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Arthropod Evolution during the Ordovician Radiation: Insights from the Fezouata Biota

Applicant Daley Allison
Number 179084
Funding scheme Project funding (Div. I-III)
Research institution Institut des sciences de la Terre Université de Lausanne
Institution of higher education University of Lausanne - LA
Main discipline Palaeontology
Start/End 01.06.2018 - 31.05.2022
Approved amount 1'203'234.00
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All Disciplines (2)

Discipline
Palaeontology
Paleontology (biol.)

Keywords (8)

Paleontology; Arthropods; Ordovician Radiation; Fossils; Fezouata Biota; Geology; Cambrian Explosion; Evolution

Lay Summary (French)

Lead
Les premières étapes de l'évolution des animaux, il y a plus de 450 millions d'années, ont pris la forme de deux radiations majeures - l'Explosion Cambrienne et la Biodiversification Ordovicienne. Le Fezouata Biota au Maroc est une localité fossile important qui se trouve exactement entre ces deux radiations. Ce projet examine les fossiles d'arthropodes du Fezouata Biota, afin de mieux comprendre leur écologie et leur liens évolutifs avec les arthropodes modernes tels que les araignées et les crabes.
Lay summary

Contenu et objectifs du travail de recherche

Les fossiles du Fezouta Biota sont importants car ils préservent les tissus mous - tels que les yeux, la peau, et les organes internes - à côté des parties indurées telles que les coquilles. Ce projet utilisera ces fossiles exceptionnellement préservés pour comprendre l’évolution des premiers animaux, tous de formes bizarres, vers les groupes vivants aujourd'hui. Dans un premier temps, de nouveaux arthropodes fossiles, y compris des limules et des trilobites, seront décrits, et étudies à l’aide de nouvelles méthodes d'imagerie utilisant des lumières ultraviolette et infrarouge, ainsi que des rayons X. La deuxième phase examinera comment ces fossiles sont liés aux arthropodes modernes, en utilisant l'analyse phylogénétique pour construire des arbres évolutifs basés sur leur anatomie. La phase finale, et la plus innovante, développera de nouveaux modèles mathématiques pour étudier le développement et les stratégies de reproduction de ces arthropodes éteints.

 

Contexte scientifique et social du projet de recherche

Cette recherche fondamentale contribue à la communauté scientifique en apportant de nouvelles méthodes pour l'imagerie de fossiles et pour l’étude de l'écologie des animaux disparus. Ce projet met l’accent sur la richesse des données fossiles, et comment elles peuvent être utilisées pour décrypter l’évolution de la vie.

Direct link to Lay Summary Last update: 16.05.2018

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Abstract

Over 99% of all species that ever existed are now extinct, and the <1% of species alive today are the result of hundreds of millions of years of evolution. Many fields in evolutionary biology, developmental biology, ecology, and molecular phylogenetics have made great advances examining evolutionary processes using extant taxa, and yet this work necessarily focuses on the <1% represented by living animals. To access the other >99%, the fossil record must be critically interrogated to bring palaeontology to the forefront of a modern synthesis on evolutionary studies. The animal fossil record holds a staggering wealth of information on the radiations and extinctions that shaped the morphological diversity of modern ecosystems. Two such radiations, the Cambrian Explosion and the Ordovician Radiation, occurred at the early stages of animal evolution, and established the overall organisation of animal body plans that persist into the modern day. Yet the interplay between these two events is the subject of debate, with no clear answer as to how they are related, and why there are such large differences in the type, diversity and abundances of taxa between them. Using exceptionally preserved arthropod fossils of the Fezouata Biota, this project addresses the fundamental question:What evolutionary dynamics govern major faunal turnovers, such as that seen in the transition from the Cambrian Explosion to the Ordovician Radiation?The Fezouata Biota is a recently discovered locality in Morocco that produces exceptionally preserved, open marine, soft-bodied fossils and mineralised taxa. Its early Ordovician age places it exactly between the Cambrian Explosion and Ordovician Radiation evolutionary events, and it is unique in the world for preserving the typical elements of both animal communities together. It is ideally suited to provide the crucial data needed to understand the dynamics of faunal turnovers, and this project interrogates the Fezouata Biota fossil record by addressing three main research objectives: What arthropod taxa characterise this fossil locality? New taxa of horseshoe crabs, trilobites, radiodontans and bivalved arthropods will be described using standard paleontological techniques (e.g. photography, camera lucida drawings) and by developing new imaging and analysis methodologies for enhancing contrast between anatomical features, such as bandpass emission imaging, spectro-imaging and elemental mapping. What are the affinities and interrelationships of the new arthropods? The new fossil taxa will be coded into a morphological character matrix and subjected to phylogenetic analyses in order to determine their affinities and produce robust trees of arthropod relationships, including both stem-lineage and crown-group taxa. What can data on arthropod moulting tell us about population dynamics? Life history strategies of extinct arthropods, including trilobites, horseshoe crabs and radiodontans, will be determined using an innovative suite of models that incorporate data describing arthropod moulting and ontogeny, as well as information on the preservation conditions of the fossil locality. By comparing the life history strategies and evolutionary relationships of Cambrian taxa that go extinct shortly after the Fezouata Biota with those of Ordovician taxa that go on to increase in diversity and abundance, this project will ultimately reveal the evolutionary dynamics that govern the faunal turnover between the Cambrian Explosion and Ordovician Radiation. This project also establishes new methodologies for imaging fossils and evaluating the life history strategies of extinct arthropods, and the research results will have wide-reaching impacts for palaeontologists, evolutionary biologists, and anyone seeking to understanding how major evolutionary radiations established the diversity of animal life seen today.
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