Llwygarua suzannae: An Echiuran Worm from the Middle Ordovician Castle Bank Biota of Wales.

Echurian Worms, or Spoonworms, are a group of Worms so morphologically distinctive that they were long thought of as being a separate phylum, although genetic analysis has shown them to be Polychaete Annelids, closely related to Capitellids. The group have a limited fossil record, with the oldest fossil considered to plausibly belong to the group being Coprinoscolex ellogimus, from the Carboniferous Mazon Creek Biota of North America.

In a paper published in the journal Acta Palaeontologica Polonica on 29 December 2023, Joseph Botting of the Nanjing Institute of Geology and Palaeontology and the Department of Natural Sciences at Amgueddfa Cymru-National Museum Wales, and Lucy Muir, also of the Department of Natural Sciences at Amgueddfa Cymru-National Museum Wales, describe a new species of Echiuran Worm from the Middle Ordovician Castle Bank Biota of Wales.

The new species is named Llwygarua suzannae, where 'Llwygarua' means 'love spoon' in Welsh, a reference to the carved wooden spoons traditionally given as tokens of love in Wales, and 'suzannae' honours Suzanne Douel, a retired biology teacher who has supported research on the Castle Bank fauna since its discovery.

The species is described from two specimens from the Castle Bank locality, near Llandrindod in Powys, Wales. These have a number of key features associated with Echiuran Worms, including the spoon-like proboscis, a diagnostic muscle-band arrangement, anterior setal pair and the presence of a differentiated caudal region.

Recent Thalassematid Echiuran (A) and a fossil equivalent (B). (A) ?Ochetostoma sp., highlighting significant features for comparison with the fossils, typical length 10–20 cm. (B) Holotype of Llwygarua suzannae from the Darriwilian (Middle Ordovician) of Castle Bank, Wales, UK, NMW.2021.3G.99 showing overall specimen in slightly oblique lateral view (B₁₂); enlargement with anterior ventral part of trunk (B₄), showing one anterior seta (white arrow) and probably second seta (black arrow); detail of proboscis in cross-polarised light (B₅), showing reticulate structure and anterior projections adjacent to midline; central region of trunk with distinctive wrinkling of cuticle in response to compression (B₂), and proboscis in plane-polarised light (B₃), with anterior projections arrowed. Botting & Muir (2023).

Llwygarua suzannae shows a remarkable degree of similarity to modern Thalassematid Echiurans such as Ochetostoma spp., to the extent that Botting and Muir consider that it could be placed in the same genus, although they conclude that putting an Ordovician species in a modern genus would be inappropriate, without much better evidence than is currently available.

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