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Abstract Detail

Paleobotanical Section

Bippus , Alexander Cole [1], Jordan, Myron [1], Tomescu, Alexandru M.F. [1].

Anatomically preserved Onychiopsis (Dicksoniaceae s.l.) in the Early Cretaceous (Barremian – early Aptian) of northern California.

A diverse Cretaceous compression flora was described by Lester Ward a century ago from the Budden Canyon Formation in northern California.  Subsequent studies of anatomically preserved material documented osmundaceous ferns, conifers, and a fruit-like structure.  Recent collecting in the Lower Chickabally Member (late Barremian - early Aptian, ca. 125 Ma) of this formation has led to the identification of a rich anatomically preserved flora which includes mosses, conifers and associated fungi, as well as fertile and vegetative fern material.  The fertile fern material consists of pinnules with soral sporangia of a leptosporangiate fern.  The pinnules are up to 0.7 cm wide and delicate (4-5 cells thick), with a thicker midrib.  The two pinnule margins are rolled abaxially toward the midrib and overlap extensively, forming a false indusium.  Overall, this structure is 0.7-1.0 mm wide, 1.2-1.6 mm tall, and 4-6 mm long.  Sporangia are attached to a linear receptacle (100 µm wide x 130 µm tall) that runs along the midvein.  A band of vascular tissue (scalariform tracheids) forming an inverted wedge shape in cross section makes up most of the receptacle tissue and connects to the midvein.  Sporangia are small, oblong, and flattened (260-330 µm tall x 190-220 µm wide x 85-130 µm thick), borne on long (ca. 200 µm), narrow (22 µm) stalks.  Sporangia have a uniseriate, nearly vertical annulus consisting of transversally elongated cells (84-120 µm long x 36-55 µm tall x 18-35 µm wide) and uninterrupted by the stalk.  In situ trilete spores display subcircular-triangular ambitus (35-45 µm diameter) with concave sides and rounded angles, and are thick-walled with laevigate surface.  The trilete mark forms prominent ridges and laesurae 17.5 µm long.  The small flattened sporangia with long, slender stalks and nearly vertical annulus place this Budden Canyon fern among the Dicksoniaceae s.l.  While superficial linear sori completely enclosed within highly modified pinnules are not known in extant Dicksoniaceae, the fertile structures of the Budden Canyon fern are assignable the dicksoniaceous fern Onychiopsis known from Jurassic-Cretaceous deposits worldwide.  This first record of permineralized Onychiopsis contributes to understanding of the fertile structures in the genus.  Extinct taxa such as Onychiopsis, which represent an extant lineage but exhibit characters distinct from those seen in living representatives of that lineage, show that modern floras do not encompass all the morphological diversity within some lineages, in this case the dicksoniaceous ferns, and that some of that diversity was lost through extinction.

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1 - Humboldt State University, Department Of Biological Sciences, 1 Harpst Street, Arcata, CA, 95521, USA

false indusium

Presentation Type: Oral Paper:Papers for Sections
Session: 8
Location: Whitewater/Grove
Date: Monday, July 28th, 2014
Time: 11:15 AM
Number: 8011
Abstract ID:849
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award

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