Facial and opercular muscles in the Anguilliformes (Elopomorpha: Teleostei): Comparative anatomy and phylogenetic implications for the basal position of Protanguilla.

The teleost order Anguilliformes, true eels, comprises more than 1000 described species in 20 families, commonly known as eels, congers, morays, and gulper eels. Comprehensive studies of Anguilliformes are limited, resulting in a lack of consensus for morphology-based phylogenetic hypotheses. A detailed morphological analysis of the cephalic and opercular myology offers a promising new source of characters to help elucidate the intrarelationships of Anguilliformes. Our study is the most extensive myological analysis for the group and includes 97 terminal taxa, with representatives from each of the 20 families of Anguilliformes plus outgroup clades. Results demonstrate that muscle characters inform phylogenetic relationships within Anguilliformes, and we propose two new synapomorphies for all extant members, including Protanguilla palau, the "living fossil"-adductor mandibulae originating on the parietal (vs. restricted to suspensorium) and segmentum mandibularis absent (vs. present). Exceptions for the first condition characterize highly modified saccopharyngoids, and for the second one, Notacanthidae. More importantly, we suggest three new synapomorphies for the remaining extant anguilliforms (except in highly modified saccopharyngoids)-adductor mandibulae originates on the frontals (vs. frontals naked), adductor mandibulae stegalis is separated from the rictalis (vs. ricto-stegalis fused into a single piece), and the levator operculi inserts on the lateral surface of the opercle (vs. medial surface of the opercle). Our phylogenetic optimization strongly corroborates the hypothesis that Protanguilla is the sister group of all other extant eels. A further goal of this paper is to clearly document the substantive conflicts between the available molecular data and the extensive and diverse morphological evidence.

Secretive fish diversity: A new species of Listrura (Siluriformes, Trichomycteridae) from a supposedly well-known river in south-eastern Brazil.

The trichomycterid catfish Listrura menezesi, new species, is described from a flooded area adjacent to Rio das Panelas, Rio São João basin, Cachoeiras de Macacu municipality, Rio de Janeiro State, Brazil. It represents a most valuable remnant of Atlantic Forest biome that still resists the devastation of Brazilian coastlands. Listrura menezesi can be distinguished from its congeners, except L. boticario and L. depinnai, by the absence of a dorsal fin. It mainly differs from L. boticario and L. depinnai by a continuous midlateral dark stripe along the entire body (vs. discontinuous) and a longitudinal row of irregular dots along the dorsal limit of the abdomen extending for nearly the entire body (vs. only on the posterior half of the body in L. boticario and not forming a distinct row in L. depinnai). Although the new species shares with L. boticario and L. depinnai the absence of dorsal fin, recent phylogenetic analyses show a close relationship between L. menezesi and L. macaensis, the latter having a dorsal fin. A putative apomorphic condition for this clade is presented: the abrupt widening on the mesethmoid axis starting posteriorly on the horizontal through the middle region of the autopalatine (vs. anteriorly, on the horizontal through the anterior region of the autopalatine). Listrura menezesi comes as an addition to the ichthyofauna of the Rio São João drainage, a region extensively sampled for the past 20 years and supposedly well known. This paper also highlights the vulnerability of this species and the possibility of its disappearance in the near future.

Comment on "An early Miocene extinction in pelagic sharks".

Sibert and Rubin (Reports, 4 June 2021, p. 1105) report an early Miocene extinction in pelagic sharks based on the loss of shark denticle diversity in two widely separated deep-sea sediment cores. We assert that the pattern observed is not a consequence of extinction but results from shifting species ranges induced by global current reorganization.

A new catfish species of Microcambeva Costa Bockmann 1994 (Siluriformes: Trichomycteridae) from a coastal basin in Rio de Janeiro State, southeastern Brazil.

Microcambeva bendego, a small psammophilous catfish species, is described from the rio Guapi-Macacu basin at Guanabara Bay in Rio de Janeiro State, an Atlantic Forest remnant. This coastal drainage has been explored by several naturalists and fish researchers since the 19th century. It is a drainage with remarkably high endemism and species richness, and some recently-described and threatened species. The new species is distinguished from all congeners by two distinctive characters: long finger-like projections in the branchial isthmus and a large opercular patch of odontodes with 19 odontodes. Due to the paucity of specimens (n=3) osteological features of the new species were accessed by CT-Scan images of the holotype. Microcambeva bendego shares putative synapomorphies with two congeners, M. ribeirae and M. filamentosa, such as the fusion of supraorbital pore s6, the absence of ossification in the anterior autopalatine cartilage, the presence of an elongated and wide posterior process of the autopalatine, and a concavity on the dorsal process of the opercle. Those characters suggest that M. bendego is more closely related to those two species from the rio Ribeira de Iguape basin than to other congeners. The biogeography and conservation status of M. bendego are also discussed.

Iterative taxonomy reveals a new species of Trichomycterus Valenciennes 1832 (Siluriformes, Trichomycteridae) widespread in Rio Doce basin: a pseudocryptic of T. immaculatus.

This paper reports on a new species of Trichomycterus from the Rio Doce basin. Unusually for new taxa in the genus during the past few decades, the new species is not narrowly endemic but instead widely distributed in its major drainage, the Rio Doce. The species has been collected and deposited in scientific collections for some years, but has been systematically misidentified as the more abundant Trichomycterus immaculatus or, to a lesser degree, as other morphologically similar species from south-eastern Brazil such as T. nigricans and T. pradensis. A combination of several morphological characteristics, such as vertebral number, pectoral-fin ray counts, pigmentation pattern and barcoding distance, were iteratively used and unambiguously distinguish the new species from all congeners. The present case reveals a pattern of diversity-discovery in which rare and narrowly endemic morphologically conspicuous species are discovered and described before visually inconspicuous taxa, even when the latter are more abundant and widespread. The morphological similarities among south-eastern Brazilian species with a uniform dark-grey color serve as basis for a brief discussion about the concepts of cryptic and pseudo-cryptic species in Trichomycterus and their consequences for potentially hidden diversity in the genus.

The type specimens of Trichomycterus alternatus (Eigenmann, 1917) and Trichomycterus zonatus (Eigenmann, 1918), with elements for future revisionary work (Teleostei: Siluriformes: Trichomycteridae).

The trichomycterid catfish species Trichomycterus alternatus (Eigenmann, 1917) and Trichomycterus zonatus (Eigenmann, 1918) are reportedly among the most pervasive species in mid- to high-elevation coastal streams of Southeastern Brazil. Despite their apparent abundance and ecological ubiquity, the applicability of their names is still uncertain. Examination of the type material of the two species reveals that part of the confusion stems from a mixing of species in the T. zonatus type series. Other issues relate to reports of character conditions in the respective species that do not actually correspond to the situation in their type specimens. Such situation triggered a long-lasting chain of taxonomic misinterpretations and erroneous identification protocols and traditions so that even the taxonomic distinctiveness of the two species is nebulous. That situation is disentangled in detail on the basis of new information on the holotypes and remaining type specimens of each species by classical and new (stereo triplet radiography) morphology analyses for data acquisition. Results show that the type specimens of T. alternatus and T. zonatus differ pronouncedly in several traits of internal and external morphology and represent markedly distinct taxa. The latter species does not correspond to most identifications in the literature and is, in fact, endemic to the region of its type locality. We also clarify and map the reported localities of the type material and offer comments on the validity of T. alternatus and T. zonatus, along with that of possibly related forms.

A new species of Cetopsis from the Guiana Shield (Siluriformes: Cetopsidae: Cetopsinae).

A new species of Cetopsis is described from Guiana Shield drainages in Guyana and Suriname. The new species is found in the Konawaruk River and tributaries, Essequibo River basin, Guyana, and in the Mauritie Creek, tributary to the Tempati River, upper Commewijne River basin, Suriname. The new taxon can be distinguished from all congeners by a combination of features: dark spots on sides of the body eye-sized or larger, dark, bilobed patch at the base of the caudal fin, absence of a dark humeral spot, absence of dark pigmentation along the fin-membrane posterior to the first dorsal-fin ray, dark pigmentation at the base of the dorsal fin, dark spots extending ventrally to the bases of anal-fin rays, and 41 total vertebrae with 28 caudal vertebrae. Data on internal anatomy of the new species were incorporated into a previously-published phylogenetic analysis and resolves the position of the new species as the sister group of C. motatanensis, from Lago Maracaibo basin. The new Cetopsis is the first species of the genus known to occur exclusively in the Guiana Shield.

A new species of Trichomycterus Valenciennes 1832 (Trichomycteridae: Siluriformes) from the Rio Doce drainage with remarkable similarities with Bullockia and a CT-scan survey.

A new species of Trichomycterus is described from rocky and psammic sectors near the main channel of the middle and upper Rio Doce basin in Southeastern Brazil. Trichomycterus astromycterus n. sp., is distinguished from all congeners by a number of autapomorphic characters, such as the distally expanded maxilla; the short and thick mesethmoid cornua; and the elongated anterior process of the vomer. Additional characters (short barbels, large head, 33 vertebrae, ii+8 or ii+9 dorsal-fin rays, nine dorsal-fin pterygiophores, markedly enlarged lips, narrow caudal peduncle, bilobed caudal fin with the lower lobe longer than the upper one) also distinguish the new species from all its congeners in Southeastern Brazil and from most congeners anywhere. Examination of internal anatomy reveals that T. astromycterus shares some intriguing characteristics with the austral genus Bullockia Arratia et al., 1978. However, the phylogenetic significance of such similarities is still uncertain and will require further comparative study. For this reason, the new species is provisionally included in the all-encompassing genus Trichomycterus. An osteological description is presented on the basis of CT-scan imaging and cleared and stained specimens.

Poor taxonomic sampling undermines nomenclatural stability: A reply to Roxo et al. (2019).

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.

Distribution, morphological notes and conservation status of the psammophilus Microcambeva catfishes (Siluriformes: Trichomycteridae).

Sarcoglanidinae and Glanapteryginae catfishes are among the most unusual elements of the Neotropical freshwater fish fauna. Microcambeva ribeirae, M. barbata and M. draco are miniaturized Sarcoglanidinae known to occur in sandy microhabitats in drainages of the Brazilian Atlantic Forest. Due to their specific habitats, specimens of Microcambeva are rare in fish collections, and new records are considered noteworthy to warrant report. Recently, specimens of this genus were newly found in the Rio Doce basin in Minas Gerais and Espírito Santo States. Such new records expand the known geographic distribution of Microcambeva. Further records of Microcambeva for Rio Peruípe in south Bahia State are also reported. Comments on the distribution of Microcambeva species along the Atlantic Forest coastal basins and suggestions on its conservation status are also offered.

Cetopsis varii, a new species of whale catfish (Siluriformes: Cetopsidae) from the Meta Basin, Colombia.

Cetopsis varii sp. nov. Cetopsidae (Cetopsinae) is described from the Río Meta basin in eastern Colombia, at middle portions of the Río Orinoco basin. The new species differs from congeners by a combination of features: the absence of a humeral spot, presence of eye, conical teeth on vomer and dentary and rounded posterior nares, along with details of body, dorsal and caudal-fin pigmentation. The osteology of the new species is investigated through high-resolution X-ray computed tomography and cleared and stained specimens. Data thus obtained are used to code the new species for character states utilized in a previous phylogenetic analysis of Cetopsidae. Analysis of the expanded matrix shows that C. varii is the sister group to C. orinoco.

Phylogeographic patterns in suckermouth catfish Hypostomus ancistroides (Loricariidae): dispersion, vicariance and species complexity across a Neotropical biogeographic region.

The upper Paraná River system (UP) is a highly diverse biogeographic province for freshwater fishes, but little is known about processes which shaped that diversity. This study describes the phylogeographic pattern in Hypostomus ancistroides, a suckermouth catfish species that is widespread in the UP and also reported from the adjoining Ribeira do Iguape basin. We used complete mtDNA sequences of ATPase 6/8 of 162 specimens to infer haplotype distribution using phylogenetic and demographic analyses and a Bayesian molecular clock. Results suggest that during the Quaternary H. ancistroides has undergone superimposed phylogeographic histories, alternating between isolation and subsequent merging of different populations. Occurrence of an isolated population on the Ribeira de Iguape is demonstrated to be a Pleistocene headwater capture event. Widely distributed haplotypes indicate deep genetic differences and suggest that populations of H. ancistroides were isolated for considerable time, but did not undergo speciation because of recurrent population mixing.

The infrabranchial musculature and its bearing on the phylogeny of percomorph fishes (Osteichthyes: Teleostei).

The muscles serving the ventral portion of the gill arches ( = infrabranchial musculature) are poorly known in bony fishes. A comparative analysis of the infrabranchial muscles in the major percomorph lineages reveals a large amount of phylogenetically-relevant information. Characters derived from this anatomical system are identified and discussed in light of current hypotheses of phylogenetic relationships among percomorphs. New evidence supports a sister-group relationship between the Batrachoidiformes and Lophiiformes and between the Callionymoidei and Gobiesocoidei. Investigated data also corroborate the existence of two monophyletic groups, one including the Pristolepididae, Badidae, and Nandidae, and a second clade consisting of all non-amarsipid stromateiforms. New synapomorphies are proposed for the Atherinomorphae, Blenniiformes, Lophiiformes, Scombroidei (including Sphyraenidae), and Gobiiformes. Within the latter order, the Rhyacichthyidae and Odontobutidae are supported as the successive sister families of all remaining gobiiforms. The present analysis further confirms the validity of infrabranchial musculature characters previously proposed to support the grouping of the Mugiliformes with the Atherinomorphae and the monophyly of the Labriformes with the possible inclusion of the Pholidichthyiformes. Interestingly, most hypotheses of relationships supported by the infrabranchial musculature have been advanced by preceding anatomists on the basis of distinct data sources, but were never recovered in recent molecular phylogenies. These conflicts clearly indicate the current unsatisfactory resolution of the higher-level phylogeny of percomorphs.

About nothing.

In light of recent terminological controversy, this article reviews cladistic conceptions of character states coded as absences, symplesiomorphies, and secondary losses. The first section addresses absence as a question of ontology vs. epistemology. The second and third sections address the evidentiary status of symplesiomorphy in cladistics, the fourth contrasts primitive absence with secondary loss, and the fifth clarifies the meaning of "grouping". While secondary losses (reversals) are often synapomorphies, symplesiomorphies ("absent" or otherwise) have no evidentiary import to cladistic hypotheses of relationship. Thus, we argue that identifying symplesiomorphic character states as "homologous" is conceptually vacuous, because they are either synapomorphies (homologues) of more inclusive taxa, or complementary absences that unite no group.

Homology and errors.

A recent review of the homology concept in cladistics is critiqued in light of the historical literature. Homology as a notion relevant to the recognition of clades remains equivalent to synapomorphy. Some symplesiomorphies are "homologies" inasmuch as they represent synapomorphies of more inclusive taxa; others are complementary character states that do not imply any shared evolutionary history among the taxa that exhibit the state. Undirected character-state change (as characters optimized on an unrooted tree) is a necessary but not sufficient test of homology, because the addition of a root may alter parsimonious reconstructions. Primary and secondary homology are defended as realistic representations of discovery procedures in comparative biology, recognizable even in Direct Optimization. The epistemological relationship between homology as evidence and common ancestry as explanation is again emphasized. An alternative definition of homology is proposed. © The Willi Hennig Society 2012.