A three-dimensionally preserved fossil polychaete worm from the Silurian of Herefordshire, England

Abstract

Polychaete body fossils are rare, and are almost invariably compressed and too poorly preserved for meaningful comparison with extant forms. We here describe Kenostrychus clementsi gen. et sp. nov. from the Silurian Herefordshire Konservat-LagerstÌtte of England, in which three-dimensional external morphology is preserved with a ¢delity unprecedented among fossil polychaetes. The fossils, which are preserved in calcite, were serially ground and photographed at 30 mm intervals to produce computergenerated reconstructions of the original external surface. The new genus has a generalized polychaete morphology with large biramous parapodia, unspecialized anterior segments and a small prostomium with median and lateral antennae and ventral prostomial palps. Cirriform branchiae arise from the ventral surface of each notopodium, and may be homologous with the inter-ramal branchiae of the extant nephtyids. Through cladistic analysis, Kenostrychus is interpreted as a member of a stem group of either the Phyllodocida or the Aciculata (Phyllodocida + Eunicida). Direct comparison with other fossil forms is di¤cult, but hints that inter-ramal respiratory structures may be primitive within the Phyllodocida and/ or the Aciculata.

Computer reconstruction and analysis of the vermiform mollusc Acaenoplax hayae from the Herefordshire Lagerstätte (Silurian, England), and implications for molluscan phylogeny

“…1 and description). Note also that previously (Sutton et al 2001a) we mistakenly identified an extra ridge beneath valve V4; hence ridges R7-R17 herein are equivalent to ridges R8-R18 of Sutton et al (2001a, fig. 3).…”

“…11), OUM C.29530 (Sutton et al 2001a, fig. 1b, f-g), OUM C.29531 (Sutton et al 2001a, fig. 1d), OUM C.29532 (Sutton et al 2001a, figs 1h-i, 2c;Sutton et al 2001d, fig.…”

“…1) follows and builds upon that of Sutton et al (2001a). All structures are numbered anterior to posterior, and the ridges (R) and associated lobe-rows (L) are designated by the same number.…”

“…Hence L4·1 is the anteriormost lobe in row L4, and L-2·7 is the seventh lobe from the anterior in lobe-row L-2. Projections from the posterior cavity (not individually labelled by Sutton et al 2001a) are referred to as Ps, Pm, and P1-P4 (see Text- fig. 1 and description).…”

A starfish with three-dimensionally preserved soft parts from the Silurian of England

“…Fossils from this deposit are preserved as three-dimensional calcite in-fills in nodules in a volcaniclastic ash (Orr et al 2000), and preserve high-fidelity details of soft tissues that can be studied through serial grinding and computer reconstruction (Sutton et al 2001b). The deposit has yielded a diversity of sponges; radiolarians ; an aplacophoran-like mollusc, Acaenoplax hayae (Sutton et al 2001a; several arthropods including Offacolus kingi (a stem group chelicerate; Orr et al 2000;Sutton et al 2002), Colymbosathon ecplecticos (a myodocopid ostracod crustacean; Siveter et al 2003), Cinerocaris magnifica (a phyllocarid crustacean; Briggs et al 2004), and Haliestes dasos (a pycnogonid; Siveter et al 2004); a polychaete worm, Kenostrychus clementsi (Sutton et al 2001c); and an array of as yet undescribed species, including several more echinoderms.…”