John D. McEachran

Phylogenetic Analysis of Skates, a Morphologically Conservative Clade of Elasmobranchs (Chondrichthyes: Rajidae)

Skates (Rajidae) are unique among chondrichthyans for their high species diversity and morphological conservatism. To elucidate phylogenetic interrelationships within this taxon, we surveyed a wide range of morphological character complexes under the premise that characters within different character complexes are constrained in different ways and would thus reveal a robust phylogeny. Maximumparsimony analysis employing 31 taxa, including three outgroups, and 55 characters produced 20 equally parsimonious trees of 160 steps (consistency index = 0.681, retention index = 0.850, homoplasy index = 0.462, and rescaled consistency index = 0.579). The strict consensus tree divided rajids into two major clades. The first, Rajinae, consisted of two partially resolved clades and one fully resolved clade and was defined by three ambiguous character states: (1) scapulocoracoids that lack an anterior bridge; (2) claspers that are distally expandible; and (3) claspers that possess the component rhipidion. The taxon comprises three tribes, 15 genera (seven elevated from subgenera of Raja and GurgesieUa), and 149 species. The second major clade, Arhynchobatinae, was nearly fully resolved and was defined by two unambiguous character states: (1) basihyal cartilages that possess lateral extensions; and (2) claspers that possess the component projection. The taxon comprises two tribes, 11 genera, two genera elevated from subgenera of Raja, and 79 species. The strict consensus tree revealed considerable parallelisms in morphological evolution within rajids. Some parallelisms, such as reduction of the rostral cartilage and concomitant forward extension of pectoral radials and muscles and enlarged nasal capsules, appear to be adaptations for deep-sea benthic habitats. The closest relatives of rajids, Rhinobatos, Zapteryx, and Trygonorrhina, are limited to shallow water. Thus, it is likely that ancestral rajids had a similar habitat and that subsequently rajids made multiple radiations into the deep sea and developed flexible snouts for grubbing in soft substrates and enlarged nasal rosettes for increased chemosensistivty in regions with little light.

Taxonomic Impediment or Impediment to Taxonomy? A Commentary on Systematics and the Cybertaxonomic-Automation Paradigm

Marcelo R. de Carvalho AE Flavio A. Bockmann AE Dalton S. Amorim AE Carlos Roberto F. Brandao AE Mario de Vivo AE Jose L. de Figueiredo AE Heraldo A. Britski AE Mario C. C. de Pinna AE Naercio A. Menezes AE Fernando P. L. Marques AE Nelson Papavero AE Eliana M. Cancello AE Jorge V. Crisci AE John D. McEachran AE Robert C. Schelly AE John G. Lundberg AE Anthony C. Gill AE Ralf Britz AE Quentin D. Wheeler AE Melanie L. J. Stiassny AE Lynne R. Parenti AE Larry M. Page AE Ward C. Wheeler AE Julian Faivovich AE Richard P. Vari AE Lance Grande AE Chris J. Humphries AE Rob DeSalle AE Malte C. Ebach AE Gareth J. Nelson

Molecular phylogenetics of myliobatiform fishes (Chondrichthyes: Myliobatiformes), with comments on the effects of missing data on parsimony and likelihood

Mitochondrial DNA sequences from the 12S rRNA gene, four tRNA genes, and a portion of two protein coding genes were used to investigate the relationship of myliobatoid genera. In addition, we conducted an investigation of the sister group to the freshwater stingrays by sampling additional DNA sequences from GenBank. Consequently, two datasets were used to examine myliobatoid relationships. The first consisted of the genes sequenced in this study. The second dataset was compiled by combining the first dataset with cytochrome b sequences from GenBank. The second dataset, however, included a number of missing characters due to differences in sampling. The effect of the missing characters on both maximum parsimony and maximum likelihood analysis was investigated by conducting a simulation study. Results of the simulation study indicated that maximum likelihood was not sensitive to the missing data, whereas the accuracy of maximum parsimony analysis was expected to decrease. Phylogenetic analysis of this group had several areas concordant with morphological studies, however, the analysis also revealed two novel relationships. In addition, placement of two taxa (Gymnura and Himantura) were dependent both on the dataset and analytical method used.

Survey of the variation in alar and malar thorns in skates: Phylogenetic implications (Chondrichthyes: Rajoidei)

A total of 62 species, representing 24 of the 28 supraspecific taxa of skates, was surveyed for the presence, distribution, and structure of alar and malar thorns. The survey revealed that alar thorns are almost universally present in mature male skates, and that malar thorns are of two types that may have separate origins. The location and orientation of alar thorns differed in two major clades of skates (groups I and II). They were either exposed on the disc with the crown oriented obliquely to the long axis of the base or imbedded in slits in the integument and oriented parallel to the long axis of the base. Group I possessed the former type of thorns and, with several exceptions, group II possessed the latter type. Group I either lacked malar thorns or possessed malar thorns that were most likely derived from generalized placoid scales. Group II possessed, with several exceptions, malar thorns derived from enlarged placoid scales. Within group I the supraspecific taxa Atlantoraja and Rioraja possessed unique alar thorns that were reclined laterally and associated with lateral grooves in the integument. Within group II the supraspecific taxa Anacanthobatis, Cruriraja, Dipturus, Okamejei, Raja, the North Pacific Assemblage, and the Amphi‐American Assemblage had a large barb on the distal section of the crown of the alar thorn that suggests that these taxa form a clade. The crown of the alar thorns of the latter five supraspecific taxa was undulatory, thus supporting their monophyletic status. Another assemblage within group II had ridges that ran most of the length of the crown of the alar thorns corroborating their monophyletic status. The survey also suggested that variation of integumentary grooves associated with the alar thorns in Bathyraja, and presence or absence of malar thorns in Psammobatis, may be phylogenetically informative.

Possible occurrence of character displacement in the sympatric skates Raja erinacea and R. ocellata (Pisces: Rajidae)

SynopsisRaja erinacea and R. ocellata are sibling species which are positively correlated with each other by occurrence and numerical abundance. In sympatry the species undergo interactive segregation; R. erinacea feeds on a higher percentage of epifauna and R. ocellata feeds on a higher percentage of infauna.An isolated allopatric population of R. ocellata occurs in the Gulf of St. Lawrence which is phenotypically intermediate between the sympatric populations of R. erinacea and R. ocellata in characters related to feeding e.g. size, number of tooth rows in the upper jaw, and shape of the upper jaw. It appears probable that the allopatric population represents the morphological state of R. ocellata before it became sympatric with R. erinacea; divergence in size, number of tooth rows, and shape of the upper jaw between the two species developed after establishment of sympatry. These divergences in character traits, related to feeding, reduced competition between the two sympatric species and permitted the present wide overlap in their ranges.Character displacement is evidently rare in demersal fishes inhabiting the flat and soft bottoms of the northwestern Atlantic because the three other pairs of sibling species that occur there are parapatrically distributed and thus would not compete for resources. Raja erinacea and R. ocellata may have been restrained from establishing parapatry by another species pair of skates (R. senta and R. radiata) which have a complementary distribution and similar feeding habits of R. erinacea and R. ocellata but which occur in deeper water.

Hybridization between Prionotus alatus and P. paralatus in the Northern Gulf of Mexico (Pisces: Triglidae)

Prionotus species with emarginate pectoral fins constitute the P. alatus species complex and consist of P. alatus, P. beanii, and P. paralatus. Specimens of this complex collected off the coast of Mobile, Alabama, were intermediate and appeared to be hybrids of P. alatus and P. paralatus. A total of 87 specimens of P. alatus and P. paralatus, plus 40 putative hybrids were examined. Greater length of the lower joined pectoral-fin rays distinguished P. alatus from its cognates. The putative hybrids had the lower joined pectoral rays at intermediate lengths and/or possessed mosaic character combinations. The hybrid zone extended from Gulfport, Mississippi, to Panama City, Florida, and may represent a vicariant zone. Similar distributional patterns are displayed by at least 13 other putative clades of benthic fishes and invertebrates, and in some cases, the zone of overlap between congeners extends southward to Campeche Bay. The putative vicariant zone appears to extend northward onto the coastal plain where it is called the Central Gulf Coast vicariant zone.

Bathyraja mariposa, a new species of skate (Rajidae : Arhynchobatinae) from the Aleutian Islands

Abstract A new species of the skate genus Bathyraja, Bathyraja mariposa, is described from the Aleutian Islands and its geographic and bathymetric range documented. Bathyraja mariposa is similar to Bathyraja violacea and Rhinoraja taranetzi in its moderate maximum size and absence of thorns on the disc. However, it can be clearly distinguished from B. violacea by its distinctive color pattern, uniform covering of fine denticles, and clasper morphology. It can be distinguished from R. taranetzi and other similar western North Pacific species by the lack of a pseudosiphon on the clasper as well as by differences in various morphometric and meristic characters.

Morphological variation within Raja miraletus and Starus of R. ocellifera (Chondrichthyes, Rajoidei)

Variation in body size, shape and clasper structure of specimens of Raja miraletus from the Mediterranean and the Gulf of Guinea led to a study of the morphological variation of this species over its entire known range: the Mediterranean, and western and southern Africa. A total of 124 specimens were examined from five areas (Mediterranean, Mauritania-Senegal, Gulf of Guineaequatorial Africa, Angola and South Africa) for the morphological study and from seven areas (Mediterranean, Mauritania, Senegal, Gulf of Guinea, equatorial Africa, Angola and South Africa) for the meristic study. Of the morphological groups, the Mediterranean and South African samples are the most distinct from each other and from the other samples. West African samples are the most similar, with Gulf of Guinea-equatorial African and Angolan samples the most distinct among the three samples. The Mediterranean sample is distinct from the remainder of the samples in distance between the dorsal-fin bases, interorbital width (IW), distance between the first gill slits, prenasal snout length (PNSL), preorbital snout length (POSL), number of predorsal tail vertebrae, number of pectoral radials and shape of some of the clasper cartilages. The South African sample is distinct from the other samples in distance between the dorsalfin bases, IW, PNSL, preoral snout length (PRSL), number of trunk vertebrae, shape of several of the clasper cartilages and number of postventral scapulocoracoid fenestrae. IW and distance between the first gill slits increase clinally whereas PNSL, PRSL and POSL decrease clinally from the Mediterranean to South Africa. Distance between the dorsal-fin bases, number of vertebrae between the dorsal fin bases and shape of accessory terminal 1, accessory terminal 2 and ventral terminal cartilages converge at the extremes of the distributional range. Because of the subtleness of the variation, clinal nature of some of the variables and the fact that the putative populations are parapatrically or allopatrically distributed, R. miraletus is considered a polymorphic species of at least three partially separated populations. Hydrographic conditions along the coast of west Africa may serve to divide these populations. Upwelling at Cape Blanco (21?N) may be responsible for isolating the Mediterranean and Mauritania-Senegal populations. Similarly, upwelling off Cape Frio (18?S) and the Benguela Current may separate the Angolan and South African populations.

New softnose skate genus Brochiraja from New Zealand (Rajidae: Arhynchobatinae) with description of four new species

Abstract Brochiraja, a new rajid genus, is defined for a group of softnose skates from the deep sea adjacent New Zealand. The group presently contains six species: Brochiraja asperula (Garrick & Paul), B. spinifera (Garrick & Paul), and four new taxa, B albilabiata sp. nov., B. aenigma sp. nov., B. leviveneta sp. nov., and B. microspinifera sp. nov. These species are closely related to members of the Indo‐Pacific genus Notoraja but three of them differ from all other softnose skates (arhynchobatins) in at least one presumed synaphomorphy—the presence of a bifurcated thorn on the mid‐distal rostral cartilage that is strongly evident in juveniles and variably reduced in adults. Placement of B. aenigma, known only from the post‐juvenile holotype, lacks these thorns so its placement in the genus is provisional. The new species differ from B. asperula, B. spinifera, and each other, in coloration, morphometrics, squamation, and vertebral and pectoral‐fin counts. The existence of multiple morphotypes of the two pre‐existing nominal taxa suggests that the New Zealand skate fauna has vicariated from populations isolated from each other on the remote continental slopes, seamounts, and plateaus of the South‐West Pacific.

Electric organs in skates: Variation and phylogenetic significance (Chondrichthyes: Rajoidei)

A total of 63 species of skates (Chondrichthyes: Rajoidei) were surveyed, along with three species of the outgroup (Chondrichtyes: Rhinobatoidei) for electric organs along the sides of the tail. All skate specimens examined possessed what appeared to be functional electric organs, and the three species of the outgroup lacked evidence of electric organs. The electric organs were tail‐positive and arranged into horizontal columns divided by transverse septa. The electrocytes varied considerably within and among supraspecific taxa (subgenera and genera), but they could be broadly classified into cup‐shape, modified cup‐shape, intermediate‐shape, and disc‐shape cells, provided that the distinction was partially based on position of the electrocytes within their connective tissue chambers. The survey, in part, corroborates a phylogenetic hypothesis of skates and in some respects further resolves the hypothesis. The supraspecific taxa Atlantoraja and Rioraja have similar derived‐type electrocytes, as do the five supraspecific taxa of Rajini, and Cruriraja and Anacanthobatis, and to a lesser extent the supraspecific taxa Arhynchobatis, Psammobatis, and Sympterygia, and the supraspecific taxa Notoraja, Pavoraja, and Pseudoraja, corroborating the hypothesis. The supraspecific taxa Amblyraja, Rajella, Leucoraja, Breviraja, and Dactylobatus were unresolved in the phylogenetic hypothesis, but the electrocyte survey suggested that Leucoraja, Breviraja, and Dactylobatus were derived with respect to Amblyraja and Rajella.