Fossils of the Herefordshire and Chengjiang Lagerstätten

Our detailed understanding of the history of life relies on the fossil record, and most especially on the very rare fossil deposits that preserve not simply the hard parts of animals, but also their soft parts. Such exceptional preservation deposits, known as fossil Lagerstätten, tell us much more about ancient biotas than the normal shelly fossil record; they provide unique windows on past life.

The Chengjiang Lagerstätte, of Lower Cambrian age (c. 525 million years old), is contributing fundamentally to our understanding of the so-called Cambrian explosion event. This saw the first appearance in the fossil record of most of the major animal groups that make up global marine biodiversity present today. Especially notable is the earliest vertebrate, a jawless fish. Overall, the fauna represents the earliest, most complete animal community. More than 150 species have been recognised from the deposit. They occupy various ecological niches, and represent a range of feeding types, indicating that an elaborate ecosystem was already established at that time.

I was part of an international group of authors that produced, in 2004, the first English language book on the fauna, since when there have been numerous, often significant, fossil discoveries. The time is opportune for a new edition of this book, especially as Chengjiang was recently (2012) ratified as a UNESCO World Heritage Site. I am a member of an English-Chinese group of palaeontologists who will undertake this work, and my Leverhulme Fellowship in part involves researching and writing for it.

The Herefordshire Lagerstätte, of Silurian age (c. 425 million years old), is from a time for which very few soft-bodied faunas are known. The fossils from there are therefore of great importance in helping fill this gap in our knowledge of the history of life. The deposit contains fossils of small marine invertebrates that were engulfed in volcanic ash. The animals themselves soon rotted away, but their shapes were faithfully recorded by the ash and by crystals of calcite that grew within the resulting voids. These crystalline shapes now occur within nodules in the ash, and not only do the fossils exquisitely preserve entire animals, almost uniquely they are fully three-dimensional and not squashed flat. The fossils are retrieved from the rock by a physical-optical CT (computed tomography) technique that creates a ‘virtual fossil’ in the round, which can be rotated, even dissected, on the computer screen.

Full page photo jpg

Maotianoascus, a sea gooseberry (Ctenophore), Lower Cambrian, Chengjiang, Yunnan, China.

Haliestes a sea spider pycnogonid mid Silurian Herefordshire UK jpg

Haliestes, a sea spider (pycnogonid), mid-Silurian, Herefordshire, UK.

I am part of a team of researchers on the Herefordshire project, which is based in Oxford, and which also includes colleagues in Leicester, London (Imperial College) and Yale universities. Various Herefordshire arthropods, such as Haliestes, a sea spider, have already been studied. Other arthropods and members of closely related groups remain to be investigated, for example some trilobites, new crustaceans, a very rare fossil example of the parasitic tongue worms (pentastomids), and one of the modern land-dwelling velvet worms (onychophorans), plus other as yet unidentified forms. All these species are anticipated to be as scientifically significant as those already investigated. In addition, this research will contribute to syntheses of the composition, community structure and ecology of the Herefordshire fauna; enable better comparison of it with other exceptionally preserved faunas; and help give an unparalleled view of life on and above the sea bottom during Silurian times.

Professor Derek Siveter
University of Oxford