Kyle R Luckenbill

A method for visualizing previously pigmented areas of the body with the employment of black-light spectrum bulbs is described. Under ultraviolet (UV) light, fish musculature fluoresces, whereas melanophores absorb incident light, revealing nearly lost contrast between once strongly and poorly pigmented areas of the body that has faded over time. Although a yet unknown extent of melanophore preservation is necessary to expose such contrast, the method was successful on a partially faded holotype of Characidium fasciadorsale Fowler, a nearly completely faded holotype of Characidium etheostoma Cope, and most remarkably for the blackened, previously mold-infested and nearly destroyed holotype of Holotaxis laetus Cope. In the latter case, the method also allowed better recognition of scale pockets on the skin.

The Widemouth Blindcat, Satan eurystomus Hubbs and Bailey 1947, was the second of four stygobitic species of Ictaluridae discovered in the subterranean waters of southern Texas and northeastern Mexico. The skeletal anatomy of Satan has been scarcely known from a few, dated radiographs. Using additional radiographs and high resolution CT-datasets for two well-ossified specimens, we applied high-resolution X-ray computed tomography (HRXCT) to visualize, illustrate and describe the bony skeleton of Satan. We also provide an online archive of still and animated tomographic images of the skeletal anatomy of this little-known species. The skeleton and soft anatomy of Satan are distinctive. Twelve skeletal autapomorphies are described that singularly distinguish Satan within Ictaluridae and, probably in combination, from all other catfishes. Some of these are reductive losses or simplifications of skull bones (e.g. loss of one infraorbital bone; reduced ornamentation of the pterotic bone) and joint complexity (e.g. simple overlapping frontal-lateral ethmoid articulation; loosely ligamentous interopercle-posterior ceratohyal joint). Some of the autapomorphies are anatomically and perhaps developmentally complex (e.g. a novel series of three midline joints closing a middle span of the posterior cranial fontanel; a deeply excavated temporal fossa and an unusually enlarged interhyal bone). The tiny dorsal-fin spinelet (first lepidotrich) of Satan has a novel peaked and twisted shape. Ten apparent and exclusive synapomorphies within Ictaluridae gathered from this and previous studies suggest that Satan and Pylodictis are closest relatives. Most of these are functionally related to prey detection and suction feeding: fusion of the symphyseal mandibular sensory pores and increase in the number of preoperculo-mandibular canal pores; depressed, flattened heads and wide transverse mouths; prominent posterior process of the lateral ethmoid alongside and below the frontal bone margin; vertical and blade-like supraoccipital posterior process; unique arrangement of the parasagittal and occipital muscle attachment crests on the skull roof; large triangular panel of integument within the operculum framed by the opercle, preopercle and interopercle bones; elongated posterior ceratohyal; and, form of the fourth supraneural and loss of its anterior nuchal plate. In contrast, 15 synapomorphies recovered by Arce-H. et al. 2016, are confirmed suggesting that Satan is one of the four stygobitic ictalurids comprising a "Troglobites" subclade within the family: (Trogloglanis, Satan, Prietella phreatophila, P. lundbergi). These features include three stygomorphic and reductive apomorphies that are exclusive within Ictaluridae: loss of fully developed eyes and pigmentation, and simplification of the fifth vertebra and its joint with the Weberian apparatus. Twelve other synapomorphies shown by the Troglobites are also apparent homoplasies of character states shared with various other ictalurids. These include reductive characters such as shortened lateral line canal, reduced infraorbitals and underdeveloped or incomplete ossifications of the pterotic, supraoccipital, hyoid arch bones and transcapular ligament. Also, the Troglobites and various other ictalurids have: an adnate adipose caudal fin, foreshortened anterior cranial fontanelle, reduced ventral wings of the frontal bone, replacement of bone by cartilage in hypohyal joints; incompletely ossified transcapular ligament, and consolidation of some hypural bones. Completing a full morphological character dataset across the Troglobites has been impeded by incomplete specimen preparations and study of P. lundbergi and to a lesser extent, P. phreatophila and Trogloglanis.

The pimelodid catfish genus Hypophthalmus has an unusually modified Weberian apparatus, reduced swim bladder, and associated bones of the occiput and pectoral girdle. Using high resolution X-ray tomography and traditional skeletal preparations of adult and juvenile specimens, we reexamined and illustrated this occipito-vertebral complex. Comparisons were made to the plesiomorphic architecture of the complex exhibited by phylogenetically deep pimelodid genera. Hypophthalmus has the swim bladder reduced to a pair of separate bilobed sacs, each doubly encapsulated by outer and inner layers of bone. The anterior vertebrae and occipital bones are shortened and contorted with apparent loss or fusion of the first centrum and development of novel joints between the basioccipital and complex vertebra. Two pairs of the Weberian ossicles are lost: claustra and intercalaria. The posttemporal-supracleithrum is reshaped and solidly united to a recurved arm of the 4th parapophysis with both extended far posteriorly to brace the outer swim bladder capsule and articulate with the cleithrum. The extrascapula is found in juveniles and apparently fuses with the adjacent pterotic. The third supraneural is present between the supraoccipital and complex vertebra. We point out conflicting results and interpretations among four previous studies and our treatment of the occipito-vertebral complex and swim bladder of Hypophthalmus. Based on unambiguous morphological and molecular evidence, Hypophthalmus belongs to the sorubimine clade of the family Pimelodidae. In this evolutionary context the morphology of the occipito-vertebral complex and swim bladder of Hypophthalmus is distinctly divergent from that of other sorubimines. The complex of Hypophthalmus is also distinct from the partially encapsulated swim bladders of the Calophysus and Megalonema clades. The morphology of the occipito-vertebral complex and swim bladder of Hypophthalmus is uniquely autapomorphic.

The anatomy and development of the siluriform pectoral-fin spine is described, illustrated and a terminology is suggested for its parts. Catfish pectoral-fin spines exhibit considerable diversity of size, shape, robustness, surface texture and, especially, details of the dentated or serrated anterior and posterior margins. This study illustrates the variety, and taxonomic and phylogenetic significance of pectoral-fin spine diversity in the South American goliath catfishes of the tribe Brachyplatystomini, family Pimelodidae, based on examination of spines of post-juvenile and adult specimens representing all eight living species of Brachyplatystoma and Platynematichthys. Unique pectoral-spine characters and character combinations serve to distinguish all eight species. Features of the pectoral-spines that change with growth are also described. Within the current phylogenetic framework of Pimelodidae, brachyplatystomines show character-state transformations and synapomorphies of the pectoral-fin spines that support hypotheses of monophyly for the subgenera Malacobagrus (B. rousseauxii, B. filamentosum, B. capapretum), and Goslinia (new usage) (B. platynemum, B. juruense), and also suggest a close relationship between B. tigrinum and subgenus Goslinia. Platynematichthys notatus and B. vaillantii retain relatively plesiomorphic features of the pectoral-fin spines.

We describe a new genus and species of bagrid catfish from the Kreung Babah Rot drainage in northwestern Sumatra. This new taxon is distinguished from confamilials by the following combination of characters: anguilliform body, reduced supraoccipital posterior process, absence of first dorsal spinelet, first proximal dorsal-fin radial inserting on 4th vertebra, first dorsal-fin lepidotrich ossified into spine, anterior edge of pectoral spine smooth, adipose fin in contact with base of last dorsal-fin ray, anal fin with 26 rays, and caudal fin with 17 principal rays.

The recent discovery and description of an unusually puzzling catfish, Kryptoglanis shajii Vincent and Thomas (2011) from ground and surface waters in Kerala State, southwestern, peninsular India, added an unresolved taxon to the order Siluriformes. Here we use high-resolution X-ray computed tomography (HRXCT) and X-radiography to illustrate, describe and compare the bony skeleton of Kryptoglanis with the objective of determining its phylogenetic position. Several characteristics of Kryptoglanis are strongly modified and structurally complex, setting this catfish apart from other siluriforms. Striking examples are its greatly shortened mesethmoid with overlapping frontals; non-tubular nasal bone; absence of the infraorbital lateralis sensory canal and canal bones but with an apparent antorbital bone; the flat and expansive orbitosphenoid; the vaulted supraoccipital-Weberian neural arch joint; the fenestrated occipital wall; the upwardly flexed occipito-vertebral joint; three pairs of elongated accessory processes off the compound Weberian vertebra; a unique exoccipital process for attachment of the transscapular ligament; hyomandibular-sphenotic ball and socket articulation; a serially notched anterior ceratohyal; and a novel posttemporo-supracleithum joint with the fourth transverse process. Some of these apparent autapomorphic features may eventually be found in some other siluriforms and judged to be informative on phylogenetic relationships. Presently, however, we have identified a few features that support the placement of Kryptoglanis in the Siluroidei (the presence of a posterior nostril barbel and position of the pterosphenoid along the anterior margin of the trigeminofacial foramen), and therein, as the sister lineage to family Siluridae (the nodular form and small size of the autopalatine).

Fossil remains of a catfish from the Late Miocene St. Marys Formation, Maryland, are described as a new, extinct species of Ictalurus (Ictaluridae). The holotype of Ictalurus countermani n. sp., is a three-dimensional partial skull, Weberian complex, pectoral girdle and fin spine. Referred paratype specimens include isolated mesethmoid, premaxilla, dorsal-fin spine and cleithrum. Ictalurus countermani n. sp., is distinguished among congeneric species by a combination of features of the sphenotic, cleithrum and pectoral-fin spine. The new species extends the known native geographic range of Ictalurus onto the mid-Atlantic slope and indicates extirpation of the genus from that region before the recent transplantation of the channel (I. punctatus) and blue (I. furcatus)catfishes. Fossils of gar (Lepisosteus) and bowfin (Amia) associated with I. countermani corroborate the likely freshwater environment at or near the site of their burial. An additional catfish fin spine collected with the foregoing is identified as an ariid sea catfish, cf. Ariopsis felis.

The osteology of Sarcoglanis simplex, a rare, miniature South American catfish, is described for the first time based on a single, 17 mm adult specimen that was both cleared and Alizarin-stained, and visualized with microfocus computed tomography (MicroCT). Previously, the internal skeletal features of this species could be predicted based only on conditions observed in its closest relatives within the subfamily Sarcoglanidinae of the Trichomycteridae. The relatively new MicroCT technique successfully revealed fine details of the skeletal morphology of this tiny fish. As predicted, Sarcoglanis shares with Stauroglanis, Stenolicmus, Malacoglanis, Microcambeva, and Ammoglanis an anterior ossification of the palatine and a large posteriorly directed dorsal process on the quadrate. Contrary to predictions, however, the mesethmoid of Sarcoglanis does not have the distal ends of the cornua distinctly wider than at their bases, and the anterior margin of the mesethmoid is not convex.