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A New Enantiornitine Bird with Four Long Rectrices from the Early Cretaceous of Northern Hebei, China

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Abstract

Paraprotopteryx gracilis, a new enantiornithine bird from the Early Cretaceous Yixian Formation in Fengning, northern Hebei Province is erected, based on the following characters: Y-shaped furcula with a long hypocleidum and a much narrow interclavicular angle, and the morphology of the sternum are different from other enantiornithines. Additionally, alular digit bearing the biggest manual claw extends distally to the distal end of the major metacarpal; the minor metacarpal is slender than the major metacarpal. Carpometacarpus only fused proximally; astragalus and calcaneum partially fused to one another but unfused to the tibia. This is the first record of Mesozoic birds in having four long rectrices, which may represent morphologically a secondary sexual character, an intermediate stage from elongated scale to branched feather, and possess functional advantage in supplementing the lifting surface to compensate the unskilled flight.

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... Because most fossils are preserved in two dimensions, the detailed anatomy of these tail feathers still remains in debate. They have been variously suggested as representing an scale-like structure intermediate in morphology between the reptilian and bird integuments, a modified pennaceous feather, or a unique type of primitive feather 2,3,[8][9][10][11][12] . ...
... Since the discovery of elongate rectricial feathers in Confuciusornis, authors mostly agree that such elongate structures may be sexually dimorphic and associated with sexual display, species recognition or visual communication 2,5,6,10,23,38 . The presence of a colour pattern on the tail base of UFRJ-DG 031 Av reinforces these interpretations. ...
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The fossil record of birds in the Mesozoic of Gondwana is mostly based on isolated and often poorly preserved specimens, none of which has preserved details on feather anatomy. We provide the description of a fossil bird represented by a skeleton with feathers from the Early Cretaceous of Gondwana (NE Brazil). The specimen sheds light on the homology and 3D structure of the rachis-dominated feathers, previously known from two-dimensional slabs. The rectrices exhibit a row of rounded spots, probably corresponding to some original colour pattern. The specimen supports the identification of the feather scapus as the rachis, which is notably robust and elliptical in cross-section. In spite of its juvenile nature, the tail plumage resembles the feathering of adult individuals of modern birds. Documentation of rachis-dominated tail in South American enantiornithines broadens the paleobiogeographic distribution of basal birds with this tail feather morphotype, up to now only reported from China.
... The radiale, as in other enantiornithines, e.g., Longipteryx, Eocathayornis, and CAGS-IG-02-0901, is much smaller than the ulnare Zhou, 2002;You et al., 2005); these two carpals are of similar sizes in Pengornis and the radiale is larger in Confuciusornis (Chiappe et al., 1999;Zhou et al., 2008). The radiale is square-shaped as in Cathayornis, Eocathayornis, and Paraprotopteryx (Zhou, 2002;Zhou and Hou, 2002;Zheng et al., 2007). ...
... The horizon was later regarded by Jin et al., (2008) (Zhang and Zhou, 2000;Zheng et al., 2007) or the Dabeigou Formation of northern Hebei Province (Zhou and Zhang, 2006a); however, recent litho-and biostratigraphic strata correlations haves indicated that it belongs to the Dadianzi Formation, and is 130.7 Ma old (He et al., 2006;Jin et al., 2008;He et al., 2006). ...
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We describe a new enantiornithine bird, Fortunguavis xiaotaizicus, gen. et sp. nov, from the Lower Cretaceous lacustrine deposits of the Jiufotang Formation in northeastern China. The new taxon has a strongly dorsoventrally bowed furcula indicating that enantiornithines evolved furcular morphologies in parallel with ornithuromorphs. The new specimen has very robust limbs compared with other enantiornithines and has an unique foot morphology with metatarsal II much shorter than metatarsal IV, robust pedal digits, and strongly recurved pedal unguals. Although recurved unguals characterize Enantiornithes, the extreme curvature present in Fortunguavis suggests scansorial specialization in this species. These features hint at a unique ecology for this taxon and further increase the known diversity of body plans in Early Cretaceous enantiornithines.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at http://www.tandfonline.com/UJVP.
... Feathers also show some variation in their overall lengths with respect to body-size (e.g., femur: rectrix ratios for Dapingfangornis sentisorhinus: 0.145, Paraprotopteryx gracilis: 0.17)-however, the extent to which variation is affected by molting is unknown. The enantiornithine, Paraprotopteryx gracilis preserves four rectrices of this morphotype [52], suggesting further diversity. However, the different color of the laterally preserved two feathers (compared to the medial pair) may indicate that these structures have been artificially added to the slab. ...
... The rachis-dominated feathers of some basal birds have been suggested to represent (I) an intermediate morphology providing evidence that pennaceous feathers evolved from elongated scales [40,52], (II) a type of modified pennaceous feather [42], or (III) a completely new type of primitive feather [4]. The presence of modern flight feathers in the non-avian dinosaur Microraptor gui and the basalmost bird Archaeopteryx lithographica, and the absence of a specimen with elongate scale-like integument largely covering the body makes the first hypothesis weak given that these supposedly intermediate structures are absent in taxa that are more basal than those that possess them. ...
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At least two lineages of Mesozoic birds are known to have possessed a distinct feather morphotype for which there is no neornithine (modern) equivalent. The early stepwise evolution of apparently modern feathers occurred within Maniraptora, basal to the avian transition, with asymmetrical pennaceous feathers suited for flight present in the most basal recognized avian, Archaeopteryx lithographica. The number of extinct primitive feather morphotypes recognized among non-avian dinosaurs continues to increase with new discoveries; some of these resemble feathers present in basal birds. As a result, feathers between phylogenetically widely separated taxa have been described as homologous. Here we examine the extinct feather morphotypes recognized within Aves and compare these structures with those found in non-avian dinosaurs. We conclude that the "rachis dominated" tail feathers of Confuciusornis sanctus and some enantiornithines are not equivalent to the "proximally ribbon-like" pennaceous feathers of the juvenile oviraptorosaur Similicaudipteryx yixianensis. Close morphological analysis of these unusual rectrices in basal birds supports the interpretation that they are modified pennaceous feathers. Because this feather morphotype is not seen in living birds, we build on current understanding of modern feather molecular morphogenesis to suggest a hypothetical molecular developmental model for the formation of the rachis dominated feathers of extinct basal birds.
... Other specimens (e.g., Eoenantiornis buhleri Hou et al., 1999, IVPP V11537, STM29-8) possess no rectrices, only morphologically simple body coverts surrounding the pygostyle (O'Connor, 2009;O'Connor et al., 2012). One taxon, (Paraprotopteryx gracilis STMV001, (Zheng et al., 2007) reportedly possesses four rachis-dominated 'racketplumes,' and the holotype of Shanweiniao cooperorum O'Connor et al., 2009 (DNHM D1878 1/2), preserves impressions of portions of at least four closely arranged tail feathers that may potentially have formed an aerodynamic surface . In contrast, several Jehol ornithuromorphs (e.g., Hongshanornis longicresta Zhou and Zhang, 2005, Piscivoravis lii Zhou et al., 2013, Yanornis martini Zhou and Zhang, 2001Zhou and Zhang, 2005;Clarke et al., 2006;Zhou et al., 2013) preserve large, round tails formed by a fan of 6-10 rectrices, and one taxon (Schizooura lii) has a forked tail (Zhou et al., 2012), all considered aerodynamic morphologies. ...
... Alternatively, specimens that clearly lack elongate feathers could conceivably represent molting individuals. Although there are not yet enough known specimens of any one taxon to definitively evaluate this hypothesis, these feathers are similarly interpreted as sexually dimorphic in the enantiornithine species in which they occur (Zheng et al., 2007). In the single Confuciusornis specimen and in the one indeterminate enantiornithine in which the gender can be confidently identified as female (due to the preservation of medullary bone and ovarian follicles, respectively), elongate rectrices are clearly absent, supporting the hypothesis that these feathers are only present in males of these species (Chinsamy et al., 2013;. ...
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We provide a detailed description of a well-preserved enantiornithine specimen (GSGM-05-CM-004) from the Lower Cretaceous (Aptian) Xiagou Formation of northwestern Gansu Province, China, for which we erect the new taxon Feitianius paradisi, gen. et sp. nov. This specimen has a distinctive pelvic morphology and can be further distinguished from all other Mesozoic birds by a unique caudal plumage formed by multiple rectricial morphotypes. This newly documented tail morphology reveals a previously unrecognized level of complexity in the plumage of basal birds. This complex tail-feather morphology has a parallel in extant sexually dimorphic birds in which the males have the most altered tails; thus, we identify this specimen as male. Ornamental tail morphologies, such as the novel tail plumage described here, dominate Enantiornithes. This reinforces hypotheses that sexual selection was a major driving force in the evolution of basal bird plumage. http://zoobank.org/urn:lsid:zoobank.org:pub:8BEF4422-58C5-487B-B76A-51C5855CF87B SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: O’Connor, J. K., D.-Q. Li, M. C. Lamanna, M. Wang, J. D. Harris, J. Atterholt, and H.-L. You. 2015. A new Early Cretaceous enantiornithine (Aves, Ornithothoraces) from northwestern China with elaborate tail ornamentation. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1054035. 2015
... Shanweiniao preserves an elongate tail composed of at least four closely aligned rectrices, a previously unrecorded morphology . The typical enantiornithine tail morphology consists of short coverts covering the pygostyle (Clarke et al., 2006), however, several species have been described possessing elongate streamer-like tail feathers; Protopteryx fengningensis (Zhang and Zhou, 2000) and Dapingfangornis sentisorhinus (Li et al., 2006) possess paired tail feathers, similar to those preserved in some specimens of Confuciusornis (Chiappe et al., 1999) and the recently named Paraprotopteryx gracilis has been described with four (Zheng et al., 2007). The elongate rectrices ...
... preserved in Paraprotopteryx, Protopteryx, Dapingfangornis, and Confuciusornis have often been interpreted as display structures, a conclusion that is supported here due to their length, splay and morphology (Chiappe et al., 1999; Zhang and Zhou, 2000; Li et al., 2006; Zheng et al., 2007). The distal ends of the feathers in these taxa are preserved widely spaced, not closely aligned along their lengths in such a way as to create a surface capable of acting as an airfoil and thus generate any aerodynamic benefit. ...
Article
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A new species of enantiornithine bird from the Lower Cretaceous Yixian Formation of northeastern China is reported. The new taxon, Shanweiniao cooperorum, possesses several enantiornithine synapomorphies as well as the elongate rostral morphology (rostrum equal to or exceeding 60% the total length of the skull) of the Chinese early Cretaceous enantiornithines, Longipteryx chaoyangensis and Longirostravis hani. The discovery of this new specimen highlights the existence of a diverse clade of trophically specialized enantiornithines, Longipterygidae, for which we present phylogenetic support in a new comprehensive cladistic analysis of Mesozoic birds. Shanweiniao provides new information on the anatomy of longipterygids, and preserves a rectricial morphology previously unknown to enantiornithines, with at least four tail feathers closely arranged. This supports the hypothesis that enantiornithines were strong fliers and adds to the diversity of known tail morphologies of these Cretaceous birds.
... Enantiornithes preserves the greatest diversity of rectricial morphologies recognized for any clade of Cretaceous bird [16][17][18][19], All scale bars represent 5 mm. Anatomical abbreviations: 1-8, sacral vertebrae; ac, acromion process; at, atlas; cp, costal process; cr, carotid process; ct, carpal trochlea; de, dentary; gl, glenoid facet; il, ilium; l, left; ma, major metacarpal; mi, minor metacarpal; r, right; sc, scleral ring; sp, spinous process. ...
... Narrow spaces are visible between some of the feathers (see Figure 7 in [20]), whereas no intervening space is preserved between adjacent rectrices in any other rectricial fan from the Jehol, including STM29-11. We consider it more likely that Shanweiniao had four (or potentially more) rachis-dominated feathers, similar to Paraprotopteryx [18]. Tail morphology is otherwise unknown among longipterygids, although the holotype of Longipteryx preserves a clear absence of elongate rectrices [32]. ...
Article
The most basal avians Archaeopteryx and Jeholornis have elongate reptilian tails. However, all other birds (Pygostylia) have an abbreviated tail that ends in a fused element called the pygostyle. In extant birds, this is typically associated with a fleshy structure called the rectricial bulb that secures the tail feathers (rectrices) [1]. The bulbi rectricium muscle controls the spread of the rectrices during flight. This ability to manipulate tail shape greatly increases flight function [2, 3]. The Jehol avifauna preserves the earliest known pygostylians and a diversity of rectrices. However, no fossil directly elucidates this important skeletal transition. Differences in plumage and pygostyle morphology between clades of Early Cretaceous birds led to the hypothesis that rectricial bulbs co-evolved with the plough-shaped pygostyle of the Ornithuromorpha [4]. A newly discovered pengornithid, Chiappeavis magnapremaxillo gen. et sp. nov., preserves strong evidence that enantiornithines possessed aerodynamic rectricial fans. The consistent co-occurrence of short pygostyle morphology with clear aerodynamic tail fans in the Ornithuromorpha, the Sapeornithiformes, and now the Pengornithidae strongly supports inferences that these features co-evolved with the rectricial bulbs as a "rectricial complex." Most parsimoniously, rectricial bulbs are plesiomorphic to Pygostylia and were lost in confuciusornithiforms and some enantiornithines, although morphological differences suggest three independent origins.
... Bohaiornis LPM B00167, Parapengornis IVPP V 18687) (Zhang and Zhou, 2000;Li et al., 2006;Hu et al., 2011;Hu et al., 2015). Paraprotopteryx (STM V 001) preserves two pairs of feathers (Zheng et al., 2007). These feathers vary with regards to the extent of the pennaceous vane, being fully pennaceous in Parapengornis and Eopengornis and distally restricted in all other specimens in which preservation is clear (Dapingfangornis, GSGM-07-CM-001, Paraprotopteryx STM V 001). ...
... Other confuciusornithiform specimens additionally preserve a pair of elongate rachis-dominated rectrices interpreted as male-specific ornaments . Consistent with similarities in pygostyle morphology, similar ornamental rachis-dominated rectrices are also present in some enantiornithines (e.g., Protopteryx, Paraprotopteryx, Dapingfangornis) (Zhang and Zhou, 2000;Li et al., 2006;Zheng et al., 2007). The only exception is the pengornithid Chiappeavis (STM 29-11), which has recently been described with a "tail fan" consisting of approximately eight overlapping rectrices (O'Connor et al., 2016). ...
Article
Full-text available
The transformation from a long reptilian tail to a shortened tail ending in a pygostyle and accompanied by aerodynamic fanning rectrices is one of the most remarkable adaptations of early avian evolution. However, no fossils directly capture this transition, and information regarding the structural morphology and the early evolution of the pygostyle in Mesozoic birds and their integuments is relatively limited. Here we provide a review of the pygostyle morphology of Early Cretaceous birds with comparison to the structure in living birds. This study emphasizes the convergent evolution of distally co-ossified caudal vertebrae in non-avian maniraptorans and early birds. There further exist distinct differences in pygostyle morphology between Sapeornithiformes, Confuciusornithiformes, Enantiornithes, and Ornithuromorpha. The morphology of the pygostyle and rectrices in early ornithuromorphs appear similar to that of extant birds, whereas the pygostyle in more primitive birds does not appear morphologically capable of supporting the rectricial bulbs and musculature necessary to control an aerodynamic fan-shaped tail. The rectricial bulbs and rectricial fan appear to have coevolved with the plough-shaped pygostyle early in the evolution of the Ornithuromorpha. This study also shows that the confuciusornithiform pygostyle was more similar to that of enantiornithines than previously recognized, consistent with the presence of nearly identical ornamental tail feathers in both groups.
... The Jiufotang Formation has produced such enantiornithine taxa as Sinornis santensis (Sereno & Rao, 1992;Zhou, Jin & Zhang, 1992;Zhou, 1995a;Sereno, Rao & Li, 2002), Bolouchia zhengi (Zhou, 1995b), Longipteryx chaoyangensis , Eocathayornis walkeri (Zhou, 2002), Dapingfangornis sentisorhinus , Alethoalaornis agitornis , Pengornis houi (Zhou, Clarke & Zhang, 2008), and Rapaxavis pani (Morschhauser et al., 2009). The Yixian Formation, although most famous for its abundant specimens of the basal pygostylian Confuciusornis sanctus (Hou et al., 1995), has also yielded a number of enantiornithines, including Eoenantiornis buhleri , Longirostravis hani , Vescornis hebeiensis (Zhang, Ericson & Zhou, 2004), Dalingheornis liweii , Paraprotopteryx gracilis (Zheng, Zhang & Hou, 2007), and Shanweiniao cooperorum (O'Connor et al., 2009). Enantiornithine specimens from the Jehol Group, although frequently consisting of complete or nearly complete skeletons, are typically poorly preserved and crushed flat, often with bones broken between a slab and a counterslab. ...
... In Qiliania, the ascending process of the astragalus is firmly co-ossified with the tibia, contrasting with the condition reported in Dalingheornis liweii , Iberomesornis (Sanz & Bonaparte, 1992;Sanz et al., 2002;contra Sereno, 2000), Longipteryx, Paraprotopteryx gracilis (Zheng et al., 2007), Protopteryx, Shenqiornis, Vescornis, GMV-2158, and GMV-2159, where the tibia and proximal tarsals are said to be unfused (this latter morphology may well be a result of the ontogenetic immaturity of these forms; see Chiappe et al., 2007). Nevertheless, in Qiliania, the margins of the ascending process may still be discerned, as in Gobipteryx, Na. eos, and Mechin collection 606, but not Concornis. ...
Article
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In recent years, the Lower Cretaceous (Aptian) Xiagou Formation has yielded approximately 100 avian partial skeletons, many with soft-tissue traces, from sites in the Changma Basin of Gansu Province, north-western China. The most abundant taxon amongst these is the ornithuromorph Gansus yumenensis, but enantiornithines have also been identified in the sample. Here we describe two incomplete, semi-articulated appendicular skeletons, the first consisting of a partial left pelvic girdle and complete pelvic limb, and the second comprised of a nearly complete right pelvic limb. Both specimens bear characteristics diagnostic of Enantiornithes, and are referred to a new taxon, Qiliania graffinigen. et sp. nov. The exceptional, three-dimensional preservation of these specimens (compared to the crushed, nearly two-dimensional condition of most other Early Cretaceous avian fossils) reveals new information regarding enantiornithine anatomy, evolution, and diversity. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162, 201–219.
... Many specimens preserve a single pair of elongate rachis-dominated tail feathers (e.g., Protopteryx IVPP V 11665, Dapingfangornis LPM 00039, Bohaiornis LPM B00167, Parapengornis IVPP V 18687) (Zhang and Zhou, 2000;Li et al., 2006;Hu et al., 2011;Hu et al., 2015). Paraprotopteryx (STM V 001) preserves two pairs of feathers (Zheng et al., 2007). These feathers vary with regards to the extent of the pennaceous vane, being fully pennaceous in Parapengornis and Eopengornis and distally restricted in all other specimens in which preservation is clear (Dapingfangornis, GSGM-07-CM-001, Paraprotopteryx STM V 001). ...
... Other confuciusornithiform specimens additionally preserve a pair of elongate rachis-dominated rectrices interpreted as male-specific ornaments . Consistent with similarities in pygostyle morphology, similar ornamental rachis-dominated rectrices are also present in some enantiornithines (e.g., Protopteryx, Paraprotopteryx, Dapingfangornis) (Zhang and Zhou, 2000;Zheng et al., 2007;Li et al., 2006). The only exception is the pengornithid Chiappeavis (STM 29-11), which has recently been described with a "tail fan" consisting of approximately eight overlapping rectrices (O'Connor et al., 2016). ...
Article
Full-text available
The transformation from a long reptilian tail to a shortened tail ending in a pygostyle and accompanied by aerodynamic fanning rectrices is one of the most remarkable adaptations of early avian evolution. However, no fossils directly capture this transition, and information regarding the structural morphology and the early evolution of the pygostyle in Mesozoic birds and their integuments is relatively limited. Here we provide a review of the pygostyle morphology of Early Cretaceous birds with comparison to the structure in living birds. This study emphasizes the convergent evolution of distally co-ossified caudal vertebrae in non-avian maniraptorans and early birds. There further exist distinct differences in pygostyle morphology between Sapeornithiformes, Confuciusornithiformes, Enantiornithes, and Ornithuromorpha. The morphology of the pygostyle and rectrices in early ornithuromorphs appear similar to that of extant birds, whereas the pygostyle in more primitive birds does not appear morphologically capable of supporting the rectricial bulbs and musculature necessary to control an aerodynamic fan-shaped tail. The rectricial bulbs and rectricial fan appear to have coevolved with the plough-shaped pygostyle early in the evolution of the Ornithuromorpha. This study also shows that the confuciusornithiform pygostyle was more similar to that of enantiornithines than previously recognized, consistent with the presence of nearly identical ornamental tail feathers in both groups.
... observ.) and the evolution of additional pairs of racket-plumes (Zheng, Zhang & Hou, 2007) further supports interpretation of these feathers as ornaments and suggests that increased ornamental function evolved in some enantiornithines. ...
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.
... Mei was first described on the basis of an exquisitelypreserved skeleton with a bird-like sleeping posture, which is arguably the most complete Early Cretaceous troodontid specimen known (Xu and Norell, 2004;Pan et al., 2013). Sinusonasus, Daliansaurus, and Liaoningvenator all have a similar size as Sinovenator, and each of them were reported from a single, near com- Hou et al., 1995Hou et al., , 1996Hou et al., , 1997bHou et al., , 1999aHou et al., , 1999bHou et al., , 2004Hou, 1996Hou, , 1997bChiappe et al., 1999Chiappe et al., , 2007Chiappe et al., , 2014Chiappe et al., , 2019bJi et al., 1999Ji et al., , 2002aJi et al., , 2002bZhang et al., 2006Zhang et al., , 2009Zhou and Zhang, 2005, 2006bGao et al., 2008Gao et al., , 2012O'Connor et al., 2009O'Connor et al., , 2011aO'Connor et al., , 2013O'Connor et al., , 2016cWang et al., 2013dWang et al., , 2013e, 2019c;Zheng et al., 2007Zheng et al., , 2013Zheng et al., , 2014 Dames, 1884;Heller, 1959;Wellnhofer, 1974Wellnhofer, , 1988Wellnhofer, , 1993Wellnhofer, , 2009Mayr et al., 2005;Wellnhofer and Marsh, 1872Marsh, , 1877Marsh, , 1880Martin and Tate, 1976;Martin, 1984;Clarke, 2004;Bell and Chiappe, 2015;Field et al., 2018b Belly River Group Case et al., 2007;Turner et al., 2012;Ely and Case, 2019;Cordes-Person, 2020 ...
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An unabated surge of new and important discoveries continues to transform knowledge of pen-naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes progress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaurians are bizarre, nonparavian pennaraptorans first discovered in North America and Mongolia within Late Cretaceous rocks in the early 20th century. We now know that oviraptorosaurians also occupied the Early Cretaceous and their unquestionable fossil record is currently limited to Laurasia. Early Cretaceous material from China preserves feathers and other soft tissues and ingested remains including gastroliths and other stomach contents, while brooding specimens and age-structured, single-species accumulations from China and Mongolia provide spectacular behavioral insights. Less specialized early oviraptorosaurians like Incisivosaurus and Microvenator remain rare, and ancestral forms expected in the Late Jurassic are yet to be discovered, although some authors have suggested Epidexipteryx and possibly other scansoriopterygids may represent early-diverging oviraptorosaurians. Long-armed scansoriopterygids from the Middle-Late Jurassic of Laurasia are either early-diverging oviraptorosaurians or paravians, and some have considered them to be early-diverging avialans. Known from five (or possibly six) feathered specimens from China, only two mature individuals exist, representing these taxa. These taxa, Yi and Ambopteryx, preserve stylopod-supported wing membranes that are the only known alternative to the feathered, muscular wings that had been exclusively associated with dinosaurian flight. Thus, scansoriopterygid specimens-particularly those preserving soft tissue-remain a key priority for future specimen collection. Dromaeosaurids and troodontids were first discovered in North America and Mongolia in Late Cretaceous rocks. More recent discoveries show that these animals originated in the Late Jurassic, were strikingly feathered, lived across diverse climes and environments, and at least in the case of dromaeosaurids, attained a global distribution and the potential for aerial locomotion at small size.
... Shenqiornis is clearly distinct from Protopteryx, Paraprotopteryx, Vescornis and Jibeinia, other taxa from Fengning, Hebei Province, China, as well as from all other described enantiornithines (Hou, 1997 ;Zheng et al., 2007 ). The taxon differs from the other Hebei enantiornithines in its overall larger size, more robust skull with large teeth, and proportionately short tarsometatarsus. ...
Article
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: 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.
... Only two types of feathered tails—fan-shaped and forked—have been reported for basal ornithuromorphs (Zhou & Zhang, 2001; Clarke, Zhou & Zhang, 2006; Zhou, Zhou & O’Connor, 2012; Zhou, Zhou & O’Connor, 2013a). Such limited diversity contrasts with what is known for their sister-group, the Enantiornithes, in which a larger number of tail morphologies (including one inferred to be aerodynamic; O’Connor et al., 2009) are known (Zhang & Zhou, 2000; Zheng, Zhang & Hou, 2007; O’Connor, Gao & Chiappe, 2010; O’Connor et al., 2012). ...
Article
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The discovery of Hongshanornis longicresta, a small ornithuromorph bird with unusually long hindlimb proportions, was followed by the discovery of two closely related species, Longicrusavis houi and Parahongshanornis chaoyangensis. Together forming the Hongshanornithidae, these species reveal important information about the early diversity and morphological specialization of ornithuromorphs, the clade that contains all living birds. Here we report on a new specimen (DNHM D2945/6) referable to Hongshanornis longicresta that contributes significant information to better understand the morphology, trophic ecology, and aerodynamics of this species, as well as the taxonomy of the Hongshanornithidae. Most notable are the well-preserved wings and feathered tail of DNHM D2945/6, which afford an accurate reconstruction of aerodynamic parameters indicating that as early as 125 million years ago, basal ornithuromorphs had evolved aerodynamic surfaces comparable in size and design to those of many modern birds, and flight modes alike to those of some small living birds.
... Several taxa (e. g. Protopteryx, Dapingfangornis, Paraprotopteryx) developed streamer-like feathers that may have played a sexual role (Zhang & Zhou, 2000;Li et al., 2006;Zheng et al., 2007), and at least one taxon evolved a fan-like tail morphology capable of generating substantial lift (Gatesy & Dial, 1996;O'Connor et al., 2009). The advanced features of the flight apparatus -the triosseal foramen, sternal keel, modern proportions of the wing, compact hand, and alula -suggest that these birds were capable of well-controlled and active flapping flight, however, future studies will be necessary to clarify how the anatomical differences between enantiornithines and modern birds affected the flight performance of this extinct clade. ...
... holotype (IVPP V 17964) The white arrows indicate five pennaceous feathers, which we interpret as leg feathers (see text) 52卷 古 脊 椎 动 物 学 报 the bone, although the distal ends of three of the feathers curve towards the pygostyle. In some enantiornithines from the Jehol Biota, the tail coverts radiate from the pygostyle and form a large acute angle with the shaft Zheng et al., 2007;Zheng et al., 2013b); besides, two long rectrices are preserved in the Bohaiornis holotype, which are close to the humeral length and substantially longer than these feathers in Longusunguis (Hu et al., 2011), leading us to suggest that the feathers preserved in the present specimen are more likely to be leg feathers, than rectrices. This interpretation is consistent with the fact that these feathers, when traced proximally, end adjacent to the surface of the tibial shaft. ...
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Two new enantiornithine birds, Parabohaiornis martini gen. et sp. nov., and Longusunguis kurochkini gen. et sp. nov., are reported here based on three nearly complete skeletons from the Lower Cretaceous lacustrine deposits of the Jiufotang Formation in Liaoning, northeastern China. The two new species share several unique features with Bohaiornis , Shenqiornis , Sulcavis and Zhouornis , including a robust rostrum with robust, subconical teeth, furcula with blunt omal expansions, sternal trabeculae caudolaterally directed, short and stout tarsometatarsus with hypertrophied ungual on digit Ⅲ . A close relationship among the two new species and four previously described taxa is confi rmed by a comprehensive phylogenetic analysis, leading us to erect Bohaiornithidae fam. nov. With six known taxa, Bohaiornithidae is the most diverse recognized enantiornithine family. The robust morphology of the rostrum and foot suggests bohaiornithids occupied a specialized ecological niche compared to other Early Cretaceous enantiornithines.
... Zhang et al., 2001F. Zhang et al., , 2004Sereno et al., 2002;Zheng et al., 2007;Morschhauser et al., 2009;O'Connor et al., 2009). * = estimated. ...
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ABSTRACT A new Late Cretaceous avian taxon, Parvavis chuxiongensis, gen. et sp. nov., is reported here based on an incomplete skeleton from Upper Cretaceous lake deposits in Yunnan Province, southern China. A phylogenetic analysis of 32 taxa and 242 morphological characters resulted in three most parsimonious trees, the strict consensus tree of which places Parvavis chuxiongensis within Enantiornithes. Histological study shows that the bones of Parvavis were composed of parallel-fibered bone tissue without lines of arrested growth, and indicated that growth rate had slowed but had not stopped at any stage prior to death. The bones also lack the rough surface texture seen in juvenile birds. Therefore, the new bird was probably close to adult body size at the time of death. However, the specimen is surprisingly small, highlighting the wide range of body sizes in Upper Cretaceous enantiornithines. The new specimen also represents both the first known bird from the Upper Cretaceous of China and the first Mesozoic bird from the south of China, and thus extends the temporal and geographic range of Mesozoic birds in China. SUPPLEMENTAL DATA?Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
... One example of such morphological misinterpretation is the original description of so-called proximally ribbon-like pennaceous feathers (PRPFs) found in the tail region of the maniraptoran theropod Epidexipteryx (Zhang et al. 2008), Confuciusornithidae (Chiappe et al. 1999) and several Enantiornithes (e.g. Zhang and Zhou 2000; Zheng et al. 2007). According to Zhang and Zhou (2000) and Xu et al. (2010a) , this feather type consists of a proximally ribbonlike element, composed of two sheet-like vanes divided longitudinally by a median line, which is identified as a rhachis. ...
Article
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Dinosaurs with fossilized filamentous integument structures are usually preserved in a highly flattened state. Several different feather types have been described on this basis, but the two-dimensional preservation of specimens during fossilization makes the identification of single feather structures difficult due to overlapping feather structures in vivo. Morphological comparison with the diversity of recent feather types is therefore absolutely vital to avoid misinterpretation. To simulate the preservation process, a cadaver of recent Carduelis spinus (European siskin) was flattened in a printing press. Afterwards, the structure of the plumage was compared with the morphology of a single body feather from the same specimen. In comparison with the single feather, the body plumage of the flattened bird looked rather filamentous. It was almost impossible to identify single structures, and in their place, various artefacts were produced. The investigation of plumage in a specimen of the Mesozoic bird Confuciusornis sanctus reveals similar structures. This indicates that flattening of specimens during fossilization amplifies the effect of overlapping among feathers and also causes a loss of morphological detail which can lead to misinterpretations. The results are discussed in connection with some dubious feather morphologies in recently described theropods and basal birds. Based on recent feather morphology, the structure of so-called proximal ribbon-like pennaceous feathers (PRPFs) found in many basal birds is reinterpreted. Furthermore, the morphology of a very similar-looking feather type found in the forelimb and tail of an early juvenile oviraptorosaur is discussed and diagnosed as the first feather generation growing out of the feather sheath. Thus, the whole plumage of this theropod might represent neoptile plumage.
... Another longipterygid, S. cooperorum, preserves the only evidence of an aerodynamic feathered tail within Enantiornithes ). The morphology of this taxon represents a distinct departure from the typical enantiornithine that either does not have elongate rectrices (Zhou et al. 2005) or possesses no more than two or four very elongate display feathers Zheng et al. 2007). The holotype of S. cooperorum preserves more than four rectrices of unknown length (distal ends not preserved) overlapping to form a single surface, a morphology that would have represented a considerable aerodynamic advantage over other known enantiornithine feathered tails ). ...
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A careful reappraisal of the only known specimen of the poorly understood fossil enantiornithine bird Boluochia zhengi reveals numerous morphological similarities that suggest this taxon is closely related to the well-known Longipteryx chaoyangensis, and so is assignable to the most diverse recognized clade of Early Cretaceous enantiornithines, the Longipterygidae. This new study of the holotype of B. zhengi reveals new longipterygid synapomorphies and expands our knowledge of the temporal and geographical ranges and diversity of the clade. We suggest that the trophic specialization that characterizes longipterygids may have been a major factor contributing to the success of this clade.
... Bohaiornis is larger than all other enantiornithine specimens from the Jiufotang Formation except for the closely related basal forms Pengornis and Xiangornis (Zhou et al., 2008;Hu et al., 2012). It is also significantly larger than most species from the underlying Yixian Formation or older deposits, such as Protopteryx (Zhang and Zhou, 2000), Paraprotopteryx (Zheng et al., 2007), Longirostravis (Hou et al., 2004) and Eoenantiornis , but only slightly larger than Shenqiornis (Wang et al., 2010). Both large-and small-bodied basal enantiornithines are present in the Yixian Formation, and proposed Yixian equivalents or older geological units (e.g., Qiaotou Formation;Ji, 2004), and younger Jiufotang Formation. ...
Article
A new specimen of Bohaiornis guoi from the Jiufotang Formation, comprising a nearly complete skeleton, sheds light on enantiornithine morphological variation and ecological specialization. The new specimen was collected from near Lamadong Village in Liaoning Province, which is the same area where the sub-adult holotype specimen was reported. It provides new information on the cranial and pectoral girdle anatomy of the species, e.g., broad nasal, strikingly robust acromion, medially curved acrocoracoid process. In contrast to the holotype, the newly referred specimen has small rounded stones in the thoracic region that in other extinct taxa has been interpreted as direct evidence of diet. Direct evidence of diet is so far unknown in other Enantiornithes. Specifically the lack of “stomach stones” or gastroliths in enantiornithines despite their excellent fossil record has been proposed to be related to their insectivorous diet as well as to their arboreal ecology. We hypothesize that cranial morphology as well as the number and shape of the preserved stones in Bohaiornis may be most consistent with a raptorial ecology previously unknown for Enantiornithes and considered rare for Avialae. While rostrum shape has a strong relationship to feeding ecology in living birds, in basal avialan birds most diversity is in dental morphology, number, and distribution of the teeth.
... As in Eopengornis, the faint impression of barbs can be identified along the entire length of the rectrices, whereas in Confuciusornis [26] and other enantiornithines (e.g. Dapingfangornis [27], Paraprotopteryx [28]) with elongate paired rectrices in the pennaceous portion is distally restricted as in the 'racket-plumes' of living birds. The medial and lateral barbs both form a small angle of approximately 10°with the rachis, and the lateral vane seems exceeds the width of the medial vane, although vaguely preserved in this impression, while far more obvious in Eopengornis STM 24-1 [6]. ...
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We describe a new enantiornithine bird, Parapengornis eurycaudatus gen. et sp. nov. from the Lower Cretaceous Jiufotang Formation of Liaoning, China. Although morphologically similar to previously described pengornithids Pengornis houi, Pengornis IVPP V18632, and Eopengornis martini, morphological differences indicate it represents a new taxon of the Pengornithidae. Based on new information from this specimen we reassign IVPP V18632 to Parapengornis sp. The well preserved pygostyle of the new specimen elucidates the morphology of this element for the clade, which is unique in pengornithids among Mesozoic birds. Similarities with modern scansores such as woodpeckers may indicate a specialized vertical climbing and clinging behavior that has not previously been inferred for early birds. The new specimen preserves a pair of fully pennaceous rachis-dominated feathers like those in the holotype of Eopengornis martini; together with the unique morphology of the pygostyle, this discovery lends evidence to early hypotheses that rachis-dominated feathers may have had a functional significance. This discovery adds to the diversity of ecological niches occupied by enantiornithines and if correct reveals are remarkable amount of locomotive differentiation among Enantiornithes.
... holotype (IVPP V 17964) The white arrows indicate five pennaceous feathers, which we interpret as leg feathers (see text) 52卷 古 脊 椎 动 物 学 报 the bone, although the distal ends of three of the feathers curve towards the pygostyle. In some enantiornithines from the Jehol Biota, the tail coverts radiate from the pygostyle and form a large acute angle with the shaft Zheng et al., 2007;Zheng et al., 2013b); besides, two long rectrices are preserved in the Bohaiornis holotype, which are close to the humeral length and substantially longer than these feathers in Longusunguis (Hu et al., 2011), leading us to suggest that the feathers preserved in the present specimen are more likely to be leg feathers, than rectrices. This interpretation is consistent with the fact that these feathers, when traced proximally, end adjacent to the surface of the tibial shaft. ...
Article
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Two new enantiornithine birds, Parabohaiornis martini gen. et sp. nov., and Longusunguis kurochkini gen. et sp. nov., are reported here based on three nearly complete skeletons from the Lower Cretaceous lacustrine deposits of the Jiufotang Formation in Liaoning, northeastern China. The two new species share several unique features with Bohaiornis, Shenqiornis, Sulcavis and Zhouornis, including a robust rostrum with robust, subconical teeth, furcula with blunt omal expansions, sternal trabeculae caudolaterally directed, short and stout tarsometatarsus with hypertrophied ungual on digit Ⅲ. A close relationship among the two new species and four previously described taxa is confirmed by a comprehensive phylogenetic analysis, leading us to erect Bohaiornithidae fam. nov. With six known taxa, Bohaiornithidae is the most diverse recognized enantiornithine family. The robust morphology of the rostrum and foot suggests bohaiornithids occupied a specialized ecological niche compared to other Early Cretaceous enantiornithines.
... Zhang pers. comm.) and the skull of the holotype of Paraprotopteryx gracilis (STM V001) does not belong to the main slab (Zheng et al. 2007;Z.-H. Zhang pers. ...
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Enantiornithines are the most speciose avian clade in the Mesozoic, with a fossil record that nearly spans the Cretaceous; however, with less than half of known taxa preserving skull material, our understanding of their cranial morphology remains incomplete. Here we present a comprehensive overview of the current knowledge of enantiornithine skull anatomy and discuss the range of morphologies known for each of the main cranial elements. The typical enantiornithine skull retains numerous ancestral features such as the absence of fusion among bones, the presence of a postorbital bone, a primitive quadrate with a single headed otic process, an unforked dentary, and teeth. The postorbital in at least one taxon is unreduced, suggesting the existence of a complete infratemporal fenestra and thus an unmodified diapsid skull as in confuciusornithids. The rostrum is well known and shows considerable variation, typical of theropods; however, in terms of rostral proportions, enantiornithines are extremely limited within the modern avian spectrum. Although Late Cretaceous skull material is extremely fragmentary, when compared to Early Cretaceous material it reveals a trend towards more specialized morphologies in younger taxa. The foramen magnum in all taxa points caudally, indicating that the ‘flexed’ type skull morphology may not have evolved in this group. Enantiornithine teeth show considerable diversity in numbers, size, morphology and placement, ranging from taxa with large teeth found throughout the jaws to taxa with small, rostrally restricted teeth, to the fully edentulous. Despite limited preservation of skull material, a number of trophic specializations can be deduced from the range of preserved morphologies, further hinting at the morphological and ecological diversity of the Cretaceous Enantiornithes.
... Unlike within Confuciusornithiformes, among enantiorni thines there is a diversity of morphologies associated with the rachis dominated rectrices (O'Connor, 2009). The shape of the distal "racket" varies between taxa, as well as the overall length of the feathers with respect to the body; one taxon may have preserved two such pairs of rectrices (Paraprotopteryx) (Zheng et al., 2007). This further supports the interpretation of these feathers as ornamental features. ...
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The recently described specimen of Sapeornis with feathers around the ankle joint is the first finding of birds with metatarsal feathers. The discovery of several groups of paravians with feathered distal hindlimbs has been used as evidence that flight in Aves evolved through the tetrapteryx stage. However, most specimens of Sapeornis do not preserve feathers around the feet, and these feathers are clearly absent in at least one exceptional specimen preserving skin and feather impressions. This suggests that the presence of ankle feathers in Sapeornis may alternatively be interpreted as ornamentation. Basal birds show more ornamental tail morphologies than aerodynamic ones suggesting that sexual selection played a dominant role in shaping tail plumage. Feathers on the forelimbs initially evolved for a purpose other than flight, and we propose aerodynamics was not the driving force in the hindlimb feather evolution. Feathers appear to be means of visual communication playing a very important role in the evolution of paravian plumage.
... These feathers are incomplete distally, but the preserved part of each ETF is identical to the corresponding structure in some primitive birds 16,[26][27][28] , for example in having a similar central rachis and unbranched vanes (Fig. 1a, 1d, with long tail plumage attract more mates than their short-tailed counterparts 30 . It is highly probable that the ETFs of Epidexipteryx likewise had display as their primary function, rather than serving other purposes such as flight or insulation 29 femur; fi, fibula; ga, gastralia; hu, humerus; il, ilium; is, ischium; ma, mandible; mtI-IV, metatarsals I-IV; p, phalanges or metacarpals; pa, parietal; pm, premaxilla; pu, pubis; q, quadrate; r, ribs; ra, radius; rc, rachis; sc, scapula; st, sternum; ti, tibia; tv, thoracic vertebrae; u, ungual phalanges; ul, ulna; uv, unbranched vane; 4 ETFs, 4 elongate ribbon-like tail feathers. ...
Article
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Recent coelurosaurian discoveries have greatly enriched our knowledge of the dinosaur-bird transition, but all reported taxa close to this transition are from relatively well-known coelurosaurian groups^1-3^. Here we report a new basal avialan, Epidexipteryx hui gen. et sp. nov., from the Middle-Late Jurassic of Inner Mongolia, China. This new species is characterized by an unexpected combination of characters seen in several different theropod groups, particularly the Oviraptorosauria. Phylogenetic analysis shows it to be the sister taxon to Epidendrosaurus^4,5^, forming a new clade at the base of Avialae^6^. Epidexipteryx also possesses two pairs of elongate ribbon-like tail feathers (ETFs), and its limbs lack contour feathers for flight. This finding shows that a member of the avialan lineage experimented with integumentary ornamentation as early as the Middle-Late Jurassic, and provides further evidence relating to this important aspect of the transition from non-avian theropods to birds.
... Never theless, they concluded that the integument of Longisquama shares several morphological char acters with feathers and developed through a twostage process similar to that by which feath ers develop. interestingly, the long scalelike feathers of Protopteryx and Paraprotopteryx (Zheng et al. 2007) are some what similar, at least in overall appearance, to the integumentary structures of Longisquama. Our recovery of Longisquama in a weakly supported clade with birds and maniraptorans (figs. ...
... Several enantiornithines, including Protopteryx (Zhang and Zhou, 2000), Dapingfangornis (Li et al., 2006) and Paraprotopteryx (Zheng et al., 2007), have an essentially Confuciusornis-like tail plumage consisting of a small number of rachis-dominated racket-plumes (O'Connor et al., 2012b). However, Eopengornis (X.L. and Parapengornis (Hu et al., 2015) each sport a single pair of elongate but fully pennaceous rachis-dominated rectrices, whereas Chi- appeavis ) possesses a tail fan composed of about 10 overlapping rectrices of normal morphology. ...
Article
Recently reported specimens from the Mid-Late Jurassic Yanliao (or Daohugou) Biota and Early Cretaceous Jehol Biota of Northeast China suggest that the early evolution of avian flight involved a surprising amount of homoplasy and evolutionary experimentation. Pennaceous feathers of variable size, structure, and extent occur on the hindlimbs of numerous Jehol and Yanliao paravian theropods, including some basal birds, and clearly had an aerodynamic function at least in the dromaeosaurid Microraptor. However, their function in many cases may have been primarily ornamental, and it is unclear whether aerodynamically useful hindwings represent a widespread paravian feature or an evolutionary novelty limited to Microraptor and possibly a few other taxa. Clearer examples of novelties related to aerial locomotion are the tail plumage of the basal bird Jeholornis, in which a proximal fan of feathers is present and the ancestral distal frond is somewhat reduced, and the membranous wings of the Yanliao scansoriopterygid Yi. Early paravian evolution evidently involved a rapid diversification of aerodynamic structures, and ancestral paravians may have been volant. It is also possible that the avian lineage passed through a four-winged “tetrapterygian” stage, but current phylogenies suggest that aerodynamic hindwings were more likely acquired independently by different paravian groups.
... Zhang pers. comm.) and the skull of the holotype of Paraprotopteryx gracilis (STM V001) does not belong to the main slab (Zheng et al. 2007;Z.-H. Zhang pers. ...
Conference Paper
Enantiornithines are the most speciose avian clade in the Mesozoic, however with less than half of known taxa preserving skull material, our understanding of their cranial morphology remains incomplete. Here we present a comprehensive overview of the current knowledge of enantiornithine skull anatomy and discuss the range of morphologies known for the main cranial elements. The typical enantiornithine skull retains numerous ancestral features such as the lack of fusion among bones, the presence of a postorbital, a primitive quadrate, an unforked dentary, and teeth. The rostrum is well known and shows considerable variation; the premaxilla varies in degree of fusion and the relative lengths of the nasal and maxillary processes. The nasals range from broad to narrow, with the maxillary process reduced or absent. The relative lengths of the premaxillary, jugal, and nasal processes of the maxilla vary considerably; in no taxa is a second accessory maxillary fenestra known. The bones of the braincase are typically unfused. The foramen magnum in all taxa in which preserved is directed caudally, not ventrally. Typically the dentaries are incompletely fused rostrally, and the lower jaw is imperforate. Enantiomithine teeth show considerable diversity in numbers, size, morphology and placement ranging from taxa with large teeth found throughout the jaws to taxa with small, anteriorly restricted teeth to the fully edentulous. Despite limited preservation of skull material, a number of trophic specializations can be deduced from the range of preserved morphologies further hinting at the diversity of the Cretaceous Enantiornithes.
... However, the recognition of Praeornis as a rachis-dominated rectricial feather argues against the evolutionary scenario proposed by Dzik et al. (2010) and Sulej and Niedzwiedzki (2011). Since the discovery of ribbon-like elongate feathers in Confuciusornis, authors mostly agreed that such elongate structures may be associated with sexual display or visual communication ( Chiappe et al. 1999;Zhang and Zhou 2000;Clarke et al. 2006;Li et al. 2006;Zheng et al. 2007;Chiappe et al. 2008;Li et al. 2012;O′Connor et al. 2011;Padian and Horner 2011;O′Connor et al. 2012O′Connor et al. , 2013). In living birds with elongate forked tail, the rectrices change their angle of attack and angle of spread, and thus, the tail streamers retain an aerodynamic function (e.g., Balmford et al. 1994;Thomas 1997;Tubaro 2003). ...
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Since its original description as a feather belonging to a basal bird, the phylogenetic position of Praeornis sharovi was debated. It was considered as belonging to a bird, a cycad leaf, or as a ‘transitional’ integumentary structure between reptile scales and bird feathers. Recently, a basal enantiornithine bird was collected in Early Cretaceous beds of Brazil. This specimen shows very well-preserved rachis-dominated tail feathers with a very thick rachis and thick and rigid barbules. These features are present in Praeornis, suggesting that this fossil may be interpreted as the tail feather of a basal bird. In this way, Praeornis constitutes one of the oldest records of rachis-dominated feathers in the world. Rachis-dominated tail feathers, including that of Praeornis appear to be rigid paired structures not performed for aerodynamical purposes, suggesting that may be important in body balance.
... Others interpreted tail feathers as having assisted with maintaining body balance when perching (Chuong et al., 2013;Agnolin et al., 2017), or with stabilizing the trunk when climbing (Hu et al., 2015). Still other authors suggested that elongate tail feathers might have been associated with sexual display or visual communication (Chiappe et al., 1999Zhang and Zhou, 2000;Clarke et al., 2006;Li et al., 2006Li et al., , 2012Zheng et al., 2007;O'Connor et al., 2011bO'Connor et al., , 2012O'Connor et al., , 2013Padian and Horner, 2011). These possibilities are not mutually exclusive, and it seems reasonable to suppose that different tail feather functions complemented and interacted with one another in the lives of these animals. ...
Article
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Recent years witnessed the discovery of a great diversity of early birds as well as closely related non-avian theropods, which modified previous conceptions about the origin of birds and their flight. We here present a review of the taxonomic composition and main anatomical characteristics of those theropod families closely related with early birds, with the aim of analyzing and discussing the main competing hypotheses pertaining to avian origins. We reject the postulated troodontid affinities of anchiornithines, and the dromaeosaurid affinities of microraptorians and unenlagiids, and instead place these groups as successive sister taxa to Avialae. Aiming to evaluate previous phylogenetic analyses, we recoded unenlagiids in the traditional TWiG data matrix, which resulted in a large polytomy at the base of Pennaraptora. This indicates that the TWiG phylogenetic scheme needs a deep revision. Regarding character evolution, we found that: (1) the presence of an ossified sternum goes hand in hand with that of ossified uncinate processes; (2) the presence of foldable forelimbs in basal archosaurs indicates widespread distribution of this trait among reptiles, contradicting previous proposals that forelimb folding driven by propatagial and associated tendons was exclusive to the avian lineage; (3) in basal paravians and avialans (e.g., Archaeopteryx, Anchiornis) the wings are relatively large and wide, with relatively short rectricial feathers, a rounded alar contour, and a convex leading margin. These taxa exhibit restricted forelimb folding capability with respect to more derived birds, their hands being preserved at angles of flexion (with respect to the radius/ulna) of no less than 90°. In more derived birds, however, the rectrices are notably elongate and the angle between the hand and forearm is much less than 90°, indicating not only increased forelimb folding capability but also an increased variety of wingbeat movements during flight. Because of the strong similarities in pectoral girdle configuration between ratites and basal avialans and paravians, it is possible to infer that the main forelimb movements were similar in all these taxa, lacking the complex dorsoventral wing excursion characteristic of living neognathans.
... Also, those in Psittacosaurus are more rigid and more widely separated from each other than in Tianyulong. The central tail feathers of the basal avialan Epidexipteryx 12 (Fig. 2e), the basal pygostylian (all birds with shortened tails) Confuciusornis 13 and some enantiornithean (one of the two major clades of early birds, which became extinct by the end of Cretaceous period) birds 14,15 are also elongate, and represent a feather type unknown in extent birds. Unlike the structures in Tianyulong, however, they are ribbon-like and branch at their distal ends 10 . ...
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Ornithischia is one of the two major groups of dinosaurs, with heterodontosauridae as one of its major clades. Heterodontosauridae is characterized by small, gracile bodies and a problematic phylogenetic position. Recent phylogenetic work indicates that it represents the most basal group of all well-known ornithischians. Previous heterodontosaurid records are mainly from the Early Jurassic period (205-190 million years ago) of Africa. Here we report a new heterodontosaurid, Tianyulong confuciusi gen. et sp. nov., from the Early Cretaceous period (144-99 million years ago) of western Liaoning Province, China. Tianyulong extends the geographical distribution of heterodontosaurids to Asia and confirms the clade's previously questionable temporal range extension into the Early Cretaceous period. More surprisingly, Tianyulong bears long, singular and unbranched filamentous integumentary (outer skin) structures. This represents the first confirmed report, to our knowledge, of filamentous integumentary structures in an ornithischian dinosaur.
... This study concluded that the rod-like tail present in more basal, non-ornithurine birds was just stiffened and reduced, with only two retrices attached until this pygostyle morphology evolved. The evolution of retricial feathering itself was covered by Gatesy and Dial (1996), Gatesy (2001b), and Zheng et al. (2007). Again, the clade Ornithurae (Fig. 1) seems to be where the caudal appendage of theropods achieved its major functional aspects inherited by crown group birds. ...
Article
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The bipedal stance and gait of theropod dinosaurs evolved gradually along the lineage leading to birds and at some point(s), flight evolved. How and when did these changes occur? We review the evidence from neontology and paleontology, including pectoral and pelvic limb functional morphology, fossil footprints/trackways and biomechanical models and simulations. We emphasise that many false dichotomies or categories have been applied to theropod form and function, and sometimes, these impede research progress. For example, dichotomisation of locomotor function into 'non-avian' and 'avian' modes is only a conceptual crutch; the evidence supports a continuous transition. Simplification of pelvic limb function into cursorial/non-cursorial morphologies or flexed/columnar poses has outlived its utility. For the pectoral limbs, even the classic predatory strike vs. flight wing-stroke distinction and separation of theropods into non-flying and flying--or terrestrial and arboreal--categories may be missing important subtleties. Distinguishing locomotor function between taxa, even with quantitative approaches, will always be fraught with ambiguity, making it difficult to find real differences if that ambiguity is properly acknowledged. There must be an 'interpretive asymptote' for reconstructing dinosaur limb function that available methods and evidence cannot overcome. We may be close to that limit, but how far can it be stretched with improved methods and evidence, if at all? The way forward is a combination of techniques that emphasises integration of neontological and paleontological evidence and quantitative assessment of limb function cautiously applied with validated techniques and sensitivity analysis of unknown variables.
... Although for some taxa all that is known is a faint incomplete impression of the enlarged rachis (e.g., Bohaiornis guoi and Protopteryx fengningensis), enantiornithine rachis-dominated feathers show greater diversity than the confuciusornithiforms (which appear to share a single morphology): both streamers (fully pennaceous) and racket plumes (distally pennaceous) are documented (the fully pennaceous morphology is currently only documented in two species of the Pengornithidae, Eopengornis martini and Parapengornis eurycaudatus) (Hu et al. 2015;Wang et al. 2014c) (Fig. 9.5a). Within the racket-plume morphology, there is further diversity in the overall length of the feathers relative to the body, the number of pairs (one specimen reportedly preserves two, the holotype specimen of Paraprotopteryx zhengi, and Shanweiniao cooperorum is interpreted as having a similar morphology) (O'Connor et al. 2016b;Zheng et al. 2007) and the morphology of the distal "racket" (O'Connor et al. 2012a). In some taxa, the pennaceous portion is restricted to the distal most portion of the rachis (Junornis), rapidly expanding with a rounded distal margin (spoonshaped as in Dapingfangornis), whereas the pennaceous portion expands gradually and extends for a greater proportion of the feather in others (e.g., GSGM-07-CM-001, an unnamed enantiornithine from the Xiagou Formation). ...
Chapter
Early bird plumage is well known primarily due to numerous discoveries of specimens preserving feathers from Early Cretaceous deposits in China. Remiges and rectrices are most commonly preserved with rectrices showing the greatest variation. The long boney-tailed Jeholornis has a unique tail plumage employing two anatomically distinct rectricial pterylae serving both aerodynamic and ornamental functions. Basal pygostylians show disparate tail plumages that are reflected by differences in pygostyle morphology. Sapeornis has a proportionately shorter pygostyle wielding a fan-shaped array of rectrices, whereas the robust pygostyle of Confuciusornis is associated with a pair of elongate rachis-dominated feathers in some specimens, considered indicative of sexual dimorphism. The latter morphology is also present in many enantiornithines. Members of this diverse clade have primarily ornamental tail morphologies, whereas the earliest members of the Ornithuromorpha all possess tail morphologies that appear to be primarily aerodynamic. Body feathers in Archaeopteryx and adult enantiornithines trapped in amber are pennaceous suggesting that reported rachis-less body feathers in Jehol birds may be taphonomic artifacts. Rarely preserved, well-developed pennaceous crural feathers are present in Archaeopteryx and some enantiornithines, whereas crural feathers are short in the Confuciusornithiformes. Their preserved absence in nearly all Jehol ornithuromorph specimens most-likely reflects the smaller available sample size. Crural feathers in many basal ornithuromorphs were probably reduced, as in Yanornis and extant aquatic and semiaquatic birds. Overall, early birds show a trend towards the reduction of the distal hindlimb feathers present in closely related nonavian dinosaurs. However, well-developed tarsometatarsal feathers are present in Sapeornis and two exceptionally well-preserved enantiornithine specimens indicate this group was diverse in the distal extent of their hindlimb plumage, including at least one lineage with feathered pedal digits. Although remarkably modern in many aspects, early bird plumage still differed from that of their modern counterparts including extinct morphotypes and differences in ontogenetic patterns.
Article
An incomplete postcranial avian skeleton is described from the Lower Cretaceous Jingchuan Formation of Otog Banner of western Inner Mongolia and referred to a new species of Cathayornis, C. chabuensis sp. nov. This is the first report of a Cathayornis from outside Liaoning Province. The new discovery indicates that Cathayornis coexisted with Otogornis genghisi, and a more detailed comparison between these two enantiornithine genera shows that Otogornis represents a more primitive genus than Cathayornis. Our analyses further indicate that Cathayornis is an arboreal bird. The discovery of a Cathayornis from this region also confirms that the avian fossil-bearing Jingchuan Formation is comparable to the Jiufotang Formation of the upper Jehol Group in western Liaoning, and should be referred to the middle-late Early Cretaceous.
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A new enantiornithine bird, Bohaiornis guoi, gen. et sp. nov., is described in this paper. The holotype, presumably a sub-adult, is a complete, fully articulated skeleton from the Lower Cretaceous Yixian Formation of western Liaoning, northeastern China. Bohaiornis exhibits some similarity in morphology to Eoenantiornis, but Bohaiornis is much larger than Eoenantiornis and differs from all previously known enantiornithine birds including Eoenantiornis in having the following features: caudal end of the articular pointed caudoventrally, sacral centra strongly compressed transversely, and clavicular ramus straight with a laterally expanded omal end. The almost perfectly preserved skeleton of this new specimen not only reveals many morphological features previously unknown in basal birds, but also clarifies many fine details of previously known features.
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Birds are some of the most diverse organisms on Earth, with species inhabiting a wide variety of niches across every major biome. As such, birds are vital to our understanding of modern ecosystems. Unfortunately, our understanding of the evolutionary history of modern ecosystems is hampered by knowledge gaps in the origin of modern bird diversity and ecosystem ecology. A crucial part of addressing these shortcomings is improving our understanding of the earliest birds, the non‐avian avialans (i.e. non‐crown birds), particularly of their diet. The diet of non‐avian avialans has been a matter of debate, in large part because of the ambiguous qualitative approaches that have been used to reconstruct it. Here we review methods for determining diet in modern and fossil avians (i.e. crown birds) as well as non‐avian theropods, and comment on their usefulness when applied to non‐avian avialans. We use this to propose a set of comparable, quantitative approaches to ascertain fossil bird diet and on this basis provide a consensus of what we currently know about fossil bird diet. While no single approach can precisely predict diet in birds, each can exclude some diets and narrow the dietary possibilities. We recommend combining (i) dental microwear, (ii) landmark‐based muscular reconstruction, (iii) stable isotope geochemistry, (iv) body mass estimations, (v) traditional and/or geometric morphometric analysis, (vi) lever modelling, and (vii) finite element analysis to reconstruct fossil bird diet accurately. Our review provides specific methodologies to implement each approach and discusses complications future researchers should keep in mind. We note that current forms of assessment of dental mesowear, skull traditional morphometrics, geometric morphometrics, and certain stable isotope systems have yet to be proven effective at discerning fossil bird diet. On this basis we report the current state of knowledge of non‐avian avialan diet which remains very incomplete. The ancestral dietary condition in non‐avian avialans remains unclear due to scarce data and contradictory evidence in Archaeopteryx. Among early non‐avian pygostylians, Confuciusornis has finite element analysis and mechanical advantage evidence pointing to herbivory, whilst Sapeornis only has mechanical advantage evidence indicating granivory, agreeing with fossilised ingested material known for this taxon. The enantiornithine ornithothoracine Shenqiornis has mechanical advantage and pedal morphometric evidence pointing to carnivory. In the hongshanornithid ornithuromorph Hongshanornis only mechanical advantage evidence indicates granivory, but this agrees with evidence of gastrolith ingestion in this taxon. Mechanical advantage and ingested fish support carnivory in the songlingornithid ornithuromorph Yanornis. Due to the sparsity of robust dietary assignments, no clear trends in non‐avian avialan dietary evolution have yet emerged. Dietary diversity seems to increase through time, but this is a preservational bias associated with a predominance of data from the Early Cretaceous Jehol Lagerstätte. With this new framework and our synthesis of the current knowledge of non‐avian avialan diet, we expect dietary knowledge and evolutionary trends to become much clearer in the coming years, especially as fossils from other locations and climates are found. This will allow for a deeper and more robust understanding of the role birds played in Mesozoic ecosystems and how this developed into their pivotal role in modern ecosystems. Video abstract
Article
A new bird from the early Cretaceous Yixian Formation of Liaoning, China is described. This new species, Grabauornis lingyuanensis, shares several synapomorphies with the Enantiornithes. The specimen is relatively well preserved. The skeletal morphology of Grabauornis bears close resemblance to that of other Chinese members of this clade. The brachial index (the ratio between the lengths of humerus and ulna) is 0.95, which is close to the average for enantiornithine birds. It indicates that Grabauornis was a rather good flyer, and the presence of an alula in the wing further testifies to this.
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The hypothesis that birds are maniraptoran theropod dinosaurs (the "BMT hypothesis") has become widely accepted by both scientists and the general public. Criticism has usually been dismissed, often with the comment that no more parsimonious alternative has been presented with cladistic methodology. Rather than taking that position, we ask here whether the hypothesis is as overwhelmingly supported as some claim. We reanalyzed a standard matrix of 46 taxa and 208 characters from a recent paper by Clark, Norell, and Makovicky, and we found statistical support for the clades Coelurosauria and Maniraptoriformes and for a clade of birds and maniraptorans. Note, however, that because the matrix contains only birds and theropods, it assumes that the origin of birds lies within the Theropoda. In addition to this problem, Clark et al.'s (2002) matrix contains problematic assumptions of homology, especially in the palate, basipterygoid, manus, carpus, and tarsus. In an attempt to avoid these two major prob...
Article
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Article
We describe the anatomy and bone histology of an enantiornithine specimen from the Early Cretaceous Jehol Group of northeastern China. CNUVB-0903 is larger than most Early Cretaceous enantiornithine birds and also different from all other named taxa. Thus, we erect the new species Zhouornis hani for the new specimen. CNUVB-0903 preserves a suite of new morphologies for the clade. Noteworthy are those of the braincase and occipital region of the skull, which was previously poorly known for enantiornithines. The morphology and placement of the large basipterygoid processes and the well-developed basisphenoid recess—comparable in morphology to those of non-avian dinosaurs—highlights the evolutionary conservatism of the enantiornithine skull. The histological characterization of CNUVB-0903 indicates that it was not yet a full-grown individual at the time of death. This, combined with the comparatively large size of the skeleton, supports previous evidence indicating that early in their history, enantiornithines were able to achieve relatively large sizes.
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A brief introduction to the morphology, flight, size, habits, diet, feathers and systematic paleontology of fossil enantiornithine birds known from the Mesozoic of China is provided. Enantiornithine birds were the dominant land birds of the Mesozoic (245–65 Myr). Although they show great morphological differences from modern birds, their diversification in many respects mimics that of the modern land bird radiation and the reasons for their extinction at the end‐Cretaceous remain a mystery.
Article
Since the 1990s, the avian fossil record has been greatly advanced with the oldest record found from the Upper Jurassic and a pan-global distribution discovered in the Cretaceous. Birds possess highly modified skeletal characteristics such as the pygostyle, keeled sternum, forelimbs developed as wings, and toothless jaws, all of which are considered to have evolved in relation to flight. Recent discoveries have also revealed that Mesozoic birds had made various ecological developments including sexual dimorphism and differential growth rates. Although the reasons for the limited diversification of flightless birds in the Mesozoic and for the survival of the Neornithes through the K-Pg mass extinction event are still not well understood, they may be attributed to environmental and physiological limitations. In this paper, I suggest that the development of flight capability, endothermy, and efficient digestive systems may have been involved in the diversification and wide geographical distribution of birds. Although physiological characteristics are rarely preserved in the fossil record, new fossil discoveries and advancements in research on soft tissue reconstruction might reveal more details of the ecology of extinct birds in the near future.
Chapter
Several stem birds, such as Confuciusornithidae and Enantiornithes, were characterized by the possession of one or two pairs of conspicuous, elongated tail feathers with a unique morphology, so-called rhachis-dominated racket plumes. In the past, several studies reported contradictory interpretations regarding the morphology of these feathers, which sometimes failed to match with any morphology known from modern feathers. In this chapter, these interpretations are reviewed and compared with various modern feather types. The comparison confirms recent interpretations that the rhachis-dominated racket plumes are highly modified pennaceous feathers with ornamental function, originating at least two times independently from each other during evolution. While the gross organization (i.e., a short distal vane and a long, naked rhachis) of these feathers resembles that of filoplumes, they resemble pennaceous body feathers of penguins in terms of rhachis morphology and pigmentation pattern. As the rhachis-dominated racket plumes combine different morphologies that are apparent among modern feather types, this extinct morphotype does in fact not show any aberrant morphological novelties, but rather fall into the morphological and developmental spectrum of modern feathers.
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Recent coelurosaurian discoveries have greatly enriched our knowledge of the transition from dinosaurs to birds, but all reported taxa close to this transition are from relatively well known coelurosaurian groups. Here we report a new basal avialan, Epidexipteryx hui gen. et sp. nov., from the Middle to Late Jurassic of Inner Mongolia, China. This new species is characterized by an unexpected combination of characters seen in several different theropod groups, particularly the Oviraptorosauria. Phylogenetic analysis shows it to be the sister taxon to Epidendrosaurus, forming a new clade at the base of Avialae. Epidexipteryx also possesses two pairs of elongate ribbon-like tail feathers, and its limbs lack contour feathers for flight. This finding shows that a member of the avialan lineage experimented with integumentary ornamentation as early as the Middle to Late Jurassic, and provides further evidence relating to this aspect of the transition from non-avian theropods to birds.
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Although recent discoveries from Lower Cretaceous sediments in northeastern China have greatly improved our understanding of the initial stages of avian diversification in eastern Asia, the early evolution of Aves elsewhere on the continent remains poorly understood. In 2004, a collaborative field effort directed by personnel from the Chinese Academy of Geological Sciences and Carnegie Museum of Natural History recovered multiple partial to nearly complete avian skeletons from outcrops of the Lower Cretaceous Xiagou Formation exposed in the Changma Basin of northwestern Gansu Province, China. Here we describe a thrush-sized partial skeleton comprised of a fragmentary pelvic girdle and largely complete hind limbs. A phylogenetic analysis of 20 avian ingroup taxa and 169 anatomical characters places the specimen in Enantiomithes, and within that clade, in Enenantiomithes. When coupled with additional recent discoveries from the Changma Basin, the new skeleton improves our understanding of early avian evolution and diversification in central Asia.
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We report on the discovery of an Early Cretaceous bird from northwestern Gansu Province, in northwestern China. Represented by a nearly complete left wing and shoulder girdle the size of a rock dove, the new bird was quarried from laminated yellowish mudstones of the Xiagou Formation (Xinminpu Group) near Changma, in the Jiuquan area. These deposits have previously yielded the only known specimen of Gansus yumenensis, a basal ornithuromorph represented by the distal half of a hind limb with long and slender digits. Several derived characters of the new occurrence supports its allocation within Enantiornithes: (1) a convex lateral margin of the coracoid, (2) a minor metacarpal that projects distally more than the major metacarpal and (3) a proximal phalanx of the major digit longer than the intermediate (second) phalanx. The general proportions of the wing suggest it was a flier comparable to most other known enantiornithine birds. Although, direct comparisons between the new fossil and Gansus are not possible, phylogenetic based inferences supports their placement into two different clades. While the new fossil falls definitively within the enantiornithines, G. Yumenensis falls within the ornithuromorphs. The new occurrence thus adds to the taxonomic diversity of Early Cretaceous birds from Gansu Province in particular and central Asia in general.
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More than half of the evolutionary history of birds is played out in the Mesozoic. A recent burst of fossil discoveries has documented a tremendous diversity of early avians. Clarification of the Phylogenetic structure of this diversity has provided clues for a better understanding of the evolution of functional, developmental and physiological characteristics of modern birds. Yet their long Mesozoic history is only beginning to be deciphered.
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We report new 40Ar÷39Ar dating results obtained from total fusion and incremental-heating analyses of sanidine and biotite from three tuffs found interbedded within the fossil-bearing deposits of Liaoning, northeast China. The first is a new sample of the Bed 6 Sihetun tuff from the Yixian Formation, previously dated by our team as middle Early Cretaceous, and recently considered by Lo et al., partially reset due to metamorphism from a nearby basaltic sill. The second is the Yixian Bed 9 tuff from Hengdaozi considered by Lo et al. to be unaffected by metamorphism and whose age, based on total fusion 40Ar÷39Ar dating of biotite, argues for a Jurassic age for the Yixian Formation. The third tuff is a previously undated tuff from the upper part of the underlying Tuchengzi Formation. Single crystal total fusion 40Ar÷39Ar analyses of the Sihetun sanidine showed homogeneous radiogenic Ar, Ca÷K ratios, excellent reproducibility and gave a mean age of 125.0±0.18 (1SD)±0.04 (SE) Ma. Single sanidine crystal total fusion 40Ar÷39Ar analyses of the Hengdaozi tuff gave a mean age of 125.0±0.19 (1SD)±0.04 (SE) Ma, which is indistinguishable from the Sihetun tuff. The Tuchengzi Formation tuff gave a mean age of 139.4±0.19 (1SD)±0.05 (SE) Ma. Detailed laser incremental-heating analyses of biotite from Sihetun, Hengdaozi, and Tuchengzi tuffs show disturbed Ar release patterns and evidence of trapped argon components. We conclude from these analyses that the total fusion dates on biotite by Lo et al. are erroneously old and isotopic dating of both biotite and sanidine from tuffs of the Yixian Formation point to a middle Early Cretaceous age. The upper part of the Tuchengzi Formation can be referred to the Early Cretaceous.
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Since the description of Confuciusornis (the oldest beaked bird) in1995, based on three partial specimens, large numbers of complete skeletons have been recovered,. Most new material of Confuciusornis, can be assigned to a single sexually dimorphic species, C. sanctus . Here we report a new species based on a remarkably well preserved skeleton with feathers and, for the first time in the Mesozoic record, direct evidence of the shape of a horny beak. It has a complete and large preserved postorbital that has a broad contact with the jugal bone. This character is presently only known in Confuciusornis, and may confirm previous suggestions of a postorbital in Archaeopteryx. The squamosal is in tight contact with the postorbital. These two bones form an arch dividing the upper and lower temporal fenestrae, as in other diapsid reptiles. The presence of a typical diapsid cheek region with two openings in Confuciusornis may preclude the presence of prokinesis (upper jaw mobility against the braincase and orbital area), a feeding adaptation found in most modern birds. The presence of a horny beak, characteristic of modern birds, coupled with a primitive temporal region provides new evidence for a mosaic pattern in the early evolution of birds.
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A new specimen of an enantiornithean bird from the Lower Cretaceous Xiagou Formation of Gansu Province, northwestern China, consists of an articulated distal left humerus, ulna, radius, carpus, and manus. The specimen may represent a primitive enantiornithean because it lacks a longitudinal sulcus on the radius, has incompletely fused alular and major metacarpals, and possibly retains a remnant of a second phalanx on the minor digit. It differs from all other known enantiornitheans, and exhibits possible autapomorphies, including peculiar, flat humeral epicondyles, a pair of eminences on the distal minor metacarpal, and an enormous flexor tuberculum on the alular ungual. The specimen probably pertains to the same taxon as a previously described enantiornithean arm from Changma; the incompleteness of the taxon precludes erecting a new name, but it provides new information concerning enantiornithean diversity in the Early Cretaceous of central Asia.
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A partial skeleton of a primitive bird, Rahona ostromi, gen. et sp. nov., has been discovered from the Late Cretaceous of Madagascar. This specimen, although exhibiting avian features such as a reversed hallux and ulnar papillae, retains characteristics that indicate a theropod ancestry, including a pubic foot and hyposphene-hypantra vertebral articulations. Rahona has a robust, hyperextendible second digit on the hind foot that terminates in a sicklelike claw, a unique characteristic of the theropod groups Troodontidae and Dromaeosauridae. A phylogenetic analysis places Rahona with Archaeopteryx, making Rahona one of the most primitive birds yet discovered.
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AVIAN flight is one of the most remarkable achievements of vertebrate evolution, yet there is little evidence of its early phases. Specimens of Archaeopteryx shed important (albeit controversial) light on this evolutionary phenomenon, but the large morphological (and almost certainly functional) gap between Archaeopteryx and modern avians remained virtually empty until recently. Here we report a new, exquisitely preserved, bird from the Lower Cretaceous Konservat-Lagerstätte of Las Hoyas (Cuenca, Spain) which provides evidence for the oldest known alula (bastard wing). Crustacean remains found inside its belly also provide the oldest direct evidence of feeding habits in birds. The new specimen has numerous synapomorphies with the Enantiornithes, but its unique sternal morphology, along with other autopomorphies in the furcula and vertebral centra, support the recognition of a new enantiornithine taxon, Eoalulavishoyasi. The combination in Eoalulavis of a decisive aerodynamic feature, such as the alula, with the basic structures of the modern flight apparatus indicates that as early as 115 million years ago, birds had evolved a sophisticated structural system that enabled them to fly at low speeds and to attain high manoeuvrability.
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Fieldwork in the Early Cretaceous Jehol Group, northeastern China has revealed a plethora of extraordinarily well-preserved fossils that are shaping some of the most contentious debates in palaeontology and evolutionary biology. These discoveries include feathered theropod dinosaurs and early birds, which provide additional, indisputable support for the dinosaurian ancestry of birds, and much new evidence on the evolution of feathers and flight. Specimens of putative basal angiosperms and primitive mammals are clarifying details of the early radiations of these major clades. Detailed soft-tissue preservation of the organisms from the Jehol Biota is providing palaeobiological insights that would not normally be accessible from the fossil record.
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We report on a new Mesozoic bird, Longirostravis hani, from the Early Cretaceous Jehol Biota of northeastern China. The new taxon has a long, slender rostrum and mandible, and a small number of rostralmost teeth. Postcranial characters such as a furcular ramus wider ventrally than dorsally, a centrally concave proximal margin of the humeral head, and a minor metacarpal that projects distally more than the major metacarpal, support the placement of Longirostravis within euenantiornithine Enantiornithes, the most diverse clade of Mesozoic birds. The morphology of the skull, however, suggests that Longirostravis had a probing feeding behavior, a specialization previously unknown for Enantiornithes. Indeed, this discovery provides the first evidence in support of the existence of such a foraging behavior among basal lineages of Mesozoic birds.
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Fossil bird skeletons discovered in Lower Cretaceous lake deposits in China shed new light on the early evolution of avian flight and perching. The 135 million-year-old sparrow-sized skeletons represent a new avian, Sinornis santensis, n. gen. n. sp., that preserves striking primitive features such as a flexible manus with unguals, a footed pubis, and stomach ribs (gastralia). In contrast to Archaeoperyx, however, Sinornis exhibits advanced features such as a broad sternum, wing-folding mechanism, pygostyle, and large fully reversed hallux. Modern avian flight function and perching capability, therefore, must have evolved in small-bodied birds in inland habitats not long after Archaeopteryx.
Conference Paper
Asia has greatly contributed to the recent burst of early Cretaceous birds. These numerous occurrences, however, are concentrated in the northeastern Chinese provinces of Liaoning and Hebei. We report on the discovery of an early Cretaceous bird from northern Gansu Province, in northwestern China, an occurrence that adds to the meager record of early Cretaceous birds from central Asia. Represented by a nearly complete left wing and shoulder girdle the size of a rock dove, the new bird was quarried from laminated green-gray mudstones of the Zhonggou/ Xiagou Formation (Xinmingu Group) near Changma, in the Jiuquan area. These deposits have previously yielded the only known specimen of Gansus yumenensis, the distal half of a hindlimb with long and slender digits. Several derived characters of the new occurrence supports its allocation within Enantiornithes:( 1) a convex lateral margin of the coracoid, (2) a minor metacarpal that projects distally more than the major metacarpal, and (3) a proximal phalanx of the major digit longer than the intermediate (second) phalanx. The general proportions of the wing suggest it was a flier comparable to most other known enantiornithine birds. Although direct comparisons between the new fossil and Gansus are not possible, the presence of a completely fused tarsometatarsus with a hypotarsus supports the placement of Gansus within Omithuromorpha, the clade that includes all living birds and the sister group of Enantiornithes. Thus, phylogenetic inferences based on the morphology of the only two known birds from the Xinmingu Group supports their placement into two different clades. The new occurrence thus adds to the taxonomic diversity of early Cretaceous birds from Gansu Province in particular and central Asia in general.
Article
A new Early Cretaceous enantiornithine bird, Eocathayornis walkeri, gen. et sp. nov. is reported from Liaoning, northeast China. It is about the size of Cathayornis but is more primitive. Teeth are present on the jaws. Claws are retained on three wing digits, but that of the minor digit is reduced. The width of the radius is nearly three-fourths that of the ulna. The sternum is relatively short, with a pair of long caudo-lateral processes and a low and caudally distributed keel. The coracoid is strut-like and caudally concave, typical of enantiornithine birds. The advanced features of the scapula and the wing suggest a powerful flapping flight capability. This bird is referred to the family Cathayornidae based on a few shared derived characters with Cathayornis.
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
A detailed description of the anatomy, in particular of the skull, of Eoenantiornis is provided. This description reveals many morphological characters previously unknown for enantiornithine birds, such as presence of a distinct facet for the intramandibular articulation between the dentary and postdentary bones. Eoenantiornis documents an intermediate stage in the abbreviation of the alular digit among Ornithothoraces, which paralleled a similar transformation within Ornithuromorpha. Our analysis also indicates that Eoenantiornis belongs to the Euenantiornithes.Une description détaillée de l'anatomie d'Eoenantiornis est présentée, plus particulièrement du crâne, qui révèle des caractères morphologiques jusqu'ici inconnus chez les oiseaux enantiornithines, tels que la présence d'une facette distincte de l'articulation intramandibulaire entre les os dentaire et post-dentaire. Eoenantiornis témoigne d'un stade intermédiaire de l'abréviation du doigt alulaire chez les Ornithothoraces qui s'inscrit parallèlement à une transformation semblable chez les ornithuromorphes. Notre analyse indique également qu'Eoenantiornis appartient aux Euenantiornithes.[Traduit par la Rédaction]
Article
Abstract  Enantionithine birds are the most blooming branch of early birds and have distinct diversities. A large number of enantionithine birds have been reported from the Early Cretaceous Jiufotang Formation in western Liaoning, China. Recently, we discovered a new eoenantiornithid bird from the Jiufotang Formation in Dapingfang Town, western Liaoning. A new eoenantiornithid bird, Dapingfangornis sentisorhinus gen. et sp. nov., is erected based on this complete skeleton with a skull. The new bird is distinguished from other known Mesozoic birds in a medium to small size, a distinct thorn-like process on the nasals, a sternum with a long and a short lateral processes. The thorn-like process on the nasal has not been discovered among known fossil birds, thus the discovery also provides new materials on the diversities of early birds.
Article
Dalingheornis liweii gen. et sp. nov., a new enantiornithine bird was collected from the early Cretaceous Yixian Formation in northeastern China. It is the first record of a highly specialized heterodactyl foot in Mesozoic birds. The Y-shaped furcula with short hypocleidum is different from that of other enantiornithines. The minor metacarpal is robust and longer than the major metacarpal. A long bony tail composed of 20 caudal vertebrae with chevrons resembling those of dromaeosaurids and thus, highlighting again the evolutionary relationship between birds and non-avian theropods. Well-preserved alula feathers and a heterodactyl foot provide strong evidence for the arboreal habit of Dalingheornis.
Article
Abstract A large number of enantiornithine birds are discovered from the Early Cretaceous Jiufutang Formation in western Liaoning, China. They are all small-sized birds with a few small teeth. The enantiornithine bird from the Jiufutang Formation in the Shangheshou area, Chaoyang, Liaoning Province reported in this paper is the largest individual known in all enantiornithine birds of the Early Cretaceous. However, its teeth possess a feature of pseudoheterodont. Some different development stages of the new teeth substitute the earlier stages and the stages of development are preserved in this specimen. This development pattern is similar to that of Archaeopteryx and alligator but not dinosaur. A well-developed postorbital was also preserved in the skull, which was a diapsidian skull like that of Confuciusornis. Additionally, the distinctive preservation of its prefrontal distinguishes it from other enantiornithine birds of the Early Cretaceous.