Background Discovery of Eocene non-marine vertebrates, including crocodylians, turtles, bony fishes, and mammals in Canada’s High Arctic was a critical paleontological contribution of the last century because it indicated that this region of the Arctic had been mild, temperate, and ice-free during the early – middle Eocene (~53–50 Ma), despite being well above the Arctic Circle. To date, these discoveries have been restricted to Canada’s easternmost Arctic – Ellesmere and Axel Heiberg Islands (Nunavut). Although temporally correlative strata crop out over 1,000 km west, on Canada’s westernmost Arctic Island – Banks Island, Northwest Territories – they have been interpreted as predominantly marine. We document the first Eocene bony fish and crocodyliform fossils from Banks Island. Principal Findings We describe fossils of bony fishes, including lepisosteid (Atractosteus), esocid (pike), and amiid, and a crocodyliform, from lower – middle Eocene strata of the Cyclic Member, Eureka Sound Formation within Aulavik National Park (~76°N. paleolat.). Palynology suggests the sediments are late early to middle Eocene in age, and likely spanned the Early Eocene Climatic Optimum (EECO). Conclusions/Significance These fossils extend the geographic range of Eocene Arctic lepisosteids, esocids, amiids, and crocodyliforms west by approximately 40° of longitude or ~1100 km. The low diversity bony fish fauna, at least at the family level, is essentially identical on Ellesmere and Banks Islands, suggesting a pan-High Arctic bony fish fauna of relatively basal groups around the margin of the Eocene Arctic Ocean. From a paleoclimatic perspective, presence of a crocodyliform, gar and amiid fishes on northern Banks provides further evidence that mild, year-round temperatures extended across the Canadian Arctic during early – middle Eocene time. Additionally, the Banks Island crocodyliform is consistent with the phylogenetic hypothesis of a Paleogene divergence time between the two extant alligatorid lineages Alligator mississippiensis and A. sinensis, and high-latitude dispersal across Beringia.
References
[1]
Dawson MR, West RM, Raemakers P, Hutchison JH (1975) New evidence on the paleobiology of the Paleogene Eureka Sound Formation, Arctic Canada. Arctic 28: 110–116. doi: 10.14430/arctic2822
[2]
Dawson MR, McKenna MC, Beard KC, Hutchison JH (1993) An Early Eocene Plagiomenid Mammal from Ellesmere and Axel Heiberg Islands, Arctic Canada. Kaupia 3: 179–192.
[3]
Estes R, Hutchison JH (1980) Eocene lower vertebrates from Ellesmere Island, Canadian Arctic Archipelago. Palaeogeography, Palaeoclimatology, Palaeoecology 30: 325–347. doi: 10.1016/0031-0182(80)90064-4
[4]
Irving E, Wynne PJ (1991) The paleolatitude of the Eocene fossil forests of Arctic Canada. In Christie, RL, McMillan, NJ, editors. Tertiary Fossil Forests of the Geodetic Hills, Axel Heiberg Island, Arctic Archipelago: Geological Survey of Canada Bulletin 403: 209–212.
[5]
Miall AD (1979) Mesozoic and Tertiary geology of Banks Island, Arctic Canada – The history of an unstable craton margin. Geological Survey of Canada Memoir 387. 235 p.
[6]
Dawson MR, West RM, Hickey LJ (1984) Paleontological evidence relating to the distribution and paleoenvironments of the Eureka Sound and Beaufort formations, northeastern Banks Island, Arctic Canada. Current Research, Part B, Geological Survey of Canada, Paper 84–1B: 359–361. doi: 10.4095/119593
Eberle JJ, Greenwood DR (2012) Life at the top of the greenhouse Eocene world – A review of the Eocene flora and vertebrate fauna from Canada’s High Arctic. GSA Bulletin 124: 3–23. doi: 10.1130/b30571.1
[9]
Sluijs A, Schouten S, Donders TH, Schoon PL, R？hl U, et al. (2009) Warm and wet conditions in the Arctic region during Eocene Thermal Maximum 2. Nature Geoscience 2: 1–4. doi: 10.1038/ngeo668
[10]
Moran K, Backman J, Brinkhuis H, Clemens SC, Cronin T, et al. (2006) The Cenozoic palaeoenvironment of the Arctic Ocean. Nature 441: 601–605. doi: 10.1038/nature04800
[11]
Markwick PJ (1998) Fossil crocodilians as indicators of Late Cretaceous and Cenozoic climates: implications for using palaeontological data in reconstructing palaeoclimate. Palaeogeography, Palaeoclimatology, Palaeoecology 137: 205–271. doi: 10.1016/s0031-0182(97)00108-9
[12]
Thorsteinsson R, Tozer ET (1962) Banks, Victoria, and Stefansson Islands, Arctic Archipelago. Geological Survey of Canada Memoir 330. 83 p.
[13]
Miall AD (1986) The Eureka Sound Group (Upper Cretaceous – Oligocene), Canadian Arctic Islands. Bulletin of Canadian Petroleum Geology 34: 240–270.
[14]
Miall AD (1991) Late Cretaceous and Tertiary basin development and sedimentation, Arctic Islands. In Trettin HP, editor. Geology of the Innuitian Orogen and Arctic Platform of Canada and Greenland: Geological Survey of Canada, Geology of Canada, no. 3; (also Geological Society of America, The Geology of North America, v. E). 437–458.
[15]
Frey RW, Howard JD, Pryor WA (1978) Ophiomorpha: Its morphologic, taxonomic, and environmental significance. Palaeogeography, Palaeoclimatology, Palaeoecology 23: 199–229. doi: 10.1016/0031-0182(78)90094-9
[16]
Hopkins WS (1974) Report on 36 Field Samples from Banks Island, District of Franklin, Northwest Territories, Submitted by A. Miall, 1973 (NTS 88C, F, 98D, E), Geological Survey of Canada, Paleontological Report KT-01-WSH-1974.
[17]
Hopkins WS (1975) Palynology Report on 44 Field Samples from Banks Island, Submitted by A.D. Miall,1974 (NTS 88B,C,F, 97H,98D,E); Geological Survey of Canada, Paleontological Report KT-10-WSH-1975.
[18]
Sweet AR (2012) Applied research report on 5 outcrop samples collected by Andrew Miall from northern Banks Island, NWT (NTS Map Sheets 098E/01, 08, 09): Geological Survey of Canada Paleontological report ARS-2012-01.
[19]
Romer AS (1956) Osteology of the Reptiles. Chicago: University of Chicago Press. 772 p.
[20]
Grande L (2010) An empirical synthetic pattern study of gars (Lepisosteiformes) and closely related species, based mostly on anatomy. American Society of Ichthyologists and Herpetologists Special Publication 6: 1–871.
[21]
Grande L, Bemis W (1998) A comprehensive phylogenetic study of amiid fishes (Amiidae) based on comparative skeletal anatomy. An empirical search for interconnected patterns of natural history. Society of Vertebrate Paleontology Memoir 4: 1–690. doi: 10.2307/3889331
[22]
Patterson RT, Wright C, Chang A, Taylor L, Lyons P, et al. (2002) Atlas of common squamatological (fish scale) material in coastal British Columbia and an assessment of the utility of various scale types in paleofisheries reconstruction. Palaeontologia Electronica 4: 1–88.
[23]
Gerdaux D, Dufour E (2012) Inferring occurrence of growth checks in pike (Esox lucius) scales by using sequential isotopic analysis of otoliths. Rapid Communications in Mass Spectrometry 26: 785–792. doi: 10.1002/rcm.6165
[24]
Brochu CA (1996) Closure of neurocentral sutures during crocodilian ontogeny: Implications for maturity assessment in fossil archosaurs. Journal of Vertebrate Paleontology 16: 49–62. doi: 10.1080/02724634.1996.10011283
[25]
Michard JG, Broin F, Brunet M, Hell J (1990) Le plus ancien crocodilien néosuchien spécialisé à charactéres “eusuchiens” du continent africain (Crétacé inférieur, Cameroun). Comptes Rendus de l’Academie des Sciences de Paris Ser. 2 311: 365–370.
[26]
Brinkmann W (1992) Die Krokodilier-Fauna aus der Unter-Kreide (Ober-Barremium) von Una (Provinz Cuenca, Spanien). Berliner Geowissenschaftliche Abhandlungen E 5: 1–143.
[27]
Rogers JV (2003) Pachycheilosuchus trinquei, a new procoelous crocodyliform from the Lower Cretaceous (Albian) Glen Rose Formation of Texas. Journal of Vertebrate Paleontology 23: 128–145. doi: 10.1671/0272-4634(2003)23[128:ptanpc]2.0.co;2
[28]
Salisbury SW, Frey E, Martill DM, Buchy MC (2003) A new crocodilian from the Lower Cretaceous Crato Formation of north-eastern Brazil. Palaeontographica Abt. A 270: 3–47.
[29]
Pol D, Turner AH, Norell M (2009) Morphology of the Late Cretaceous crocodylomorph Shamosuchus djadochtaensis and a discussion of neosuchian phylogeny as related to the origin of Eusuchia. Bulletin of the American Museum of Natural History 324: 1–103. doi: 10.1206/0003-0090-324.1.1
[30]
Buscalioni AD, Piras P, Vullo R, Signore M, Barbera C (2011) Early Eusuchia Crocodylomorpha from the vertebrate-rich Plattenkalk of Pietraroia (Lower Albian, southern Appenines, Italy). Zoological Journal of the Linnean Society 163: S199–S227. doi: 10.1111/j.1096-3642.2011.00718.x
[31]
Salisbury SW, Frey E (2001) A biomechanical transformation model for the evolution of semi-spheroidal articulations between adjoining vertebral bodies in crocodilians. In: Grigg GC, Seebacher F, Franklin CE, editors. Crocodilian Biology and Evolution. Chipping Norton: Surrey Beatty and Sons. 85–134.
[32]
Brisbin IL, Standora EA, Vargo MJ (1982) Body, temperatures and behavior of American alligators during cold winter weather. American Midland Naturalist 107: 209–218. doi: 10.2307/2425371
[33]
Thorbjarnarson J, Wang X (2010) The Chinese Alligator: Ecology, Behavior, Conservation, and Culture. Baltimore: Johns Hopkins University Press.
[34]
Eberle JJ, Fricke HC, Humphrey JD, Hackett L, Newbrey MG, et al. (2010) Seasonal variability in Arctic temperatures during early Eocene time: Earth and Planetary Science Letters. 296: 481–486. doi: 10.1016/j.epsl.2010.06.005
[35]
Greenwood DR, Basinger JF, Smith RY (2010) How wet was the Arctic Eocene rainforest? Estimates of precipitation from Paleogene Arctic macrofloras. Geology 38: 15–18 doi: 10.1130/G30218.1.
[36]
Weijers JWH, Schouten S, Sluijs A, Brinkhuis H, Sinninghe Damste JH (2007) Warm Arctic continents during the Paleocene-Eocene thermal maximum. Earth and Planetary Science Letters 261: 230–238. doi: 10.1016/j.epsl.2007.06.033
[37]
Schubert BA, Jahren AH, Eberle JJ, Sternberg LSL, Eberth DA (2012) A summertime rainy season in the Arctic forests of the Eocene. Geology 40: 523–526. doi: 10.1130/g32856.1
[38]
Schubert BA, Jahren AH (2011) Quantifying seasonal precipitation using high-resolution carbon isotope analyses in evergreen wood. Geochimica et Cosmochimica Acta 75: 7291–7303. doi: 10.1016/j.gca.2011.08.002
[39]
Nilsson J, Engstedt O, Larsson P (2013) Wetlands for northern pike (Esox lucius L.) recruitment in the Baltic Sea. Hydrobiologia 721: 145–154. doi: 10.1007/s10750-013-1656-9
[40]
Lehman J-P (1951) Un novel amiid de l’Eocène du Spitzberg. Pseudamia heintzi. Arshefter Troms？ Museums 70(1947): 1–11.
[41]
Ohta YA, Hjelle A, Andresen A, Dallman WK, Salvigsen S (1992) Geological map of Svalbard 1: 100,000. Sheet B9G Isfjorden. Norsk Polarinstitutt. Temakart 16, Oslo.
[42]
Scott WB, Crossman EJ (1973) Freshwater fishes of Canada. Bulletin Fisheries Research Board of Canada 184: 1–96. doi: 10.1002/iroh.19760610109
[43]
Taplin LE, Grigg GC (1989) Historical zoogeography of the eusuchian crocodilians: a physiological perspective. American Zoologist 29: 885–901. doi: 10.1093/icb/29.3.885
[44]
Xu Q, Huang C (1984) Some problems in evolution and distribution of Alligator. Vertebrata PalAsiatica 22: 49–53.
[45]
Brochu CA (1999) Phylogeny, systematics, and historical biogeography of Alligatoroidea. Society of Vertebrate Paleontology Memoir 6: 9–100. doi: 10.2307/3889340
[46]
Snyder D (2007) Morphology and systematics of two Miocene alligators from Florida, with a discussion of Alligator biogeography. Journal of Paleontology 81: 917–928. doi: 10.1666/pleo05-104.1
[47]
Brochu CA (2004) Alligatorine phylogeny and the status of Allognathosuchus Mook, 1921. Journal of Vertebrate Paleontology 24: 856–872. doi: 10.1671/0272-4634(2004)024[0857:apatso]2.0.co;2
[48]
Wu X, Wang Y, Zhou K, Zhu W, Nie J, et al. (2003) Complete mitochondrial DNA sequence of Chinese alligator, Alligator sinensis, and phylogeny of crocodiles. Chinese Science Bulletin 48: 2050–2054. doi: 10.1360/03wc0076
[49]
Roos JR, Aggarwal K, Janke A (2007) Extended mitogenomic phylogenetic analyses yield new insight into crocodylian evolution and their survival of the Cretaceous-Tertiary boundary. Molecular Phylogenetics and Evolution 45: 663–673. doi: 10.1016/j.ympev.2007.06.018
[50]
Oaks JR (2011) A time-calibrated species tree of Crocodylia reveals a recent radiation of the true crocodiles. Evolution 65: 3285–3297. doi: 10.1111/j.1558-5646.2011.01373.x
[51]
Martin J, Lauprasert K (2010) A new primitive alligatorine from the Eocene of Thailand: relevance of Asiatic members to the radiation of the group. Zoological Journal of the Linnean Society 158: 608–628. doi: 10.1111/j.1096-3642.2009.00582.x
