|North America during the Campanian|
Appalachian dinosaurs differ sufficiently from their Laramidian cousins to imply a lengthy period of isolation—all of Appalachia’s dinosaurs must have migrated over there prior to the appearance of the WIS. Once the WIS receded at the end of the Campanian (it was gone completely by the Maastrichtian), dinosaurs from Laramidia and Appalachia were free to comingle—if they did at all, but poor sampling in the eastern United States (there’s a paucity of Late Cretaceous exposures) is an omnipresent frustration.
Anyway, in 2016, Longrich published on a partial ceratopsianmaxilla from North Carolina (paywalled). It is very small and there aren’t any teeth in it,
but Longrich ascribes it to the Leptoceratopsidae. However, Andy Farke has told me it could also simply be from a basal neoceratopsians like Aquilops. To me, this diagnosis is the safer bet.
Saying it’s a leptoceratopsid demands that leptoceratopsids evolved prior to
the appearance of the WIS and that they migrated not just from Asia to North
America but from Asia to Eastern
North America by the Campanian. Given that the rest of Appalachia’s dinosaurs
are seemingly from more plesiomorphic stock than their Laramidian counterparts,
it makes more sense to—at this juncture—call it a basal neoceratopsian and
leave it at that.
|The North Carolina ceratopsian|
|The Mississippi ceratopsid tooth|
didn’t do well when submerged), the Mississippi ceratopsid must have been a western immigrant.