[Paleontology • 2026] Invictibellatrix amberina • A new megaraptoran dinosaur (Coelurosauria: Megaraptora) from the Lower Cretaceous Wessex Formation, UK, and its implications for theropod evolution and biogeography

 

 Invictibellatrix amberina
with contemporary fauna in the lower part of the Wessex Formation. 

Morrison, Scherer, Mannion, Porro, Clark, Folkes & Barrett, 2026

DOI: doi.org/10.1098/rsos.260937 

Artwork by Sergey Krasovskiy and Pedro Salas

Abstract

Theropod dinosaur remains from the Barremian (Lower Cretaceous) Wessex Formation of the Isle of Wight, UK, are rare and often fragmentary. Here, we present a previously undescribed braincase from this formation that represents a new coelurosaurian, Invictibellatrix amberina gen. et sp. nov. Phylogenetic analysis and comparative anatomy indicate that Invictibellatrix is distantly related to all previously named theropods from this stratigraphic unit. Theropod braincases are often regarded as morphologically and phylogenetically conservative, but we demonstrate that neurocranial characters provide essential data that can help clarify the phylogenetic relationships of theropods. The sub-circular occipital condyle, sub-oval foramen magnum and presence of a sagittal nuchal crest indicate that Invictibellatrix is referable to Megaraptora, with phylogenetic analyses recovering it as an early-diverging member of this clade, within a paraphyletic array of Eurasian taxa. Incorporation of Invictibellatrix into a biogeographical analysis suggests that non-megaraptorid megaraptorans likely had a cosmopolitan distribution in the Early Cretaceous, and that the absence of megaraptorans in the Late Cretaceous of Laurasia is best explained by regional extinction. The recognition of this new genus increases our knowledge of Early Cretaceous European coelurosaurian diversity, which now includes tyrannosauroids, maniraptoriforms and megaraptorans.

Keywords: megaraptora, endocast, Early Cretaceous, theropod, dinosaur, biogeography, Wessex Formation 

Systematic palaeontology

Dinosauria Owen, 1842

Saurischia Seeley, 1888

Theropoda Marsh, 1881

Tetanurae Gauthier, 1986

Coelurosauria Huene, 1914

Megaraptora

Photographs of the holotype braincase (NHMUK PV R6775) of Invictibellatrix amberina gen. et sp. nov. in A: anterior, B: posterior; C: right lateral; D: left lateral; E: ventral; F: dorsal views.

Abbreviations: atr, anterior tympanic recess; boc, basioccipital crest; bpr, basipterygoid recess; bsr, basisphenoid recess; bt, basal tubera; btw, basituberal web; CN, cranial nerves V, VII; cp, cultriform process; cvl, crista ventrolateralis of basisphenoid; fm, foramen magnum; oc, occipital condyle; ova, fenestra ovalis; pcr, paracondylar recess; pit, depression of the pituitary gland within the pituitary fossa; pp, paraoccipital process; prp, preotic pendant; psncr, parasagittal nuchal crest recess; scr, sub-condylar recess; snc, parasagittal nuchal crest; sok, supraoccipital knob; sta, sella turcica. Scale bar equals 50 mm.

Invictibellatrix amberina gen. et sp. nov.

Etymology: the generic name Invictibellatrix is derived from the Latin ‘invictus’ (‘unconquered’) and ‘bellatrix’ (‘warrior’ in the feminine form) and honours the future role of Megaraptora as Gondwanan apex predators, while early on in their evolutionary history they were smaller, non-apex predators [55–57]. This name is to give hope and strength to all those who are bullied, discriminated, victimized and oppressed that tomorrow will be theirs and not to give up in the face of such odds. The species epithet amberina is derived from the amber present in the plant debris beds of the Wessex Formation [58].

Locality and horizon: Sudmoor Point, near Brook, southwestern coast of the Isle of Wight, UK; Wessex Formation, Barremian, Lower Cretaceous. Most likely from the lower plant debris beds (L1 to L5).

Holotype: NHMUK PV R6775, a partial braincase.

Diagnosis: Invictibellatrix amberina can be diagnosed by the following unique character combination (autapomorphies marked with an asterisk): (i) *presence of a small basipterygoid recess anterior to the anterior tympanic recess (ATR) on each side of the parabasisphenoid, (ii) *slightly transversely compressed, hourglass-shaped nuchal crest, (iii) the presence of two large, deep and dorsoventrally elongate paracondylar recesses on the ventrolateral sides of the basioccipital, and (iv) *parasagittal nuchal crest recesses that are slightly curved and pronounced.

An artist's illustration of the new theropod dinosaur, Invictibellatrix amberina (center of the image), in its ecosystem on the Isle of Wight, United Kingdom, in the Early Cretaceous (around 120 million years ago). It lived in what was likely a seasonally wet-to-dry floodplain environment and is surrounded by other dinosaurs including large long-necked rebbachisaurid sauropods (directly behind Invictibellatrix, center) and relatives of Iguanodon (right). A spinosaurid theropod, potentially the apex predator of the time, fishes (left). Invictibellatrix has just caught and is consuming two small mammals. Gymnosperms dominate the environment as flowering plants (angiosperms) were not common at this time. Other reptiles including relatives of modern lizards, crocodiles and turtles enjoy the warm Early Cretaceous weather of the U.K.

Artwork by Sergey Krasovskiy and Pedro Salas

Cassius Morrison; Charlie R. Scherer; Philip Mannion; Laura B. Porro; Brett Clark; Daniel D. Folkes; Paul M. Barrett. 2026. A new megaraptoran dinosaur from the Lower Cretaceous Wessex Formation, UK, and its implications for theropod evolution and biogeography. R. Soc. Open Sci. 13(10): 260937. DOI: doi.org/10.1098/rsos.260937 [14 Oct 2026]

[Paleontology • 2026] Tromerosaurus solumons • A new albertosaurine from the Oldman Formation, Alberta, Canada, illuminates ambiguity between albertosaurine and tyrannosaurine characteristics

Tromerosaurus solumons

Powers, Napoli, Coppock, Sharpe, Garros, Demers-Potvin, Raun, Stock, Miyashita & Currie, 2026

 

DOI: doi.org/10.1080/02724634.2026.2728669

   x.com/Paleoartologist

 ABSTRACT

Tyrannosaurid species have often been considered to have high longevity and low diversity relative to contemporaneous megaherbivores. Recent chronospecies assertions around tyrannosaurid lineage evolution have reinforced this idea. An albertosaurine, Tromerosaurus solumons, from the Oldman Formation of Alberta, Canada, shares features with Daspletosaurus and Gorgosaurus, and prompts reassessment of tyrannosaurid characteristics and the Late Cretaceous radiation of Tyrannosauridae. Maxillary morphometrics reveal clear intermediate morphologies in Tromerosaurus between Daspletosaurus and Gorgosaurus, including an anteroposteriorly longer maxillary fenestra and narrower pila promaxillaris than in Gorgosaurus libratus. An anatomical diagnosis of Tromerosaurus solumons allowed referral of specimens previously attributed to Gorgosaurus. Restricted stratigraphic overlap between Tromerosaurus and Gorgosaurus offers support to this distinction. A modified recent character-taxon dataset recovers Tromerosaurus as the earliest diverging member of Albertosaurinae under parsimony or Tyrannosaurinae under Bayesian inference. The difference in topologies along with reduced node support values for clades such as Lythronax + Teratophoneus, or Bistahieversor and other derived tyrannosaurines, suggests uncertainty as to their recovery within Albertosaurinae or Tyrannosaurinae. Together, these results support a younger divergence of the two main tyrannosaurid lineages with rapid character acquisition and transition during the Late Cretaceous (Santonian–Maastrichtian).

SYSTEMATIC PALEONTOLOGY

THEROPODA, Marsh 1881

TYRANNOSAUROIDEA, Walker 1964

TYRANNOSAURIDAE, Osborn 1906

ALBERTOSAURINAE, Currie et al. 2003

Clade Definition—A group of tyrannosaurid theropods that are more closely related to Albertosaurus than Tyrannosaurus (Currie et al., 2003).

TROMEROSAURUS, gen. nov.

TROMEROSAURUS SOLUMONS, gen. et sp. nov.

Albertosaurus libratus TMP 1985.011.0003 (Table 1); Carr 1999

Gorgosaurus libratus TMP 1994.012.0602 and TMP 1995.005.0001 (Table 1); Currie 2003b.

Daspletosaurus torosus UALVP 52981 (Table 1); Rhodes et al. 2021.

Gorgosaurus libratus TMP 1985.011.0003 (Fig. 3B), TMP 1994.012.0602 (Figs. 3K, 7D and 8C), and TMP 1995.005.0001 (Fig. 5B); Voris et al. 2021.

Daspletosaurus UALVP 52981 (Table 1); Paul et al. 2022.

Etymology—The genus name derives from Ancient Greek for terrible or frightful (tromerós) lizard (saûros) with regard to the taxon having a mosaic of characteristics between Gorgosaurus (terrible lizard) and Daspletosaurus (frightful lizard). The specific epithet (solumons) derives from Latin for lonely (solus) and mountain (mons), pertaining to the isolation of the lacrimal horn by a broad flat shelf of the posterior process of the lacrimal. This also pays homage to the infamous fictional dragon Smaug (in particular, to his lair in The Hobbit (Tolkien, 1937), recognizing the visual similarities between tyrannosaurids and iconography of dragons.

 

Mark J. Powers, James G. Napoli, Colton C. Coppock, Henry S. Sharpe, Christiana W. Garros, Alexandre V. Demers-Potvin, Gorm S. Raun, Jordan C. Stock, Tetsuto Miyashita and Philip J. Currie . 2026. A new albertosaurine from the Oldman Formation, Alberta, Canada, illuminates ambiguity between albertosaurine and tyrannosaurine characteristics. Journal of Vertebrate Paleontology. e2728669. DOI: doi.org/10.1080/02724634.2026.2728669 [02 Oct 2026]

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[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]  

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[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] The coelurosaur theropods of the Romualdo Formation, early Cretaceous (Aptian) of Brazil: Santanaraptor placidus meets Mirischia asymmetrica

Hypothetical reconstruction of Mirischia asymmetrica (left) and Santanaraptor placidus (right) disputing a lizard in what is now northeastern Brazil ~112 million years ago (Early Cretaceous, Aptian).

Santanaraptor placidus Kellner, 1999 
Mirischia asymmetrica Naish, Martill & Frey, 2004

in Delcourt, Grillo, Hendrickx, Kellermann et Langer, 2025.

 Santanaraptor   Mirischia 

DOI: doi.org/10.1002/ar.70085 

Illustration by Guilherme Gehr. 

 

Abstract

The upper carbonate concretion levels of the Romualdo Formation (Aptian, Brazil) have yielded several theropod dinosaur remains, including spinosaurids and the coelurosaurs Santanaraptor placidus and Mirischia asymmetrica, the phylogenetic affinities of which are controversial. Here, we present a comprehensive anatomical reassessment of the holotypes of both species (MN 4802-V and SMNK 2349 PAL, respectively), integrating newly observed osteological features and a detailed comparison of the pelvic and hind limb elements. Our preferred phylogenetic hypothesis places S. placidus and M. asymmetrica in the earliest-branching maniraptoromorph clade, along with Juratyrant langhami and Tanycolagreus topwilsoni from the Late Jurassic of Laurasia, suggesting an early diversification of coelurosaurs in that area, followed by Early Cretaceous dispersal events towards Gondwana. The comparative analysis of the two Romualdo taxa refutes their synonymy, given consistent differences in ischial (position and shape of the obturator plate and foramen) and tibial (condylar configuration) morphology. The observed morphological variation in the ischial obturator plate across early coelurosaurs further highlights a significant degree of homoplasy in this structure during the early radiation of the group. This revision underscores the need for additional research to further resolve the early evolutionary history of coelurosaur theropods.

Keywords: Araripe, Coelurosauria, Dinosauria, Gondwana, Theropoda

Hypothetical reconstruction of Mirischia asymmetrica (left) and Santanaraptor placidus (right) disputing a lizard in what is now northeastern Brazil ~112 million years ago (Early Cretaceous, Aptian).

Illustration by Guilherme Gehr. 

Santanaraptor placidus Kellner, 1999

Mirischia asymmetrica Naish, Martill & Frey, 2004

CONCLUSIONS: 

The comprehensive reassessment of Santanaraptor placidus (MN 4802-V) and Mirischia asymmetrica (SMNK 2349) presented here offers new insights into the anatomy, taxonomy, and phylogenetic affinities of these two coelurosaur theropods from the Early Cretaceous (Aptian) Romualdo Formation of Brazil. Despite the minor overlapping of skeletal elements, both specimens exhibit consistent anatomical differences that support their recognition as distinct species. These differences are particularly evident in the configuration of the ischial obturator plate and the structure of the proximal tibial condyles.

Some of our phylogenetic results place S. placidus and M. asymmetrica together with Juratyrant langhami and Tanycolagreus topwilsoni, from the Late Jurassic of Laurasia, in a clade of early branching maniraptoromorphs. This is the first time that these Brazilian taxa are found closely related within a lesser-inclusive clade, corroborating previous assumptions of close biogeographic relations between Laurasian and Gondwanan landmasses by the Early Cretaceous. Further biogeographic patterns are, however, harder to define, especially having in mind the still patchy record of Jurassic theropods in areas such as Africa, Australia, India, Antarctica, and South America.

 

Rafael Delcourt, Orlando Nelson Grillo, Christophe Hendrickx, Maximilian Kellermann, Max Cardoso Langer. 2025. The coelurosaur theropods of the Romualdo Formation, early Cretaceous (Aptian) of Brazil: Santanaraptor placidus meets Mirischia asymmetrica. The Anatomical Record. DOI: doi.org/10.1002/ar.70085 [18 November 2025]

[Paleontology • 2025] Nanotyrannus and Tyrannosaurus coexisted at the close of the Cretaceous

Nanotyrannus   

in Zanno et Napoli, 2025.

 DOI: doi.org/10.1038/s41586-025-09801-6 

Artwork: Anthony Hutchings

 x.com/JGN_Paleo

Tyrannosaurus rex ranks among the most comprehensively studied extinct vertebrates1 and a model system for dinosaur paleobiology. As one of the last surviving non-avian dinosaurs, Tyrannosaurus is a crucial datum for assessing terrestrial biodiversity, ecosystem structure, and biogeographic exchange immediately preceding the end-Cretaceous mass extinction —one of Earth’s greatest biological catastrophes. Paleobiological studies of Tyrannosaurus, including ontogenetic niche partitioning, feeding, locomotor biomechanics, and life history have drawn upon an expanding skeletal sample comprising multiple hypothesized growth stages—and yet the Tyrannosaurus hypodigm remains controversial. A key outstanding question relates to specimens considered to exemplify immature Tyrannosaurus, which have been argued to represent the distinct taxon Nanotyrannus. Here, we describe an exceptionally well-preserved, near somatically mature tyrannosaur skeleton (NCSM 40000) from the Hell Creek Formation that shares autapomorphies with the holotype specimen of N. lancensis. We couple comparative anatomy, longitudinal growth models, observations on ontogenetic character invariance, and a novel phylogenetic dataset to test the validity of Nanotyrannus, demonstrating conclusively that this taxon is distinguishable from Tyrannosaurus, sits outside Tyrannosauridae, and unexpectedly contains two species—N. lancensis and Nanotyrannus lethaeus, sp. nov. Our results prompt a re-evaluation of dozens of existing hypotheses based on currently indefensible ontogenetic trajectories. Finally, we document at least two co-occurring, ecomorphologically distinct genera in the Maastrichtian of North America, demonstrating that tyrannosauroid alpha diversity was thriving within one million years of the end-Cretaceous extinction.

A pack of Nanotyrannus attacks a juvenile Tyrannosaurus rex.

Artwork: Anthony Hutchings

  Lindsay E. Zanno and James G. Napoli. 2025. Nanotyrannus and Tyrannosaurus coexisted at the close of the Cretaceous. Nature.  DOI: doi.org/10.1038/s41586-025-09801-6  [30 October 2025]

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[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 

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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

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[Paleontology • 2025] Khankhuuluu mongoliensis • A new Mongolian tyrannosauroid and the Evolution of Eutyrannosauria

Khankhuuluu mongoliensis 

Voris, Zelenitsky, Kobayashi, Modesto, Therrien, Tsutsumi, Chinzorig & Tsogtbaatar, 2025

DOI: doi.org/10.1038/s41586-025-08964-6

Abstract

Eutyrannosaurians were large predatory dinosaurs that dominated Asian and North American terrestrial faunas in latest Cretaceous times. These apex predators arose from smaller-bodied tyrannosauroids during the ‘middle’ Cretaceous that are poorly known owing to the paucity of fossil material. Here we report on a new tyrannosauroid, Khankhuuluu mongoliensis gen. et sp. nov., from lower Upper Cretaceous deposits of Mongolia that provides a new perspective on eutyrannosaurian origins and evolution. Phylogenetic analyses recover Khankhuuluu immediately outside Eutyrannosauria and recover the massive, deep-snouted Tyrannosaurini and the smaller, gracile, shallow-snouted Alioramini as highly derived eutyrannosaurian sister clades. Khankhuuluu and the late-diverging Alioramini independently share features related to a shallow skull and gracile build with juvenile eutyrannosaurians, reinforcing the key role heterochrony had in eutyrannosaurian evolution. Although eutyrannosaurians were mainly influenced by peramorphosis or accelerated growth, Alioramini is revealed as a derived lineage that retained immature features through paedomorphosis and is not a more basal lineage as widely accepted. Our results reveal that Asian tyrannosauroids (similar to Khankhuuluu) dispersed to North America, giving rise to Eutyrannosauria in the mid-Late Cretaceous. Eutyrannosauria diversified and remained exclusively in North America until a single dispersal to Asia in the latest Cretaceous that established Alioramini and Tyrannosaurini. Stark morphological differences between Alioramini and Tyrannosaurini probably evolved due to divergent heterochronic trends—paedomorphosis versus peramorphosis, respectively—allowing them to coexist in Asia and occupy different ecological niches.

Khankhuuluu mongoliensis gen. et sp. nov.

Jared T. Voris, Darla K. Zelenitsky, Yoshitsugu Kobayashi, Sean P. Modesto, François Therrien, Hiroki Tsutsumi, Tsogtbaatar Chinzorig and Khishigjav Tsogtbaatar. 2025. A new Mongolian tyrannosauroid and the Evolution of Eutyrannosauria. Nature. DOI: doi.org/10.1038/s41586-025-08964-6 [11 June 2025]

[Paleontology • 2025] Huadanosaurus sinensis & Sinosauropteryx lingyuanensis • Two New compsognathid-like Theropods (Coelurosauria: Sinosauropterygidae) show diversified predation strategies in Theropod Dinosaurs

Huadanosaurus sinensis gen. et sp. nov. and
Sinosauropteryx lingyuanensis sp. nov.  

 Qiu, Wang, Jiang, Meng & Zhou, 2025

 DOI: doi.org/10.1093/nsr/nwaf068 

 illustrated by ZHAO Chuang facebook.com/PNSOus

ABSTRACT

The Compsognathidae was originally considered an early-diverging clade of coelurosaur theropods. However, recent study suggests that Compsognathidae is not monophyletic. Here, we describe two new compsognathid-like species, Sinosauropteryx lingyuanensis sp. nov. and Huadanosaurus sinensis gen. et sp. nov. from the Lower Cretaceous Yixian Formation of Dawangzhangzi (Lingyuan, Western Liaoning, China). The phylogenetic results indicate that all compsognathid-like theropods from the Early Cretaceous Jehol Biota form a monophyletic group Sinosauropterygidae nested among early-diverging coelurosaurs. Morphological comparison between various species of sinosauropterygids from the Early Cretaceous of Northeast China, combined with the phylogenetic results, suggests that at least three distinct hunting strategies were present among coeval species. The diversification of theropods should be attributed to the landscape caused by the destruction of the North China craton.

Early Cretaceous, Jehol Biota, Yixian Formation, Sinosauropterygidae, North China craton

Holotype of Huadanosaurus sinensis gen. et sp. nov. (IVPP V 14202: a, b) and
Sinosauropteryx lingyuanensis sp. nov. (IVPP V 12415:c, d).
Photographs and line drawings.
Black shading indicates the impression made by the skeleton. Dark grey shading indicates the mammalian bony stomach content.

 f, furcula; lc, left coracoid; lf, left femur; lh, left humerus; li, left ilium; lis, left ischium; lmt, left metatarsal; ls, left scapula; lt, left tibia; lu, left ulna; pu, pubis; rc, right coracoid; rd, right dentary; rf, right femur; rh, right humerus; ri, right ilium; ris, right ischium; rmc, right metacarpal; rmt, right metatarsal; rr, right radius; rs, right scapula; rt, right tibia; ru, right ulna. Scale bar, 10 cm.

Dinosauria Owen, 1842

Saurischia Seeley, 1888

Theropoda Marsh, 1881

Coelurosauria Von Huene, 1914

Sinosauropterygidae Ji et Ji, 1996

Sinosauropteryx Ji et Ji, 1996

Sinosauropteryx lingyuanensis sp. nov

Diagnosis. Differs from other sinosauropterygids in possessing the following autapomorphies: the jugal ramus of the maxilla subequal to the length of the snout; maxilla relatively low and elongated, maxillary fenestra large and subequal in size to the external naris; absence of the ischiatic boot.

Huadanosaurus sinensis gen. et sp. nov.

Diagnosis. Differs from other sinosauropterygids in possessing the following autapomorphies: large oval concavity between the anterior margin of the antorbital fossa and the maxilla; large lacrimal recess on the lacrimal, U-shaped bifurcation at the posteroventral margin of the dentary, small and crescent-shaped external mandibular fenestra, fanshaped neural spine on the axis, strongly anteroposteriorly elongated centrum in the posterior cervical vertebrae, small pleurocoel on centrum of the anterior dorsal vertebrae, the coracoid elongated lateromedially, not oval-shaped, the supracetabular crest well developed on the ilium, the obturator process >70% of the length of the ischial shaft, and the tibia ∼1.3 times of the femoral length.

Etymology. ‘Huadan’, a Chinese word meaning the birthday of a great person or a great institution, commemorating the 75th anniversary of the founding of the People’s Republic of China and the Chinese Academy of Sciences, the 95th anniversary of the founding of the Palaeontological Society of China and the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and the 40th anniversary of the founding of the Chinese Society of Vertebrate Paleontology; ‘saurus’, Greek for lizard. ‘sine’, Latin referring to China. 

Huadanosaurus sinensis (left) and Sinosauropteryx lingyuanensis (right)

 illustrated by ZHAO Chuang

Rui Qiu, Xiaolin Wang, Shunxing Jiang, Jin Meng and Zhonghe Zhou. 2025. Two New compsognathid-like Theropods show diversified predation strategies in theropod dinosaurs. National Science Review, Volume 12(5); nwaf068. DOI: doi.org/10.1093/nsr/nwaf068 [22 February 2025]

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[Paleontology • 2025] Duonychus tsogtbaatari • Didactyl therizinosaur (Coelurosauria: Therizinosauridae) with a preserved keratinous claw from the Late Cretaceous of Mongolia

 

Duonychus tsogtbaatari

Kobayashi, Zelenitsky, Fiorillo & Chinzorig, 2025

 

www.cell.com/iscience/fulltext/S2589-0042(25)00401-8  

illustration by Masato Hattori

Highlights: 

• Duonychus tsogtbaatari is described as another therizinosaur from Mongolia

• It is a didactyl therizinosaur, possessing only two manual digits

• A keratinous sheath on digit I provides rare insight into theropod claw structure

• Duonychus reveals convergent digit III loss in at least five theropod clades

Summary

Therizinosaurs were a group of herbivorous/omnivorous theropod dinosaurs that lived in Asia and North America during the Cretaceous Period. These theropods are notable for their three-fingered hands sporting large claw-like unguals. Here, we describe a new and unusual species of the therizinosaurid Duonychus tsogtbaatari, recovered from the lower Upper Cretaceous Bayanshiree Formation of the Gobi Desert of Mongolia. This species is different from other therizinosaurs in that the hand possesses only two fingers, rather than three fingers, the typical condition for Avetheropoda, providing further insight into forelimb/hand reduction among theropods. Phylogenetically, Duonychus reveals a broader but still limited appearance of didactyly among avetheropodans. The manual ungual of Duonychus tsogtbaatari also preserves a nearly complete three-dimensional structure covering the ungual of the left manual digit I, which represents a keratinous manual claw. The strong curvature of this large claw and high ungual flexion indicate that Duonychus was likely amplectorial (grasping) and an effective grasper of vegetation, despite having only two functional fingers.

Systematic Paleontology

Theropoda  

Coelurosauria  

Therizinosauria  

Therizinosauridae 

 

Duonychus tsogtbaatari gen. et sp. nov.

 

Horizon and locality: The holotype specimen was collected from the Urlibe Khudak Locality (N43°27.092′, E107°23.476′) within the Bayanshiree Formation (Figure 1), which primarily consists of conglomerates, sandstones, and mudstones deposited in alluvial and fluvial settings, in the eastern Gobi Desert, Mongolia. This formation, dated to the Late Cretaceous, spans the Cenomanian to Santonian stages, as indicated by radiometric dating and biostratigraphic data. ...

Diagnosis: A derived therizinosaur exhibiting the following unique combination of characters: dorsal vertebrae with a long neural spine; a thick centrodiapophyseal lamina without additional laminae; dorsal vertebrae lacking pleurocoels; sacral vertebrae (2–4) with flat ventral surfaces; dorsal vertebrae possessing a weak ventral keel; pneumatic dorsal ribs; fused distal carpals 1 and 2; distal carpals 1 and 2 semilunate-shaped with a mediodorsal process; a small angle between the articular surfaces of the radiale for the semilunate carpal and the radius; a reduced metacarpal III forming a splint; absence of digit III; equally sized manual unguals I-2 and II-3; absence or reduction of the flexor fossa in manual phalanges; and a reduced dorsal process at the proximal end of manual phalanges. Duonychus can be distinguished from other therizinosaurs of the Bayanshiree Formation by several features. Its humerus has a more proximally positioned deltopectoral crest compared to Erlikosaurus, and in Duonychus, the entepicondyle is reduced with a markedly narrow groove separating it from the ulnar condyle. Unlike Enigmosaurus, which has a fused pubic boot and coalesced sacral vertebrae, Duonychus has an unfused pubic boot and ventrally flat sacral vertebrae with a shorter second sacral. Duonychus has an anteriorly deflected humeral shaft and a nearly straight ventral border of the pubic boot, distinguishing it from the convex shape seen in Segnosaurus.

Etymology: The generic epithet is derived from duo for two in Greek in reference to the presence of a didactyl hand which is unusual in therizinosaurs, and from onyx for claw in Greek. The species epithet honors Khishigjav Tsogtbaatar, a paleontologist and former director of the Institute of Paleontology, Mongolian Academy of Sciences in Ulaanbaatar, Mongolia.

 

Yoshitsugu Kobayashi, Darla K. Zelenitsky, Anthony R. Fiorillo and Tsogtbaatar Chinzorig. 2025. Didactyl therizinosaur with a preserved keratinous claw from the Late Cretaceous of Mongolia.  iScience. www.cell.com/iscience/fulltext/S2589-0042(25)00401-8  

DOI: 10.1016/j.isci.2025.112141 [March 25, 2025]