Journal of Vertebrate Paleontology 25(1):1–7, March 2005 © 2005 by the Society of Vertebrate Paleontology
ADDITIONS TO THE EOCENE SELACHIAN FAUNA OF ANTARCTICA WITH COMMENTS ON ANTARCTIC SELACHIAN DIVERSITY JÜRGEN KRIWET Ludwig-Maximillians-University, Faculty of Geosciences, Department of Earth and Environmental Sciences, Section of Paleontology, Richard-Wagner-Str. 10, D-80333 Munich, Germany,
[email protected]
ABSTRACT—Antarctic Eocene selachians were reported from the La Meseta Formation of Seymour Island and from glacial erratics of Mount Discovery, Antarctica. Seymour Island has produced the most diverse Palaeogene selachian fauna of the Southern Hemisphere so far. Up to now, 23 selachian taxa (20 sharks, 2 rays) have been described from the Eocene of Antarctica. Recent geological and palaeontological investigations on Seymour Island yielded new selachian remains from Lutetian (middle Eocene) deposits. An upper tooth is referred to the requiem shark Carcharhinus and a rostral spine to the sawfish Pristis. These occurrences represent the first Eocene records of both groups in the Southern Hemisphere and extend their geographic distribution. In addition, a fragmentary stinging ray attributed to Myliobatoidea is presented for the first time from Antarctica. The diversity of Eocene La Meseta fishes is reflected.
In the last few years, new fish material was collected from Late Cretaceous and Paleogene deposits of Antarctica by field parties of the British Antarctic Survey and the Instituto Antartico Argentino that provides new insights in the diversity of Antarctic post-Jurassic fishes. Here, I report on new selachian records from the Eocene Antarctica.
INTRODUCTION Antarctica, located today in the Southern Ocean, is one of the most remote and coldest places in the world. This ocean forms about 10% of the world’s ocean surfaces and plays a key-element in understanding both Earth processes and global climate changes. The modern fish fauna is striking in its low diversity dominated by notothenioid fishes. The fossil history of these fishes and their phylogenetic relationships are still obscure. The evolution of the distinct modern Antarctic fish fauna is related to low temperatures, isolation of the Southern Ocean due to the break-up of Gondwana, habitat loss, and climatic cycles (Clarke and Johnston, 1996). In the late Eocene, Antarctica became separated from the surrounding continents by opening of the Tasman and Drake passages initiating deep and shallow circumpolar circulations and the thermal isolation of the Antarctic continent (Dingle and Lavalle, 2000). Fossil fish remains are mainly known from the Palaeogene leaving a gap of almost 30 million years in the fossil record of Antarctic fishes. A few teleost skeletons were discovered from King George Island (Southern Shetland Islands) in the Atlantic sector of Antarctica (A. Gazdzicki, pers. comm. 2002). These specimens might give some new insights in the evolutionary history of modern Antarctic fish faunas. Selachians are rather rare in Antarctic waters today. Isolated fossil fish remains from Antarctica were first reported by Woodward (1908) from Cretaceous-Tertiary strata of Seymour and Snow Hill Islands. Additional Mesozoic and Tertiary finds enriched subsequently the knowledge of post-Palaeozoic Antarctic fish faunas (e.g., Schaeffer, 1972; Chatterjee and Zinsmeister, 1982; Grande and Eastman, 1986; Grande and Chatterjee, 1987; Richter and Ward, 1990). Tertiary Antarctic fishes are mainly known from Seymour Island. Here middle and upper Eocene marine sediments of the La Meseta Formation yielded the most diverse Palaeogene ichthyofauna from the Southern Hemisphere (e.g., Balushkin, 1994; Doktor et al., 1996; Jerzmanska, 1988; Eastman and Grande, 1989, 1991). So far, 22 selachian taxa within 14 families (including two batoids) have been reported from different localities on Seymour Island and from different levels within the La Meseta Formation (Cione and Reguero, 1995, 1998: Long, 1992a, b, c; Welton and Zinsmeister, 1980). Recently Long and Stilwell (2000) reported on rare selachian teeth from Eocene deposits of Mount Discovery in East Antarctica. This material includes the first record of Galeorhinus for Antarctica.
LOCALITY AND GEOLOGICAL SETTING J. J. Hooker of the British Museum of Natural History, London collected the selachian remains described in this paper during an expedition to Seymour Island by the British Antarctic Survey in the beginning of 1989 (“James Ross Island Scientific Cruise”). Seymour Island is situated at 64º17’S in the Larsen Basin that is situated to the east of the northern tip of the Antarctic Peninsula and is one of a number of sedimentary basins in the southern South America–Antarctic Peninsula region (Fig. 1). The marine fill is most extensively exposed in the James Ross Island region (e.g., Zinsmeister, 1982; Hathway, 2000). Seymour Island forms with James Ross and Snow Hill Islands one of the most productive fossil vertebrate sites in the Southern Hemisphere. Seymour Island is rather small being about 20 km long and 9 km wide. Sediments of the late Maastrichtian – early Paleocene Lopez de Bertodano and Paleocene Sobral Formations cover the southern 2/3 of the island while the Eocene La Meseta Formation crops out at the northern part. Zinsmeister (1998) described the K-T boundary section of Seymour Island in detail. The La Meseta Formation overlies the Paleocene deposits unconformably in the form of a small trough or large channel (Sadler, 1988). The La Meseta Formation consists of about 800 m sands interbedded with bioturbated sandy muds, and sand/mud heteroliths, which are rich in marine and terrestrial fossils in some parts (Gazdzicki, 1998, 2001). These sediments were deposited in shallow, near coastal to estuarine environments in the lower parts and open-marine shelf areas in the upper parts (Myrcha et al., 2002). Deposition took place from the late Ypresian to the Priabonian according to Sr isotope datings (Dingle and Lavalle, 1998). The La Meseta sediments are subdivided either into three transgressive-regressive cycles (Unites I to III; Elliot and Trautman, 1982) or seven major lithofacies (Telms 1 to 7; Sadler, 1988). 1
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FIGURE 1. Index map of Seymour Island at the north-eastern tip of the Antarctic Peninsula (A) and the fossil bearing localities near Cape Wiman indicated by an arrow (B).
FIGURE 2. Upper tooth of Carcharhinus sp. (BAS P.153.113) from the “Bottom Coquina surface” at Cape Wiman, Telm 3, Lutetian. A, lingual view. B, labial view. C, camera lucida drawing, lingual view. D, camera lucida drawing, mesial view. E, camera lucida drawing, labial view. Scale bars equal 2.0 mm.
MATERIAL AND METHODS The material collected by J.J. Hooker consists of isolated remains of selachians and actinopterygians and was obtained by screen washing of unconsolidated sediments near Cape Wiman near the northwestern tip of Seymour Island. The sediments are referred to Unite II of Eliot and Trautman (1982) and include Telms 3 to 5. The material include abundant selachian teeth containing a carcharhiniform tooth from Telm 3 and a batoid rostral spine from Telm 4 and are of Lutetian age. All material described here is deposited in the fossil fish collection of the British Museum of Natural History (Department of Palaeontology) and have registration numbers prefixed by “BAS” meaning “British Antarctic Survey.” The specimens were cleaned with H2O2 and examined and drawn under a Wild M5 microscope with camera lucida. Photos were prepared using a digital camera with high resolution. Comparative material includes selachian remains in the collections of the British Museum of Natural History, London and the Museum of Natural History in Berlin as well as material from private collections. The systematic and nomencalture used here is adopted from Cappetta (1987), Compagno (1988), and Carvalho (1996). SYSTEMATIC PALEONTOLOGY Class CHONDRICHTHYES Huxley, 1880 Subclass ELASMOBRANCHII Bonaparte, 1838 Infraclass NEOSELACHII Compagno, 1977 Division GALEOMORPHII Compagno, 1973 Superorder GALEOIDEA Carvalho, 1996 Order CARCHARHINIFORMES Compagno, 1973 Genus CARCHARHINUS Blainville, 1816 CARCHARHINUS sp. (Fig. 2) Material—BAS P.153.113: a single tooth from the “Bottom Coquina surface” at Cape Wiman, Telm 3, Lutetian. Description—The tooth crown is single-cusped without lateral cusplets. The labial face is flat, the lingual one convex. The tooth
neck is slightly curved in lingual view. The crown has a slight sigmoidal appearance in mesial view (Fig. 2D). The labial face of the crown has a straight basal margin that does not overhang the root. The pointed cusp is narrow and distally inclined. The cutting edges are smooth and extend to the base of the crown. The cusp is separated from the lateral heels by shallow angular notches. The lateral heels are elongated and unserrated, the distal one being higher than the mesial one in labial view. The cusp and lateral heels are smooth without any ornamentation. The crown-root junction is curved in lingual view whereas the labial one is straight. The root is not very high and mesiodistally elongated and extends below the lateral heels. The lingual root protuberance is weak and the groove separating the root lobes is rather shallow. A fairly large central foramen opens on the lingual root face in the groove. The root branches are well separated and have a more or less oval outline. The mesial edge is almost regularly curved whereas the distal one tapers slightly. The basal margin of the root is concave in lingual view. The root groove is inconspicuous in labial aspect. Remarks—The tooth displays characters that are found in carcharhiniforms (e.g., holaulacorhize root, single-cusped crown, lateral heels). Single-cusped teeth with lateral heels are present, at least in one of the jaws, in Galeorhinus, Paragaleus, Rhizoprionodon, Scoliodon, Loxodon, Sphyrna, Galeocerdo, and Prionace. The specimen from Seymour Island differs in several features from teeth of these carcharhiniforms. The tooth crown is upright, contorted, and serrated in Galeocerdo. The serrated cutting edges do not extend to the base of the crowns in Prionace. The teeth of most Sphyrna species differ in the presence of a deep notch between the distal heel and the cusp and in a more robust crown (with the exception of the extant Sphyrna mokarran). The teeth of Loxodon have very convex labial and lingual crown faces (also found in Scoliodon) and a more or less sigmoidal mesial cutting edge. Teeth of Scoliodon have generally no distal heels. The main cusp is elongated with the vertical axis being more or less twisted. Two teeth assigned to Scoliodon from
KRIWET—ANTARCTIC EOCENE SELACHIANS Seymour Island were described by Long (1992a). The most important distinguishing feature of Rhizoprionodon is the recurved tip of the cusp. BAS P.153.113 most closely resembles teeth of the carcharhinids Carcharhinus and Negaprion. The pointed and distally bent cusp and the widely separated and mesio-distally extended root branches with the mesial lobe being longer indicate a lateral to latero-posterior upper jaw position. Carcharhiniform sharks are characterized by a dignathic heterodonty. This can be rather weak (e.g., Loxodon, Scoliodon, Rhizoprionodon, Isogomphodon, Triaenodon) or strong (Carcharhinus, Nasolamia, Lamiopsis, Prionace, Glyphis, Negaprion, Hemipristis) (Herman et al., 1991). Consequently, isolated teeth of genera such as Negaprion and Carcharhinus are sometimes difficult to distinguish, especially those from posterior positions. The upper teeth of most post-Eocene Carcharhinus spp. have a rather broad cusp with serrated cutting edges. The cusp of lower teeth is narrow and upright or slightly distally bent with or without serrations depending on the species. This led to taxonomic confusion and many fossil teeth of Carcharhinus were assigned to different genera or lumped together in a single species (e.g., C. egertonia). Most Eocene carcharhinids have partially or completely unserrated cusps render their identification and attribution difficult (B. Heim, pers. comm. 2002). An angular notch on both sides of the crown characterizes the teeth of Negaprion and Carcharhinus. In this feature, the specimen from Seymour Island resembles both although the mesial notch is very shallow, almost subtle. In comparison to both fossil and extant forms BAS P.153.113 is very similar to upper lateral teeth of “Negaprion” and Carcharhinus from the Eocene in the presence of a rather wide but flat and unserrated cusp, a more curved basal face of the root, a weak lingual root protuberance, and a rather shallow groove. Lower teeth of Carcharhinus have generally an upright cusp and a more or less straight basal root face. The most important feature to differentiate teeth of Negaprion from lower teeth of Carcharhinus is the presence of faint but distinct serrations at least on the heels in the latter. The root does not or slightly protrude lingually in Carcharhinus spp. and the groove is comparably deeper. The Seymour specimen is referred here to Carcharhinus taking into account the difficulties in distinguishing Eocene carcharhinid selachian teeth. Variations of the specific characters mentioned above are the general feature in extant carcharhiniform taxa. The extant species of the requiem sharks Carcharhinus have a cosmopolitan distribution mainly in tropical but also subtropical latitudes and range from the surface to depth about 500 m (Compagno, 1984). The closely related genus Negaprion is today restricted to tropical latitudes and occurs along the eastern Pacific coasts from Baja California to Ecuador, along the western Atlantic coast-lines from New Jersey to southern Brazil (southernmost occurrence), and along the costs off West Africa (Compagno, 1984). It ranges from the intertidal zone to about 92 meters. Eocene records of both genera have only been known from the Northern Hemisphere up to now. The teeth of Negaprion amekiensis from the middle Eocene of Nigeria (White, 1926) are close to Carcharhinus (Cappetta, 1987). Woodward (1895) described the species gibbesi and attributed it to Carcharias (Aprionodon). Based on the overall morphology this species may belong to Carcharhinus. This species occurs in the Eocene of Alabama, North Carolina, Virgina, U.S.A. and Egypt as well as in the Oligocene of North and South Carolina and in the early Miocene of North Carolina (Williams, 1999). This rather long stratigraphic distribution indicates that “C.” gibbesi may represent an unnatural grouping. Case and West (1991) attributed some teeth from the late Eocene Drazinda Shale of Pakistan to Negaprion eurybathrodon. This species was also reported from the late Eocene of Georgia,
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U.S.A. (Case and Borodin, 2000a). “N.” kraussei occurs in the middle Eocene of North Carolina (Case and Borodin, 2000b). The Eocene species Carcharhinus frequens (Dames, 1883) from Egypt is similar to the Antarctic species but differs in the presence of a cutting edge that is restricted to the upper parts of the crown and in having differently shaped root lobes. On the whole, the attribution of the species frequens to Carcharhinus seems justified because of the strong lingual root protuberance in lower teeth and the short cutting edges. The upper teeth show the characteristic Carcharhinus-like morphology. C. gilmori (Leriche, 1942) occurs in the middle Eocene of Virginia, U.S.A., C. marcaisi (Arambourg, 1952) in the middle Eocene of Morocco, C. woodwardi (Leriche, 1905) in Belgium, and specific unidentified remains have been reported from the middle Eocene of England (e.g., Williams, 1999). However, the attribution of all these specimens to Carcharhinus is not well established and may be regarded as a more conservative approach in interpreting these tooth morphologies. In the Miocene, Carcharhinus and Negaprion are rather widespread and exhibit a more or less cosmopolitan distribution (e.g., Cappetta, 1987; Williams, 1999). The specimen from the middle Eocene of Seymour Island is the most southern record of Carcharhinus known to date (Fig. 3). So far, no specimens of Carcharhinus or Negaprion have been recovered from Palaeocene deposits indicating, that both genera originated in the Eocene and achieved a wide distribution including both Northern and Southern Hemispheres early in their evolutionary history. Division SQUALEA Shirai, 1992 Superorder HYPNOSQUALEA Carvalho and Maisey, 1996 Order RAJIFORMES Berg, 1940 Suborder PRISTOIDEI Cappetta, 1980 Family PRISTIDAE Bonaparte, 1838 Genus PRISTIS Linck, 1790 PRISTIS sp. (Fig. 4) Material—BAS P.159.115a: a fragmentary rostral spine from Cape Wiman, Telm 4, Lutetian. Description—The single specimen is a fragmentary rostral spine lacking the base and the tip. It measures 21 mm in height and 6 mm in width. The enameloid forms a rather thin layer on the dentine and is devoid of any ornamentation. The spine is dorso-ventrally flat, slightly curved, and tapers towards the apex. The dorsal and ventral sides are rather flat and only slightly convex. The anterior face is very convex and acute but without a distinct cutting edge. The posterior edge is relatively broad and concave, forming a groove that runs from the apex to the base. The spine is sub-triangular in cross-section (Figure 5c).
FIGURE 3. Distribution of Eocene carcharhiniform taxa referred to Carcharhinus and Negaprion. Palaeogeographic base map modified from Scotese (1999).
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JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 25, NO. 1, 2005 Modern pristids are demersal and amphidromous inhabiting sandy or muddy bottoms of shallow coastal waters, estuaries, river mouths as well as freshwater rivers and lakes. They are widespread in warm-temperate to tropical latitudes. The fossil record of Pristis ranges back to the Ypresian (Cappetta, 1987) and already exhibits a rather wide distribution in the Eocene (Belgium: P. brevis Casier, 1949, P. lathami, P. praecursor Casier, 1949 P. propinquidens Casier, 1946; Egypt: P. lathami P. prosulctus Stromer, 1905; England: P. lathami; France: P. lathami; Morocco: P. hamatus White, 1926, P. lathami; Netherlands: P. propinquidens Casier, 1946; Togo: P. lathami; U.S.A.: P. lathami, P. pickeringi Case, 1981; Uzbekistan: P. sp.; West Africa: P. olbrechtsi Dartevelle and Casier, 1959; Fig. 5). The occurrence of Pristis in shallow, coastal waters of Antarctica extends its geographic distribution considerably. Order MYLIOBATIFORMES Compagno, 1973 Superfamily MYLIOBATOIDEA Compagno, 1973 Family and genus indeterminate Fig. 6
FIGURE 4. Fragmentary rostral spine of Pristis sp. (BAS P.159.115a) from,Telm 4, Lutetian, of Cape Wiman. A, dorsal (?) view. Scale bar equals 0.5 cm. B, ventral (?) view. Scale bar equals 0.5 cm. C, crosssection. Scale bar equals 0.25 cm.
Remarks—I follow here Herman et al. (1997) in calling the tooth-like structures along the flattened rostrum of sawfishes rostral spines because their morphology is different from that of oral teeth. Fossil sawfishes of the suborder Pristoidei include members of the genera Peyeria, Propristis, Anoxypristis, and Pristis. The latter two are the only extant sawfishes. Peyeria is known so far only from Cenomanian deposits in North Africa (e.g., Cappetta, 1987). The spines are broadly triangular and funnel-shaped at their base. This morphology is quite untypical and the rest of pristids first appear in the Eocene. Consequently, Cappetta (1987) assumes that these structures may represent dermal thorns. The spines of Propristis are lacking enameloid and are almost as wide as high. There are two cutting edges and vertical grooves at the base. Propristis displays a rather wide geographic distribution and is known from many Eocene localities in Africa, Europe, and the U.S.A. The present specimen from Seymour Island most closely resembles rostral spines of Anoxypristis and Pristis in its general morphology. The presence of a posterior groove instead of a cutting edge relates the specimen to Pristis. Juvenile spines may lack this posterior groove (Purdy et al., 2001). Consequently, the Antarctic specimen is interpreted as belonging to an adult individual despite its rather small size.
FIGURE 5. Distribution of Eocene Pristis spp. Palaeogeographic base map modified from Scotese (1999).
Material—BAS P.159.115b: a fragmentary stinging ray, Telm 4, Ypresian. Description—The single specimen is rather fragmentary but exhibits the typical morphology of myliobatiform stinging spines. It is dorsoventrally flattened with serrated lateral margins. The serrae are rather small with the apex being bent downwards. Remarks—Stinging spines are often referred to the stingray Dasyatis. However, there are several families of myliobatiforms with caudal stinging spines. Welton and Zinsmeister (1980) described a single myliobatiform tooth from a fossiliferous shell bank in Unit II of the la Meseta Formation, Seymour Island, and placed it within the superfamily Myliobatoidea. Long (1992a) while describing a diverse selachian fauna from La Meseta Formation of Seymour Island did not indicate any remains of myliobatiforms in the collection he used. In addition, myliobatiform remains have not been encountered by anyone else so far. More than 100 additional teeth in the collections of the BMNH ranging from Telm 3 to Telm 5 indicate that myliobatiforms were not that rare in Antarctic waters during the Eocene as previously assumed. The spine fragment can be referred to the same group as the teeth and represents the first published record of this kind of ichthyodorulites from Antarctica. DIVERSITY OF EOCENE ANTARCTIC SELACHIANS The presence of Carcharhinus sp. and Pristis sp. in the middle Eocene of the Antarctic Peninsula extends the distribution of both groups in the Eocene. So far, the Eocene selachian fauna of Antarctica including the records from Seymour Island (e.g., Welton and Zinsmeister, 1980; Long, 1992a; Cione and Reguero,
FIGURE 6. Fragmentary stinging ray of Myliobatoidea indet. (BAS P.159.115b) from Telm 4, Ypresian, of Cape Wiman. Ventral (?) view. Scale bar equals 0.5 cm.
KRIWET—ANTARCTIC EOCENE SELACHIANS 1995, 1998) and Mount Discovery (Long and Stilwell, 2000) contained 23 taxa. The two taxa described here increase the number of shark (22) and ray taxa (3) (Appendix 1). The oldest fossil record of the carcharhinids Carcharhinus is from the middle Eocene (e.g., Cappetta, 1987) while remains of pristids referred to Pristis are known from the Paleocene (Thanetian) (e.g., Case, 1994). The temporal and spatial distributions of Carcharhinus and Pristis spp. in the Northern and Southern Hemispheres (Figs. 4, 6) of indicate that carcharhinids and pristids were already widely distributed prior to the middle Eocene and suggest that the origin of both probably dates back at least into earliest Paleogene. The Eocene selachian fauna from Antarctica includes 25 species in 16 families (Appendix 1). 24 taxa and 15 families come from the Eocene La Meseta Formation of Seymour Island. The majority of taxa belongs to sharks while batoids are represented by only three taxa with a very uneven distribution in the sequence. Long (1992c) and Case (1992) analysed the ecology and diversity of the Eocene Seymour selachian fauna and concluded that the selachian fauna represents a cool-temperate fauna with different ecological components including tropical water immigrants (e.g., Pseudoginglymostoma, Stegostoma, Scoliodon). However, these authors did not take all known taxa into account and, moreover, did not analyse the distribution and composition of “assemblages” for every stratigraphic level (Telms 1–7) in relation to depositional environments and climatic conditions. Striking is the predominance of the lamniform shark Striatolamia macrota in all levels and associations. However, the selachian diversity is very low in Telm 1 when low-energy and/or protected environments (lagoon/estuarine) persisted in warm, wet, and seasonal climatic conditions until the middle Eocene (Myrcha et al., 2002). The diversity increased slightly following extension of seawater in the course of the transgressive event of Telm 1. A considerable, gradual cooling trend was established during the middle to late Eocene. Abrupt drops in sea surface temperatures occur at the early and middle Eocene boundaries and again in the late middle Eocene (Frakes et al., 1992). The gradual cooling towards the top of the La Meseta Formation is supported by the structure of the benthic fauna and sedimentological and oxygen isotope data (e.g., Stilwell and Zinsmeister, 1992; Aronso and Blake, 2001; Gazdzicki et al., 1992). The final Eocene cooling correlates with the Eocene/Oligocene boundary-cooling event in the Southern Ocean (e.g., Zachos et al., 2001). The highest diversity of selachians is found in Telms 4 and 5 when the climate changed to strongly seasonal and cooltemperate and coincides with a “polytaxic period” indicated by a remarkable increase in species diversity of many other oceanic groups such as planctic foraminifers, dinoflagellates, and teleosts (e.g., Fisher and Arthur, 1977). Open-marine conditions on the upper slope were established in the Telms 4 and 5. The presence of a cool-water selachian fauna that is partially represented by Paleocene relict taxa such as †Palaeohypotodus rutoti in the upper parts of the La Meseta Formation is in good accordance with the assumed temperature decline (D. Ward, pers. comm. 2002). In general, the diversity of Eocene Antarctic selachian faunas is rather low compared to other localities of the same age in the Northern Hemisphere and the taxonomic composition is remarkably mixed. Striking is the first appearance (e.g. Deania, Squalus with serrated cutting edges, Stegostoma, Pseudoginglymostoma, Lamna) and last appearance of selachian taxa (e.g., Anomotodon, Odontaspis winkleri, Palaeohypototus rutoti) in the La Meseta fauna. Selachians disappeared at the end of Telm 5 and no remains have been found in Telms 6 and 7 although actinopterygian remains as well as bones of whales and penguins are abundant in the upper parts of the La Meseta Formation. The disappearance
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of the cool water selachian association cannot be explained with the rapid temperature decline. The La Meseta deposits herald the final stage of the Gondwana break-up and onset of the late Eocene glaciation with ice-shield formation on the Antarctic Peninsula 4 million years later (Dingle and Lavalle, 2000; Dzik and Gazdzicki, 2001). The glaciation event may have reduced the shelf habitats dramatically forcing taxa of those areas to retreat. The increase of teleost diversity and cetacean evolution is linked to the progressive cooling of polar waters. The cooling of Antarctic waters and the thermal isolation of the Southern Ocean also initiated the evolution of cold water adaptations in teleosts. The occurrence of Carcharhinus and Pristis, both taxa confined today to warm-temperate to tropical waters in the cool waters of Eocene Antarctica indicates that both were not primary inhabitants but migrated along open trans-equatorial seaways into Southern Hemisphere waters. This interpretation is also supported by their rare finds. ACKNOWLEDGMENTS P. Forey, A. Longbottom, J. J. Hooker ( both British Museum of Natural History, London) and A. Crame (British Antarctic Survey, Cambridge) are acknowledged for the possibility to study the Antarctic fossil fish remains in the BMNH collection. A. Gazdzicki and A. Bittner (Polish Academy of Sciences, Warsaw) are thanked for their hospitality and help during a stay at their institution to study material collected by Polish Antarctic expeditions. I am deeply indebted to D. Ward (Orpington), B. Heim, and J. Bourdon (New York) for discussions on Antarctic selachians and Eocene carcharhiniform sharks as well as for suggestions. M. Gottfried (East Lansing) and an unknown reviewer are acknowledged for their constructive comments. M. Benton (Bristol) is thanked for his support and for the permission to use the facilities at Bristol University. This research has been supported by a Marie Curie Fellowship of the European Community program “Improving Human Research Potential and the Socioeconomic Knowledge Base” under contract number HPMF-CT2001–01310. LITERATURE CITED Aronso, B. R., and D. B. Blake. 2001. Global climate change and origin of modern benthic communities in Antarctica. American Zoologist 41:27–39. Balushkin, A. V. 1994. Proeleginops grandeastmanorum gen. et sp. nov. (Perciformes, Notothenioidei, Eleginopsidae) from the Late Eocene of Seymour Island (Antarctica) is a fossil notothenioid, not a gadiform. Journal of Ichthyology 34:10–23. Cappetta, H. 1987. Chondrichthyes II. Mesozoic and Cenozoic Elasmobranchii; pp. 1–193 in H.-P. Schultze (ed.). Handbook of Paleoichthyology Vol. 3B. Stuttgart and New York, Gustav Fischer Verlag. Carvalho, M. R. de 1996. Higher-level elasmobranch phylogeny, basal squaleans, and paraphyly; pp. 35–62 in M. L. J. Stiassny, Parenti, L. R., and G. D. Johnson (eds.). Interrelationships of Fishes. San Diego, Academic Press. Case, G. R. 1994. Fossil fish remains from the late Paleocene Tuscahoma and early Eocene Bashi Formations of Meridian, Lauderdale County, Mississippi. Palaeontographica A 230:97–138. Case, G. R., and R. M. West. 1991. Geology and Paleontology of the Eocene Drazinda Shale Member of the Khirthar Formation, central Western Pakistan, Part II: Late Eocene fishes. Tertiary Research 12:105–120. Case, G. R., and P. D. Borodin. 2000a. Late Eocene selachians from the Irwinton Sand Member of the Barnwell Formation (Jacksonian), WKA mines, Gordon, Wilkinson County, Georgia. Münchner Geowissenachaftliche Abhandlungen 39:5–16. Case, G. R., and P. D. Borodin. 2000b. A middle Eocene selachian fauna from the Castle Hayne Limestone Formation of Duplin County, North Carolina. Münchner Geowissenachaftliche Abhandlungen 39: 17–32.
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KRIWET—ANTARCTIC EOCENE SELACHIANS APPENDIX 1 Eocene selachians of Antarctica. Data from Long (1992c), Cione and Reguero (1995, 1998), Long and Stilwell (2000), and this study. (S) ⳱ Seymour Island, (M) ⳱ Mount Discovery. Family Hexanchidae Hexanchus sp. (S) Heptranchias howelli (S) Family Squalidae Squalus weltoni (S) Squalus woodburnei (S) Centrophorus sp. (S) Deania sp. (S) Dalatias licha (S) Family Pristiophoridae Pristiophorus lanceolatus (S) Family Squatinidae Squatina sp. (S) Family Stegostomatiidae Stegostoma cf. S. fasciatum (S) Family Ginglymostomatidae Pseudoginglymostoma cf. P. brevicaudatum (S)
Family Odontaspididae Striatolamia macrota (S, M [as cf. macrota]) Palaeohypototus rutoti (S) Odontaspis winkleri (S) Family Mitsukurinidae Anomotodon multidenticulatus (S) Family Lamnidae Isurus praecursor (S) Lamna nasus (S) Family Otodontidae Carcharocles auriculatus (S) Family Family Cetorhinidae Cetorhinus sp. (S) Family Triakidae Galeorhinus sp. (M) Family Carcharhinidae Scoliodon sp. (S) Carcharhinus sp. (S) Family Rajidae Bathyraja sp. (S) Family Pristidae Pristis sp. (S) Myliobatoidea fam., gen., sp. indet. (S)
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