Turtle research

The fossil record preserves the responses of chelonians (turtles, tortoises and terrapins) to major environmental changes and extinctions. By studying these fossils we hope to better understand the potential impact of current threats to chelonian diversity.

We are producing the first comprehensive analysis of turtle, tortoise and terrapin biodiversity and distribution through time. 

The project aims to determine whether significant events in chelonian evolution coincide with major episodes of global environmental change. 

Project background

Chelonians are an immensely successful group of vertebrates that have endured for over 220 million years. They survived several major environmental changes:

  • global hot-house conditions in the Late Cretaceous and Eocene (and associated cooling events)
  • the end-Cretaceous mass extinction
  • post-Eocene global cooling trends
Why chelonians?

Chelonians are ideal for studying the biotic response of cold-blooded vertebrates to long-term environmental change. They:

  • inhabit all three major global ecosystems (marine, freshwater, terrestrial)
  • have an established taxonomy
  • are exceptionally common in the fossil record
  • have well-defined habitat preferences

Comparing groups of chelonians characteristic of a particular habitat or region can reveal the effects of long-term change on subsets of biodiversity. 

Chelonians are a globally threatened group. We can predict the impact of future climate change by studying their past responses to major environmental events.


We will undertake a comprehensive literature search to populate our database of chelonian occurrences in the Mesozoic and Paleogene fossil record. This includes data on depositional environments and preservation types. 

Statistical analysis

Using the database, we will construct estimates of global chelonian diversity through the Mesozoic and Paleogene. We also hope to clarify how these patterns of diversity differ among habitats and regions.

Using standard and newly developed statistical methods we aim to separate changes in diversity from noise resulting from uneven sampling and other biases in the fossil record. 

Comparing diversity patterns with climate data (such as mean annual temperature, precipitation rates) will show how changing environmental factors may have affected chelonian evolution.

Project team

Dr David B Nicholson

Dr Paul M Barrett 
Principal Investigator

Dr Kenneth G Johnson

Dr Daniella Schmidt
University of Bristol

Prof Paul Valdes
University of Bristol

Prof Margaret Collinson
Royal Holloway, University of London

Dr Alistair McGowan
University of Glasgow

Dr Patricia Holroyd
University of California, Berkeley

Dr J Howard Hutchinson
University of California, Berkeley


This project is funded by the Natural Environment Research Council (NERC).