Abstract The cranial morphology of theropod dinosaurs has been used to examine the phylogeny, ontogeny, ecology and biomechanics of the clade. Previous studies have recognized that paedomorphosis and peramorphosis occurred multiple times throughout theropod evolution, with skull paedomorphism being one of the major changes during the transition from non-avialan theropods to birds. This study supplemented previous works with more detailed sampling of the morphological data of non-avialan paravians. Principal component analyses based on the cranial geometry confirm that the small-bodied non-avialan paravians have paedomorphic skulls compared with the early-diverging theropods, but independent peramorphosis is also observed in various groups. The secondary elongation of the preorbital portion of the cranium was present in both the late-diverging troodontids and the late-diverging dromaeosaurids, but it was achieved through different morphological configurations in these two lineages.

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 The Late Campanian-aged Kaiparowits Formation (72.5–76.6 Ma) is a thick, fossiliferous fluvio-overbank–lacustrine complex deposited in south-central Utah. Host to one of the richest, most diverse Campanian terrestrial fossil records in North America, the physical environment of the Kaiparowits ecosystem, particularly the dynamics of the hydrological system, remains obscure. In 2014, an extensive bonebed was found in a conglomeratic sandstone unit of fluvial origin, known as the Rainbows and Unicorns Quarry. Isotopic compositions of serially sampled tooth enamel phosphate (δ 18 O p ) from tyrannosaur teeth were analysed to see if they held data that could clarify the palaeohydrology of the Kaiparowits Formation. To assess a greater palaeoecological context for the tyrannosaurs, the isotopic composition of their teeth was compared to other faunal elements, including the giant alligatoroid Deinosuchus , and turtles (Baenid, Gilmoremys , Neurankylus and Trionychid) from the same quarry. The δ 18 O w calculated from tyrannosaur was low, suggesting that isotopically-light, high-altitude runoff strongly influenced the local hydrology of the Kaiparowtis Formation. The seasonal change in δ 18 O of tyrannosaur drinking water ranged from −21.0 to −14.4‰ V-SMOW, while δ 18 O w calculated from turtles and crocodiles ranged between an average of −9.3 and −10.9‰, respectively. The seasonal precipitation pattern and temperature of the Kaiparowits Formation was then compared to analogue settings, such as the monsoonal climate of Hanoi, Vietnam and Cuiaba, Brazil. While similarities exist between these sites, the unique configuration of the Sevier Mountains adjacent to the nearby Western Interior Seaway provides the unique setting for a complex palaeohydrological system that results in a wide range of δ 18 O w as a result of cold seasonal precipitation at high elevation that runs off and mixes with local precipitation (−6.0 to −4.68‰) sourced from the Western Interior Seaway. This study demonstrates the importance of serial- and micro-sampling of multi-taxa comparisons for isotopic investigations of palaeohydrological systems.