which seem to be simple branching structures. The claim that one skeleton of Sinosauropteryx has preserved the shape of the liver is unsupportable, if only because the fossil had collapsed into a single plane, which would have distorted any soft, internal organs.
Article
We describe Tratayenia rosalesi gen. et sp. nov., a new megaraptoran theropod dinosaur from the Upper Cretaceous of Patagonia, Argentina. The holotype consists of a well-preserved, mostly articulated series of dorsal and sacral vertebrae, two partial dorsal ribs, much of the right ilium, and pubis and ischium fragments. It was found in a horizon of the Upper Cretaceous (Santonian) Bajo de la Carpa Formation of the Neuquén Group in the Neuquén Basin exposed near the town of Añelo in Neuquén Province of northwestern Patagonia. Phylogenetic analysis recovers Tratayenia within the Gondwanan megaraptoran subclade Megaraptoridae. The new taxon exhibits similarities to other megaraptorids such as Aerosteon riocoloradensis, Megaraptor namunhuaiquii, and Murusraptor barrosaensis, but also presents differences in the architecture of the dorsal and sacral vertebrae and the morphology of the ilium. Tratayenia is the first megaraptoran that unequivocally preserves the complete sequence of sacral vertebrae, thereby increasing knowledge of the osteology of the clade. Moreover, depending on the chronostratigraphic ages of the stratigraphically controversial megaraptorids Aerosteon and Orkoraptor burkei, as well as the phylogenetic affinities of several fragmentary specimens, the new theropod may be the geologically youngest megaraptorid or megaraptoran yet discovered. Tratayenia is also the largest-bodied carnivorous tetrapod named from the Bajo de la Carpa Formation, reinforcing the hypothesis that megaraptorids were apex predators in southern South America from the Turonian through the Santonian or early Campanian, following the extinction of carcharodontosaurids.
Article
Benthic ecologists have successfully applied rarefaction techniques to the problem of compensating for the effect of sample size on apparent species diversity (= species richness). The same method can be used in studies of diversity at higher taxonomic levels (families and orders) in the fossil record where samples represent world-wide distributions of species or genera over long periods of geologic time. Application of rarefaction to several large samples of post-Paleozoic echinoids (totaling 7,911 species) confirms the utility of the method. Rarefaction shows that the observed increase in the number of echinoid families since the Paleozoic is real in the sense that it cannot be explained solely by the increase in numbers of preserved species. There has been no statistically significant increase in the number of families since mid-Cretaceous, however. At the order level, echinoid diversity may have been nearly constant since late Triassic or early Jurassic.
Article
A new compsognathid dinosaur, Sinocalliopteryx gigas gen. et sp. nov., is erected based on a complete skeleton from the Early Cretaceous Yixian Formation of western Liaoning, northeastern China. It shares the features with Huaxiagnathus orientalis in having a manus as long as the humerus plus radius, very large and subequally long manual claws I and II, and reduced olecranon process on the ulna. But it differs from Huaxiagnathus orientalis in having the much large size, a very long maxillary process of premaxilla not extending the vertical level of the maxillary antorbital fossa, and the proportionally longer ulna and so on. Sinocalliopteryx gigas gen. et sp. nov. represents the largest species among the known compsognathid dinosaurs, suggesting the tendency of the body enlargement in compsognathids to some extent. The long filamentous integuments are attached to the whole body of this compsognathid, confirming that such integuments evolved firstly in the basal coelurosaurs. This new giant compsognathid was a fierce carnivorous theropod, as shown further by an incomplete dromaeosaurid leg inside its abdominal cavity.
Article
We report on a new enantiornithine Eopengornis martini gen. et sp. nov. from the lowest horizon of the Jehol Biota in Hebei, China; dated at 130.7 Mya, this is the second oldest avian bearing fossil deposit in the world, recording the First Appearance Datum of Enantiornithes. The new specimen, only the second enantiornithine and third bird reported from this horizon, preserves numerous synapomorphies with the largest Lower Cretaceous enantiornithine Pengornis houi from the Jiufotang Formation dated at 120 Mya. Together, they form a new avian lineage that lasted over 10 Myr, which is longer than any known clade of Lower Cretaceous enantiornithine. Eopengornis reveals new information about basal enantiornithine morphology such as the presence of a metatarsal V, helping to clarify the early evolution of these dominant Cretaceous avians. Furthermore, Eopengornis preserves a previously unrecognized tail morphology: a pair of elongate fully pennaceous rachis dominated feathers. This discovery confirms hypotheses proposing that the rachis dominated racket-plumes in basal birds represent modified pennaceous feathers. We suggest that the ornamental racket-plumes in enantiornithines and Confuciusornis evolved independently from the basal pygostylian condition, which we infer was a tail formed of normal flight feathers. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 805–819.
Article
This paper describes a new enantiornithine fossil bird, Vescornis hebeiensis, nov. sp. from the Early Cretaceous of China. We refer Vescornis to the crown clade Euenantiornithes based on several characteristics observed in the thoracic girdle and wing. Vescornis also exhibits characteristics that separate it from other enantiornithine birds, such as the short alular phalanx, the vestigial manual claws, and the well-developed and long foot claws. These features suggest an adaptation towards an improved flight capability, while the ability of Vescornis to climb is reduced compared with many other enantiornithine birds. Résumé : Cet article décrit un nouvel oiseau fossile, Vescornis hebeiensis, sp. nov. (groupe des Enantiornithes), du Crétacé précoce en Chine. Nous référons Vescornis au clade maître Euenantiornithes d'après plusieurs caractéristiques observées dans la ceinture thoracique et les ailes. Vescornis démontre aussi des caractéristiques qui le distinguent des autres oiseaux du groupe des Enantiornithes : la courte phalange de l'alula, les griffes manuelles atrophiées et les griffes longues et bien développées des pieds. Ces caractéristiques suggèrent une adaptation à une meilleure capacité de vol alors que l'habilité de Vescornis à grimper est réduite si on la compare à de nombreux autres oiseaux du groupe des Enantiornithes. (Traduit par la Rédaction) Zhang et al. 1107
Article
The recent discovery of small paravian theropod dinosaurs with well-preserved feathers in the Middle-Late Jurassic Tiaojishan Formation of Liaoning Province (northeastern China) has challenged the pivotal position of Archaeopteryx, regarded from its discovery to be the most basal bird. Removing Archaeopteryx from the base of Avialae to nest within Deinonychosauria implies that typical bird flight, powered by the forelimbs only, either evolved at least twice, or was subsequently lost or modified in some deinonychosaurians. Here we describe the complete skeleton of a new paravian from the Tiaojishan Formation of Liaoning Province, China. Including this new taxon in a comprehensive phylogenetic analysis for basal Paraves does the following: (1) it recovers it as the basal-most avialan; (2) it confirms the avialan status of Archaeopteryx; (3) it places Troodontidae as the sister-group to Avialae; (4) it supports a single origin of powered flight within Paraves; and (5) it implies that the early diversification of Paraves and Avialae took place in the Middle-Late Jurassic period.
Article
A study of the distribution of dinosaurian body masses in the Dinosaur Park Formation (DPF; Campanian; southern Alberta), reveals a prominent negative skew; a pattern distinct from those of modern terrestrial faunas. We find a direct and robust correlation between taxon size (estimated live body mass) and known completeness. There is a clear dichotomy between large and small-bodied taxa at around 60 kg, in which taxa less than 60 kg are significantly less complete (mean completeness = 7.6%) than those with an estimated mass of 60 kg or greater (mean = 78.2%). Along with completeness, there is also a strong association of body size and taphonomic mode, with small taxa known largely from isolated and occasionally associated remains, and large taxa known from articulated skeletons. In addition, there is a significant correlation between taxon body mass and both date of discovery and of description, with taxa < 60 kg taking an average of 65.9 and 75.6 years to discover and describe, respectively, compared to 33.6 and 34.1 years for taxa > 60 kg. The rates of both cumulative discovery and description for large taxa are best described by a logarithmic curve nearing an asymptote, whereas small taxa show either a linear or power increase through time. This suggests that our current knowledge of the large-bodied dinosaur assemblage is reasonably representative of the true biological fauna with few discoveries likely to be made in the future. However, small taxa are greatly underestimated in both their diversity and abundance, with many more potential discoveries to be made. Given that (1) the sedimentary deposits and fossil assemblages in the DPF together represent one of the best studied examples of a Mesozoic alluvial‐paralic (terrestrial) ‘palaeoecosystem,’ and (2) similar patterns have been suggested (but not documented) for other Mesozoic terrestrial ecosystems in the Western Interior of North America, we suggest that this pattern of size bias may typify vertebrate fossil assemblages in terrestrial Mesozoic systems. If so, such biases must be considered before patterns of diversity in dinosaur communities through time can be considered accurate, or used to compare and interpret Mesozoic palaeoecosystems.
Article
A reexamination of the French Compsognathus corallestris, from the Portlandian lithographic limestones of the Tithonian of southern France, provides new cranial and postcranial information crucial for a better understanding of the taxon Compsognathus. The French Compsognathus is almost completely preserved either as actual bony elements or as impressions, lacking only the distal portion of its tail, and some of the manual phalanges. It is preserved in two blocks, one containing the skull and postcranial skeleton up to the seventh caudal vertebra, the other caudal vertebrae nine through 31. Compsognathids are currently known from Europe, South America, and China. The absence of an external mandibular fenestra, dorsally fan-shaped dorsal neural spines with hook-shaped ligament attachments, and a very short McI and a PhI-1, which is stouter than the radius distinguish compsognathids from other coelurosaurs. Anatomical and morphological characters of the Bavarian specimen of Compsognathus are nearly identical to those of the French specimen. The differences are related to ontogenetic or within-species variation or are caused by preservational factors. Therefore this study proposes that C. corallestris is a subjective junior synonym of Compsognathus longipes from Bavaria.
Article
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.
Article
Over the past 10 years, numerous dinosaur specimens covering several major dinosaurian clades have been recovered from the Lower Cretaceous Jehol Group of western Liaoning. Among ornithischians from the Jehol Group, ornithopod fossils shed new light on the evolution of this largest ornithischian group; ankylosaurian discoveries add morphological diversity relevant to the highly specialized ankylosaurian body-plan and ceratopsian occurrences offer a chance to study patterns of morphological change at the base of the Ceratopsia. The most significant discoveries are exceptionally well-preserved theropod specimens covering most major coelurosaurian groups. Most theropod taxa from the Jehol Biota are the earliest, most basal members of coelurosaurian sub-clades and provide substantial new information important for the reconstruction of coelurosaurian phylogeny and understanding the character evolution. The examination of character distributions along the coelurosaurian lineages reveals that the major structural modifications seen in birds were acquired sequentially and hierarchically early in coelurosaurian evolution. Most significantly, the Liaoning theropod discoveries advanced our understanding of two long-debated evolutionary issues: the origin and early evolution of feathers and the origin of avian flight. The known distribution of the feather-like integumentary structures and true feathers along the coelurosaurian lineages suggests that: (1) simple, filamentous integuments represent a primitive morph in feather evolution; (2) pennaceous feathers evolved early in maniraptoran evolution; and (3) feathers with aerodynamic features originated before the origin of birds. The presence of flight feathers on the metatarsus represents a new morph that is not known previously, but it has implications for understanding the origin of avian flight. The discovery of four-winged dinosaurs was suggested to provide strong evidence supporting the ‘tree-down’ hypothesis for the origin of avian flight, though in-depth analysis and more data are needed to confirm this. A brief analysis of the fossil preservation and faunal composition reveals several interesting characteristics: (1) Volcanic activity might have contributed to the exceptional preservation of dinosaurian skeletons and in particular their soft tissues; (2) Different from most other dinosaur faunas, the Jehol dinosaur fauna has a low ornithischian specific diversity relative to a high theropod specific diversity; and (3) the Liaoning theropods show a strong tendency toward secondary herbivory. The faunal composition suggests a complex biogeographic history for this fauna and provides negative evidence for the hypothesis that eastern Asia was isolated from the Middle Jurassic through late Early Cretaceous times. Copyright © 2006 John Wiley & Sons, Ltd.
Article
Jinfengopteryx is a newly uncovered Archaeopteryx-like avialan bird outside Germany, which was found from the Jehol Biota of northern Hebei in northeastern China. It shares many characters only with Archaeopteryx by the possession of three fenestrae in the antorbital cavity, 23 caudal vertebrae and long tail feathers attached to all the caudal vertebrae. But the former differs from the latter in the relatively short and high preorbital region of skull, more and closely packed teeth, much shorter forelimb compared to hindlimb. Such differences indicate Jinfengopteryx is even slightly more primitive than Archaeopteryx, although both birds can be placed at the root position of the avialan tree based on cladistic analysis. Shenzhouraptor is suggested to be slightly more advanced than Jinfengopteryx + Archaeopteryx, supported by some derived features in teeth, shoulder girdles and forelimbs such as the reduction of tooth number, dorsolaterally directed glenoid facet, very long forelimb and comparatively short manus. Meanwhile, the tail of Shenzhouraptor shows more primitive characters than those of Jinfengopteryx and Archaeopteryx, e.g., the strikingly longer tail composed of more caudal vertebrae and the long tail feathers attached only to distal caudal segments. The mixed primitive and advanced characters reveal the evident mosaic evolution among long-tailed avialan birds.
Article
The so-called Jehol Biota, an excellently preserved Early Cretaceous biota consisting of both lacustrine and terrestrial organisms, is one of the most important Mesozoic fossillagerstätten. Although there have been extensive palaeontological studies, little work has been done on the volcanic settings under which the biota was preserved. The Sihetun area is the most famous fossil locality of the Jehol Biota in western Liaoning, and the volcanic succession in that area is the most representative and best studied. We use a case study of the volcanic succession of the Lower Cretaceous Yixian Formation in the Sihetun area to reconstruct the volcanic complexes and their history, to propose a depositional model of the volcanic successions, and to understand the relationship between volcanic activity and fossil preservation in western Liaoning. The volcanic succession comprises four volcanic complexes, each with distinct products; a shield volcano, an intermediate multi-vent center, a volcanic lake (in summit caldera), and finally lava domes. The presence of a caldera is postulated from exposures which suggest the presence of an inner topographic wall, bounding faults, and intra-caldera fill. Frequent volcanic activities and widespread existence of volcanic lakes during the Early Cretaceous are thought to account for the exceptional preservation of invertebrates and vertebrates of the Jehol Biota in western Liaoning.Research highlights►We reconstruct the volcanic complexes and their history of the Yixian Formation. ►We aim to untangle the relationship between volcanism and fossil preservation. ►Four volcanic complexes are recognized. ►A caldera origin is proposed for the Early Cretaceous volcanic lake in the Sihetun. ►Volcanic activities adjacent lakes increase the chances of fossil preservation.