460-million-year-old well-preserved rare fossils unearthed in Wales

This one-of-a-kind fossil site provides an intriguing glimpse of marine life on Earth that existed during the Cambrian period (542-485 million years ago).
Mrigakshi Dixit
Reconstruction of the Castle Bank community.
Reconstruction of the Castle Bank community.

YANG Dinghua 

An unexpected fossil site containing unusually well-preserved marine specimens has been discovered at Castle Bank in Wales. 

This one-of-a-kind fossil site provides an intriguing glimpse of marine life on Earth that existed during the Cambrian period (542-485 million years ago). This part of Wales was covered in ocean million years ago, where myriad, tiny marine life forms thrived. 

This site has preserved a plethora of marine fossils, some of which belong to unidentified species with small bodies (only 1-3 mm long). That's why the team, led by the Chinese Academy of Sciences, dubbed it "Marine Dwarf World."

The findings can fill in the evolutionary gap

The uncovered fossils belonged to 150 species and were found preserved in rocks buried beneath the sea nearly 460 million years ago. This site is scientifically significant because it can provide a rare glimpse into the evolution of marine life after the Cambrian explosion about 500 million years ago. 

It is noted that during the Cambrian explosion (540m and 485m years ago), new life forms began to emerge, and even the ancestors of many modern animals began to evolve. 

“A new Burgess Shale-type fauna from the middle of this interval will help close this gap by answering questions about the animal shift from Cambrian fauna to Palaeozoic fauna and about the shift in ecosystems from the Cambrian style (which were similar across much of the world) to the much more diversified ecology we see today,” explained the official statement

Fossils preserved with internal organs

The fossils consist of well-preserved soft tissues as well as complete marine organisms, which are typically difficult to come by. Mainly, marine fossils unearthed from various parts of the globe consist of only hard parts such as shells and bones to date.

These new diverse fossils belong to various species, including arthropods such as crustaceans and horseshoe crabs, as well as worms, sponges, starfish, and others. Some well-preserved fossils also show the internal organs of small organisms, such as digestive systems, optic nerves, arthropod limbs, and tentacles.

“In addition, the range of fossils also includes several unusual discoveries, from unexpectedly late examples of Cambrian animals looking like opabiniids (weird proto-arthropods with a long proboscis) and wiwaxiids (slug-like molluscs armored with scales) to tantalizing, unexpectedly early fossils that resemble modern goose barnacles, cephalocarid shrimps (which have no fossil record at all) and possibly even a marine relative of insects,” adds the press statement. 

Dr. Joe Botting and Dr. Lucy Muir discovered this new marine fossil assemblage in 2020 near Llandrindod, central Wales. During the lockdown, the couple went on a field trip to the 10-meter-wide quarry in Llandrindod, central Wales. 

The results have been reported in the journal Nature Ecology & Evolution. 

Study abstract:

Burgess Shale-type faunas are critical to our understanding of animal evolution during the Cambrian, giving an unrivalled view of the morphology of ancient organisms and the ecology of the earliest animal-dominated communities. Rare examples in Lower Ordovician strata such as the Fezouata Biota illustrate the subsequent evolution of ecosystems but only from before the main phase of the Great Ordovician Biodiversification Event. Later Ordovician Konservat-Lagerstätten are not directly comparable with the Burgess Shale-type faunas as they do not represent diverse, open-shelf communities, limiting our ability to track ecological development through the critical Ordovician biodiversification interval. Here we present the Castle Bank fauna: a highly diverse Middle Ordovician Burgess Shale-type fauna from Wales (UK) that is directly comparable with the Burgess Shale and Chengjiang biotas in palaeoenvironment and preservational style. The deposit includes animals with morphologies similar to the iconic Cambrian taxa Opabinia, Yohoia and Wiwaxia, combined with early examples of more derived groups such as barnacles. Many taxa such as kinorhynchs show the small sizes typical of modern faunas, illustrating post-Cambrian miniaturization. Castle Bank provides a new perspective on early animal evolution, revealing the next chapter in ecosystem development following the Chengjiang, Burgess Shale and Fezouata biotas.

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