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Morphological and Behavioural Evolution Through MORPHOLOGICAL AND BEHAVIOURAL EVOLUTION THROUGH THE EDIACARAN AND BASAL CAMBRIAN OF THE MACKENZIE MOUNTAINS, NW CANADA by Calla Agnes Carbone A thesis submitted to the Department of Geological Sciences and Geological Engineering In conformity with the requirements for the Degree of Master of Science Queen’s University Kingston, Ontario, Canada (January, 2014) Copyright © Calla Agnes Carbone, 2014 i Abstract The Mackenzie Mountains of NW Canada contains a superb record of biotic evolution through the late Ediacaran-early Cambrian that is ideal for studying the biological, ecological, behavioural, and environmental innovations that occurred during the Ediacaran and basal Cambrian. Newly discovered Ediacara-type megafossils in the uppermost Blueflower Formation at Sekwi Brook include tubes possibly attributable to suspension-feeding annelids, the preserved top of a large frond holdfast, and several problematica. These fossils represent the youngest and shallowest Ediacaran fossils known from NW Canada, and differ significantly from the communities of deep-water rangeomorphs preserved lower in the succession. Behavioural evolution of the infauna through the Ediacaran and earliest Cambrian can be observed in the rich trace fossil records of the Blueflower and Ingta formations. Trace fossils in the lower part of the Blueflower Formation are characterized by millimeter-diameter, simple, horizontal burrows of microbial grazers and deposit feeders that demonstrated very primitive and inconsistent two-dimensional avoidance strategies. Upper Blueflower trace fossils additionally include three-dimensional avoidance burrows and oblique burrows of filter-feeders or predators, reflecting new behavioural innovations and increased three-dimensional use of the substrate. The Cambrian strata of the Ingta Formation further include probing, U-shaped, and radiating burrows, irregular networks, and arthropod trails. These new feeding strategies were accompanied by increasingly more systematic grazing burrows. The development of more diverse feeding styles upwards through the succession both caused and reflected the spatial and temporal disappearance of Proterozoic matgrounds and their replacement by Phanerozoic mixgrounds. Avoidance strategies among grazing burrows became more consistent and complicated upward throughout this succession, increasingly resembling the guided meanders of Phanerozoic trace fossils. This implies that, while the first avoidance burrows probably reflected the responses of individual ii burrowers to individual stimuli, genetically-coded programmed behaviour developed and became dominant in the earliest Cambrian. These observations imply that increases in sensory and neural capacity accompanied skeletonization as a major factor in the Cambrian explosion of animal life. iii Statement of Co-Authorship While this thesis is substantially my own work, my supervisor has actively contributed to its development. A modification of Chapter 2 is currently in press with the Journal of Paleontology (due out in volume 88, March 2014), and is co-authored by Guy M. Narbonne who helped greatly in the development and editing of the manuscript. Chapter 3 is currently in preparation for submission to an international journal. Taxonomic Statement The systematic paleontology of the new Ediacaran genus described in this thesis does not constitute the official description of this taxon in accordance with the International Code of Zoological Nomenclature (fourth edition). The official description of this taxon will appear in a modified version of Chapter 3, which is currently being prepared for submission to an international journal. iv Acknowledgements I would like to extend my profound thanks to my supervisor, Guy Narbonne, for his mentorship through an undergraduate thesis and master’s thesis. His dedication and genuine interest in my project, even when out of the country, was extremely motivating. Beyond this, his scientific guidance, encouragement, and enthusiasm for my work has given me a confidence in my scientific work which will not be forgotten in my future endeavors. Special thanks goes to Sara Mason, who allowed me to assist her in the field, which first enchanted me to pursue scientific research of the Ediacaran. I would also like to thank both Ally Brown and Thomas Boag, who each braved remote camps and wildlife encounters with optimism and enthusiasm during their assistance in the field, making for very successful and enjoyable seasons. I would like to acknowledge all of my professors and colleagues from the time spent at Queen’s University. I am grateful for everything that I have learned, both in and out of the classroom, and for the fine examples of professors and scientists that have helped me learn what it is to be a geologist. I would also like to thank Erik Sperling, Louis Buatois, Gabriela Mángano, and Roy Plotnick for helpful comments during the publication process of Chapter 2. I would like to offer my sincerest thanks to my friends and family, especially my parents and Ted Matheson, for their endless positivity and support. To my parents, your encouragement of my interest in science from a young age helped me to get to where I am today. To Ted, your love and words of encouragement meant so much, especially during the more stressful moments that are involved in being a graduate student. v I would like to gratefully acknowledge the cooperation of the communities of Norman Wells and Tulita, and logistical assistance from Amy Newton and Canadian Helicopters. Fieldwork was carried out under scientific permits from Aurora Institute, NWT. This research was funded through NSERC Discovery grants, a Queen’s Research Chair to Guy M. Narbonne, the C. C. Reinhardt Fellowship, E. L. Bruce Memorial Scholarship, Queen’s Graduate Award and G. N. L. Bowen Bursary, and continual support from Guy M. Narbonne. vi Table of Contents Abstract ............................................................................................................................................ ii Statement of Co-Authorship ........................................................................................................... iv Taxonomic Statement ..................................................................................................................... iv Acknowledgements .......................................................................................................................... v Table of Contents ........................................................................................................................... vii List of Figures ................................................................................................................................. ix Chapter 1 Introduction .................................................................................................................. 1 1.1 The Ediacaran-Cambrian Biotic Succession .......................................................................... 1 1.2 Body Fossils: Diversification and Biomineralization ............................................................ 2 1.3 Trace Fossils: A Record of Behaviour ................................................................................... 5 1.4 The Ediacaran-Cambrian Succession in the Mackenzie Mountains ...................................... 7 Chapter 2 When Life Got Smart: the evolution of behavioural complexity through the Ediacaran and early Cambrian Of NW Canada ...................................................................... 12 2.1 Abstract ................................................................................................................................ 12 2.2 Introduction .......................................................................................................................... 13 2.3 Geological and Paleontological Setting ............................................................................... 16 2.4 Background to Foraging Behaviour ..................................................................................... 23 2.5 Microbial Grazing ................................................................................................................ 25 2.5.1 Undirected Horizontal Traces ....................................................................................... 28 2.5.2 Microscopic Curved and Contorted Burrows ............................................................... 30 2.5.3 Two-dimensional Avoidance Traces ............................................................................ 31 2.5.4 Three-dimensional Avoidance Burrows ....................................................................... 37 2.5.5 Directed Crossing Traces .............................................................................................. 39 2.5.6 Pseudo-spiral Traces ..................................................................................................... 40 2.5.7 Synthesis of Microbial Grazing .................................................................................... 41 2.6 Deposit Feeding ................................................................................................................... 42 2.6.1 Undirected Horizontal Burrows .................................................................................... 43 2.6.2 Irregular Networks ........................................................................................................ 46 2.6.3 Radiating Burrows .......................................................................................................
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