31 Amia cf. pattersoni from the Paleocene Paskapoo Formation of Alberta Lance Grande, Li Guo-Qing, and Mark V. H. Wilson Abstract: A well-prepared anterior half of an amiid skull from the Late Paleocene Paskapoo Formation of south-central Alberta is described. The specimen is either very closely related to, or conspecific with, Amia pattersoni Grande and Bemis, 1998, from the Early Eocene Green River Formation of Wyoming. We leave the specimen as Amia cf. pattersoni until additional material is found to further clarify its relationships. Amia cf. pattersoni is the oldest known specimen clearly identifiable as belonging to the genus Amia (sensu Grande and Bemis, 1998), and the Paskapoo spe- cies extends the known geographic range of Amia both northward and westward. The fish assemblage of the Paskapoo Formation represents the most diverse freshwater Paleocene fish fauna known from North America. Based on compari- sons of sample size and relative taxonomic diversity to the better known Green River Formation localities of Wyoming, we predict that further collecting will substantially increase the known diversity of the Paskapoo fauna. The Paskapoo Formation, therefore, has great potential to continue adding to the meager knowledge of pre-Eocene freshwater teleost diversity in North America. Résumé : Ce document décrit une moitié antérieure bien préparée d'un crâne d'un aminoïde de la Formation de Paska- poo du Paléocene tardif. Le spécimen est soit relié très étroitement à Amia cf. pattersoni Grande et Bemis, 1998 de la Formation de Green River de l'Éocène précoce, au Wyoming, soit qu'il lui est congénère. Nous classons le spécimen en tant que Amia cf. pattersoni jusqu'à ce qu'il y ait plus de matériel pour mieux clarifier ses relations. Amia cf. patter- soni est le plus ancien spécimen connu que l'on peut identifier clairement comme faisant partie du genre Amia (sensu Grande et Bemis, 1998) et l'espèce de Paskapoo agrandit l'étendue géographique connue de Amia à la fois vers le nord et vers l'ouest. L'assemblage de poissons de la Formation de Paskapoo représente la faune la plus diversifiée connue de poissons d'eau douce du Paléocène en Amérique du Nord. En comparant des tailles d'échantillons et la diversité taxo- nomique relative aux localités mieux connues de la Formation de Green River au Wyoming, nous pouvons dire avec certitude que la poursuite de l'échantillonnage augmentera de façon substantielle le diversité connue de la faune de Pas- kapoo. La Formation de Paskapoo a donc un grand potentiel contribuer de façon marquée au très peu de connaissances actuelles sur la diversité des poissons téléostéens du pré-Éocène en Amérique du Nord. [Traduit par la Rédaction] Grande et al. 37 Introduction the Paskapoo Formation will be described in a larger study of fossil and living gars.2 Previous descriptions of the other The Late Paleocene Paskapoo Formation of south-central Paskapoo fishes are as follows. Occurrence in Alberta of Alberta contains the most diverse freshwater Paleocene fish amiids in what is now considered to be the genus Cyclurus assemblage known from North America. Although some has been known since 1928 in deposits of both Paleocene taxa in the formation are so far represented only by scales, and Late Cretaceous ages. The nominal taxa Kindleia isolated bones, or parts of the caudal region (i.e., the amiid fragosa Jordan 1927 (Late Cretaceous) and Stylomyleodon Cyclurus, Gonorynchidae, Cyprinoidea, and Asineopidae), lacus Russell 1928a (Paleocene) were both established for others are represented by articulated, nearly complete skele- amiids with flattened, crushing teeth, based on fragments of tons (Lepisosteidae, Osteoglossidae, Esocidae and jaw bones and associated disarticulated material. Contro- Percopsidae), or a partial skull (the amiid Amia cf. versy about the generic (e.g., Russell 1928b) and specific pattersoni described herein). The lepisosteid skeletons from (e.g., Gaudant 1992) distinctiveness of Russell’s Paleocene species has recently been resolved as follows. Jordan’s Late Received April 9, 1999. Accepted October 20, 1999. Cretaceous species is now classified by Grande and Bemis L. Grande.1 Department of Geology, Field Museum of (1998) as Cyclurus fragosus (Jordan), whereas Russell’s Natural History, Roosevelt Road at Lake Shore Drive, Paleocene species is treated as a nomen dubium, Cyclurus Chicago, IL 60605, U.S.A. "lacus" (Russell), by the same authors. Nevertheless, it dem- Li G.-Q. Institute of Vertebrate Paleontology and onstrates the presence of the genus Cyclurus in the Paleoanthropology, Academia Sinica, P. O. Box 643, Beijing Paleocene assemblage. Grande and Bemis (1998) also 100044, China. briefly reported that a specimen assignable to Amia existed Li G.-Q. (present address) and V.H. Wilson. Department of in the collections of the University of Alberta. That speci- Biological Sciences, University of Alberta, Edmonton, AB men is the subject of the present paper. T6G 2E9, Canada. Osteoglossidae were described based on isolated bones by 1Corresponding author (e-mail: [email protected]). Wilson (1980), and the genus Joffrichthys was established 2Work by Grande and Bemis currently in progress. based on articulated skeletons by Li and Wilson (1996). Can. J. Earth Sci. 37: 31–37 (2000) © 2000 NRC Canada 32 Can. J. Earth Sci. Vol. 37, 2000 Hiodontidae were reported by Wilson (1980) on the basis of nasal; pas, parasphenoid; pastp, parasphenoid tooth patch; scales, isolated skull bones, and a partial caudal skeleton, pmx, premaxilla; po, postinfraorbitals; ro, rostral bone; smx, but later discoveries proved that all of these fragments can supramaxilla; so, subinfraorbital. be referred to the osteoglossid Joffrichthys (Li and Wilson 1996). Gonorynchidae were reported based on scales and Systematic paleontology isolated skull bones (including a peculiar clefted subopercle indicative of the genus Notogoneus) by Wilson (1980). Subclass Actinopterygii Cope, 1887 Cyprinoidea (probably catostomids) were recorded based on (sensu Rosen et al., 1981) isolated cleithra by Wilson (1980). Esocidae were described Series Neopterygii Regan, 1923 based on isolated bones and several articulated skeletons by (sensu Rosen et al., 1981) Wilson (1980, 1984). Asineopidae were reported based on Division Halecostomi Regan, 1923 isolated scales and skull bones by Wilson (1980). Percopsidae were briefly reported based on isolated bones (sensu Patterson, 1973) by Wilson (1980); Wilson also mentioned, but did not de- Subdivision Halecomorphi Cope, 1872 scribe, partial skeletons. Murray and Wilson (1996) and (sensu Patterson, 1973) Murray (1996) later described nearly complete skeletons that Order Amiiformes Hay 1929 they assigned to two different genera of Percopsidae. (sensu Grande and Bemis, 1998) Percopsid species make up about 95% of the approximately Superfamily Amioidea Bonaparte, 1838 2000 articulated fish skeletons known from the Paskapoo (sensu Grande and Bemis, 1998) Formation. The University of Alberta specimen assigned by Grande Family Amiidae Bonaparte, 1838 and Bemis (1998) to Amia is the first articulated specimen of (sensu Grande and Bemis, 1998) an amiid yet found in the Paleocene of western Canada. Al- Subfamily Amiinae Bonaparte, 1838 though incomplete, consisting only of the anterior half of the (sensu Grande and Bemis, 1998) skull, it is extremely well preserved. In the present paper, we Genus Amia Linnaeus, 1766 fully describe the specimen, place it in phylogenetic context, (sensu Grande and Bemis, 1998) and review the potential of the Paskapoo Formation to yield increased diversity of Paleocene freshwater fishes. Remarks Grande and Bemis (1998, p. 32), in a comprehensive revi- Materials sion of Amiidae, provided an emended diagnosis for the ge- For a list of amiine specimens examined, see Grande and nus Amia. Characters used to distinguish the genus Amia Bemis (1998). Nominal species from that list reexamined from Cyclurus (another genus in the subfamily Amiinae) in- here include the following: Amia calva Linnaeus, 1766; clude the following: (1) the presence of sharply pointed teeth Amia scutata Cope, 1875; Amia pattersoni Grande and on the anterior coronoids and vomers (versus styliform teeth Bemis, 1998; Amia "robusta" Priem, 1901; "Amia" hesperia on the anterior coronoids and vomers in Cyclurus); (2) long Wilson, 1982; Stylomyleodon lacus Russell, 1928 and narrow tooth patch extending well anterior to the later- (= Cyclurus "lacus" (Russell)); Amia kehreri Andreae, 1893 ally pointing ascending rami of the parasphenoid (versus a (= Cyclurus kehreri (Andreae)); Paramiatus gurleyi Romer shorter tooth patch in Cyclurus; see Grande and Bemis and Fryxell, 1928 (= Cyclurus gurleyi (Romer and Fryxell)); 1998: Fig. 135); and (3) a high number of preural centra, ir- Amia efremovi Sytchevskaya, 1981 (= Cyclurus efremovi relevant with regard to the fossil being described here, which (Sytchevskaya)); Kindleia fragosa Jordan, 1927 (= Cyclurus is missing the vertebrae. fragosus (Jordan)). For an explanation of use of quotation The Paskapoo amiid skull described herein has features marks, see Grande and Bemis (1998, p.19 for genera, (1) and (2) (discussed in description), which identify it as pp. 315, 316 for species). belonging to the genus Amia and as being the oldest and northernmost occurrence of the genus sensu Grande and Abbreviations Bemis, 1998. The specimen has some additional features, strongly resembling those of Amia pattersoni Grande and Institutional Bemis (1998) and discussed after the description