New records from Banks Island expand the diversity of Eocene fishes from Canada’s western Arctic Greenhouse

Michael D Gottfried,Jaelyn J Eberle

doi:10.1139/as-2017-0007

Abstract

Eocene vertebrates from the Canadian Arctic, including sharks, bony fishes, turtles, crocodylians, birds, and mammals, have provided strong evidence for relatively warm ice-free conditions in the Arctic during the Eocene Greenhouse interval. Recent expeditions to Banks Island (Northwest Territories) in the western Arctic have recovered a relatively more marine-influenced Eocene fauna, including sand tiger sharks, bony fishes, turtle shell fragments, and a single crocodylian specimen. We report here on new additions to this fauna, including diagnostic large scales that confirm the presence of Amia in the western Arctic. One very large lateral line scale corresponds to a fish approximately 1.4 m in total length, larger than the maximum size for extant Amia calva. We also recovered approximately 100 distinctive teeth that we assign to the teleost genus Eutrichiurides, which is otherwise known from lower latitude Paleogene sites in the United States, India, Africa, and Europe. The genus is interpreted as an a...

Highlights

The discovery over the past several decades of a wide range of late early to middle Eocene vertebrates from the Canadian Arctic has been instrumental to developing the concept of the “Greenhouse Earth” interval during which global temperatures were significantly higher than at present and the Arctic experienced mild temperate conditions with above-freezing winters (Dawson et al 1976; Estes and Hutchison 1980)
The scales of Amia establish that amiid fishes were present at the far western edge of the Canadian Arctic in the Eocene, a further expansion of their previously known range from the eastern Canadian Arctic (Estes and Hutchison 1980; Eberle and Greenwood 2012) and reassuring given the uncertainty over an earlier account (Eberle et al 2014) that tentatively identified amiids on Banks Island based on less diagnostic material
Belk and Houston (2002), convincingly argued against this in their study, which included a large sample size of representatives of 18 relatively large-bodied Northern Hemisphere fish species — they concluded that North American freshwater fishes in general do not follow Bergmann’s Rule ( Amia was not included in their analysis)

Summary

Introduction

The discovery over the past several decades of a wide range of late early to middle Eocene (approximately 50–53 Ma) vertebrates from the Canadian Arctic has been instrumental to developing the concept of the “Greenhouse Earth” interval during which global temperatures were significantly higher than at present and the Arctic experienced mild temperate conditions with above-freezing winters (Dawson et al 1976; Estes and Hutchison 1980). We further expand the Eocene fish fauna from Banks Island, including an unambiguous and more informative record for amiids (Amia sp.) and a large sample of teeth of the “scombroid” teleost Eutrichiurides. These discoveries were made from strata of the lower–middle Eocene Cyclic Member of the Eureka Sound Formation at sites near the Eames River within the northern part of Aulavik National Park on northern Banks Island (Fig. 1). The new finds definitively expand the range of amiids to the western edge of the Canadian Arctic during the Greenhouse interval and add a distinctive new predatory teleost to the Arctic that is otherwise known from a range of lower latitude Eocene sites

Materials and methods

Discussion