126 



J.D. TAYLOR, Y.I. KANTOR AND A.V. SYSOEV 



The Conoidea are considered to be monophyletic, because 

 the families share the common apomorphy of a venom 

 apparatus con-sisting of the venom gland and muscular bulb. 

 This is thought to have been lost in some taxa, such as some 

 highly-derived members of the Daphnellinae and Terebridae 

 (Kantor & Sysoev 1989; Taylor, 1990) and all Strictispirinae. 



Compared with the number of living species and the 

 attention paid to the description of shells, particularly of 

 Conidae, there have been very few anatomical studies of 

 Conoidea. However, recently, a much wider range of species 

 from the Turridae, Terebridae and Pervicaciidae (Sysoev & 

 Kantor 1987, 1988, 1989; Kantor & Sysoev, 1989; Miller, 

 1989, 1990; Kantor, 1990; Taylor, 1990) have been investi- 

 gated anatomically. These studies illustrate the great variety 

 of foregut anatomy, particularly within the Turridae and 

 Terebridae. By comparison, the Conidae appear to have a 

 relatively uniform foregut anatomy (Marsh, 1971; Miller, 

 1989), although they have been surprisingly little studied. 



Until recently, attempts to use anatomical characters in 

 determining relationships amongst conoideans were con- 

 strained either by the limited range of taxa that had been 

 studied or by the small number of characters used. For 

 example, an evolutionary scenario for the Conoidea based 

 upon characters of foregut anatomy was proposed by Sheri- 

 dan etal. (1973), but species were studied from only three out 

 of the seventeen turrid subfamilies. Additionally, Shimek & 

 Kohn (1981) used only radular characters to produce a 

 cladistic analysis of a wider range turrid taxa. 



Another problem in comparing the different taxa studied 

 within the Conoidea, is that the nomenclature for the differ- 

 ent anatomical structures is inconsistent and very confused. 

 This has hampered the recognition of homologous structures 

 that may be shared between the different taxa. 



In this paper we attempt a comparative review of the 

 anatomy and functional morphology of the conoidean 

 foregut. We have attempted to examine species from all the 

 currently-recognised subfamilies of Turridae, many species of 

 Terebridae, Pervicaciidae and a few species of Conns. Addi- 

 tionally, we have incorporated previously published studies 

 into our review and attempted to standardize the nomencla- 

 ture of the anatomical structures. 



The overall objectives of the study are, firstly, to evalu-ate 

 the use of characters of foregut anatomy in determining 

 relationships among the Conoidea and secondly, to propose a 

 new classification of conoidean higher taxa which incorpo- 

 rates these anatomical characters. Foregut anatomy was 

 chosen as the focus for this study, because a few previous 

 studies (Sheridan et al. 1973; Kantor, 1990) had drawn 

 attention to the diversity and complexity of the digestive 

 system. As far as is known, other organ systems are similar to 

 other neogastropods. 



descriptions in our analysis. Additionally, radular prepara- 

 tions were made from a range of other species. 



Critical-point dried preparations for scanning electron 

 microscopy were made of some anatomical structures and 

 some small species (methods in Taylor & Miller, 1989). 

 Radula preparations for both light and scanning microscopy 

 were made by standard methods. 



FOREGUT ANATOMY 



A generalized diagram of the conoidean foregut (Fig. 1) 

 shows the relative positions of the major structures. 



rstm 



rcoel 



rw 





MATERIAL AND METHODS 



The material on which this study is based consists mainly of 

 longitudinal serial sections of the foreguts of a wide range of 

 gastropods from all of the currently recognised subfamilies of 

 Turridae, many Terebridae and Pervicaciidae and a few 

 species of Conidae (Table 1). Dissections were also made of 

 most of these species. Also indicated in Table 1 are species 

 for which we have used previously published anatomical 



Fig. 1 Composite diagram of the foregut of a hypothetical 



conoidean gastropod showing the location of the major structures 

 discussed in the text. No single gastropod possesses all these 

 features. Abbreviations: as, anterior sphincter of buccal tube; bl, 

 buccal lips; bm, buccal mass; bt, buccal tube; is, intermediate 

 sphnicter of buccal tube; m, mouth; mb; muscular bulb; oe, 

 oesophagus; p, proboscis; rcoel, rhynchocoel; rs, radular sac; rsp, 

 rhynchostomal sphincter; rstm, rhynchostome; rw, rhynchodeal 

 wall; s, septum; sg, salivary gland; tm, transverse muscles of 

 rhynchodeal wall (shown in part only); vg, venom gland. 



