Crown Group - Palaeontological Significance of Stem- and Crown Groups

Palaeontological Significance of Stem- and Crown Groups

Placing fossils in their right order in a stem group allows the order of these acquisitions to be established, and thus the ecological and functional setting of the evolution of the major features of the group in question. Stem groups thus offer a route to integrate unique palaeontological data into questions of the evolution of living organisms. Furthermore, they show that fossils that were considered to lie in their own separate group because they did not show all the diagnostic features of a living clade, can nevertheless be related to it by lying in its stem group. Such fossils have been of particular importance in considering the origins of the tetrapods, mammals, and animals.

The application of the stem group concept also radically reformed the interpretation of the organisms of the Burgess shale. Their classification in stem groups to extant phyla, rather than in phyla of their own, made the Cambrian explosion much easier to understand without invoking unusual evolutionary mechanisms.

Read more about this topic:  Crown Group

Famous quotes containing the words significance, crown and/or groups:

    I am not afraid that I shall exaggerate the value and significance of life, but that I shall not be up to the occasion which it is.
    Henry David Thoreau (1817–1862)

    The crown of literature is poetry. It is its end and aim. It is the sublimest activity of the human mind. It is the achievement of beauty and delicacy. The writer of prose can only step aside when the poet passes.
    W. Somerset Maugham (1874–1966)

    ... until both employers’ and workers’ groups assume responsibility for chastising their own recalcitrant children, they can vainly bay the moon about “ignorant” and “unfair” public criticism. Moreover, their failure to impose voluntarily upon their own groups codes of decency and honor will result in more and more necessity for government control.
    Mary Barnett Gilson (1877–?)