Monday, 4 March 2013

Tetrapod finds update


In this blog I will give an update on some of the vertebrate fossils the TW:eed team has found so far. This work has been undertaken by the vertebrate team at Cambridge, which consists of Jenny Clack, Tim Smithson, Ket Smithson and Sarah Finney. They have been busy picking through a huge amount of rock to expose the bones within.

The most common animals they have found are tetrapods, lobe-finned fish (rhizodonts), acanthodians (gyracanths) ray-finned fish (actinopterygians) and lungfish.

Tetrapods
Many tetrapod bones have been found during our autumn fieldwork season, many of which have never been seen before, so may belong to new tetrapod species. Below are photographs of some of the tetrapod bones: the maxilla (jaw), gastralia (scales from the underbelly region) and metapodials (toe bones). 

 
Fossil images are copyright of Jenny Clack, reconstruction copyright of Mike Coates. Please note that the reconstruction is of 'Ribbo' and does not directly relate to the bone specimens shown here.

Rhizodonts
Rhizodonts are an extremely large type of fish, members of the group of lobe-finned fishes which were ancestors to tetrapods (i.e. tetrapods evolved from these fish to be able to walk on land). Many bones have been found so far, some of which have a large range in size of the same bone. This indicates the presence of different aged individuals within the community. Below are photographs of some of the rhizodont bones: cleithra (part of the shoulder girdle) and postparietals (part of the skull).

 
Fossil images are copyright of Jenny Clack, reconstruction copyright of Mike Coates. Please note that the reconstruction is of Rhizodus and does not directly relate to the bone specimens shown here.

In summary, the vertebrate team at Cambridge are now finding lots of new material from our sites in Scotland, including completely new taxa. This will help us to understand how tetrapods and fish evolved following the end Devonian mass extinction, and fill in ‘Romer’s Gap’ in the fossil record. Great stuff!

Want to know more about tetrapod discoveries? Check out this paper by Jenny about the late Devonian Ichthyostega and it’s fascinating anatomy. Or for a less technical read, look at this BBC news article.

In other news, rock processing is progressing fairly rapidly (90 samples left to go), and microfossil picking is also progressing well. With my volunteer Tom’s help we are finding small pieces of plants, wood, fish, ostracods and bones. Tomorrow we will examine some material on the Scanning Electron Microscope to find out more.

Until next time
Carys

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