Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 16. 1993. (Budapest, 1993)

The phylogenetic relationships of the mentioned taxa are also different. "R." decorata and Sardorhynchia are typical representatives of the Tetrarhynchiinae subfamily (Ager et al. 1972, Taddei Ruggiero & Ungaro 1983). Septirhynchia has its own family or at least subfamily and is a rootless enigma (Mancenido & Walley 1979), showing closer relationship to the Dimerellidae than to the "true" rhynchonellid families (Ager et al. 1972). The phylogenetic position of Lessiniella is even less clear but the basic external and internal similarities seem to link it to the family Septirhynchiidae. Ager et al. (1972) speculated on the ancestry of this family and suggested the Stenoscismatacea as a possible Late Paleozoic parent group. The internal features of the two taxa are, however, very different, therefore a true phylogenetic relationship seems to be highly improbable. Similar is the case with Lessiniella: the Paleozoic forms with almost identical exterior, mentioned in this paper, are totally different internally and belong to another order (Pentamerida). Therefore, Septirhynchia and Lessiniella are probably not "Lazarus taxa" but can be regarded as cases of heterochronous homoeomorphy. In conclusion, the assemblage of the giant, late Middle Jurassic rhynchonellids is not homogeneous. "R." decorata and Sardorhynchia are distinct from the septirhynchiids both in distribution and in phylogeny and their seemingly coeval appearance might be merely incidental. The other two giants (Septirhynchia and Lessiniella) are apparently closer in morphology and in phylogeny, possibly belonging to the same stem and may represent two offshoots adapted to very different environments. The strong Paleozoic reminiscences they show, recall the array of archaic features found in the Jurassic brachiopods of the Mediterranean province (Ager et al. 1972, Vörös 1977, 1984). This Paleozoic "flavour" seems to be connected to the Tethys, the "lost Eden" of brachiopods. As it was suggested elsewhere (Vörös 1993) the western end of the oceanic Tethys was an asylum and an evolutionary centre for the brachiopods in the first half of the Mesozoic. It was favourable for the maintenance or recurrence of archaic morphological features. In the late Middle Jurassic, by the opening of the "Hesperian Strait" between the Tethys and the Central Atlantic, the system of the oceanic circulation in the Tethys fundamentally changed. This was probably the last moment for the true Tethyan brachiopods to invade newly opened areas and niches; Septirhynchia and, with less success, Lessiniella took the advantage of this opportunity. ACKNOWLEDGEMENTS Thanks are due to Mr. Attilio BENETTI (Camposilvano, Italy) for loaning the original specimens of Lessiniella for study. Dr. Miguel MANCENIDO (La Plata, Argentina) kindly revised and commented a first version of this paper; his valuable help is acknowledged herein. REFERENCES AGER. D. V (1965): Mesozoic and Cenozoic Rhynchonellacea. In: Moore, R. C. (Ed.): Treatise on Invertebrate Paleontology, Part H: Brachiopoda, University of Kansas Press: H597-H625. AGER, D. V, CHILDS, A. & PEARSON, D. A. B. (1972): The evolution of the Mesozoic Rhynchonellida. - Géobios, 5 (2-3): 157-233.