Abstract Detail

Paleobotanical Section

Ortiz, Ashley [1], Tomescu, Alexandru M.F. [2].

Early Cretaceous (Barremian-Aptian) cupressaceous cones from the Budden Canyon Formation of California.

The Early Cretaceous Budden Canyon Formation of northern California (Valanginian - Turonian) includes near-shore deposits that contain rich plant fossil assemblages in the late Barremian - early Aptian levels (Lower Chickabally Mudstone Member; ca. 125 Ma).  These assemblages had previously yielded a compression flora of >40 taxa, as well as several permineralized fern and spermatophyte fossils.  Recent investigations have revealed a diverse flora preserved by calcium carbonate permineralization and comprising bryophytes, ferns, seed plants, and fungi.  The seed plant material includes abundant conifers: wood, foliage, and fertile structures.  Among the latter are a seed cone and a pollen cone of cupressaceous affinities.  The seed cone is 10 mm long and 7 mm in diameter.  The cone axis (1.2 mm diameter) bears 20-24 helically arranged peltate ovuliferous scales.  The ovuliferous scales are up to 3 mm long, with a cuneate base and a peltate head up to 2 mm wide in longitudinal section.  Resin canals (one per scale) are 45-90µm in diameter.  Scale-shaped leaves at the base of the cone are ca. 1 mm wide, with a central resin canal 70-90µm in diameter.  The pollen cone is 2.3 mm in diameter.  Microsporophylls have a 1.1 mm wide distal lamina with one central resin canal, and bear three ovoid microsporangia each.  Microsporangia are ca. 270 µm wide and at least 500 µm long, and contain abundant pollen; the pollen is spherical, thin-walled and 20-(24)-30µm in diameter.  Cupressaceous affinities of the seed cone are supported by the peltate shape of ovuliferous scales and in the pollen cone by the simple pollen.  The presence of these cones is consistent with the abundant shoots and leaves assignable to Cupressaceae found throughout the Budden Canyon assemblage.  The pollen cone compares favorably to those of many living and extinct Cupressaceae, but incomplete preservation and a paucity of characters renders in-depth comparisons tenuous.  The seed cone is similar in morphology and taxis of the ovuliferous scales to those of living Athrotaxis, Sequoia, and Taxodium (cones of morphologically similar Sequoiadendron are much larger).  Comparable morphologies are known in Late Cretaceous and younger sequoioid and taxodioid cones from North America, Japan, and Europe, but in the Early Cretaceous they have been documented only in Athrotaxites and Athrotaxis (from North and South America); older occurrences of this morphology are not known.  While its taxonomy awaits further resolution, the Budden Canyon cone ranks among the oldest peltate cupressaceous seed cones.

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

Keywords:
Fossil
Cupressaceae
Athrotaxis
Athrotaxites
Sequoia
Taxodium
pollen cone
seed cone
pollen
Cretaceous
California.

Presentation Type: Oral Paper:Papers for Sections
Session: 8
Location: Whitewater/Grove
Date: Monday, July 28th, 2014
Time: 10:15 AM
Number: 8007
Abstract ID:784
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award