Abstract Detail

Paleobotany

Pfeiler, Kelly [1], Matsunaga, Kelly [2], Peterson, Autumn [3], Atkinson, Brian [4].

A new anatomically-preserved cupressaceous seed cone from the Paleogene of Washington State.

The cypress family, Cupressaceae s.l., has a worldwide distribution and with more than 30 extant genera it is the most genus-rich conifer family. Phylogenetic relationships within the family include a ‘taxodiaceous grade’ (e.g., Athrotaxis, Sequoia, Taxodium) and a Cupressaceae s.s. clade (e.g., Juniperus, Cupressus, Thuja), which comprises the bulk of the diversity. Members of the taxodiaceous grade are characterized by ovulate cones with numerous helically arranged bract-scale complexes, whereas species of Cupressaceae s.s. have cones with typically few bract-scale complexes in a opposite decussate or whorled phyllotaxis. While the family has an extensive fossil record reaching back to the Early Jurassic, the earliest records of extant genera of Cupressaceae s.s. have been reported from the Late Cretaceous. Herein, we characterize a new anatomically preserved cupressaceous fossil seed cone from the Makah formation (Eocene–Oligocene boundary; ca. 33 MA) of the Olympic Peninsula of Washington State, based on serial peels and 3D reconstructions of the cone and its vasculature. This cone has a striking combination of taxodiaceous and cupressoid characters. The ovulate cone is woody and globose, 12 mm wide. There are 6 helically arranged peltate bract-scale complexes, each with a prominent, centrally positioned umbo. The cone axis has a continuous cylinder of secondary xylem. Vascular traces supplying the bract-scale complex diverge as a hollow cylinder from the main axis and subsequently divide radially into numerous discrete strands that extend along the entire periphery of the bract-scale complexes. Additionally, 1–2 vascular strands supply the central region of the bract-scale complexes. Abaxial to the vascular trace, 1–3 resin canals originate at the proximal end of bract-scale complex; several smaller resin canals originate de novo on both adaxial and abaxial sides of the bract-scale complex. The overall morphology of the bract-scale complexes of this new cone is similar to those of Cupressaceae s.s., namely those of Cupressoideae; however, the helical phyllotaxis of the cone scales in this new fossil precludes its definitive placement into Cupressoideae. Preliminary phylogenetic analyses recover the Olympic Peninsula cone as sister to Cupressaceae s.s.. The young age of this fossil relative to that of the family, combined with its phylogenetic position and unique combination of characters not seen in extant taxa, suggests that the Olympic Peninsula cone represents a stem lineage of Cupressaceae s.s. that persisted into the Eocene.

1 - University of Kansas, Ecology and Evolutionary Biology, 1200 Sunnyside Avenue, 2041 Haworth Hall , Lawrence, KS, 66045, USA
2 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnysive Ave., Lawrence, KS, 66045, United States
3 - Georgia Institute of Technology, North Avenue, Atlanta, GA, 30332, USA
4 - University Of Kansas, Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Lawrence, KS, 66045, United States

Keywords:
Cupressaceae
Fossil
Paleogene
seed cone
ovulate cone
anatomy.

Presentation Type: Oral Paper
Session: PL2, Paleobotany: Cookson Student Presentations - Session II
Location: /
Date: Monday, July 19th, 2021
Time: 12:45 PM(EDT)
Number: PL2002
Abstract ID:213
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award