Late Cretaceous and Paleocene Decapod Crustaceans from James Ross Basin, Antarctic Peninsula

45 Pages·2008·5.05 MB·English

Paleontological Society
Late Cretaceous and Paleocene Decapod Crustaceans from James Ross Basin, Antarctic
Peninsula
Author(s): Rodney M. Feldmann, Dale M. Tshudy, Michael R. A. Thomson
Source: Memoir (The Paleontological Society), Vol. 28, Supplement to Vol. 67, no. 1 of the
Journal of Paleontology (Jan., 1993), pp. 1-41
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/1315582
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The Paleontological Society
MEMOIR 28
LATE CRETACEOUS AND PALTEOCENED ECAPOD CRUSTACEANS FROM
JAMES ROSS BASIN, ANTARCTIC PENINSULA
1RODNEY M. FELDMANN, 1DALE M. TSHUDY, AND 2MICHAEL R. A. THOMSON
'Department of Geology, Kent State University, Kent, Ohio 44242 U.S.A. and
2British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, United Kingdom
Copyright ? 1993 by
THE PALEONTOLOGICAL SOCIETY, INC.
JANUARY 1993
CONTENTS GENUSR etrorsichela n. gen .................... 27
Retrorsichela laevis n. sp .................... 27
AB STRACT ................................................ 1 INFRAORDEBRr achyura Latreille, 1803 ................ 29
INTRODUCTION... ......................................... 1 SECTIONP odotremata Guinot, 1977 ................. 29
STRATIGRAPHSIECT TING ................................... 1 SUBSECTIODNr omiacea de Haan, 1833 ............ 29
GE NE RAL ............................................... 1 SUPERFAMILDYr omioidea de Haan, 1833 ........ 29
SANTAM ARTAF ORMATION.. ............................. 3 FAMILYP rosopidae von Meyer, 1860 ......... 29
LOPEZ DE BERTODANO FORMATION ........................ 3 SUBFAMILPYi thonotinae Glaessner, 1933 .... 29
SOBRALF ORMATION. .................................... 5 GENUSP lagiophthalmous Bell, 1863 ...... 29
CAPEM ELVILLFEO RMATION. ............................. 5 Plagiophthalmous collinsi n. sp ........ 29
TAPHONOYM .............................................. 5 SUBSECTIOANr chaeobrachyura Guinot, 1977 ....... 30
COLLECTINLGO CALITIES... ................................. 6 SUPERFAMILHYo moloidea de Haan, 1839 ....... 30
DEPOSITORIES ............................................. 6 FAMILYP oupiniidae Guinot, 1991 ............ 30
SYSTEMATIC PALEONTOLOGY ................................ 7 GENUSR hinopoupinia n. gen .............. 30
ORDERD ecapoda Latreille, 1803 ......................... 7 Rhinopoupinia bicornis n. sp. ............. 30
SUBORDERPl eocyemata Burkenroad, 1963 ............... 7 SUPERFAMILRYa ninoidea de Haan, 1841 .......... 31
INFRAORDEARs tacidea Latreille, 1803 ................. 7 FAMILYR aninidae de Haan, 1841 .............. 31
FAMILYN ephropidae Dana, 1852 ................... 7 GENUSC ristafrons n. gen .................... 31
SUBFAMILHYo marinae Huxley, 1879 .............. 7 Cristafrons praescientis n. sp. ............... 33
GENUSH oploparia McCoy, 1849 ............... 7 SUPERFAMILTYy moloidea Alcock, 1896 ........... 34
Hoploparia stokesi (Weller, 1903) ............. 7 FAMILYT orynommidae Glaessner, 1980 ......... 34
Hoploparia antarctica Wilckens, 1907 ......... 12 GENUST orynomma Woods, 1953 ............ 34
GENUSM etanephrops Jenkins, 1972 ............. 16 SUBGENUST orynomma (Torynomma) Woods,
19 53 .................................. 34
Metanephropsjenkinsi Feldmann, 1989 ....... 16
Metanephrops rossensis n. sp ................ 16 Torynomma (Torynomma) australis n. sp. 34
INFRAORDERP alinura Latreille, 1803 .................. 19 SECTIONH eterotremata Guinot, 1977 ............... 35
SUPERFAMILYG lypheoidea Winckler, 1883 .......... 19 SUPERFAMILCYa lappoidea de Haan, 1833 ......... 35
FAMILYG lypheidae Winckler, 1883 ............... 19 FAMILYC alappidae de Haan, 1833 .............. 35
GENUSG lyphea von Meyer, 1835 ............... 19 GENUSN ecrocarcinus Bell, 1863 .............. 35
Glyphea australensis n. sp ................... 19 Necrocarcinus wrighti n. sp ................ 35
FAMILYM ecochiridae van Straelen, 1925 .......... 22 Necrocarcinus carinatus n. sp ............ 36
GENUSM eyeria McCoy, 1849 .................. 22 SUMMARYA NDC ONCLUSIONS.. ............................. 37
Meyeria crofti Ball, 1960 ..................... 22 ACKNOWLEDGMENTS ....................................... 38
REFERENCES.. ............................................ 38
SUPERFAMILPYa linuroidea Latreille, 1803 ........... 22
FAMILYP alinuridae Latreille, 1802 ................ 22 A PPEN D IX ................................................ 40
GENUSL inuparus White, 1847 ................. 22
ILLUSTRATIONS
Linuparus macellarii Tshudy and Feldmann,
19 8 8 .................................... 22 FIGURES
INFRAORDEARn omura H. Milne Edwards, 1832 ........ 24 1 -Maps of the James Ross Island area showing the
SUPERFAMILTYh alassinoidea Latreille, 1831 ......... 24 distribution of stratigraphic units discussed in the text and
FAMILYC allianassidae Dana, 1852 ................ 24 the locations from which new occurrences of decapod
fossils are described .................................. 2
GENUSC allianassa Leach, 1814 ................ 24
2-Stratigraphic sections from selected sites in the James Ross
Callianassa cf. C. meridionalis Ball, 1960 ..... 24 Island area showing the positions from which decapod
SUPERFAMILPYa guroidea Latreille, 1803 ............. 24 fossil collections were made ........................... 4
FAMILYP aguridae Latreille, 1802 ................. 24 3- Hoploparia stokesi (W eller) ............................ 9
GENUSP aguristes Dana, 1851 .................. 24 4-Hoploparia stokesi (W eller) ............................ 10
5--Hoploparia stokesi (W eller) ............................ 11
Paguristes santamartaensis n. sp ............. 24 6-Summary of stratigraphic changes in the morphology of
SUPERFAMILGYa latheoidea Samouelle, 1819 ......... 25 Hoploparia stokesi (Weller) and interpreted bathymetric
FAMILYG alatheidae Samouelle, 1819 ............. 25 framework for each unit ............................... 12
SUBFAMILMY unidopsinae Ortmann, 1898 ....... 25 7--Hoploparia antarctica Wilckens ........................ 14
GENUSM unidopsis Whiteaves, 1874 .......... 25 8-Hoploparia antarctica Wilckens ........................ 15
9-Metanephrops rossensis n. sp .......................... 18
Munidopsisfoersteri n. sp ................. 25
10--Metanephrops rossensis n. sp .......................... 19
SUPERFAMIL?YG alatheoidea Samouelle, 1819 ........ 27 11 -Metanephrops rossensis n. sp .......................... 19
FAMILYR etrorsichelidae n. fam .................. 27 12--Glyphea australensis n. sp ............................. 20
13-Line drawing of Glyphea australensis n. sp. showing the 27-Holotype of Torynomma (Torynomma) australis n. sp. ... 34
positions and orientations of measurements recorded in 28-Line drawing of Torynomma (Torynomma) australis n. sp.,
T ab le 3 .............................................. 21 showing the measurements taken, in mm ............... 35
14-Linuparus macellarii Tshudy and Feldmann ............. 23 29-Necrocarcinus spp .................................... 36
15--Callianassa cf. C. meridionalisB all .................... 24 30-Line drawing of Necrocarcinus wrighti n. sp., showing the
16-Paguristes santamartaensisn . sp ....................... 25 position and orientation of measurements taken on both
17-Munidopsis foersterin . sp ............................. 26 species of Necrocarcinus ............................... 37
18-Line drawing of Munidopsisfoersteri showing the
measurements taken, in mm ........................... 26 TABLES
19-Retrorsichela laevis n. gen. and sp ..................... 28
1- Measurements (in mm) taken on specimens of Hoploparia
20-Line drawing of the carapace of Retrorsichela laevis n. gen.
antarctica W ilckens ................................... 15
and sp., showing pattern of grooves described in text .....
21 -Holotype of Plagiophthalmous collinsi n. sp ............ 2 2-Measurements (in mm) taken on specimens of
Metanephropsr ossensisn . sp ......................... 17
22-Line drawing of Plagiophthalmous collinsi n. sp., showing
the measurements made, in mm ....................... 3 3-Measurements (in mm) taken on specimens of Glyphea
australensisn . sp. .................................. 21
23-Dorsal and left lateral view of the carapace of the holotype
4--Measurements (in mm) taken on specimens of Retrorsichela
of Rhinopoupinia bicornis n. sp ........................
laevis n. gen. and sp. ................................ 27
24-Line drawing of Rhinopoupinia bicornis n. sp., showing the
m easurem ents m ade .................................. 31 5-Measurements (in mm) taken on specimens of Cristafrons
25- Cristafronsp raescientisn . gen. and sp .................. 3praescientis n. sp. . ................................... 33
6-Measurements (in mm) taken on specimens of
26--Line drawing of the carapace of Cristafrons praescientis n.
Necrocarcinus wrighti n. sp. .......................... 37
gen. and sp., showing the position and orientation of
m easurem ents taken .................................. 33
Copyright ? 1993, The Paleontological Society
LATE CRETACEOUS AND PALEOCENED ECAPOD CRUSTACEANS
FROM JAMES ROSS BASIN, ANTARCTIC PENINSULA
RODNEY M. FELDMANN,' DALE M. TSHUDY,' AND MICHAEL R. A. THOMSON2
'Departmento f Geology, Kent State University, Kent, Ohio 44242 U.S.A. and
2BritishA ntarcticS urvey, High Cross, MadingleyR oad, CambridgeC B3 OETU nited Kingdom
ABSTRATr-Seventeesnp ecies of decapod crustaceansh ave been describedf rom Campaniant hroughP aleocener ocks in the Santa
Marta,L 6pezd e Benodano, and SobralF ormationso f the JamesR oss Basin,A ntarcticaO. f these,n ine aren ew species:M etanephrops
rossensis, Glypheaa ustralensis,P aguristess antamartaensis,M unidopsisf oersteri, Retrorsichelal aevis, Plagiophthalmousc ollinsi,
Rhinopoupiniab icornis,C ristafronsp raescientis,a nd Torynomma( Torynomma)a ustralis.O ne new family, Retrorsichelidaea, nd
three new genera, Retrorsichela,R hinopoupinia,a nd Cristafrons,w ere also named. This assemblagei ncludes the first notice of
brachyuransf rom the Cretaceouso f Antarctica;s ix species are described.T he nephropidl obster Hoploparias tokesi (Weller),t he
most common decapod throughoutt he section, exhibits significantm orphologicalc hanget hroughouti ts rangef rom late Santonian
or earliest Campanian to Paleocene; however, variation of key features is asynchronous.T he raninid brachyuran,C ristafrons
praescientis,i s second in abundancet o H. stokesi. The occurrenceo f Metanephropsr ossensisa nd Munidopsisf oersteri represents
the oldest geological records for these genera and the recognitiono f species of Paguristes,P lagiophthalmous,T orynomma,a nd
Necrocarcinusc onstitutes the first notice of these genera in Antarctica.O f those taxa that have living congenors, the species of
MetanephropsL, inuparusa, nd Munidopsiso ccupiedh abitatsa t inner shelf depthsi n the Cretaceousw hereast heire xtantd escendants
are restrictedt o outer shelf and bathyal depths. This diverse decapod fauna is dominated by generat hat rangei nto the Cenozoic
and appearst o be a pioneer assemblage.
INTRODUCTION collections of decapods were made in the course of studies by
THE CRETACEOUaSn d Paleogene rocks of the James Ross Basin, E. Olivero and material that he collected has been made available
situated on the eastern margin of the Antarctic Peninsula, for the present work.
have yielded some of the most diverse and well-preserved In the austral summers of 1985/1986 and 1987/1988, field
assemblages of fossils from anywhere in Antarctica. work conducted under the auspices ofthe British Antarctic Survey
Representatives of nearly every phylum of organisms known examined the stratigraphic sequence ranging from Santonian
from the fossil record have been identified from the area. Among through Campanian on western James Ross and Vega Islands
these groups, the decapod crustaceans are unusually diverse. as well as conducted reconnaissance collecting on Seymour,
The first record of a decapod crustacean from the James Ross Humps, and Cockburn Islands. It is the material collected as a
Basin was that of Hoploparia stokesi (Weller, 1903), which may result of this work that forms the primary basis for this study.
have been the first species of fossil described from specimens The purpose of this work is to describe the systematic
collected in Antarctica. Subsequently, several investigators have paleontology of several newly discovered decapod taxa from the
reported upon decapod occurrences within the area. The field James Ross Basin area as well as to provide new information
work of W. N. Croft and R. Stoneley resulted in collections of regarding the paleobiology of previously known forms. In so
decapods studied by Ball (1960). He described the details of doing, the study provides a comprehensive treatment of the
Hoploparia stokesi and added two additional species, Callianassa previously undescribed decapods from the James Ross Basin
meridionalis Ball and Meyeria crofti Ball, to the list of species area and a summary of information regarding previously
known from the region. Subsequently, del Valle and Rinaldi described taxa.
(1975) recognized the presence of Hoploparia stokesi on Seymour Most of the specimens forming the basis of the this work were
Island. collected from the Santa Marta Formation at localities in
Within the past decade, numerous works have been devoted northwestern James Ross Island and from the Cape Lamb
to the decapods of this region. Five species of macrurans, three Member (Crame et al., 1991) of the L6pez de Bertodano
species of anomurans, and seven species of brachyurans have Formation near Cape Lamb, southwestern Vega Island (Figure
been described (Feldmann and Zinsmeister, 1984; Feldmann 1). Additional specimens were collected from Humps, Cockburn,
and Wilson, 1988; Tshudy and Feldmann, 1988; Aguirre-Urreta, and Seymour Islands. Because the details of stratigraphy and
1989; Feldmann, 1989, 1992; Aguirre-Urreta et al., 1990) correlation have been treated recently (Pirrie et al., 1991; Crame
(Appendix). These studies documented a rich and abundant et al., 1991), only a summary of relevant details will be given
brachyuran fauna in the Eocene La Meseta Formation on herein. The stratigraphic and geographic positions of sites from
Seymour Island, providing a foundation for the conclusion that which decapods were collected will be based largely upon their
the Antarctic was the site of origin of several taxa whose work.
descendants currently inhabit lower latitude, deeper water
settings. In addition, a macruran fauna, consisting of three species, STRATIGRAPHIC SETTING
was described from the Cretaceous and Paleocene rocks of the General. -The James Ross Basin evolved during late Mesozoic
Lopez de Bertodano Formation on Seymour, Vega, and Snow and early Cenozoic time as a back-arc basin produced during
Hill Islands. One of the species, Hoploparia stokesi, was the eastward to southeastward subduction of proto-Pacific
demonstrated to be one of the most abundant and widely oceanic crust beneath the Antarctic Plate. From the Late Jurassic
distributed taxa within the area (Feldmann and Tshudy, 1989). through the Eocene, the basin filled with sediments shed from
Much of this recent work has been concentrated on an active magmatic arc at the "northern" end of the Antarctic
Maastrichtian through Eocene rocks on Seymour Island, although Peninsula to the northwest (Elliot, 1988). Throughout this history,
it has long been known that Campanian and possibly Santonian Antarctica was situated in a polar position and the James Ross
rocks of James Ross Island contain decapods. Ball (1960) reported Basin would have been at a latitude similar to the present-day
on the occurrence of decapods from these older rocks. Important 64?S.
1
2 RODNEY M. FELDMANN ET AL.
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DECAPOD CRUSTACEANS FROM ANTARCTICA 3
The total exposed basin-fill, totaling approximately 6,000 m one anomuran, a callianassid, and four brachyurans (true crabs)
of sediment, dominantly sandstones and siltstones, has been have been identified. The unit is best exposed on the northwestern
formally divided into the Kimmeridgian-Tithonian portion of James Ross Island, "between Abernethy Flats and
Nordenskjold Formation, and the overlying Gustav, Marambio, the north-western face of Lachman Crags," and "at Hidden
and Seymour Island Groups. The Nordenskjold Formation was Lake, and possibly at Seacatch Nunataks, James Ross Island"
deposited in an anoxic marine basin (Aguirre-Urreta et al., 1990, (Crame et al., 1991, p. 1131). The lower 500 m of the unit
citing Farquhharson, 1982, 1983, and del Valle et al., 1988). consists mostly of"massive, friable sandstones, silty sandstones
The Gustav Group, of approximately Barremian to Santonian and siltstones" but with some finer and coarser beds. The upper
age, was deposited in a submarine fan slope complex (Ineson, 350 m consists of conglomerates and sandstones. The unit is
1989, in Pirrie et al., 1991, p. 229) and crops out along the interpreted as having been deposited below storm-wave base in
northwestern coast of James Ross Island. The Marambio Group, mid to outer shelf depths (Crame et al., 1991, p. 1129). Age of
of approximately Santonian to Paleocene age (Pirrie et al., 1991, the Lachman Crags Member is given by Crame et al. (1991, fig.
p. 229), crops out in several localities which, together, span 2) as ?late Santonian to middle Campanian.
nearly the entire width of the basin. The group is divided into The Herbert Sound Member embraces 250 m of sediment
the Santa Marta, Lopez de Bertodano, and Sobral Formations. overlying the Santa Marta Formation. The Herbert Sound
The Seymour Island Group, of Paleocene to Eocene age, is Member has yielded a very diverse decapod assemblage,
exposed only on eastern Seymour Island, and is subdivided into including three astacids, two palinurids, three anomurans, and
the Cross Valley and La Meseta Formations. four brachyurans. On James Ross Island, the unit is best exposed
Only one decapod, an allochthonous crab from the in the region of St. Martha Cove but also crops out on the
Nordenskjold Formation (Aguirre-Urreta et al., 1990), is known northwest shore of Croft Bay, Cape Lamb on Vega Island, and
from pre-Upper Cretaceous strata within the basin, but decapods possibly also on Humps Island (Crame et al., 1991, p. 1131).
are diverse, abundant, and often well preserved in the Marambio The Herbert Sound Member consists of "well-sorted, fine-grained
and Seymour Island Groups. The decapod-rich Marambio and quartzose sandstones, interbedded with minor cross-bedded
Seymour Island Groups together record an overall transgressive, sandstones, shell coquinas, and rarer finer-grained beds" (Pirrie,
basin-filling sequence. 1989, 1990 in Crame et al., 1991, p. 1131). Based on hummocky
The stratigraphy of the Marambio Group is currently in a cross-bedding and thicker shelled bivalves, this member is
very dynamic state. Revisions have been frequent and they interpreted by Pirrie to have been deposited above storm wave
continue. In the most recent revision of the basin's Campanian- base, probably at inner shelf depths. Age of the Herbert Sound
Maastrichtian strata, Crame et al. (1991) discussed what is the Member is given by Crame et al. (1991, fig. 2) as early late
biggest impediment to more interpretive work on the decapods, Campanian. Pirrie and Riding (1988 in Crame et al., 1991)
that being the confident correlation of isolated exposures currently suggested that some beds on Humps Island may represent the
referred to the L6pez de Bertodano Formation. The reader is outer shelf equivalent to the inner shelf deposits of the Herbert
referred to Crame et al. (1991), and also Pirrie et al. (1991), for Sound Member.
detailed reviews of the problem. The stratigraphic section and L6pez de Bertodano Formation.--The Lopez de Bertodano
correlations accepted herein are given in Figure 2. Formation crops out at several localities in the James Ross
The Paleocene through Eocene strata of the Seymour Island Basin, but is exposed in greatest thickness on Seymour Island,
Group are known only from Seymour Island and are, therefore, the easternmost exposure of the formation. The mollusks indicate
without the controversies of correlation that surround the a late Campanian-Paleocene age for the L6pez de Bertodano
underlying Marambio Group. The ages and environments of Formation on Seymour Island, but dinoflagellates suggest that
deposition of these units also seem better understood. the lower portion of the formation is slightly older, probably
Santa Marta Formation. -The Santa Marta Formation is best Santonian (Crame et al., 1991).
exposed on James Ross Island at St. Martha Cove, but also The westernmost exposure of the Lopez de Bertodano
crops out on the island along the northwest shore of Croft Bay, Formation occurs on Cape Lamb on Vega Island, where a 480-m
as well as at Cape Lamb on Vega Island and on Humps Island section has recently been studied in detail by Pirrie et al. (1991).
(Crame et al., 1991). This formation consists mostly of"massive, Between Cape Lamb and Seymour Island, the L6pez de
very fine- to medium-grained sandstones and silty sandstones" Bertodano Formation crops out at The Naze on James Ross
but includes coarser beds in its lower part (Crame et al., 1991, Island, Humps Island, at False Island Point on Vega Island,
p. 1130). Ammonites indicate an early-late Campanian age Snow Hill Island, and Cockbur Island. Decapods were collected
(Crame et al., 1991, p. 1133, citing Olivero, 1984, and Olivero at all these exposures.
et al., 1986) for the Santa Marta Formation, but some mollusks The precise stratigraphic relationship of these exposures is
and dinoflagellates suggest that the lower portion of the formation uncertain. Part of the problem has been that these localities lie
may be as old as Santonian (Crame et al., 1991, p. 1133). in a proximal-distal transect across the basin, so that beds on
The Santa Marta Formation is currently subdivided into three Cape Lamb represent the most proximal deposits of the
members: the Lachman Crags Member, Herbert Sound Member, formation, and those on Seymour Island the most distal. It is
and Rabot Member. The former two each contain several uncertain which of the biotic differences between the isolated
decapod taxa; the Rabot has yielded none. exposures are age-related and which are due to facies differences.
The Lachman Crags Member comprises the lower 850 m of The most recent, albeit tentative, judgment regarding the
the Santa Marta Formation, and has yielded a diverse decapod relationship between the Cape Lamb beds and the Seymour
fauna. One astacid (true lobster), two palinurids (spiny lobsters), Island beds is that of Crame et al. (1991), who correlated the
FIGURE I-Maps of the James Ross Island area showing the distribution of stratigraphic units discussed in the text and the locations from which
new occurrences of decapod fossils are described. Locality numbers are keyed to locality descriptions given in the text and to the stratigraphic
sections shown in Figure 2. (Geologic map details from Crame, Pirrie, Riding, and Thomson, 1991.)
4 RODNEY M. FELDMANN ET AL.
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FIGURE 2-Stratigraphic sections from selected sites in the James Ross Island area showing the positions from which decapod fossil collections
were made. Memberso f the Santa MartaF ormation,t he LachmanC ragsa nd HerbertS ound, are identifiedi n the northernJ ames Ross Island
section. The diagonallyl ined portion of that section denotes scatterede xposuresw ithin the LachmanC ragsM emberw hose precises tratigraphic
position is questionable.M emberso f the Lopez de BertodanoF ormation,C ape Lamb and SandwichB luff, are identifiedi n the Cape Lamb
section. The member status of exposureso f the L6pez de BertodanoF ormationa t False Island Point, The Naze, Humps Island, Snow Hill
Island, and Cockbum Island has not been established.( Modifiedf rom Cramee t al., 1991.)
Cape Lamb beds with the middle portion of the Lopez de intervening exposures of the Lopez de Bertodano Formation,
Bertodano Formation on Seymour Island. They suggested that except for some of the latter on Snow Hill Island, within the
faunal differences between the two sections are due to proximal- Cape Lamb Member.
distal facies changes across the basin. The same authors included To date, the L6pez de Bertodano Formation has yielded eight
DECAPOD CR USTA CEANS FROM ANTARCTICA 5
decapod species, including two astacids, three palinurids, and Rotularia Units was probably deeper than interpreted by
three brachyurans. The Cape Lamb Member and Seymour Island Macellari (1988), who considered these to be very shallow marine
beds contain five and four species, respectively. The astacid deposits. The lower Cape Lamb Member is interpreted as outer
Hoploparia stokesi is found throughout the formation. shelf deposition, which may require an even deeper setting for
The L6pez de Bertodano Formation on Seymour Island was the more distal Seymour Island beds. Such varying interpretations
interpreted by Macellari (1988) as a transgressive-regressive of key stratigraphic sections underscore the need for more
sequence. Macellari recognized 10 informal units in the 1,190-m stratigraphic work.
sequence, referring to the lower six as Rotularia Units and the Member C of the Cape Lamb section of Pirrie et al. (1991)
upper four as Molluscan Units. The Rotularia Units exhibit a was formalized as the Sandwich Bluff Member by Crame et al.
low-diversity macrofauna that includes no decapods, whereas (1991). This member was considered to be late Maastrichtian
the Molluscan Units contain a rich and abundant macrofauna, (Pirrie et al., 1991), as are some of the Molluscan Units on
including several decapod taxa. Seymour Island, but the Sandwich Bluff Member is considered
Macellari suggested that the Rotularia Units, which "form a to have direct physical equivalents on Seymour Island (Crame
distinctive lithologic sequence composed of friable silty mudstone et al., 1991, p. 20).
and sandy siltstone predominantly gray in color, usually strongly Sobral Formation. -The Paleocene Sobral Formation lies
bioturbated, and interbedded with fine-grained gray sandstone" unconformably upon the L6pez de Bertodano Formation on
(1988, p. 28), were deposited in a "very shallow delta/estuary- Seymour Island (Macellari, 1988). This formation, 255 m thick,
influenced environment" (1988, p. 50), and that the low consists of "maroon, well-laminated silts at the base, followed
macrofaunal diversity, especially in Units 1-4, may have been by cleaner sandstones that become more glauconitic and cross-
due to low salinity or high turbidity. Fossil evidence, including bedded toward the top" (Macellari, 1988, p. 25). Macellari (1988,
unbored fossil wood and, in Units 5 and 6, common mosasaur p. 25) interpreted the Sobral Formation as the "filling of the
remains, supports deposition near a delta or estuary (1988, p. basin by the progradation of a delta system." The unit is not as
49). There is, however, conflicting evidence for deposition in fossiliferous as the underlying molluscan units of the Lopez de
fully marine conditions. Macellari noted that 180 values for Bertodano Formation, but yielded two astacid lobster species,
benthic foraminifera did not reflect fluctuations in salinity (E. Hoploparia stokesi and Metanephrops jenkinsi.
Barrera, personal commun., 1986 in Macellari, 1988, p. 48). Cape Melville Formation.--The Cape Melville Formation
Similarly, Huber (1988, p. 169) stated that foraminiferal stable crops out on King George Island and has been assigned a Miocene
isotope data and foraminiferal and siliceous (Harwood, 1988) age (Gazdzicki, 1987). Although this unit is exposed well beyond
microfossil distributions indicated that normal marine conditions the geographic bounds of this study, two hermit crab claws were
persisted during deposition of Seymour Island beds from at least collected from the Cape Melville Formation that are thought to
above 200 m through to the K/T boundary. Elliot (1988, p. 550) be conspecific with claws collected in the Santa Marta Formation.
concluded that "on balance, a shelf environment below storm The Cape Melville Formation is a sequence of glacio-marine
wave base and with turbid waters seems most likely." sediments known to contain fossils derived from older rock units
The Molluscan Units on Seymour Island consist of"generally in the peninsular region (see, for example, Birkenmajer et al.,
monotonous, sandy siltstone" deposited in deeper, open marine 1987).
conditions. Units 7 and 8 were deposited in middle shelf depths,
whereas Unit 9 represents outer shelf deposition and maximum TAPHONOMY
transgression for the formation. Unit 10 was interpreted as The general quality of preservation of fossil decapod material
representing middle to inner shelf deposition (Macellari, 1988, in the James Ross Basin is excellent. Cuticle is often preserved
p. 50). in fine enough detail that ultrastructure can be examined
At its type locality on Vega Island, the Cape Lamb Member (Feldmann and Tshudy, 1987). In general, damage to the cuticle
of the Lopez de Bertodano Formation rests conformably upon has occurred as a result of exposure at the surface rather than
the Herbert Sound Member of the Santa Marta Formation. during the degradational period surrounding the death,
Pirrie et al. (1991, p. 252) interpreted these deposits as dismemberment, and burial of the organisms.
representing deposition in outer to mid-?inner shelf depths. They With the exception of the specimens of Retrorsichela laevis
also stated that Member A and part of Member B of the Cape n. sp., all decapod fossils described from Late Cretaceous and
Lamb section may be equivalent to the Rotularia Units on Paleocene rocks of the James Ross Basin were preserved within
Seymour Island. Units A and B were subsequently combined ovoid to spherical calcareous concretions. As noted previously
into a formal unit by Crame et al. (1991) as the Cape Lamb (Feldmann, 1989), the dimensions of the concretions seldom
Member of the L6pez de Bertodano Formation. Their correlation exceed twice the greatest length of the enclosed specimen. The
diagram (Pirrie et al., 1991, fig. 9) suggests a correlation of what formation of the enclosing concretions would appear to be related
is now the Cape Lamb Member to units as high as Unit 8; 7 to burial and diagenetic processes, perhaps induced by the
and 8 are Molluscan Units. The tentative correlation is based decomposition of the decapod remains, rather than as fillings
mainly on ammonites and dinoflagellates. Firm correlations are of burrow structures. There has been no observation of structures
not possible at this time as correlations based on the ammonite surrounding the fossils that would suggest burrow fillings.
Gunnarites do not agree with those based on other ammonites. Burial of the decapod remains, and concretion formation,
It is possible that this discrepancy is due to facies differences probably occurred rapidly. Tshudy et al. (1989) suggested the
(Crame et al., 1991). importance of cephalopods and other organisms as scavenging
Crame et al. (1991) supported a slightly different correlation agents on decapods and concluded that fossils of these organisms
between the Cape Lamb Member and the beds on Seymour would form only under circumstances of extremely rapid burial.
Island. Their correlation (Crame et al., 1991, fig. 2) diagram This interpretation is supported by observations of specimens
indicated that the Cape Lamb Member is equivalent to Seymour examined in this study. In fact, the preservation of Callianassa
Island Units 4 or 5 through 7. cf. C. meridionalis Ball provides an independent indication of
Based upon their tentative correlation of the lower Cape Lamb timing of burial and concretion formation. Three specimens
Member to Rotularia Units on Seymour Island, Pirrie et al. referred to this species are preserved as entire specimens. This
(1991) suggested that the environment of deposition of the is a very rare occurrence in species of Callianassa because the
6 RODNEY M. FELDMANN ET AL.
cuticle of all but the claws and pereiopods tends to be extremely collectionsf rom isolated exposures,l argelyc overed in morainicd ebris;
thin and uncalcified. It is highly unlikely that these specimens LachmanC ragsM ember,S anta MartaF ormation;p ossible correlation
would have been preserved in this fashion unless burial had with the conglomeratel evels at the top of locality.
been nearly instantaneous. 9. West side of San Jose Pass: 63?53.0'S, 57?56.0'Wt o 63?64.0'S,
Retrorsichela laevis is preserved typically as entire individuals 57?55.0'W;r oughs tratigraphicasle ction over poorly exposed sequence
in the NW-SE trendingv alley on the westerns ide of San Jose Pass and
within a calcareously cemented conglomerate. The specimens off the southerne nd of LachmanC rags;L achmanC ragsM ember,S anta
are not surrounded by concretionary structures. Although no MartaF ormation.S ample locality:D .8623
field observations were made regarding the orientation of the 10. WesternS anJ oseP ass:6 3?54.5'S5, 7?49.0'Ws;t ratigraphicasel ction
specimens within the rock unit, it is possible that the specimens in the upper part of the valley on the western side of San Jose Pass;
were preserved in living position. This tentative conclusion is upper part of LachmanC ragsM ember,S anta MartaF ormation.
based upon the observation that, of the specimens that are 11. Western margin of Abernethy Flats: 63?53.4'S, 57?58.5'W to
complete and that appear to represent corpses, all exhibit the 63?53.3'S, 57?58'W;s tratigraphicasl ection in poorly exposed ground
same posture. The claws are carried in a characteristic "preying and in section in ridgeso bliquet o strikei n the aread ue south of Brandy
mantis" position beneath the carapace. Although this posture Bay; lower part of LachmanC rags member, Santa MartaF ormation.
Sample locality:D .8630
could result from rigor mortis, the presence of several specimens 12. Southwesternm argino f AbernethyF lats: 63?53.3'S,5 7058'Wt o
in the same position would seem to make that possibility unlikely. 63?54.5'S,5 7058'W;d etaileds tratigraphicasle ction continuingu pwards
However, because the organisms lived as burrowing organisms from the top of section at locality 11. The section repeats the beds
in a very coarse sediment, there is no way to identify burrow studieda t localities6 , 7, and 10; upperp arto f LachmanC ragsM ember,
structures. Santa MartaF ormation.S ample locality:D .8629
Decapod fossils are preserved both as corpses and as exuviae 13. West side of Leal Bluff, Cape Lamb, Vega Island: 63?52.7'S,
(Feldmann and Tshudy, 1987; Feldmann, 1989). Distinction 57?36'W;s pot collections from the slopes on the western side of Leal
between these two preservational styles is based upon Bluff;C ape Lamb Member, L6pez de BertodanoF ormation. Sample
observations on entire specimens. The separation of the carapace locality:D .8641
14.E asts ide of LealB luff,C apeL amb,V egaI sland:6 3?53.4'S5, 7?35'W;
from the abdomen and preservation in Salter's position in the spot collections from numerouss catteredc oncretionsw eatheredo ut of
macrurans is taken to indicate that the specimen was a molt. poorly lithified sandstones; slopes south of Leal Bluff; Cape Lamb
Recognition of molting in brachyurans and anomurans may be Member, L6pez de BertodanoF ormation. Sample localities: D.8644
more difficult as the carapace may return to its original position and 8645, DJ.230, 231
following molting. A molted skeleton may be positioned exactly 15. Col between Dagger Peak and Comb Ridge, The Naze, James
as in life. Displacement of the carapace, relative to the rest of Ross Island:6 3055'S, 57028.2'Wc; ollectionf rom concretionsw eathered
the skeleton, is the criterion used to recognize molting. out of poorly lithifieds andstoneb eds exposed on the easterns ide of the
col; Cape Lamb Member, L6pez de Bertodano Formation. Sample
localities:D .8643, DJ.355
COLLECTINGL OCALITIES 16. North side of FortressH ill, the Naze, James Ross Island:6 3?56'S,
Throughout the following pages, collection sites will be referred 57?31'W ;s potc ollectionf romp oorlye xposeds andstonesw ithc oncretions
to by numbers. The complete description of these collecting on the NW slope of the hill in an area largelyc overed with debrisf rom
localities is given below. The sites are plotted on Figure 1. overlying basaltic rocks; Cape Lamb Member, L6pez de Bertodano
Formation.
1. CapeM elville,e asternK ingG eorgeI sland:6 2?01'15"S5, 7?37'30"W; 17. Northwests ide of Humps Island:6 3?59.5'S,5 7'25.5'W;c ollection
western end of the Cape Melville peninsula, on summit of cliffs; of fossils in concretions,l oose on slope extendingd own from the col
reconnaissanceg eology and general fossil collection. Sample locality: between the two peaks; Cape Lamb Member, L6pez de Bertodano
DJ.94 Formation.S ample localities:D J.355 and 368
2. West coast of HerbertS ound: 63?51.2'S,5 7'47.0'W;J ames Ross 18. Westerne nd of Humps Island:6 3'59.5'S, 57'26'W;c ollection of
Island, 8 km south of Cape Lachman;s pot collectionsf rom two small fossilsf roma measureds ectione xtendingf romb eachl evel to just beneath
exposureso f conglomerateo n either side of a small stream;u ppermost a residualv olcanicc ap on the westernmosto f the two peaks;C apeL amb
part of the LachmanC ragsM ember, Santa MartaF ormation. Member,L opez de BertodanoF ormation.
3. North side of CrameC ol: 63?50'S,5 7?53.7'Wr; oughs tratigraphical 19. Eastc oast of CockburnI sland:6 4?12.3'S,5 6?50'Ws; pot collection
section from the top of Hidden Lake Beds to base of the main section in prominent pale-coloredg ully about midway along the coast; Cape
exposed in Crame Col; basal Lachman Crags Member, Santa Marta LambM ember,L 6pezd e BertodanoF ormation.S amplel ocality:D J.351
Formation.S ample locality:D .8612 20. SouthwesternS eymourI sland:6 40?17'58"S5, 6?45'8"Wn;o rth-facing
4. SoutheastB randyB ay: 63'50.3'S, 57?55.5'W;s pot collection from slope along a drainagee xposing unit Klb9 (Sadler, 1988), L6pez de
isolated exposuresa pproximatelyc orrelatedw ith the lower 50 m of the BertodanoF ormation.M aastrichtian.
LachmanC ragsM ember,S anta MartaF ormation.
5. West side of LachmanC rags:6 3?51.0'S,5 7'52'W;m easureds ection, DEPOSITORIES
2.5 km southeasto f CrameC ol; LachmanC ragsM ember,S antaM arta
Formation;c rustaceansw ere collected from reworkedn odules in the Specimens that formed the basis for this work have been
conglomerates.S ample locality:D .8616 deposited in the following collections. The abbreviations denoting
6. EasternA bernethyF lats: 63'52.3'S, 57?54.0'W;m easureds ection those depositories, and used throughout the text, are as follows.
in fine sandstonesa nd conglomerateesx posedo n eithers ide of an isolated BAS. IN., British Antarctic Survey, Invertebrate Type Collection,
and prominent basaltic dike (trend 314?); Lachman Crags Member, British Antarctic Survey, High Cross, Madingley Road,
Santa MartaF ormation.S ample locality:D .8617 Cambridge CB3 OET, United Kingdom. CIRGEO, Centro de
7. SouthwestL achmanC rags:6 3?53.0'S,5 7?54'W;m easureds ection Investigaciones en Recursos Geologicos, Ramirez de Velazco
northwest of a prominent roof-shaped hill extending from the 847, 1414-Buenos Aires, Argentina. CPBA, Catedra de
southwesternc orer of the crags;L achmanC ragsM ember,S antaM arta
Formation;n ear the top of the section, just below the debris-covered Paleontologia, Universidad de Buenos Aires, Ciudad
slopes of the volcanic cap, are threep rominentc onglomerateb eds, rich Universitaria, Pabellon 2, Geologia, 1428-Buenos Aires,
in crustaceanr emains;s pot collectionsw ere also made in conglomerate Argentina. KSU, Kent State University, Department of Geology,
exposuresa bout 309 m below the base of the section. Samplel ocalities: Paleontology Collection, Kent, Ohio, U.S.A. USNM, United
D.8618 and 8621, DJ.377 States National Museum of Natural History, Department of
8. Corrie, southwest Lachman Crags: 63?53.2'S, 57?54.2'W;s pot Paleobiology, Washington, D.C., U.S.A.