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Journal of Paleontology

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TUBE ULTRASTRUCTURE OF THE FOSSIL GENUS ROTULARIA DEFRANCE, 1827 (POLYCHAETA, SERPULIDAE)

¹ Institute of Geology, University of Tartu, Vanemuise 46, 51014 Tartu, Estonia <olev.vinn@ut.ee>

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
AMONG POLYCHAETE annelids, calcareous tubes occur in Serpulidae, Spirorbidae, Sabellidae, and Cirratulidae (Perkins, 1991; Fischer et al., 2000). The tubes of most serpulids are completely or partially cemented to the substrate. The fossil genus Rotularia has a peculiar unattached, spirally coiled tube, thus well distinguishable from the other known serpulids. Tube records of Rotularia are known from Mesozoic (Late Jurassic) (Ball, 1960; Stevens, 1967) to Early Tertiary sediments, becoming very common during the Cretaceous and Eocene (see Savazzi, 1995). It also has a global distribution (Wrigley, 1951; Ball, 1960; Keen, 1961; Regenhardt, 1961; Howell, 1962; Stevens, 1967; Chiplonkar and Tapaswi, 1973; Ware, 1975; Lommerzheim, 1979; Macellari, 1984; Jäger, 1993).

Owing to the peculiar shape of Rotularia, many authors in the past interpreted it as a vermetid gastropod (e.g., Bronn, 1827; Schauroth, 1865; Stoliczka, 1868; Whitfield, 1890; Rovereto, 1904; Cossmann, 1912; Doncieux, 1926; Rutsch, 1939; Wenz, 1943). Serpulid identification has been definitively confirmed by recent observations on the tube structures (Accorsi Benini and Ungaro, 1989; Savazzi, 1995). All rotularias were cemented to the substrate during their earliest growth stage, but they became detached shortly after the formation of first whorls (Savazzi, 1995). Their tubes have two layers (Schmidt, 1955; Ball, 1960; Savazzi, 1995), the thin inner layer composed of lamellae subparallel to the inner shell surface and the thick outer layer with chevron shaped growth lamellae.

The tube ultrastructure of Recent serpulid polychaetes has been recently studied by various authors (Bubel et al., 1983; ten Hove and Zibrowius, 1986; Zibrowius and ten Hove, 1987; ten Hove and Smith, 1990. . . [Full Text of this Article]