The western Anglo−Paris Basin was a major site of shallow marine carbonate sedimentation duringMiddle Jurassic times. The sequence stratigraphy of the region has been studied by Rioult et al. (1991) who recognized 18 depositional cycles in the Middle to Upper Jurassic related to short−term changes in sea−level. Fossil invertebrates are very abundant and diverse in the Middle Jurassic of England and Normandy. They have been the subject of numerous monographic studies beginning in the early 19th century, along with several palaeoecological studies in more recent years.
The tubeworms used in the current study come from five stratigraphical horizons spanning Upper Aalenian to Upper Bathonian, the names of the tubeworm species recorded be− ing given in brackets. In ascending order the horizons are:
(1) Upper Aalenian, Ludwigia murchisonae Zone; Infe− rior Oolite Group, Birdlip Limestone Formation, Crickley Member (including the former “Pea Grit”); Stroud−Chel− tenham area of Gloucestershire, England (see Barron et al. 1997). Thismaterial encrusts articulated shells of large tere− bratulid brachiopods, at least some of which are from an oncolitic limestone believed to have been deposited in a shallow water, open shelf environment where the sea−bed was stabilised by dense vegetational cover (Mudge 1995). (Punctaconchus ampliporus sp. nov.).
(2) Lower Bajocian, Witchellia laeviuscula Zone; Lin− colnshire Limestone Formation, Kirton Shale Member (see Ashton 1980); Kirton−in−Lindsey, Lincolnshire, England. All specimens are detached from their original substrates. (Punctaconchus midfordensis [Richardson, 1907]).
(3) Upper Bajocian, Parkinsonia parkinsoni Zone; Infe− rior Oolite Group, Salperton Limestone Formation, Clypeus Grit Member (see Parsons 1976; Barron et al. 1997); around Midford, Avon and Stroud, Gloucestershire, England. These detached specimens belong to the Lindsall Richardson Col− lection, are labelled “Bradfordian (Truellii), Upper Coral− bed”, and possibly include syntypes of Spirorbis midforden− sis Richardson, 1907. (Punctaconchus midfordensis [Richard− son, 1907]).
(4) Middle or Upper Bathonian, Morrisiceras morrisi or Procerites hodsoni zones; Great Oolite Group, White Lime− stone Formation; Foss Cross Quarry, Gloucestershire. Re− corded as Spirorbis sp. by Taylor (1979), most of this mate− rial encrusts shells of the bivalve Plagiostoma. (Punctacon− chus ampliporus sp. nov.). (5) Upper Bathonian, Aulacosphinctes hollandi Zone; Caillasses de la Basse Ecarde Formation (see Rioult et al. 1991); St Aubin−sur−Mer, Calvados, Normandy, France. Most of the spirorbiform tubeworms here encrust a lithistid sponge, Platychonia magna, which forms small patch reefs (Palmer and Fürsich 1981). (Punctaconchus palmeri sp. nov.).
In addition to these Middle Jurassic localities, a tube− worm−encrusted intraclast allegedly from the Lower Jurassic was studied. The specimen is labelled as Whitbian (= Toar− cian) in age and is apparently a derived fossil obtained by dredging the River Nene at Stebbington, Huntingdonshire, England. The tubeworms—Punctaconchus ampliporus sp. nov.—are partly decalcified, revealing casts of the pores or punctae that penetrate their walls.
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