Abstract Starting in the early 1950s, palaeontologists began to discover a wide range of Cretaceous terrestrial fossils in the Laiyang, Qingshan and Wangshi groups of the Jiaolai Basin, which resides in the eastern part of the Shandong Peninsula of northern China. Significant specimens from these deposits include various dinosaur eggs, footprints and fossils, including hadrosauroids, tyrannosaurids and ankylosaurids. These expanded the understanding of evolution, biodiversity and palaeoecology in East Asia. While many examples of the Jehol Biota from this area are not well constrained in terms of their stratigraphy and geochronology, previous studies have generally suggested that fossils from this region represent the second or third phase of Jehol Biota development. This paper reviews fossils, stratigraphic correlations, tectonic history and age estimates for the less well-studied outcrops of the Shandong Peninsula that host the Jehol Biota. We report three new 40 Ar/ 39 Ar ages for the Qingshang Group and discuss how these somewhat imprecise ages still constrain chronostratigraphic interpretation for the fossil-rich units.

ABSTRACT In 2017–2018, two fine arts undergraduate students, Todd Rowan and Moesha Wright, conceived and created a mural for the Dunn-Seiler Museum at Mississippi State University, Mississippi, USA, under the supervision of art professor emeritus Brent Funderburk. Students researched, conceptualized, and painted Mississippi Cretaceous Panorama , which interpreted the Late Cretaceous landscape that once surrounded the university and the momentous extinction event that brought the Mesozoic Era to its close. The project necessitated creativity to address several challenges, including funding, space constraints, and a local population with Young Earth views. The completed mural engages museum visitors with a mosasaur, ceratopsian dinosaur, and a meteorite impact—illustrating the local, terminal Mesozoic geologic history in a nonthreatening venue that can improve community geoliteracy.

Abstract Mesozoic dinosaur fossils are exceptionally rare in Scandinavia. The Swedish record is typically depauperate, with the Kristianstad Basin of Skåne (Scania) yielding all of the known fossils from Swedish Cretaceous strata. Although highly fragmentary, these body remnants are important because they provide evidence of a relatively diverse fauna, including previously recognized hesperornithiform birds and leptoceratopsid ceratopsians, as well as indeterminate ornithopods that are confirmed here for the first time. In this paper, we describe three phalanges (from Åsen) and an incomplete right tibia (from Ugnsmunnarna) from the Kristianstad Basin. One of the phalanges appears to pertain to a leptoceratopsid ceratopsian, providing further evidence of these small ornithischians in the Cretaceous sediments of Sweden. The other two phalanges are interpreted as deriving from small ornithopods similar to Thescelosaurus and Parksosaurus . The tibia appears to represent the first evidence of a non-avian theropod dinosaur in the Cretaceous of Sweden, with a previous report of theropod remains based on fish teeth having been corrected by other authors. The remains described herein provide important additions to the enigmatic dinosaurian fauna that inhabited the Fennoscandian archipelago during the latest Cretaceous.

The record of dinosaurs over the last 10 m.y. of the Cretaceous, as well as surrounding the Cretaceous-Paleogene boundary, helps to define extinction scenarios. Although Late Cretaceous dinosaur fossils occur on all present-day continents, only in North America do we find a terrestrial vertebrate fossil record spanning the Cretaceous-Paleogene boundary, although promising work may yield comparable records in South America, India, China, and Europe. For the present then, the North American record represents the proxy for our knowledge of dinosaur extinction. Over the last 10 m.y. of the Cretaceous (late Campanian to late Maastrichtian) in the northern part of the western interior of North America, the number of nonavian dinosaur species dropped from 49 to 25, almost a 50% reduction, even though a 16% greater extent of fossil-bearing exposures record the last dinosaurs in the latest Cretaceous in the western interior. Important, but less-well-exposed, nonavian-dinosaur–bearing units suggest this drop occurred around, or at least commenced by, the Campanian-Maastrichtian boundary. These losses began during climatic fluctuations, occurring during and possibly in part caused by the last major regressive cycle of the Cretaceous, which also reduced the expanse of the low coastal plains inhabited by nonavian dinosaurs. The pulse of Deccan Trap emplacement that began some time later in the latest Cretaceous was also likely a major driver of climatic change. As for the dinosaur record near the Cretaceous-Paleogene boundary, even the best-known records from North America remain enigmatic and open to interpretation. Newer studies suggest some decline in at least relative abundance approaching the Cretaceous-Paleogene boundary, but the cause (or causes) for the final extinction (if it was the case) of non-avian dinosaurs remains unresolved, although the Chicxulub impact undoubtedly played a major role.

Here we provide a survey of Triceratops localities and accompanying stratigraphic data from the Hell Creek Formation of northeastern Montana. The majority of the sites discussed here were relocated or discovered during the last 5 yr of the Hell Creek Project (1999–2010), a multi-institutional effort to record a large volume of faunal, floral, and geologic data on the Hell Creek Formation in order to test evolutionary, paleoecological, and geological hypotheses. Triceratops is the most abundant dinosaur in the Hell Creek Formation and one of the most common nonavian dinosaurs of the Upper Cretaceous. It is known from hundreds of specimens, which have been collected since it was first described in 1889. Although these specimens provide a wealth of morphological data on Triceratops , many lack detailed stratigraphic information and context. Detailed stratigraphic and contextual data for more than 70 specimens of Triceratops collected during the Hell Creek Project make this data set among the most comprehensive for any nonavian dinosaur.

Here, we describe a juvenile Triceratops sp. skull, UCMP 136306, from the Hell Creek Formation, McCone County, Montana. The relative completeness and superb preservation of this skull contribute to an improved understanding of the cranial ontogeny, morphology, and individual variation in Triceratops . Total skull length is 120 cm long (est.). UCMP 136306 is one of the most complete Triceratops skulls of this ontogenetic stage yet known. The cranial sutures are patent, and most are overlapping with minimal sinuosity, modest interdigitation, and overlapping flat sutural surfaces. The following cranial elements are preserved and described in this study: epinasal, rostral, quadrate, quadratojugal, jugal, pterygoid, dentary, surangular, postorbital horn, parietal, squamosal, epiparietal, episquamosal, occipital condyle, supraoccipital, and exoccipital. For decades following the initial description of Triceratops by O.C. Marsh in 1889, the typical collector attitude was “bigger is better.” Emerging scientific institutions and museums with newly constructed exhibit halls demanded the biggest and newest dinosaurs. We hypothesize that this historical practice, influenced by facies and taphonomic factors in the Upper Cretaceous Hell Creek Formation, Montana (and contemporaneous formations in neighboring states), resulted in the underrepresentation of nonadult Triceratops in museum collections. This practice contributed to the false notion that nonadult Triceratops specimens are rarely preserved in the fossil record, until now.

Ceratopsid dinosaurs are notable for their common occurrences in bonebeds; however, until recently, these have not been encountered for the chasmosaurine Triceratops . The aim of this investigation is to describe the taphonomy of Quittin' Time (Museum of the Rockies locality HC-430), a Triceratops bonebed in the Hell Creek Formation, Garfield County, Montana. Using site taphonomic descriptions with an evaluation of ontogeny, inferences regarding the paleobiology of this extinct taxon are possible. The locality is associated with abundant organic material, including woody debris, large seeds, and other fragments in isolated silty lenses, all incorporated within a siltstone matrix, indicating preservation within a floodplain environment. Based on the repetition and ontogenetic stages of cranial elements, the minimum number of individuals (MNI) is three. Evidence from the location and taphonomic condition of the bones preserved in close proximity within the same siltstone unit suggests that the individuals—one young adult, one subadult, and a juvenile—likely accumulated during distinct flooding events within a narrow region of the floodplain as a result of “bloat-and-float” transport. The relatively small scale of the bonebed, both in terms of total area and number of individuals, implies that future work on Triceratops sites requires careful scrutiny of cranial elements examined within an ontogenetic framework because they are potentially critical to establishing MNI. Preservation of multiple individuals within the same unit does not necessarily provide evidence of gregarious behavior in Triceratops but rather may be a reflection of site taphonomic history and accumulation processes.