Two spectacular fossilized dinosaur skeletons were recently discovered in Liaoning in northeastern China. Here we describe the two nearly complete skeletons of a small theropod that represent a species closely related to Compsognathus. Sinosauropteryx has the longest tail of any known theropod, and a three-fingered hand dominated by the first finger, which is longer and thicker than either of the bones of the forearm. Both specimens have interesting integumentary structures that could provide information about the origin of feathers. The larger individual also has stomach contents, and a pair of eggs in the abdomen.

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.

Multi-kilometre-thick Jurassic–Cretaceous-age sedimentary successions exposed in the southern, northwestern, and northeastern regions of the Junggar Basin display a consistent and correlative stratigraphy comprising four, stacked second-order megasequences: Badaowan, Sangonghe, Shishugou, and Kalaza. Each consists of a basal erosional unconformity or discontinuity surface and lower, middle, and upper units that are interpreted as forestepping, backstepping, and aggradational systems tracts, respectively. Each megasequence is interpreted as recording an upsection shift from active tectonism and uplift to tectonic quiescence with associated changes in crustal response and sediment supply. Basin-wide analysis of megasequences indicates that tectonism was intermittent and regionally variable. A maximum phase of subsidence and sediment accommodation is recorded in the middle unit of each megasequence and correlates with a notable abundance of fossil vertebrates suggesting a primary tectonic and basin-response control on fossil preservation. Seasonally dry climatic conditions were developed first in the northeastern region of the basin during the Pliensbachian, followed by basin-wide seasonal dryness during the Bajocian. Seasonally dry climatic conditions were permanently established across the basin by the Oxfordian and intensified during the Early Cretaceous. A seasonally dry climate from Oxfordian through the Early Cretaceous correlates positively with the widespread presence of fossil vertebrates and suggests an additional climatic control on fossil preservation.

Detachment of the three tiny middle ear bones from the reptilian mandible is an important innovation of modern mammals. Here we describe a Mesozoic eutriconodont nested within crown mammals that clearly illustrates this transition: the middle ear bones are connected to the mandible via an ossified Meckel's cartilage. The connected ear and jaw structure is similar to the embryonic pattern in modern monotremes (egg-laying mammals) and placental mammals, but is a paedomorphic feature retained in the adult, unlike in monotreme and placental adults. This suggests that reversal to (or retention of) this premammalian ancestral condition is correlated with different developmental timing (heterochrony) in eutriconodonts. This new eutriconodont adds to the evidence of homoplasy of vertebral characters in the thoraco-lumbar transition and unfused lumbar ribs among early mammals. This is similar to the effect of homeobox gene patterning of vertebrae in modern mammals, making it plausible to extrapolate the effects of Hox gene patterning to account for homoplastic evolution of vertebral characters in early mammals.

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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 featherlike 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.Résumé : Deux impressionnants squelettes de Sinosauropteryx, provenant des strates du Jurassique-Crétacé à Liaoning dans le nord-est de la Chine, attirèrent une notoriété mondiale en 1996 en tant que les premiers dinosaures recouverts de structures ressemblant à des plumes. Sinosauropteryx prima est significatif non seulement en raison de son tégument, mais aussi parce qu'il s'agit d'un coelurosaure de base et qu'il représente une étape importante dans l'évolution mal comprise des Thérapodes. Coelurosauria, qui comprend (sans s'y limiter) les dromaeosauridés, les ornithomimosaures, les oviraptorosaures, les troodontidés et les tyrannosauridés, formait le plus important rayonnement de dinosaures carnivores du Crétacé dans l'hémisphère Nord. On y inclut aussi Aves. Sinosauropteryx prima présente certains caractères qui ont été mal préservés dans les spécimens connus de son proche parent européen Compsognathus longipes. Ces caractères comprennent la plus longue queue connue pour tout Théropode et une main à trois doigts dominée par le premier doigt, qui est plus long et plus épais que l'un ou l'autre des os de l'avant-bras. Les deux spécimens ont un épais manteau de structures de type plumes, lesquelles semblent être de simples structures de branchements. L'allégation qu'un squelette de Sinosauropteryx aurait préservé la forme du foie n'est pas justifiable, si ce n'est pour la simple raison que le fossile s'était effondré dans un seul plan, ce qui aurait déformé tout organe interne mou.

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