DOCSLIB.ORG

Stratigraphy and Sedimentary Petrology of the Fremouw Formation (Lower Triassic), Cumulus Hills, Central Transantarctic Mountain

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Stratigraphy and Sedimentary Petrology of the Fremouw Formation (Lower Triassic), Cumulus Hills, Central Transantarctic Mountain This raises the question of what the food of the antarctic The Fremouw Formation of the Cumulus Hills represents proto-lizard may have been. Gow (1975), in his monograph a small part of a large river system that probably drained the on Prolacerta from South Africa, suggested that this reptile fed Gondwanian orogenic belt (Elliot, 1975). Streams in the upon "the young of many small synapsids [mammal-like rep- Cumulus Hills area flowed toward the southwest from a tiles] procolophonids and labyrinthodonts [amphibians], source terrane that included volcanic, metamorphic, and as well as insects." Gow also suggests that Prolacerta—"a light, sedimentary rocks. Rocks in the lower and middle Fremouw swift creature"—may have been to some extent arboreal. Ap- are interpreted to represent broad, relatively straight, sand- plying these considerations to the presumed Prolacerta in Ant- bed variable discharge rivers separated by well-vegetated arctica, we can speculate on the environment of this part of flood plains. The upper Fremouw represents a system of Gondwanaland in early Triassic time. We know there were braided streams in which the flood-plain facies is poorly trees and other forms of vegetation. There must have been in- represented. This change was possibly related to renewed sects, for the antarctic proto-lizard is of such small size that uplift or increased volcanism in the source area or to climatic insects probably formed a large part of its diet. But we still change. have much to learn about the fauna and flora of the Fremouw The Fremouw Formation in the Cumulus Hills is approx- Formation. imately 700 meters thick (Kitching et al., 1972) and can be The study of Prolacerta from Antarctica was supported in divided into 3 informal members, although thicknesses of part by National Science Foundation grant DPP 75-23136. these members vary greatly from locality to locality. The lower member consists of approximately equal amounts of ledge-forming sandstone and slope-forming mudstone; the middle member is predominantly slope-forming siltstone and References mudstone with varying proportions of ledge-forming sandstone; and the upper member is mostly ledge-forming sandstone. The lower member was studied at Thrinaxodon Colbert, E. H. 1975. Further determinations of Antarctic Triassic Col and Collinson Ridge, the lower and middle members at tetrapods. Antarctic Journal of the Us., 20(5): 250-252. the head of LaPrade Valley and Shenk Peak, and a part of Gow, C.E. 1975. The morphology and relationships of Youngina the upper member near the top of Mt. Kenyon. capensis Broom and Prolacerta broomz Parrington. Palaeontologia Two major facies occur in the Fremouw Formation, chan- Africana, 18:89-131. nel and flood-plain. Channel-lag deposits of conglomerate commonly occur above the basal erosion surfaces of channels and above large scour surfaces within sandstone units. Most clasts are locally derived mudstone chips, pebbles, and cob- bles, but quartz pebbles and vertebrate bones occur sporadically. Characteristic features of channels are large scours with single trough-fills [or cosets] of festoon cross- beds, which probably represent high-flow scour and fill Stratigraphy and sedimentary and/or fill at lower flow by linguoid dunes and bars (figure 1). Beds are commonly distorted by soft-sediment deforma- petrology of the Fremouw tion. Tops of some major scours and truncation surfaces are Formation (Lower Triassic), overlain by thin, silty mudstone drapes that are commonly burrowed and mud-cracked. Cumulus Hills, Central The flood-plain facies comprise: (a) fining-upward se- Transantarctic Mountains quences of greenish-gray, fine-grained argillaceous sandstone, siltstone, and mudstone; (b) tabular sheets of low angle cross-bedded and horizontally bedded, medium- grained sandstone (figure 2); and (c) fining-upward se- JAMES W. COLLINSON, KENNETH 0. STANLEY, and quences of red, sandy siltstone and mudstone. Fine-grained CHARLES L. VAVRA sandstone commonly exhibits parting lineation and small- Institute of Polar Studies and scale cross-bedding. Root casts and burrows are most abun- Department of Geology and Mineralogy dant in the greenish-gray rocks; only the tops of redbeds con- The Ohio State University tain root casts. Tabular sheets of medium-grained sandstone, Columbus, Ohio 43210 intercalated in the flood-plain facies, are characterized by bottom surfaces that are not scoured. In some cases sandstone has filled mudcracked surfaces on the underlying mudstone (figure 3). These sandstones represent rapid progradation of Sedimentologic investigations in the Cumulus Hills, com- sand across the flood plain during overbank flow. Their inter- bined with vertebrate paleontologic studies (Cosgriff et al., nal structures suggest lobate-bar, sand-delta, and sheet-sand 1978), are providing new information about Early Triassic deposition where the stream expanded onto the flood plain. paleogeography in Antarctica. A seven-man camp was Streams that deposited Fremouw sandstone in the established on the McGregor Glacier (175°W.85°S.) on 21 Cumulus Hills were of low sinuosity and flowed toward the November 1977 near the site of the 1970 camp. The three southwest. This is in contrast with the northwesterly sedimentologists left the field with the midseason supply paleocurrent directions reported by Barrett (1970) for the Fre- flight on 11 December 1977. Localities in the Cumulus Hills mouw Formation in the Queen Alexandra Range. Of 508 were reached by motor toboggan via LaPrade Valley or the cross-bed readings in the Cumulus Hills, the mean direction Shackleton Glacier. was 223°, s=±62°. In the lower and middle members, 427 October 1978 21 * Figure 1. Channel fades in the lower Fremouw Formation at Figure 3. Mudcracks on bottom surface of sheet sandstone In Shenk Peak showing cross-bedded sandstone and large flood-plaIn fades. scour surface overlain by a pebble lag and filled with festoon cross-bedded sandstone. the source were pyroclastic flows. Post-depositional modifica tions to Fremouw sandstones include formation of cements, destruction and replacement of grains, and dissolution of grains. Authigenic cements and minerals that replace detrital grains include zeolites, prehnite, and phyllosilicates. The important volcanic components in sandstones of the lower Fremouw in the Cumulus Hills are not characteristic of the formation in the Queen Alexandra Range, where Barrett (1969) reported subarkose. However, in both areas the mid- dle and upper members are similarly dominated by volcanic lithic fragments. Our interpretations of the sandstone petrology in the Cumulus Hills differ from those of LaPrade (1970), who described these rocks as feldspathic graywackes. This research was supported by National Science Founda- tion grant DPP 76-23431. References Figure 2. Flood-plain fades at Shenk Peak In middle Fremouw Barrett, P. J 1969. Formation showing fining-upward, . Stratigraphy and petrology of the mainly fluviatile greenish-gray siltstone to Permian and Triassic Beacon rocks. Beardmore Glacier area. mudstone sequences and tabular sheets of medium-grained Report Institute Polar Studies, Ohio State University, 34. sandstone. Barrett, P. J. 1970. Paleocurrent analysis of the mainly fluviatile Per- mian and Triassic Beacon Antarctica: Journal of Sedimentary readings indicate a mean direction of 219, s= ±45°. Fewer Petrology, 40(1): 395-411. readings in the upper Fremouw (78) indicate a mean direc- Cosgriff,J. W., W. R. Hammer, J. M. Zawiskie, and N. R. Kemp. tion of 246°, s = ±36°. Most of the dispersion occurs in sepa- 1978. New Triassic vertebrates from the Fremouw Formation of rate but closely spaced sandstone units. Dispersal directions the Queen Maud Mountains. Antarctic Journal of the US., 13(4). are similar in flood-plain and channel facies. The variation in 23-24. direction from large- and small-scale cross-beds and from Elliot, D. H. 1975. Gondwana basins of Antarctica. In: Gondwana parting lineation is insignificant. Geology (K, S. W. Campbell, ed.). A.N.U. Press, Canberra. pp. 493-536. Channel and coarser flood-plain deposits of the Fremouw Kitching, J Formation are dominantly medium- to fine-grained, well . W., J. W. Collinson, D. H. Elliot, and E. H. Colbert. 1972. Lystrosaurus sorted volcanic sandstone. Detrital rock fragments, quartz, zone (Triassic) fauna from Antarctica. Science, 175(402): 524-527. feldspar, and heavy mineral grains indicate a source terrane LaPrade, K. E. dominated by felsic volcanic rocks with subordinate 1970. Permian-Triassic Beacon group of the Shackleton Glacier area, Queen Maud Range, Transantarctic metamorphic and sedimentary rocks. Relic shard and Mountains, Antarctica. Geological Society America, Bulletin, 81(5): pumaceous structures indicate that some of the volcanics at 1403-1410. 22 ANTARCTIC JOURNAL.
Load more

Recommended publications
  • 8. Archosaur Phylogeny and the Relationships of the Crocodylia
    8. Archosaur phylogeny and the relationships of the Crocodylia MICHAEL J. BENTON Department of Geology, The Queen's University of Belfast, Belfast, UK JAMES M. CLARK* Department of Anatomy, University of Chicago, Chicago, Illinois, USA Abstract The Archosauria include the living crocodilians and birds, as well as the fossil dinosaurs, pterosaurs, and basal 'thecodontians'. Cladograms of the basal archosaurs and of the crocodylomorphs are given in this paper. There are three primitive archosaur groups, the Proterosuchidae, the Erythrosuchidae, and the Proterochampsidae, which fall outside the crown-group (crocodilian line plus bird line), and these have been defined as plesions to a restricted Archosauria by Gauthier. The Early Triassic Euparkeria may also fall outside this crown-group, or it may lie on the bird line. The crown-group of archosaurs divides into the Ornithosuchia (the 'bird line': Orn- ithosuchidae, Lagosuchidae, Pterosauria, Dinosauria) and the Croco- dylotarsi nov. (the 'crocodilian line': Phytosauridae, Crocodylo- morpha, Stagonolepididae, Rauisuchidae, and Poposauridae). The latter three families may form a clade (Pseudosuchia s.str.), or the Poposauridae may pair off with Crocodylomorpha. The Crocodylomorpha includes all crocodilians, as well as crocodi- lian-like Triassic and Jurassic terrestrial forms. The Crocodyliformes include the traditional 'Protosuchia', 'Mesosuchia', and Eusuchia, and they are defined by a large number of synapomorphies, particularly of the braincase and occipital regions. The 'protosuchians' (mainly Early *Present address: Department of Zoology, Storer Hall, University of California, Davis, Cali- fornia, USA. The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds (ed. M.J. Benton), Systematics Association Special Volume 35A . pp. 295-338. Clarendon Press, Oxford, 1988.
    [Show full text]
  • University of Birmingham the Earliest Bird-Line Archosaurs and The
    University of Birmingham The earliest bird-line archosaurs and the assembly of the dinosaur body plan Nesbitt, Sterling; Butler, Richard; Ezcurra, Martin; Barrett, Paul; Stocker, Michelle; Angielczyk, Kenneth; Smith, Roger; Sidor, Christian; Niedzwiedzki, Grzegorz; Sennikov, Andrey; Charig, Alan DOI: 10.1038/nature22037 License: None: All rights reserved Document Version Peer reviewed version Citation for published version (Harvard): Nesbitt, S, Butler, R, Ezcurra, M, Barrett, P, Stocker, M, Angielczyk, K, Smith, R, Sidor, C, Niedzwiedzki, G, Sennikov, A & Charig, A 2017, 'The earliest bird-line archosaurs and the assembly of the dinosaur body plan', Nature, vol. 544, no. 7651, pp. 484-487. https://doi.org/10.1038/nature22037 Link to publication on Research at Birmingham portal Publisher Rights Statement: Checked for eligibility: 03/03/2017. General rights Unless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or the copyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposes permitted by law. •Users may freely distribute the URL that is used to identify this publication. •Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of private study or non-commercial research. •User may use extracts from the document in line with the concept of ‘fair dealing’ under the Copyright, Designs and Patents Act 1988 (?) •Users may not further distribute the material nor use it for the purposes of commercial gain. Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document.
    [Show full text]
  • Gondwana Vertebrate Faunas of India: Their Diversity and Intercontinental Relationships
    438 Article 438 by Saswati Bandyopadhyay1* and Sanghamitra Ray2 Gondwana Vertebrate Faunas of India: Their Diversity and Intercontinental Relationships 1Geological Studies Unit, Indian Statistical Institute, 203 B. T. Road, Kolkata 700108, India; email: [email protected] 2Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, India; email: [email protected] *Corresponding author (Received : 23/12/2018; Revised accepted : 11/09/2019) https://doi.org/10.18814/epiiugs/2020/020028 The twelve Gondwanan stratigraphic horizons of many extant lineages, producing highly diverse terrestrial vertebrates India have yielded varied vertebrate fossils. The oldest in the vacant niches created throughout the world due to the end- Permian extinction event. Diapsids diversified rapidly by the Middle fossil record is the Endothiodon-dominated multitaxic Triassic in to many communities of continental tetrapods, whereas Kundaram fauna, which correlates the Kundaram the non-mammalian synapsids became a minor components for the Formation with several other coeval Late Permian remainder of the Mesozoic Era. The Gondwana basins of peninsular horizons of South Africa, Zambia, Tanzania, India (Fig. 1A) aptly exemplify the diverse vertebrate faunas found Mozambique, Malawi, Madagascar and Brazil. The from the Late Palaeozoic and Mesozoic. During the last few decades much emphasis was given on explorations and excavations of Permian-Triassic transition in India is marked by vertebrate fossils in these basins which have yielded many new fossil distinct taxonomic shift and faunal characteristics and vertebrates, significant both in numbers and diversity of genera, and represented by small-sized holdover fauna of the providing information on their taphonomy, taxonomy, phylogeny, Early Triassic Panchet and Kamthi fauna.
    [Show full text]
  • An Icehouse to Greenhouse Transition in Permian Through Triassic Sediments, Central Transantarctic Mountains, Antarctica
    An icehouse to greenhouse transition in Permian through Triassic sediments, Central Transantarctic Mountains, Antarctica Peter Flaig, Bureau of Economic Geology Icehouse vs. Greenhouse Icehouse vs. Greenhouse Icehouse vs. Greenhouse Gornitz, 2009 Heading to Svalbard… so why talk about Antarctica? Svalbard and Antarctica both spent some time at high latitudes (in both modern and ancient times) Both currently have little to no vegetation (laterally extensive outcrop exposures) Some rocks are from similar time periods (compare Svalbard, northern hemisphere to Antarctica, southern hemisphere) Can use Antarctic strata to show you some qualities of outcrop belts and sediments that we use to understand ancient environments Understanding how changing environments are expressed in outcrops (Svalbard trip) helps us predict reservoir quality and reservoir geometries From overall geometries- to facies- to environments Idea: Step back and look at the outcrop as a whole (large scale) Look at the inetrplay between sand and mud deposition and preservation Make some prediction about reservoirs vs. source rocks and bad vs. good reservoirs Look closer at the facies to help us refine our interpretations (smaller scale) Central Transantarctic Mountains Geology Similar Age Catuneanu, 2004 Volcanic Arc Craton (continent) Active Margin Transantarctic Basin = retroarc foreland basin Long et al., 2008 Collinson et al., 2006 200 MA Dicroidium 245 Cynognathus Lystrosaurus P/T Ext. Glossopteris This talk This 300 415 MA Isbell et al., 2003 300 m Jurassic sill (Gondwana
    [Show full text]
  • Migration of Triassic Tetrapods to Antarctica J
    U.S. Geological Survey and The National Academies; USGS OF-2007-1047, Extended Abstract 047 Migration of Triassic tetrapods to Antarctica J. W. Collinson1 and W. R. Hammer2 1Byrd Polar Research Center and School of Earth Sciences, Ohio State University, Columbus, OH. 43210 USA ([email protected]) 2Augustana College, Rock Island, IL. 61201 ([email protected]) Summary The earliest known tetrapods in Antarctica occur in fluvial deposits just above the Permian-Triassic boundary in the central Transantarctic Mountains. These fossils belong to the Lystrosaurus Zone fauna that is best known from the Karoo basin in South Africa. The Antarctic fauna is less diverse because of fewer collecting opportunities and a higher paleolatitude (65º vs. 41º). Many species are in common. Lystrosaurus maccaigi, which is found near the base of the Triassic in Antarctica, has been reported only from the Upper Permian in the Karoo. Two other species of Lystrosaurus in Antarctica are also likely to have originated in the Permian. We hypothesize that tetrapods expanded their range into higher latitudes during global warming at the Permian- Triassic boundary. The migration route of tetrapods into Antarctica was most likely along the foreland basin that stretched from South Africa to the central Transantarctic Mountains along the Panthalassan margin of Gondwana. Citation: Collinson, J. W., and W. R. Hammer (2007), Migration of Triassic Tetrapods to Antarctica, in Antarctica: A Keystone in a Changing World – Online Proceedings of the 10th ISAES X, edited by A. K. Cooper and C. R. Raymond et al., USGS Open-File Report 2007-1047, Extended Abstract 047, 3 p.
    [Show full text]
  • Downloaded from Brill.Com10/06/2021 02:24:59PM Via Free Access 78 IAWA Journal, Vol
    lAWA Journal, Vol. 17 (1),1996: 77-88 WOUND RESPONSE IN FOSSIL TREES FROM ANTARCTICA AND ITS POTENTIAL AS A PALEOENVIRONMENTAL INDICATOR by Michelle K. Putz? & Edith L. Taylor! SUMMARY Numerous permineralized axes of Middle Triassic age from Fremouw Peak, Antarctica show evidence of mechanical wounding and wound responses. These consist of both elongate and triangular-shaped scars. Some scars can be detected beneath subsequent secondary xylem, indicating that wounding occurred early in stem development. In other stems, scars remained open suggesting late wounding and the perma­ nent disruption of the cambium. In cross section most stems display little cal1ustissue, but wound periderm can be seen along the margin of the scar. In some stems the wound phellogen has formed phellem and phelloderm within the wounded area oriented perpendicular to the growth rings. Although some scars resemble those produced by fires, we were unable to document the presence of charcoal around scars. In modem ecosystems wounds may be caused by other agents, including debris drifting in floods, flowing ice, avalanches, and animals. Each of these potential sources is reviewed in relationship to the paleoclimate in the region during the Triassic. Key words: Antarctica, wound, fire, flood, fossil wood. INTRODUCTION Modem forest ecosystems are subject to natural disturbance of all types from fire and flood to insect and disease outbreaks (White 1979; Agee 1990). Fires, floods, animals, and other agents can also damage individual trees, causing their bark to be broken. Once the bark barrier is breached some type of wound response usually results . If damage is extensive, the wounded tree may die.
    [Show full text]
  • Annual Report 2011
    Natural and Agricultural Sciences Annual Report 2011 Natural and Agricultural Sciences Annual Report 2011 Contact Details Dean Prof Neil Heideman +27 (0)51 401 2322 [email protected] Vice-Dean Prof. Corli Witthuhn +27 (0) 51 4013855 [email protected] Faculty Manager Mr Johan Kruger +27 (0)51 401 2409 Issued by [email protected] Faculty of Natural and Agricultural Sciences Marketing Manager University of the Free State Ms Elfrieda Lotter Editorial Compilation +27 (0)51 4012531 [email protected] Betta van Huyssteen Physical Address Language Revision Room 9A, Biology Building, Main Campus, Bloemfontein Betta van Huyssteen Stella Mcgill Postal Address Revision of Bibliographical Data University of the Free State PO Box 339 Mercia Coetzee Bloemfontein Design, Layout South Africa 9300 Chrysalis Advertising & Publishing Fax: +27 (0)51 401 3728 Printing E-mail: [email protected] Oranje Drukkery • Printers Faculty website: www.ufs.ac.za/natagri Table of Contents Preface 5 Research Clusters 6 Agricultural Sciences 13 Agricultural Economics 14 Animal, Wildlife and Grassland Sciences 20 Plant Sciences 30 Soil, Crop and Climate Sciences 40 Building Sciences 49 Architecture 50 Quantity Surveying and Construction Management 56 Urban and Regional Planning 62 Natural Sciences 67 Chemistry 68 Computer Science and Informatics 86 Consumer Science 94 Genetics 100 Geography 108 Geology 116 Mathematical Statistics and Actuarial Science 126 Mathematics and Applied Mathematics 132 Microbial, Biochemical and Food Biotechnology 136 Physics 150 Zoology
    [Show full text]
  • An Exceptional Fossil Skull from South America and the Origins of the Archosauriform Radiation Received: 18 December 2015 Felipe L
    www.nature.com/scientificreports OPEN An exceptional fossil skull from South America and the origins of the archosauriform radiation Received: 18 December 2015 Felipe L. Pinheiro1, Marco A. G. França2, Marcel B. Lacerda3, Richard J. Butler4 & Accepted: 22 February 2016 Cesar L. Schultz3 Published: 11 March 2016 Birds, dinosaurs, crocodilians, pterosaurs and their close relatives form the highly diverse clade Archosauriformes. Archosauriforms have a deep evolutionary history, originating in the late Permian, prior to the end-Permian mass extinction, and radiating in the Triassic to dominate Mesozoic ecosystems. However, the origins of this clade and its extraordinarily successful body plan remain obscure. Here, we describe an exceptionally preserved fossil skull from the Lower Triassic of Brazil, representing a new species, Teyujagua paradoxa, transitional in morphology between archosauriforms and more primitive reptiles. This skull reveals for the first time the mosaic assembly of key features of the archosauriform skull, including the antorbital and mandibular fenestrae, serrated teeth, and closed lower temporal bar. Phylogenetic analysis recovers Teyujagua as the sister taxon to Archosauriformes, and is congruent with a two-phase model of early archosauriform evolution, in response to two mass extinctions occurring at the end of the Guadalupian and the Permian. Birds, dinosaurs, crocodilians, and pterosaurs all belong to the clade Archosauriformes1, an extraordinarily diverse group that dominated terrestrial tetrapod faunas worldwide for nearly the entire Mesozoic Era2–4, around 175 million years, and plays a major role in the modern biota, with birds comprising around a third of extant tetrapod biodiversity5,6. The Permian origin of the clade and its major diversification during the Triassic follow- ing the end-Permian mass extinction event were events of exceptional significance that fundamentally reshaped ecosystems on land2,7–11.
    [Show full text]
  • Dr. John L. Isbell Department of Geosciences, University of Wisconsin-Milwaukee P.O
    Dr. John L. Isbell Department of Geosciences, University of Wisconsin-Milwaukee P.O. Box 413, Milwaukee, WI 53201 Phone: (414) 229-2877 e-mail: [email protected] http://www.uwm.edu/People/jisbell/index.html EDUCATION 1990 Ph.D., Geology. THE OHIO STATE UNIVERSITY, Columbus, Ohio. Dissertation Topic: Fluvial sedimentology and basin analysis of the Permian Fairchild and Buckley Formations, Beardmore Glacier Region, and the Weller Coal Measures, southern Victoria Land, Antarctica. Dissertation Advisor: Dr. James W. Collinson. 1985 M.S., Geology. NORTHERN ILLINOIS UNIVERSITY, DeKalb, Illinois. Thesis topic: Palynology and sedimentology of Pennsylvanian strata in the northwestern portion of the Illinois Basin. Thesis advisors: Dr. Ross D. Powell and Dr. Hsin Yi Ling. 1981 B.A., Geology. AUGUSTANA COLLEGE, Rock Island, Illinois. Advisors: Dr. Richard Anderson and Dr. Fred H. Behnken. POSITIONS HELD 9/04-Present Professor: Department of Geosciences, The University of Wisconsin-Milwaukee. Clastic sedimentologist. 9/09-8/12 Department Chair: Department of Geosciences, The University of Wisconsin- Milwaukee. 9/98-9/04 Associate Professor: Department of Geosciences, The University of Wisconsin- Milwaukee. Clastic sedimentologist. 9/92-8/98 Assistant Professor: Department of Geosciences, The University of Wisconsin- Milwaukee. Clastic sedimentologist. 5/95-97 Project Contributor: Geological Evolution and Hydrocarbon Plays of the Southern South Atlantic. A joint international project utilizing the specialties of geologists from the Cambridge Arctic Shelf Programme, Cambridge, U.K.; Centro de Investigaciones Geologicas, La Plata, Argentina; University of Aberdeen, Scotland; Institute of Geophysics at the University of Texas-Austin; University of Cambridge, U.K.; and the Department of Geosciences at the University of Wisconsin-Milwaukee.
    [Show full text]
  • Early Triassic
    www.nature.com/scientificreports OPEN A new specimen of Prolacerta broomi from the lower Fremouw Formation (Early Triassic) of Received: 12 June 2018 Accepted: 21 November 2018 Antarctica, its biogeographical Published: xx xx xxxx implications and a taxonomic revision Stephan N. F. Spiekman Prolacerta broomi is an Early Triassic archosauromorph of particular importance to the early evolution of archosaurs. It is well known from many specimens from South Africa and a few relatively small specimens from Antarctica. Here, a new articulated specimen from the Fremouw Formation of Antarctica is described in detail. It represents the largest specimen of Prolacerta described to date with a nearly fully articulated and complete postcranium in addition to four skull elements. The study of this specimen and the re-evaluation of other Prolacerta specimens from both Antarctica and South Africa reveal several important new insights into its morphology, most notably regarding the premaxilla, manus, and pelvic girdle. Although well-preserved skull material from Antarctica is still lacking for Prolacerta, a detailed comparison of Prolacerta specimens from Antarctica and South Africa corroborates previous fndings that there are no characters clearly distinguishing the specimens from these diferent regions and therefore the Antarctic material is assigned to Prolacerta broomi. The biogeographical implications of these new fndings are discussed. Finally, some osteological characters for Prolacerta are revised and an updated diagnosis and phylogenetic analysis are provided. Prolacerta broomi is a medium sized non-archosauriform archosauromorph with a generalized, “lizard-like” body type. Many specimens, mostly consisting of cranial remains, have been described and Prolacerta is considered one of the best represented early archosauromorphs1–3.
    [Show full text]
  • Permian Extinction Event in Australia
    PALAIOS, 2020, v. 35, 342–357 Research Article DOI: http://dx.doi.org/10.2110/palo.2020.007 DWELLING IN THE DEAD ZONE—VERTEBRATE BURROWS IMMEDIATELY SUCCEEDING THE END- PERMIAN EXTINCTION EVENT IN AUSTRALIA 1 1 1 2 3 3 STEPHEN MCLOUGHLIN, CHRIS MAYS, VIVI VAJDA, MALCOLM BOCKING, TRACY D. FRANK, AND CHRISTOPHER R. FIELDING 1Swedish Museum of Natural History, Svante Arrhenius v. 9, SE-104 05, Stockholm, Sweden 2Bocking Associates, 8 Tahlee Close, Castle Hill, NSW, Australia 3Department of Earth and Atmospheric Sciences, University of Nebraska-Lincoln, 126 Bessey Hall, Lincoln, NE 68588-0340, USA email: [email protected] ABSTRACT: A distinctive burrow form, Reniformichnus australis n. isp., is described from strata immediately overlying and transecting the end-Permian extinction (EPE) horizon in the Sydney Basin, eastern Australia. Although a unique excavator cannot be identified, these burrows were probably produced by small cynodonts based on comparisons with burrows elsewhere that contain body fossils of the tracemakers. The primary host strata are devoid of plant remains apart from wood and charcoal fragments, sparse fungal spores, and rare invertebrate traces indicative of a very simplified terrestrial ecosystem characterizing a ‘dead zone’ in the aftermath of the EPE. The high-paleolatitude (~ 65–758S) setting of the Sydney Basin, together with its higher paleoprecipitation levels and less favorable preservational potential, is reflected by a lower diversity of vertebrate fossil burrows and body fossils compared with coeval continental interior deposits of the mid-paleolatitude Karoo Basin, South Africa. Nevertheless, these burrows reveal the survivorship of small tetrapods in considerable numbers in the Sydney Basin immediately following the EPE.
    [Show full text]
  • Under Pressure? Epicormic Shoots and Traumatic Growth Zones in High-Latitude Triassic Trees from East Antarctica
    Annals of Botany 121: 681–689, 2018 doi:10.1093/aob/mcx199, available online at www.academic.oup.com/aob Under pressure? Epicormic shoots and traumatic growth zones in high-latitude Triassic trees from East Antarctica Anne-Laure Decombeix1,2,*, Rudolph Serbet2 and Edith L. Taylor2 1CNRS and Université Montpellier 2, UMR AMAP, F-34000 Montpellier, France and 2Department of Ecology and Evolutionary Biology, and Natural History Museum and Biodiversity Institute, University of Kansas, Lawrence, KS 66045–7600, USA Downloaded from https://academic.oup.com/aob/article/121/4/681/4791876 by guest on 29 September 2021 *For correspondence. E-mail: [email protected] Received: 25 September 2017 Returned for revision: 14 November 2017 Editorial decision: 29 November 2017 Accepted: 5 December 2017 Published electronically 6 January 2018 • Background and Aims Investigating the biology of trees that were growing at high latitudes during warmer geological periods is key to understanding the functioning of both past and future forest ecosystems. The aim of this study is to report the first co-occurrence of epicormic shoots and traumatic growth zones in fossil trees from the Triassic of Antarctica and to discuss their biological and environmental implications. • Methods Permineralized woods bearing scars of epicormic shoots were collected from the Triassic Fremouw Formation in Gordon Valley, Central Transantarctic Mountains, Antarctica in 2010. Samples from different portions of three specimens were prepared using standard thin section and hydrofluoric (HF) acid peel techniques, and anatomical details were studied in transmitted light. • Key Results The fossil woods represent the outer part of trunks, with at least 40 growth rings that are 0.2–4.8 mm in width.
    [Show full text]