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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. Fil: de Carvalho, María Rosa. Universidade de Sao Paulo; Brasil Fil: Ebach, Malte C.. University of New South Wales; Australia Fil: Williams, David M.. Natural History Museum; Reino Unido Fil: Nihei, Silvio S.. Universidade de Sao Paulo; Brasil Fil: Rodrigues, Miguel Trefaut. Universidade de Sao Paulo; Brasil Fil: Grant, Taran. Universidade de Sao Paulo; Brasil Fil: Silveira, Luís F.. Universidade de Sao Paulo; Brasil Fil: Zaher, Hussam. Universidade de Sao Paulo; Brasil Fil: Gill, Anthony C.. University of Sydney; Australia Fil: Schelly, Robert C.. American Museum of Natural History; Estados Unidos Fil: Sparks, John S.. American Museum of Natural History; Estados Unidos Fil: Bockmann, Flávio. Universidade de Sao Paulo; Brasil Fil: Séret, Bernard. Muséum National d'Histoire Naturelle; Francia Fil: Ho, Hsuan-Ching. National Museum of Marine Biology and Aquarium; China Fil: Grande, Lance. Field Museum Of Natural History; Estados Unidos Fil: Rieppel, Olivier. Field Museum Of Natural History; Estados Unidos Fil: Dubois, Alain. Muséum National d'Histoire Naturelle; Francia Fil: Ohler, Annemarie. Muséum National d'Histoire Naturelle; Francia Fil: Faivovich, Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Assis, Leandro C.S.. Universidade Federal de Minas Gerais; Brasil Fil: Wheeler, Quentin D.. Arizona State University; Estados Unidos Fil: Goldstein, Paul Z.. University of Maryland; Estados Unidos Fil: De Almeida, Eduardo A.B.. Universidade de Sao Paulo; Brasil Fil: Valdecasa, A.G.. Museo Nacional de Ciencias Naturales; España Fil: Nelson, Gareth. University of Melbourne; Australia

The reconstruction of the evolutionary history of animal phyla was an integral part of Othenio Abel’s paleobiology (paleozoology). Abel took issue with those phylogeneticists who, following the lead of Haeckel, would draw up phylogenetic trees on the basis of transformation series of singular characters considered to be of particular importance. Abel highlighted Louis Dollo’s principle of the chevauchement des specialisations (crossing of specializations), which transformed phylogenetics from a search for ancestor–descendant sequences to research into relative degrees of relationships. This replacement resolved the conflict, much discussed at the time, between the continuity of ancestor–descendant lineages and the discontinuity inherent in the natural (phylogenetic) system. Walter Zimmermann refined Abel’s methodology, which he called character-phylogenetics (Merkmalsphylogenie), an approach that was eventually adopted by Willi Hennig.

Species are groups of organisms, marked out by reproductive (replicative) properties. Monophyletic taxa are groups of species, marked out by synapomorphies. In Nelson’s 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. © The Willi Hennig Society 2010.

Sinai Tschulok emigrated from the Ukraine to Switzerland, where he studied natural sciences, in particular biology. He founded and managed his own high school, which prepared students for entry to university-level education. This left him little time for research, which may explain why his work largely fell into oblivion. He did publish two influential books, however (Tschulok, S., 1910, Das System der Biologie in Forschung und Lehre, Gustav Fischer, Jena and Tschulok, S., 1922, Deszendenzlehre, Gustav Fischer, Jena), which were cited and commented upon favourably by both Walter Zimmermann and Willi Hennig. The most important point, in their opinion, was how Tschulok’s explication of biological systematics had turned the “natural system” into a proof for the “Theory of Descent”. The influence of Walter Zimmermann on Willi Hennig and the development of phylogenetic systematics is well known. Here some parts of Tschulok’s writings are discussed that render him a pioneer in Cladistics. © The Willi Hennig Society 2009.

In his “Grundzuge einer Theorie der phylogenetischen Systematik”, Hennig (1950) cited three philosophers: the leading empiricist Rudolf Carnap, the conventionalist Hugo Dingler, and the somewhat more obscure empiricist Theodor Ziehen. David Hull characterized Hennig's “Grundzuge” as one long argument against idealistic morphology. It will here be argued that Hennig attacked idealistic morphology (synonymous with “systematic” morphology) for its mode of concept formation. Building on Carnap and Ziehen, who both looked back on Ernst Cassirer, Hennig argued that the “generic”, “thing” or “class” concept of traditional nomothetic science must be replaced with Cassirer's “relation concept.” According to Hennig, such “emancipation” of systematics from the Aristotelian “species” concept would also allow transcendence from the distinction of idiographic from nomothetic sciences, thus preserving the unity of science. However, the establishment of relations in the construction of a system of order presupposes entities that can be, or are, related. Relations presuppose relata, which in modern systematics are best conceptualized (at least at the supraspecific level) not as Aristotelian classes, nor as individuals as was argued by Hennig and Ziehen, but as tokens of natural kinds. © The Willi Hennig Society 2006.

How morphology and systematics come together through morphological analysis, homology hypotheses and phylogenetic analysis is a topic of continuing debate. Some contemporary approaches reject biological evaluation of morphological characters and fall back on an atheoretical and putatively objective (but, in fact, phenetic) approach that defers to the test of congruence for homology assessment. We note persistent trends toward an uncritical empiricism (where evidence is believed to be immediately “given” in putatively theory-free observation) and instrumentalism (where hypotheses of primary homology become mere instruments with little or no empirical foundation for choosing among competing phylogenetic hypotheses). We suggest that this situation is partly a consequence of the fact that the test of congruence and the related concept of total evidence have been inappropriately tied to a Popperian philosophy in modern systematics. Total evidence is a classical principle of inductive inference and does not imply a deductive test of homology. The test of congruence by itself is based philosophically on a coherence theory of truth (coherentism in epistemology), which is unconcerned with empirical foundation. We therefore argue that coherence of character statements (congruence of characters) is a necessary, but not a sufficient, condition to support or refute hypotheses of homology or phylogenetic relationship. There should be at least some causal grounding for homology hypotheses beyond mere congruence. Such causal grounding may be achieved, for example, through empirical investigations of comparative anatomy, developmental biology, functional morphology and secondary structure. © The Willi Hennig Society 2006.

The long history of belief in a parallelism between ontogeny and a hierarchical order of natural things is reviewed. The meaning of von Baerian recapitulation is analyzed and its implications for cladistic methodology are discussed at two levels: ontogeny and homology. The basic problem inherent in the purported parallelism is that the order of natural things (i.e., the taxic approach to homology) is part of the "world of being" of Platonic ideas, whereas ontogeny and phylogeny (i.e., the transformational approach to homology) belong to Plato's "world of becoming." These two "genera of existence," as Plato put it, being and becoming, are incompatible but complementary views of nature.