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Evolutionary Systematics, also called Gradistic Taxonomy, gives an a dynamic evolutionary slant to the static . It is based on a combination of branching and divergence. Most old books on were based on this paradigm. Evolutionary Systematics was formulated by such "grand old men" of paleontology as and . This approach accepts the as adequate for reconstructing phylogenetic trees, but retains groups (e.g. "").
Also, unlike Cladistics, with it's reliance on a proposed that is never actually described or discovered (a missing link that is always missing), Evolutionary systematics gives illustrations of the actual evolution of one species or higher taxon into another.
Admittedly, Evolutionary Systematics suffers from a number of shortcomings. For example the use of several very different criteria (, divergence, adaptational level) to define particular taxa, as well as inconsistencies inherent in the paraphyletic approach (e.g. separating (Birds) from the ). This, together with the greater rigor and precision of the Cladistic (Phylogenetic) approach has meant that over the past decades, Evolutionary Systematics has greatly declined with cladistics becoming the dominant paradigm.
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Evolutionary Systematics: The so-called "Evolutionary Systematics" is a syncretistic approach to biological systematics, which was especially endorsed by ERNST MAYR and SIMPSON. Although the proponents of this approach mostly accepted the Hennigian methodology as adequate technique for the reconstruction of , they strongly objected against a strictly cladistic classification, since they wanted to use paraphyletic groups in their classifications. These paraphyla (e.g. "Reptilia") were a direct corollary of their desire to assign a higher categorical rank (e.g. class) to a monophyletic taxon with numerous (e.g. birds), than to its sister group (e.g. ), if the latter has retained numerous with other groups (e.g. ). This desire was justified by the greater "evolutionary divergence" compared to the common ancestor, and the possession of a new "adaptational level". Except the difficulty to define and measure "evolutionary divergence" and "adaptational level", the main problem of this approach is the extreme arbitrariness in the classification and delimitation of paraphyla: Should been divided in "" (paraphyletic) versus (monophyletic), or rather in "" (paraphyletic) versus (monophyletic), or better in "" (paraphyletic) versus (monophyletic); should one likewise divide Vertebrata in "" (paraphyletic) versus (monophyletic), or in "" (paraphyletic) versus (monophyletic), or maybe even in non-mammals (paraphyletic) and Mammalia (monophyletic), which curiously was never proposed yet. Even the exclusion of from the of animals as separate kingdom (regnum) "" has been proposed and would be absolutely compatible with the principles of "Evolutionary Systematics". The grouping of crocodiles and birds as sistergroups in a monophyletic taxon Archosauria has been dismissed as absurd by evolutionary systematists, while they accepted a group like Deuterostomia without any protest, although it is including such divergent organisms as and man. A further critique against Phylogenetic Systematics was the mere conjecture that it shall completely neglect the evidence from symplesiomorphic characters, although they are important , too. This statement is of course nonsense, since all homologous characters are recognized and used in Phylogenetic Systematics, and symplesiomorphic characters are therefore not neglected at all, but are recognized on that hierarchical level on which they do represent a ... A more general problem of "Evolutionary Systematics" is the circumstance that several very different criteria are used for the construction of a classification (phylogeny, divergence, adaptational level), but in the resulting system it is not recognizable which criteria have been used for a particular taxon. Because of the mentioned problems and the theoretical, practical and heuristic superiority of Phylogenetic Systematics, the number of proponents of "Evolutionary Systematics" has strongly declined in the past decades."