Taxonomic investigation of elements from the early cretaceous megaflora from the Middle Clarence Valley, New Zealand
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The fossil megaflora of the middle Clarence valley, South Island, New Zealand, contains leaf forms attributable to all the following plant groups: liverworts, ferns, equisetaleans, cycads, bennettites, pentoxylaleans, ginkgoaleans, araucariaceans, podocarps, pteridosperms and dicotyledons. The elements investigated here are taxa belonging to Phyllopteroides, Taeniopteris, Cycadales, Bennettitales, Ginkgo, Agathis and dicotyledonous foliage form species. The sediments in which this megaflora occurs are fluviatile and lacustrine and were laid down in a coastal region of South Gondwana. The age of the deposits is late Albian/early Cenomanian. The palaeolatitude was high, being within the Antarctic Circle. Palaeoclimatic evidence shows that the climate of polar regions in Cretaceous times was mild temperate and highly equable at least in coastal regions. Methods of extraction and photography of fossil cuticle are described. Numerical taxonomic methods are used to analyse 1) the relationships of fossil taxa within particular plant groups, 2) between New Zealand and Australian fossils, and, 3) between a fossil species and extant species of Agathis. The new term numerotype is here proposed to rationalise variation of characters within a taxon for computational purposes. Thirty-four new leaf form species are described systematically, of which 22 are dicotyledonous. These dicotyledonous leaves are all simple, broadly laminate, pinnately reticulate-veined and petiolate, and possibly some were deciduous.