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Mammals from the Palaeogene of the EurekaSound Formation: Ellesmere Island, Arctic Canada
MAMMALS FROM THE PALAEOGENE OF THE EUREKA SOUND FORMATION ELLESMERE ISLAND, ARCTIC CANADA by ROBERT M. W E S T * and MARY R. D A W S O N *"
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ABSTRACT
La formation Eureka Sound dans File Ellesmere, situ4e dans la zone arctique canadienne ~ approximativement 79 ° de latitude Nor& a livr4 diverses faunes de mammif~res qui ont un cachet Eocene infErieur/: Eocene moyen. LIn premier examen du mat4riel a montr4 la presence de plusieurs ordres :
The Eureka Sound Formation on Ellesmere Island., Canadian High Arctic at about 79 ° north latitude, has yielded mammalian assemblages of early to middle Eocene aspect. Preliminary examination has shown t~he presence of the orders Pro.t.
PvOteutheria, D ermoptera, Rodentia, t~antodonta, carnivores et Perissodactyla. Associ4s a c e s mammif4res on a un ensemble de vert4brEs infErieurs comprenant de nombreux restes de poissons, sa]amandres, alligators, 1Ezards, serpents et diffErentes sortes de tortues et d'oiseaux. Ces ensembles constituent la premiere preuve pal4ontologique de la pr4sence de faunes terres~ Ires au PalEog4ne sous des latitudes 41ev4es dans la r4gion holarctique; eliles posent de nouveaux problames ~ propos de la palEobiogEographie environnements de la zone arctique pendant l'Eoc~ne.
eutheria, Dermoptera, Primates, Ro,denti& Pantodonta, carnivores, an'd Perissodactyia. Associated with these mammals are a variety of Iower vertebrates, incIuding numerous fish. salamander, alligator, several kinds of turtle, lizard, snake, and several kinds of birds. The assemblages provide the first paleontological evidence of high latitude Paleogene terrestrial faunas in the Holarctic, and raise new questions about Arctic environment during the Eocene.
MOTS-CLI~S : FALINEVERTI~BR]~S, I~OC]~NE, BIOGEOGRAPHIE, FRANKLIN ILES ARCTIQIAESCANADA(ELLESMERE ISLAND). KEY WORDS: VERTEBRATE FAUNA, EOCENE, BIOGEOGRAPHY, FRANKLIN ARCTIC ISLANDS (ELLESMERE ISLAND).
* Department of Geology, Milwaukee PubIic Museum, Milwaukee, Wisconsin 53.233, U.S A. '~* Section of Vertebrate Fossils, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania 15213, U.S.A.
G4obios, MEm. special 1
p. 107-1'24, 8 fig., 1 ta'bl.
Lyon, septembre 1977
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CONTENTS Introduction : North Atlantic faunal exchange Previous studies . . . . . . . . . . . . . . . . . . . . . . . . Current programs . . . . . . . . . . . . . . . . . . . . . . The Eureka Sound Formation . . . . . . . . . .
108 10,9 109 115
Eureka Sound Formation vertebrates . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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INTRODUCTION : NORTH ATLANTIC FAUNAL EXCHANGE It has long been recognized that North American and European early Eocene (Sparnacian/ Wasatchian, approximately 50 million years ago) mammalian faunas show a high degree of similarity at the generic level (Simpson, 1947; Russell, 196,8; Hartenberger, 1970; Savage, 1971). The traditional stabilist explanation of this similarity has been to invoke a trans-Eurasian distribution, with North America at the eastern end and Europe at the western end (Matthew, 1'915 and 1939; Simpson, 1947). However, neither of these authors denied the possibility of a North Atlantic early Eocene connection; they merely regarded the evidence for such a connection to be quite inadequate, and their basic stabilist ,philosophies made a Bering connection much more attractive. Ongoing studies of sea-floor spreading and resultant continental movements now provide a physical framework for re-evaluating the *likelihood of a continuous land connection across the protoNorth Atlantic until about 47 million years ago. Calculations of the actual time of greatest faunal similarity using radiometric techniques place it at about 50 million years ago, with the abrupt decrease in similarity (or increase in endemism) occurring a few mill.ion years later. This corresponds nicely to the postulated final severing of the land connection about 47 million years ago. There are two proposed actual position,s of the last points of terrestrial communication between Europe and North America (fig. 1). The DeGeer route o:f M. McKenna (1971, 19'72) extends from northern Greenland to the European mainland via Spitsbergen and the shallow Barents Shelf. The Thulean route (Gregory, 1929 ; Kurten, 196,6) includes Paleogene proto-Iceland and the Faeroes
as stepping stones on the way to Britain and the mainland. Both of these share a common western en'd from Greenland to the North American main~ land via the northeastern Canadian Arctic Islands, the largest one of which, Ellesmere, is immediately adjacent to the northwestern part of Greenland. This western part of the latest early Tertiary exchange area can be no farther south, as the floor of Baffin Bay is Mesozoic in age. W h e n drawn on a map of the modern North Atlantic, the eastern ends of the probable exchange area include large amounts of open ocean with oceanic crust beneath. This is because of the location of the Cenozoic sea-floor spreading center along the mid-Atlantic Ridge which extends between Greenland and Europe. If we transpose these routes onto an early Tertiary, pro-drift map (fig. 2), the proximity of Greenland to Europe via either route becomes far more apparent and the logic behind the intercontinental connection more clear. No significant change in the relationship of the Canadian Arctic and Greenland has occurred in the Cenozoic. If we now consider the three branches of this Y-shaped exchange area, we find that only two of them have obvious geologic potential for paleontologic confirmation of the presence and nature o[ Paleogene North Atlantic area vertebrate faunas. Rocks of modern Iceland are simply not old enough to contain fossils of early or middle Eocene age; Paleogene proto-tceland has been cycled into a submarine position as the North Atlantic developed through the Neogene. East Greenland has thick Paleogene deposits, but they are largely marine or igneous (Soper et al., 1976). This region has modest pal;eontologic promise as well-preserved
--- 109 - vertebrates have been collected from welded tufts and other igneous rocks at various places elsewhere in the world. However, plant and invertebrate-bearing Tertiary rocks do occur in East Greenland and the contents have been studied (for example, see Hasan, 1953), but no fossil bones have been found. Thus, the northwestern end of the Thulean route is potentially confirmable, but the discovery of Paleogene fossils on or near Iceland is improbable. The DeGeer route includes emergent Paleogene
terrestrial sedimentary rocks on Spitsbergen (Lehmann, 1973 ; Livsic, 1974). These welt&nown coal measures contain a temperate flora in lithofacies which are similar to those of fossiliferous rocks eIsewhere in the world. The common western end of the North Atlantic exchange area incorporates the extensive coalbearing rocks of the Eureka Sound Formation, which also yields abundant temperate-cl:imate plant fossils (Fortier et at., 1963).
PREVIOUS STUDIES Searches for Paleogene mammals in high-latitude areas were first conducted by ].A. Dorr Jr., in northwestern Canada and Alaska south of the Brooks Range in the early 1960's (Dorr, 1963). This work was intended to shed some light on Tertiary mammals in the Bering Strait region in the context of W . D . Matthew's and G . G . Simpson's work. Despite the availability of suitable exposures and facies, Dorr was unsuccessful in his search for pre-Pleistocene non-marine vertebrate fossils. D. Russell in 1969 (Lehman, 1970) and LI. Lehmann in 1972 (Lehmann, 1973) and 1975 searched the Tertiary of Spitsbergen with no success in finding terrestrial fossil vertebrates. The presence of an amiid fish, Pseudamia (LEHMAN, 1951 ), found and presented to the Tromso Museum in 1910, indicated the presence of fresh-water deposits on Spitsbergen, but neither D. Russell nor LI. Lehmann was able to demonstrate the presence of higher vertebrates. Like J.A. Doff, they did
encounter abundant temperate-climate plant fossils from the coat-bearing sequences. This negative evidence in no way proves the absence of terrestrial vertebrates from Paleogene Spitsbergen, but their nature remains quite uniknown. Thus, both proposed eastern areas of EuropeanNorth American exchange across the North Atlantic are unconfirmed, and only the DeGeer route appears to have reasonable potential for confirmation. For purely geologic reasons, the Thulean route seems to have more promise as a direct western E u r o p e - N o r t h American route, as early and middle Eocene Scandinavia apparently was a geographic cul-de-sac cut off from the major part of Europe by a greatly expanded BaItic Sea (Ziegler, 1975) which connected directly with the Obik Sea and Turgai Strait of central Russia. These Asian epicontinental seas also provide a barrier to Paleogene distribution via the Bering Strait region.
C U R R E N T PROGRAMS The geology of the other promising region for recovery of Tertiary vertebrates, the northeastern Canadian Arctic (fig. 3), is under intensive study by the Geological Survey of Canada. Most of this area is occupied by the Sverdrup Basin, a vast ,downwarp which collected sediment virtually continuously from Pennsylvanian to early Tertiary, and which was subjected to several episodes of folding, faulting and diapiric intrusion. The oil and gas potential of t'his com,plex area is the obvious stim-
ul'us for the Geological Survey of Canada work. A general result has been the publication o{ a series of geologic maps covering much of Ellesmere Island. The appearance of these maps with their demonstration of the vast amount of Eureka Sound Formation exposures, led the current authors to initiate paleontologic work on Ellesmere Island in 1973. The initial field season was under the auspices of the Carnegie Museum, Adelphi University (New
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Fig. 2 - Paleogene North Atlantic, prior to the opening of the Atlantic Ocean into the Artic Basin. The Thule, DeGeer and Ellesmere areas of possible faunal interchange are indicated by the same patterns as in fig. 1. Adapted from Lowell, 1972. La r~gion Nord Atlantique au Pal6og6ne, avant la communication de FOc~an Atlantique avec Je bassin arctique. Les zones de Thul6. Degeer et Ellesmere d'6change faunique possible sont indiqu6es par les m6mes figur6s que dans la fig. 1. Adapt6 d'apr6s Lowell, 1972.
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Fig. 5 - The Strathcona Fiord region of west-central Ellesmere Island. Patterned areas are occupied by pre-Eureka Sound Formation rocks. Fossiliferous regions are indicated by the large dots. La region du fjord Strathcona dans la partie centre-ouest de ile Eilesmere. La zone hachur6e indique les affleurements des s6diments pr6-Eureka Sound Formation. Les r6gions fossilif~res sont marqu6es par les points.
- - 115 - York) and the Royal Ontario Museum (Toronto), with financial support from the National Geographic Society and logistics support from the Polar Continental Shelf Project of the Canadian Department of Energy, Mines and Resources. The field group included R . M . W e s t and M . R . Dawson, the co-principal investigators, and J. Howard Hutchison (University of California, Berkeley) and Paul Ramaekers (Royal Ontario Museum) as fieid assistants. The 1975 field season was co-sponsored by Carnegie Museum and the Milwau;kee Public Museum; logistical support again came from the Polar Continental Shelf Project and a small financial contribution was made by the Arctic Institute of North America. W e s t and Dawson constituted the field party. Carnegie Museum and the Milwaukee Public Museum again co-sponsored the 1976 work, with support from the National Geographic Society and the Polar Continental Shelf Project. R . M . W e s t and M . R . Dawson again coordinated the work, with J . H . Hutchison and Malcolm C. McKenna (American Museum of Natural History, N e w York) assisting. The results of the 1973 and 1975 seasons have already been published (Dawson e,~ al., 1975, 1976 ;
W e s t et al., 1975). No terrestriai vertebrate fossils were recovered from the Eureka Soun*d Formation in 1973; the primary tangible resuIt was the delineation of major marine sequences within the Eureka Sound Formation, indicated by marine invertebrates and calcareous otoliths of marine teleost fishes. A less tangible result was the observation of the nature of Eureka Sound Formation exposures and facies. This was encouraging enough to maintain interest in additional work. In 1975 a small but diverse vertebrate fauna was collected, with turtles and al,ligators the dominant elements. Three taxa of mammals w'ere recovered, but each was represented by fragmentary material. Tentative identifications were made of two forms; one seemed similar to the Sparnacian equid Propachy, nolophus 9audryi as well as to the late Wasatchian titanothere Lambdotherium popoagicum, while the other appeared similar to the Cuisian paleothere
Playio[oph~s cartieri. During the 1976 season a substantial vertebrate fauna was collected. It includes several hundred specimens, about t00 of which are mammalian. In contrast with the 19'75 collection, the quality of the specimens is good, so many identifications can be made with confidence. Preliiminary work suggests that at least 3'0 tetrapod species are present, about ! 8 of which are mammalian.
THE EUREKA S O U N D FORMATION The Eureka Sound Formation is a weli deve!oped, sedimentary unit, over 30~00 m (10000 ft) thick in its typical area on Fosheim Peninsula, west-central Ellesmere Island (Fortier et al., 1963). Both marine and continental deposits are present. In fact, there is enough distinction between these two primary Iithofacies to suggest that they might well be mappable as separate formations. If that is the case, the Eureka Sound should be raised to Group rank. The continental rocks are dominantly dark carbonaceous mudstones, fine to medium-wained lightcolored quartzose sandstones, low-grade coal beds up to eight meters thick, and occasional resistant calcareous units. The marine sediments are generally marls, silty limestones and calcareous shale siltstone and sandstone, readily distinguished from the continental rocks by their greater resistance to weathering and more reg,ala:r bedding.
Because of the absence of abun'dant vegetation and the erosive activities of surface water under Arctic conditions, the Eureka Sound Formation is well exposed in many places (fig. 4). As it is a relatively nonresistant unit, exposures are usually gently sloped and thus readily accessible. Exposure areas of the Eureka Sound Formation on Ellesmere Island are usually in north-south trending structural valleys. The bounding rocks are generally Paleozoic marine units which have been thrust up over the Eureka Sound Forma;:ion during the late Paleogene or early Neogene Eurekan Orogeny. One of the effects of this recent orogenic activity is to make correlation within the Eureka Sound Formation exceedingly difficult. It is vi> tually impossible to relate a locality in one valley to a locality in an adjacent valley. Perhaps depositional cycles exist which are consistent throughout the exposure area of the Eureka Sound For-
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mation. However, the basic physical stratigraphic work which could provide such correlation clues simply has not been completed. The Geological Survey of Canada is initiating a major stratigraphic study of the Eureka Sound Formation, but it will be several, years be'fore any results will be available. In the meantime, paleontologic work will be largely independent.
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The generalized stratigraphy of the Strathcona region includes approximately 2 5,0,0 to 3 000 meters of section. Three lithofacies dominate the exposure pattern, and each has yielded its own suite of fossil organisms. Because of the local structural complexities, the superpositional relationships of these are poorly understood and there is an unknown amount of repetition within the section. A thick (600 meters)
Fig. 6 - "Otolith Hills" the region south of Strathcona Fiord where otoliths of marine fishes were found. "Otolith Hills", la r6gion au Sud du fjord Strathcona oh des otolithes de poissons marins ont 6t6 trouv6s.
Thus far, all the vertebrate localities are in the vicinity of Bay and Strathcona Fiords, central Ellesmere Island, centered on about 78 ° 45' north latitude and 82 ° 30' east longitude (fig. 5). All apparently are in the same structural valley. Although the several fiords disrupt exposure conti~ nuity, careful study of aerial photographs and surface examination on the various peninsulas sug~ gest a basic structural and stratigraphic similarity through the productive region.
reddish-brown mudstone unit containing abundant fossil plants is situated relatively low in the local section. The initial finds of turtles, alligatorines and fragmentary mammals were made in this facies in 1975 in the region of Strathcona Fiord (fig. 6). Apparently underlying it is a very thick <> unit, 1 000 to 1 25,0 meters o,f flaggy gray san dsto~ nes and stiltstones and thin-bedded limestones and marls (fig. 7). This unit is with the primary producer of marine fossils (otoliths, molluscs, shark teeth,
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foraminifers and scaphopods) south of Strathcona Fiord. The presumed uppermost fossiliferous uiit of the local Eureka Sound Formation section in the Strathcona region is about 70'0 meters of alter~ nating buff~brown sandstones, siltstones and coals,
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with prominent sideritic surface debris on much o} the sandstone and siltstone, and minor limestones and marls. This part of the section contains the better vertebrate localities, and all of them that seem to be primarily terrestrial (fig. 8).
EUREKA S O U N D FORMATION VERTEBRATES Fossil vertebrates have been collected from over 120 localities in several lithofacies within the Eureka Sound Formation, each apparently repre~ senting a distinct depositionaI environment. Marine siltstones and fine-grained sandstones have pro~ duced teleost otoliths (locally abundant) {West et al., 1975) and, at one locality, shark teeth of the genus Odentaspis. There are strong suggestions from both the foraminiferans and the fish that at least part of this facies was deposited in deep, open-water conditions. The initial tetrapod discoveries of 1975 (Dawson et al., 1976) were in gray to brown si}stones and fissile shales. Although some mammals were found, as mentioned above the fauna from this lithofacies is dominated by aquatic turtles and alligatorines. Various fishes are also present, including Lepisos~ teu~ and Amia as well as teleosts. This facies probably represents swampy of lagoonal conditions with relatively little water movement. The pre~ sence of presumed freshwater fish suggest a conti~ nentat or marginal location, with the water either fresh or brackish. Mammals are common, indeed dominant, in two assemblages, both recognized in 1976. Both occur in fine to medium-grained light quartzose sandstone channel deposits cut into light-colored siltstones, the surfaces o'f which are littered with sideritic concretions and debris. This is part of a thick continental coal-bearing sequence ; a reasonably detailed section over 400 meters (1200 feet) thick was measured and the top of the productive part of the sequence was not reached. One assemblage includes mammals associated with abundant remains of turtles, while in the other the mammalian fossils are associated with fossil seeds of Cercidiphyllum. These two occurrences are essentially identical geologically, and are definitely continental in situation. In addition to fossil mammals and turtles, these two assemblages contain infrequent remains of salamanders, snakes, lizards, alligatorines and birds.
The mammalian fauna is listed in Table t, which also indicates the approximate frequency of occur~ rence. Three kinds of mammals dominate : dermop~ terans (Plagiomenidae ) , pantedonts (Coryphodon ) , and tapiroids (Hyrachyus). Brief comments of a preliminary nature follo,w for each of the recog~ nized mammalian taxa. PROTEUTHERIA : The Leptictidae are represented by a single lower molar which seems similar to the well-known Wasatchian Palaeictops. The Pantolestictae are represented by a complete lower molar, a partial upper motar, and postcranial fragments including a well-preserved humerus. These specimens are readily referable to Pantoles~es cf. natans, an early Bridgerian species illustrated and discussed by W . D. Matthew in 19'09. DEMOPTERA : Several species of Plagiomenidae are present, and this genus is a prominent part of the assemblage. The species are separable both on the basis of size and of rather prominent differences in dental characteristics. In addition to the various species represented by dental material, several edentuous dentaries may also be dermopteran. If so, at 1east one additional species is present, as one of the edentulous jaws is only about 6;0 % the size of the next smaller one. Arctic Plagiom,enidae diversity far exceeds that farther south, as K. D. Rose (I973) recognized only one species in the early 'Wasatchian of Wyoming. PRIMATES : T w o species of the paramomyid Phenacolemur are present. The smaller is virtually identical to P. praecox of the early ~Vasatchian (see Simpson, 1955). The other specimen is of vastly larger individual, quite obviously a new species. The genus Phenacolemur is one component of the Eureka
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Sound assemblages which is present on both sides of the Atlantic Ocean, although the Arctic material is much more similar to North American species. RODENTIA :
One common family of early and middle Eocene rodents is present in the Eureka Sound Formation, though at this point is not as diverse and abundant as in localities farther south. They are represented by ,distressingly incomplete material. Lower jaws of Ischyromyida¢ were recovered but in each instance the entire cheek tooth row is broken off. Three ischyromyid cheek teeth have been found m the washed concentrate; these belong to at least two species. In addition, several isolated incisor fragments are in the 19.76 collection, but their likely affinities have not yet been determined. Ischyromyids are well known from both Europe and North America. TAENIODONTA :
A single fragment o,f enamel is readily assignable to the Stylinodonticlae, although it is not possible to determine whether it should be placed in Ecto9anus or Stylino,don. It is part of an anterior tooth (incisor or canine) in which the enamel covering is incofplete; fortunately the enamel margin is present in our specimen. Further substantiation of this ordinal assignment is provided by the typical enamel rugo,sity. Taeniodonts are North American and South Asian and are elements of most Paleogene assemblages through the Bridgerian. PANTODONTA :
Another of the three most common genera is
Coryphodon, the large herbivore present throughout the Wasatchian of North America, the Sparnacian of Europe and the early Eocene of Asia. Arctic Co rgphodon is represented by isolated teeth, a dentary fragment with P~-M1 and two partial skulls, both preserved mainly as siderite-filled sinuses. The species of coryphodonts are in a markedly confused state (Simons, 1960, p. 13), so no specific designation is possible. CARNIVORANS :
Three dentary fragments are apparently of carnivorous mammals, but the specimens are so incomplete and badly preserved that we cannot even determine whether they are true Carnivora, Creodonta or carnivorous Co ndylarthra. Far better material is necessary before any precise evaluation of this part of the assemblage can be undertaken.
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PERISSODACTYLA :
The third common genus in the Eureka Sound Formation assemblage is the tapiroid Hyrachyus. it is represented by excellent material from numerous localities. N M C 3.0.8'04 is a skull fragment containing the entire post-canine dentition; other specimens demonstrate the nature of almost all of the lower post-canine teeth. Dentally there are no consequential differences between the Eureka Sound animal and H!trach~tus modes;tus of the Bridget Formation of W y o m i n g ; the Arctic animal is about 10 % smaller than the mean size of early Bridgerian specimens and almost the same size as the mean of later Bridgerian H. modestus (Radinsky, 1967). There is a slight incongruity in that the upper posterior premolars are relatively primitive and nonmolariform (virtuallv no development of the hypocone), while the lower posterior premolars of what is presumably the same species of Hyrachyus are relatively advanced with squared talonids possessing prominent entoconids. Also, the infraorbital foramen of Hyrachyus from Wyoming is directly above the third premolar (Wood, 193,4), while in the Arctic form it is situated above the first molar. In addition to this common species of Hyrachyus, a sing~l'e lower premolar probably represents a second, much smaller species. In the absence of more complete dentitions, however, it is almost impossible to tell whether this tooth belongs to Hyrachyus or to a species of Hela,letinae (used in the sense of Radinsky, 1967). Hyrachyus is present in the late Wasatchian and Bridgerian of North America and the Sparnacian and Lutetian of Europe. Several specimens of upper molars are morphologically close to the small Wasatchian brontothere Lambdo,therium, though there are also similarities with European Eocene palaeotheres. The specimens collected in 1975 and tentatively referred to Pla9iolophus and Pro,pachyno,lophus or Lambdotherium (Dawson et al., 197,6,) now seem referable to this North American genus. A single lower third premolar is questionably referred to Hyracotherium, the Wasatchian/Sparnacian equid of both continents. Tile enamel of this tooth is badly corroded, producing considerable uncertainty in the identification. In most respects, the mammalian fauna of the Eureka Sound Formation seems temporally and compositionally closest to that of the Wasatchian of North America. Of the genera than can be identified with reasonable certainty, only Panto-
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testes is not now known from the Wasatchian. Several taxa have Bridgerian as well as Wasatchian records, but the affinities do seem to more strongly suggest a Wasatchian age. The localities range through at least 70:0 meters of section, so it is also possible that a biologically significant amount of time elapsed between lower and upper localities. The Eureka Sound assemblage, while having this general strong Wasatchian affinity, does not correspond with any of the known local faunas of the Wasatchian-early (Gray BulI), middle (Lysite), or late {Lost Cabin). Plagiomenidae is present only in the early Wasatchian (Gray Bull fauna) (Rose, 1973), whereas Lambdotherium is exclusively later Wasatchian (Lost Cabin and possib!y Lysite) and Hyrachyus appears initially in the late Wasatchian and is not common until the Bridgerian. Palaeictops, Phenacolemur, Coryphodon, and Hyracotherium occur throughout the VVasatchian. So, not surprisingly, the assemblage from the Eureka Sound Formation does not exactly correspond to any known southern assemblage. Although all the taxa tentatively or confidently identified have North American affinities, half (Phenacotemur, ischyromyid rodents, Coryphodon, Hyrachyus, and cf. Hyracotherium) occur also in Europe. The lfkely Wasatchian age for at least the butk of the Eureka Sound Formation mammalian fauna places it at a point in time slightly after the proposed termination of fauna continuity between Europe and North America. The diversity of the fauna and the taxonomic similarity to southern faunas suggests markedly similar climatic conditions across much of the Paleogene Northern
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Hemisphere. Such similarity necessitates reexamination of the paleoclimatic history of the far North. The absences from the current Eureka Sound Formation fauna are interesting, though with the relatively small sample size, many of them are not particularly significant at this time. Perhaps the most surprising absence, especially with the close North American relationship, is Hyopsodus. This small condylarth is a prominent part of virtually all Wasatchian and Bridgerian faunas in the American West, and is physically large enough to be readily collected during surface prospecting. Of somewhat less consequence is the absence of primate diversity, especially in the northarctid/ adapidadapid/omomyid area. Fairly small physical size could be a factor here. No marsupials, phena~ codont condylarths or artiodactyls have been found. Marsupials of the family DMelphidae are very small and could easily have been overlooked. Phenacodus and Ectocion are uncommon in the later Wasatchian, as the Phenacoclontidae were rapidly decreasing in relative abundance (West, 1976,), so the absence is not stri:king. Artiodaceyls are relatively uncommon in ~he late W'asatc,hian and Bridgerian, so once again the absence is not particularly important. Rodent and insectivore diversity in the Eureka Sound Formation fauna is very low, but the sinai1 expected physical size allows specimens to be easily overlooked. Approximately one hundred kilos of washed concentrate were shipped south. This material was collected from several of the more productive surface local~ities. Initial results from the picking in,dicare that the fauna will be further expanded, and some absences eliminated,
CONCLUSIONS 1. A Paleogene continental vertebrate fauna of considerable diversity occupied the northeastern corner of North America. This assemblage contains at least thirty species of tetrapods. 2. The vertebrate fossils collected from the Eureka Sound Formation on Ellesmere Island were found in lithologies similar to those of fossiliferous rocks far to the south. The most productive facies are fine and medium-grained channel sandstones,
while bones are also found in finer-grained continental and marine sediments. These represent both continental and marginal aquatic environments. 3. The composition of the Eureka Sound Formation mammalian assemblage most closely resem~ bles that of the North American Wasatchian. However, the assemblage does not exactly correspond with any produced from the presently recognized subdivisions of the Wasatchian.
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4. A p p r o x i m a t e l y 50 % of the reasonably confidently identified genera in the E u r e k a Sound Formation are held in common in N o r t h America and E u r o p e ; the other 50 % are unique to N o r t h America or are present also in Asia. 5. T h e composition of the assemblage suggests that it dates from a short time after the termination of physical continuity between E u r o p e and N o r t h America. 6. Evidence thus far obtained from the E u r e k a Sound Formation does not contribute either to placing a biochronologic date on the separation of N o r t h America a n d Europe, or to verifying a specific eastern exchange area. 7. T h e occurrence and a b u n d a n c e of fossil vertebrates in the E u r e k a Sound Formation in the B a y / S t r a t h c o n a Fiord area of Ellesmere Island, along with the extensive unprospected exposures of that formation, suggest the strong likelihood that future field w o r k will increase the diversity and geographic a n d stratigraphic distribution of the fauna.
122 - Frequency Order Proteutheria
Family Leptictidae el. Palaeictops sp. Family Pantolestidae
R
Pantolestes of. natans Order Dermoptera Family Plagiomenidae
M
Plagiomenid sp. 1 Plagiomenid sp. 2 Plagiomenid sp. 3
C C
M
Order Primates
Family Paromomyidae Phenacolemur small sp. Phenacolemur large sp.
R R
Order R odentia Family Ischyromyidae ischyromyid sp. 1 ischyromyid sp. 2
R R
Order Taenidonta
Family Stylinodontidae of. Stylinodon sp. ACKNOWLEDGEMENTS We are grateful for the financial support of the National Geographic Society in 1973 and 1976 and the Arctic Institute of North America in 1975. The Polar Continental Shelf Project provided logistics support all three seasons; George Hohson, Fred Alt and Frank Hunt of that or0anization have been most helpful and understanding. Dr. Ray Thorsteinsson and the Geological Survey of Canada Arctic research group in Calgary have provided useful advice, information and moral support. Malcolm C. McKenna, J. Howard Hutchison, Leonard Krishtalka, Leonard Radinsky, Howard Schorn, and Bruce Welton have provided valuable advice on identifications of the fossils. All the fossil vertebrates collected from the Eureka Sound Formation are catalogued into the collections of the Division of Paleontology, National Museum of Canada, and are indicated by the abbreviation NMC.
R
Order Pantodonta
Family Coryphodontidae Coryphodon sp.
C
Order Carnivora (?)
Creodonta (?) Condylarthra (?) Family undetermined carnivora indet, sp. 1 carnivora indet, sp. 2 carnivora indet, sp. 3
R R R
Order Perissodactyla
Family Brontotheriidae Lambdotherium ef. popoagicum Family Hyrachyidae Hyrachyus large sp. Hyrachyus small sp. Family Equidae cf. Hyracotherium sp. R : 1 only
M : 2-4
M C R R
C : 5 or more
TaN. 1 - Mammalian faunal list Eureka sound formation.
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123 - -
REFERENCES DAWSON M. R. et al. 0974). - - New evidence on the palaeobiology of the Eureka Sound Formation, Arctic Canada. Arctic, Montreal, 28 (2), p.
110-116.
DAWSON M. R. et al. (1975). - - Paleogene terrestrial vertebrates : norternmost occurrence, gl.lesmere Island, Canada. Science, Washington, 192, p. 781-782. DORR J. A. Jr. (1964). ~ Tertiary non-marine vertebrates in Alaska - - the lack thereof. Bull. Am. Assoc. Pet. Geol., Tulsa, 48 (7), p. 1198-1203. FORTmR Y . O . et al. (1963). - - Geology of the north-central part of the Arctic Archipelago, Northwest Territories (Operation Franklin). Mem. Geol. Surv. Canada, Ottawa, 320, p. 1-669. GRECORY J . W . ( 1 9 2 , 9 ) . - The geological history of the Atlantic Ocean. Quart. J. Geol. Soc. London, 85, L X V I I L C X I I . HARTENBERGER J.-L. (1970). - - Los mammif~res d'Egerkingen et l'histoire des faunes de l'Eoc~ne d'Europe. Bull. Soc. G~ol. France, Paris, 7 ° s4r., 12, p. 886-893. HASSAN M . Y . (1953). - - Tertiary faunas from Kap Brewster, East Greenland. Medd. om Gronland, Copenhague, 111 (5), p. 1-Zfl. KUI~TEN B. ( 1 9 6 6 ) . - Holarctic land connexions in the early Tertiary. Comment. Biol. Soc. Sci. Fennica, Helsinki, 29 (5), 5 p. LEHMAN J.-P. (1951). - - LIn nouvel amiide de l'Eoc4ne du Spitzberg, Pseudamia heintzi. Tromso Mus. Arch. Natur. Avd., Tromso, 70 {3), p. 1-11. LEHMAN ].-P. (1970). - - L'exp~dition pal4ontoIogique frangaise de 1969 au Spitzberg. Atomes, Paris, 25 (274), p. 193-198. LEHMANN LI. (1973). ~ Z u r P algogeographie des Nordatlantiks im Tertiar. Mitt. Geol.-Pataont. Inst. Univ. Hamb,u W, 42, p. 57-69. Lwsm I. J. (197~t) • - - paleogene deposits and platform structure of Svalbard. 1Vorsk Polarinstittut Skri~ter, Oslo, n ° 59, p. 1-51. LOWELL ]. D. (1972). - - Spitsbergen Tertiary orogenic belt and the Spitsbergen fracture zone. Geol. Soc. Amer. Bull., Washington, 83, p. 3'0'913'102.
MATTHEW -W. D. (t909'). - - The Carnivora and Insectivora of the Bridger Basin, Middle Eocene. Mem. Amer. Musu Nat. Hist., N e w York, 9, p. 291-567. MATTHEW W . D . (1915). --- Climate and evoiution. Ann. N. I/'. Acad. Sci., N e w York, 24, p. t71-318. MATTHEW W . D . (1939). - - Climate and evoIution. Second edition, revised and enlarged. Spee. Pubt. N. Y. Acad. Sci., New York, 1, p. XIL223. M c K E ~ A M . C . ( 1 9 7 1 ) . - Fossil mamma!s and the Eocene demise of the DeGeer North AtIantic dispersal route. Geol. Soc. Amer. Abstracts with Programs, Washington, 3 (7), p. 644. MCKENNA M. C. (1972). - - W a s Europe connected directly to North America prior to the middle Eocene ? Evo,l. Biol., Amsterdam, 6, p. 179-188. RADINSKY L. B. ( 1 9 6 7 ) . - Hyrachyus, C,hasmotherium, and the early evolution of helaletid tapifolds. Amer. Mus. Nodt., N e w York, 2313, p. 1-23.
ROSE K.D. (1973). - - The mandibular dentition of Plagiom,ene (Dermoptera, Pla~tiomenidae ) . Breviora, Cambridge, 411, p. 1-17. RUSSELL D. (196'8). - - Succession, en Europe, des faunes mammaliennes au d4but du Tertiaire. M4m. Bus. Rech. G4ol. Min., Paris, n ° 58, p. 291-296. S1MONSE. L. (I 96,0).-- The Paleocene Pantodonta. Trans. Amer. Philos. So c, Philadeiphia, n.s., 50 (6), p. 3-99. SZMPSON G . G . (1947). - - Holarctic mammaIian faunas and continental relationships during the Cenozoic. Butl. Geol. Soc. Amer., Wash'ington, 5,8, p. 613-688. SIMPsoN G. G. ( 1 9 ' 5 3 ) . - Evolution and Geography. Co~ndon Lectures, Oregon State Sgst. Higher Educ., p. 1-64. SIMPSON G.G. ( 1 9 5 , 5 ) . - The Phenacolemuridae, new family of early primates. Bull. Amer, Mus. Nat. Hist., N e w York, 105 (5), p. 411-442. SOPER N . J . et al. {i976). - - Late Cretaceous early Tertiary stratigraphy of the Kangerdlugssuag area, east Greenland, and the age of opening of the nort-east AtIantic. ]our. Geo.l. Soc., 1 3 2 , p. 8 5 - 1 0 4 .
- -
WEST R . M . et el. (197't). - - Paleontologic evidence of marine sediments in the Eureka Sound Formation of Ellesmere Island, Arctic Archipelago, N . W . T . Canada. Canad. ]our. Earth Sci., Ottawa, 12 (4), p. 574-579. WEST R . M .
(19'76). - -
The North American
Phenacodontidae (Mammalia, Condglarthra ). Milwaukee Pu~b. Mus. Cont. Biol. Geol., Milwaukee, 6, p. 1-78.
124
- -
WOOD H. E. 2nd (1934). - - Revision of the Hgrachgidae. Bull. Amer. Mus. Nat. Hist., New York, 67 (5), p. 181-29'5. ZIF,GLER P. A. (1975). - - The geological evolution of the North Sea area in the tectonic framework of north western Europe. No rges 9eo,l. undersokelse, n ° 3'16 (in Whiteman A.J. et al., eds., Bull. 29, Petroleum Geology and Geology of the North Sea and the Northeastern Atlantic Continental Margin, Proceedings o[ a Co,n[erence, Univ,ersitg o[ Bergen, December 1973) p. 1-27.
RgsuMg
ABSTRACT
La formation Eureka Sound dans File Ellesmere, situ4e dans la zone arctique canadienne ~ approximativement 79 ° de latitude Nor& a livr4 diverses faunes de mammif~res qui ont un cachet Eocene infErieur/: Eocene moyen. LIn premier examen du mat4riel a montr4 la presence de plusieurs ordres :
The Eureka Sound Formation on Ellesmere Island., Canadian High Arctic at about 79 ° north latitude, has yielded mammalian assemblages of early to middle Eocene aspect. Preliminary examination has shown t~he presence of the orders Pro.t.
PvOteutheria, D ermoptera, Rodentia, t~antodonta, carnivores et Perissodactyla. Associ4s a c e s mammif4res on a un ensemble de vert4brEs infErieurs comprenant de nombreux restes de poissons, sa]amandres, alligators, 1Ezards, serpents et diffErentes sortes de tortues et d'oiseaux. Ces ensembles constituent la premiere preuve pal4ontologique de la pr4sence de faunes terres~ Ires au PalEog4ne sous des latitudes 41ev4es dans la r4gion holarctique; eliles posent de nouveaux problames ~ propos de la palEobiogEographie environnements de la zone arctique pendant l'Eoc~ne.
eutheria, Dermoptera, Primates, Ro,denti& Pantodonta, carnivores, an'd Perissodactyia. Associated with these mammals are a variety of Iower vertebrates, incIuding numerous fish. salamander, alligator, several kinds of turtle, lizard, snake, and several kinds of birds. The assemblages provide the first paleontological evidence of high latitude Paleogene terrestrial faunas in the Holarctic, and raise new questions about Arctic environment during the Eocene.
MOTS-CLI~S : FALINEVERTI~BR]~S, I~OC]~NE, BIOGEOGRAPHIE, FRANKLIN ILES ARCTIQIAESCANADA(ELLESMERE ISLAND). KEY WORDS: VERTEBRATE FAUNA, EOCENE, BIOGEOGRAPHY, FRANKLIN ARCTIC ISLANDS (ELLESMERE ISLAND).
* Department of Geology, Milwaukee PubIic Museum, Milwaukee, Wisconsin 53.233, U.S A. '~* Section of Vertebrate Fossils, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania 15213, U.S.A.
G4obios, MEm. special 1
p. 107-1'24, 8 fig., 1 ta'bl.
Lyon, septembre 1977
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108
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CONTENTS Introduction : North Atlantic faunal exchange Previous studies . . . . . . . . . . . . . . . . . . . . . . . . Current programs . . . . . . . . . . . . . . . . . . . . . . The Eureka Sound Formation . . . . . . . . . .
108 10,9 109 115
Eureka Sound Formation vertebrates . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . .
119 121 123
INTRODUCTION : NORTH ATLANTIC FAUNAL EXCHANGE It has long been recognized that North American and European early Eocene (Sparnacian/ Wasatchian, approximately 50 million years ago) mammalian faunas show a high degree of similarity at the generic level (Simpson, 1947; Russell, 196,8; Hartenberger, 1970; Savage, 1971). The traditional stabilist explanation of this similarity has been to invoke a trans-Eurasian distribution, with North America at the eastern end and Europe at the western end (Matthew, 1'915 and 1939; Simpson, 1947). However, neither of these authors denied the possibility of a North Atlantic early Eocene connection; they merely regarded the evidence for such a connection to be quite inadequate, and their basic stabilist ,philosophies made a Bering connection much more attractive. Ongoing studies of sea-floor spreading and resultant continental movements now provide a physical framework for re-evaluating the *likelihood of a continuous land connection across the protoNorth Atlantic until about 47 million years ago. Calculations of the actual time of greatest faunal similarity using radiometric techniques place it at about 50 million years ago, with the abrupt decrease in similarity (or increase in endemism) occurring a few mill.ion years later. This corresponds nicely to the postulated final severing of the land connection about 47 million years ago. There are two proposed actual position,s of the last points of terrestrial communication between Europe and North America (fig. 1). The DeGeer route o:f M. McKenna (1971, 19'72) extends from northern Greenland to the European mainland via Spitsbergen and the shallow Barents Shelf. The Thulean route (Gregory, 1929 ; Kurten, 196,6) includes Paleogene proto-Iceland and the Faeroes
as stepping stones on the way to Britain and the mainland. Both of these share a common western en'd from Greenland to the North American main~ land via the northeastern Canadian Arctic Islands, the largest one of which, Ellesmere, is immediately adjacent to the northwestern part of Greenland. This western part of the latest early Tertiary exchange area can be no farther south, as the floor of Baffin Bay is Mesozoic in age. W h e n drawn on a map of the modern North Atlantic, the eastern ends of the probable exchange area include large amounts of open ocean with oceanic crust beneath. This is because of the location of the Cenozoic sea-floor spreading center along the mid-Atlantic Ridge which extends between Greenland and Europe. If we transpose these routes onto an early Tertiary, pro-drift map (fig. 2), the proximity of Greenland to Europe via either route becomes far more apparent and the logic behind the intercontinental connection more clear. No significant change in the relationship of the Canadian Arctic and Greenland has occurred in the Cenozoic. If we now consider the three branches of this Y-shaped exchange area, we find that only two of them have obvious geologic potential for paleontologic confirmation of the presence and nature o[ Paleogene North Atlantic area vertebrate faunas. Rocks of modern Iceland are simply not old enough to contain fossils of early or middle Eocene age; Paleogene proto-tceland has been cycled into a submarine position as the North Atlantic developed through the Neogene. East Greenland has thick Paleogene deposits, but they are largely marine or igneous (Soper et al., 1976). This region has modest pal;eontologic promise as well-preserved
--- 109 - vertebrates have been collected from welded tufts and other igneous rocks at various places elsewhere in the world. However, plant and invertebrate-bearing Tertiary rocks do occur in East Greenland and the contents have been studied (for example, see Hasan, 1953), but no fossil bones have been found. Thus, the northwestern end of the Thulean route is potentially confirmable, but the discovery of Paleogene fossils on or near Iceland is improbable. The DeGeer route includes emergent Paleogene
terrestrial sedimentary rocks on Spitsbergen (Lehmann, 1973 ; Livsic, 1974). These welt&nown coal measures contain a temperate flora in lithofacies which are similar to those of fossiliferous rocks eIsewhere in the world. The common western end of the North Atlantic exchange area incorporates the extensive coalbearing rocks of the Eureka Sound Formation, which also yields abundant temperate-cl:imate plant fossils (Fortier et at., 1963).
PREVIOUS STUDIES Searches for Paleogene mammals in high-latitude areas were first conducted by ].A. Dorr Jr., in northwestern Canada and Alaska south of the Brooks Range in the early 1960's (Dorr, 1963). This work was intended to shed some light on Tertiary mammals in the Bering Strait region in the context of W . D . Matthew's and G . G . Simpson's work. Despite the availability of suitable exposures and facies, Dorr was unsuccessful in his search for pre-Pleistocene non-marine vertebrate fossils. D. Russell in 1969 (Lehman, 1970) and LI. Lehmann in 1972 (Lehmann, 1973) and 1975 searched the Tertiary of Spitsbergen with no success in finding terrestrial fossil vertebrates. The presence of an amiid fish, Pseudamia (LEHMAN, 1951 ), found and presented to the Tromso Museum in 1910, indicated the presence of fresh-water deposits on Spitsbergen, but neither D. Russell nor LI. Lehmann was able to demonstrate the presence of higher vertebrates. Like J.A. Doff, they did
encounter abundant temperate-climate plant fossils from the coat-bearing sequences. This negative evidence in no way proves the absence of terrestrial vertebrates from Paleogene Spitsbergen, but their nature remains quite uniknown. Thus, both proposed eastern areas of EuropeanNorth American exchange across the North Atlantic are unconfirmed, and only the DeGeer route appears to have reasonable potential for confirmation. For purely geologic reasons, the Thulean route seems to have more promise as a direct western E u r o p e - N o r t h American route, as early and middle Eocene Scandinavia apparently was a geographic cul-de-sac cut off from the major part of Europe by a greatly expanded BaItic Sea (Ziegler, 1975) which connected directly with the Obik Sea and Turgai Strait of central Russia. These Asian epicontinental seas also provide a barrier to Paleogene distribution via the Bering Strait region.
C U R R E N T PROGRAMS The geology of the other promising region for recovery of Tertiary vertebrates, the northeastern Canadian Arctic (fig. 3), is under intensive study by the Geological Survey of Canada. Most of this area is occupied by the Sverdrup Basin, a vast ,downwarp which collected sediment virtually continuously from Pennsylvanian to early Tertiary, and which was subjected to several episodes of folding, faulting and diapiric intrusion. The oil and gas potential of t'his com,plex area is the obvious stim-
ul'us for the Geological Survey of Canada work. A general result has been the publication o{ a series of geologic maps covering much of Ellesmere Island. The appearance of these maps with their demonstration of the vast amount of Eureka Sound Formation exposures, led the current authors to initiate paleontologic work on Ellesmere Island in 1973. The initial field season was under the auspices of the Carnegie Museum, Adelphi University (New
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Fig. 2 - Paleogene North Atlantic, prior to the opening of the Atlantic Ocean into the Artic Basin. The Thule, DeGeer and Ellesmere areas of possible faunal interchange are indicated by the same patterns as in fig. 1. Adapted from Lowell, 1972. La r~gion Nord Atlantique au Pal6og6ne, avant la communication de FOc~an Atlantique avec Je bassin arctique. Les zones de Thul6. Degeer et Ellesmere d'6change faunique possible sont indiqu6es par les m6mes figur6s que dans la fig. 1. Adapt6 d'apr6s Lowell, 1972.
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Fig. 5 - The Strathcona Fiord region of west-central Ellesmere Island. Patterned areas are occupied by pre-Eureka Sound Formation rocks. Fossiliferous regions are indicated by the large dots. La region du fjord Strathcona dans la partie centre-ouest de ile Eilesmere. La zone hachur6e indique les affleurements des s6diments pr6-Eureka Sound Formation. Les r6gions fossilif~res sont marqu6es par les points.
- - 115 - York) and the Royal Ontario Museum (Toronto), with financial support from the National Geographic Society and logistics support from the Polar Continental Shelf Project of the Canadian Department of Energy, Mines and Resources. The field group included R . M . W e s t and M . R . Dawson, the co-principal investigators, and J. Howard Hutchison (University of California, Berkeley) and Paul Ramaekers (Royal Ontario Museum) as fieid assistants. The 1975 field season was co-sponsored by Carnegie Museum and the Milwau;kee Public Museum; logistical support again came from the Polar Continental Shelf Project and a small financial contribution was made by the Arctic Institute of North America. W e s t and Dawson constituted the field party. Carnegie Museum and the Milwaukee Public Museum again co-sponsored the 1976 work, with support from the National Geographic Society and the Polar Continental Shelf Project. R . M . W e s t and M . R . Dawson again coordinated the work, with J . H . Hutchison and Malcolm C. McKenna (American Museum of Natural History, N e w York) assisting. The results of the 1973 and 1975 seasons have already been published (Dawson e,~ al., 1975, 1976 ;
W e s t et al., 1975). No terrestriai vertebrate fossils were recovered from the Eureka Soun*d Formation in 1973; the primary tangible resuIt was the delineation of major marine sequences within the Eureka Sound Formation, indicated by marine invertebrates and calcareous otoliths of marine teleost fishes. A less tangible result was the observation of the nature of Eureka Sound Formation exposures and facies. This was encouraging enough to maintain interest in additional work. In 1975 a small but diverse vertebrate fauna was collected, with turtles and al,ligators the dominant elements. Three taxa of mammals w'ere recovered, but each was represented by fragmentary material. Tentative identifications were made of two forms; one seemed similar to the Sparnacian equid Propachy, nolophus 9audryi as well as to the late Wasatchian titanothere Lambdotherium popoagicum, while the other appeared similar to the Cuisian paleothere
Playio[oph~s cartieri. During the 1976 season a substantial vertebrate fauna was collected. It includes several hundred specimens, about t00 of which are mammalian. In contrast with the 19'75 collection, the quality of the specimens is good, so many identifications can be made with confidence. Preliiminary work suggests that at least 3'0 tetrapod species are present, about ! 8 of which are mammalian.
THE EUREKA S O U N D FORMATION The Eureka Sound Formation is a weli deve!oped, sedimentary unit, over 30~00 m (10000 ft) thick in its typical area on Fosheim Peninsula, west-central Ellesmere Island (Fortier et al., 1963). Both marine and continental deposits are present. In fact, there is enough distinction between these two primary Iithofacies to suggest that they might well be mappable as separate formations. If that is the case, the Eureka Sound should be raised to Group rank. The continental rocks are dominantly dark carbonaceous mudstones, fine to medium-wained lightcolored quartzose sandstones, low-grade coal beds up to eight meters thick, and occasional resistant calcareous units. The marine sediments are generally marls, silty limestones and calcareous shale siltstone and sandstone, readily distinguished from the continental rocks by their greater resistance to weathering and more reg,ala:r bedding.
Because of the absence of abun'dant vegetation and the erosive activities of surface water under Arctic conditions, the Eureka Sound Formation is well exposed in many places (fig. 4). As it is a relatively nonresistant unit, exposures are usually gently sloped and thus readily accessible. Exposure areas of the Eureka Sound Formation on Ellesmere Island are usually in north-south trending structural valleys. The bounding rocks are generally Paleozoic marine units which have been thrust up over the Eureka Sound Forma;:ion during the late Paleogene or early Neogene Eurekan Orogeny. One of the effects of this recent orogenic activity is to make correlation within the Eureka Sound Formation exceedingly difficult. It is vi> tually impossible to relate a locality in one valley to a locality in an adjacent valley. Perhaps depositional cycles exist which are consistent throughout the exposure area of the Eureka Sound For-
- -
mation. However, the basic physical stratigraphic work which could provide such correlation clues simply has not been completed. The Geological Survey of Canada is initiating a major stratigraphic study of the Eureka Sound Formation, but it will be several, years be'fore any results will be available. In the meantime, paleontologic work will be largely independent.
116
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The generalized stratigraphy of the Strathcona region includes approximately 2 5,0,0 to 3 000 meters of section. Three lithofacies dominate the exposure pattern, and each has yielded its own suite of fossil organisms. Because of the local structural complexities, the superpositional relationships of these are poorly understood and there is an unknown amount of repetition within the section. A thick (600 meters)
Fig. 6 - "Otolith Hills" the region south of Strathcona Fiord where otoliths of marine fishes were found. "Otolith Hills", la r6gion au Sud du fjord Strathcona oh des otolithes de poissons marins ont 6t6 trouv6s.
Thus far, all the vertebrate localities are in the vicinity of Bay and Strathcona Fiords, central Ellesmere Island, centered on about 78 ° 45' north latitude and 82 ° 30' east longitude (fig. 5). All apparently are in the same structural valley. Although the several fiords disrupt exposure conti~ nuity, careful study of aerial photographs and surface examination on the various peninsulas sug~ gest a basic structural and stratigraphic similarity through the productive region.
reddish-brown mudstone unit containing abundant fossil plants is situated relatively low in the local section. The initial finds of turtles, alligatorines and fragmentary mammals were made in this facies in 1975 in the region of Strathcona Fiord (fig. 6). Apparently underlying it is a very thick <
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foraminifers and scaphopods) south of Strathcona Fiord. The presumed uppermost fossiliferous uiit of the local Eureka Sound Formation section in the Strathcona region is about 70'0 meters of alter~ nating buff~brown sandstones, siltstones and coals,
!19--
with prominent sideritic surface debris on much o} the sandstone and siltstone, and minor limestones and marls. This part of the section contains the better vertebrate localities, and all of them that seem to be primarily terrestrial (fig. 8).
EUREKA S O U N D FORMATION VERTEBRATES Fossil vertebrates have been collected from over 120 localities in several lithofacies within the Eureka Sound Formation, each apparently repre~ senting a distinct depositionaI environment. Marine siltstones and fine-grained sandstones have pro~ duced teleost otoliths (locally abundant) {West et al., 1975) and, at one locality, shark teeth of the genus Odentaspis. There are strong suggestions from both the foraminiferans and the fish that at least part of this facies was deposited in deep, open-water conditions. The initial tetrapod discoveries of 1975 (Dawson et al., 1976) were in gray to brown si}stones and fissile shales. Although some mammals were found, as mentioned above the fauna from this lithofacies is dominated by aquatic turtles and alligatorines. Various fishes are also present, including Lepisos~ teu~ and Amia as well as teleosts. This facies probably represents swampy of lagoonal conditions with relatively little water movement. The pre~ sence of presumed freshwater fish suggest a conti~ nentat or marginal location, with the water either fresh or brackish. Mammals are common, indeed dominant, in two assemblages, both recognized in 1976. Both occur in fine to medium-grained light quartzose sandstone channel deposits cut into light-colored siltstones, the surfaces o'f which are littered with sideritic concretions and debris. This is part of a thick continental coal-bearing sequence ; a reasonably detailed section over 400 meters (1200 feet) thick was measured and the top of the productive part of the sequence was not reached. One assemblage includes mammals associated with abundant remains of turtles, while in the other the mammalian fossils are associated with fossil seeds of Cercidiphyllum. These two occurrences are essentially identical geologically, and are definitely continental in situation. In addition to fossil mammals and turtles, these two assemblages contain infrequent remains of salamanders, snakes, lizards, alligatorines and birds.
The mammalian fauna is listed in Table t, which also indicates the approximate frequency of occur~ rence. Three kinds of mammals dominate : dermop~ terans (Plagiomenidae ) , pantedonts (Coryphodon ) , and tapiroids (Hyrachyus). Brief comments of a preliminary nature follo,w for each of the recog~ nized mammalian taxa. PROTEUTHERIA : The Leptictidae are represented by a single lower molar which seems similar to the well-known Wasatchian Palaeictops. The Pantolestictae are represented by a complete lower molar, a partial upper motar, and postcranial fragments including a well-preserved humerus. These specimens are readily referable to Pantoles~es cf. natans, an early Bridgerian species illustrated and discussed by W . D. Matthew in 19'09. DEMOPTERA : Several species of Plagiomenidae are present, and this genus is a prominent part of the assemblage. The species are separable both on the basis of size and of rather prominent differences in dental characteristics. In addition to the various species represented by dental material, several edentuous dentaries may also be dermopteran. If so, at 1east one additional species is present, as one of the edentulous jaws is only about 6;0 % the size of the next smaller one. Arctic Plagiom,enidae diversity far exceeds that farther south, as K. D. Rose (I973) recognized only one species in the early 'Wasatchian of Wyoming. PRIMATES : T w o species of the paramomyid Phenacolemur are present. The smaller is virtually identical to P. praecox of the early ~Vasatchian (see Simpson, 1955). The other specimen is of vastly larger individual, quite obviously a new species. The genus Phenacolemur is one component of the Eureka
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Sound assemblages which is present on both sides of the Atlantic Ocean, although the Arctic material is much more similar to North American species. RODENTIA :
One common family of early and middle Eocene rodents is present in the Eureka Sound Formation, though at this point is not as diverse and abundant as in localities farther south. They are represented by ,distressingly incomplete material. Lower jaws of Ischyromyida¢ were recovered but in each instance the entire cheek tooth row is broken off. Three ischyromyid cheek teeth have been found m the washed concentrate; these belong to at least two species. In addition, several isolated incisor fragments are in the 19.76 collection, but their likely affinities have not yet been determined. Ischyromyids are well known from both Europe and North America. TAENIODONTA :
A single fragment o,f enamel is readily assignable to the Stylinodonticlae, although it is not possible to determine whether it should be placed in Ecto9anus or Stylino,don. It is part of an anterior tooth (incisor or canine) in which the enamel covering is incofplete; fortunately the enamel margin is present in our specimen. Further substantiation of this ordinal assignment is provided by the typical enamel rugo,sity. Taeniodonts are North American and South Asian and are elements of most Paleogene assemblages through the Bridgerian. PANTODONTA :
Another of the three most common genera is
Coryphodon, the large herbivore present throughout the Wasatchian of North America, the Sparnacian of Europe and the early Eocene of Asia. Arctic Co rgphodon is represented by isolated teeth, a dentary fragment with P~-M1 and two partial skulls, both preserved mainly as siderite-filled sinuses. The species of coryphodonts are in a markedly confused state (Simons, 1960, p. 13), so no specific designation is possible. CARNIVORANS :
Three dentary fragments are apparently of carnivorous mammals, but the specimens are so incomplete and badly preserved that we cannot even determine whether they are true Carnivora, Creodonta or carnivorous Co ndylarthra. Far better material is necessary before any precise evaluation of this part of the assemblage can be undertaken.
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PERISSODACTYLA :
The third common genus in the Eureka Sound Formation assemblage is the tapiroid Hyrachyus. it is represented by excellent material from numerous localities. N M C 3.0.8'04 is a skull fragment containing the entire post-canine dentition; other specimens demonstrate the nature of almost all of the lower post-canine teeth. Dentally there are no consequential differences between the Eureka Sound animal and H!trach~tus modes;tus of the Bridget Formation of W y o m i n g ; the Arctic animal is about 10 % smaller than the mean size of early Bridgerian specimens and almost the same size as the mean of later Bridgerian H. modestus (Radinsky, 1967). There is a slight incongruity in that the upper posterior premolars are relatively primitive and nonmolariform (virtuallv no development of the hypocone), while the lower posterior premolars of what is presumably the same species of Hyrachyus are relatively advanced with squared talonids possessing prominent entoconids. Also, the infraorbital foramen of Hyrachyus from Wyoming is directly above the third premolar (Wood, 193,4), while in the Arctic form it is situated above the first molar. In addition to this common species of Hyrachyus, a sing~l'e lower premolar probably represents a second, much smaller species. In the absence of more complete dentitions, however, it is almost impossible to tell whether this tooth belongs to Hyrachyus or to a species of Hela,letinae (used in the sense of Radinsky, 1967). Hyrachyus is present in the late Wasatchian and Bridgerian of North America and the Sparnacian and Lutetian of Europe. Several specimens of upper molars are morphologically close to the small Wasatchian brontothere Lambdo,therium, though there are also similarities with European Eocene palaeotheres. The specimens collected in 1975 and tentatively referred to Pla9iolophus and Pro,pachyno,lophus or Lambdotherium (Dawson et al., 197,6,) now seem referable to this North American genus. A single lower third premolar is questionably referred to Hyracotherium, the Wasatchian/Sparnacian equid of both continents. Tile enamel of this tooth is badly corroded, producing considerable uncertainty in the identification. In most respects, the mammalian fauna of the Eureka Sound Formation seems temporally and compositionally closest to that of the Wasatchian of North America. Of the genera than can be identified with reasonable certainty, only Panto-
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testes is not now known from the Wasatchian. Several taxa have Bridgerian as well as Wasatchian records, but the affinities do seem to more strongly suggest a Wasatchian age. The localities range through at least 70:0 meters of section, so it is also possible that a biologically significant amount of time elapsed between lower and upper localities. The Eureka Sound assemblage, while having this general strong Wasatchian affinity, does not correspond with any of the known local faunas of the Wasatchian-early (Gray BulI), middle (Lysite), or late {Lost Cabin). Plagiomenidae is present only in the early Wasatchian (Gray Bull fauna) (Rose, 1973), whereas Lambdotherium is exclusively later Wasatchian (Lost Cabin and possib!y Lysite) and Hyrachyus appears initially in the late Wasatchian and is not common until the Bridgerian. Palaeictops, Phenacolemur, Coryphodon, and Hyracotherium occur throughout the VVasatchian. So, not surprisingly, the assemblage from the Eureka Sound Formation does not exactly correspond to any known southern assemblage. Although all the taxa tentatively or confidently identified have North American affinities, half (Phenacotemur, ischyromyid rodents, Coryphodon, Hyrachyus, and cf. Hyracotherium) occur also in Europe. The lfkely Wasatchian age for at least the butk of the Eureka Sound Formation mammalian fauna places it at a point in time slightly after the proposed termination of fauna continuity between Europe and North America. The diversity of the fauna and the taxonomic similarity to southern faunas suggests markedly similar climatic conditions across much of the Paleogene Northern
121
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Hemisphere. Such similarity necessitates reexamination of the paleoclimatic history of the far North. The absences from the current Eureka Sound Formation fauna are interesting, though with the relatively small sample size, many of them are not particularly significant at this time. Perhaps the most surprising absence, especially with the close North American relationship, is Hyopsodus. This small condylarth is a prominent part of virtually all Wasatchian and Bridgerian faunas in the American West, and is physically large enough to be readily collected during surface prospecting. Of somewhat less consequence is the absence of primate diversity, especially in the northarctid/ adapidadapid/omomyid area. Fairly small physical size could be a factor here. No marsupials, phena~ codont condylarths or artiodactyls have been found. Marsupials of the family DMelphidae are very small and could easily have been overlooked. Phenacodus and Ectocion are uncommon in the later Wasatchian, as the Phenacoclontidae were rapidly decreasing in relative abundance (West, 1976,), so the absence is not stri:king. Artiodaceyls are relatively uncommon in ~he late W'asatc,hian and Bridgerian, so once again the absence is not particularly important. Rodent and insectivore diversity in the Eureka Sound Formation fauna is very low, but the sinai1 expected physical size allows specimens to be easily overlooked. Approximately one hundred kilos of washed concentrate were shipped south. This material was collected from several of the more productive surface local~ities. Initial results from the picking in,dicare that the fauna will be further expanded, and some absences eliminated,
CONCLUSIONS 1. A Paleogene continental vertebrate fauna of considerable diversity occupied the northeastern corner of North America. This assemblage contains at least thirty species of tetrapods. 2. The vertebrate fossils collected from the Eureka Sound Formation on Ellesmere Island were found in lithologies similar to those of fossiliferous rocks far to the south. The most productive facies are fine and medium-grained channel sandstones,
while bones are also found in finer-grained continental and marine sediments. These represent both continental and marginal aquatic environments. 3. The composition of the Eureka Sound Formation mammalian assemblage most closely resem~ bles that of the North American Wasatchian. However, the assemblage does not exactly correspond with any produced from the presently recognized subdivisions of the Wasatchian.
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4. A p p r o x i m a t e l y 50 % of the reasonably confidently identified genera in the E u r e k a Sound Formation are held in common in N o r t h America and E u r o p e ; the other 50 % are unique to N o r t h America or are present also in Asia. 5. T h e composition of the assemblage suggests that it dates from a short time after the termination of physical continuity between E u r o p e and N o r t h America. 6. Evidence thus far obtained from the E u r e k a Sound Formation does not contribute either to placing a biochronologic date on the separation of N o r t h America a n d Europe, or to verifying a specific eastern exchange area. 7. T h e occurrence and a b u n d a n c e of fossil vertebrates in the E u r e k a Sound Formation in the B a y / S t r a t h c o n a Fiord area of Ellesmere Island, along with the extensive unprospected exposures of that formation, suggest the strong likelihood that future field w o r k will increase the diversity and geographic a n d stratigraphic distribution of the fauna.
122 - Frequency Order Proteutheria
Family Leptictidae el. Palaeictops sp. Family Pantolestidae
R
Pantolestes of. natans Order Dermoptera Family Plagiomenidae
M
Plagiomenid sp. 1 Plagiomenid sp. 2 Plagiomenid sp. 3
C C
M
Order Primates
Family Paromomyidae Phenacolemur small sp. Phenacolemur large sp.
R R
Order R odentia Family Ischyromyidae ischyromyid sp. 1 ischyromyid sp. 2
R R
Order Taenidonta
Family Stylinodontidae of. Stylinodon sp. ACKNOWLEDGEMENTS We are grateful for the financial support of the National Geographic Society in 1973 and 1976 and the Arctic Institute of North America in 1975. The Polar Continental Shelf Project provided logistics support all three seasons; George Hohson, Fred Alt and Frank Hunt of that or0anization have been most helpful and understanding. Dr. Ray Thorsteinsson and the Geological Survey of Canada Arctic research group in Calgary have provided useful advice, information and moral support. Malcolm C. McKenna, J. Howard Hutchison, Leonard Krishtalka, Leonard Radinsky, Howard Schorn, and Bruce Welton have provided valuable advice on identifications of the fossils. All the fossil vertebrates collected from the Eureka Sound Formation are catalogued into the collections of the Division of Paleontology, National Museum of Canada, and are indicated by the abbreviation NMC.
R
Order Pantodonta
Family Coryphodontidae Coryphodon sp.
C
Order Carnivora (?)
Creodonta (?) Condylarthra (?) Family undetermined carnivora indet, sp. 1 carnivora indet, sp. 2 carnivora indet, sp. 3
R R R
Order Perissodactyla
Family Brontotheriidae Lambdotherium ef. popoagicum Family Hyrachyidae Hyrachyus large sp. Hyrachyus small sp. Family Equidae cf. Hyracotherium sp. R : 1 only
M : 2-4
M C R R
C : 5 or more
TaN. 1 - Mammalian faunal list Eureka sound formation.
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(19'76). - -
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WOOD H. E. 2nd (1934). - - Revision of the Hgrachgidae. Bull. Amer. Mus. Nat. Hist., New York, 67 (5), p. 181-29'5. ZIF,GLER P. A. (1975). - - The geological evolution of the North Sea area in the tectonic framework of north western Europe. No rges 9eo,l. undersokelse, n ° 3'16 (in Whiteman A.J. et al., eds., Bull. 29, Petroleum Geology and Geology of the North Sea and the Northeastern Atlantic Continental Margin, Proceedings o[ a Co,n[erence, Univ,ersitg o[ Bergen, December 1973) p. 1-27.