Gnathostome dental pattern and the evolution of chondrichthyan dentitions
Lead Research Organisation:
Birkbeck, University of London
Department Name: Earth and Planetary Sciences
Abstract
One of the most significant vertebrate innovations was the evolution of jaws, and on these jaws, teeth arranged into functional dentitions. These dentitions allowed vertebrates to radiate into a number of major groups, including sharks (Chondrichthyes) and bony fishes (Osteichthyes). Along with these are a variety of fossil groups whose dentitions have been difficult to understand and interpret. Because these fossil groups are closer to the origin of jaws and teeth, it is crucial that we try to better understand how their dentitions evolved.
One way to do this is to study how the dentitions of living groups developed and then apply these observations, as far as possible, to the development of dentitions in fossil taxa. The group Osteichthyes includes well-known fish such as the tuna, salmon, seahorse, coelacanth, lungfish and also tetrapods. Osteichthyan dentitions have been intensely studied in recent years, and we even understand what genes are involved in producing these dentitions. Despite this, even within this group we know nothing about tooth development of more primitive osteichthyans, such as the paddlefish and gar. As well, and perhaps somewhat surprisingly, we know very little about how genes control development of shark and ray dentitions. The goal of our project is to study development in a broad range of chondrichthyans to find common developmental characters of these dentitions that can be compared to osteichthyan dentitions and in the future, to the more primitive, problematic fossil taxa.
Shark teeth are plentiful in the fossil record and features they show are important in identifying different species. Chondrichthyans show a wide variety of dentitions, ranging from large numbers of almost microscopic teeth along the jaw (in filter-feeding sharks such as Rhincodon, the Whale shark), to the pavement-like dentition in rays, to a dentition in which teeth change along the jaw from biting to crushing (Heterodontus, the Port Jackson shark). This diversity has made it difficult to find common patterns of dentition development that could be used to compare to the problematic fossil vertebrates mentioned above. Sharks and rays also possess other 'tooth-like' structures such as the gill rakers in the filter-feeding basking shark Cetorhinus and 'teeth' along the rostrum of sawfish and sawsharks.
Our project will study specimens of a wide range of modern sharks and rays of different growth stages in order to investigate the patterns of tooth development within the jaws and changes in the number and shape of teeth during growth. A number of exceptionally well-preserved fossils will also be studied in order to place the modern forms within a wider context within the Chondrichthyes. Additionally, we will study embryos of a shark, ray and a basal bony fish and will record the genes controlling their tooth development that will allow us to compare underlying mechanisms of the formation of teeth in all vertebrates.
One way to do this is to study how the dentitions of living groups developed and then apply these observations, as far as possible, to the development of dentitions in fossil taxa. The group Osteichthyes includes well-known fish such as the tuna, salmon, seahorse, coelacanth, lungfish and also tetrapods. Osteichthyan dentitions have been intensely studied in recent years, and we even understand what genes are involved in producing these dentitions. Despite this, even within this group we know nothing about tooth development of more primitive osteichthyans, such as the paddlefish and gar. As well, and perhaps somewhat surprisingly, we know very little about how genes control development of shark and ray dentitions. The goal of our project is to study development in a broad range of chondrichthyans to find common developmental characters of these dentitions that can be compared to osteichthyan dentitions and in the future, to the more primitive, problematic fossil taxa.
Shark teeth are plentiful in the fossil record and features they show are important in identifying different species. Chondrichthyans show a wide variety of dentitions, ranging from large numbers of almost microscopic teeth along the jaw (in filter-feeding sharks such as Rhincodon, the Whale shark), to the pavement-like dentition in rays, to a dentition in which teeth change along the jaw from biting to crushing (Heterodontus, the Port Jackson shark). This diversity has made it difficult to find common patterns of dentition development that could be used to compare to the problematic fossil vertebrates mentioned above. Sharks and rays also possess other 'tooth-like' structures such as the gill rakers in the filter-feeding basking shark Cetorhinus and 'teeth' along the rostrum of sawfish and sawsharks.
Our project will study specimens of a wide range of modern sharks and rays of different growth stages in order to investigate the patterns of tooth development within the jaws and changes in the number and shape of teeth during growth. A number of exceptionally well-preserved fossils will also be studied in order to place the modern forms within a wider context within the Chondrichthyes. Additionally, we will study embryos of a shark, ray and a basal bony fish and will record the genes controlling their tooth development that will allow us to compare underlying mechanisms of the formation of teeth in all vertebrates.
Planned Impact
1) Academic Beneficiaries: see 'Academic Beneficiaries' page.
2) Citizen Scientists: Shark teeth/dentitions have a high degree of interest among amateur collectors/researchers. In the fossil fish collections at the Natural History Museum, London (NHM), shark teeth represent a large portion of donations to the collection, and general enquiries. This is due to the easy availability of relevant shark-bearing geological formations outside London. Our work will be of interest to these citizen scientists as it will provide new characters to help them identify and classify their fossil finds, and illustrate a new aspect to their fossils (ontogeny, or how teeth/dentitions develop through growth) that they may not have considered. In this way, our project will contribute to increasing public awareness and understanding of scientific issues. We will develop an outreach/learning packet that can be modified to meet the needs of these beneficiaries; our team members will use these and each plan to attend one internal (e.g., NHM Nature Live), and two external UK events per year of the grant, to better disseminate our research and increase the impact of our work (see role of 'virtual palaeontology', below). We can also reach citizen scientists via NHM websites such as 'Nature Plus' (http://www.nhm.ac.uk/natureplus/index.jspa) and KEEmu, where we can blog project progress, including strong visuals such as reconstructed CT-scans, histological images, gene expression results, etc.
3) Students (schools) and adult education: These beneficiaries will overlap with 'citizen scientists', but we will modify our outreach events to maximize our impact with these beneficiaries. After initial discussions, we could tailor our outreach packet for individual schools and curricula. For example, we would be more specimen-oriented (Recent shark jaws, histological slides, cleared and stained specimens) for a biology class. For a class interested in the technological side of our research, we could focus on CT-scanning (using images and videos on a portable laptop) and 3-D rapid prototyping (both aspects of outreach and education via 'virtual palaeontology', Rahman et al., 2012. Evo Edu Outreach DOI 10.1007/s12052-012-0458-2). By disseminating our results in this flexible, adaptive way, we will contribute to the scientific culture in the UK and Europe. Students could also access websites as above.
4) Museums, galleries and aquaria: Given the wide public interest in shark teeth/dentitions, our work will be beneficial to museums and galleries that may be able to incorporate our results into exhibitions or for use in museum talks or public engagement. For example, PI Johanson regularly contributes to NHM public engagement via 'Nature Live', 'Science Uncovered' and 'A-levels' schools programme. Project Partner Sansom has already liaised with the Sea Life Centre in Birmingham such that we will provide them a version of our outreach to use. The Sea Life Centre has a network throughout Europe providing opportunities for outreach in continental Europe as well (targeting facilities in Germany).
5) Staff working on this project: Staff will acquire important skills from either CT-scanning (NHM, KCL), including using the software needed to structurally render this data, or, analysis of gene expression patterns via in situ hybridization. These are highly mature technologies and used in a wide variety of research programs involving both fossil and extant specimens. In this way, our project will train and deliver highly skilled researchers and technicians. Additionally, the PDRA (Sheffield) will travel to the lab of Project Partner Marcus Davis (Kennesaw State University), having the opportunity to develop their skills and interact in a new lab environment. Our timeline suggests these benefits accrue within the first year with respect to the CT-scanning, and within the first two years for the molecular work.
2) Citizen Scientists: Shark teeth/dentitions have a high degree of interest among amateur collectors/researchers. In the fossil fish collections at the Natural History Museum, London (NHM), shark teeth represent a large portion of donations to the collection, and general enquiries. This is due to the easy availability of relevant shark-bearing geological formations outside London. Our work will be of interest to these citizen scientists as it will provide new characters to help them identify and classify their fossil finds, and illustrate a new aspect to their fossils (ontogeny, or how teeth/dentitions develop through growth) that they may not have considered. In this way, our project will contribute to increasing public awareness and understanding of scientific issues. We will develop an outreach/learning packet that can be modified to meet the needs of these beneficiaries; our team members will use these and each plan to attend one internal (e.g., NHM Nature Live), and two external UK events per year of the grant, to better disseminate our research and increase the impact of our work (see role of 'virtual palaeontology', below). We can also reach citizen scientists via NHM websites such as 'Nature Plus' (http://www.nhm.ac.uk/natureplus/index.jspa) and KEEmu, where we can blog project progress, including strong visuals such as reconstructed CT-scans, histological images, gene expression results, etc.
3) Students (schools) and adult education: These beneficiaries will overlap with 'citizen scientists', but we will modify our outreach events to maximize our impact with these beneficiaries. After initial discussions, we could tailor our outreach packet for individual schools and curricula. For example, we would be more specimen-oriented (Recent shark jaws, histological slides, cleared and stained specimens) for a biology class. For a class interested in the technological side of our research, we could focus on CT-scanning (using images and videos on a portable laptop) and 3-D rapid prototyping (both aspects of outreach and education via 'virtual palaeontology', Rahman et al., 2012. Evo Edu Outreach DOI 10.1007/s12052-012-0458-2). By disseminating our results in this flexible, adaptive way, we will contribute to the scientific culture in the UK and Europe. Students could also access websites as above.
4) Museums, galleries and aquaria: Given the wide public interest in shark teeth/dentitions, our work will be beneficial to museums and galleries that may be able to incorporate our results into exhibitions or for use in museum talks or public engagement. For example, PI Johanson regularly contributes to NHM public engagement via 'Nature Live', 'Science Uncovered' and 'A-levels' schools programme. Project Partner Sansom has already liaised with the Sea Life Centre in Birmingham such that we will provide them a version of our outreach to use. The Sea Life Centre has a network throughout Europe providing opportunities for outreach in continental Europe as well (targeting facilities in Germany).
5) Staff working on this project: Staff will acquire important skills from either CT-scanning (NHM, KCL), including using the software needed to structurally render this data, or, analysis of gene expression patterns via in situ hybridization. These are highly mature technologies and used in a wide variety of research programs involving both fossil and extant specimens. In this way, our project will train and deliver highly skilled researchers and technicians. Additionally, the PDRA (Sheffield) will travel to the lab of Project Partner Marcus Davis (Kennesaw State University), having the opportunity to develop their skills and interact in a new lab environment. Our timeline suggests these benefits accrue within the first year with respect to the CT-scanning, and within the first two years for the molecular work.
People |
ORCID iD |
Charles Underwood (Principal Investigator) |
Publications
Meredith Smith M
(2018)
Development and evolution of tooth renewal in neoselachian sharks as a model for transformation in chondrichthyan dentitions.
in Journal of anatomy
Rasch LJ
(2016)
An ancient dental gene set governs development and continuous regeneration of teeth in sharks.
in Developmental biology
Rasch LJ
(2020)
Development and regeneration of the crushing dentition in skates (Rajidae).
in Developmental biology
Smith MM
(2015)
Early development of rostrum saw-teeth in a fossil ray tests classical theories of the evolution of vertebrate dentitions.
in Proceedings. Biological sciences
Underwood C
(2016)
Cutting blade dentitions in squaliform sharks form by modification of inherited alternate tooth ordering patterns.
in Royal Society open science
Underwood CJ
(2015)
Development and evolution of dentition pattern and tooth order in the skates and rays (batoidea; chondrichthyes).
in PloS one
Welten M
(2015)
Evolutionary origins and development of saw-teeth on the sawfish and sawshark rostrum (Elasmobranchii; Chondrichthyes).
in Royal Society open science
Description | The teeth of stars and rays are fundamentally different to the denticles despite their similarity in form, differing in patterning and replacement. Shark and ray teeth are produced within the embryo in an alternate pattern. In some sharks the alternate pattern is modified into apparent single row replacement by either differential tooth production along the jaw or loss of tooth positions. The first teeth of some species have the same number of tooth positions as adults, in some rays there are 2 teeth in the first row with additional teeth added with each tooth row. In rays with reduced teeth numbers, the wide teeth are modified midline teeth that get wider in successive rows. The gene control of shark and ray teeth is similar to that in other vertebrates, even though the teeth have a different mode of development and replacement. Tooth-like structures on the rostrum of some sharks and rays are not teeth but modified denticles. |
Exploitation Route | Some of the publications from this are now standard texts used in discussions of tooth development and evolution across vertebrates. |
Sectors | Environment,Culture, Heritage, Museums and Collections |
Description | Findings have appeared in the general media in these three blogs: http://news.sciencemag.org/biology/2015/09/sawfish-teeth-didn-t-pave-way-modern-chompers?utm_source=social_media&utm_medium=hootsuite&utm_campaign=standard http://blogs.plos.org/paleocomm/2015/10/30/the-slasher-ray-an-extinct-fish-with-a-saw-like-nose/ http://derstandard.at/2000021649468/Wie-Seepferdchen-Papas-Schwangeren-aehneln-Ursprung-moderner-Zaehne-doch-nicht |
First Year Of Impact | 2015 |
Sector | Other |
Impact Types | Cultural |
Description | Evolution and Development of chondrichthyan dentitions |
Organisation | University of Vienna |
Country | Austria |
Sector | Academic/University |
PI Contribution | Chondrichthyan specimens, data including CT-scans, rendered CT-scans, images |
Collaborator Contribution | Chondrichthyan specimens including rare taxa from partner's Japanese colleague, data including CT-scans, rendered CT-scans |
Impact | oyal Society International Exchange grant submitted, in review Rendered CT-scans of fossil material to be used in upcoming publication and Society of Vertebrate Paleontology, Berlin (2014) |
Start Year | 2014 |
Description | 3 days of school visits, Tetherdown Primary, Muswell Hill |
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 | Activities based around fossils and modern shark and other animal remains; 1 hour per class in the school |
Year(s) Of Engagement Activity | 2016 |
Description | Blast from the Past, Isle of Wight |
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 | Specimens and videos for public audience |
Year(s) Of Engagement Activity | 2016 |
Description | Gnathostome dental pattern and the evolution of chondrichthyan dentitions: NHM scratchpad |
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 | Our NHM scratchpad (http://chondrichthyes.myspecies.info/) is currently our main webpage to disseminate information about our project, including images, upcoming events, and relevant publications. We also will store published data here. Our current research assistant will be developing another website to link to this, to increase our outreach potential This is our main portal to disseminate information to the public and scientific researchers. |
Year(s) Of Engagement Activity | 2014 |
URL | http://chondrichthyes.myspecies.info/ |
Description | Lyme regis Fossil Festival |
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 | Demonstrations with fossils, modern specimens and videos |
Year(s) Of Engagement Activity | 2015 |
Description | Lyme regis Fossil Festival |
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 | Specimens and videos for large audiences |
Year(s) Of Engagement Activity | 2016 |