Evolution and Anatomy of Early Terrestrial Arthropods: Insights from the Rhynie Chert

Colonisation of the land is one of the defining transitions in the history of life on Earth, fundamentally reshaping the planet’s chemical, biological, and geological systems. Among the most significant fossil deposits for understanding this transition is the Lower Devonian (ca. 408 Ma) Rhynie chert of Aberdeenshire, Scotland. Preserved in extraordinary three-dimensional detail by silica sinters from ancient hot springs, the Rhynie chert represents the earliest complex land animal ecosystem in the fossil record. Its diverse biota includes pioneering plants, fungi, bacteria, and many modern animal groups, such as hexapods, arachnids, myriapods, and nematodes, providing a unique glimpse into the world where some of the earliest unequivocal land animals took their first steps. This thesis employs confocal laser scanning microscopy (CLSM) to investigate the anatomical and functional adaptations of Rhynie arthropods, addressing key questions about the evolution of arthropod terrestrialisation and the morphological innovations that enabled life to proliferate on land. Through detailed analyses, this research examines the functional morphology and phylogeny of trigonotarbid arachnids, highlighting key adaptations for terrestrial life and reaffirming their placement within or as a sister-group to Tetrapulmonata (Chapters 2 & 3). Additionally, a comprehensive reassessment of the enigmatic fossil Rhyniognatha hirsti revises its phylogenetic placement and challenges its controversial status as a calibration point for insect evolution (Chapter 4). Chapter 1 situates the Rhynie chert in its broader evolutionary and ecological context, outlines the challenges and opportunities inherent in studying fossils entombed in chert, and introduces the objectives and methodological innovations underpinning this research. Chapter 5 synthesises the findings of this thesis, offering a discussion of the broader implications for understanding early terrestrial ecosystems and the evolutionary history of arthropods. By integrating CLSM imaging with comparative morphological and phylogenetic analyses of fossil and extant taxa, this thesis advances our understanding of early terrestrial ecosystems and underscores the potential of CLSM in palaeontological research.<p></p>

Author dc:creator

• E Long (9876461)

• CLSM
• Rhynie chert
• Arthropod
• Arachnid

Statement dc:rights

• All rights reserved
• Open Access after 2027-03-18

Identifier

10871/140664

OAI identifier oai:identifier

oai:figshare.com:article/29844023