THE MID-PALAEOZOIC BIOTIC CRISIS: SETTING THE TRAJECTORY OF TETRAPOD EVOLUTION

Lead Research Organisation: NERC British Geological Survey
Department Name: Geology & Regional Geophysics

Abstract

This project will shed light on a key stage in the evolution of life on Earth. The advent onto land of limbed vertebrates (tetrapods) was an event that shaped the future evolution of the planet, including the appearance of humans. The process began about 360 million years ago, during the late Palaeozoic, in the early part of the Carboniferous Period. Within the 20 million years that followed, limbed vertebrates evolved from their essentially aquatic and fish-like Devonian predecessors into fully terrestrial forms, radiating into a wide range of body forms that occupied diverse habitats and ecological niches. We know this because we have an adequate fossil record of the earliest limbed vertebrates from the Late Devonian, contrasting with the terrestrial forms that lived significantly later in the Early Carboniferous, about 340 million years ago. It is also clear that a mass extinction event occurred at the end of the Devonian, following which life on land and in fresh water habitats had to be re-established. Unfortunately, the formative 20 million years from the end of Devonian times has remained almost unrepresented for fossil tetrapods and their arthropod contemporaries. Thus, we know little about how tetrapods evolved adaptations for life on land, the environments in which they did so, and the timing or sequence of these events. The evolutionary relationships among these early tetrapods and how they relate to modern forms are also unclear and controversial as a result of this lack of fossil information. The entire fossil hiatus has been called 'Romer's Gap' after the American palaeontologist who first recognized it. Now, for the first time anywhere in the world, several fossil localities representing this period have been discovered in south-eastern Scotland. They have already provided a wealth of new fossils of tetrapods, fish, invertebrates and plants, and our team is the first to have the opportunity to study this material and the environmental, depositional, and climatic context in which this momentous episode took place. We have a number of major aims. The existing fossil material will form a baseline for this study, but the project will augment this by further excavating the richest of the sites so far found and subjecting it to a detailed archaeological-style analysis. We will collect from other recently recognized sites and explore for further sites with relevant potential. The fossil material will be described and analysed using a range of modern techniques to answer many questions related to the evolution of the animals and plants. Not only that, using stratigraphical, sedimentological, palynological, geochemical and isotopic data, we will establish the conditions of deposition that preserved the fossils, the environments in which the organisms lived and died, and the precise times at which they did so. We will drill a borehole that will core through the entire geological formation in which these fossils have been found. Using this, we will integrate data from our fossil sites using the signals provided by the sedimentary record to build a detailed time line showing in which horizons the fossils were found, the age of each occurrence and their sequential relationship. We will compare and correlate our data with that from contemporaneous deposits in Nova Scotia, the only other locality with information sufficiently rich to be meaningful. Our data will allow us to infer changes to the environment and the evolutionary trajectories of the animals and plants during the deposition of this formation, covering the 20 million years following the end-Devonian mass extinction. Comparison with similar data for the Late Devonian will allow us to chart the changes around the time of the mass extinction, to infer its causes and consequences, and obtain a detailed record of exactly how changes to the environment correlated with changes to the fauna and flora.

Planned Impact

The earliest Carboniferous (Tournaisian) interval (360-340 Ma) has long formed a 'bottleneck' in studies of the evolution of terrestrial ecosystems, and particularly the earliest evolution of terrestrial tetrapods, because of the almost complete lack of fossil evidence from this key time. We are now able to populate this hiatus in fossil data as a result of recent discoveries in Scotland, and to place these specimens in a palaeoecological and stratigraphic context.
Given the current paucity of data previously available for study of the faunas and floras from this time, and the profound changes to terrestrial ecosystems that took place then, we fully expect our results to be literally and metaphorically ground breaking. The material we will discover and describe will be of international significance, and enhance the reputation of the UK as a centre of excellence for Palaeozoic tetrapod fossils and their study. We anticipate publication in high profile journals including Science and Nature. Our palaeontological results will benefit interrelated disciplines from anatomists through molecular phylogeneticists to palaeoecologists. Biomechanics of locomotion, feeding, and breathing will gain from the new insight into the basal anatomical conditions at the onset of terrestriality. Studies of the evolutionary development of skeletal systems, and the timing of key innovations in tetrapod morphological adaptations will use our findings. Molecular phylogenies will benefit from new calibration points for the origins of the tetrapod and actinopterygian crown groups. The geological aspects of the proposal will benefit those modelling ancient climates in deep time, environmental and sedimentary systems, and their influence on and relationship to key evolutionary events. The refined stratigraphical, isotopic and palynological data that our studies provide will augment the, so far, relatively poorly known picture of this key period. Our comprehensive dataset from the earliest Carboniferous of Scotland will provide a future standard of comparison for contemporary deposits in other parts of the world. The industry-standard geophysical log data will be of interest to petrophysicists in academia and their industry partners, from including civil engineers, the construction industry and the hydrocarbon industries, who are studying the characterisation and prediction of physical properties in UK rock formations. As a team, we are particular well placed for high impact in the press and other media, with two members situated in nationally and internationally renowned museums, and with close links to others. Both institutions have professional in-house officers who deal with outreach on a continuing basis. Our experience talking to media representatives, the general public and other non-academics including people local to our sites, suggests that this project is of wide public interest and appeal.
 
Description 5 new tetrapod (4-limber vertebrate animals) taxa have been named and at least another 7 taxa found but are too incomplete to name. Romer's Gap has been proved to be a collection failure.
The early Carboniferous rock record shows an abundance and diversity of fossil soils that indicate that the floodplain was covered by a mosaic of habitats from marsh through to forest. The diversity of habitats present may have been a factor in allowing the earliest terrestrial tetrapods to adapt to life on land.
Exploitation Route Education in understanding how and why vertebrates adapted to life on land, a critical move that ultimately led to humans.
Sectors Education,Culture, Heritage, Museums and Collections,Other

URL http://tetrapods.org/
 
Title Norham borehole rock samples and fossils 
Description All samples of rocks, thin sections, palynological preparations, isotope analysis and fossils from the Norham borehole are entered into existing database managed by the National Geological Repository. Detailed information on the samples are kept in project research databases and made available to Consortium partners. 
Type Of Material Database/Collection of data 
Provided To Others? No  
Impact Samples taken from the cores are being analysed and interpreted by BGS team members and by researchers from Consortium partners. 
 
Description Articles in Scotland on Sunday Newspaper, Berwick Advertiser and Geodrilling International 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact The press release announcing the start of drilling a borehole as part of the TWeed project was picked up by the Scotland on Sunday and published 7 April 2013. Lively interview with the science reporter. Also picked up by the local Berwick Advertiser published 12 April 2013. Article published in the drilling industry journal Geodrilling International.

Several people got in touch to find out more information.
Year(s) Of Engagement Activity 2013
 
Description BGS Science showcase at Our Dynmaic Earth 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Manned display of posters and fossil vertebrate material; queations and discussions with public
Year(s) Of Engagement Activity 2016
 
Description Edinburgh Geological Society field trip 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Field trip to Burnmouth for members of the Edinburgh Geological Society, showing science discovered during project
Year(s) Of Engagement Activity 2015
 
Description Field workshop for ICDP science strategy board 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Significant discussion; expansion of awareness of science topic

None
Year(s) Of Engagement Activity 2015
 
Description Fossil Day at Our Dynamic Earth, Edinburgh 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Much interest and many questions from members of the public including children. People were encouraged to participate in the 'Scottish Fossil Five Poll' to find Scotland's top 5 fossils.

In creased voting in Fossil Five Poll
Year(s) Of Engagement Activity 2015
 
Description Geoblogy article on Fossil Hunter's exhibition 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A short blog at the start of the Fossil Hunters exhibition at the National Museums Scotland explaining the project work on unearthing the mystery of life on land. Exhibition lasts from 19 Feb until 14 August 2016.
Year(s) Of Engagement Activity 2016
URL http://britgeopeople.blogspot.co.uk/
 
Description Introduction to TWeed project and Norham cores to NERC Knowledge Exchange Network 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Discussion and interest; received request for image of some of the cores.

None noted
Year(s) Of Engagement Activity 2013
 
Description Open Day at British Geological Survey, Murchison House Edinburgh 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Posters and display of fossils and rocks from the project explained to the visiting public. Many questions and discussions on the the early evolution of tetrapods and the environments they occupied.

Received offers of help in a forthcoming excavation from amateur geologists and interested persons.
Year(s) Of Engagement Activity 2012,2013,2014
 
Description Oral presentation and core workshop Yorkshire Geol Soc 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact A full day event involving a core workshop and 4 talks. BGS team organised and co-led the core workshop and presented 1 talk. Much interested discussion after formal talks and on a one-to-one basis.

None
Year(s) Of Engagement Activity 2015
 
Description Oral presentation at IGCP596 SDS meeting Brussels 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Sparked questions and discussion

Good feedback and ideas for further investigation
Year(s) Of Engagement Activity 2015
 
Description Presentation and core workshop using Norham borehole experience to Neftex staff 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Shared experience of drilling planning and logistics; followed by core logging exercise for participants to understand the principles of core logging - much discussion.

None noted.
Year(s) Of Engagement Activity 2013
 
Description Scotland's Fossil Five Poll 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact A national poll to find Scotland's favourite fossil. Organised and run by the Scottish Geodiversity Forum through their website and the national press. 'Early Carboniferous Tetrapods' was voted 3rd.

Increased awareness in Scotland of Romer's Gap and of the current research programme.
Year(s) Of Engagement Activity 2015
 
Description Talk to Burnmouth (Berwickshire ) community 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Very lively question and discussion afterwards.

After my talk request made for another talk later in the project and for a poster display for the Burnmouth community centre.
Year(s) Of Engagement Activity 2014
 
Description Talk to Edinburgh Geological Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Part of Edinburgh Geological Society talks programme, informing members of research activity, followed by discussion
Year(s) Of Engagement Activity 2016
 
Description Talk to Edinburgh Geological Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Very lively questions and discussion.

Recurring interest in project progress at future meetings.
Year(s) Of Engagement Activity 2013
 
Description Talk to Edinburgh Geology Group of U3A 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Presentation to the Edinburgh geological group of the University of the Third Age (U3A)
Year(s) Of Engagement Activity 2015
 
Description Talk to NERC Earth System Science Spring School 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Talk was followed by lively discussion

None noted
Year(s) Of Engagement Activity 2013
 
Description Talk to Open University geological society meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Undergraduate students
Results and Impact 200+ attended a symposium for undergraduate Open University geology students; attracted lost of questions afterwards.
Year(s) Of Engagement Activity 2017