References

Harris, T. 1937. The fossil flora of Scoresby Sound east Greenland. Part 5: Stratigraphic relations of the plants beds. Meddelelser om Grenland, 112(2), 1-114. Harris, T. 1964. The Yorkshire Jurassic Flora. H. Caytoniales, cycadales and pteridosperms. London: British Museum (Natural History) London. Kerp, J.H. 1988. Aspects of Permian palaeobotany and palynology: 10. The west and central European species of the genus Autunia Krasser emend. Kerp (Peltaspermaceae) and the form-genus Rhachiphyllum Kerp (callipterid foliage). Review of Palaeobotany and Palynology, 54(2), 249-360. Petriella, B. 1980. Summary of the Corystospermaceae (Corys- tospermales Pteridospermophyta) of Argentina. II. Fertile struc- tures. Ameghiniana, 8(2), 168-180. (In Spanish) Reymanówna, M. 1970. New investigations of the anatomy of Cayto- nia using sectioning and maceration. Palaontologische Abhand- lung-B Paläobotanik, 3(3), 651-655. Taylor, T.N., G.M. Del Fueyo, and E.L. Taylor. 1994. Permineralized Figure 3. Distal end of branch bearing three cupules (arrows). caie seed fern cupules from the Triassic of Antarctica: Implications for = 1 cm). cupule and carpel evolution. America Journal of Botany, 81, 666-677. of these similarities, however, corystosperm cupules Taylor, T.N., and E.L. Taylor. 1988. Late Triassic flora from Mount described to date are all characterized by an elongate Falla, Queen Alexandra Range. Antarctic Journal of the U.S., 23(5), micropylar tube that projects from the cupule and the pres- 2-3. ence of bracts subtending each branch. We are hopeful that Thomas, H.H. 1925. The Caytoniales, a new group of angiospermous an analysis of the cuticle, which is currently being processed, plants from the Jurassic rocks of Yorkshire. Philosophical Transac- tions of the Royal Society of London, 213B(3), 299-363. will provide additional information not only on affinities of Thomas, H.H. 1933. On some pteridosperms plants from the Meso- these cupules but also on the plants that produced them zoic rocks of South Africa. Philosophical Transactions of the Royal based on cuticle similarities with Dicroidium foliage. Society of London, 222B(1), 193-265. This study was supported by National Science Founda- Townrow, J.A. 1960. The Peltaspermaceae, a pteridosperm family of Permian and Triassic age. Palaeontology, 3(2), 333-361. tion grant OPP 91-18314.

A dinosaur assemblage from the Transantarctic Mountains

WILLIAM R. HAMMER, WILLIAM J. HICKERSON, and RICHARD W. SLAUGHTER, Department of Geology, Augustana College, Rock Island, Illinois 61201

he vertebrate assemblage collected during the 1990-1991 terminate at this point may belong to the same skeleton. Taustral summer from Mount Kirkpatrick in the Beardmore Many of these pieces are still in matrix awaiting preparation; Glacier region of the Central Transantarctic Mountains others have been partially prepared. includes 120-140 bones and 16 teeth representing at least six A recent review (Slaughter, Hickerson, and Hammer 1994) different taxa. The specimens are from the upper Falla Forma- of serration densities and patterns of teeth found near gnawed tion and include the partial skull and numerous postcranial elements among the Falla Formation fossils showed that the elements from a crested theropod dinosaur, Cryolophosaurus teeth represented at least two (and possibly three) different elliott (Hammer and Hickerson 1994; see table). Other speci- types of scavenging theropods. In addition to these teeth, five mens in the collection include more fragmentary material isolated teeth appear to be from the Cryolophosaurus skull and from a large plateosaurid prosauropod, at least two different an isolated theropod maxilla with three teeth may belong to scavenging theropods, a (?)dimorphodontid pterosaur, and a another individual of this genus. large tritylodont (table). A partial foot and the distal end of a femur representing a Most of the bones collected belong to a single individual large prosauropod were recovered. The animal has a foot of Cryolophosaurus ellioti (table). A diagnosis of Cry- structure indistinguishable from the two large plateosaurid olophosaurus elliott and a brief consideration of its affinities prosauropods known from more complete specimens, Pla- have been published by Hammer and Hickerson (1994). In teosaurus, from Germany, and Lufengosaurus, from China. addition to the elements referred to this animal in the table, The antarctic prosauropod most likely is closely related to many of the isolated vertebrae and other bones listed as inde- these forms.

ANTARCTIC JOURNAL - REVIEW 1994 31 Fossils collected from the Falla Formation at Mount CALLOVIAN Kirkpatrick I

BATHONIAN 0 Kirkpatrick Intrusive.

Ctyolophosaurus ftJOCIAN Articulated skull with mandibles -z Ilium a U WC lschium AALENL4N a Pubis Cl) ______Femur Articulated tibiotarsus and fibula TOARCIAN 2 articulated metatarsals Tibia fragment Maxilla fragments with teeth PLIENSBACHIAN 4 articulated caudal vertebrae 3 articulated cervical vertebrae with ribs SINEMURIAN 5 teeth

Indeterminate HETFANGIAN Maxilla fragment with 3 teeth theropods 6 additional isolated teeth

Prosauropod Articulated astragalus, 4 metatarsals, and 2 RHAETIAN distal tarsals U Distal end of femur Cl) N0RL.N Pterosaur Humerus IL GJ Ln Tritylodont Upper postcanine tooth CARNIAN Indeterminate 28 isolated vertebrae 2 ribs Comparative age chart showing ranges for plateosaurid 10 limb fragments prosauropods, Bienotheroides "dade" tritylodonts, and dimophodon- Pelvic fragment tid pterosaurs. 6 indeterminant bone pieces Numerous smaller fragmentary bones see figure). Dimorphodontids are also restricted to the Late Triassic and Early Jurassic (figure). Tritylodonts are known The single pterosaur humerus recovered probably belongs from the Late Triassic (Nonian) into at least the Middle Juras- to a dimorphodontid or a related primitive family within the sic, but the other large tritylodonts similar in size and tooth Rhamphorhynchoidea. Other dimorphodontids are known morphology to the antarctic animal are Tritylodon maximus, from the Late Triassic and Early Jurassic of Europe. This bone from the Early Jurassic (Pliensbachian) of Africa, and was one of three isolated elements recovered approximately 20 Bienothero ides, which occurs above the Lufengosaurus beds in meters from the main concentration of fossils. China (Middle Jurassic; see figure). Other related tritylodonts The single postcanine tooth from a large tritylodont indi- within the Bienotheroides "dade" (Sues 1986, pp. 279-284) cates synapsids persisted into the Early Jurassic in the Antarc- range back into the Early Jurassic (Pliensbachian). tic as they did elsewhere. Diverse faunas of Early to Middle Tri- As illustrated in the figure, the overlap of ranges for the assic synapsids have been described from a number of other large plateosaurid prosauropods (Lufengosaurus) and the sites in the Transantarctic Mountains (Hammer and Cosgniff Bienotheroides "dade" would suggest a Pliensbachjan to, per- 1981; Hammer 1990, pp. 42-50). The Mount Kirkpatrick trity- haps, a Toarcian age for the Falla Formation fauna. The lodont is equal in size to the two largest known tritylodonts advanced nature of Ciyolophosaurus compared to Late Trias- from China (Bienotheroides) and South Africa (Tritylodon) sic and earliest Jurassic theropods reinforces this middle-to- (Hammer and Hickerson 1994). late Early Jurassic age. The upper Falla Formation fauna suggests an Early Juras- This research was supported by National Science Founda- sic (Pliensbachian-Toarcian) age. Diabase intrusions into the tion OPP 88-17023 and OPP 91-18620 and by the Augustana upper Falla Formation indicate a minimum age of 177 million Research Foundation. years (early Middle Jurassic; Heimann et al. 1994; see figure). A Dicroidium flora some 300 meters below the bone bed indi- cates a Late Triassic age for the lower Falla Formation. References Prosauropods are known from all of the other continents and are restricted to the Late Triassic and Early Jurassic; however, large plateosaurids most like the antarctic specimen are from Hammer, W.R. 1990. Triassic terrestrial vertebrate faunas of Antarc- tica. In T.N. Taylor and E.L Taylor (Eds.), the Late Triassic (Plateosaurus, Antarctic paleobiology: Keuper Formation, Germany) Its role in the reconstruction of Gondwana. New York: Springer- and earliest Jurassic (Lufengosaurus, Lufeng Formation, China; Verlag.

ANTARCTiC JOURNAL - REVIEW 1994 32 Hammer, W.R., and J.W. Cosgriff. 1981. Myosaurus gracilis, an Slaughter, R.W., W.J. Hickerson, and W.R. Hammer. 1994. Analysis of anomodont reptile from the Lower Triassic of Antarctica and antarctic theropod teeth based on serration densities and pat- South Africa. Journal of Paleontology, 55(2), 410-424. terns. 1994 Geological Society of America North Central Section Hammer, W.R., and W.J. Hickerson. 1994. A crested theropod Annual Meeting Abstracts (Vol. 61). Kalamazoo, Michigan: West- dinosaur from Antarctica. Science, 264, 828-830. ern Michigan University. Heimann, A., T.H. Fleming, D.H. Elliot, and K.A. Foland. 1994. A Sues, H.D. 1986. Relationships and biostratigraphic significance of short interval of Jurassic continental flood basalt volcanism in the Tritylodontidae (Synapsida) from the Kayenta Formation of Antarctica as demonstrated by Ar/Ar geochronology. Earth and northeastern Arizona. In K. Padian (Ed.), The beginning of the age Planetary Science Letters, 111, 1941. of dinosaurs. New York: Cambridge University Press.

Jurassic phreatomagmatic volcanism in the central Transantarctic Mountains RICHARD E. HANSON, Department of Geology, Texas Christian University, Fort Worth, Texas 76129 DAVID H. ELUOT, Department of Geological Sciences and Byrd Polar Research Center, Ohio State University, Columbus, Ohio 43210

he upper part of the Gondwana sequence in the Queen clear evidence for an active volcano-tectonic regime prior to TAlexandra Range, Beardmore Glacier area, central effusion of the Kirkpatrick basalts. Transantarctic Mountains (84°30S 165 0E), records a transi- Individual lahar deposits are massively bedded, very tion from deposition in a retroarc foreland basin in the Trias- poorly sorted, and up to 50 meters thick (figure 1). Coarser sic to explosive basaltic and rhyolitic volcanism in the Jurassic clasts typically are supported in a matrix of basaltic ash and (Barrett, Elliot, and Lindsay 1986, pp. 339-428; Collinson et al. fine lapilli intermixed with large quantities of accidental in press). The explosive volcanism is represented by the upper material. The deposits are intercalated with accretionary part of the Falla Formation, which is probably of Early Juras- lapilli tuffs, which are characteristically developed in moist, sic age, and the overlying Middle Jurassic Prebble Formation. cohesive volcanic ash produced by phreatomagmatic erup- Explosive volcanism was directly followed by quiet effusion of tions. Accretionary lapilli also are common in the matrix of the Middle Jurassic Kirkpatrick tholeiitic flood basalts; both the deposits, and some beds grade directly up into accre- phases of volcanic activity are interpreted to have occurred in tionary lapilli tuff. The latter relation suggests that at least a continental rift environment associated with incipient some of the lahars were produced during eruptive events, stages in Gondwanaland breakup (Elliot 1992, pp. 165-184). rather than resulting from later slumping of unstable, near- Previous work revealed evidence that the explosive volcanism vent tephra accumulations. was phreatomagmatic in nature, involving violent interaction In thin section, characteristics of the basalt shards in the between magma and external water (Larsen 1988; Elliot and matrix of the deposits reveal details of the mechanisms driving Larsen 1993, pp. 397-410). The present research was initiated the explosive eruptions. Many of the basalt shards consist of during the 1990-1991 field season, with the intention of gain- weakly devitrified, clear, pale-brown sideromelane glass, ing further insight into the nature of this phreatomagmatic which is indicative of rapid quenching of basaltic magma in volcanism in relation to tectonic setting. contact with water. Vesicularity of the shards is variable, but The Prebble Formation contains the main record of prox- shard outlines in many cases are controlled by fracture sur- imal explosive basaltic volcanism prior to effusion of the Kirk- faces rather than broken bubble walls, indicating that steam patrick lavas and provides a unique opportunity to examine explosions generated from external water played a major role the events leading up to eruption of a typical continental in magma disruption. Dark brown, turgid, scoriaceous flood-basalt province. The formation, which has a maximum tachylite shards also are present in variable amounts, however, thickness of some 200 meters, consists primarily of coarse- and indicate that some magma batches were subject to less grained basaltic debris-flow deposits (lahars) and is an drastic quenching, with explosive release of magmatic unusual example of a regionally developed, basaltic lahar volatiles in large part driving the eruptions in these cases. field. Rapid thickness variations are interpreted to reflect the A notable feature of the laharic deposits is their high con- effects of extensional faulting during accumulation of the tent of accidental lithic debris derived from quartzose sand- lahars, and clear evidence that monoclinal warping and stone, silicic tuff, and carbonaceous shale in the underlying explosive volcanism were broadly contemporaneous has been Falla Formation. This debris ranges from discrete sand grains documented by Elliot and Larsen (1993, pp. 397-410). present in abundance in the matrix of the lahars to boulder- Detailed mapping during the present study has shown that sized clasts measuring 50 centimeters or more across (figure deposition of thick lahars in steep-sided channels occurred 1). Apparently, violent disruption of parts of the Falla Forma- during large-scale slumping of the Falla Formation, providing tion occurred when subterranean steam explosions were initi-

ANTARCTIC JOURNAL - REVIEW 1994 33