A new Microraptor Relative Found in Cretaceous China?

A new microraptorine specimen (Theropoda: Dromaeosauridae) with a brief comment on the evolution of compound bones in theropods

Authors:

Xu et al

Abstract:

Microraptorinae is a recently discovered subgroup of dromaeosaurid theropods, mostly comprising species from the Lower Cretaceous Jehol Group of western Liaoning, China. Here we describe a new microraptorine specimen from the Jiufotang Formation (the upper section of the Jehol Group) of Dapingfang, Chaoyang, Liaoning, which displays interesting morphological features not previously documented within Microraptorinae. Noteworthy are several osteological features, including dental and ischial ones, which are transitional between the condition of Sinornithosaurus and that of Microraptor. These features highlight the existence of a spectrum of morphological variation between Sinornithosaurus, which is more like a typical dromaeosaurid, and Microraptor, which shares many characteristics with troodontids. However, the taxonomic significance of these variations has not to be fully assessed yet. A feature deserving special mention is the fusion of the pubes to the ilia in this specimen, which has implications for the evolution of compound bones in theropods+. Our preliminary analysis suggests that many compound bones in birds have been formed by sequential fusion of multiple elements in a peramorphic process.

New Findings in the Study of Feathered Dinosaurs and Pterosaurs

New Findings in the Study of Feathered Dinosaurs and Pterosaurs

Authors:

???

Abstract:

An oviraptorid dinosaur Huanansaurus ganzhouensis, belonging to the derived oviraptorid dinosaur, was discovered from the Late Cretaceous deposits in Ganzhou, Jiangxi Province. Its unique skull characteristics provide a new insight into the craniofacial evolution of oviraptorosaurid dinosaurs, paleogeographical distribution and paleoecological environments. Zhenyuanlong suni from the Early Cretaceous Yixian Formation of western part of Liaoning Province is a large, short-armed, winged dromaeosaurid dinosaur. It provides the evidence of feather morphologies and distribution in a short-armed dromaeosaurid dinosaur. The discovery of Zhenyuanlong also provides important evidence for the study of the diversity, the origin of feathers and the flight of Liaoning dromaeosaurid dinosaurs. Orientognathus chaoyngensis is the first Late Jurassic pterosaur discovered in western Liaoning and it is the largest rhamphorhynchinae pterosaur. The discovery of Orientognathus not only fills the temporal gap between the Middle Jurassic and Early Cretaceous pterosaur faunas of China but also plays an important role in the understanding of radiation evolution of rhamphorhynchids from the Late Jurassic. The above-mentioned important discoveries play a key role in our understanding of the hot and difficult issues such as the evolution of oviraptorid dinosaurs, the feather evolution in dromaeosaurid dinosaurs and the origin of bird feathers. In particular, the Ganzhou Dinosaurian Fauna is named based on the discovery of Huanansaurus.

Dakotaraptor is a Chimera: Part of Maastrichtian Cretaceous Dromaeosaurid is a Piece of a Turtle

The furculae of the dromaeosaurid dinosaur Dakotaraptor steini are trionychid turtle entoplastra

Authors:

Arbour et al

Abstract:

Dakotaraptor steini is a recently described dromaeosaurid dinosaur from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of South Dakota. Included within the D. steini hypodigm are three elements originally identified as furculae, one of which was made part of the holotype specimen. We show that the elements described as D. steini ‘furculae’ are not theropod dinosaur furculae, but are rather trionychid turtle entoplastra referable to cf. Axestemys splendida. The hypodigm of D. steini should be adjusted accordingly.

Boreonykus certekorum: a new High-latitude Dromaeosaurid Theropod From Upper Campanian Cretaceous Alberta

A high-latitude dromaeosaurid, Boreonykus certekorum, gen. et sp. nov. (Theropoda), from the upper Campanian Wapiti Formation, west-central Alberta

Authors:

Bell et al

Abstract:

Dromaeosaurids were rare components of most Late Cretaceous terrestrial ecosystems and are poorly known from high palaeolatitudes. New dromaeosaurid material, including a frontal and associated postcranial elements, is described from a dense monodominant ceratopsid bonebed on Pipestone Creek, near the city of Grande Prairie (Unit 3, Wapiti Formation, upper Campanian), central-western Alberta, Canada. This stratigraphic interval is significant because it records a period of terrestrial deposition at a time when much of the western interior of Canada and the United States was inundated by the Bearpaw Sea. A phylogenetic analysis recovers Boreonykus certekorum, gen. et sp. nov., as a derived eudromaeosaur, possibly within Velociraptorinae. The identification of a new dromaeosaurid from the Wapiti Formation simultaneously helps fill an important gap in the record of late Campanian dromaeosaurids, bolsters support for a partly endemic fauna within the Wapiti Formation, and potentially adds to the North American record of a predominantly Asian Velociraptorinae.

Dakotaraptor is a Chimera, "Wishbone" is Part of a TURTLE

The furculae of the dromaeosaurid dinosaur Dakotaraptor steini are trionychid turtle entoplastra

Authors:

Arbour et al

Abstract:

Dakotaraptor steini is a recently described dromaeosaurid dinosaur from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of South Dakota. Included within the D. steini hypodigm are three elements originally identified as furculae: one which is part of the holotype specimen and two referred specimens. We show that the elements described as D. steini ‘furculae’ are not theropod dinosaur furculae, but rather trionychid turtle entoplastra. Given that the holotype 'furcula' is not referable to Dromaeosauridae and that the specimen is a disarticulated individual based on skeletal remains from a multitaxic bonebed, the holotype of Dakotaraptor steini is a chimera.

Dakotaraptor steini: a new Maastrichtian Cretaceous FEATHERED Giant Raptor

THE FIRST GIANT RAPTOR (THEROPODA: DROMAEOSAURIDAE) FROM THE HELL CREEK FORMATION

Authors:

DePalma et al

Abstract:

Most dromaeosaurids were small- to medium-sized cursorial, scansorial, and arboreal, sometimes volant predators, but a comparatively small percentage grew to gigantic proportions. Only two such giant “raptors” have been described from North America. Here, we describe a new giant dromaeosaurid, Dakotaraptor steini gen. et sp. nov., from the Hell Creek Formation of South Dakota. The discovery represents the first giant dromaeosaur from the Hell Creek Formation, and the most recent in the fossil record worldwide. A row of prominent ulnar papilli or “quill knobs” on the ulna is our first clear evidence for feather quills on a large dromaeosaurid forearm and impacts evolutionary reconstructions and functional morphology of such derived, typically flight-related features. The presence of this new predator expands our record of theropod diversity in latest Cretaceous Laramidia, and radically changes paleoecological reconstructions of the Hell Creek Formation

Itemirus: a Dromaeosaur From Turonian Cretaceous Uzbekistan

Dromaeosauridae (Dinosauria: Theropoda) from the Bissekty Formation (Upper Cretaceous: Turonian) of Uzbekistan and the phylogenetic position of Itemirus medullaris Kurzanov, 1976

Authors:

Sues et al

Abstract:

Skeletal remains of dromaeosaurid theropods are uncommon in the richly fossiliferous continental strata of the Upper Cretaceous (Turonian) Bissekty Formation of the Kyzylkum Desert in Uzbekistan. The phylogenetic position of the first published specimen, a partial braincase designated as the holotype of Itemirus medullaris Kurzanov, 1976, has long been contentious. Our examination of the specimen supports its attribution to Dromaeosauridae. Additional, mostly well-preserved dromaeosaurid skeletal remains from the Bissekty Formation include cranial bones, teeth, vertebrae, and some podial elements. They are tentatively referred to the same taxon, Itemirus medullaris, and establish the presence of dromaeosaurid paravians in present-day Central Asia during the Turonian.

Changyuraptor yangi: a new ‘Four-winged’ Microraptorine From Barremian Cretaceous China's Jehol Biota

A new raptorial dinosaur with exceptionally long feathering provides insights into dromaeosaurid flight performance

Authors:

Han et al

Abstract:

Microraptorines are a group of predatory dromaeosaurid theropod dinosaurs with aerodynamic capacity. These close relatives of birds are essential for testing hypotheses explaining the origin and early evolution of avian flight. Here we describe a new ‘four-winged’ microraptorine, Changyuraptor yangi, from the Early Cretaceous Jehol Biota of China. With tail feathers that are nearly 30 cm long, roughly 30% the length of the skeleton, the new fossil possesses the longest known feathers for any non-avian dinosaur. Furthermore, it is the largest theropod with long, pennaceous feathers attached to the lower hind limbs (that is, ‘hindwings’). The lengthy feathered tail of the new fossil provides insight into the flight performance of microraptorines and how they may have maintained aerial competency at larger body sizes. We demonstrate how the low-aspect-ratio tail of the new fossil would have acted as a pitch control structure reducing descent speed and thus playing a key role in landing.

Abelisaur and Dromaeosaur Teeth Found in Upper Cretaceous Brazil

Theropod teeth from the Adamantina Formation (Bauru Group, Upper Cretaceous), Monte Alto, São Paulo, Brazil

Authors:

Tavares et al

Abstract:

Theropod bone remains from the Bauru Group, Upper Cretaceous, Southeastern Brazil, are scarce and poorly preserved. Because of that much of the information about these dinosaurs mainly relies on isolated teeth. Here we report a set of theropod teeth found in association with several crocodylomorph teeth and a well-preserved and semi-articulated sauropod dinosaur from the Adamantina Formation deposits. The teeth were analyzed under both morphological and morphometric point of views and the results showed they correspond to the clades Abelisauridae and Dromaeosauridae. To date, and based on osteological evidence, abelisaurids are the most common theropod clade in Bauru Group deposits. Additionally, although deinonychosaur remains have also been described for this unit, some of the teeth reported here might represent the first evidence of Dromaeosauridae for the Bauru Group.

Acheroraptor temertyorum: a Velociraptor Cousin in the Maastrichtian Cretaceous Hell Creek Formation

A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America

Authors:

David C. Evans, Derek W. Larson and Philip J. Currie

Abstract:

Dromaeosaurids from the Maastrichtian of North America have a poor fossil record and are known largely from isolated teeth, which have typically been referred to taxa based on more complete material from earlier Campanian strata. An almost complete maxilla with well-preserved dentition and an associated dentary from the Hell Creek Formation of Montana are used to establish a new dromaeosaurid taxon in the latest Maastrichtian, immediately prior to the end-Cretaceous extinction event. Acheroraptor temertyorum gen. et sp. nov. is differentiated from other dromaeosaurids on the basis of a hypertrophied postantral wall that projects posteriorly into the antorbital fenestra, a maxillary fenestra positioned low in the antorbital fossa and directly posterior to the promaxillary fenestra, and distinctive dentition with marked apicobasal ridges. The new material allows a dromaeosaurid from the Maastrichtian of North America to be placed within a phylogenetic framework for the first time. Phylogenetic analysis suggests Acheroraptor is a velociraptorine that is more closely related to Asian dromaeosaurids, including Tsaagan and Velociraptor, than it is to Dromaeosaurus, Saurornitholestes, or any other taxon from North America. As part of the Lancian Tyrannosaurus–Triceratops fauna, A. temertyorum is the latest occurring dromaeosaurid. Its relationships and occurrence suggest a complex historical biogeographic scenario that involved multiple, bi-directional faunal interchanges between Asia and North America during the Late Cretaceous.