Abstract
The first record of fossil teleostean otoliths from Antarctica is reported. The fossils were obtained from late Early Eocene shell beds of the La Meseta Formation, Seymour Island that represent the last temperate marine climate phase in Antarctica prior to the onset of cooling and subsequent glaciation during the late Eocene. A total of 17 otolith-based teleost taxa are recognized, with 10 being identifiable to species level containing nine new species and one new genus: Argentina antarctica sp. nov., Diaphus? marambionis sp. nov., Macruronus eastmani sp. nov., Coelorinchus balushkini sp. nov., Coelorinchus nordenskjoeldi sp. nov., Palimphemus seymourensis sp. nov., Hoplobrotula? antipoda sp. nov., Notoberyx cionei gen. et sp. nov. and Cepola anderssoni sp. nov. Macruronus eastmani sp. nov. is also known from the late Eocene of Southern Australia, and Tripterophycis immutatus Schwarzhans, widespread in the southern oceans during the Eocene, has been recorded from New Zealand, southern Australia, and now Antarctica. The otolith assemblage shows a typical composition of temperate fishes dominated by gadiforms, very similar at genus and family levels to associations known from middle Eocene strata of New Zealand and the late Eocene of southern Australia, but also to the temperate Northern Hemisphere associations from the Paleocene of Denmark. The Seymour Island fauna bridges a gap in the record of global temperate marine teleost faunas during the early Eocene climate maximum. The dominant gadiforms are interpreted as the main temperate faunal component, as in the Paleocene of Denmark. Here they are represented by the families Moridae, Merlucciidae (Macruroninae), Macrouridae and Gadidae. Nowadays Gadidae are a chiefly Northern Hemisphere temperate family. Moridae, Macruroninae and Macrouridae live today on the lower shelf to deep-water or mesopelagically with Macruroninae being restricted to the Southern Ocean. The extant endemic Antarctic gadiform family Muraenolepididae is missing, as are the dominant modern Antarctic fishes of the perciform suborder Notothenioidei. Recently, there has been much debate on isolated jaw bones of teleost fishes found in the La Meseta Formation and whether they would represent gadiforms (Merlucciidae in this case) or some early, primitive notothenioid. Otoliths are known to often complement rather than duplicate skeletal finds. With this in mind, we conclude that our otolith data support the presence of gadiforms in the early Eocene of Antarctica while it does not rule out the presence of notothenioids at the same time.http://zoobank.org/urn:lsid:zoobank.org:pub:A30E5364-0003-4467-B902-43A41AD456CC
Highlights
Few fossil fish remains have been recovered from the Cenozoic of Antarctica, partly because outcrops are scarce due to ice coverage, and because Cenozoic strata were rarely identified along the islands of the Antarctic Peninsula
The Eocene La Meseta Formation on Seymour Island represents the prime location for Palaeogene fish fossils in Antarctica
The fish fauna that we describe here by means of otoliths is clearly dominated by the Gadiformes
Summary
Few fossil fish remains have been recovered from the Cenozoic of Antarctica, partly because outcrops are scarce due to ice coverage, and because Cenozoic strata were rarely identified along the islands of the Antarctic Peninsula. The Eocene La Meseta Formation on Seymour Island represents the prime location for Palaeogene fish fossils in Antarctica. The majority of otoliths described here come from Seymour Island localities IAA 1/90 (Figs 1, 2A, B; known as the ‘Ungulate site’; 64 140 04.6700 S, 56 390 56.3800 W) and IAA 2/95 (Figs 1, 2C, D; known as the ‘Marsupial site’; 64 130 5800 S, 56 39’ 0600 W) Both sites expose lenses of a shelly conglomerate at the same stratigraphical level within the Telm 5 unit that is informally referred to as the ‘Natica horizon’ (Fig. 2E), because the bioclast component of the fine to coarse sediment matrix is dominated by the naticid gastropod Polynices. According to the chronostratigraphical synthesis by Montes et al (2013), the Cucullaea I Allomember has a basal age of 52.8 Ma and a top age of 49.0 Ma, resulting in a late Early Eocene, Ypresian age, an age which is accepted here (Fig. 1)
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