A phylogeny of the species of the loricariid genus Acestridium and relevant outgroups is presented based on a parsimony analysis of 52 unweighted and unordered morphological characters. Acestridium is diagnosed as monophyletic based on the possession of the 17 exclusive synapomorphies. Two primary trees were found, and the strict consensus among those alternative trees resulted in the following relationships: ((A. dichromum + A. triplax)(A. gymnogaster + A. scutatum + (A. discus (A. colombiensis + A. martini)))). Acestridium was found to be sister to Niobichthys with this clade subsequently the sister-group to Oxyropsis + Hypoptopoma.Uma filogenia das espécies do gênero de Loricariidae Acestridium e grupos externos relevantes é apresentada com base na análise de parcimônia de 52 caracteres morfológicos não pesados e desordenados. Acestridium é diagnosticado como monofilético com base na posse de 17 sinapomorfias exclusivas. Duas árvores primárias foram encontradas e o consenso estrito entre essas árvores alternativas resultou nas seguintes relações: ((A. dichromum + A. triplax)(A. gymnogaster + A. scutatum + (A. discus (A. colombiensis + A. martini)))). Acestridium foi encontrado como grupo-irmão de Niobichthys e este clado como grupo-irmão sucessivo de Oxyropsis + Hypoptopoma.

The discovery of three new taxa of Hypoptotopomatini with ambiguous generic assignment prompted a reanalysis of the phylogenetic relationships of the tribe. The analysis focused on a data matrix of 56 terminals and 107 morphological characters comprising the three new taxa, most species of Hypoptopoma and Otocinclus, and all other species of the tribe. The 162 maximally parsimonious trees of 382 steps, consistency index of 0.41, and retention index of 0.83 were then summarized in a strict consensus tree. The results confirm the monophyly of the Hypoptopomatini, recover four genera as monophyletic (Acestridium, Hypoptopoma, Niobichthys, and Otocinclus), revealed Hypoptopoma and Oxyropsis to be non-monophyletic; and revealed two new genera within Hypoptopomatini. Additionally, Otocinclus was found to be sister to a group with all remaining genera of the tribe; Acestridium and Niobichthys were found to be sister to each other and that clade sister to a group formed by ((Leptotocinclus + Hypoptopoma [part]) + (Nannoxyropsis (Oxyropsis + Hypoptopoma [part]))). Based on this framework, changes to the classification and the taxonomy of the Hypoptopomatini are suggested and the new taxa are described.Keywords: Hypoptopomatinae, Morphology, New genera, Systematics, Taxonomy.A descoberta de três novos táxons pertencentes à Hypoptopomatini com designações genéricas incertas, levaram a uma nova análise das relações filogenéticas da tribo. A análise focou em uma matriz de dados formada por 56 terminais e 107 caracteres morfológicos incluindo os três novos táxons, a maioria das espécies de Hypoptopoma e Otocinclus, e todas as demais espécies da tribo. As 162 árvores maximamente parcimoniosas com 382 passos, índice de consistência 0.41 e índice de retenção 0.83 foram sumarizadas em um consenso estrito. O resultado obtido corrobora o monofiletismo de Hypoptopomatini, recupera quatro gêneros como grupos monofiléticos (Acestridium, Hypoptopoma, Niobichthys, e Otocinclus), aponta Hypoptopoma e Oxyropsis como grupos não-monofiléticos e revela dois novos gêneros pertencentes à Hypoptopomatini. Adicionalmente, Otocinclus foi encontrado como sendo grupo-irmão de um clado formado por todos os demais gêneros da tribo e Acestridium e Niobichthys formam um grupo-irmão mais relacionado a um clado formado por dois grupos monofiléticos ((Leptotocinclus + Hypoptopoma [parte]) + (Nannoxyropsis (Oxyropsis + Hypoptopoma [parte]))). Com base neste cenário, sugere-se mudanças na classificação e na taxonomia de Hypoptopomatini e os novos táxons são descritos.

Epactionotus species are known for inhabiting the rocky-bottom stretches of fastflowing rivers in a limited geographic area along the Atlantic coast of southern Brazil. These species are endemic to single coastal river drainages (two neighbouring drainages for Epactionotus bilineatus) isolated from each other by the coastal lacustrine environments or the Atlantic Ocean. E. bilineatus is from the Maquiné and Três Forquilhas River basins, both tributaries of the Tramandaí River system, whereas E. itaimbezinho is endemic to the Mampituba River drainage and Epactionotus gracilis to the Araranguá River drainage. Recent fieldwork in the Atlantic coastal drainages of southern Brazil revealed new populations in the Urussanga, Tubarão, d'Una and Biguaçu River drainages. Iterative species delimitation using molecular data (cytochrome c oxidase subunit I) and morphology (morphometrics and meristics) was applied to evaluate species recognition of isolated populations. With regard to new data, the genus was re-diagnosed, the status of Epactionotus species/populations was re-evaluated, formerly described species were supported and population structure was recognized. As for the newly discovered populations, both morphological and molecular data strongly support the population from the Biguaçu River drainage, in Santa Catarina State, as a new species. Molecular data revealed strong per-basin population structure, which may be related to species habitat specificity and low or no dispersal among drainages.

No abstract

A recent study based on genomic data by Roxo et al. (2019) provided a phylogeny of the Loricariidae, the largest catfish family and second largest Neotropical fish family with approximately 1,000 species. The study represents a valuable and innovative contribution for understanding higher-level relationships within the family. The phylogenetic tree inferred by Roxo et al. (2019) thoroughly corroborates the monophyly and relationships of most currently accepted subfamilies of Loricariidae, based on a fair taxon sampling (nearly 14% of the species in the family) representing most genera of each but one of the subfamilies, the Lithogeninae, the sister-group of the remaining members of the family (Pereira & Reis, 2017; Reis et al., 2017). In addition to a hypothesis of relationships, Roxo et al. (2019) also proposed a series of lower-level taxonomic changes, which are deemed premature considering that the taxonomic sampling of the study targeted higher-level clades, and go against one of the pillars of biological classification: nomenclatural stability (e.g., Heterick & Majer, 2018; Beninger & Backeljau, 2019). Here we (1) discuss implications of inadequate taxonomic sampling as a basis for changes in classification of species; (2) explain why the taxonomic sampling design of Roxo et al. (2019) is inadequate for the proposed nomenclatural changes; and (3) advocate that changes to classifications must be grounded on phylogenies with dense sampling of taxa at the relevant level.