Abstract Detail

Paleobotany

Bickner, Maya [1], Toledo, Selin [2], Tomescu, Alexandru [3].

New fossils from the Battery Point Formation of Gaspé (Quebec, Canada) expand the anatomical diversity of Early Devonian euphyllophytes.

The Battery Point Formation, located on the Gaspé Peninsula hosts a rich Early Devonian (Emsian) flora that represents one of the rare occurrences of anatomically preserved Early Devonian plants. Recent investigations of the permineralized plant assemblages of the Battery Point Formation have uncovered several new types of euphyllophytes represented by small-sized axes with ribbed xylem. A first morphotype is represented by several axes ca. 2 mm in diameter exhibiting mesarch protosteles with three short ribs (up to 180 µm long) and inconspicuous protoxylem strands at each rib tip. The inner cortex, mostly parenchymatous, has a discontinuous layer of sclereids. The outer cortex combines parenchyma and sclerenchyma cells in an alternating pattern and is ca. 192µm thick. A second morphotype is an axis 1.8 mm wide with an oval-shaped protostele that has 3-4 mesarch protoxylem strands forming a line along the xylem midplane. The inner cortex is thin and parenchymatous. The outer cortex, ca. 190µm thick, consists of evenly distributed sclerenchyma cells. A third morphotype represented by a single axis 1.7 mm in diameter, has a 3-ribbed stele with longer (up to 400 µm) mesarch xylem ribs and incompletely preserved extraxylary tissues. A forth morphotype, represented by two axes up to 3.5 mm wide, is characterized by a 4-ribbed protostele. The protostele ribs are up to 168 µm long and protoxylem strands are present at each rib tip and the center of the stele. The inner cortex is mostly parenchymatous, with scattered groups of sclereids. The outer cortex, ca. 220 µm thick, consists of alternating areas of sclerenchyma and parenchyma cells. A fifth type is represented by two axes ca. 2.1 mm in diameter. Although sub-optimally preserved, these axes have steles with 5 and 6 thin xylem ribs up to 580 μm long. Protoxylem strands are present at the stele center, rib tips, and possibly along rib midplanes. The inner cortex is parenchymatous and the outer cortex, ca. 180 µm thick, sclerenchymatous. These five distinct morphotypes offer a new set of previously unknown Early Devonian plants. The features of these plants – ribbed steles, outer cortex with alternating parenchymatous and sclerenchymatous areas, sclereids in inner cortex – are reminiscent of younger (Middle Devonian) structurally-complex euphyllophytes: cladoxylopsids, aneurophytalean progymnsoperms, and stenokolealeans. These new plants broaden considerably the anatomical diversity known in the Early Devonian and demonstrate that the euphyllophyte evolutionary radiation was already exploring different aspects of structural complexity by the Emsian.

1 - Humboldt State University , Botany , 1 Harpst St, Arcata, CA, 95521, USA
2 - Humboldt State University, Department of Biological Sciences, 1, Harpst Street , Arcata, CA, 95521, USA
3 - Humboldt State University, Department Of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA

Keywords:
euphyllophyte
fossil
Paleobotany
Devonian
Canada
tracheophyte
anatomy
xylem
stele
Emsian.

Presentation Type: Oral Paper
Session: 16, Cookson/Moseley and Paleozoic paleobotany
Location: Sundance 4/Omni Hotel
Date: Monday, June 26th, 2017
Time: 4:15 PM
Number: 16003
Abstract ID:166
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award