The decline in morphological phylogenies has become a pronounced trend in contemporary systematics due to a disregard for theoretical, methodological, conceptual, and philosophical approaches. The role and meaning of morphology in phylogenetic reconstruction and classification have been undermined by the following: (i) the ambiguous delineation of morphological characters; (ii) the putative ''objectivity'' of molecular data; (iii) that morphology has not been included in data matrices; (iv) that morphology has been mapped onto molecular cladograms; and (v) a separation of a paradigmatic relationship among morphology, phylogeny, and classification. Historical ⁄ philosophical arguments including the synthesis of coherence (coherentism) and correspondence (foundationalism) theories-i.e. ''foundherentism'' as a theory of epistemic justification-provide support for a renaissance of morphology in phylogenetic systematics. In the language of systematics, coherence theory corresponds to the logical ⁄ operational congruence of character states translated into a hierarchical ⁄ relational system of homologues and monophyletic groups as natural kinds. Correspondence theory corresponds to the empirical ⁄ causal accommodation of homologues and monophyletic groups as natural kinds grounded in the concept of semaphoront, and in developmental biology, genetics, inheritance, ontogenesis, topology, and connectivity. The role and meaning of morphology are also discussed in the context of separate and combined analyses, palaeontology, natural kinds, character concepts, semaphoront, modularity, and taxonomy. Molecular systematics suffers from tension between coherence and correspondence theories, and fails to provide a pragmatic language for predicates in science and in everyday life. Finally, the renaissance of morphology is not only dependent on a scientific ⁄ philosophical perspective but also depends on political, economic, social, and educational reforms in contemporary systematics.Ó The Willi Hennig Society 2009.It has recently been assumed that molecular phylogenies have primacy over morphological phylogenies in comparative biology and systematics. In this scenario, the role and meaning of morphological and molecular evidence in phylogenetic reconstruction have experienced a renewed and rigorous evaluation (e.g. argued that most morphological characters are too ambiguous in interpretation to be included in data matrices; the delineation of homology is subjective; and they do not provide phylogenetic accuracy or resolve phylogenetic relationships at any taxonomic level. Scotland et al. (2003) also claimed that, at the very least, DNA sequence data offer the unique potential of large numbers of unambiguous characters and therefore they opt for either the inclusion of only a few morphological characters in data matrices (those that can be anatomically delineated) or promoted the use of mapping of morphological characters onto molecular cladograms in order to interpret morphological evolution.

Taxa and homologues can in our view be construed both as kinds and as individuals. However, the conceptualization of taxa as natural kinds in the sense of homeostatic property cluster kinds has been criticized by some systematists, as it seems that even such kinds cannot evolve due to their being homeostatic. We reply by arguing that the treatment of transformational and taxic homologies, respectively, as dynamic and static aspects of the same homeostatic property cluster kind represents a good perspective for supporting the conceptualization of taxa as kinds. The focus on a phenomenon of homology based on causal processes (e.g., connectivity, activity-function, genetics, inheritance, and modularity) and implying relationship with modification yields a notion of natural kinds conforming to the phylogenetic-evolutionary framework. Nevertheless, homeostatic property cluster kinds in taxonomic and evolutionary practice must be rooted in the primacy of epistemological classification (homology as observational properties) over metaphysical generalization (series of transformation and common ancestry as unobservational processes). The perspective of individuating characters exclusively by historical-transformational independence instead of their developmental, structural, and functional independence fails to yield a sufficient practical interplay between theory and observation. Purely ontological and ostensional perspectives in evolution and phylogeny (e.g., an ideographic character concept and PhyloCode's 'individualism' of clades) may be pragmatically contested in the case of urgent issues in biodiversity research, conservation, and systematics.

Species are groups of organisms, marked out by reproductive (replicative) properties. Monophyletic taxa are groups of species, marked out by synapomorphies. In NelsonÕs analysis, monophyly and synapomorphy are identical relations. Monophyly and synapomorphy, however, are not equivalent relations. Monophyly is epistemically not accessible, whereas synapomorphy is epistemically accessible through character analysis. Monophyly originates with speciation, the two sister-species that come into being through the splitting of the ancestral species lineage forming a monophyletic taxon at the lowest level of inclusiveness. Synapomorphy provides the empirical evidence for monophyly, inferred from character analysis in the context of a three-taxon statement. If synapomorphy and monophyly were equivalent, phylogenetic systematists should find a single tree, instead of multiple equally parsimonious trees. Understanding synapomorphy as the relevant evidence for phylogenetic inference reveals a category mistake in contemporary phylogenetics: the treatment of morphological characters mapped onto molecular trees as synapomorphies and homoplasies. The mapping of morphological characters onto nodes of a molecular tree results in an empirically empty procedure for synapomorphy discovery. Morphological synapomorphies and homoplasies can only be discovered by morphological and combined analyses. The use of morphology in phylogenetic inference in general is defended by examples from Laurales and Squamata in particular. To make empirical evidence scientifically relevant in order to search for concordance, or dis-concordance, of phylogenetic signal, is certainly more fruitful for phylogenetics than the uncritical mapping of morphological traits on a molecular scaffold.

Recent commentary by Costello and collaborators on the current state of the global taxonomic enterprise attempts to demonstrate that taxonomy is not in decline as feared by taxonomists, but rather is increasing by virtue of the rate at which new species are formally named. Having supported their views with data that clearly indicate as much, Costello et al. make recommendations to increase the rate of new species descriptions even more. However, their views appear to rely on the perception of species as static and numerically if not historically equivalent entities whose value lie in their roles as "metrics". As such, their one-dimensional portrayal of the discipline, as concerned solely with the creation of new species names, fails to take into account both the conceptual and epistemological foundations of systematics. We refute the end-user view that taxonomy is on the rise simply because more new species are being described compared with earlier decades, and that, by implication, taxonomic practice is a formality whose pace can be streamlined without considerable resources, intellectual or otherwise. Rather, we defend the opposite viewpoint that professional taxonomy is in decline relative to the immediacy of the extinction crisis, and that this decline threatens not just the empirical science of phylogenetic systematics, but also the foundations of comparative biology on which other fields rely. The allocation of space in top-ranked journals to propagate views such as those of Costello et al. lends superficial credence to the unsupportive mindset of many of those in charge of the institutional fate of taxonomy. We emphasize that taxonomy and the description of new species are dependent upon, and only make sense in light of, empirically based classifications that reflect evolutionary history; homology assessments are at the centre of these endeavours, such that the biological sciences cannot afford to have professional taxonomists sacrifice the comparative and historical depth of their hypotheses in order to accelerate new species descriptions.

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