Abstract Detail

Paleobotany

Serbet, Rudolph [1], Decombeix, Anne-Laure [2], Escapa, Ignacio H [3], Harper, Carla J [4], Gulbranson, Erik L [5], Taylor, Edith L [6], Taylor, Thomas N [7].

A diverse Late Triassic flora from the Allan Hills (Lashly Formation), southern Victoria Land, Antarctica.

During the 2014-2015 austral field season, a new locality (“Escapa Heights”) yielding Triassic plants was discovered in Allan Hills, south Victoria Land, Antarctica. The plants are preserved as compressions/impressions and most of the specimens correspond to leaves and fertile reproductive organs. They occur within the Upper Triassic member C of the Lashly Formation, in a siltstone matrix associated with an abandoned channel of a meandering stream system. The intact nature of the majority of compressions/impressions suggests minimal transport, thus the fossil assemblage is likely affiliated with a riparian niche. About 1,300 blocks were collected, typically with several different taxa on each rock surface. Although sphenophyte remains and osmundaceous fronds are present, gymnosperms are by far dominant, both in abundance and in taxonomic diversity. Cycadophytes are the most rare gymnosperm group, with only a few leaves and possible ovulate cones. Strap-shaped leaves assigned to Taeniopteris might represent an additional cycadophyte, but the affinities of this genus are unclear and leaves may belong to the Bennettitales or Pentoxylales. Ginkgophyta leaves (Baiera) are relatively common, while Heidiphyllum and Rissikia leaves indicate that at least two conifer taxa were present. Among the pteridosperms, Lepidopteris (Peltaspermales) fertile axes are reported for the first time from Antarctica. Corystospermales are the dominant group in terms of diversity and abundance, as demonstrated by the numerous Dicroidium species, i.e., D. crassinervis, D. coriaceum, D. dubium, D. elongatum, D. lineatum, D. odontopteroides, D. superbum, and D. zuberi. Some of these leaves have an aberrant morphology (sensu Anderson & Anderson), with a double dichotomy that had previously been reported in several Gondwanan assemblages but never in Antarctica. Reproductive structures of the Corystospermales are diverse, with 2-3 Pteruchus species and 2-3 Umkomasia species, the highest diversity observed at a single Antarctic locality. The assemblage also includes several morphotypes of seeds, and specimens of Dordrechtites, belonging to a putative gymnosperm ovulate organ. The diversity at this site is completed by remains of unknown taxa, such as highly reticulated leaves similar to the genus Chiropteris. In addition, some leaves show evidence of plant-arthropod interactions (e.g., chew marks, galls). Fossils from this locality constitute by far the most taxonomically diverse Triassic compression/impression assemblage yet described from Antarctica. As such, they provide an opportunity not only to reconstruct whole-plant taxa but also to better understand the ecology of high-latitude floras during the Triassic.

1 - University Of Kansas, Division Of Paleobotany, Natural History Museum and Biodiversity Institute, 1200 Sunnyside Avenue, Lawrence, KS, 66045, USA
2 - CNRS, UMR AMAP, C/o CIRAD, TA A51/PS2, Bvd De La Lironde, Montpellier, F-34398, France
3 - Museo Paleontológico Egidio Feruglio, Avenida Fontana 140, Trelew, 9100, Argentina
4 - Ludwig-Maximilians-Universitaät, Richard-Wagner-Straße, Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Bayerische Staatssammlung für Paläontologie und Geolo, Richard-Wagner-Straße 10, 80333, Munich, 80333, Germany
5 - University of Wisconsin-Milwaukee, Geosciences, 3209 N. Maryland Ave, Lapham Hall 366, Dept of Geosciences, Milwaukee, WI, 53211, USA
6 - University of Kansas, KU Biodiversity Institute, 1345 Jayhawk Boulevard, Lawrence, KS, 66045, United States
7 - University of Kansas, Ecology & Evolutionary Biology, KU Biodiversity Institute, 1345 Jayhawk Boulevard, Lawrence, KS, 66045, United States

Keywords:
Gondwana
Antarctica
Triassic
high-latitude
gymnosperms
compression/impression.

Presentation Type: Oral Paper
Session: 23, Paleozoic and Mesozoic Paleobotany
Location: 102/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 10:15 AM
Number: 23008
Abstract ID:165
Candidate for Awards:None