Tetrapod World: early evolution and diversity | TWeed

Ribbo reconstruction

Tetrapod World early evolution and diversity, or TWeed for short, is a new scientific research project studying fossils and environments from the Early Carboniferous period.

The TWeed project intends to fill in a significant gap in our understanding of how tetrapods moved from the water onto land.

Experts from the universities of Cambridge, Leicester and Southampton, the BGS and National Museums of Scotland are collaborating to study some newly discovered fossils that will help us learn more about the other animals and plants that existed in the Early Carboniferous and the environment in which these evolutionary changes took place.

Exhibition in 2016

RibboFossil Hunters: Unearthing the Mystery of Life on Land

Discover how life on earth moved from water onto land 360–345 million years ago through ground-breaking discoveries made in Scotland. This exhibition is based on research carried out by the Tweed Project.

When: 19 Feb – 14 Aug 2016. Where: Exhibition Gallery 2, Level 3, National Museum of Scotland. How much: Free!


Semi-articulated skeletal remains of a small tetrapod from the borders, named as 'Ribbo'; skull bones to the left, hind legs to the right

Romer's Gap. Life reconstruction of Eucritta by Dmitri Bogdanov. 
GNU Free Documentation licence.

The adaptation by limbed vertebrates (tetrapods) to life on land was an important step in the evolution of life on Earth, leading eventually to the appearance of humans.

The process began about 360 million years ago at the end of Devonian times. In the Late Devonian tetrapods were essentially aquatic and fish-like.

However, 20 million years later, tetrapods had evolved into fully terrestrial forms that occupied diverse habitats and ecological niches.

This 20-million-year period has remained almost unrepresented for fossil tetrapods and the hiatus has become known as Romer’s Gap.

Little is known therefore about how tetrapods evolved adaptations for life on land, the environments in which they did so, and the timing and sequence of the events.

These questions are now being addressed in a new 4-year project, which commenced in July 2012; funded by the Natural Environment Research Council.

The team, led by Jenny Clack from Cambridge University, brings together scientists from a wide range of disciplines from the universities of Cambridge, Southampton, and Leicester, the National Museums Scotland, and the BGS.

This project has been made possible by recent finds by palaeontologists Tim Smithson (University of Cambridge) and the late Stan Wood. There has also been some internationally significant tetrapod fossils in lower Carboniferous strata in south-east Scotland.

These localities are the only places, so far known in the world, where tetrapod fossils of such quality and quantity have been found within Romer’s Gap. Our team is the first to be given the opportunity to study them in detail and to begin to understand a crucial period of Earth history.

Aims of the project

The project aims to establish the biological, environmental and geological conditions during early Carboniferous times.

We will explore and explain the changes that laid the foundations for the emergence of modern fauna and flora, and when tetrapods evolved into diverse groups including predominantly terrestrial forms for the first time.

The BGS team of Dave Millward, Tim Kearsey and Melanie Leng will contribute to the understanding of the environments in which the animals lived and died, the conditions of deposition that preserved the fossils, and the precise times at which they did so.


millwardTWeed Website

Home of the TWeed Project and collaborators. Featuring the project framework, fieldwork news and project updates.

Tetrapod WorldTetrapod World

A weekly science research blog about the TWeed research project. Written by Carys Bennett a geoscientist from the University of Leicester. Carys also tweets as @tetrapodworld


Geoblogy15 million years of evolution gone missing? Who ya gonna call?

This blog is an introduction to the project written by scientists for the pleasure of everyone. Collaborators will be frequently posting with TWeed news and progress as it happens.


Contact Dr David Millward for more information on TWeed.