Teeth and jaws: evolutionary emergence of a model organogenic system and the adaptive radiation of gnathostomes
Lead Research Organisation:
University of Leicester
Department Name: Geology
Abstract
More than 99.8% of living vertebrates are gnathostomes (vertebrates with jaws and teeth), and the origin of gnathostomes thus represents one of the most significant episodes in animal evolution. Teeth and jaws are widely held to be the key innovation that underpinned the adaptive radiation of jawed vertebrates, and allowed them to drive their jawless relatives, which had dominated vertebrate communities for the preceding 150 Myr, to extinction. Three recent discoveries challenge this long-cherished hypothesis: (a) 'teeth' evolved before jaws (thus tooth and jaw origin was not coordinated); (b) all lineages of jawed vertebrates were primitively toothless, and each evolved teeth independently; and (c) a major revision of evolutionary relationships of the most primitive jawed vertebrates has overturned the long established view that two principal groups of extinct primitive jawed vertebrates - placoderms and acanthodians - are in fact many different groups that are related by degree to the living jawed vertebrates - sharks and bony fishes (that latter including our own evolutionary lineage). This is not merely a phylogenetic nicety: it reveals a protracted and sequential construction of the bodyplan of crown-gnathostomes, including the assembly of the supposed evolutionary innovation of jaws and teeth. The impact of these discoveries is felt well beyond evolutionary biology because teeth are a core model for understanding the general principles of organ development, and these theories rely heavily upon the assumption that all vertebrate teeth evolved from a common ancestor and that sharks can be taken to represent the primitive condition. This no longer appears to be the case and our understanding of the evolution of this model organogenic system is in disarray. Thus, we are faced with a major shift in our understanding, requiring a complete reformulation of explanations of the origin of jawed vertebrates, but existing data are not up to the job. We know nothing concerning the function of 'teeth' in jawless vertebrates, and feeding in toothless jawed vertebrates has not been the subject of critical analysis. How feeding in later, toothed representatives of each lineage compared is unknown and, as a consequence, so is the ultimate cause of the gnathostome radiation. Furthermore, we do not even know when the radiation occurred: coincident with the origin of jaws, with the later convergent acquisition of teeth, or neither? We do not even know confidently whether the new hypothesis of convergent tooth evolution is correct, because there are no comprehensive evolutionary trees that test whether toothless forms appeared near the base or higher up within gnathostome lineages, and our initial investigations have revealed that these 'toothless' forms appear to possess kosha teeth. We propose to tackle this problem through an innovative multidisciplinary research programme combining the unique and complementary expertise of the four investigators with cutting edge, hi-tech methods. Existing hypotheses of jaw and tooth function among extinct jawless and basal jawed vertebrates will be tested using tooth microwear analysis, which provides direct evidence of how vertebrates ate and the nature of their food. We will use sophisticated and powerful computer models to determine how jaws and teeth were engineered to fit their function. These models will use high-resolution data from advanced Synchrotron Radiation X-ray Tomographic Microscopy. A kind of super-CAT-scanning, this will reveal in 3D the internal microstructure of 'jawless teeth', teeth and jaws, allowing us to understand how they grew and were replaced. This in turn will allow us to test hypotheses concerning the evolution of tooth development. Our research will allow us to provide new, robust explanations for the emergence and radiation of jawed-vertebrates and - arguably more importantly - the evolutionary origin of a model developmental module: the jaw-tooth system
Organisations
People |
ORCID iD |
Mark Purnell (Principal Investigator) |
Publications
Jones D
(2012)
Non-destructive, safe removal of conductive metal coatings from fossils: a new solution
in Palaeontologia Electronica
Purnell M
(2012)
Quantitative three-dimensional microtextural analyses of tooth wear as a tool for dietary discrimination in fishes.
in Journal of the Royal Society, Interface
Jones David
(2012)
Non-destructive, safe removal of conductive metal coatings from fossils: a new solution
in PALAEONTOLOGIA ELECTRONICA
Purnell MA
(2013)
Within-guild dietary discrimination from 3-D textural analysis of tooth microwear in insectivorous mammals.
in Journal of zoology (London, England : 1987)
Martinez-Perez, C
(2014)
FUNCTIONAL ANALYSIS AND ONTOGENY IN THE EARLIEST GNATHOSTOMES
in Abstracts of the 4th INTERNATIONAL PALAEONTOLOGICAL CONGRESS
Gill PG
(2014)
Dietary specializations and diversity in feeding ecology of the earliest stem mammals.
in Nature
Martínez-Pérez C
(2014)
Finite element, occlusal, microwear and microstructural analyses indicate that conodont microstructure is adapted to dental function
in Palaeontology
Purnell M
(2015)
3D tooth microwear texture analysis in fishes as a test of dietary hypotheses of durophagy
in Surface Topography: Metrology and Properties
Goodall RH
(2015)
Accuracy and precision of silicon based impression media for quantitative areal texture analysis.
in Scientific reports
Description | More than 99.8% of living vertebrates are gnathostomes (vertebrates with jaws and teeth), and the origin of gnathostomes thus represents one of the most significant episodes in animal evolution. Teeth and jaws are widely held to be the key innovation which underpinned the adaptive radiation of jawed vertebrates, and testing this hypothesis - that the evolution of jaws and teeth is correlated with increased dietary versatility and/or specialization - is fundamental to understanding how modern vertebrates evolved. We have developed a new approach to analysis of diet and feeding in extinct aquatic vertebrates. This is based on quantitative analysis of the microscopic 3D textures that develop on tooth surfaces as they are worn. By analysing living fishes, we have established that these textures differ between fish that eat different foods and which occupied different trophic niches. Applying the same approach to extinct fishes, including early gnathostomes, we can test for differences in feeding and diet. Our analysis reveals that placoderm species had much great dietary range than would be expected from analysis of tooth morphology (they were not dietary specialists) and that different species of acanthodian had different diets. This allows us to test and refute aspects of recent work that links tooth and jaw morphology to dietary adaptation during early vertebrate evolution. |
Exploitation Route | potential for public engagement activities and museum exhibits based around new view of how diet changed during early vertebrate evolution. mainly academic beneficiaries, reached through conference presentations and publication in journals |
Sectors | Environment |
Description | Work on the relationship between diet, tooth shape and tooth wear/microwear have formed the basis for talks to schools and for public engagement activities at national fossil festivals |
First Year Of Impact | 2016 |
Sector | Other |
Impact Types | Societal |
Description | NERC AST studenship |
Amount | £29,933 (GBP) |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 10/2012 |
End | 03/2016 |
Description | NERC CENTA DTP studenship (adams) |
Amount | £75,000 (GBP) |
Organisation | University of Leicester |
Sector | Academic/University |
Country | United Kingdom |
Start | 10/2017 |
End | 05/2021 |
Description | NERC Research Experience Placement |
Amount | £2,500 (GBP) |
Organisation | Natural Environment Research Council |
Sector | Public |
Country | United Kingdom |
Start | 07/2015 |
End | 09/2015 |
Description | Palaeontological Association undergraduate research experience bursary |
Amount | £1,600 (GBP) |
Organisation | Palaeontological Association |
Sector | Charity/Non Profit |
Country | United Kingdom |
Start | 07/2015 |
End | 09/2015 |
Title | new dietary proxy for analysis of aquatic vertebrates |
Description | developed a new approach, based on ISO international standards, for quantitative analysis of 3D microscopic textures of tooth wear, particularly in aquatic vertebrates, and use as a dietary proxy |
Type Of Material | Improvements to research infrastructure |
Year Produced | 2014 |
Provided To Others? | Yes |
Impact | none |
Description | School visit, Devon |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | interactive talk about tooth functional morphology and inference of diets to around 50 primary school children, Devon |
Year(s) Of Engagement Activity | 2016 |
Description | Society of Verebrate Palaeontology Workshop on textural analysis of microwear |
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 | lots of discussion, immediately after, during wider meeting, and subsequently by email not 'impact' focussed |
Year(s) Of Engagement Activity | 2014 |
Description | series of interactive talks in School (Bristol) |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | interactive workshop with primary school classes |
Year(s) Of Engagement Activity | 2018 |