| | The families of gymnosperms |
Including Lebachia, Ernestiodendron, Walchia, Walchiostrobus, Pseudovoltzia, Palaeotaxus, Araucarioxylon
Taxonomy. Pinales, Araucariales, and Cupressales.
Comments. Gymnosperms as a group merit study by all serious biology students, not only because of the ecological and economic significance of extant forms, but by virtue of their well documented evolutionary history. Distinctness since the early Mesozoic of the conifer and taxad lineages is unambiguously demonstrated by the fossil record; and the details of the evolutionary origins of coniferous female cones are at least as compelling, and as intellectually satisfying, as the far more widely publicized example of the evolution of the horse's foot. In particular, Rudolph Florin’s elegant revelation of the nature of the "ovuliferous scale", which involved extensive comparative morphological and anatomical studies of both fossils and extant forms, set admirable standards for palaeontologists and taxonomists alike.
The sample illustrations given here exemplify a sequence of fossil conifers, progressing from the Carboniferous epoch to the Cretaceous, with details of a present-day taxodiaceous cone for comparison. They should suffice to explain (for example) the peculiar vascularization of modern cones, with their "inverted" vascular bundles. Further examples are provided with the family descriptions, but students interested in pursuing the topic properly should consult Florin’s classic (1951) summary paper, then proceed to the modern literature.
Miscellaneous. • Female cones: Lower Permian. • Female cones: Upper Permian, Triasic, Jurassic. • Female cones: Jurassic and Cretaceous, cf. extant Cunninghamia. • Upper Triassic Palaeotaxus, cf. extant Taxus canadensis. • Agathis jurassica, from a Jurassic deposit in N.S.W., Australia: cf. extant Agathis spp..
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2008 onwards. The families of gymnosperms. Version: 5th August 2019. delta-intkey.com’.
