The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)

Abstract

Ceratopsids (“horned dinosaurs”) are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

A highly pneumatic middle Cretaceous theropod from the British Lower Greensand

“…Diagnostic Aptian dinosaur material is rare in the European fossil record as a whole, probably due to a return to marine conditions following the early Aptian transgression (Hopson 2011). Non‐bird dinosaur remains are considered uncommon in marine sediments (Pasch & May 1997), and are often fragmentary (Farke & Phillips 2017), although their rarity may reflect a collection bias in some localities (Horner 1979). Several mechanisms have been suggested for the allochthonous or parautochthonous presence of dinosaurs in marine sediments (Benton et al .…”

“…2017; Longrich et al . 2017; although marginocephalians are notably scarce: Farke & Phillips 2017) and some marine sediments, such as those of the Middle and Upper Jurassic of England (Benton et al . 1995; Martill et al .…”

The first <i>in situ</i> collection of a mosasaurine from the marine Breien Member of the Hell Creek Formation in south-central North Dakota, USA

“…The persistence of the mosasaurine lineage through the end of the Cretaceous is documented at other sites across the planet, including specimens of both Mosasaurus and Prognathodon recovered just below the K-Pg boundary in the Upper Maastrichtian Formation in The Netherlands, the Hornerstown Formation of New Jersey, and the Prairie Bluff Chalk of Alabama (Kiernan 2002, Jagt et al 2008, Gallagher et al 2012. Mosasaurine fossils recovered at other localities in close association with the K-Pg boundary in North America, such as the Tanis site in southwestern North Dakota and the Owl Creek Formation in both Mississippi and Missouri, may be either reworked from underlying deposits or transported out of context by the aftereffects of the Chicxulub impact (Gallagher 2005, Farke and Phillips 2017, DePalma et al 2019. Kiernan (2002) identified mosasaurine mosasaurs just below the K-Pg boundary in the Prairie Bluff Chalk, which has an age range of 68-67 Ma, whereas NDGS locality L301 is closer to 66 Ma.…”

An Appalachian population of neochoristoderes (Diapsida, Choristodera) elucidated using fossil evidence and ecological niche modelling

“…The presence of neochoristoderes in the latest Campanian to earliest Maastrichtian of the Atlantic coastal plain also has interesting implications for the movement of this group within North America. Several species of dinosaurs, including ceratopsians (Farke & Phillips 2017), tyrannosaurs (Brownstein 2018), dromaeosaurs (Brownstein 2019), hadrosaurs (Gallagher 1993) and ornithomimosaurs (Brusatte et al . 2012), from the Maastrichtian of the Navesink Formation and coeval formations in the Atlantic coastal plain, have been recovered as close relatives to Laramidian taxa.…”