The Bajocian tubeworm Spirorbis midfordensis, previously regarded as a spirorbid polychaete, is …

• Abstract
• Introduction
• Geological setting
• Material and methods
• Systematic palaeontology
• Discussion
• References
• Figures

Biology Articles » Paleobiology » Paleozoology » Microconchid tubeworms from the Jurassic of England and France » Introduction

Introduction

- Microconchid tubeworms from the Jurassic of England and France

Small, spirally−coiled calcareous worm tubes are common in the Palaeozoic and Triassic (e.g., Brönnimann and Zani− netti 1972; Burchette and Riding 1977; Weedon 1990), but rare in the Jurassic. Such tubeworms are traditionally as− signed to the polychaete genus Spirorbis. However, pre− Cretaceous examples have been reinterpreted as micro− conchids (Class Tentaculitoidea Bouček, 1964) on the basis of the early ontogeny and microstructure of their tubes (Weedon 1991, 1994; Dreesen and Jux 1995; Taylor and Vinn 2006). Microconchids (Figs. 1–4) differ from poly− chaete tubeworms (Filogranidae, Spirorbidae, and Serpu− lidae) principally in having lamellar (e.g., Fig. 4F), pseudo− punctate or punctate tubes (e.g., Figs. 2A2, D, E, 3A3, E, 4E2), and a bulb−like tube origin (Weedon 1991; Taylor and Vinn 2006; Fig. 3A2).

In the Jurassic, Spirorbis−like tubeworms have been re− corded from the Yorkshire coast (Serpula cirriformis Young, 1828; Serpula compressa Young, 1828), the Bajocian Upper Coral Bed (Spirorbis midfordensis Richardson, 1907) and the Bathonian White Limestone Formation of Gloucester− shire (Spirorbis sp. in Taylor 1979), and Caillasses de la Basse Ecarde Formation of Normandy (Spirorbula sp. in Palmer and Fürsich 1981). Another putative spirorbid, Spiro− rbis imprimus Ziegler and Michalik, 1998, described from the Upper Jurassic of the Pieniny Klippen Belt of the western Carpathians, resembles neither microconchids nor spirorbids and is most likely to be a coiled serpulid, which are very common in the Jurassic (e.g., Parsch 1956).

Spirorbiform tubeworms from the Jurassic have not pre− viously been studied in detail and their microstructures have never been described. Using well−preserved material princi− pally from the Middle Jurassic of England and France, and aided by SEM, we here document the morphologies and microstructures of supposed Spirorbis and Spirorbula, pro− viding evidence for their microconchid affinities. Conse− quently, a new genus (Punctaconchus) and two new species (P. ampliporus and P. palmeri) are introduced.