[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] Kank australis • New unenlagiid (Theropoda: Unenlagiidae) from the Chorrillo Formation (Late Cretaceous, Maastrichtian), SW Patagonia, Argentina

 

Kank australis

Motta, Rolando, Rozadilla, Agnolín, Egli, Herrera, Chimento, Coco, Tsuihiji, Manabe, Pol & Novas, 2026

 

DOI: doi.org/10.1080/02724634.2026.2656456 

A reconstruction by Gabriel Díaz Yantén

 

ABSTRACT

Unenlagiids constitute a group of paravian theropods up to now represented in Gondwanan landmasses. They are particularly diverse in northern Patagonia, where at least seven species were discovered in Upper Cretaceous beds. In southern Patagonia, by contrast, the record is restricted to a few isolated remains of indeterminate taxa from Argentina and Chile. The aim of the present contribution is to describe an unenlagiid, Kank australis gen. et sp. nov. from the Maastrichtian beds of southern Santa Cruz, southern Patagonia, Argentina. Kank australis is represented by vertebrae, isolated pedal phalanges, and shed teeth. The holotype individual has a unique combination of characters, including a highly pneumatized cervical vertebra with well-developed parapophysis and carotid processes. Further, a pedal phalanx II-2 resembles those of troodontids due the reduction of the distal condyles, and differs from other known unenlagiids. The apomorphic condition of the few available elements suggests that Kank australis was probably distinct from its kin and reinforces the hypothesis that Unenlagiidae was a morphologically disparate clade.

SYSTEMATIC PALEONTOLOGY

DINOSAURIA OWEN, 1842

SAURICHIA SEELEY, 1888

THEROPODA MARSH, 1881

PARAVES SERENO, 1997

UNENLAGIIDAE (Bonaparte, 1999)

KANK AUSTRALIS gen. et sp. nov.

Diagnosis—Medium-sized unenlagiid (phalanges similar in size to Neuquenraptor argentinus estimated in ∼27 kg; Motta, 2023) showing the following combination of characters (autapomorphies marked by an asterisk): (1) dentary teeth having mesial carinae restricted to the apical third of the crown (shared with Austroraptor); (2) labiolingually compressed maxillary teeth “8” in cross-section (shared with Buitreraptor); (3) dentary teeth having a crenulate mesial carina restricted to its apical third; (4) cervicodorsal vertebra having three pneumatic foramina on its ventral surface*; (5) cervicodorsal vertebra having epipophyseal fossa*; and (6) phalanx 2-II showing reduced distal condyles and collateral pits located very close to the anterodorsal corner of the condyles (shared with troodontids).

Etymology—“Kank,” in reference to the “elder Rhea,” who created the constellation Choiols (Southern Cross constellation) in the Aonikenk mythology, and “australis,” which means “from south” in Latin, in reference to the southern latitude where this dinosaur was found.

 

Matías J. Motta, Alexis M. Aranciaga Rolando, Sebastián Rozadilla, Federico L. Agnolín, Federico Brissón Egli, Gerardo P. Álvarez Herrera, Nicolás R. Chimento, Gastón Lo Coco, Takanobu Tsuihiji, Makoto Manabe, Diego Pol and Fernando E. Novas. 2026. New unenlagiid from the Chorrillo Formation (Late Cretaceous, Maastrichtian), SW Patagonia, Argentina. Journal of Vertebrate Paleontology. e2656456. DOI: doi.org/10.1080/02724634.2026.2656456  [28 May 2026]

https://newsroom.taylorandfrancisgroup.com/heron-like-fish-eating-dinosaur-from-70-million-years-ago-discovered-in-argentina

https://www.macnconicet.gob.ar/kank-australis-el-nuevo-raptor-descubierto-en-la-patagonia-argentina

[Paleontology • 2026] Ptychotherates bucculentus • A New Taxon of saurischian Dinosaur (Saurischia: Morphoraptor) from the Coelophysis Quarry of New Mexico, USA (Triassic: latest Norian or Rhaetian) highlights herrerasaurian diversity in the latest Triassic

 

Ptychotherates bucculentus 

Srivastava & Nesbitt, 2026

DOI: doi.org/10.1002/spp2.70069 

Abstract

The most complete record of the earliest dinosaur lineages is from the Carnian from the higher latitudes of Pangea (e.g. present-day Brazil, Argentina), but dinosaurian assemblages from the upper stages of the Upper Triassic are better known from the low latitudes of Pangea (present day southwestern USA). How early carnivorous dinosaurian diversity matches or mismatches at various latitudes remains to be documented because of uncertainty around the spatio-temporal ranges and phylogenetic relationships of early dinosaur lineages. We examine low-latitude diversity patterns through the lens of the saurischian dinosaur Tawa hallae and close relatives, including a new species, Ptychotherates bucculentus gen. et sp. nov. The new taxon is known from an incomplete but well-preserved skull (CM 31368) from the uppermost Triassic Coelophysis Quarry in northern New Mexico. The new taxon clearly shares synapomorphies with Tawa hallae, such as distinctive fossae on the quadrate and otoccipital and a dorsoventrally tall and laterally flat jugal. However, the new taxon is distinguishable from all other coeval ornithodirans by a combination of many character states, including the proportionally dorsoventrally deepest jugal known for any Triassic-aged dinosaur. Higher-palaeolatitude ecosystems across Pangea show a complete turnover of carnivorous dinosaurs by neotheropods in the Norian and Rhaetian, but the ‘Chindesaurus–Tawa’ clade (Morphoraptora clade nov.) coexisted with neotheropods possibly until the End-Triassic Extinction Event. This suggests a low-latitude ‘museum’ where early-diverging lineages survived much longer than at higher latitudes, and that the End-Triassic Extinction Event affected dinosaur diversity more than previously hypothesized.

Keywords: biogeography, Saurischia, extinction, skull, phylogenetics, clade longevity

SYSTEMATIC PALAEONTOLOGY

DINOSAURIA Owen 1842 sensu Langer et al. 2020

SAURISCHIA Seeley 1888 sensu Gauthier et al. 2020

Clade MORPHORAPTORA nov.

Derivation of name: Morphe from the Greek for ‘form, shape’ and raptor from the Latin for ‘robber’, describing the morphological convergence between members of this clade and Theropoda, as if this clade is ‘stealing’ morphology. ‘Morphoraptor’ loosely translates to ‘bodysnatcher’, in honour of the 2007 song by Radiohead in the album In Rainbows, which author S. Srivastava listened to hundreds of times while preparing this manuscript.

The posterior portion of the skull Ptychotherates bucculentus (CM 31368) in posterior view.

Abbreviations: ar, articular bo, basioccipital; bt, basituber; f, frontal; fm, foramen magnum; fno, fenestra ovalis; pa, parietal; par, paroccipital process of the otoccipital; mf, metotic foramen; n, nasal; pbs, parabasisphenoid; pf, prefrontal; po, postorbital; ptf, posttemporal fenestra; qj, quadratojugal; qu, quadrate; rap, retroarticular process; so, supraoccipital; sq, squamosal; st, stapes. Crossed circle indicates posterior direction out of page. Scale bar represents 1 cm.

Digital reconstruction of the skull of Ptychotherates bucculentus (CM 31368) in left lateral view. Dashed lines indicate extrapolation and the coloured infill indicates known bone presence.

Abbreviations: eaf, external antorbital fenestra; en, external naris; emf, external mandibular fenestra; itf, infratemporal fenestra; orb, orbit. Arrow indicates anterior direction. Scale bar represents 2 cm.

 

Genus Ptychotherates nov.

 

Derivation of name: Ptycho from the Greek for ‘fold’ because of the numerous and challenging axes of reorientation on elements of the holotype. Therates from the Greek for ‘hunter’, for the carnivorous habits inferred from its teeth.

 Ptychotherates bucculentus sp. nov.  

Derivation of name: The species epithet is Latin for ‘with full cheeks’ in reference to the exceptionally tall jugal.

 

Diagnosis: Ptychotherates bucculentus bears the following combination of character states (local autapomorphies indicated with *): supratemporal fossa present on posterior portion of the frontal and dorsal surface of the parietal; tapering dorsal process of the maxilla; maxilla lacking antorbital fossa on its posterior portion ventral to the antorbital fenestra; prefrontal symmetrical in lateral view*; jugal body proportionally dorsoventrally deep* (i.e. more than three times as deep as the jugal posterior process, deeper than the length of postorbital ventral process, and more than half the height of the quadrate main body; Table 1); laterally extensive ventral process (= crista interfenestralis) of the otoccipital; ventral process of squamosal anteroposteriorly wide with a lateral fossa on the posterior part; retroarticular process upturned immediately posterior to glenoid; anterolateral portion of postorbital dorsally overhanging orbit; postorbital dorsolaterally overlapping the squamosal; posttemporal fenestra as wide as foramen magnum; nasal and frontals flat dorsally; serrated and recurved teeth with fine serrations (4–5 per 1 mm in the maxilla, 5–6 per 1 mm in the dentary) with pointed apices of the serrations.

Artistic rendition of Ptychotherates bucculentus.

Artwork by Megan Sodano 

 

Simba Srivastava and Sterling J. Nesbitt. 2026. A New Taxon of saurischian Dinosaur from the Coelophysis Quarry of New Mexico, USA (Triassic: latest Norian or Rhaetian) highlights herrerasaurian diversity in the latest Triassic. Papers in Palaeontology. 12(2); e70069. DOI: doi.org/10.1002/spp2.70069 [14 April 2026]

[Paleontology • 2026] Alnashetri cerropoliciensis • Argentine Fossil rewrites Evolutionary History of a baffling Dinosaur Clade

Alnashetri cerropoliciensis Makovicky, Apesteguía & Gianechini, 2012

in Makovicky, Mitchell, Meso, Gianechini, Cerda et Apesteguía, 2026.  

 DOI: doi.org/10.1038/s41586-026-10194-3

Abstract

Alvarezsauroids are an enigmatic clade of predominantly small-bodied theropod dinosaurs that are known mainly from the Jurassic to Cretaceous periods of Asia and South America. Late Cretaceous alvarezsauroids possess specialized forelimbs adapted for digging, minute supernumerary teeth and heightened sensory capacities, and are interpreted as myrmecophagous. They are hypothesized to exhibit evolutionary miniaturization coupled to their dietary specialization. Fragmentary South American taxa are traditionally arrayed as a paraphyletic grade with respect to the Late Cretaceous Asian subclade Parvicursorinae, invoking dispersal to explain their disjunct distributions. Here we describe a skeleton of the alvarezsauroid Alnashetri cerropoliciensis representing to our knowledge the most complete and smallest South American taxon to date. We also recognize two alvarezsauroids among historic taxa from the Northern Hemisphere. Phylogenetic analysis recovers Alnashetri among basal non-alvarezsaurids, rendering South American taxa polyphyletic. Combined with the new taxa recognized here, our biogeographical analyses infer a Pangaean ancestral distribution for Alvarezsauroidea, with vicariance dominating the early history of the clade. The early branching position of Alnashetri among larger-bodied relatives revises best-fit models of body size evolution in alvarezsauroids—we find no support for evolutionary miniaturization but, rather, find support for repeated evolution within a narrow body size range.

 

Peter J. Makovicky, Jonathan S. Mitchell, Jorge G. Meso, Federico A. Gianechini, Ignacio Cerda and Sebastian Apesteguía. 2026. Argentine Fossil rewrites Evolutionary History of a baffling Dinosaur Clade.  Nature. DOI: doi.org/10.1038/s41586-026-10194-3 [25 February 2026]

 x.com/NatureJapan/status/2031626177027387582

[Paleontology • 2026] Spinosaurus mirabilis • Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation

Spinosaurus mirabilis

Sereno, Vidal, Myhrvold, Johnson-Ransom, Ciudad Real, Baumgart, Sánchez Fontela, Green, Saitta, Adamou, Bop, Keillor, Fitzgerald, Dutheil,  Laroche, Demers-Potvin, Simarro, Gascó-Lluna,  Lázaro, Gamonal, Beightol, Reneleau, Vautrin, Bertozzo, FGranados, Kinney-Broderick, Mallon, Lindoso, Ramezani & Jahandar, 2026

 

DOI: doi.org/10.1126/science.adx5486

Artwork: Dani Navarro

 Abstract

INTRODUCTION: The fossils of Spinosaurus aegyptiacus, a giant sail-backed, fish-eating theropod dinosaur from northern Africa, have inspired competing lifestyle interpretations, either as a semiaquatic ambush predator stalking shorelines and shallows or a fully aquatic predator in pursuit of prey underwater. Its bones and teeth have been found only in coastal deposits near marine margins, a locale potentially consistent with either lifestyle interpretation.

RATIONALE: In the central Sahara, a new fossiliferous area (Jenguebi) was discovered in beds equivalent in age [Farak Formation; Cenomanian ~95 million years ago (Mya)] to those yielding fossil remains of S. aegyptiacus. We describe from this area a new species, Spinosaurus mirabilis sp. nov., which is very similar to S. aegyptiacus in skeletal form but with a much taller, scimitar-shaped cranial crest. Two new sauropods were found in close association with the new spinosaurid buried in fluvial sediments indicative of an inland riparian habitat.

RESULTS: Spinosaurus mirabilis sp. nov. is distinguished by the low profile of its snout, a hypertrophied nasal-prefrontal crest, greater spacing of posterior maxillary teeth, and other features. Its features highlight the extraordinary specializations of both species of the genus Spinosaurus, including interdigitating upper and lower teeth. Principal component analysis of body proportions places spinosaurids between semiaquatic waders (e.g., herons) and aquatic divers (e.g., darters) distant from all other predatory dinosaurs. A time-calibrated phylogenetic analysis resolves three evolutionary phases: an initial Jurassic radiation when their distinctive elongate fish-snaring skull evolved and split into two distinctive designs, baryonychine and spinosaurine; an Early Cretaceous circum-Tethyan diversification when both reigned as dominant predators; and a final early Late Cretaceous phase when spinosaurines attained maximum body size as shallow water ambush specialists limited geographically to northern Africa and South America.

CONCLUSION: The discovery of the tall-crested S. mirabilis sp. nov. in a riparian setting within an inland basin supports a lifestyle interpretation of a wading, shoreline predator with visual display an important aspect of its biology. At the end of the Cenomanian about 95 million years ago, an abrupt eustatic rise in sea level and the attendant climate change brought the spinosaurid radiation to an end.

Sheathed bony head crests in extinct and living dinosaurs. Spinosaurus mirabilis sp. nov., evolved the tallest head crest of any theropod dinosaur, drawing attention to the midline ornamentation that characterizes the cranium and axial skeleton of all spinosaurids. In life, the crest would have been extended to some degree by a keratinous sheath, as in the living helmeted guinea fowl (Numida meleagris). Visual signaling, as is the case in guinea fowl and other crested avians, was likely the function of spinosaurid cranial crests and trunk and tail sails. Scale bar, 20 cm for S. mirabilis and 3 cm for N. meleagris.

Spinosaurus mirabilis

A single Spinosaurus mirabilis rears over a carcass of the coelacanth Mawsonia on the forested bank of a river some 95 million years ago in what is now the Sahara Desert in Niger. A scimitar-shaped head crest and interdigitating teeth characterize this wading giant, one of the last-surviving species of a spinosaurid radiation some 50 million years in the making.

Artwork: Dani Navarro

Sereno, Paul C.; Vidal, Daniel; Myhrvold, Nathan P.; Johnson-Ransom, Evan; Ciudad Real, María; Baumgart, Stephanie L.; Sánchez Fontela, Noelia; Green, Todd L.; Saitta, Evan T.; Adamou, Boubé; Bop, Lauren L.; Keillor, Tyler M.; Fitzgerald, Erin C.; Dutheil, Didier B.; Laroche, Robert A. S.; Demers-Potvin, Alexandre V.; Simarro, Álvaro; Gascó-Lluna, Francesc; Lázaro, Ana; Gamonal, Arturo; Beightol, Charles V.; Reneleau, Vincent; Vautrin, Rachel; Bertozzo, Filippo; Granados, Alejandro; Kinney-Broderick, Grace; Mallon, Jordan C.; Lindoso, Rafael M.; Ramezani, Jahandar. 2026. Scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation. Science. 391 (6787) eadx5486. DOI: doi.org/10.1126/science.adx5486 [19 Feb 2026] 

 

Editor’s summary: Recent descriptions of and debates about the massive, fish-eating dinosaur Spinosaurus have brought this striking predator to the forefront of the dinosaur pantheon. Its huge size and distinctive morphology have stimulated much debate about the degree to which it lived an aquatic lifestyle. Sereno et al. describe a crested fossil Spinosaurus found in northern Africa as a new species. The researchers argue that this group of dinosaurs underwent three phases of evolution with increasing aquatic adaptations and existence in habitats around the Tethys Sea. —Sacha Vignieri

[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]

http://x.com/JGN_Paleo/status/1983926921898660347

[Paleontology • 2025] Huayracursor jaguensis • A long-necked early Dinosaur from a newly discovered Upper Triassic basin in the Andes

 

Huayracursor jaguensis

Hechenleitner, Martinelli, Rocher, Fiorelli, Juarez, Taborda & Desojo, 2025

DOI: doi.org/10.1038/s41586-025-09634-3 

Abstract

During the Late Triassic epoch (237–201 million years ago), the terrestrial ecosystems of Pangaea underwent drastic changes that led to the rise and diversification of mammaliaforms, crocodylomorphs and dinosaurs. Although the Carnian sedimentary rocks of South America provided much of the available evidence for understanding the early evolution of these clades, key discoveries have remained restricted to the Ischigualasto-Villa Unión and Paraná basins in Argentina and Brazil, respectively. Here we report a Carnian tetrapod assemblage from the previously unrecognized Northern Precordillera Basin in northwestern Argentina. Discoveries at this basin, in the Quebrada Santo Domingo site, include a nearly complete skeleton of the early sauropodomorph Huayracursor jaguensis gen. et sp. nov., and typical components of Late Carnian faunas, such as hyperodapedontine rhynchosaurs, gomphodontosuchine traversodontid cynodonts, and aetosaurs. Compared to its generally small and short-necked Carnian counterparts, Huayracursor is larger and exhibits an incipient elongation of its cervical vertebrae, representing an intermediate condition for size and cervical elongation between known Carnian and Norian sauropodomorphs. This discovery provides one of the oldest pieces of evidence of increased body mass and neck elongation in early Sauropodomorpha.

Huayracursor jaguensis gen. et sp. nov.

 

E. Martín Hechenleitner, Agustín G. Martinelli, Sebastián Rocher, Lucas E. Fiorelli, Malena Juarez, Jeremías R. A. Taborda and Julia B. Desojo. 2025. A long-necked early Dinosaur from a newly discovered Upper Triassic basin in the Andes. Nature. DOI: doi.org/10.1038/s41586-025-09634-3 [15 October 2025]