The horned dinosaurs Pentaceratops and Kosmoceratops from the upper Campanian of Alberta and implications for dinosaur biogeography
Author:
Longrich
Abstract:
The upper Campanian of the American Southwest has produced dinosaurs that are unknown from the northern Great Plains and vice versa. This has led to the idea that North America's Campanian dinosaur fauna was characterized by high levels of endemism and distinct faunal provinces. Here, two horned dinosaurs known from the Southwest, Pentaceratops and Kosmoceratops, are described from southern Canada. Pentaceratops aquilonius sp. nov. is represented by two frill fragments from the uppermost Dinosaur Park Formation near Manyberries, southeast Alberta. Features shared with Pentaceratops include large, triangular epiparietals, an M-shaped parietal posterior bar, and an epiparietal P1 that curls up and twists laterally. The Manyberries specimens differ from Pentaceratops sternbergii and Utahceratops gettyi in that the posterior bar is broader, emargination is weakly developed, and P1 is directed dorsally, rather than anteriorly. Phylogenetic analysis places P. aquilonius as sister to a clade comprising P. sternbergii and Utahceratops. Kosmoceratops is documented by a partial skull from Dinosaur Provincial Park. Previously referred to Chasmosaurus, the skull exhibits derived features inconsistent with this referral, including a reduced septal flange, a caudally inclined narial strut, a triangular narial process, a reduced frontal fontanelle, a weakly hooked rostral, and a narrow, caudally inclined internal naris. Phylogenetic analysis recovers the animal as sister to Kosmoceratops richardsoni, but differences in the shape of the naris and nasal horn suggest that it likely represents a distinct species. The presence of Pentaceratops and Kosmoceratops in Canada argues against the idea of distinct northern and southern faunal provinces, but the fact that they differ from their southern relatives confirms that endemism was high in the Campanian. The ability of dinosaur lineages to disperse long distances across North America suggests that dinosaur distribution was not constrained by geographic barriers, climate, or flora. Instead, dinosaur endemism may result from competitive exclusion of immigrants by established populations adapted to local environmental conditions.
Upper Triassic Corals from Nevada, Western North America, and the Implications for Paleoecology and Paleogeography
Authors:
1. Ewa Roniewicz (a)
2. George D. Stanley, Jr. (b)
Affiliations:
a. Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00–818 Warszawa, Poland, < eron.twarda@pan.pl>
b. The University of Montana Paleontology Center, Missoula MT 59812, USA, < george.stanley@umontana.edu>
Abstract:
Late Carnian–early Norian corals from the Luning and Osobb formations in west-central Nevada represent an important Late Triassic fauna for understanding the paleoecology and the paleogeography of the eastern Panthalassa region during Late Triassic time. The corals occur in bedded limestone representing biostromes and patch reefs and their composition presages the important global changeover of faunas of the intra-Norian interval. A taxonomic analysis of over 60 specimens reveals a majority of colonial corals ranging from cerioid, astreoid (i.e., cerioid-plocoid lacking walls), meandroid and thamnasterioid types. Surprisingly, remnants of the original aragonite microstructure remain in some specimens, allowing a better comparison with more remote Tethyan corals. In total, 14 genera have been identified from Nevada while two genera remain undetermined. The fauna is composed of species considered typical of both the North American Cordillera and cratonal South America. The following genera and species are new and endemic to the Americas: Khytrastrea silberlingi and K. cuifiamorpha, Flexastrea serialis, Nevadoseris punctata, Areaseris nevadaensis and a new genus Minasteria (with Astrocoenia shastensis Smith, 1927 as type species). Likewise are the new species: Margarogyra silberlingi and Curtoseris dunlapcanyonae. Genera Meandrovolzeia, Margarogyra, Ceriostella, Ampakabastraea, Retiophyllia, Distichomeandra, Curtoseris, Thamnasteria and Astraeomorpha provide important links to the former Tethys province. The revised coral fauna changes previous views of the close taxonomic similarity with the Tethys, instead producing a paleogeographic pattern emphasizing a much greater degree of endemism. This pattern emphasizes the isolation of Nevada from the Tethys and the similarities with some outboard terranes of the Cordillera.
Pop sci
write ups abound.
However, the tPotRSb has not yet released the open access paper to the public as of my writing.
It's available now
here and open access.
