[Paleontology • 2026] Norellraptor barsboldi • Independent Assembly of the Flight Apparatus in A Non-avian Dinosaur Clade

  

 Norellraptor barsboldi 

Wang, Ji, Cau, Kundrát, Liu, Wang & Ji, 2026

 DOI: doi.org/10.1038/s41467-026-77804-6

Abstract

The discovery of feathered dinosaurs revolutionized the studies on the origin of birds and the evolution of their flight. Among paravians (birds and their closest relatives), the microraptorine dromaeosaurids are unique in bearing several flight-related adaptations with a controversial evolutionary interpretation, supporting, alternatively, flight as ancestral to Paraves or having evolved multiple times among the latter. Here, we introduce an exquisitely-preserved member of Microraptorinae, Norellraptor barsboldi gen. et sp. nov., and describe in detail forelimb osteohistological features for that clade. Norellraptor nests among late-diverging microraptorines and supports step-wise assembly of aerial adaptations in that clade. About 30% of the microraptorine synapomorphies are convergently acquired by the bird lineage (Avialae). Yet, the sequences of flight-related novelties reconstructed along the two lineages differ consistently; combined with histological evidence which might indicate a peculiar limb growth model in Microraptorinae, these results dismiss a shared developmental pattern driving the evolution of the flying dinosaurs and support multiple and independent selective regimes at the origin of the winged taxa in Paraves.

 Norellraptor barsboldi 130108-MHGU-F4281
a Whole specimen. b Skull in lateral view. c Close up of the rostrum. d Close up of the posterior part of skull. e Pectoral region. f Distal end of tail.

aof, antorbital fossa; arm, ascending ramus of maxilla; at, anterior tympanic recess; bt, basal tuber; bp, basypterygoid process; cf, coracoid fenestra; ct, caudal tympanic recess; cnV, 5th cranial nerve opening; cnVII, 7th cranial nerve opening; cv, cervical vertebra; d1, first dorsal vertebra; de, dentary; dt, dorsal tympanic recess; fo, foramen; fr, frontal; fu, furcula; gl, glenoid; h, humerus; la, lacrimal; lat, laterosphenoid; lcv, last caudal vertebra; lp, lateral pneumatic recess; mc, metacarpus; mxf, maxillary fenestra; na, nasal; oc, otosphenoid crest; or, otic region; pa, parietal; paw, postantral wall; pmx, premaxilla; pp, paroccipital process; ppd, posterior processes of dentary; pt, pterygoid; pxf, promaxillary fenestra; r, radius; rp, retroarticular process; sa, surangular; sc, scapula; so, supraoccipital; sp, sternal plate; sr, sclerotic ring; u, ulna; up, uncinate process; vor, ventral otic recess. 

Arrow indicates point of histological sampling. 

Scale bar = 50 mm (a); 10 mm (b–f).

 Norellraptor barsboldi 130108-MHGU-F4281, appendicular elements.
a Right hand. b Pubis. c Feet.

am, acetabular margin; ap, apron; cs, claw soft tissue; gi, gastral impression; mcI-III, metacarpals I to III; mtI-V, metatarsals I to V; p, phalanx; pf, pubic foot; r, radius; sc, semilunate carpal; t, tibiotarsus; u, ulna; uI-III, unguals 1 to 3. 

Scale bar = 10 mm.

Systematic palaeontology

Dinosauria Owen, 1842 

Theropoda Marsh, 1881 

Dromaeosauridae Matthew and Brown, 1922  

Microraptorinae Senter et al., 2004 

Microraptorini (Senter et al., 2004) 

Norellraptor barsboldi gen. et sp. nov.

Locality and horizon: Lamadong Town, Jianchang County, western Liaoning, China. Jiufotang Formation, Lower Cretaceous. China.

Diagnosis: Microraptorine dromaeosaurid with the unique combination of features (autapomorphies marked by asterisk; Supplementary Fig. 2): premaxilla with length of prenarial part half the depth of the subnarial body; large promaxillary fenestra occupying the whole rostral third of the antorbital fossa*, and with long axis inclined 35° caudodorsally; pila promaxillaris narrower than the pila interfenestralis and both less than half the diameter of the maxillary fenestra*; pubis gently curved caudoventrally with small foot having the posterior projection less than the diameter of the pubic shaft*. Differential diagnosis: Norellraptor differs from Changyuraptor in having basally-constricted dentary crowns and in the semilunate carpal barely

 

Etymology: The genus name refers to the American palaeontologist Mark Allen Norell (1957-2025), with Latin word “raptor” (“robber”), a frequently used suffix in dromaeosaurid taxonomy. The species name refers to the Mongolian palaeontologist Rinchen Barsbold (1935-2025). The new taxon name remarks and honours the exceptional contributions by R. Barsbold and M. A. Norell to the study of the bird-like dinosaurs.

 

Xuri Wang, Yannan Ji, Andrea Cau, Martin Kundrát, Yichuan Liu, Yang Wang and Qiang Ji. 2026. Independent Assembly of the Flight Apparatus in A Non-avian Dinosaur Clade. Nature Communications. 17: 10074. DOI: doi.org/10.1038/s41467-026-77804-6 [29 September 2026]

[Paleontology • 2026] Kayrasaurus changliensi • A New therizinosaur from the Early Cretaceous Jehol Biota and ecomorphological patterns among early therizinosaurians

 

Kayrasaurus changliensis  Liao, Freimuth, Zanno & Xu, 2026;

Beipiaosaurus inexpectus; Jianchangosaurus yixianensis; Lingyuanosaurus sihedangensis

DOI: doi.org/10.1080/14772019.2026.2710287 

Artwork by Kōhei Futaka. x.com/_HETAKA

 

Abstract

Therizinosauria is a highly specialized clade of maniraptoran theropods, notable for a suite of unusual traits in late-branching taxa. These paradoxical anatomical features contributed to the complex taxonomic history of the clade, which remained unresolved until the discovery of early branching taxa. Here, we describe a new early branching species, Kayrasaurus changliensis, based on a nearly complete, skeletally immature specimen (IVPP V 18597) recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China. This taxon is notably larger than other penecontemporaneous Jehol therizinosaurians (at least 1.6 times larger than the second-largest taxon, Beipiaosaurus inexpectus) and exhibits a unique combination of features (e.g. extremely small and densely packed teeth, cervical centra markedly longer than dorsal centra, and a dorsally extended ‘lip’ on manual ungual IV). We evaluate the phylogenetic position of K. changliensis using an expanded dataset with increased character and taxon sampling. Our results allow us to revise the diagnosis of B. inexpectus and provide new insights into therizinosaurian evolution, provisionally recovering two subclades within Therizinosauridae that are differentiated by their manual ungual morphology. By integrating morphological traits, body mass estimates, and biomechanical data, we infer the possibility of at least two distinct ecological niches among Jehol therizinosaurians. One ecological group, represented by B. inexpectus and possibly K. changliensis, exhibits features indicative of enhanced bite force and a more robust, less cursorial body plan. In contrast, Jianchangosaurus yixianensis and Lingyuanosaurus sihedangensis display traits associated with greater cursoriality and a reliance on forelimb-based foraging. Kayrasaurus changliensis, together with the results of our phylogenetic analysis, provides new insights into the morphological evolution and ecological adaptations of therizinosaurians in the Jehol Biota. However, further analyses and the discovery of more complete, well-preserved specimens are essential to rigorously test and refine these hypotheses. 

Keywords: Early Cretaceous, Liaoning, maniraptoran, morphology, taxonomy

four species of therizinosaurids from the Jehol Biota, China: 
Kayrasaurus changliensis; Beipiaosaurus inexpectus;
Jianchangosaurus yixianensis; Lingyuanosaurus sihedangensis

Artwork by Kōhei Futaka.  x.com/_HETAKA

Systematic palaeontology

Dinosauria Owen, 1842

Theropoda Marsh, 1881

Coelurosauria sensu Gauthier, 1986

Therizinosauria Russell and Dong, 1993

Kayrasaurus changliensis gen. et sp. nov.

Etymology. Kayra, the god of creation in Turkic Shamanism, is the father of Erlik, the god of death, symbolizing its phylogenetic connection to Erlikosaurus; saurus, Greek for lizard. The specific name changliensis is derived from Changli, a historical place name from the Three Kingdoms period, referring to the provenance of the fossil.

Horizon and locality. Dabangou village, Sihetun Area, near Beipiao City, Liaoning Province, P. R. China; Lower Cretaceous (Barremian–Aptian) Yixian Formation (Chang et al., 2017).

Chun-Chi Liao, William J. Freimuth, Lindsay E. Zanno and Xing Xu. 2026. A New therizinosaur from the Early Cretaceous Jehol Biota and ecomorphological patterns among early therizinosaurians. Journal of Systematic Palaeontology. 24(2); 2710287. DOI: doi.org/10.1080/14772019.2026.2710287 [10 Sep 2026]  

x.com/_HETAKA/status/2098404378852102507

[Paleontology • 2026] Zhengheornis buyu • Jurassic Avialan reveals stepwise Evolution of Bony Tail in Birds

Zhengheornis buyu

Wang, Tang, Deng, Dong, L. Xu, X. Xu, M. Lin,  Du, G. Lin, Chen, Zhang & Zhou, 2026 

 

DOI: doi.org/10.1126/sciadv.aeb5202 

Abstract

The evolutionary assembly of the flight-adapted bird body plan encompasses some of the most profound morphological changes in terrestrial vertebrate history. Beyond feathered wings, the short pygostyle-bearing tail has been pivotal to the clade’s ecological success. However, transition from the long bony tail to the short pygostyle-bearing tail remains a mystery, hindered by the scarcity of early branching avialans with transitional morphologies. Here, we report on a new avialan, Zhengheornis buyu, gen. et sp. nov., from the Upper Jurassic of southeastern China, suggesting that the vertebral reduction and shortening preceded pygostyle fusion in early avialan evolution, providing critical evidence for the stepwise evolution of the bird tail. Z. buyu is smaller than all known non-pygostylian paravians, expanding the species and body size diversity of stemward taxa.

Systematics

Theropoda Marsh, 1881  

Maniraptora Gauthier, 1986  

Avialae Gauthier, 1986 

Zhengheornis buyu gen. et sp. nov. 

Etymology: “Zhenghe” (Mandarin), referring to Zhenghe Country, where the holotype specimen was found; “ornis,” bird (Greek); “buyu,” unexpected (Mandarin), from the ancient Chinese book Guoyu, referring to the unique tail and pelvic morphologies preserved in this species. 

Holotype: Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) V34168, an articulated and partially complete skeleton (most limb bones are preserved as molds) with feathers preserved on a slab and counter slab (Fig. 1, figs. S1 and S2, and table S1). 

Locality and horizon: Near Yangyuan Village, Zhenghe Country, Nanping City, Fujian Province; Upper Jurassic, Nanyuan Formation [Tithonian stage]. 

Diagnosis: IVPP V34168 is distinguishable from all other paravians in the following combination of characters (*denotes probable autapomorphy): short tail comprising 15 vertebrae that is shorter than the hindlimb (combined length of femur, tibia, and metatarsal III)*; middle and posterior caudal vertebrae less elongate (opposite to the condition in other long tailed avialans); final two caudal vertebrae box-like*; manual phalanx III-1 shorter than III-2, opposite to the condition in Archaeopteryx and Fujianvenator [the three manual digits of maniraptorans are here identified as I, II, and III, as in (Tamura, et al. 2011)]; manual phalanx III-3 50% longer than III-2 (the length ratio greater than 2 in Anchiornis and Archaeopteryx); slender ischium that has a knob-like, distally located obturator process and lacks the posterior process*; short fibula that terminates far proximal to the ankle; metatarsal I that articulates at the distal third of metatarsal II; metatarsal II that ends far proximal to metatarsal III trochlea; short hallux with an ungual that is smaller than that of other pedal digits; and robust digit II that has the longest non-ungual (II-2) and ungual pedal phalanges.

 

Min Wang, Jianrong Tang, Ke Deng, Liping Dong, Liming Xu, Xing Xu, Min Lin, Honggang Du, Ganmin Lin, Runsheng Chen, Chi Zhang and Zhonghe Zhou. 2026. Jurassic Avialan reveals stepwise Evolution of Bony Tail in Birds. Science Advances. 12(27); DOI: doi.org/10.1126/sciadv.aeb5202 [1 Jul 2026]

[Paleontology • 2026] Jian changmaensis • First non-Avian Theropod (Dromaeosauridae: Microraptorinae) from the Bird-bearing Lower Cretaceous Xiagou Formation of the Changma Basin, Gansu Province, Northwestern China

 

Jian changmaensis 

Zhou, Lamanna, Poust, Li, You & O’Connor, 2026

attacks the early bird Gansus yumenensis 

  

 facebook.com/CarnegieMNH 

 illustration by Lewis LaRosa  x.com/LewisLaRosa, colorized by Jão Canola.

ABSTRACT

Lacustrine sediments of the Lower Cretaceous (lower Aptian) Xiagou Formation exposed near the village of Changma in the Changma Basin of northwestern Gansu Province, China have yielded more than 100 avian partial skeletons, many of which also preserve remnants of soft tissues such as feathers and skin. Collectively, these fossils characterize a rich avifauna dominated by the crownward ornithuromorph Gansus yumenensis Hou and Liu, 1984. Despite this wealth of Early Cretaceous bird material, no skeletal remains of other dinosaurs have been described from Changma to date. Here we report the first non-avian dinosaur body fossil from the Xiagou Formation of the Changma Basin. Consisting of an articulated left pectoral girdle and forelimb lacking the carpus and manus, the specimen pertains to a new dromaeosaurid theropod taxon, Jian changmaensis, gen. et sp. nov. Phylogenetic analysis recovers Jian within Microraptorinae, expanding the definitive fossil record of this clade to include northwestern China. The new Changma microraptorine constitutes an additional similarity between the theropod faunas of the Xiagou Formation of the Changma Basin and penecontemporaneous strata of the Jehol Group of northeastern China. In particular, the Changma theropod assemblage closely resembles that of the Sihedang locality of the Jehol Group in that both include representatives of Microraptorinae and are overwhelmingly dominated by single ornithuromorph taxa that phylogenetic analyses have repeatedly resolved as close relatives. This raises the possibility that the two sites were deposited under comparable paleoenvironmental settings that are otherwise poorly represented at known Jehol localities. 

Key Words: Early Cretaceous, Gansus yumenensis, Jian changmaensis, microraptorine, paleobiogeography, paleoenvironment, phylogeny, Sihedang 

SYSTEMATIC PALEONTOLOGY 

Dinosauria Owen, 1842 

Saurischia Seeley, 1888 

Theropoda Marsh, 1881 

Maniraptora Gauthier, 1986 

Dromaeosauridae Matthew and Brown, 1922 

Microraptorinae Xu, 2002 

Holotype of Jian changmaensis, gen. et sp. nov. (GSGM-D050), an articulated partial left pectoral girdle (scapulocoracoid) and forelimb (humerus, radius, and ulna). A, silhouette of generalized microraptorine dromaeosaurid theropod (courtesy Scott Hartman) showing skeletal elements preserved; B, photograph of specimen as preserved, exposed primarily in dorsomedial (scapulocoracoid), caudodorsal (humerus), and dorsal (radius and ulna) views; C, interpretive line drawing of B; D, detail photograph of scapulocoracoid and proximal end of humerus in caudodorsal view, showing supracoracoid fenestra and other structures; E, interpretive line drawing of D.

Abbreviations: ac, acromion; bc, bicipital crest; C, coracoid; cr, caudal ridge; dep, dorsal epicondyle; dpc, deltopectoral crest; dr, dorsal ridge; ed, epicondylar depression; fs?, fossa for M. supinator?; H, humerus; hh, humeral head; lp, lateral process; ‘mb’, ‘medial bar’; op, olecranon process; R, radius; S, scapula; scb, scapular blade; scf, supracoracoid fenestra; sta, sternal articulation; U, ulna.

Jian changmaensis, gen. et sp. nov.

Diagnosis.—Medium-sized (intermediate in skeletal dimensions between adult specimens of Microraptor zhaoianus and Sinornithosaurus millenii Xu et al., 1999; see Table 2) microraptorine dromaeosaurid theropod characterized by the following three autapomorphies: (1) a coracoid that is proportionally longer relative to the humerus than in any other microraptorine (~36% humerus length; the next closest individuals are the immature Microraptor IVPP V31612, with a value of ~35%, and IVPP V12811, the holotype of Sinornithosaurus, with a value of 33%) (Table 2); (2) humeral distal condyles developed on the cranial surface of this bone (Figs. 2B–C, 3E; a local autapomorphy within Microraptorinae, shared with nonmicroraptorine theropods such as the therizinosaur Erlikosaurus andrewsi Barsbold and Perle, 1980, and Aves); and (3) a well-developed foramen on the ventral aspect of ...

Etymology.—The genus name is for the Jiān (鹣), a one winged bird in Chinese mythology, in reference to the bird-like, possibly volant nature of this microraptorine taxon and the skeletal composition of its holotype (an isolated partial pectoral girdle and forelimb). The specific name is for Changma (昌马), the locality where the holotype was discovered.

 The new microraptor dinosaur Jian changmaensis (left) attacks the early bird Gansus yumenensis (right) in what is now the Changma Basin of northwestern China approximately 120 million years ago. 

 illustration by Lewis LaRosa  x.com/LewisLaRosa,
colorized by Jão Canola.

Ling-Qi Zhou, Matthew C. Lamanna, Ashley W. Poust, Da-Qing Li, Hai-Lu You and Jingmai K. O’Connor. 2026. First non-Avian Theropod (Dromaeosauridae, Microraptorinae) from the Bird-bearing Lower Cretaceous Xiagou Formation of the Changma Basin, Gansu Province, Northwestern China. ANNALS OF CARNEGIE MUSEUM. 92(2); 89–110. [4 June 2026]

https://carnegiemnh.org/wp-content/uploads/2026/06/Jian-changmaensis-Annals-of-Carnegie-Museum.pdf

 facebook.com/CarnegieMNH/posts/1431015332396739

 x.com/LewisLaRosa/status/2062606679980556631

[Paleontology • 2026] Xenovenator espinosai • A Thick-Skulled Troodontid Theropod (Maniraptora: Troodontidae) from the Late Cretaceous of Mexico

 

Xenovenator espinosai 

Rivera-Sylva, Aguillón-Martinez, Flores-Ventura, Sánchez-Uribe, Guzman-Gutierrez & Longrich, 2026

DOI: doi.org/10.3390/d18010038

Abstract

Dinosaurs repeatedly evolved adaptations for sexual selection over their 150-million year history, including adaptations for display and intraspecific combat. Adaptations for intraspecific combat have not previously been described in non-avian maniraptorans. We report a troodontid from the Campanian Cerro del Pueblo Formation of Coahuila, Mexico, showing a thickened and domed skull roof. The cranium is domed and bones are extremely thick, a morphology convergent on that of Pachycephalosauridae. Referred specimens show less thickening or doming, suggesting ontogenetic changes or perhaps sexual dimorphism. The holotype shows fusion of the frontal midline suture and tightly interdigitating sutures between skull bones, and a rugose skull roof. The specializations seen here suggest adaptation for intraspecific combat, specifically head-butting as hypothesized for pachycephalosaurids and pachyrhinosaurin ceratopsids. Repeated evolution of elaborate weapons and display features in the Cretaceous suggests that sexual selection became increasingly important in dinosaur evolution during the Cretaceous.

Keywords: Dinosauria; Theropoda; Maniraptora; Troodontidae; Cretaceous; Campanian; Laramidia; sexual selection; intraspecific combat

Saurischia Seeley, 1888 

Theropoda Marsh, 1881  

Avetheropoda Paul, 1988  

Coelurosauria Von Huene 1914  

Maniraptora Gauthier 1986  

Deinonychosauria Colbert and Russell, 1969 

Troodontidae Gilmore, 1924  

Troodontinae van der Reest and Currie, 2017 

Troodontini n. tax.

Xenovenator gen. nov.

Diagnosis. Troodontid characterized by thick frontals, anterior displacement of frontal postorbital processes relative to the parietal suture, broad and transversely arched interfrontal ridge, broad frontal-lacrimal suture.

Etymology. Greek xenos, ‘strange’ + Latin venator, ‘hunter’.

Xenovenator espinosai sp. nov. 

Holotype. CPC 2973, braincase including frontals, parietals, orbitosphenoids, laterosphenoids, exoccipitals, prootics, basisphenoid, basioccipital (Figure 4, Figure 5, Figure 6, Figure 7 and Figure 8).

 

Etymology. The species name honors Luis Espinosa, a pioneer in the study of Mexican dinosaurs and mentor to many generations of paleontologists.

Diagnosis. Xenovenator characterized by the following characters (* = autapomorphy): frontals extensively fused; frontals, parietals, and other cranial bones with strongly interdigitating sutures *; strong doming of frontals *; frontals and parietals massive (up to 12 mm thick) *, thickening well-developed anteriorly and less well-developed in the center of the frontal *; dorsal surface of frontals and parietals rugose and striated *, nasal processes broad between lacrimals *, orbital fossae widely separated ventrally *, frontal with notch and shelf to receive posterior end of lacrimal, parietal forms narrow process inserting between frontals *; triangular parietal table *, anteroventral expansion of the orbitosphenoids and laterosphenoids to enclose braincase ventrally *.

Horizon and Locality. Cerro Del Pueblo Formation, uppermost/latest Campanian (Figure 3), Coahuila, Mexico. CPC 2973 and CPC 3112 are from the La Parrita locality, 54 km west of Saltillo; municipality of General Cepeda, Coahuila, Mexico. CPC 3112 is from the Ejido Trincheras locality, 109 km west of Saltillo, municipality of Parras de la Fuente, Coahuila, Mexico (Figure 2).

 Hector E. Rivera-Sylva, Martha C. Aguillón-Martinez, Jose Flores-Ventura, Ivan E. Sánchez-Uribe, Jose Ruben Guzman-Gutierrez and Nicholas R. Longrich. 2026. A Thick-Skulled Troodontid Theropod from the Late Cretaceous of Mexico. Diversity. 18(1), 38. DOI: doi.org/10.3390/d18010038 [9 January 2026]

 

[Paleontology • 2025] Shri rapax • A New bird-like Dinosaur from the Upper Cretaceous of Mongolia with extremely robust hands supports niche partitioning among velociraptorines

Shri rapax

Moutrille, Cau, Chinzorig, Escuillié, Tsogtbaatar, Ganzorig, Mallet & Godefroit, 2025

DOI: doi.org/10.1080/08912963.2025.2530148  

  theropoda.blogspot.com 

  facebook.com/TheropodaBlog

 

ABSTRACT

Dromaeosauridae is a clade of bird-like theropod dinosaurs including, among others, the genera Deinonychus and Velociraptor, and characterised by a specialised second toe bearing an enlarged and falciform ungual. Here, we describe an exquisitely-preserved velociraptorine dromaeosaurid from the Upper Cretaceous Djadokhta Formation of Mongolia, and refer it to the new species Shri rapax. This dromaeosaurid is diagnosed by a peculiar combination of vertebral and pelvic features and by an exceptionally robust hand with a very stout pollex bearing the ungual proportionally larger than in any other dromaeosaurid. Combined with cranial adaptations which could support a bite more powerful than in other velociraptorines, the enlarged unguals in both Shri species suggest ecological partitioning in prey preference among the sympatric Djadokhtan dromaeosaurids.

KEYWORDS: Cretaceous, Djadokhta Formation, Dromaeosauridae, Mongolia, Theropoda

Shri rapax

 

 

Léa Moutrille, Andrea Cau, Tsogtbaatar Chinzorig, François Escuillié, Khishigjav Tsogtbaatar, Bayasgaa Ganzorig, Christophe Mallet and Pascal Godefroit. 2025. A New bird-like Dinosaur from the Upper Cretaceous of Mongolia with extremely robust hands supports niche partitioning among velociraptorines. Historical Biology: An International Journal of Paleobiology. DOI: doi.org/10.1080/08912963.2025.2530148 [13 Jul 2025] 

  theropoda.blogspot.com/2025/07/move-over-velociraptor-its-shri-rapax.html

  facebook.com/TheropodaBlog/posts/1329586105840132

[Paleontology • 2025] Chicago Archaeopteryx informs on the early Evolution of the Avian Bauplan

Chicago Archaeopteryx 

in O’Connor, Clark, Kuo, Kiat, Fabbri, Shinya, Van Beek, Lu, Wang et Hu, 2025.

DOI: doi.org/10.1038/s41586-025-08912-4 

 facebook.com/JingmaiOConnor 

artwork by Lewis LF LaRosa (color by Adrienne Stroup)

Abstract

Here we report on the nearly complete and uncrushed 14th specimen of Archaeopteryx. Exceptional preservation and preparation guided by micro-computed tomographic data make this one of the best exemplars of this iconic taxon, preserving important data regarding skeletal transformation and plumage evolution in relation to the acquisition of flight during early avian evolution. The ventrolaterally exposed skull reveals a palatal morphology intermediate between troodontids and crownward Cretaceous birds. Modifications of the skull reflect the shift towards a less rigid cranial architecture in archaeopterygids from non-avian theropods. The complete vertebral column reveals paired proatlases and a tail longer than previously recognized. Skin traces on the right major digit of the hand suggest that the minor digit was free and mobile distally, contrary to previous interpretations. The morphology of the foot pads indicates that they were adapted for non-raptorial terrestrial locomotion. Specialized inner secondary feathers called tertials are observed on both wings. Humeral tertials are absent in non-avian dinosaurs closely related to birds, suggesting that these feathers evolved for flight, creating a continuous aerodynamic surface. These new findings clarify the mosaic of traits present in Archaeopteryx, refine ecological predictions and elucidate the unique evolutionary history of the Archaeopterygidae, providing clues regarding the ancestral avian condition.

Chicago Archaeopteryx 

artwork by Lewis LF LaRosa 

(color by Adrienne Stroup)

 

Jingmai O’Connor, Alexander Clark, Pei-Chen Kuo, Yosef Kiat, Matteo Fabbri, Akiko Shinya, Constance Van Beek, Jing Lu, Min Wang and Han Hu. 2025. Chicago Archaeopteryx informs on the early Evolution of the Avian Bauplan. Nature. DOI: doi.org/10.1038/s41586-025-08912-4 [14 May 2025] 

 facebook.com/JingmaiOConnor/posts/29428682216775738

[Paleontology • 2024] Eoneophron infernalis • A New oviraptorosaur (Theropoda: Oviraptorosauria: Caenagnathidae) from the end-Maastrichtian Hell Creek Formation of North America

Eoneophron infernalis

Atkins-Weltman, Simon, Woodward, Funston & Snively, 2024

DOI: 10.1371/journal.pone.0294901

Illustration by Zubin Erik Dutta  facebook.com/ZDuttaArt

Abstract

Caenagnathidae is a clade of derived, Late Cretaceous oviraptorosaurian theropods from Asia and North America. Because their remains are rare and often fragmentary, caenagnathid diversity is poorly understood. Anzu wyliei is the only caenagnathid species currently described from the late Maastrichtian Hell Creek Formation of the USA and is also among the largest and most completely preserved North American caenagnathids. Smaller, less complete caenagnathid material has long been known from the Hell Creek Formation, but it is unclear whether these are juvenile representatives of Anzu or if they represent distinct, unnamed taxa. Here, we describe a relatively small caenagnathid hindlimb from the Hell Creek Formation, and conduct osteohistological analysis to assess its maturity. Histological data and morphological differences from Anzu wyliei and other caenagnathids allow us to conclude that this specimen represents a new species of caenagnathid from the Hell Creek Formation, with a smaller adult body size than Anzu. This new taxon is also distinct from other small caenagnathid material previously described from the area, potentially indicating the coexistence of three distinct caenagnathid species in the Hell Creek Formation. These results show that caenagnathid diversity in the Hell Creek ecosystem has been underestimated.

Systematic paleontology

Theropoda Marsh 1878 

Oviraptorosauria Barsbold 1976 

Caenagnathidae Sternberg 1940 

Eoneophron gen. nov. 

Eoneophron infernalis sp. nov.

 

Holotype: CM 96523, partial hindlimb including right femur, right tibia and astragalocalcaneum, a right metatarsal III, and a right metatarsal IV.

Diagnosis: Caenagnathid oviraptorosaur diagnosed by the following combination of traits (autapomorphies are denoted with an asterisk): femoral head directed dorsomedially, rather than perpendicular to the shaft; astragalocalcaneum fused to tibia*, metatarsal III with well-developed posterior cruciate ridges continuous with the distal condyle; distal condyle of metatarsal III transversely wider than anteroposteriorly deep, with medial portion of condyle larger than lateral portion; proximal end of metatarsals III and IV project posteriorly to form proximal protuberance; distal tarsal IV coossified with the proximal end of metatarsal IV at maturity; shaft of metatarsal IV with well-developed oblique longitudinal ridge on anterior surface extending along the distal three-quarters of the shaft*.

Etymology: Genus name derived from the Ancient Greek “eo”–meaning “dawn,” and from the genus name of the Egyptian vulture, Neophron, sometimes referred to as the “pharaoh’s chicken.” The species name derives from Latin for Hell, in reference to the Hell Creek Formation. Together the taxon name equates to “Pharaoh’s dawn chicken from Hell.”

Locality and horizon: Collected from exposures of the upper Maastrichtian Hell Creek Formation, Meade County, South Dakota, United States of America. The specimen was prepared prior to acquisition, but matrix remains adhered to some areas, such as the proximal portion of the tibia and anterodistal region of the femur. These sediments resemble those of typical floodplain deposits such as siltstones with organic material as seen elsewhere in the Hell Creek Formation (KLAW, pers. obs.).

Artist’s depiction of Eoneophron infernalis (top left), MOR 752 (bottom left), and Anzu wyliei (right) in the Hell Creek Formation.

Illustration by Zubin Erik Dutta.

 Kyle L. Atkins-Weltman, D. Jade Simon, Holly N. Woodward, Gregory F. Funston and Eric Snively. 2024. A New oviraptorosaur (Dinosauria: Theropoda) from the end-Maastrichtian Hell Creek Formation of North America. PLoS ONE. 19(1): e0294901. DOI: 10.1371/journal.pone.0294901

 facebook.com/ZDuttaArt/posts/822554889885490

[Paleontology • 2023] Jaculinykus yaruui • A New alvarezsaurid Dinosaur (Theropoda: Alvarezsauria) from the Upper Cretaceous Baruungoyot Formation of Mongolia provides insights for Bird-like Sleeping behavior in Non-avian Dinosaurs

Jaculinykus yaruui

Kubo, Kobayashi, Chinzorig & Tsogtbaatar, 2023

 

DOI: 10.1371/journal.pone.0293801

Artwork courtesy of Seiji Yamamoto

 

Abstract

Alvarezsauria is a group of early-branching maniraptoran theropods that are distributed globally from the Late Jurassic to the latest Cretaceous. Despite recent increases in the fossil record of this group, the scarcity of complete specimens still restricts interpreting their detailed anatomy, ecology, and evolution. Here, we report a new taxon of derived alvarezsaur, Jaculinykus yaruui gen. et sp. nov., from the Late Cretaceous of Mongolia, which represents a nearly complete and articulated skeleton. Our phylogenetic analysis reveals that Jaculinykus belongs to the sub-clade of Alvarezsauridae, Parvicursorinae, and forms a mononphyletic group with Mononykus and Shuvuuia. Its well-preserved manus has only two fingers, composed of a hypertrophied digit I and greatly reduced digit II, which implies an intermediate condition between the tridactyl manus of Shuvuuia and monodactyl manus of Linhenykus. This highlights a previously unrecognized variation in specialization of alvarezsaurid manus. Notably, the preserved posture of the specimen exhibits a stereotypical avian-like sleeping position seen in the troodontids Mei and Sinornithoides. Evidence of this behavior in the alvarezsaur Jaculinykus suggests that stereotypically avian sleeping postures are a maniraptoran synapomorphy, providing more evidence of bird-like traits being distributed broadly among avian ancestors.

Geographic and stratigraphic occurrence of the Mongolian alvarezsaurids.
(C) The stratigraphic horizon of  Jaculinykus yaruui gen. et sp. nov. and other alvarezsaurids in the Nemegt, Baruungoyot, and Djadokhta formations. The composite stratigraphy was modified from Eberth [2018] and Jerzykiewicz and Russell [1991].

Geographic and stratigraphic occurrence of the Mongolian alvarezsaurids.
(A) Plan view of Mongolia. (B) Location of Jaculinykus yaruui gen. et sp. nov. (MPC-D 100/209) and alvarezsaurid occurrences in the Nemegt Basin. The map was generated using Simplemappr (www.simplemappr.net) before modification and modified from Jerzykiewicz et al. [2021]. 

Holotype of Jaculinykus yaruui gen. et sp. nov. (MPC-D 100/209).
(A) Photograph of the specimen. (B) Explanatory drawing of (A). Highlighted areas refer to the indication of the skeletal elements; skull in green, tail in grey, pectoral girdle and forelimbs in red, pelvis and hind limbs in purple.
(C) Reconstruction of Jaculinykus yaruui gen. et sp. nov. Grey areas are missing parts.

Life restoration of sleeping posture of Jaculinykus yaruui

 (Artwork courtesy of Seiji Yamamoto)

Systematic paleontology

Dinosauria Owen, 1842  

Theropoda Marsh, 1882 

Maniraptora sensu Gauthier, 1986  

Alvarezsauria Bonaparte, 1991  

Alvarezsauridae Bonaparte, 1991  

Parvicursorinae Karhu and Rautian, 1996  

Jaculinykus yaruui gen. et sp. nov.

 

Etymology: Jaculinykus is from “Jaculus,” a tiny dragon from the Greek myth, and “onykus,” claw; yaruui, derived from Mongolian word, yaruu (яаруу): speedy (= hasty).

Holotype: The type specimen (MPC-D 100/209) is a nearly complete skeleton with a skull, missing some cranial elements (vomers, nasals, postorbitals, and supraoccipitals), eighth or ninth cervical vertebra, posterior dorsal vertebrae, seven anterior caudal vertebrae, sternum, furcula, right manual phalanx (II-2), right manual ungual and left fibula (Fig 2). It is housed in the Institute of Paleontology of Mongolian Academy of Sciences (IP-MAS), Ulaanbaatar, Mongolia.

Type locality and horizon: Nemegt locality, Ömnögovi Province, Mongolia (Fig 1). The specimen was collected from the upper section of the Baruungoyot (or Barun Goyot) Formation, suggested as the Campanian in age, (Fig 1). The stratigraphic horizon of Jaculinykus belongs to a part of “Big Red” in the transitional stratigraphic interval (Zone 4).

Diagnosis: Jaculinykus differs from all other alvarezsaurs in having a dorsoventrally high narial opening of the premaxilla, medially curved parasagittal crest on the parietal, slender and nearly straight dentaries, triangular-shaped deltopectoral crest being separated from the humeral head by a notch, strong medial tab of metacarpal I, weakly developed proximodorsal process of phalanx I-1, robust medial condyle of the tibia relative to the fibular condyle, and sharply indented base of the ascending process of astragalus. Jaculinykus is also distinguished from other alvarezsaurs by the unique combination of the following characters: slender ischial shaft relative to the pubic shaft, an open popliteal fossa of the femur, and prominent external projection of the ectocondylar tuber of the femur. It differs from the hypothesized sister taxon Shuvuuia deserti in possessing the following additional features: the deltopectoral crest being separated from the humeral head by a notch; the absence of the third manual digit. It also differs from stratigraphically same or older (the Baruungoyot Formation) alvarezsaurid, Ondogurvel alifanovi, from the same locality (the Nemegt locality) in possessing the following features ....

Evolution of avian-like sleeping posture in theropod dinosaurs. Skeletal disposition of Jaculinykus yaruui gen. et sp. nov. (MPC-D 100/209) in dorsal (photograph courtesy of Tomonori Tanaka) (A) and ventral (reversed) (B) views. (C), Interpretive line drawing of skeletal disposition.
 (D), Life restoration of sleeping posture of Jaculinykus yaruui (Artwork courtesy of Seiji Yamamoto).
(E), Simplified coelurosaurian phylogeny represents presence for evidence of avian ‘tuck-in’ posture.

 Kohta Kubo, Yoshitsugu Kobayashi, Tsogtbaatar Chinzorig and Khishigjav Tsogtbaatar. 2023. A New alvarezsaurid Dinosaur (Theropoda, Alvarezsauria) from the Upper Cretaceous Baruungoyot Formation of Mongolia provides insights for Bird-like Sleeping behavior in Non-avian Dinosaurs. PLoS ONE. 18(11): e0293801. DOI: 10.1371/journal.pone.0293801