Giant Upper Triassic bivalves of Wrangellia, Vancouver Island, Canada

One of the most distinctive components of the Late Triassic warm-water biota are alatoform, reclining bivalves of the genus Wallowaconcha. Wallowaconcha raylenea was first described from shallow-water, fine-grained Upper Triassic carbonate rocks of the Wallowa terrane, northeastern Oregon, and later found in coeval limestone in the Yukon. Fossils of the family Wallowaconchidae are easily recognized and readily distinguished from other fossil groups by their large size (over a metre in length), alatoform morphology, and especially the chambered wing-like extensions likely associated with photosymbiosis. Several different taxa of Norian age inhabited lagoon and reef-related settings on four separate terranes of western North America (Antimonio terrane, Sonora, Mexico; Wallowa terrane, northeastern Oregon; Stikine terrane in the Yukon; Chulitna terrane of Alaska), which during Triassic time existed as volcanic islands in the eastern Panthalassa Ocean. Outside eastern Panthalassa in the eastern Tethys, two other species of Wallowaconcha come from distant localities in Asia and Arabia. We here report for the first time, in presumed Rhaetian limestone of the upper part of the Parson Bay Formation, Vancouver Island, newly discovered examples of Wallowaconcha. They are from Wrangellia and, based on size and shape of the chambers, are assignable to W. raylenea but unlike other examples they appear to be Rhaetian in age. This species of giant bivalve inhabited warm-water locales outboard of North America during the Late Triassic, and its presence provides possible paleobiogeographic links of Wrangellia with both Stikinia and the Wallowa terrane.

Systematic analysis of Upper Triassic silicified scleractinian corals from Wrangellia and the Alexander Terrane, Alaska and British Columbia

Acid processing allowed systematic identification of 458 Upper Triassic silicified scleractinian corals (20 genera, 47 species) from the Alexander terrane (southeast Alaska) and Wrangellia (Wrangell Mountains, southern Alaska and Vancouver Island, Canada). Coral faunas, here presented, show taxonomic affinity with coeval collections from other Cordilleran terranes, specifically the Wallowa terrane (northeastern Oregon and Idaho) and Peru (South America) as well as the distant Tethys region. Genera from the Alexander terrane include: Kompsasteria Roniewicz, Gablonzeria Cuif, Cuifia Melnikova, Paracuifia Melnikova, Distichophyllia Cuif, Retiophyllia Cuif, Kuhnastraea Cuif, Margarosmilia Volz, Distichomeandra Cuif, Astraeomorpha Reuss, Pamiroseris Melnikova, Crassistella Roniewicz, Stylophyllum Frech, and Meandrostylis Frech. Genera from Wrangellia include: Gablonzeria Cuif, Distichophyllia Cuif, Retiophyllia Cuif, Kuhnastraea Cuif, Margarosmilia Volz, Distichomeandra Cuif, Astraeomorpha Reuss, Parastraeomorpha Roniewicz, Chondrocoenia Roniewicz, Pamiroseris Melnikova, Crassistella Roniewicz, Ampakabastraea? Alloiteau, Recticostastraea Stanley and Whalen, Meandrostylis Frech, Anthostylis Roniewicz, and the new genus Campesteria n. gen. New species include: Gablonzeria grandiosa n. sp., Paracuifia smithi n. sp., Paracuifia jennieae n. sp., P. anomala n. sp., Retiophyllia dendriformis n. sp., R. obtusa n. sp., and Campesteria prolixia n. sp.