[PaleoOrnithology • 2026] Plumadraco bankoorum • Hyperelongate Ornamental Tail Feathers in A New early Cretaceous enantiornithine Bird

 

Plumadraco bankoorum

Clark, O’Connor, X. Wang, Y. Wang, Pruett-Jones, Zhang, X.Wang, Zheng & Zhou, 2026 

 

DOI: doi.org/10.1371/journal.pone.0347641

Illustration: Ville Sinkkonen

Abstract

Bird diversity is reflected in the abundance and variety of extraordinary plumages. Some of these include elongate, ornamental tail feathers that are typically attributed to either intraspecific communication in monomorphic species or sexual selection in sexually-dimorphic ones. Enantiornithines (Aves: Ornithothoraces) were the most diverse group of birds during the Cretaceous. Importantly, some enantiornithine fossils preserve soft tissues, most often in the form of feathers surrounding the body. Unlike any living bird, many enantiornithine specimens lack tail feathers (rectrices) all together, with the tail region consisting entirely of contour feathers. However, when present, enantiornithine rectrices typically consist of a pair of elongate, ornamental feathers with unusually wide rachises, referred to as rachis-dominated feathers. Here we describe Plumadraco bankoorum gen. et sp. nov., a new bohaiornithid enantiornithine with a pair of exceptionally long rectrices. These tail feathers measure twice the individual’s body length, ending in proportionally small pennaceous rackets, thus adding to the growing diversity of these unusual feathers. The fine preservation of these tail feathers, in comparison to other enantiornithine rectrices, reveals previously unrecognized structural variation that hints at their potential function in courtship displays. Although ornamental feathers in enantiornithines are widely considered sexually dimorphic, determining the selection pressures that shaped them is difficult due primarily to limited soft tissue data. Enantiornithine rectrices are likely the result of an interplay between both sexual and naturally selective pressures, similar to the processes which produce analogous structures in birds today.

Plumadraco bankoorum. The skull of STM11−4.
(A) Photo of fossil specimen and (B) a corresponding line drawing. Well preserved bones are colored white, crushed or poorly preserved bones (or portions of bones) are grey, and preserved soft tissues are brown.

Abbreviations: at, atlas; cev, cervical vertebrae; dn, dentary; fe, feathers; fp, frontal process of the premaxilla; fe, feather; fr, frontal; l, left; mx, maxilla; ns, nasal; pmx, premaxilla; pr, parietal; r, right; su, surangular; to, tooth. 

Scale bar 10 mm.

Plumadraco bankoorum. Specimen STM11−4 
(A) The holotype specimen of Plumadraco, (B) a closer view of the body and, (C) a line drawing of the same portion of the body shown in B. Well preserved bones are colored white, crushed or poorly preserved bones (or portions of bones) are grey, and preserved soft tissues are brown. The extent of the feather traces are denoted by the thin black outline around the body. Potential outline or crural feather present along the cranial face of the tibia.

Abbreviations: al, alula; cev, cervical vertebrae; co, coracoid; fm, femur; fu, furcula; hu, humerus; il, ilium; is, ischium; ma, manus; ph, phalanges (of the peds); pu, pubis; py, pygostyle; ri, rib(s); ra, radius; sc, scapula; sk, skull; sp, sternal plate; sy, synsacrum; tb, tibia; tmt, tarsometatarsus; tf, tail feathers; tv, thoracic vertebrae; ul, ulna. 

Scale bar (A, C) equals 50 mm.

Systematic paleontology

Aves Linnaeus, 1758

Pygostylia Chiappe et al., 2002  

Ornithothoraces Chiappe, 1995 

Enantiornithes Walker, 1981

Plumadraco bankoorum gen. et sp. nov.

Holotype. STM11−4 is a complete, articulated specimen preserved in a single slab primarily in dorsal aspect with feathers preserved around the head, body, wings, and tail.

Locality and horizon. Near Xiaotaizi Village, Jianchang County, Liaoning Province, Jiufotang Formation, 121 Ma (Lower Aptian). 

Diagnosis: Mid-sized [112–144 g, similar to some extant turdids (e.g., Cochoa, Turdus) and meliphagids (e.g., Anthochaera) enantiornithine (ventral margin of the furcula wider than dorsal margin; acrocoracoid, glenoid, and scapular cotyla omal-sternally aligned; minor metacarpal extending distally farther than the major metacarpal; metatarsal IV thinner than metatarsals II and III with the trochlea reduced to a single condyle; and a J-shaped metatarsal I), belonging to the family Bohaiornithidae (basally robust, apically tapered dentition; unforked dentary- surangular articulation; proportional width of the coracoid’s sternal margin; caudolateral projection of the sternal plate’s lateral trabeculae; well-developed abruptly terminating deltopectoral crest; robust pedal unguals), with the unique combination of the following features: corpus of the premaxillae dorsoventrally deeper than the dentaries; rostral ~80% of the dentary with parallel dorsal and ventral margins; tip of dentary is rostrodorsally tapered; at least nine sacral vertebrae; caudally-oriented lateral trabeculae of the sternum with asymmetrical, fan-shaped distal expansions; phalanx I of the manual digit craniocaudally thin; weakly curved pedal unguals; RDFs approximately twice body length.

Etymology. “Pluma”, Latin for feather, and “draco”, Latin for dragon. In the theme of avian biology and evolution, the specific name, “bankoorum”, honors Winston E. and Paul C. Banko. Together, their momentous life-long efforts have significantly contributed to our understanding of avian biology and conservation, particularly across the Hawaiian archipelago. Plumadraco bankoorum, the Banko’s feather dragon.

 B) Finely-preserved structures present in the proximal portion of the right RDF of Plumadraco bankoorum, C) and the preserved racket showing the differentiated barbs and the reduction, and eventual complete termination, of the central support structures (i.e., ramus and medial stripe). (D) The unique, undifferentiated barbs of the occipital plumes of Pteridophora alberti (King-of-Saxony Bird-of-Paradise) (FMNH 280831) forming tab-like laminated sheets. These structures may be uniquely analogous to the lateral margins (ribbon-like sheets) of enantiornithine RDFs preceding the distal ornaments.
 (E) An in-life restoration of Plumadraco. Illustration by Ville Sinkkonen.

  Results of phylogenetic analyses suggest Plumadraco belongs to the diverse Bohaiornithidae.

 

 male and female Plumadraco bankoorum

Illustration: Ville Sinkkonen

 Alexander D. Clark, Jingmai K. O’Connor, Xiaoli Wang, Yan Wang, Stephen Pruett-Jones, Xiangyu Zhang, Xing Wang, Xiaoting Zheng and Zhonghe Zhou. 2026. Hyperelongate Ornamental Tail Feathers in A New early Cretaceous enantiornithine Bird. PLoS One 21(5): e0347641. DOI: doi.org/10.1371/journal.pone.0347641 [May 27, 2026]

[PaleoOrnithology • 2024] Neobohaiornis lamadongensis • A New diminutive Species of bohaiornithid enantiornithine (Aves: Ornithothoraces) from the Lower Cretaceous Jehol Group, northern China

Neobohaiornis lamadongensis 

Shen, Clark, Fang, Chen, Jiang, Ji & O’Connor, 2024

DOI: doi.org/10.1038/s41598-024-82869-8 

Researchgate.net/publication/387498440

Abstract

Enantiornithes are the most successful early-diverging avian clade, their fossils revealing important information regarding the structure of Cretaceous avifaunas and the parallel refinement of flight alongside the ornithuromorph lineage that includes modern birds. The most diverse recognized family of Early Cretaceous enantiornithines is the Bohaiornithidae, known from the Jehol Biota in northeastern China. Members of this clade enhance our understanding of intraclade morphological diversity and elucidate the independent evolution of this unique lineage. Here, we report on a new specimen of bohaiornithid, Neobohaiornis lamadongensis gen. et sp. nov., from the Lower Cretaceous Jiufotang Formation in western Liaoning, China. The holotype specimen is considerably smaller than all other known bohaiornithids (roughly half the size of Bohaiornis). The presence of complete fusion in compound elements strongly suggests it represents a mature or nearly mature individual, and therefore substantially increases the known size range of this clade. This specimen further differs from known bohaiornithids in that it exhibits reduced manual unguals and an increased number of sacral vertebrae, which indicates bohaiornithids evolved increased flight capabilities in parallel to other enantiornithine lineages, such as the Longipterygidae. Traces of the plumage, which are rarely preserved in bohaiornithids, reveal the presence of remiges with rounded distal margins and short crural feathers.

 

Holotype of Neobohaiornis lamadongensis gen. et sp. nov. (MHGU-0288).
(A) Photograph; (B) line drawing.

al alular metacarpal, ce cervical vertebrae, co coracoid, d dentary, fr frontal, fe femur, fi fibula, fs fish, fu furcula, h humerus, hy hyoid, il illium, is ischium, mac major metacarpal, mic minor metacarpal, mt I-IV metatarsal I-IV, n nasal, pm premaxilla, pu pubis, py pygostyle, r radiale, sc scapula, st sternum, ti tibiotarsus, u ulna.

Plumage preserved in the holotype of Neobohaiornis lamadongensis gen. et sp. nov. (MHGU-0288).
(A) apices of the feathers extending from the caudal margin of the external nares down the neck; (B) distribution of crural feathers along the left tibiotarsus; (C) A pair of rachis-dominated rectrices (blue arrows); (D) The primary wing feathers preserved on the left wing. ms medial stripe, rd rachis in ‘rachis-dominated’ feathers.

Aves Linnaeus, 1758; [sensu Sereno, 1999].

Ornithothoraces Chiappe, 1995.

Enantiornithes Walker, 1981.

Bohaiornithidae Wang et al., 2014. 

Neobohaiornis lamadongensis gen. et sp. nov.

Diagnosis: Referrable to Enantiornithes based on the presence of the following diagnostic features: a furcula with a ventral margin wider than dorsal margin; a proportionately elongate hypocleidium of the furcula; minor metacarpal projecting distally farther than major metacarpal; metatarsal IV mediolaterally thinner than both metatarsals II and III with the trochlea reduced to a single condyle; and a J-shaped metatarsal I. Referred to the enantiornithine clade Bohaiornithidae based on the presence of  ...

Etymology: The generic name refers to the derived morphology (e.g., reduced alular digit, increased number of sacral vertebrae) of this taxon relative to other bohaiornithids. The specific name refers to the town of Lamadong, near where the fossil was found.

Caizhi Shen, Alexander D. Clark, Hui Fang, Shaokun Chen, Hongxia Jiang, Qiang Ji and Jingmai K. O’Connor. 2024. A New diminutive Species of bohaiornithid enantiornithine (Aves: Ornithothoraces) from the Lower Cretaceous Jehol Group, northern China. Scientific Reports. 14: 31363. DOI: doi.org/10.1038/s41598-024-82869-8

 Researchgate.net/publication/387498440_A_new_diminutive_species_of_bohaiornithid_enantiornithine_from_the_Cretaceous_Jehol_Group_northern_China

[PaleoOrnithology • 2024] Navaornis hestiae • Cretaceous Bird from Brazil informs the Evolution of the Avian Skull and Brain

Navaornis hestiae 

Chiappe, Navalón, Martinelli, Carvalho, Santucci, Wu & Field, 2024

 

 DOI: doi.org/10.1038/s41586-024-08114-4

Abstract

A dearth of Mesozoic-aged, three-dimensional fossils hinders understanding of the origin of the distinctive skull and brain of modern (crown) birds. Here we report Navaornis hestiae gen. et sp. nov., an exquisitely preserved fossil species from the Late Cretaceous of Brazil. The skull of Navaornis is toothless and large-eyed, with a vaulted cranium closely resembling the condition in crown birds; however, phylogenetic analyses recover Navaornis in Enantiornithes, a highly diverse clade of Mesozoic stem birds. Despite an overall geometry quantitatively indistinguishable from crown birds, the skull of Navaornis retains numerous plesiomorphies including a maxilla-dominated rostrum, an akinetic palate, a diapsid temporal configuration, a small cerebellum and a weakly expanded telencephalon. These archaic neurocranial traits are combined with a crown bird-like degree of brain flexion and a bony labyrinth comparable in shape to those of many crown birds but substantially larger. Altogether, the emergent cranial geometry of Navaornis shows an unprecedented degree of similarity between crown birds and enantiornithines, groups last sharing a common ancestor more than 130 million years ago. Navaornis provides long-sought insight into the detailed cranial and endocranial morphology of stem birds phylogenetically crownward of Archaeopteryx, clarifying the pattern and timing by which the distinctive neuroanatomy of living birds was assembled.

Systematic palaeontology

Aves Linnaeus, 1758

Ornithothoraces Chiappe and Calvo, 1994

Enantiornithes Walker, 1981

Navaornis hestiae gen. et sp. nov.

Remarks. We use Aves to refer to all taxa descended from the most recent common ancestor of Archaeopteryx lithographica and crown birds. 

Diagnosis. Enantiornithine with a toothless skull and a combination of the following features: fully fused premaxillae with a convex dorsorostral surface, highly curved jugal, small, comma-shaped quadratojugal, diminutive lacrimal failing to separate the orbit from the antorbital fenestra, parasphenoidal rostrum perforated by a large ovoid fenestra, elongate basipterygoid processes, large and sinusoidal anterior semicircular canal excavating the dorsal margin of the supraoccipital, robust and prominent medial process of the mandible.

Etymology. Navaornis honours William Nava, who discovered the fossil locality in 2004 and the holotype specimen in 2016; the specific epithet hestiae alludes to Hestia, the Greek goddess of architecture, regarded as simultaneously the oldest and the youngest of the Twelve Olympians. Navaornis reflects this duality in that it belongs to an archaic lineage, yet its cranial geometry is essentially modern. 

Luis M. Chiappe, Guillermo Navalón, Agustín G. Martinelli, Ismar de Souza Carvalho, Rodrigo Miloni Santucci, Yun-Hsin Wu and Daniel J. Field. 2024. Cretaceous Bird from Brazil informs the Evolution of the Avian Skull and Brain. Nature. 635, 376–381. DOI: doi.org/10.1038/s41586-024-08114-4

 

[PaleoOrnithology • 2024] Avisaurus darwini & Magnusavis ekalakaenis • New Enantiornithine Diversity in the Hell Creek Formation and the Functional Morphology of the avisaurid tarsometatarsus

Reconstruction of an avisaurid (e.g., Avisaurus  darwini). Morphology of the tarsometatarsus suggests that these large birds engaged in raptorial behavior and could carry proportionally large prey. 

 Clark, Atterholt, Scannella, Carroll & O’Connor, 2024

DOI: 10.1371/journal.pone.0310686

Illustration by Ville Sinkkonen.

Abstract

Enantiornithines were the most diverse group of birds during the Cretaceous, comprising over half of all known species from this period. The fossil record and subsequently our knowledge of this clade is heavily skewed by the wealth of material from Lower Cretaceous deposits in China. In contrast, specimens from Upper Cretaceous deposits are rare and typically fragmentary, yet critical for understanding the extinction of this clade across the K-Pg boundary. The most complete North American Late Cretaceous enantiornithine is Mirarce eatoni, a member of the diverse clade Avisauridae. Except for Mirarce, avisaurids are known only from isolated hindlimb elements from North and South America. Here we describe three new enantiornithines from the Maastrichtian Hell Creek Formation, two of which represent new avisaurid taxa. These materials represent a substantial increase in the known diversity of Enantiornithes in the latest Cretaceous. Re-examination of material referred to Avisauridae through phylogenetic analysis provides strong support for a more exclusive Avisauridae consisting of six taxa. Exploration of the functional morphology of the avisaurid tarsometatarsus indicates potential strong constriction and raptorial attributes. The lower aspect ratio of the tarsometatarsus facilitates a more biomechanically efficient lever system which in extant birds of prey equates to lifting proportionally heavier prey items. In addition, the proportional size and distal position of the m. tibialis cranialis tubercle of the tarsometatarsus is similar to the morphology seen in extant birds of prey. Together with the deeply-grooved metatarsal trochlea facilitating robust and likely powerful pedal digits, morphologies of the hindlimb suggest avisaurids as Late Cretaceous birds of prey.

Systematic paleontology

Aves Linnaeus, 1758

Pygostylia Chiappe, 2002

Ornithothoraces Chiappe, 1995

Enantiornithes Walker, 1981

The three fossil specimens (from left to right), Avisaurus  darwini, Avisaurus sp., and Magnusavis ekalakaensis, all of which are represented by a tarsometatarsus. They are all shown to scale with one another.  

Avisauridae Brett-Surman and Paul, 1985

Avisaurus Brett-Surman and Paul, 1985

Avisaurus darwini sp. nov.  

Etymology: The specific name “darwini” is in honor of Charles Darwin, whose momentous research and publications helped define the field of evolutionary biology. Avisaurus darwini, Darwin’s bird lizard.

Reconstruction of an avisaurid (e.g., Avisaurus  darwini). Morphology of the tarsometatarsus suggests that these large birds engaged in raptorial behavior and could carry proportionally large prey.

Illustration done by Ville Sinkkonen.

Magnusavis ekalakaenis gen. et sp. nov. 

Etymology: In Latin, “Magnus” meaning big, and “avis” meaning bird, and “ekalakaensis” in honor of the town of Ekalaka, Montana, close to where this specimen was discovered. Ekalaka is Lakota for “one who wanders”. Magnusavis ekalakaenis, Ekalaka’s big bird.

Phylogenetic placement of new Hell Creek enantiornithines based on cladistic analysis.
A) A subset of the strict consensus tree focusing on taxa around the Avisauridae, and B) the full 50% majority tree. In the majority tree, the newly diagnosed Avisauridae family is comprised of six taxa, two of which are described in this publication. C) A 1.8 m tall human to scale with A. darwini (maroon), the largest known Early Cretaceous enantiornithine Pengornis (black), a medium-sized early enantiornithine, Imparavis (white), and finally, a minuscule enantiornithine, Elektorornis (smaller inset black). The extant Buteo jamaicensis (Red-tailed Hawk) is shown in grey.

Alexander D. Clark, Jessie Atterholt, John B. Scannella, Nathan Carroll and Jingmai K. O’Connor. 2024. New Enantiornithine Diversity in the Hell Creek Formation and the Functional Morphology of the avisaurid tarsometatarsus. PLoS ONE. 19(10): e0310686. DOI: doi.org/10.1371/journal.pone.0310686

[PaleoOrnithology • 2024] Imparavis attenboroughi • First Edentulous Enantiornithine (Aves: Ornithothoraces) from the Lower Cretaceous Jehol Avifauna

Imparavis attenboroughi

  Wang, Clark, O'Connor, Zhang, Wang, Zheng & Zhou, 2024

DOI: 10.1016/j.cretres.2024.105867

Artwork: Ville Sinkkonen.

Abstract

Among Mesozoic birds, enantiornithines exhibit great morphological variation, which likely reflects their species diversity, range, and overall success throughout the Cretaceous. The majority of enantiornithines come from the Lower Cretaceous Jehol deposits (130–120 Ma) in northeastern China. In contrast to living birds, most enantiornithines were fully toothed. However, the rostral lengths, appendicular proportions, and pedal morphologies of extant birds can still inform on possible diet, flight mode, and ecology. Both partial (e.g., Longipterygidae) and complete tooth loss (e.g., Yuornis, Gobipteryx) are observed among enantiornithines, with edentulous rostra previously restricted to Upper Cretaceous taxa. Here, we describe the first edentulous enantiornithine from the Lower Cretaceous, Imparavis attenboroughi gen. et sp. nov., indicating a toothless beak evolved in this group 48 Ma earlier than previously recognized. Additionally, we reinterpret Chiappeavis as edentulous which together with the discovery of Imparavis indicates the complete loss of teeth in enantiornithines was not uncommon although still less frequent than observed in ornithuromorphs. The absence of gastroliths in all known enantiornithines suggests that the loss of teeth evolved under different pressures in these two ornithothoracine clades. Differences in rostral occlusion between Imparavis and Chiappeavis suggest they utilized different foraging strategies and possibly diet. Appendicular morphology in Imparavis suggest the capacity for relatively high wing beat frequency and powerful take-off capabilities. Together with the morphology of the hindlimb, we suggest Imparavis was primarily a terrestrial forager that could utilize sudden bursts of flight to escape into arboreal settings as a prey evasion strategy.

Illustration showing the fossil skeleton of Imparavis attenboroughi, alongside a reconstruction of the bird in life.

Artwork: Ville Sinkkonen.

Systematic paleontology

Aves Linnaeus, 1758

Pygostylia Chiappe, 2002

Ornithothoraces Chiappe, 1995

Enantiornithes Walker, 1981

Imparavis attenboroughi gen. et sp. nov.

Locality and horizon. Collected near the village of Toudaoyingzi, Jianchang County, Liaoning Province, PR China; Lower Cretaceous Jiufotang Formation, 120 Ma (Lower Aptian) (He et al., 2004; Pan et al., 2013).

Conclusions: 

Imparavis attenboroughi represents the first known edentulous enantiornithine from the Lower Cretaceous. The discovery of this taxon contributes to the multiple independent evolutionary occurrences of complete tooth loss among Mesozoic birds. The loss of teeth in enantiornithines may be linked to shifts in feeding behavior; however, as yet there is no evidence that this shift was driven by herbivory as is suggested for ornithuromorphs and non-avian dinosaurs. Rostral occlusion in Imparavis ....

Xiaoli Wang, Alexander D. Clark, Jingmai K. O'Connor, Xiangyu Zhang, Xing Wang, Xiaoting Zheng and Zhonghe Zhou. 2024. First Edentulous Enantiornithine (Aves: Ornithothoraces) from the Lower Cretaceous Jehol Avifauna. Cretaceous Research. 159, 105867. DOI: 10.1016/j.cretres.2024.105867

 

[PaleoOrnithology • 2023] Cratonavis zhui • Decoupling the Skull and Skeleton in A Cretaceous Bird with Unique Appendicular Morphologies

 Cratonavis zhui

 Li, Wang, Stidham & Zhou, 2023

 DOI: 10.1038/s41559-022-01921-w

Abstract

The Cretaceous is a critical time interval that encompasses explosive diversifications of terrestrial vertebrates, particularly the period when the earliest-branching birds, after divergence from their theropod ancestors, evolved the characteristic avian Bauplan that led eventually to their global radiation. This early phylogenetic diversity is overwhelmed by the Ornithothoraces, consisting of the Enantiornithes and Ornithuromorpha, whose members evolved key derived features of crown birds. This disparity consequently circumscribes a large morphological gap between these derived clades and the oldest bird Archaeopteryx. The non-ornithothoracine pygostylians, with an intermediate phylogenetic position, are key to deciphering those evolutionary transformations, but progress in their study has been hampered by the limited diversity of known fossils. Here we report an Early Cetaceous non-ornithothoracine pygostylian, Cratonavis zhui gen. et sp. nov., that exhibits a unique combination of a non-avialan dinosaurian akinetic skull with an avialan post-cranial skeleton, revealing the key role of evolutionary mosaicism in early bird diversification. The unusually elongated scapular and metatarsal one preserved in Cratonavis highlights a breadth of skeletal plasticity, stemming from their distinct developmental modules and selection for possibly raptorial behaviour. Mapped changes in these two elements across theropod phylogeny demonstrate clade-specific evolutionary lability.

   

Cratonavis zhui gen. et sp. nov.

 

Zhiheng Li, Min Wang, Thomas A. Stidham and Zhonghe Zhou. 2023. Decoupling the Skull and Skeleton in A Cretaceous Bird with Unique Appendicular Morphologies. Nature Ecology & Evolution. DOI: 10.1038/s41559-022-01921-w

www.eurekalert.org/news-releases/975492

[PaleoOrnithology • 2021] A Juvenile Specimen of Archaeorhynchus Sheds New Light on the Ontogeny of Basal Euornithines

Archaeorhynchus spathula Zhou & Zhang, 2006

in Foth, Wang, ... et Yang, 2021. 

DOI: 10.3389/feart.2021.604520 

Illustration: Frederik Spindler facebook.com/FrederikSpindler7

The ontogenetic development of extant birds is characterized by rapid growth, bone fusion and an early onset of flight ability. In contrast, little is known about how these ontogenetic traits evolved in the bird stem lineage, and the available data pertains primarily to Enantiornithes. Here, we describe an almost complete skeleton of a juvenile euornithine bird (LNTU-WLMP-18) from the Early Cretaceous Jiufotang Formation (Aptian), which was discovered near Lamadong Town (Jianchang County, Liaoning, China). Despite its completeness, bone preservation is rather poor. Thus, to increase the contrast between bone tissue and matrix, we used cyan-red-based autofluorescence photography. The specimen is more or less articulated and exposed in ventral aspect. The jaws are edentulous, the coracoid bears a procoracoid process, and the ischium lacks a proximodorsal process. The pedal unguals are short and barely curved, indicating a ground-dwelling lifestyle. Feathers, including long primaries, are present as carbonized traces. Several characters indicate that LNTU-WLMP-18 is a juvenile: the bone surface has a coarsely striated texture and no fusion is evident between the carpals and metacarpals, between the tibia and the astragalus and calcaneum, or among the metatarsals. Although juvenile characters have the potential to impede accurate identification of the specimen, morphological comparisons and cladistic analysis identify LNTU-WLMP-18 as most likely referable to the basal euornithine Archaeorhynchus, which would make the specimen the first juvenile bird from the Jehol Group that could be assigned to a specific taxon. Based on its size and the incomplete ossification of the bone surface, LNTU-WLMP-18 represents the smallest and therefore youngest known individual of this genus. A statistical comparison of limb proportions shows that the forelimbs of LNTU-WLMP-18 are significantly shorter than the hindlimbs, while the forelimbs are longer than the hindlimbs in subadult and adult individuals. This is different from the situation in some Enantiornithes, in which the forelimbs exceed the length of the hindlimbs even in hatchlings. Similar to Enantiornithes, Archaeorhynchus probably exhibit an early onset of flight ability, as indicated by the extensive wing plumage in LNTU-WLMP-18. Finally, the lack of gastroliths in the visceral cavity might indicate a dietary shift in Archaeorhynchus during ontogeny. As a small-bodied, ground-dwelling, seed-eating bird with a precocial ontogeny, Archaeorhynchus filled an ecological niche that later allowed early crown birds to survive the K-Pg mass extinction.

Keywords: Euornithes, ontogeny, Early Cretaceous, China, bird evolution

FIGURE 2. Overview of the skeleton of LNTU-WLMP-18.
 (A) LNTU-WLMP-18 under normal light. (B) LNTU-WLMP-18 under cyan-red autofluorescence. (C) Explanatory drawing of LNTU-WLMP-18.

 Anatomical abbreviations: cv cervicals; do dorsals; gc gastric content; lco left coracoid; lfe left femur; lhu left humerus; lil left ilium; lis left ischium; lma left metacarpus; lmt left metatarsus; lpd left pedal digits; lpu left pubis; lra left radius; lre left remiges; lsc left scapula; lti left tibia; lul left ulna; rfe right femur; rhu right humerus; ril right ilium; ris right ischium; rpd right pedal digits; rpu right pubis; rra right radius; rre right remiges; rsc right scapula; rti right tibia; rul right ulna; sac sacrum; sk skull. Scale bar 10 mm.

 

 Christian Foth, Shiying Wang, Frederik Spindler, Youhai Lin and Rui Yang. 2021. A Juvenile Specimen of Archaeorhynchus Sheds New Light on the Ontogeny of Basal Euornithines. Front. Earth Sci.  9:604520. DOI: 10.3389/feart.2021.604520

  facebook.com/FrederikSpindler7/posts/3917366061666504

[PaleoOrnithology • 2020] Khinganornis hulunbuirensis • A New Advanced Ornithuromorph Bird from Inner Mongolia documents the northernmost Geographic Distribution of the Jehol Paleornithofauna in China

Khinganornis hulunbuirensis

Wang, Cau, Kundrát, Chiappe, Ji, Wang, Li & Wu, 2020

DOI: 10.1080/08912963.2020.1731805 

 theropoda.blogspot.com

ABSTRACT

We describe a new taxon of advanced ornithuromorph bird, Khinganornis hulunbuirensis gen. et sp. nov., from the previously unreported Pigeon Hill locality of the Lower Cretaceous Longjiang Formation in the northern Greater Khingan Range area of Inner Mongolia, China. A cladistics analysis resolves K. hulunbuirensis as the sister group of a clade formed by Changzuiornis and Iteravis among ornithuromorphs. The osteohistological analysis indicates that K. hulunbuirensis is the first ornithuromorph that maintained an uninterrupted growth during a longer period characterised by slow deposition of low-vascularised and terminal avascular bone tissue. The relatively long hindlimbs and elongate pedal digits with long proximal phalanges suggest a wading and amphibious ecology for the new bird. The discovery of K. hulunbuirensis represents the first occurrence of Jehol birds in the Greater Khingan Range and documents the northernmost known geographic distribution of the celebrated avifauna in China. The new record implies more extended palaeogeographic range for the early diversification of Mesozoic birds on the eastern side of Laurasia.

KEYWORDS: Early Cretaceous, Longjiang formation, Jehol Biota, Ornithuromorpha, growth strategy

the holotype of Khinganornis hulunbuirensis gen. et sp. nov., SGM-AVE-2017001. A, slab-A; B, slab-B.

Abbreviations: ce, cervical vertebrae; co, coracoid; cv, caudal vertebrae; f, femur; fu, furcula; h, humerus; il, ilium; is, ischium; lr, left radius; lu, left ulna; ma, manus; pd, pedal digits; pu, pubis; rr, right radius; ru, right ulna; s, scapula; sk, skull; st, sternum; t, tibiotarsus; tm, tarsometatarsus. 

Scale bar = 2 cm.

Systematic palaeontology 

Class: Aves Linnaeus, 1758 

Pygostylia Chiappe, 2002 

Ornithothoraces Chiappe, 1995 

Ornithuromorpha Chiappe, 2002 

Genus: Khinganornis gen. nov.

 Type species: Khinganornis hulunbuirensis sp. nov. 

Derivation of name: The genus name is derived from the Greater Khingan Range in northeastern China, referring to the first fossil bird uncovered from the Greater Khingan Range at the time of publication. 

Khinganornis hulunbuirensis sp. nov.

Derivation of name: The species name refers to the fossil site located in Hulunbuir City.

Xuri Wang, Andrea Cau, Martin Kundrát, Luis M. Chiappe, Qiang Ji, Yang Wang, Tao Li and Wenhao Wu. 2020. A New Advanced Ornithuromorph Bird from Inner Mongolia documents the northernmost Geographic Distribution of the Jehol Paleornithofauna in China. Historical Biology: An International Journal of Paleobiology. DOI: 10.1080/08912963.2020.1731805 

 theropoda.blogspot.com/2020/02/khinganornis-wang-cau-kundrat-chiappe.html

[PaleoOrnithology • 2019] Elektorornis chenguangi • A New Enantiornithine Bird with Unusual Pedal Proportions Found in Amber

 Elektorornis chenguangi 

Xing, O’Connor, Chiappe, McKellar, Carroll, Hu, Bai & Lei, 2019

 DOI: 10.1016/j.cub.2019.05.077 

Illustration: Zhongda Zhang

Highlights: 

• New fossil is first avian species recognized from amber

• Elektorornis is distinct from all other birds based on the proportions of the foot

• Scutellae scale filaments on foot suggest probing function for elongated third toe

Summary

Recent discoveries of vertebrate remains trapped in middle Cretaceous amber from northern Myanmar have provided insights into the morphology of soft-tissue structures in extinct animals, in particular, into the evolution and paleobiology of early birds. So far, five bird specimens have been described from Burmese amber: two isolated wings, an isolated foot with wing fragment, and two partial skeletons. Most of these specimens contain the remains of juvenile enantiornithine birds. Here, we describe a new specimen of enantiornithine bird in amber, collected at the Angbamo locality in the Hukawng Valley. The new specimen includes a partial right hindlimb and remiges from an adult or subadult bird. Its foot, of which the third digit is much longer than the second and fourth digits, is distinct from those of all other currently recognized Mesozoic and extant birds. Based on the autapomorphic foot morphology, we erect a new taxon, Elektorornis chenguangi gen. et sp. nov. We suggest that the elongated third digit was employed in a unique foraging strategy, highlighting the bizarre morphospace in which early birds operated.

Keywords: Cretaceous, Cenomanian, Burma, Hukawng, stem Aves, Enantiornithes, ecology, feathers

 Tarsal with Integumentary Structures Preserved in Elektorornis chenguangi  HPG-15-2

Systematic Paleontology: 

Aves Linnaeus 1758 

Ornithothoraces Chiappe 1995 

Enantiornithes Walker 1981 

Elektorornis gen. nov. 

 Elektorornis chenguangi gen. et sp. nov.

Etymology: Elektorornis, ‘‘Elektor,’’ the word for amber; ‘‘-ornis,’’ Greek, meaning bird. The species name ‘‘chenguangi’’ is in honor of Chen Guang, a curator at the Hupoge Amber Museum.

 Lida Xing, Jingmai K. O’Connor, Luis M. Chiappe, Ryan C. McKellar, Nathan Carroll, Han Hu, Ming Bai and Fuming Lei. 2019. A New Enantiornithine Bird with Unusual Pedal Proportions Found in Amber. Current Biology. In Press.  DOI: 10.1016/j.cub.2019.05.077 

Bird with unusually long toes found fossilized in amber phys.org/news/2019-07-bird-unusually-toes-fossilized-amber.html via @physorg_com

[PaleoOrnithology • 2019] Avimaia schweitzerae • An Early Cretaceous Enantiornithine (Aves) Preserving An Unlaid Egg and Probable Medullary Bone

Avimaia schweitzerae 

Bailleul, O’Connor, Zhang, Li, Wang, Lamanna, Zhu & Zhou, 2019

DOI: 10.1038/s41467-019-09259-x 

Reconstruction by Michael Rothman 

Abstract

Understanding non-crown dinosaur reproduction is hindered by a paucity of directly associated adults with reproductive traces. Here we describe a new enantiornithine, Avimaia schweitzerae gen. et sp. nov., from the Lower Cretaceous Xiagou Formation with an unlaid egg two-dimensionally preserved within the abdominothoracic cavity. Ground-sections reveal abnormal eggshell proportions, and multiple eggshell layers best interpreted as a multi-layered egg resulting from prolonged oviductal retention. Fragments of the shell membrane and cuticle are both preserved. SEM reveals that the cuticle consists of nanostructures resembling those found in neornithine eggs adapted for infection-prone environments, which are hypothesized to represent the ancestral avian condition. The femur preserves small amounts of probable medullary bone, a tissue found today only in reproductively active female birds. To our knowledge, no other occurrence of Mesozoic medullary bone is associated with indications of reproductive activity, such as a preserved egg, making our identification unique, and strongly supported.

Fig. 1 Photograph and line drawing of the holotype of Avimaia schweitzerae, IVPP V25371.
a Photograph of the partial skeleton with feather impressions, and the crushed preserved egg between the pubes; b interpretive line drawing, with white arrows indicating the two fragments extracted for microscopic analysis with a super-imposed CT-scan revealing the egg and underlying elements of the right pelvis in dorsal (synsacrum) and medial (ilium) view.

Gray denotes bones (darker gray indicating poor preservation), blue denotes the egg, and dark gray denotes feather impressions.

 cv caudal vertebra, d digit, dp dorsal process, f fibula, fc fibular crest, fe femur, if ilioischiadic foramen, il ilium, is ischium, l left, mt metatarsal, p pedal phalanx, pu pubis, py pygostyle, r right, ri rib, sy synsacrum, tb tibiotarsus, tm tarsometatarsus, tv thoracic vertebra. 

Scale bar is 1 cm.

  Photograph of the holotype of Avimaia schweitzerae.

(Image by Barbara Marrs) 

Systematic paleontology

Aves Linnaeus, 1758

Pygostylia Chiappe, 2002

Ornithothoraces Chiappe, 1995

Enantiornithes Walker, 1981

Avimaia schweitzerae gen. et sp. nov.

Etymology: The generic name Avi- (bird) maia (mother) refers to the fact the specimen is a female preserved with an egg in the body cavity. Schweitzerae is in honor of Mary Higby Schweitzer for her ground-breaking works on MB and for her role in establishing the field of molecular paleontology.

Holotype: IVPP V25371 (Institute of Vertebrate Paleontology and Paleoanthropology), an articulated partial skeleton with some feather traces, consisting of the caudal half of the axial column, the pelvis, and the hind limbs, mostly exposed ventrolaterally (Fig. 1).

Locality and horizon: Near Changma Village, Yumen City, Gansu Province, northwestern China; Lower Cretaceous (lower–middle Aptian) Xiagou Formation10.

Diagnosis: Small-bodied enantiornithine (robust, cranially forked pygostyle, distal condyles of tibiotarsus contacting medially, J-shaped metatarsal I, metatarsal IV mediolaterally reduced relative to metatarsals III and IV, metatarsal IV trochlea reduced to single condyle) with the following autapomorphies: pubis delicate and strongly curved so that the caudal margin is concave throughout; distal end of ischium dorsally curved.

 Reconstruction of the Xiagou Formation with colonial nesting ground of Avimaia schweitzerae.
The female individual dead in the water on the left (with an unlaid egg not visible inside its abdomen), represents the fossilized individual described here.

(Image by Michael Rothman)

Alida M. Bailleul, Jingmai O’Connor, Shukang Zhang, Zhiheng Li, Qiang Wang, Matthew C. Lamanna, Xufeng Zhu and Zhonghe Zhou. 2019.  An Early Cretaceous Enantiornithine (Aves) Preserving An Unlaid Egg and Probable Medullary Bone. Nature Communications. volume 10, 1275. DOI: 10.1038/s41467-019-09259-x 

New Cretaceous Fossil Sheds Light on Avian Reproduction -    english.cas.cn/newsroom/research_news/201903/t20190320_207048.shtml 

New Cretaceous fossil sheds light on avian reproduction  eurekalert.org/e/933b via @EurekAlert