The late Eocene–early Oligocene ichthyofauna from the Eastend area of the Cypress Hills Formation, Saskatchewan, Canada

Abstract

The Eocene through Miocene Cypress Hills Formation of Saskatchewan and Alberta has been the basis of studies on sedimentology, paleobotany, herpetofauna, avifauna, and mammalian local faunas. We describe the ichthyofauna from the Eastend area of the formation, representing late Eocene Chadronian to early Oligocene Whitneyan deposits. This fauna is diverse, including at least 14 fish taxa: Lepisosteus, Amiinae, aff. Hiodon, at least three cypriniforms among which is a Ptychocheilus-like leuciscine and at least one catostomid, two ictalurids, both ascribed to Astephus, a probable salmoniform, an amblyopsid-like percopsiform, Mioplosus, a probable moronid, a centrarchid, and at least one other perciform of uncertain affinity. The formation may therefore represent the first fossil record of the Amblyopsidae, and the first North American occurrence of the Moronidae. The composition of the ichthyofauna suggests higher temperatures during the Eocene-Oligocene transition than at present. Paleotemperatures similar to those of the Gulf Coast of the United States are indicated by the present ranges of several taxa, as well as by the large sizes attained by some of these fishes. The high relative abundance of abraded ictalurid material representing small individuals suggests that much of the formation was deposited in shallow, hypoxic floodplain pools that may have seasonally dried out. However, the large sizes attained by some taxa and the diversity of the fauna as a whole indicate that the neighboring aquatic environments were diverse, with welloxygenated, vegetated, permanent, and deep-water environments. This suggests the presence of a mosaic of conditions, such as is found in large floodplains.

NEW OCCURRENCE OF Lepisosteid remains (LEPISOSTEIFORMES: LEPISOSTEOIDEA) FROM THE CENOMANIAN OF THE ALCANTARA FORMATION (UPPER CRETACEOUS), MARANHÃO STATE, BRAZIL = NOVA OCORRÊNCIA DE RESTOS DE LEPISOSTEÍDEOS (LEPISOSTEIFORMES: LEPISOSTEOIDEA) DO CENOMANIANO DA FORMAÇÃO ALCÂNTARA (CRETÁCEO SUPERIOR), ESTADO DO MARANHÃO, BRASIL

“…The specimens were obtained through sediment sifting of samples collected in 2003 and stored at the fossil collection of the Centro de Pesquisa de História Natural e Arqueologia do Maranhão (CPHNAMA), where they were registered as VT-1541 (teeth) and VT-1540 (vertebrae). Their descriptions were based on Grande (2010) monography; and Divay & Murray (2015), which pertain to details of the vertebrae neural and haemal arches, with some nomenclatural differences.…”

“…Isolated materials such as scales and teeth represent the most common fossil remains of gars, and in addition to the few lepisosteoid vertebrae, they provide an important record favoring the understanding of the historic distribution of the group (Moody & Sutcliffe, 1991;Gottfried & Krause, 1998;Kear et al, 2009;Divay & Murray, 2015;Martinelli & Teixeira, 2015;Pérez-García et al, 2016;Szabó et al, 2016;Alves et al, 2020;Kovalchuk & Anfimova, 2020). The vertebrae with opisthocoelous centra and teeth with plicidentine are useful for identifying fragmentary fossil specimens, once they are diagnostic for Lepisosteoidea and Lepisosteidae, respectively (Grande, 2010;López-Arbarello, 2012).…”