Graduation Date

Spring 2020

Document Type

Thesis

Program

Master of Science degree with a major in Biology

Committee Chair Name

Dr. Alexandru M.F. Tomescu

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Gar Rothwell

Second Committee Member Affiliation

Community Member or Outside Professional

Third Committee Member Name

Paul Kenrick

Third Committee Member Affiliation

Community Member or Outside Professional

Fourth Committee Member Name

Michael Mesler

Fourth Committee Member Affiliation

HSU Faculty or Staff

Subject Categories

Botany

Abstract

Secondary growth from a vascular cambium has a deep fossil record among euphyllophytes, with the earliest occurrence dated to 407 Ma. To date, Armoricaphyton and Franhueberia represent the only instances of secondary growth formally documented in the Early Devonian. Secondary growth diversified rapidly and was present in all major euphyllophyte lineages by the Middle Devonian. Here, I describe two new Early Devonian euphyllophytes exhibiting secondary growth, from the Emsian (c. 400-395 Ma) Battery Point Formation (Québec, Canada): Gmujij tetraxylopteroides gen. et sp. nov. and Perplexa praestigians gen et sp. nov. Both these plants possess mesarch actinosteles with Psilophyton-type tracheid thickenings, and each represents a new type of anatomical organization among Early Devonian wood-producing euphyllophytes. These new Early Devonian plants reveal an unexpected level of diversity in the early stages of the first major tracheophyte radiation. Importantly, Gmujij and Perplexa, together with the other Early Devonian euphyllophytes exhibiting secondary growth, reinforce existing hypotheses about the modular regulation of vascular cambial growth and demonstrate that vascular cambial growth is an assemblage of regulatory modules whose deployment followed a mosaic pattern in the evolution of tracheophytes.

Citation Style

Papers in Palaeontology

Pfeiler2020_Chapter1_TracheidMeasurements.csv (19 kB)
Tracheid measurements for Chapter 1

Pfeiler2020_Chapter2_MetaxylemTracheidMeasurements.csv (2 kB)
Metaxylem tracheid measurements for Chapter 2

Pfeiler2020_Chapter2_SecondaryXylemTracheidMeasurements.csv (4 kB)
Secondary xylem tracheid measurements for Chapter 2

Pfeiler2020_Chapter2_RoundnessCircularity.csv (60 kB)
Metaxylem roundness and circularity measurements for Chapter 2

Pfeiler2020_Chapter2_RoundnessCircularityOutlines.pdf (9834 kB)
Metaxylem roundness and circularity outlines for Chapter 2

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