[Paleontology • 2026] Acutodon villeveyracensis • A New pan-shinisaur Lizard (Anguimorpha) from the lower Campanian of Villeveyrac (Hérault, France)

Acutodon villeveyracensis 

Jansen, Augé, Garcia, Otero & Valentin, 2026

DOI: doi.org/10.1080/02724634.2026.2636649 

Artwork by Olivier Jansen

ABSTRACT

The Chinese crocodile lizard (Anguimorpha, Pan-Shinisaurus Shinisaurus crocodilurus) is an endangered species inhabiting the lowland rainforests of southeastern China and northern Vietnam. The evolutionary history of this clade remains poorly understood, as only five fossil species and a few fossil specimens are described from the Lower Cretaceous of China and the Cenozoic of Europe and North America, revealing a considerable gap in the fossil record. A new anguimorph, Acutodon villeveyracensis gen. et sp. nov., is described from the lower Campanian (Upper Cretaceous) locality of Villeveyrac (Hérault, France), corresponding to a freshwater subtropical paleoenvironment. The species is attributed to a pan-shinisaur anguimorph based on a toothed maxilla sharing multiple characters with the extant Sh. crocodilurus and its fossil relatives, notably tall, tapered, and recurved teeth, with mesiodistally constricted tooth bases lacking basal infoldings but possessing medial resorption pits, and a posteromedially shifted anterior superior alveolar foramen. This Cretaceous record is the oldest in Europe for pan-shinisaur lizards. It pre-dates the occurrence of this clade in Europe by around 30 Myr, raising questions about the paleobiogeographic history of pan-shinisaur lizards.

Acutodon villeveyracensis holotype and unique material (UP.VIL.2010.55). Photographs, virtual reconstruction, and interpretative drawings of the maxilla in A, labial; B, lingual; C, occlusal; and D, dorsal views. Note that the posteriormost tooth was lost after CT scanning.

Abbreviations: asaf, anterior superior alveolar foramen; ce, cutting edge; cl, crista lateralis; ct, crista transversalis; fp, facial process; lf, labial foramina; lic, lamina intercristalis; lpp, lateral premaxillary process; lr, lacrimal recess; mpp, medial premaxillary process; ps, palatal shelf; rp, resorption pit; sds, supradental shelf. Scale bar equals 10 mm.

Details of the teeth of Acutodon villeveyracensis holotype and unique material (UP.VIL.2010.55) from the virtual reconstruction.
A, morphology in anterior view; B, section in median plane; C, section in horizontal plane.

Abbreviations: asaf, anterior superior alveolar foramen; c, cement; cl, crista lateralis; ct, crista transversalis; d, dentine; lf, labial foramen; lpp, lateral premaxillary process; m, maxilla; mpp, medial premaxillary process; ps, palatal shelf; t1–t4, teeth numbered from front to back. Scale bar equals 2 mm.

SQUAMATA Oppel, 1811

ANGUIMORPHA Fürbringer, 1900

PAN-SHINISAURUS sensu Smith and Gauthier, 2013

ACUTODON gen. nov.

ACUTODON VILLEVEYRACENSIS, gen. et sp. nov.

Diagnosis—Large anguimorph lizard characterized by the following combination of characters: the teeth are tall, thin, and possess a tapered apex; anterior teeth are strongly posteriorly recurved, but the most posterior teeth are straight; the teeth lack striations and basal infoldings; the base of the teeth expands lingually but is strongly anteroposteriorly compressed, and is covered in a thin layer of cementum; the crowns have a faint cutting edge, restricted to the most apical portion; medial resorption pits are ...

Etymology—‘acutus’ (Latin), sharp, pointed, piercing, and thin; ‘ὀδόντος’ (Greek), teeth; the genus name refers to the tapered, sharp, and thin teeth of this new genus; ‘villeveyracensis’ (Latin) from the locality of Villeveyrac, department of Hérault, France, where this new lizard taxon has been found.

Acutodon villeveyracensis
Paleoartistic reconstruction of the new genus and species of pan-shinisaur lizard from the lower Campanian of Villeveyrac (Hérault, France). Original artwork by Olivier Jansen.

Olivier Jansen, Marc Augé, Geraldine Garcia, Olga Otero and Xavier Valentin. 2026. A New pan-shinisaur Lizard (Anguimorpha) from the lower Campanian of Villeveyrac (Hérault, France). Journal of Vertebrate Paleontology. DOI: doi.org/10.1080/02724634.2026.2636649  [20 May 2026]

[PaleoMammalogy • 2026] Cimolodon desosai • Cranial and Postcranial Remains of A New Species of Cimolodon (Multituberculata: Cimolodontidae) from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, México

Cimolodon desosai

Mantilla, Newbins, Fastovsky, Zhang, Montellano-Ballesteros, Alcántara & Chen, 2026

DOI: doi.org/10.1080/02724634.2026.2641109

Illustration by Andrey Atuchin

ABSTRACT

Late Cretaceous mammals from North America are predominantly known from isolated teeth and fragmentary jaws and from localities representing coastal lowlands along the Western Interior Seaway. Here, we report craniodental and associated postcranial remains of a new species of the cimolodontid multituberculate genus Cimolodon from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, México. The specimen was deposited along the Pacific Coast between 75.17 ± 0.30 Ma and 74.55 ± 0.18 Ma. It represents the most complete mammal known from the Mesozoic of México and one of the best known cimolodontan multituberculates from North America. Morphologically, the new species, Cimolodon desosai, is most like C. nitidus, but differences include upper anterior premolar shape, molar cusp formulae, and relative length proportions of the cheek teeth. Phylogenetic analysis supports placement of the new species within Cimolodon and Ptilodontoidea, but uncertainties remain regarding relationships among cimolodontan families. Using the craniodental and postcranial data, we quantitatively reconstruct C. desosai as a small-bodied (∼100 g), animal-dominated omnivore with a scansorial locomotor mode. With the new taxonomic occurrence, the El Gallo mammalian local fauna is now known from 16 specimens referred to three multituberculate species (Mesodma cf. M. formosa, ?Stygimys sp., and Cimolodon desosai), one metatherian (Pediomys sp.), and one eutherian (Gallolestes pachymandibularis). Although further sampling is needed, the mammalian local fauna presently shows greatest biogeographic affinities with the Terlingua local fauna of western Texas.

SYSTEMATIC PALEONTOLOGY

MAMMALIA Linnaeus, 1758

MULTITUBERCULATA Cope, 1884

CIMOLODONTA McKenna, 1975

PTILODONTOIDEA Sloan and Van Valen, 1965

CIMOLODONTIDAE McKenna, 1975

CIMOLODON Marsh, 1889

CIMOLODON DESOSAI, sp. nov.

Partial cranium of the holotype of Cimolodon desosai (IGM 14691).
Images are three-dimensional surface renderings from μCT scans in: A, anterior; B, stereo dorsal; C, stereo ventral; D, left lateral; and E, right lateral views of the partial cranium; and F, occlusal view of the right upper cheek tooth row in high magnification. Dashed white lines represent interpreted position of cranial bone sutures.

Abbreviations: al, anterior lamina; fr, frontal; iof, intraorbital foramen; mx, maxilla; na, nasal; naf, nasal foramen; otc, orbitotemporal canal; pa, parietal; pav, palatal vacuity; pmx, premaxilla; pop, postorbital process; sq, squamosal; zpm, zygomatic process of the maxilla. Scale bar equals 10 mm for A–E and 2 mm for F.

Cimolodon desosai on the tree with a fruit in its mouth. It was about the size of a golden hamster. It likely scampered on the ground and in the trees and ate fruits and insects.

Illustration by Andrey Atuchin

 

 

Gregory P. Wilson Mantilla, Isiah R. Newbins, David E. Fastovsky, Yue Zhang, Marisol Montellano-Ballesteros, Dalia García Alcántara and Meng Chen. 2026. Cranial and Postcranial Remains of A New Species of Cimolodon (Mammalia, Multituberculata, Cimolodontidae) from the Upper Cretaceous (Campanian) El Gallo Formation of Baja California, México. Journal of Vertebrate Paleontology. e2641109. DOI: doi.org/10.1080/02724634.2026.2641109  [22 Apr 2026]

[Paleontology • 2025] Wadisuchus kassabi • An early dyrosaurid (Pseudosuchia: Crocodyliformes) from the Campanian of Egypt sheds light on the Origin and Biogeography of Dyrosauridae

 

Wadisuchus kassabi

Saber, Salem, Ouda, Gohar, El-Sayed, O’Connor & Sallam, 2025 

DOI: doi.org/10.1093/zoolinnean/zlaf134

Paleoart by Nathan Dehaut. 

Abstract

Dyrosauridae are a clade of crocodyliforms characterized by diverse cranial morphologies and a broad palaeogeographic distribution from the Late Cretaceous to the Palaeogene. However, their early evolutionary history remains poorly understood due to a significant fossil gap during the Campanian. Here, we describe Wadisuchus kassabi gen. et sp. nov., an early-diverging dyrosaurid from the middle Campanian Quseir Formation of Egypt, based on two partial skulls and three partial mandibles. This new taxon displays transitional cranial features—including reduced premaxillary alveoli, modified occlusion patterns, and dorsally positioned external nares—that clarify aspects of cranial evolution related to longirostry in early dyrosaurids. Phylogenetic analyses consistently recover Wadisuchus as the earliest-diverging dyrosaurid, closely related to Chenanisuchus and distinct from Elosuchus, supporting a transition from dyrosauroids to dyrosaurids. Its Campanian age extends the temporal range of the clade and suggests that transatlantic dispersal from Africa to South America occurred earlier than previously recognized. Alongside Brachiosuchus kababishensis from Sudan, the new Egyptian taxon also implies that reverse dispersal into Africa preceded the Maastrichtian. Wadisuchus provides critical insights into the early diversification, palaeobiogeography, and cranial evolution of Dyrosauridae, confirming longirostry as an early-acquired trait and highlighting North Africa as a key region in their origin.

Campanian, Quseir Formation, Egypt, North Africa, Dyrosauridae, phylogeny

Life reconstruction of Wadisuchus kassabi from the Late Cretaceous of Egypt, showing an adult capturing a lungfish in a wetland, with a juvenile nearby. The scene highlights the ancient ecosystem, including turtles and lush vegetation, based on fossil evidence from the Quseir Formation.

Paleoart by Nathan Dehaut. / MUVP—Scientific supervision

Wadisuchus kassabi gen. et sp. nov.

Sara Saber, Belal S Salem, Khaled Ouda, Abdullah S Gohar, Sanaa El-Sayed, Patrick M O’Connor and Hesham M Sallam. 2025. An early dyrosaurid (Wadisuchus kassabi gen. et sp. nov.) from the Campanian of Egypt sheds light on the Origin and Biogeography of Dyrosauridae. Zoological Journal of the Linnean Society. 205(2) zlaf134. DOI: doi.org/10.1093/zoolinnean/zlaf134 [27 October 2025]

[Paleontology • 2025] Ahshislesaurus wimani • A New saurolophine hadrosaurid (Ornithischia: Hadrosauridae) from the Upper Cretaceous (Campanian) Hunter Wash Member, Kirtland Formation, San Juan Basin, New Mexico

Ahshislesaurus wimani 

Dalman, Jasinski, Malinzak, Malinzak, Lucas, Kundrát, Fiorillo, 2025

 

 Researchgate.net/publication/396005330

Artwork by Sergey Krasovskiy

A new saurolophine hadrosaurid dinosaur, Ahshislesaurus wimani gen et sp. nov., from the lower Hunter Wash Member of the lower Kirtland Formation (~75.02 Ma) of New Mexico is described. The specimen was briefly described before and referred to the stratigraphically younger Kritosaurus navajovius, which is known from the De-na-zin Member (~73.83–73.49 Ma) of the uppermost Kirtland Formation. The holotype of A. wimani consists of an incomplete diagnostic skull, several isolated cranial elements including the right jugal, quadrate, dentary, and surangular, and a series of articulated cervical vertebrae. In addition to the holotype of A. wimani, several specimens from the same strata may also belong to this newly identified species, including a well-preserved left dentary and a partial skeleton, as well as two humeri, one belonging to a large adult and the other to a juvenile. The skull of A. wimani preserves several taxonomically informative characters that show close affinities with the stratigraphically younger Naashoibitosaurus ostromi from the De-na-zin Member. Together with Naashoibitosaurus, Ahshislesaurus forms a potentially novel clade of flat-headed saurolophine hadrosaurids. This clade suggests the saurolophines were a taxonomically diverse group, which, during the last 20 million years of the Cretaceous, were among the dominant herbivorous dinosaurs in southern Laramidia. Recognition of a new hadrosaurid species from New Mexico also provides further evidence for latitudinal variation in the hadrosaurid fauna during the Late Cretaceous in Laramidia.

Skeleton reconstruction of Ahshislesaurus wimani gen. et sp. nov., (USNM VP-8629), holotype skull.
This includessome of the postcranial specimens from the lower Hunter Wash Member (Kirtland Formation) that may not represent this newspecies, including a postcranial skeleton (NMMNH P-25057); left scapula (NMMNH P-RMS 2013-7); left humerus (NMMNHP-31928); and right isolated ulna (NMMNH P-32885).

SYSTEMATIC PALEONTOLOGY

DINOSAURIA Owen, 1842

ORNITHISCHIA Seeley, 1887

ORNITHOPODA Marsh, 1881

IGUANODONTIA Dollo, 1888

HADROSAURIA von Huene, 1956

HADROSAURIDAE Cope, 1870

SAUROLOPHINAE Brown, 1914

Ahshislesaurus, new genus

Etymology: The genus name Ahshislesaurus is from the Ah-shi-sle-pah Wash Wilderness in the lower Hunter Wash Member of the Kirtland Formation in northwestern New Mexic where the new species was found. Ah-shi-sle-pah Wildernessis located in San Juan County, New Mexico, between Chaco Canyon and the De-na-zin Wilderness. Its name is a phonetic transliteration of Navajo “áshįįh łibá” meaning “salt, it is gray.”.

Ahshislesaurus wimani, new species 

Etymology: The specific epithet, wimani, honors the first Swedish professor of paleontology, Carl Wiman (1867–1944),from Uppsala University, who worked on fossil vertebrates from the San Juan Basin. 

Life reconstruction of Ahshislesaurus wimani gen. et sp. nov. based on the holotype (USNM VP-8629) and closely related taxa.

Artwork by Sergey Krasovskiy

Sebastian G Dalman, Steven E. Jasinski, D Edward Malinzak, ... et Anthony R. Fiorillo. 2025. A New saurolophine hadrosaurid (Ornithischia: Hadrosauridae) from the Upper Cretaceous (Campanian) Hunter Wash Member, Kirtland Formation, San Juan Basin, New Mexico. New Mexico Museum of Natural History and Science Bulletin. Fossil Record. 11: 73–114. (September 2025)  

 Researchgate.net/publication/396005330_A_new_saurolophine_hadrosaurid_from_the_Upper_Cretaceous_Hunter_Wash_Member_Kirtland_Formation_San_Juan_Basin_New_Mexico

[PaleoEntomology • 2025] Cordualadensa acorni • New Family of Fossil Dragonfly (Odonata: Cavilabiata) from the late Cretaceous (Campanian) Dinosaur Park Formation, Alberta, Canada

Cordualadensa acorni

Mueller, Demers-Potvin & Larsson, 2025 

  

DOI: doi.org/10.1139/cjes-2024-0162  

Abstract

A new dragonfly species, Cordualadensa acorni gen. et sp. nov., assigned to Cordualadensidae fam. nov. (Odonata, Cavilabiata), is described from Dinosaur Provincial Park (DPP). The taxon represents the oldest known North American fossil taxon within Cavilabiata and the only Mesozoic dragonfly for Canada. This discovery provides a missing link in the evolutionary transition from the early Cretaceous Cavilabiata to extant families and introduces one of the few dragonflies known from the late Cretaceous fossil record. The specimen described herein also confirms that insect impression fossils can be preserved in the Dinosaur Park Formation (DPF) and suggests that the diversity of the entomofauna preserved in DPP's fossil assemblage is only beginning to be fully appreciated. The presence of dragonflies in the DPF also supports the hypothesis that Campanian Alberta had a sufficiently high insect biomass to support insect predators at higher trophic levels.

Cordualadensa acorni gen. et sp. nov.

 

 André S. Mueller, Alexandre V. Demers-Potvin and Hans C.E. Larsson. 2025. New Family of Fossil Dragonfly (Odonata, Cavilabiata) from the late Cretaceous (Campanian) Dinosaur Park Formation, Alberta, Canada. Canadian Journal of Earth Sciences. 62(8): 1373-1381. DOI: doi.org/10.1139/cjes-2024-0162  [1 August 2025]

https://www.mcgill.ca/newsroom/channels/news/mcgill-team-discovers-canadas-first-dinosaur-era-dragonfly-fossil-366386

[Paleontology • 2024] Labocania aguillonae • A New Tyrant Dinosaur (Theropoda: Tyrannosauridae) from the Late Campanian of Mexico Reveals a Tribe of Southern Tyrannosaurs

  

 Labocania aguillonae

    Rivera-Sylva & Longrich, 2024

 www.mdpi.com/2813-6284/2/4/12  

facebook.com/NickLongrich

Artwork by Andrey Atuchin.

Abstract

The end of the Cretaceous saw the Western Interior Seaway divide North America into two land masses, Laramidia in the west and Appalachia in the east. Laramidian dinosaurs inhabited a narrow strip of land extending from Mexico to Alaska. Within this geographically restricted area, dinosaurs evolved high diversity and endemism, with distinct species in the north and south. Here, we report a new tyrannosaurid from the Late Campanian-aged Cerro del Pueblo Formation of Coahuila, Mexico, which is part of a tribe of tyrannosaurs originating in southern Laramidia. Phylogenetic analysis recovers the new tyrannosaur as part of a clade including Labocania anomala from the La Bocana Roja Formation of Baja California Norte, Bistahieversor sealeyi from the Kirtland Formation of New Mexico, Teratophoneus curriei from the Kaiparowits Formation in Utah, and Dynamoterror dynastes from the Menefee Formation of New Mexico. Distinct frontal morphology and the younger age (~72.5–73 Ma versus >75.8 Ma for L. anomala) support recognition of the new tyrannosaur as a distinct species of Labocania, Labocania aguillonae. The Labocania clade dominated southern Laramidia at a time when the north was dominated by daspletosaurins and albertosaurines. The high endemism seen in tyrannosaurids is remarkable, given that modern apex predators have large geographic ranges and hints that the diversity of carnivorous dinosaurs has been underestimated.

Keywords: Tyrannosauridae; dinosauria; Campanian; Cretaceous; Laramidia

Skeletal reconstruction of Labocania aguillonae (CPC 2974) showing preserved material. Scale = 1 m.

Systematic paleontology

Dinosauria—Owen 1842  

Theropoda—Marsh, 1881  

Coelurosauria—von Huene 1914  

Tyrannosauridae—Osborn, 1906 

Tyrannosaurinae—Osborn, 1906  

Teratophoneini—Scherer & Voiculescu-Holvad, 2024  

Labocania—Molnar 1974  

Labocania aguillonae sp. nov.

Diagnosis: Tyrannosaurine diagnosed by the following character combination (*—autapomorphies): orbit large and circular, with a very strongly convex anteroventral margin of the lacrimal* with a prominent, strongly dorsally extended* subocular process on the lacrimal along the anteroventral margin of the orbit; strong posteroventral extension of the antorbital fossa onto the lacrimal to end below the anterior margin of the orbit; lateral ends of frontals with a very prominent, acutely triangular shape, with strong transversely expanded overlap of frontal onto lacrimal; broad anteromedial extension of supratemporal fossa extending far forward onto frontal*; strong medial projection of postorbitals behind frontals onto dorsolateral surface of postorbital process, such that frontal underlaps the postorbital anteriorly*, lateral teeth with a figure-eight basal cross-section, and deep, prominent grooves or fullers extending from the root up the labial and lingual surfaces of the crown.

 Etymology: The species name honors Martha C. Aguillón, discoverer of the specimen and a long-time career paleontologist of Coahuila.

Conclusions: 

CPC 2974 represents a new species of tyrannosaurid, Labocania aguillonae, closely related to Labocania anomala, Bistahieversor sealeyi, and Teratophoneus curriei. It adds to the diversity of the Cerro del Pueblo Formation and shows that endemicity existed within tyrannosaurs in the Late Campanian, with distinct species and clades inhabiting the northern Great Plains in the north and the American Southwest and Mexico in the south. Given the limited geographic sampling, many tyrannosaur species likely remain undiscovered. Competition between species likely helped to enforce endemism among dinosaurs. Why large dinosaurs seem to have such unusually high levels of endemism compared to modern mammals remains unclear.

 Héctor E. Rivera-Sylva and Nicholas R. Longrich. 2024. A New Tyrant Dinosaur from the Late Campanian of Mexico Reveals a Tribe of Southern Tyrannosaurs. Foss. Stud. 2024, 2(4), 245-272. DOI: doi.org/10.3390/fossils2040012  www.mdpi.com/2813-6284/2/4/12

  facebook.com/NickLongrich/posts/10160809409234125

[Paleontology • 2024] Coahuilasaurus lipani • a New Kritosaurin Hadrosaurid (Hadrosauridae: Saurolophinae) from the Upper Campanian Cerro Del Pueblo Formation, Northern Mexico

Coahuilasaurus lipani

Longrich, Velasco, Kirkland, Torres & Serrano-Brañas, 2024

 

DOI: 10.3390/d16090531  

Life reconstruction by C. Díaz Frías

Abstract

The Late Cretaceous of Western North America (Laramidia) supported a diverse dinosaur fauna, with duckbilled dinosaurs (Hadrosauridae) being among the most speciose and abundant members of this assemblage. Historically, collecting and preservational biases have meant that dinosaurs from Mexico and the American Southwest are poorly known compared to those of the northern Great Plains. However, evidence increasingly suggests that distinct species and clades inhabited southern Laramidia. Here, a new kritosaurin hadrosaurid, represented by the anterior part of a skull, is reported from the late Campanian of the Cerro del Pueblo Formation, ~72.5 Ma, in Coahuila, Mexico. The Cerro del Pueblo Formation kritosaur was originally considered to represent the same species as a saurolophine from the Olmos Formation of Sabinas, but the Sabinas hadrosaur is now considered a distinct taxon. More recently, the Cerro del Pueblo Formation kritosaur has been referred to Kritosaurus navajovius. We show it represents a new species related to Gryposaurus. The new species is distinguished by its large size, the shape of the premaxillary nasal process, the strongly downturned dentary, and massive denticles on the premaxilla’s palatal surface, supporting recognition of a new taxon, Coahuilasaurus lipani. The dinosaur assemblage of the Cerro del Pueblo Formation shows higher diversity than the contemporaneous fauna of the Horseshoe Canyon Formation in Alberta. Furthermore, Kritosaurini, Lambeosaurini, and Parasaurolophini all persist into the latest Campanian in southern Laramidia after disappearing from northern Laramidia. These patterns suggest declining herbivore diversity seen at high latitudes may be a local, rather than global phenomenon, perhaps driven by cooling at high latitudes in the Late Campanian and Maastrichtian.

Keywords: Dinosauria; Hadrosauridae; Saurolophinae; Kritosaurini; Cretaceous; Campanian; Laramidia; biogeography

 IGM 6685, holotype Coahuilasaurus lipani. (A), rostrum with posterior skull reconstructed in left lateral view; (B), scaled silhouette. The animal is estimated to have been around 8 m in length.

Dinosauria Owen 1842

Ornithopoda Marsh 1881 

Hadrosauridae Cope 1869 

Saurolophinae Brown 1914 (sensu Prieto-Márquez, 2010)

Kritosaurini Brett-Surman 1989 (sensu Prieto-Márquez, 2014)

Coahuilasaurus lipani gen. et sp. nov.

Etymology. Coahuila in reference to Coahuila State + Greek sauros, ‘lizard’; lipani references the Lipani Apache tribe of Coahuila.

Diagnosis. Large kritosaurin with an estimated length of ~8 m (Figure 5). Distinguished by the following unique character combination (* = autapomorphies). The anterior margin of premaxillae is strongly convex in lateral view; the anterodorsal margin of the narial process is subtly sinusoidal in lateral view, being concave anteriorly then weakly convex posteriorly *. The narial aperture is narrow and slot-like and strongly extended anteroventrally *. The premaxillary labrum is deep anteriorly, becoming shallower posteriorly. The posteroventral corner of the premaxillary beak is strongly angular, with the anteroventral margin and posteroventral margin forming approximately a right angle in lateral view *; the posteroventral margin of the premaxilla is strongly concave in lateral view. The premaxilla is short and broad in dorsal view. The oral margin of the beak bears a series of 5–6 small denticles. The palatal surface of the premaxilla forms a horseshoe-shaped ridge projecting far below the oral margin *; the ridge bears three pairs of massive, diamond-shaped denticles*. The nasal–premaxillary contact is posteriorly positioned, probably near the end of the nasal aperture. Very large narial flange of premaxilla *. The predentary oral margin is strongly concave in the lateral view and has a steeply inclined rostroventral margin, and the tip is hooked up strongly in lateral view (approached in Gryposaurus monumentensis). There is a narrow U-shaped notch between predentary lateral processes and ventral processes (shared with Gryposaurus monumentensis); the ventral processes are long and slender. The edentulous end of the dentary is strongly downturned, with a strongly convex anterodorsal margin, and a long ventral contact between the dentaries.

 

 Map showing localities of kritosaurins from the Late Cretaceous of western North America (Laramidia).
1,2, Gryposaurus notabilis (incl. G. incurvimanus) Dinosaur Park Formation, Alberta; 3, Gryposaurus latidens, Two Medicine Formation, Montana; 4, Gryposaurus sp., Bearpaw Shale, Montana; 5, Kritosaurini indet., North Horn Formation, Utah;
6, Rhinorex condrupus, Neslen Formation, Utah; 7, Gryposaurus monumentensis, Kaiparowits Formation, Utah; 8, Anazisaurus horneri, Farmington Formation of the Kirtland Formation of New Mexico; 9, Naashoibitosaurus ostromi, De-Na-Zin Member of the Kirtland Formation of New Mexico; 10, Kritosaurus navajovius, De-Na-Zin Member of the Kirtland Formation of New Mexico;
11, Naashoibito kritosaurin, Naashobito Member of the Kirtland Formation of New Mexico; 12, Gryposaurus (?) alsatei, upper Javelina Formation, Texas; 13, cf. Kritosaurus, UTEP P.37.7, basal Javelina Formation of Texas; Aguja Formation, Texas; 14, Aguja Fm. Kritosaur, AMNH 3079; 15, Coahuilasaurus lipani, Cerro del Pueblo Formation, Coahuila. Map by Ron Blakey.

Conclusions: 

A partial skull from the latest Campanian of the Cerro del Pueblo Formation of Coahuila, Mexico, represents a new species of kritosaurin, Coahuilasaurus lipani (Figure 20). Along with specimens from the Naashoibito Member of the Kirtland Formation in New Mexico, C. lipani documents the persistence of kritosaurins in the south after local extinction in northern Laramidia, a pattern also seen in Parasaurolophini and Lambeosaurini.

Southern faunas not only have distinct species, but different patterns of diversity change, compared to northern Laramidian faunas. Differences in species composition and community structure in different parts of Laramidia mean that further work on the dinosaurs of Mexico and the American Southwest is needed to understand the evolution of dinosaur diversity in western North America. Southern dinosaur faunas may have been characterized by both higher origination rates and lower extinction rates than northern faunas.

 Nicholas R. Longrich, Angel Alejandro Ramirez Velasco, Jim Kirkland, Andrés Eduardo Bermúdez Torres and Claudia Inés Serrano-Brañas. 2024. Coahuilasaurus lipani, a New Kritosaurin Hadrosaurid from the Upper Campanian Cerro Del Pueblo Formation, Northern Mexico. Diversity. 16(9), 531. DOI: doi.org/10.3390/d16090531  

[Paleontology • 2024] Lokiceratops rangiformis gen. et sp. nov. (Ceratopsia: Ceratopsidae: Centrosaurinae) from the Campanian Judith River Formation of Montana reveals Rapid Regional Radiations and Extreme Endemism within centrosaurine dinosaurs

Lokiceratops rangiformis

 Loewen​​, Sertich​, Sampson, O’Connor, Carpenter, Sisson, Øhlenschlæger, Farke, Makovicky, Longrich & Evans, 2024

DOI: 10.7717/peerj.17224

Abstract
 The Late Cretaceous of western North America supported diverse dinosaur assemblages, though understanding patterns of dinosaur diversity, evolution, and extinction has been historically limited by unequal geographic and temporal sampling. In particular, the existence and extent of faunal endemism along the eastern coastal plain of Laramidia continues to generate debate, and finer scale regional patterns remain elusive. Here, we report a new centrosaurine ceratopsid, Lokiceratops rangiformis, from the lower portion of the McClelland Ferry Member of the Judith River Formation in the Kennedy Coulee region along the Canada-USA border. Dinosaurs from the same small geographic region, and from nearby, stratigraphically equivalent horizons of the lower Oldman Formation in Canada, reveal unprecedented ceratopsid richness, with four sympatric centrosaurine taxa and one chasmosaurine taxon. Phylogenetic results show that Lokiceratops, together with Albertaceratops and Medusaceratops, was part of a clade restricted to a small portion of northern Laramidia approximately 78 million years ago. This group, Albertaceratopsini, was one of multiple centrosaurine clades to undergo geographically restricted radiations, with Nasutuceratopsini restricted to the south and Centrosaurini and Pachyrostra restricted to the north. High regional endemism in centrosaurs is associated with, and may have been driven by, high speciation rates and diversity, with competition between dinosaurs limiting their geographic range. High speciation rates may in turn have been driven in part by sexual selection or latitudinally uneven climatic and floral gradients. The high endemism seen in centrosaurines and other dinosaurs implies that dinosaur diversity is underestimated and contrasts with the large geographic ranges seen in most extant mammalian megafauna.

Skull of Lokiceratops rangiformis n. gen et n. sp. (EMK 0012).
(A) Skull of Lokiceratops rangiformis in dorsal view. (B) Skull reconstruction in anterior view. (C) Skull reconstruction in lateral view interpreted from both sides. Reconstructions are based on 3D surface scans with deformation and parallax removed. The mandible was not found with EMK 0012.

Stippled artwork by Sergey Krasovskiy. Scale bar equals 1 m.

Systematic Paleontology

Dinosauria Owen, 1842; sensu Padian & May, 1993

Ornithischia Seeley, 1887; sensu Sereno, 1998

Ceratopsia Marsh, 1890; sensu Dodson, 1997

Ceratopsidae Marsh, 1888; sensu Sereno, 1998

Centrosaurinae Lambe, 1915; sensu Dodson, Forster & Sampson, 2004

Albertaceratopsini clade nov.

 

Diagnosis—Albertaceratopsini is defined as a stem-based clade that consists of all taxa more closely related to Albertaceratops nesmoi than to Centrosaurus apertus.

Lokiceratops gen. nov.

Lokiceratops rangiformis gen. et sp. nov.

Diagnosis—Lokiceratops rangiformis is an albertaceratopsin centrosaurine ceratopsid distinguished from other centrosaurines by the following autapomorphies: presence of unadorned nasal; elongate, uncurved ep1 epiossification directed in plane of frill along posterior margin of parietosquamosal frill; hypertrophied, lateral curving epiparietal ep2 directed in plane of frill. The hypertrophied ep2 is relatively larger than any other parietal epiossification within Centrosaurinae. Both ischia are distinctly kinked distally at about two-thirds of the length of the shaft, at the point where the two ischia contact medially. Postorbital horncore bases are deeply excavated by sinuses penetrating a distance equivalent to the orbital diameter of each horncore, to an extent unobserved in other long horned centrosaurs.

 

Etymology— The generic name refers to the god Loki from Norse mythology, and ceratops, (Greek) meaning “horned face.” The species name refers to the bilateral asymmetry of frill ornamentations, similar to the asymmetry in antlers of the reindeer/caribou genus Rangifer.

 

Holotype Locality—EMK 0012 was recovered from the Loki Quarry in Kennedy Coulee, south of the Milk River in Hill County, northern Montana (Fig. 1). The quarry is 3.6 km from the Montana-Alberta border and 922 m above sea level. Exact coordinates are available at the Evolutionsmuseet, Knuthenborg, Maribo, Denmark, and the Natural History Museum of Utah, United States of America.

Holotype Horizon—EMK 0012 was recovered from lower Judith River Formation horizons that correlate to the McClelland Ferry Member to the south, and to the lower part of the Oldman Formation of southern Alberta, 3.6 km to the north. EMK 0012 was located 11.4 m above the Marker A Coal equivalent to the Taber Coal Zone (at the top of the Foremost Formation) and laterally equivalent to the Herronton Sandstone Zone near the base of the Oldman Formation 3.6 km to the north in Alberta.

Age—High-precision U–Pb analyses of zircons by the CA-ID-TIMS method in a bentonite within the Marker A Coal (KC061517-1; 11.4 m below the Loki Quarry) date to 78.549 ± 0.024 Ma (Ramezani et al., 2022). Using the median Bayesian age model developed by Ramezani et al. (2022) for the stratigraphic position of the Loki Quarry recovers a date of roughly 78.1 Ma, with a lower modeled bound of 78.38 Ma and an upper modeled bound of 77.18 Ma.

  

Mark A. Loewen​​, Joseph J. W. Sertich​, Scott Sampson, Jingmai K. O’Connor, Savhannah Carpenter, Brock Sisson, Anna Øhlenschlæger, Andrew A. Farke, Peter J. Makovicky, Nick Longrich and David C. Evans. 2024. Lokiceratops rangiformis gen. et sp. nov. (Ceratopsidae: Centrosaurinae) from the Campanian Judith River Formation of Montana reveals Rapid Regional Radiations and Extreme Endemism within centrosaurine dinosaurs. PeerJ. 12:e17224. DOI: 10.7717/peerj.17224

[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