Phylogenetic significance of clasper morphology of electric rays (Chondrichthyes: Batoidea: Torpediniformes).

Torpediniformes (electric rays) is a monophyletic group strongly supported by morphological and molecular phylogenetic studies. The claspers of electric rays, however, are poorly documented in comparation to the clasper of other batoids, especially skates, and the knowledge of their anatomical variation is restricted to the description of a few species. The present article analyzes the external and skeletal clasper anatomy of electric rays and reports newly discovered characters that can be useful for taxonomic diagnoses and higher-level systematic studies. The family Torpedinidae exclusively presents the integumental flap, a poorly calcified clasper skeleton, and a dorsal marginal cartilage with a medial flange on its distal portion. Derived or diagnostic characters were not found in the clasper of the reportedly nonmonophyletic families Narcinidae and Narkidae; however, the claspers of species and genera of narcinids and narkids present different anatomical patterns that can be useful for taxonomic and phylogenetic studies.

Clasper Morphology of the Japanese Sawshark, Pristiophorus japonicus Günther, 1870 (Chondrichthyes: Elasmobranchii).

Sawsharks (Pristiophoriformes) are slender, medium-sized sharks with elongated, saw-like snouts, and include the monotypic Pliotrema and Pristiophorus with seven species. The phylogenetic position of sawsharks is still problematic as phylogenetic hypotheses based on morphological and molecular evidence disagree about their relationships, whether closer to batoids (morphological data) or grouped with squaliforms, angelsharks, and hexanchiforms in an all shark higher taxon (molecular data). However, many aspects of the morphology of sawsharks are poorly known. The present article describes the clasper musculature and skeleton of a sawshark (Pristiophorus japonicus); the clasper skeleton of a sawshark is described for the first time. The clasper musculature is similar to squaliforms and most batoids, whereas the clasper skeleton is similar to that found in Squatina and Squalus. However, the ventral marginal, dorsal terminal (dt), and ventral terminal cartilages are distinct and diagnostic at least for Pristiophorus japonicus. Comparisons with galeomorph sharks are necessary to further refine our conclusions in relation to the systematic significance of the clasper muscles and skeleton of the Japanese sawshark. Anat Rec, 302:1666-1670, 2019. © 2019 American Association for Anatomy.

Morphology of the clasper musculature in rays (Chondrichthyes; Elasmobranchii: Batoidea), with comments on their phylogenetic interrelationships.

The subclass Batoidea comprise skates, electric rays, stingrays, guitarfishes, and sawfishes, and their interrelationships are still problematical despite recent morphological and molecular phylogenetic studies. The most recent morphological phylogeny indicates that guitarfishes are a polyphyletic group, and that the phylogenetic placement of Platyrhina and Platyrhinoidis is still unclear. Several molecular studies suggest that guitarfishes (except Zanobatus) and sawfishes comprise the monophyletic order Rhinopristiformes, and that thornback rays (Platyrhinidae, Platyrhina, and Platyrhinoidis) are more closely related to the electric rays (Torpediniformes); rhinopristiforms have recently been supported by morphological data as well. The clasper musculature of batoids suggests an alternative pattern of interrelationships for thornback rays, with the m. dilatator attached to the dorsal terminal 1 cartilage by a series of tendons found only in Rhinopristiformes and Platyrhinidae, suggesting that they are closely related. Furthermore, Rajiformes, Rhinopristiformes, and Platyrhinidae exclusively share a reduced m. extensor lateralis, suggesting that these taxa form a monophyletic group. This study identifies new synapomorphies that corroborate the separate monophyly of Rajiformes, Torpediniformes, and Myliobatiformes: the m. dilatator divided into dorsal and ventral bundles and the presence of a single m. flexor are found only in Rajiformes; the extensor lateralis with a laminar shape is a derived character of Torpediniformes; and the exclusive m. flexor medialis arising on the puboischiadic bar is derived for Myliobatiformes.

Comparative anatomy of the clasper of the subfamily Potamotrygoninae (Chondrichthyes: Myliobatiformes).

Claspers of stingrays (Myliobatiformes) are poorly documented in comparison to claspers of skates, with our knowledge restricted mainly to external morphological characters and skeletal components included in descriptions of new species; more encompassing morphological comparative analyses are lacking. Concerning potamotrygonins, clasper morphology has been described for a handful of species, but without elucidating their variation and systematic potential. The present article analyzed clasper structures in all genera of the subfamily Potamotrygoninae (Potamotrygon, Paratrygon, Plesiotrygon, and Heliotrygon), which were compared to the clasper of Styracura and some dasyatid genera. Potamotrygon shows some morphometric variation among the species analyzed. Anatomically, we found variation mainly in the dorsal terminal 1 and accessory terminal 1 cartilages, which are considered diagnostic among potamotrygonin genera; external morphological structures did not present significant differences among potamotrygonins.

Clasper morphology of skates of the tribe Riorajini (Chondrichthyes: Rajiformes: Arhynchobatidae) and its systematic significance.

Claspers of adult specimens of the skate tribe Riorajini, family Arhynchobatidae, comprising Atlantoraja and Rioraja, are described, compared, and systematically reinterpreted based on material collected off southeastern and southern Brazil. For the first time the external components and musculature of the clasper of members of this tribe are described and related to internal (skeletal) structures. The component pecten is present in all species of Atlantoraja but absent in Rioraja. The new external component grip, an autapomorphy of A. cyclophora fully developed in adults, is described. Rioraja presents dorsal terminals 1 and 2, ventral marginal distally extended and ventral terminal cartilages. Dorsal terminals 1 and 2, ventral marginal distally extended, accessory terminals 2 and 3, and ventral terminal cartilages occur in Atlantoraja. A new interpretation of the ventral marginal distally extended is discussed. The dorsal terminal 1 of Atlantoraja has an inverted U shape but is triangular in Rioraja. The accessory terminal 2 cartilage is reported for the first time in Atlantoraja cyclophora. The accessory terminal 3 is present only in A. platana and A. cyclophora, and absent in Rioraja and A. castelnaui. Many of our findings concerning the clasper skeleton do not agree with previous interpretations. The arrangement, distribution and systematic significance of many of the terminal clasper components are discussed among rajoids.

Systematic implications of brain morphology in potamotrygonidae (Chondrichthyes: Myliobatiformes).

The gross brain morphology, brain proportions, and position of cranial nerves in all four genera (Potamotrygon, Plesiotrygon, Paratrygon, and Heliotrygon) and 11 of the species of the Neotropical stingray family Potamotrygonidae were studied to provide new characters that may have a bearing on internal potamotrygonid systematics. The brain was also studied in four other stingray (Myliobatiformes) genera (Hexatrygon, Taeniura, Dasyatis, and Gymnura) to provide a more inclusive phylogenetic context for the interpretation of features of the brain in potamotrygonids. Our results indicate, based on neuroanatomical characters, that the genera Paratrygon and Heliotrygon are sister groups, as are the genera Potamotrygon and Plesiotrygon, agreeing with previous morphological and molecular phylogenetic studies. Both groups of genera share distinct conditions of the olfactory tracts, telencephalon and its central nuclei, hypophysis and infundibulum, morphology and orientation of the metencephalic corpus cerebelli, orientation of the glossopharyngeal nerve, and overall encephalic proportions. The corpus cerebelli of Paratrygon and Heliotrygon is interpreted as being more similar to the general batoid condition and, given their phylogenetic position highly nested within stingrays, is considered secondarily derived, not plesiomorphically retained. Our observations of the corpus cerebelli of stingrays, including Hexatrygon, corroborate that the general stingray pattern previously advanced by Northcutt is derived among batoids. The morphology of the brain is shown to be a useful source of phylogenetically informative characters at lower hierarchical levels, such as between genera and species, and thus, has significant potential in phylogenetic studies of elasmobranchs.

Tetronarce cowleyi, sp. nov., a new species of electric ray from southern Africa (Chondrichthyes: Torpediniformes: Torpedinidae).

A new species of torpedo ray, Tetronarce cowleyi, sp. nov., is described from specimens collected from the southeastern Atlantic Ocean. The new species is placed in the genus Tetronarce based on a uniform dorsal coloration and absence of papillae around the spiracles. The new species is distinguished from its closest congeners, the North Atlantic Tetronarce nobiliana Bonnaparte, 1835, and southwestern Atlantic Tetronarce puelcha Lahille, 1926, by a combination of morphological characteristics including a shorter spiracular length, a proportionally greater head length as measured between snout margin and fifth gill openings, a proportionally greater preoral snout length, a uniform shiny black or dark gray dorsal surface, lacking any prominent markings, and a creamy white ventral color with dark edges in juveniles but fading with growth. Teteronarce cowleyi, sp. nov., is further distinguished from T. nobiliana by its more circular anterior disc shape (vs. relatively straight in T. nobiliana), fewer tooth rows (32/28 vs. 38-53/38-52 in T. nobiliana), greater mouth width (1.5-1.7 times as great as interorbital width vs. 0.5-0.6 times interorbital width in T. nobiliana), smaller distance between second dorsal and caudal fins (3.5-4.9% vs. 6.6-6.8% in T. nobiliana), and a clasper length extending nearly to lower caudal fin origin (claspers in T. nobiliana that extend only two-thirds distance between second dorsal and caudal fins). Teteronarce cowleyi, sp. nov., is known from Walvis Bay, Namibia to Algoa Bay, Eastern Cape, South Africa, at depths of 110 to 457 m.

Potamotrygon limai, sp. nov., a new species of freshwater stingray from the upper Madeira River system, Amazon basin (Chondrichthyes: Potamotrygonidae).

Potamotrygon limai, sp. nov., is described from the Jamari River, upper Madeira River system (Amazon basin), state of Rondônia, Brazil. This new species differs from congeners by presenting unique polygonal or concentric patterns formed by small whitish spots better defined over the posterior disc and tail-base regions. Potamotrygon limai, sp. nov., can be further distinguished from congeners in the same basin by other characters in combination, such as two to three rows of midtail spines converging to a single irregular row at level of caudal sting origin, proportions of head, tail and disc, patterns of dermal denticles on rostral, cranial and tail regions, among other features discussed herein. Potamotrygon limai, sp. nov., is most similar to, and occurs sympatrically with, P. scobina, and is distinguished from it by lacking ocellated spots on disc, by its characteristic polygonal pattern on posterior disc, a comparatively much shorter and broader tail, greater intensity of denticles on disc, more midtail spine rows at tail-base, and other features including size at maturity and meristic characters. Potamotrygon limai, sp. nov., is also distinguished from other species of Potamotrygon occurring in the Amazon region, except P. scobina, by presenting three angular cartilages (vs. two or one). This new species was discovered during a detailed taxonomic and morphological revision of the closely related species P. scobina, and highlights the necessity for thorough and all-embracing taxonomic studies, particularly in groups with pronounced endemism and morphological variability.

Does counting species count as taxonomy? On misrepresenting systematics, yet again.

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.

Mandibular and hyoid muscles of Galeomorph sharks (Chondrichthyes: Elasmobranchii), with remarks on their phylogenetic intrarelationships.

The superorder Galeomorph comprises the orders Heterodontiformes, Orectolobiformes, Lamniformes, and Carcharhiniformes. Recent morphological and molecular support that it is a monophyletic taxon. The phyletic relationship within the Galeomorphi are also well resolved. However, only few morphological characters of the mandibular and hyoid muscles have been employed, and a detailed description of these muscles and their variations may contribute new interpretations of homology and to the discussion of different hypothesis of intrarelationships. This paper provides a detailed description of mandibular and hyoid arch muscles in galeomorph sharks, within a comparative elasmobranch framework, with the objective to discuss putative homologies that may elucidate our understanding of galeomorph evolution. Twenty-eight galeomorph species were dissected, described, illustrated and compared with other elasmobranchs and with data from the literature. The Galeomorphi are supported as monophyletic by presenting the m. levator labii superioris attached directly to the neurocranium, different from the attachment through a tendon in basal squalomorphs. Heterodontiformes and Orectolobiformes share particular variations in the position and insertion of the m. levator labii superioris and the presence of a well-defined m. levator hyomandibulae. Lamniformes and Carcharhiniformes show similar patterns in the position and attachment of the m. levator labii superioris, subdivision of the m. adductor mandibulae, and the presence of an almost indivisible m. levator hyomandibulae and m. constrictor hyoideus dorsalis, similar to the condition, albeit independently, in basal squalomorphs. No specific mandibular or hyoid arch muscle character was found to support the clade composed of Orectolobiformes, Lamniformes, and Carcharhiniformes, as advocated by recent phylogenetic analyses.

Introduction to the systematics and biodiversity of sharks, rays, and chimaeras (Chondrichthyes) of Taiwan.

All 13 orders of chondrichthyan fishes occur in Taiwanese waters, representing 52 chondrichthyan families (31 shark, 19 batoid, 2 chimaeroid) and 98 genera (64 shark, 31 batoid, 3 chimaeroid). A total of 119 shark, 58 batoid, and 4 chimaera species may occur in the waters surrounding Taiwan, pending taxonomic resolution of some groups. Of the 34 nominally described species from Taiwan, 17 are currently considered valid. The majority of named species occurred during two peak periods in Taiwanese chondrichthyan research; the first between 1959-63, when 13 nominal species were described, of which 7 remain valid today, and a second peak period between 2003-13 when 9 nominal species were described, of which 6 remain valid. The overall species diversity of Taiwan's chondrichthyan fauna is comparable to that of other adjacent marine zoogeographic hotspots, e.g. Japan (126 shark, 75 batoid, 11 chimaeroid species) and the Philippines (81 shark, 46 batoid, 2 chimaeroid species). The Carcharhiniformes, Squaliformes, Myliobatiformes, and Rajiformes are the most dominant orders in terms of abundance and species-richness within this region. Each of these groups may increase in relative diversity with improved taxonomic resolution resulting from the incorporation of molecular tools and renewed morphological studies. Improved identification of Taiwan's chondrichthyan fauna will aid in developing better conservation and management practices.

An annotated checklist of the chondrichthyans of Taiwan.

An annotated checklist of chondrichthyan fishes (sharks, batoids, and chimaeras) occurring in Taiwanese waters is presented. The checklist is the result of a biodiversity workshop held in Mach 2012 as well as on-going systematic revisions by the authors. The chondrichthyan fauna of Taiwan is one of the richest in the world with the number of species totaling 181, comprising 52 families and 98 genera. It includes 31 families, 64 genera, and 119 species of sharks, 19 families, 31 genera, and 58 species of batoids, and 2 families, 3 genera, and 4 species of chimaeras. The most species-rich families are the Carcharhinidae with 22 species followed by the Scyliorhinidae with 17. The most species-rich batoid families are the Dasyatidae with 11 species and and the Rajidae with 10. Verified voucher material is provided for each species where available and potential taxonomic issues are high-lighted when applicable. This represents the first detailed, evidence-based checklist of chondrichthyans from Taiwanese waters in over 40 years.

Nomenclatural and taxonomic problems related to the electronic publication of new nomina and nomenclatural acts in zoology, with brief comments on optical discs and on the situation in botany.

In zoological nomenclature, to be potentially valid, nomenclatural novelties (i.e., new nomina and nomenclatural acts) need first to be made available, that is, published in works qualifying as publications as defined by the International Code of zoological Nomenclature ("the Code"). In September 2012, the Code was amended in order to allow the recognition of works electronically published online after 2011 as publications available for the purpose of zoological nomenclature, provided they meet several conditions, notably a preregistration of the work in ZooBank. Despite these new Rules, several of the long-discussed problems concerning the electronic publication of new nomina and nomenclatural acts have not been resolved. The publication of this amendment provides an opportunity to discuss some of these in detail. It is important to note that: (1) all works published only online before 2012 are nomenclaturally unavailable; (2) printed copies of the PDFs of works which do not have their own ISSN or ISBN, and which are not obtainable free of charge or by purchase, do not qualify as publications but must be seen as facsimiles of unavailable works and are unable to provide nomenclatural availability to any nomenclatural novelties they may contain; (3) prepublications online of later released online publications are unavailable, i.e., they do not advance the date of publication; (4) the publication dates of works for which online prepublications had been released are not those of these prepublications and it is critical that the real release date of such works appear on the actual final electronic publication, but this is not currently the case in electronic periodicals that distribute such online prepublications and which still indicate on their websites and PDFs the date of release of prepublication as that of publication of the work; (5) supplementary online materials and subsequent formal corrections of either paper or electronic publications distributed only online are nomenclaturally unavailable; (6) nomenclatural information provided on online websites that do not have a fixed content and format, with ISSN or ISBN, is unavailable. We give precise examples of many of these nomenclatural problems. Several of them, when they arise, are due to the fact that the availability of nomenclatural novelties now depends on information that will have to be sought not from the work itself but from extrinsic evidence. As shown by several examples discussed here, an electronic document can be modified while keeping the same DOI and publication date, which is not compatible with the requirements of zoological nomenclature. Therefore, another system of registration of electronic documents as permanent and inalterable will have to be devised. ZooBank also clearly needs to be improved in several respects. Mention in a work of its registration number (LSID) in ZooBank would seem to be possible only if this registration has occurred previously, but some works that have purportedly been registered in ZooBank are in fact missing on this web application. In conclusion, we offer recommendations to authors, referees, editors, publishers, libraries and the International Commission on Zoological Nomenclature, in the hope that such problems can be limited along with the potential chaos in zoological nomenclature that could result, if careful attention is not paid to the problems we highlight here, from a somewhat misplaced, and perhaps now widespread, understanding that electronic publication of nomenclatural novelties is now allowed and straightforward. We suggest that, as long as the problematic points linked to the new amendment and to electronic publication as a whole are not resolved, nomenclatural novelties continue to be published in paper-printed journals that have so far shown editorial competence regarding taxonomy and nomenclature, which is not the case of several recent electronic-only published journals.

Morphological and taxonomic revision of species of Squatina from the Southwestern Atlantic Ocean (Chondrichthyes: Squatiniformes: Squatinidae).

The morphology and taxonomy of species of Squatina from the southwestern Atlantic Ocean are revised. Species previously considered valid, Squatina argentina (Marini, 1930), Squatina guggenheim Marini, 1936 and Squatina occulta Vooren and da Silva, 1991, are investigated and described in detail, including a morphometric and meristic study of specimens from their recorded range. The taxonomic status of the doubtful nominal species Squatina punctata Marini, 1936 was also evaluated. This species was previously considered a junior synonym of S. argentina, a junior synonym of S. guggenheim, or a senior synonym of S. occulta. Although there is much morphological similarity between Squatina species, significant differences in dermal denticle patterns, dorsal coloration, tooth formula, and size at maturity are reported, enabling the recognition of S. argentina, S. guggenheim and S. occulta as valid species, and relegating S. punctata to the synonymy of S. guggenheim. Differences in skeletal morphology between valid species are described and considered supportive of the taxonomic hypothesis, corroborating a previous study of neurocrania. Additionally, an unidentified specimen is reported, as Squatina sp., from the continental shelf of Bahia state, Brazil, recognized by having more vertebral centra and a conspicuous dermal denticle morphology on interspiracular region, features not present in other South America angelshark species. A report on the only known syntype of Squatina dumeril Le Sueur, 1818 is presented, describing features that are still preserved and designating it as lectotype. Lateral-line sensory canals, skeleton, and cranial and hypobranchial muscles for the three valid species of Squatina from the southwestern Atlantic, as well as the brain and cranial nerves of S. guggenheim, are described and illustrated.

Comparative myology of the mandibular and hyoid arches of sharks of the order hexanchiformes and their bearing on its monophyly and phylogenetic relationships (Chondrichthyes: Elasmobranchii).

The order Hexanchiformes currently comprises two families, Chlamydoselachidae (frilled sharks) and Hexanchidae (six- and seven-gill sharks), but its monophyly and relationships with other elasmobranchs are still discussed. Previous studies of hexanchiforms addressing these issues were based mainly on external morphology, teeth, skeletal features, and molecular data, whereas the employment of characters derived from variations in muscles has not been significantly explored. Dissections of four species of Hexanchiformes (including Chlamydoselachus anguineus) are reported here describing the mandibular (musculus adductor mandibulae dorsalis, m. adductor mandibulae ventralis, m. levator labii superioris, m. intermandibularis, and m. constrictor dorsalis) and hyoidean (m. constrictor hyoideus dorsalis and ventralis) arch muscles. Our results provide new data concerning the relationships of hexanchiforms to other elasmobranchs. The m. adductor mandibulae superficialis is described and illustrated in C. anguineus, contradicting previous accounts in which is was considered absent. The anteroposterior orientation of the m. adductor mandibulae superficialis in Chlamydoselachus is similar to the pattern found in hexanchids, squaloids, and hypnosqualeans (including batoids), suggesting it was secondarily lost in Echinorhinus. This muscle therefore provides further support for the inclusion of the Chlamydoselachidae and Hexanchidae in the Squalomorphi, and not basal to all other elasmobranchs or nested within an all-shark collective, as has been previously proposed. However, the m. adductor mandibulae superficialis originating at the jaw joint and with an aponeurotic insertion in hexanchids, squaliforms, and hypnosqualeans, may be a separate derived feature uniting these taxa. The insertion of the m. constrictor dorsalis is restricted to the postorbital articulation in hexanchids, whereas it extends farther anteriorly in C. anguineus. The insertion of the m. constrictor hyoideus dorsalis solely on the palatoquadrate is found exclusively in the Hexanchidae. We conclude that no specific pattern of mandibular or hyoid arch muscles support the monophyly of hexanchiforms (i.e., including Chlamydoselachus).

Modeling the skin pattern of fishes.

Complicated patterns showing various spatial scales have been obtained in the past by coupling Turing systems in such a way that the scales of the independent systems resonate. This produces superimposed patterns with different length scales. Here we propose a model consisting of two identical reaction-diffusion systems coupled together in such a way that one of them produces a simple Turing pattern of spots or stripes, and the other traveling wave fronts that eventually become stationary. The basic idea is to assume that one of the systems becomes fixed after some time and serves as a source of morphogens for the other system. This mechanism produces patterns very similar to the pigmentation patterns observed in different species of stingrays and other fishes. The biological mechanisms that support the realization of this model are discussed.