THE MORPHOLOGY OF HYOLITHIDS AND ITS FUNCTIONAL IMPLICATIONS

Abstract:  The exceptionally preserved hyolithids Gompholites striatulus , Maxilites robustus , Maxilites snajdri and Maxilites sp. are described with particular emphasis on helen and muscle scar morphology. These two aspects of hyolithid morphology have remained controversial. In life position, each helen curved ventrally. When the operculum closed the aperture of the conch, each helen was locked at the commissure slit with its dorsal edge tilted forward. Inside the conch, it was held in the dorsal apertural plane and clear of the inner surface of the operculum. Previously unidentified muscle scars are described from both the operculum and the conch. Dorsal scars on the conch aperture held muscles directed to the operculum. Comparative study of the muscle insertion pattern indicates that hyolithids did not have serially arranged muscles and that all hyolithids may have had a common skeleto-muscular system. The arrangement of the muscle scars with respect to the helens suggests that the latter were capable of relatively complex movements and could have been used to propel the organism over the substrate. The general morphology and orientation of the helens suggests that in addition they functioned to stabilize the organism on the sea-floor.     

SKELETAL MICROSTRUCTURE OF HELENS, LATERAL SPINES OF HYOLITHIDS

Abstract:  In hyolithids the skeleton consists of four elements: a conch, an operculum and a pair of long, logarithmically curved 'spines' called helens. These last elements are rarely preserved, and have therefore remained poorly known and enigmatic. We have studied three-dimensionally preserved helens of the species ' Hyolithes ' lanceolatus , from the Permian of New South Wales, Australia, and ' Hyolithes ' groenwalli , from the Cambrian of Bornholm, Denmark. Helens were massive calcareous elements. Their original microstructure, herein reported for the first time, consisted of concentric lamellae surrounding a narrow elongated core, which may have been rich in organic matter. This concentric pattern resulted from the successive accretion of shell material at the proximal, internal portion of helens. This growth model is in accordance with helen morphology and with the presence of a characteristic surface sculpture of overlapping lamellae.     

The taxonomy of Galium crespianum J.J. Rodr. (Rubiaceae), a Balearic Islands endemic revisited

Galium crespianum J.J. Rodr. is a perennial plant inhabiting cliffs and crevices on the Balearic Islands. Although it was described from the mountains of Mallorca, several populations from the islands of Eivissa and Formentera have been traditionally considered as belonging to the same species. A careful comparison of specimens from the western and eastern Balearics revealed several discriminant features in gross morphology (robustness and habit of the stems, presence or absence of hairs at the internodes and leaves, waxiness of stems and leaves, shape of the inflorescence, flower colour and scent) and stem anatomy. In addition, several mutations in the ribosomal ITS sequences distinguished western and eastern plants. It is proposed that the plants from Eivissa and Formentera previously subsumed under G. crespianum be recognized at the specific level as G. friedrichii N. Torres, L. Saez, Mus & Rossello nom. nov. The new species is tetraploid (2n = 44) and shares morphological features with G. crespianum or with several taxa in the G. glaucum complex from the south east Iberian peninsula, to which it is most probably related.     

Volatile components vaxiation in the Teucrium marum complex (Lamiaceae) from the Balearic Islands

The volatile compounds of 18 samples from the western Balearic Islands belonging to three taxa of the Teucrium marum L. complex (T. marum subsp. marum, T. marum subsp. occidentale and T. marum subsp. drosocalyx) were fractionated by distillation-extraction and analysed by means of GC-MS. Seventeen components were characterized and the quantitative data were subjected to multivariate and clustering techniques. Two main groups appeared, one comprising T. marum subsp. occidentale samples and the other grouping T. marum subsp. marum and T. marum subsp. drosocalyx accessions. Chemical data and taxonomic groupings generally agreed, but quantitative and qualitative differences within and between taxa were found. Specimens from Minorca and Cabrera islands showing intermediate morphological features between T. marum subsp. marum and T. marum subsp. occidentale were included within the T. marum subsp. marum-T. marum subsp. drosocalyx group in the Principal Component Analysis. The origin of these intermediate specimens is discussed, and it is suggested that they are local variants of T. marum subsp. marum which had an independent origin throughout its area.