A Remarkable Collection Of Fossil Birds From The Eocene

Written by Andrew Kitchener, Principal Curator of Vertebrates, National Museums Scotland.

In November 2021 National Museums Scotland acquired a remarkable collection of fossil bird skeletons dating from the Eocene, approximately 54.6-55 million years ago. The story of how this collection ended up in Edinburgh is a very long one and began more than 25 years ago. 

Please can you show me your collection of Eocene birds?” This was the question that greeted me when I first met a Mr Michael Daniels more than 25 years ago. Visiting the museum with his wife Pam and his daughter Caroline, who lived in Edinburgh, this meeting would be the beginning of a long friendship and long-term correspondence, which ended sadly in 2021. My answer was “Well I would love to show you our collection of Eocene birds, but we don’t have any.” Michael proceeded to tell me about his remarkable collection of several hundred skeletons and part skeletons that he had discovered in nodules of the London Clay, which had eroded out of the cliffs at Walton-on-the-Naze in Essex. In later years I visited Michael and Pam at their home and got to see the collection in its countless drawers and boxes in his study. I was astonished at the amazing variety of specimens of all shapes and sizes.  Many of the bones were minuscule, requiring great patience and skill to extract from the substrate.

Some of the many hundreds of fossil bird bones from Walton-on-the-Naze © National Museums Scotland

Michael Daniels was a passionate self-taught palaeontologist, who visited various fossil sites outside London and further afield in southern England from his home at Loughton near Epping Forest. He developed a more specialised interest in the Tertiary Eocene London Clay in the early 1970s, having been a founder member of the Tertiary Research Group in 1969. On retirement in 1985 he moved with his wife to Holland-on-Sea, so that he could pursue this interest at Walton-on-the-Naze.

Michael’s focus was the narrow Eocene horizon containing 54-million-year-old bird bones at Walton-on-the-Naze. Previously only very occasional stray bones had been found there, but Michael discovered hundreds of more-or-less complete skeletons, ranging in size from the fragmentary bones of a large archaic falcon ancestor similar in appearance to a predatory phorusrhacid or terror bird to the tiny hummingbird-sized skeletons of a swift. In all, Michael estimated that he drove 27,000 miles and walked 1,590 miles on 640 field visits to Walton-on-the-Naze to collect 15 tonnes of London Clay. He then took another 600 hours or 150 days to painstakingly prepare more than 700 fossil bird skeletons. 

Michael Daniels making another discovery at Walton-on-the-Naze © Bill George

Michael took great pride in his collection, which he documented and analysed in great detail. He sourced the skeletons of living bird species to help him identify the fossil specimens. Michael developed his own system of 70 avian skeletal characters, which resulted in a total of 270 possible criteria, to score each skeleton and show how similar each was to a living bird species. Despite this, many birds were difficult to classify because they originated from near the beginning of the modern evolutionary radiation of birds and often have characters mixed together that are now found in different modern bird families. In the early Eocene the climate was much warmer than today. According to a recent study, global mean annual surface temperatures were up to 13°C warmer than late 20th century temperatures, so that the fauna from this site may have important lessons for today’s global climate change. Given this warmer climate, it is perhaps not surprising that the former huge diversity of bird species at Walton-on-the-Naze is more like what you would see in an Amazonian rainforest than the Essex of today.

Michael wondered whether a possible catastrophe caused the mass avian mortality at this site, exploring volcanic evidence and the possibility of an asteroid strike. Michael was particularly interested in the origin of some possible glass-like tektites he found at the Naze, which might be evidence of this impact catastrophe. Hopefully further research can settle this question, using the small samples of tektites in the collection.

The mandible of the holotype specimen of the diver Nasidytes ypresianus. © National Museums Scotland

Michael’s collection is of global importance and it rivals collections made from bird-rich sites at the Green River, Wyoming, USA, Messel in Germany also of Eocene age and Liaoning, China, which dates to the earlier Cretaceous period. What makes the Naze fossil birds so important is that they are preserved in three dimensions, whereas at other key localities they are squashed flat, and they also represent the early stages in the evolutionary radiation of modern birds. Michael worked with and/or was visited by several of the world’s leading avian palaeontologists, including Gerald Mayr, Alan Feduccia, Storrs Olson, Bob Chandler, Greg Tomlinson, Peter Houde, Cécile Mourer-Chauviré and Stig Walsh, Curator of Vertebrate Palaeontology at National Museums Scotland.

Vicen Carrió, geological conservator at National Museums Scotland, discussing the conservation of the fossil birds with Dr Gerald Mayr from the Senckenberg Research Institute. © National Museums Scotland.

There was much speculation as to where Michael would eventually find a home for his collection. It was only in early 2021 that he finally decided that he would bequeath his remarkable collection to National Museums Scotland. Sadly Michael died unexpectedly on 27th Sept 2021. We brought back the collection to Edinburgh on 11th November after a very long day carefully packing each specimen. We are very proud and honoured to host this collection, which will provide decades of research interest with many new species of fossil bird awaiting a formal scientific description. However, the collection provides an opportunity to study how this wide diversity of birds fits into the wider Eocene ecosystem of what we now call Walton-on-the-Naze. 

Although anonymously, Sir David Attenborough described Michael’s collection in The Life of Birds, where he singled out the “remarkable site” at Walton-on-the-Naze for providing “astonishing evidence of this swift and rich development” of bird evolution “yielding over six hundred specimens of ancient extinct birds.” The extent of this remarkable fossil assemblage is largely down to one man’s dedication, which Michael summed up in his own words in a short pencil note found recently “just a scrap of bone that proved to be bird … that strange but necessary wherewithal and element of obsessive crankiness to keep going and continue searching for 33 years”.

Upper and lower jaws of the holotype of the stem falcon Danielsraptor phorusrhacoides. © National Museums Scotland

Since arriving at National Museums Scotland, research on and curation of the collection has already begun. Michael requested, in particular, that Gerald Mayr of the Senckenberg Research Institute, Frankfurt am Main, be invited to work on the collection. In his two visits so far this year, a steady stream of research papers, describing new species, has appeared. These include a stem falcon, Danielsraptor phorusrhacoides, which resembled the South American caracara, the world’s earliest known diver or loon, Nasidytes ypresianus, which had a beak more like a coot’s and probably did not pursue fishes like modern divers, and a diurnal owl, Ypresiglaux michaeldanielsi. There are many more new species awaiting description and once this is complete, it will be possible to look at the entire avian community of this region during the early Eocene. The task of curation and conservation is formidable with at least 700 specimens listed so far. We look forward to working with Gerald Mayr and other palaeontologists to find out more about Michael Daniels’ remarkable collection.

Acknowledgement

I would like to thank David Bain for his help and hospitality in the transfer of Michael’s collection to the National Museum of Scotland.  I would also like to thank David and Bill George for sharing much of the biographical information and photos of Michael, which I have reproduced in this blog.

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