Fróðskaparrit - 01.01.2001, Side 109

Fróðskaparrit - 01.01.2001, Side 109
ARMFÓTINGAR (BRACHIOPODA) í FØROYSKUM ØKI 1 13 An important part of the paper by We- senberg-Lund (1941) for the present study is the description of the two superficially similar looking Terebratulina species. For this purpose, Wesenberg-Lund used several features pertaining to the morphology of the shell. She concluded that the two species either represented a morphological- ly based cline with intermediate forms, or were two different races (subspecies) cau- sed by different ecological conditions. This problem has since been investigated using principal component analysis on a morpho- logical study of the shells (Curry and Endo 1991) and DNA and immunological analy- sis of the intracrystalline shell proteins (Co- hen et al:, 1991). Both studies confirmed the presence of two valid species with no intermediate forms. In 1990, the present author published a paper concemed with the application of brachiopods in palaeoceanographic recon- structions (Thomsen, 1989). This paper dealt mainly with Macandrevia cranium (Miiller, 1776) and established the recent biogeography of this species based on pub- lished information and unpublished re- cords. The biogeography shows that M. cranium is almost completely confined to the shelves surrounding the North Atlantic and the Norwegian-Greenland Sea. When this distribution pattem is compared with published information on autecology and possible limiting environmental factors, the conclusion reached is that there is substan- tial evidence for the pattern being a func- tion of dispersal by the Gulf Stream (cf. Helmcke, 1939b) and its continuations, i.e. the North Atlantic Current, the Norwegian Current and the North Cape Current. Thus the stratigraphical occurrence of M. crani- um in Late Weichselian-Holocene sedi- ments on the Norwegian shelf maý be used as an important marker for the presence of Atlantic Water and the final intrusion of At- lantic Water masses. In connection with this study, the distribution of M. cranium on the Faroe platform was mapped (Thomsen, 1989) based on Wesenberg-Lund (1940, 1941) and O.S. Tendal (pers. comm., Nør- revang etal., 1994). It confirmed the affini- ty of the species to the Atlantic Water (also demonstrated in the present paper). Curry and Endo (1991) later also found a palae- oceanographic connection when studying the distribution of the two terebratulinids in the North Atlantic. They concluded that T. retusa has its main distribution in the east- em North Atlantic and T. septentrionalis in the western North Atlantic, with the excep- tion of a supposed relict occurrence of T. retusa off Finnmark, northern Norway. However, Thomsen and Brattegard (1997) recorded T. septentrionalis from Hordaland northwards into the Barents Sea. Recently, Pakhnevich (1997) has studied the size and age characteristics of Macan- drevia cranium based on two trawl sam- ples, one of which was recovered by the R/V ”Sevastopol” south-west off the Faroes in 1959. The BIOFAR programme The BIOFAR programme (Investigations on the marine benthic fauna of the Faroe Is- lands) is a Nordic research programme (Nørrevang et al., 1994). The aim of the programme is to study the marine benthic
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49. nummar (01.01.2001)

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