Decapod crustaceans from the Late Cretaceous and the Eocene of ...
Decapod crustaceans from the Late Cretaceous and the Eocene of Seymour Island, Antarctic Peninsula R. M. FELDMANN Department of Geology Kent State University Kent, Ohio 44242
During the austral summer of 1983-1984, the second U.S.sponsored Seymour Island expedition conducted extensive paleontological field work to augment collections made during the first expedition, 2 years previously. On the first expedition, a small but very significant collection of decapod crustaceans was made. Thus, one of the express purposes of the 1983-1984 expedition was to supplement those collections and to make collections of decapod-associated organisms. As a result of that work, this paper reports the occurrence and distribution of no fewer than nine decapod taxa, three from the Cretaceous terrain and six from the Eocene. Prior to this time, only 21 species-level taxa of decapods had been described from Antarctica (Feldmann and Zinsmeister 1984, p. 1048), of which two were recently named species representing the only known Eocene forms from Seymour Island (Feldmann and Zinsmeister 1983, 1984). Earlier work on James Ross Island (Ball 1960) and Alexander Island (Taylor 1979) resulted in the description of 16 taxa ranging in age from Berriasian to Campanian. Subsequently, one of these species, Hoploparia stokesi, was noted from Seymour Island (Del Valle and Rinaldi 1975). The decapod assemblages from the Cretaceous of Seymour Island appear to resemble most closely the Campanian occurrences noted on James Ross Island, whereas the Eocene occurrences of Seymour Island are unique.
Cretaceous occurrences. Two locations in the Late Cretaceous Lopez de Bertodano Formation (figure 1, localities 1 and 2) yielded a large number of decapod specimens. All of them are macrurans (lobster-like forms) and most are referrable to the nephropid species Hoploparia stokesi (Weller), 1903 (Ball 1960) (figure 2). Several fragmentary remains of another, more highly ornamented form, have been tentatively referred to the erymid genus Enoploclytia. The third taxon is represented by a single specimen of carapace and abdomen referrable, with certainty, to the palinurid genus, Linuparus. These notices represent the first published record of Enoploclytia from Campanian rocks of Antarctica and the first notice of Linuparus from the continent.
4
Figure 2. Fossil decapods from Seymour Island. A. Hoploparla
stokesL B. Lyreldus antarct!cus. C. Chasmocarcinus seymourensis. Bar scales represent one centimeter. Notice that H. stokes! Is preserved in a concretion in the classic Salter's Position, Indicating that It is a molted skeleton.
SEYMOUR ISLAND DECAPOD LOCALITIES
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/ Figure 1. Location map of Seymour Island (64 015'S 56045'W) showing the locations of the 15 sites where decapod fossils have been collected. ANTARCTIC JOURNAL
All of the Cretaceous decapod material is well preserved in concretions so that carapace material is intact and, particularly in the case of Hoploparia stokesi, many of the specimens are articulated. There is no evidence of post-mortem transportation. First noted by del Valle and Rinaldi (1975), the fauna is significant in that it provides a firm tie with the decapod assemblage described from James Ross Island (Ball 1960). At the same time, the number of Cretaceous species has now been expanded. The absence of brachyurans (crab-like forms) in not atypical of Cretaceous assemblages and may reflect their scarcity or sampling bias. Eocene occurrences. Brachyurans are the dominant forms collected from the Eocene La Meseta Formation. In this unit, at least five distinctly different species of brachyurans and one species of anomuran, the ghost-shrimp Callianassa (figure 1, locality 4), have been collected, Decapod fossils are relatively common in the middle and upper part of the formation where they are most commonly preserved in concretions but occasionally can be found as loose specimens. The crab fauna of the La Meseta Formation is overwhelmingly dominated by Lyreidus antarcticus figure 2, item B, figure 3). This species has been collected from no fewer than eight sites (figure 1, localities 3, 4, 6, 7, 8, 10, 13, and 15) and is now represented by over 100 specimens. Invariably, this species is preserved in concretions and is exceptionally well preserved so that nearly all hard parts ultimately can be described. The other occurrences of crabs consist of one or only a few specimens but all are significant because they represent first occurrences from Antarctica and, in many cases, the earliest occurrences of the taxon in the fossil record. Of these, only Chasmocarcinus seymourensis (Feldmann and Zinsmeister (1984) (figure 1, locality 14; figure 2, item c) has previously been described. The remaining species include a dromiacian (figure 1, localities 4, 9, and 12), a calappid (figure 1, locality 12), and a portunid (figure 1, locality 12). Study of the Eocene forms has already yielded valuable information ragarding the evolution and biogeography of southern hemisphere forms (Feldmann and Zinsmeister 1984; Zinsmeister and Feldmann 1984). Description and interpretation of the taxa reported here for the first time will provide additional valuable information regarding the history of decapod faunas. Summary. Collections of decapods made during the 1983-1984 field season has increased the known occurrences on Seymour Island from three to nine, has provided numerous additional specimens of Lyreidus antarcticus which will make possible the detailed study of the comparative anatomy of that species, has confirmed the close association of the decapod faunas of James Ross Island with that of the Lopez de Bertodano Formation of Seymour Island, and greatly has enlarged the sample of Hoploparia stokesi which will enhance our understanding of that form. Finally, these discoveries reconfirm the key position of the study of the paleontology of Seymour Island to
1984 REVIEW
019
a
Figure 3. Closeup view of some of the fossil Lyreidus antarcticus collected from the site of its greatest abundance, locality 6.
the interpretation of the Cenozoic history of the southern hemisphere. This research was supported by National Science Foundation grant DPP 82-13985 to William J. Zinsmeister. Other members of the research team were Frederick Barbis, Judd Case, Dan Chaney, Sankar Chatterjee, Brian Huber, Carlos Macellari, Michael Nickel, James Robinson, Peter Sadler, Brian Small, Michael Woodburne, and William Zinsmeister.
References Ball, H.W. 1960. Upper Cretaceous Decapoda and Serpulidae from James Ross Island, Graham Land. Falkland Islands Dependencies Survey Scientific Reports, 24, 1-30. Feldmann, R.M., and W.J. Zinsmeister. 1983. New crabs from the La Meseta Formation (Eocene) of Antarctica: Biogeography and paleoecology. Geological Society of America Abstracts with program, 15(6), 571. Feldmann, R.M., and W.J. Zinsmeister. 1984. New fossil crabs (decapoda: brachyura) from the La Meseta Formation (Eocene) of Antarctica: Paleogeographic and biogeographic implications. Journal of Paleontology, 58(4), 1046-1061. Taylor, B.J. 1979. Macrurous decapoda from the Lower Cretaceous of southeastern Alexander Island. British Antarctic Survey Scientific Reports, 81, 1-39. Valle, R.A. del, and C.A. Rinaldi, 1975. Additions to the presence of Hoploparia stokesi (Weller) in the "Snow Hill Island Series," on Vicecomodoro Marambio Island, Antarctica. Contribucion del Inst it uto Antartica Argentino, 190, 1-21. (In Spanish.) Zinsmeister, W.J., and R.M. Feldmann. 1984. Cenozoic high latitude heterochroneity of Southern Hemisphere marine faunas. Science, 224(4646), 281-283.
During the austral summer of 1983-1984, the second U.S.sponsored Seymour Island expedition conducted extensive paleontological field work to augment collections made during the first expedition, 2 years previously. On the first expedition, a small but very significant collection of decapod crustaceans was made. Thus, one of the express purposes of the 1983-1984 expedition was to supplement those collections and to make collections of decapod-associated organisms. As a result of that work, this paper reports the occurrence and distribution of no fewer than nine decapod taxa, three from the Cretaceous terrain and six from the Eocene. Prior to this time, only 21 species-level taxa of decapods had been described from Antarctica (Feldmann and Zinsmeister 1984, p. 1048), of which two were recently named species representing the only known Eocene forms from Seymour Island (Feldmann and Zinsmeister 1983, 1984). Earlier work on James Ross Island (Ball 1960) and Alexander Island (Taylor 1979) resulted in the description of 16 taxa ranging in age from Berriasian to Campanian. Subsequently, one of these species, Hoploparia stokesi, was noted from Seymour Island (Del Valle and Rinaldi 1975). The decapod assemblages from the Cretaceous of Seymour Island appear to resemble most closely the Campanian occurrences noted on James Ross Island, whereas the Eocene occurrences of Seymour Island are unique.
Cretaceous occurrences. Two locations in the Late Cretaceous Lopez de Bertodano Formation (figure 1, localities 1 and 2) yielded a large number of decapod specimens. All of them are macrurans (lobster-like forms) and most are referrable to the nephropid species Hoploparia stokesi (Weller), 1903 (Ball 1960) (figure 2). Several fragmentary remains of another, more highly ornamented form, have been tentatively referred to the erymid genus Enoploclytia. The third taxon is represented by a single specimen of carapace and abdomen referrable, with certainty, to the palinurid genus, Linuparus. These notices represent the first published record of Enoploclytia from Campanian rocks of Antarctica and the first notice of Linuparus from the continent.
4
Figure 2. Fossil decapods from Seymour Island. A. Hoploparla
stokesL B. Lyreldus antarct!cus. C. Chasmocarcinus seymourensis. Bar scales represent one centimeter. Notice that H. stokes! Is preserved in a concretion in the classic Salter's Position, Indicating that It is a molted skeleton.
SEYMOUR ISLAND DECAPOD LOCALITIES
/
/ Figure 1. Location map of Seymour Island (64 015'S 56045'W) showing the locations of the 15 sites where decapod fossils have been collected. ANTARCTIC JOURNAL
All of the Cretaceous decapod material is well preserved in concretions so that carapace material is intact and, particularly in the case of Hoploparia stokesi, many of the specimens are articulated. There is no evidence of post-mortem transportation. First noted by del Valle and Rinaldi (1975), the fauna is significant in that it provides a firm tie with the decapod assemblage described from James Ross Island (Ball 1960). At the same time, the number of Cretaceous species has now been expanded. The absence of brachyurans (crab-like forms) in not atypical of Cretaceous assemblages and may reflect their scarcity or sampling bias. Eocene occurrences. Brachyurans are the dominant forms collected from the Eocene La Meseta Formation. In this unit, at least five distinctly different species of brachyurans and one species of anomuran, the ghost-shrimp Callianassa (figure 1, locality 4), have been collected, Decapod fossils are relatively common in the middle and upper part of the formation where they are most commonly preserved in concretions but occasionally can be found as loose specimens. The crab fauna of the La Meseta Formation is overwhelmingly dominated by Lyreidus antarcticus figure 2, item B, figure 3). This species has been collected from no fewer than eight sites (figure 1, localities 3, 4, 6, 7, 8, 10, 13, and 15) and is now represented by over 100 specimens. Invariably, this species is preserved in concretions and is exceptionally well preserved so that nearly all hard parts ultimately can be described. The other occurrences of crabs consist of one or only a few specimens but all are significant because they represent first occurrences from Antarctica and, in many cases, the earliest occurrences of the taxon in the fossil record. Of these, only Chasmocarcinus seymourensis (Feldmann and Zinsmeister (1984) (figure 1, locality 14; figure 2, item c) has previously been described. The remaining species include a dromiacian (figure 1, localities 4, 9, and 12), a calappid (figure 1, locality 12), and a portunid (figure 1, locality 12). Study of the Eocene forms has already yielded valuable information ragarding the evolution and biogeography of southern hemisphere forms (Feldmann and Zinsmeister 1984; Zinsmeister and Feldmann 1984). Description and interpretation of the taxa reported here for the first time will provide additional valuable information regarding the history of decapod faunas. Summary. Collections of decapods made during the 1983-1984 field season has increased the known occurrences on Seymour Island from three to nine, has provided numerous additional specimens of Lyreidus antarcticus which will make possible the detailed study of the comparative anatomy of that species, has confirmed the close association of the decapod faunas of James Ross Island with that of the Lopez de Bertodano Formation of Seymour Island, and greatly has enlarged the sample of Hoploparia stokesi which will enhance our understanding of that form. Finally, these discoveries reconfirm the key position of the study of the paleontology of Seymour Island to
1984 REVIEW
019
a
Figure 3. Closeup view of some of the fossil Lyreidus antarcticus collected from the site of its greatest abundance, locality 6.
the interpretation of the Cenozoic history of the southern hemisphere. This research was supported by National Science Foundation grant DPP 82-13985 to William J. Zinsmeister. Other members of the research team were Frederick Barbis, Judd Case, Dan Chaney, Sankar Chatterjee, Brian Huber, Carlos Macellari, Michael Nickel, James Robinson, Peter Sadler, Brian Small, Michael Woodburne, and William Zinsmeister.
References Ball, H.W. 1960. Upper Cretaceous Decapoda and Serpulidae from James Ross Island, Graham Land. Falkland Islands Dependencies Survey Scientific Reports, 24, 1-30. Feldmann, R.M., and W.J. Zinsmeister. 1983. New crabs from the La Meseta Formation (Eocene) of Antarctica: Biogeography and paleoecology. Geological Society of America Abstracts with program, 15(6), 571. Feldmann, R.M., and W.J. Zinsmeister. 1984. New fossil crabs (decapoda: brachyura) from the La Meseta Formation (Eocene) of Antarctica: Paleogeographic and biogeographic implications. Journal of Paleontology, 58(4), 1046-1061. Taylor, B.J. 1979. Macrurous decapoda from the Lower Cretaceous of southeastern Alexander Island. British Antarctic Survey Scientific Reports, 81, 1-39. Valle, R.A. del, and C.A. Rinaldi, 1975. Additions to the presence of Hoploparia stokesi (Weller) in the "Snow Hill Island Series," on Vicecomodoro Marambio Island, Antarctica. Contribucion del Inst it uto Antartica Argentino, 190, 1-21. (In Spanish.) Zinsmeister, W.J., and R.M. Feldmann. 1984. Cenozoic high latitude heterochroneity of Southern Hemisphere marine faunas. Science, 224(4646), 281-283.
