The fossil record of Cretaceous avian dinosaurs in Mexico remains limited compared with that of other vertebrate groups, but provides important evidence on the distribution, taxonomy, and paleoecology of birds in southern North America during the Late Cretaceous. Here, we critically review the currently known Mexican record, integrating osteological remains from Baja California and Coahuila with avian and avian-like ichnofossils from northeastern Mexico. Confirmed skeletal records include the enantiornithine Alexornis antecedens from the Campanian La Bocana Roja Formation and Ichthyornis sp. from the Coniacian–Campanian Austin Group. The ichnological record comprises several Campanian and Maastrichtian occurrences from the Cerro del Pueblo and Las Encinas formations, including the formally recognized ichnotaxon Leptoptilostipus isp. and additional footprint morphotypes. Critical reassessment indicates that footprint morphotypes cannot be equated directly with biological taxa because substrate properties, preservation, locomotor behavior, and other extramorphological factors may influence track morphology. Nevertheless, the combined osteological and ichnological evidence documents the recurrent presence of avian trackmakers across non-marine, marine, deltaic, wetland, and marginal environments in Mexico. The Mexican record therefore provides an important southern North American perspective on Cretaceous avian distribution while also highlighting substantial preservational and sampling biases. Future progress will depend on the renewed study of existing collections, targeted recovery of small vertebrate remains, and systematic reassessment of historically important tracksites.

Mosasaurs staged a major radiation at the end of the Cretaceous period before perishing at the Cretaceous-Paleogene boundary. Although mosasaurs are well-known from the Late Cretaceous of North America, relatively little is known about the mosasaurids of Mexico. In 2001 the largely complete skull of a mosasaurid was collected from outcrops of the Early Maastrichtian the skeleton was reported to have been present, only the skull was collected and the quarry has not been relocated. The specimen was described and figured in 2007 by Buchy et al. (2007) and reported as an indeterminate mosasaurid. Although the specimen has suffered some erosion after exposure in the desert, it includes most of the skull. We redescribe this specimen and show that it represents a derived species of Prognathodon, P. cipactli sp. nov. The specimen shows specializations for an apex predator niche, including a short rostrum with robust jaws and teeth, suggesting that specialization for taking large prey preceded the evolution of large size in prognathodontins. The specimen enhances our understanding of the fossil record and paleoecology of the Western Interior Seaway during the Late Cretaceous, showing how prognathodontins successfully exploited the top predator niche globally in the Maastrichtian.

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.

The fossil record of Ankylosauria is well-documented in several regions of the world yet remains relatively scarce in Mexico. Here we report new thyreophoran material from the Late Cretaceous in Coahuila, northeastern Mexico. The specimens, which include isolated osteoderms and partial skeletal elements, contribute to our understanding of the diversity, paleobiogeography, and paleoecology of this dinosaur clade in North America. Morphological comparisons suggest affinities with nodosaurid ankylosaurs, expanding their known range and ecological roles in the region. This discovery highlights the importance of Coahuila as a key locality for studying dinosaur faunas at the southern margin of the Western Interior Seaway.

The Mosasauridae underwent a major radiation early in the Late Cretaceous, with the subfamilies Plioplatecarpini and Tylosaurini appearing in the Turonian. Here we report an almost complete mosasaur skull assigned to the plioplatecarpine genus Yaguarasaurus. The specimen was discovered southwest of Vallecillo in the northeastern Mexico state of Nuevo Leon, about 80 km north of Monterrey, in a laminated limestone layer of the upper member of the Agua Nueva Formation (Upper Turonian - ?Lower Coniacian). The specimen is referred to as a new species, Y. regiomontanus. This is the first report of Yaguarasaurus from Mexico and the most complete of the Americas. At roughly 5 m in length, it is one of the earliest large mosasaurids. Along with Yaguarasaurus columbianus, Russellosaurus coheni, and an unnamed plioplatecarpine from Texas, it documents the rapid diversification and expansion of plioplatecarpines in the marine realm in the Turonian.

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.

A new long-legged, spatula-beaked, filter-feeding pterodactyloid pterosaur from Upper Jurassic plattenkalk limestones at Wattendorf, Bavaria, Southern Germany, is remarkable for its completeness, unusual dentition and hints of the preservation of soft tissues, including wing membranes. The fully articulated specimen displays both jaws each side with over one hundred sub-parallel-sided teeth with a small, slightly hooked expansion at the crown tip. There are at least 480 teeth in total. The tip of the rostrum widens to a spatula-like, laterally concave structure with teeth only along its lateral margins. The straight anterior margin is devoid of teeth allowing plankton-rich water to stream in, while the teeth interdigitate forming a fine mesh trap. A slightly up swept rostrum assisted filtering by probable pulsating movements of the long neck, while wading or swimming through shallow water.

The paleontological diversity of Mesozoic marine reptiles in northeastern Mexico shows an extensive fossil record, composed of different orders, including Ichthyosauria, a group with reports in Jurassic formations of the region. This paper presents two specimens collected in Galeana, Nuevo Leon, comprised by postcranial elements, from the La Caja Formation, of the Upper Jurassic. The mentioned specimens increase the fossil record of the area and contribute to the greater understanding of the fauna and paleoecological diversity of the PaleoGulf of Mexico during the Upper Jurassic.

La diversidad paleontológica de reptiles marinos mesozoicos en el noreste de México demuestra un registro fósil considerable, compuesto por distintos órdenes, incluyendo Ichthyosauria, grupo que presenta reportes en formaciones del Jurásico de la región. Este trabajo presenta dos ejemplares colectados en Galeana, Nuevo León; los cuales están constituidos por elementos postcraneales, procedentes de la Formación La Caja, del Jurásico Superior. Estos complementan el registro fósil de la zona y contribuyen al mayor entendimiento de la diversidad faunística y paleoecológica del Paleo-Golfo de México durante el Jurásico Superior.

The Ojinaga Basin is crucial for understanding the southern province of Laramidia because it contains a unique dinosaur fauna on the North American continent. The Upper Cretaceous Aguja and Javelina formations contain fossil remains of the dinosaur families Hadrosauridae, Ceratopsidae, Nodosauridae, Tyrannosauridae, and Saltasauridae. The latter is the first evidence for a saltasaurid taxon from Mexico identified as Alamosaurus sanjuanensis.

New hadrosaurid postcranial material is reported, collected near Presa San Antonio, Parras de la Fuente municipality, Coahuila, Mexico, in a sedimentary sequence belonging to the upper Campanian of the Cerro del Pueblo Formation, in the Parras Basin. The skeletal remains include partial elements from the pelvic girdle (left ilium, right pubis, ischium, and incomplete sacrum), a distal end of a left femur, almost complete right and left tibiae, right metatarsals II and IV, cervical and caudal vertebrae. Also, partially complete forelimb elements are present, which are still under preparation. The pubis shows characters of the Lambeosaurinae morphotypes, but the lack of cranial elements does not allow us to directly differentiate this specimen from the already described hadrosaurid taxa from the studied area, such as Velafrons coahuilensis, Latirhinus uitstlani, and Kritosaurus navajovius. This specimen, referred as Lambeosaurinae indet., adds to the fossil record of the hadrosaurids in southern Laramidia during the Campanian.

The publisher regrets that this article has been temporarily removed. A replacement will appear as soon as possible in which the reason for the removal of the article will be specified, or the article will be reinstated. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

At Canada Ancha, about 15 km northwest of Saltillo, northeastern Mexico, deposits of the upper Campanian-?lower Maastrichtian Cerro del Pueblo Formation exhibit bone clusters of disarticulated hadrosaurids, tentatively assigned here based on maxillary features to Velafrons coahuilensis and a second yet undetermined taxon. We discuss the taphonomy of the material as transported and buried on a delta plain. Orientation and breakage of bones as well as absence of strong abrasion indicate short-distance and high-energy transport by a viscose 'flash flood' or debris flow. (C) 2019 Elsevier Ltd. All rights reserved.

ABSTRACTBone histology grants substantial insight into the growth and biology of fossil vertebrates. Many of the major non‐avian dinosaurian clades have been extensively sampled for bone histologic data allowing reconstruction of their growth as well as the assessment of the evolution of growth changes along phylogenies. However, horned ceratopsians are poorly represented in paleohistologic studies. Further, the ceratopsian taxa that have been examined are unevenly sampled phylogenetically with very basal forms and highly derived forms making up the majority of studied taxa. In order to rectify this, we have histologically sampled Avaceratops from Montana and Yehuecauhceratops from northern Mexico to assess how mid‐sized basal centrosaurines grew relative to more basal and derived forms. Based on results from these taxa, basal centrosaurines present a mosaic of growth characters intermediate between those seen in basal ceratopsians and more derived centrosaurines. Further, Yehuecauhceratops has many lines of arrested growth preserved, suggesting that the large number of lines of arrested growth found in a high‐latitude Pachyrhinosaurus specimen may be a result of phylogeny rather than geography. Since lines of arrested growth are not preserved in long bones of many ceratopsians, especially chasmosaurines, we also histologically sampled ribs of Avaceratops and Pachyrhinosaurus. However, the largest ribs were highly remodeled obscuring lines of arrested growth, making it unlikely that rib histology will clarify growth trends in ceratopsians. These centrosaurines add to the growing ceratopsian histological database and demonstrate that basal centrosaurines grew in a manner intermediate between non‐ceratopsid taxa and derived centrosaurines. Anat Rec, 303:935–948, 2020. © 2019 Wiley Periodicals, Inc.

The record of land tetrapods of the Cerro del Pueblo Formation (Late Cretaceous, Campanian), in Coahuila, includes turtles, pterosaurs, dinosaurs, and crocodyliforms. This last group is represented only by goniopholidids, indeterminate eusuchians, and Brachychampsa montana. In this work we report the first crocodyliform remains from La Parrita locality, Cerro del Pueblo Formation, based on one isolated tooth, vertebrae, and osteoderms. The association of crocodyliforms, turtles, dinosaurs, and charophyte oogonia provide evidence for stagnant to fluvial environments on a delta plain with tropical climate for the Cerro del Pueblo Formation during the Late Cretaceous.

Here we report new hadrosaur remains recovered from the Cerro del Pueblo Formation (Upper Cretaceous: Campanian) at La Parrita locality, northeastern Mexico. Although the material is fragmentary, the identification of dental microwear in three out of the four teeth collected is notable. This sample allows for a preliminary assessment of hadrosaur dental microwear from this geographic region and time frame. The variables studied were the orientation and average count of scratches, average count of pits, and average microwear feature width in an area of 400 X 400 µm at 35X magnification. The results show a predominance of dorsodistally-ventromesially inclined scratches in all three teeth indicating that the mandible primarily moved in an orthopalinal direction during the power stroke. The pattern of scratch orientation we recorded is comparable to that reported for different hadrosaur species from Alberta, Canada, and Wyoming, U.S.A.; suggesting similar jaw mechanics in the hadrosaurs from Coahuila. In contrast, there are significant differences in the average number of pits and microwear feature width between the Alberta and the Coahuila hadrosaurs samples, with the latter presenting more pits and finer microwear features. Given the similar jaw mechanics between the Alberta and Coahuila hadrosaurs, suggested by our analysis, the difference in average number of pits and microwear feature width is probably due to differences in diet and/or the type and amount of grit ingested during feeding. The greater number of pits in the hadrosaurs from Coahuila might indicate that these individuals ingested a greater proportion of hard food items than the Alberta hadrosaurs.

The Las Aguilas locality near Porvenir de Jalpa, Coahuila, Mexico, is extremely rich in fossil remains comprising both bones and trackways of several late Campanian dinosaur taxa. Here we present a tooth with an asymmetrically bulged crown and an isolated shallow amphicoelous vertebral centrum. Both are assigned by us to Parksosauridae. The material represents the first occurrence of this enigmatic family in Mexico.