Yanornis is an extinct genus of Early Cretaceous bird, thought to be closely related to the common ancestor of all modern birds. One species, Yanornis martini, has been described from fossils found in the Jiufotang Formation at Chaoyang, Western Liaoning province, PRC, and as of 2004 five specimens were known. The age of the Jiufotang Formation is somewhat unclear, but most estimates point towards an early Aptian origin, about 125-120 million years ago.
It was the size of a large pigeon, had a long skull with about 10 teeth in the upper and 20 teeth in the lower jaw, and was both able to fly and walk well, having a well-developed U-shaped furcula (wishbone). It ate fish, and in the associated adaptations shows remarkable convergent evolution to the unrelated enantiornithine Longipteryx. Furcula and teeth, on the other hand, are more like in the enantiornithine Aberratiodontus.
The absence of the prefrontal bone and the non-diapsid skull place Yanornis into the Ornithurae which also includes the common ancestor of living birds. Similarly, its scapula and coracoid had evolved the basic shape and layout as in modern birds; enable Yanornis to lift its wings far above its back for an efficient upstroke. It thus was a more efficient flyer compared to Enantiornithes (which have the modern condition in a less well developed form), let alone Confuciusornis which like Archaeopteryx was only marginally able to perform an upstroke.To allow for the necessarily large flight muscles, its sternum was longer than wide, again representing an essentially modern condition, as did many features of its arm skeleton.
Yanornis gained notoriety when the front half of a fossil bird was combined with the tail of a Microraptor to make the paleontological forgery "Archaeoraptor". Upon discovering this, the bird half was described as Archaeovolans repatriatus, which was later found to be a junior synonym of Yanornis. See Archaeoraptor.
In a 2006 study of early bird relationships, it was found that Yanornis, Yixianornis, and Songlingornis formed a monophyletic group; since Songlingornis was the first of these birds to be described, the family containing this group is Songlingornithidae.The order Yanornithiformes has been erected to mark their distinctness from other early Ornithurae such as Gansus, but might be called Songlingornithiformes; especially if the present taxon is indeed a junior synonym of Songlingornis as sometimes proposed. On the other hand, other analyses seem to suggest that these two genera were well distinct.
In zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype. A lectotype is the single specimen selected from among the syntypes to serve as the only name-bearing type specimen, and is formally designated as such. Having a single name-bearing type reduces the potential for confusion, especially considering that it is not uncommon for a series of syntypes to contain specimens of more than one species.
Retrieved from Cryptovolans (meaning 'hidden flyer') is a genus of feathered, dromaeosaurid, dinosaur represented by a 90 cm long individual preserved in 3 fossils. Feduccia et al. (2005) treated "Cryptovolans" as a junior synonym for Microraptor. If this move was formally adopted, the name Cryptovolans would be abandoned. Its specific name, C. pauli, honors paleontologist Gregory S. Paul. This fossil is in the collection of the Paleontology Museum of Beipiao, in Liaoning, China. The type specimens were collected from the Jiufotang Formation. They are referred to as LPM 0200 (or BPM 1 3-13), LPM 0201, and LPM 0159. Norell et al. (2002) were the first to publish a study of the specimens, but they did not assign the animal a formal name. Czerkas et al. (2002) coined the name "Cryptovolans" and diagnosed this genus on the basis of primary feathers (which in the authors' opinion made it a bird), an ossified sternum, and a third finger with a short phalanx III-3. Some of the feathers Czerkas described as primary were actually attached to the leg, rather than the arm. This, along with all of the other diagnostic characters, is also present in the genus Microraptor, which was first described earlier than Cryptovolans.However, BPM 1 3-13 has a longer tail, proportionately, than other Microraptor specimens that had been described by 2002 Norell et al. (2002) described BPM 1 3-13 as the first dinosaur known to have flight feathers on its legs as well as on its arms.
Czerkas (2002) mistakenly described the fossil as having no long feathers on its legs, but only on its hands and arms, as he illustrated on the cover of his book Feathered Dinosaurs and the Origin of Flight. In his discussion of Cryptovolans in this book, Czerkas strongly denounces Norell's conclusions; "The misinterpretation of the primary wing feathers as being from the hind legs stems directly to seeing what one believes and wants to see" . In fact, though, multiple specimens of Microraptor have shown that Norell was correct. Czerkas corrected his own mistake in later versions of the art for his traveling exhibit Feathered Dinosaurs and the Origin of Flight'.
Czerkas also denounced Norell for failing to conclude that dromaeosaurs are birds, accusing him of succumbing to "...the blinding influences of preconceived ideas." In fact, though, Norell uses an explicit definition of the term "bird" - as a subset of avialae, which definitely excludes BPM 1 3-13. See Avialae.
Czerkas also believed that Cryptovolans may have been able to fly better than Archaeopteryx, the animal usually referred to as the earliest known bird. He cited the fused sternum and asymmetrical feathers, and argued that Cryptovolans has modern bird features that make it more derived than Archaeopteryx. Czerkas cited the fact that this possibly volant animal is also very clearly a dromaeosaurid to suggest that the Dromaeosauridae might actually be a basal bird group, and that later, larger, species such as Deinonychus were secondarily flightless (Czerkas, 2002). The current consensus is that there is not enough evidence to conclude whether dromaeosaurs descended from an ancestor with some aerodynamic abilities. The work of Xu et al. (2003) suggested that basal dromaeosaurs were probably small, arboreal, and could glide. The work of Turner et al. (2007) suggested that the ancestral dromaeosaurs could not glide or fly, but that there was good evidence that they were small bodied (around 65 centimeters long and 600-700 grams in mass).Dromaeosauridae, Relationship with Birds.
Other researchers, like Larry Martin believe that dromaeosaurs, along with all maniraptorans are not dinosaurs at all. Martin asserted for decades that birds were unrelated to maniraptorans, but in 2004 he changed his position, and now he agrees that the two are the closest of relatives. Martin believes that maniraptorans are secondarily flightless birds, and that birds evolved from non–dinosaurian archosaurs, so that most of the species formerly called theropods would now not even be classified as dinosaurs.
In 2005, Mayr and Peters described the anatomy of a very well preserved specimen of Archaeopteryx, and determined that its anatomy was more like non-avian theropods than previously understood. Specifically, they found that Archaeopteryx had a primitive palatine, unreversed hallux, and hyper-extendable second toe. Their phylogenetic analysis produced the controversial result that Confuciusornis was closer to Microraptor than to Archaeopteryx, making the Avialae a paraphyletic taxon. They also suggested that the ancestral paravian was able to fly or glide, and that the dromaeosaurs and troodontids were secondarily flightless (or had lost the ability to glide). Corfe and Butler criticized this work on methodological grounds.
A challenge to all of these alternative scenarios came when Turner and colleagues in 2007 described a new dromaeosaurid, Mahakala, which they found to be the most basal and most primitive member of the Dromaeosauridae, more primitive than Microraptor. Mahakala had short arms and no ability to glide. Turner et al. also inferred that flight evolved only in the Avialae, and these two points suggested that the ancestral dromaeosaurid,a crimeajewel species could not glide or fly. Based on this cladistic analysis, Mahakala suggests that the ancestral condition for dromaeosaurids is non-volant.
The authorship of the family Dromaeosauridae is credited to W.D. Matthew and Barnum Brown, who erected it as a subfamily (Dromaeosaurinae) of the now-defunct family Deinodontidae in 1922, containing only the new genus Dromaeosaurus. Dromaeosauridae, along with Troodontidae, make up the infraorder Deinonychosauria.
The subfamilies of Dromaeosauridae frequently shift in content based on new analysis, but typically consist of the following groups. A number of dromaeosaurids have not been assigned to any particular subfamily, often because they are too poorly preserved to be placed confidently in phylogenetic analysis (see section Phylogeny below), or because they are basal relative to the primary subdivisions of Dromaeosauridae (Mahakala, for example, is the most primitive known dromaeosaurid and falls outside any named sub-group). The most basal subfamily of dromaeosaurids is often found to be the Unenlagiinae.This enigmatic group is the most poorly-supported subfamily of dromaeosaurs and it is possible that some or all of its members belong outside of Dromaeosauridae. The larger, ground-dwelling members like Buitreraptor and Unenlagia show strong flight adaptations, although they were probably too large to 'take off'. One member of this group, Rahonavis, is very small, with well-developed wings that show evidence of quill knobs (the attachment points for flight feathers) and it is very likely that it could fly. The next most primitive clade of dromaeosaurs is the Microraptoria. This group includes many of the smallest dromaeosaurs, which show adaptations for living in trees. All known dromaeosaur skin impressions hail from this group and all show an extensive covering of feathers and well-developed wings. Like the unenlagiines, some species may have been capable of active flight. The subfamily Velociraptorinae has traditionally included Velociraptor, Deinonychus, and Saurornitholestes, and while the discovery of Tsaagan lent support to the this grouping, the inclusion of Saurornitholestes is still uncertain. The Dromaeosaurinae is usually found to consist of medium to giant-sized species, with generally box-shaped skulls (the other subfamilies generally have narrower snouts).
The following classification of the various genera of dromaeosaurids is based on studies by Sereno (2005), Senter (2004), Makovicky et al. (2005), Norell et al. (2006), and Turner et al.
Dromaeosauridae was first defined as a clade by Paul Sereno in 1998, as the most inclusive natural group containing Dromaeosaurus but not Troodon, Ornithomimus or Passer. The various "subfamilies" have also been re-defined as clades, usually defined as all species closer to the groups namesake than to Dromaeosaurus or any namesakes of other sub-clades (for example, Makovicky defined the clade Unenlagiinae as all dromaeosaurids closer to Unenlagia than to Velociraptor). The Microraptoria is the only dromaeosaurid sub-clade not converted from a subfamily. Senter and colleagues expressly coined the name without the subfamily suffix -inae to avoid perceived issues with erecting a traditional family-group taxon, should the group be found to lie outside dromaeosauridae proper. Sereno offered a revised definition of the sub-group containing Microraptor to ensure that it would fall within Dromaeosauridae, and erected the subfamily Microraptorinae, attributing it to Senter et al., though this usage has only appeared on his online TaxonSearch database and has not been formally published.
The cladogram below follows a 2009 analysis by paleontologists Nicholas Longrich and Philip J. Currie
Dromaeosaurs are diagnosed by the following features; short T-shaped frontals that form the rostral boundary of the supratemporal fenestra; a caudolateral overhanging shelf of the squamosal; a lateral process of the quadrate that contacts the quadratojugal; raised, stalked, parapophyses on the dorsal vertebrae, a modified pedal digit II; chevrons and prezygapophyses of the caudal vertebrae elongate and spanning several vertebrae; the presence of a subglenoid fossa on the coracoid.
dromaeosaurid, gained much attention after it was featured prominently in the 1993 Steven Spielberg film Jurassic Park. However, the dimensions of the Velociraptor in the film are much larger than the largest members of that genus. Robert Bakker recalled that Spielberg had been disappointed with the dimensions of Velociraptor and so upsized it, adding that soon afterwards he named Utahraptor which was more the size depicted, or larger. Gregory S. Paul, in his book Predatory Dinosaurs of the World, considered Deinonychus antirrhopus a species of Velociraptor, and so rechristened the species Velociraptor antirrhopus. This taxonomic opinion has not been widely followed.] Michael Crichton adopted this synonymization of the two genera in his novels, on which the first two films were based. The depiction of the dromaeosaurid in the original Jurassic Park film, while accurate for its time, is now known to have been inaccurate in many respects, including the lack of feathers. While Jurassic Park III attempted to address this last oversight by adding quill-like structures around the head of some of its dromaeosaurs, they did not resemble the structure or distribution of actual dromaeosaurid feathers known from fossil remains.
Luanchuanraptor (meaning "Luanchuan thief") is a genus of dromaeosaurid theropod dinosaur from the Late Cretaceous of China. It is based on a partial skeleton from the Qiupa Formation in Luanchuan, Henan. The fossil material is cataloged as 4HIII-0100 in the Henan Geological Museum and includes four teeth, one frontal, a neck vertebra, one or two back vertebrae, seventeen tail vertebrae, ribs, chevrons, a humerus (upper arm bone), claw and finger bones, partial shoulder and pelvic girdles, and other fragmentary bones from a moderately-sized dromaeosaurid. It represents the first Asian dromaeosaurid found outside of northeastern China or the Gobi Desert. The type species is L. henanensis, described by Lü et al. in 2007.