Suborbital Bones Research Articles

New genus and species of the family Aeduellidae (Actinopterygii) from the Lower Goldlauter Formation (Asselian, Lower Permian) of the Thuringian

A new aeduellid actinopterygian Amelangia ornata gen. et sp. nov. is described from the Lower Goldlauter Formation of the Thuringian Forest (Lower Permian, Germany). Distinguishing characters of the newly described taxon are a large dermosphenotic, an unusually large number of suborbital bones, a maxilla with a low maxillary plate, a distinct sculpture consisting of tubercles on the operculum and suboperculum, the presence of a single branchiostegal ray, and a pectoral fin with a scaly basal lobe. The preserved characters place the new genus close to the genera Aeduella and Bourbonnella. The newly described genus and species is similar to an isolated operculum and suboperculum recovered from the Lower Permian of the Krkonoše Piedmont Basin in the Bohemian Massif.

Osteichthyan Fishes from the uppermost Norian (Triassic) of the Fuchsberg near Seinstedt, Lower Saxony (Germany)

Fishes from the uppermost Norian Fuchsberg Quarry near Seinstedt are represented by two taxa that we interpret as a teleosteomorph (complete specimens) and actinistian (scales). Seinstedtia parva gen. et sp. nov. is described; although it was proposed as a possible semionotiform, this study reveals that Seinstedtia possesses a combination of teleosteomorph features, for instance: characteristic pholidophoriform-shaped cranial roof; fusion of skull roof bones; three dorso-posterior infraorbitals, including an enlarged infraorbital 3; one suborbital bone; movable premaxilla; and characteristic-shaped preopercle. In parallel, Seinstedtia possesses a head gently curved anteriorly, with lower jaw protruding slightly in front of upper jaw; supraorbital 1 forming most of antero-dorsal margin of circumorbital ring; one supramaxilla; three extrascapulae; cleithrum with short and broad lower arm; and enlarged clavicle. This character combination places Seinstedtia as a teleosteomorph, family incertae sedis. This fish (total length ca. 50 mm) and some pholidophorids (ca. 70 mm or less; Parapholidophorus nybelini and Pholidoctenus serianus) represent the known smallest teleosteomorphs that inhabited Europe during the Norian. The isolated scales are elasmoid of amioid type ornamented with the elongated ridges of actinistians. This diversity of teleosteomorphs and actinistians in Fuchsberg Quarry during the Triassic indicates a connection to a marine environment.

Feeding in the Devonian antiarch placoderm fishes: a study based upon morphofunctional analysis of jaws

AbstractAntiarch placoderm fishes were an abundant component of the Middle Paleozoic vertebrate assemblages. Despite a large number of known taxa and specimens, the morphology and function of the skeletal elements of their jaws is inadequately known. Because of this, questions regarding their feeding modes and their roles in the trophic webs remain open. We present a skeletomuscular model of the antiarch jaw apparatus with an attempt to reconstruct its potential biomechanical function. The position of the upper jaw suborbital bones within the plane of the ventral side of the fish armor is suggested to represent the natural “mouth closed” position. During mouth opening, the suborbitals rotated rostrally with simultaneous depression and inward rotation of the infragnathals. The ball-and-socket jaw articulation might ensure this combined movement. Recently described lower jaw elements ofLivnolepis zadonica(Obrucheva, 1983) andBothriolepissp. from the Upper Devonian (lower Famennian) of Central Russia demonstrating very deep and porous blades of the oral division of the infragnathals queried the structure of these bones in other antiarchs. Observed porosity reflects intense vascularization to supply blood to a connective tissue underlying a supposed keratinous sheath, which protected and strengthened the jaws, as well as made possible scraping tough food objects, such as thallus algae, from the substrate.Having evolved during the Silurian in the Pan-Cathaysian zoogeographical province, antiarchs migrated to Gondwana during the Emsian and later to Euramerica during the Eifelian. Supposedly, antiarchs became the first macrophytophagous vertebrates occupying the trophic level of primary consumers during the late Silurian–Early Devonian. This event diversified the only previously existing predator–prey interrelationships between filter-feeding agnathans and predatory gnathostomes.

Habitat influences skeletal morphology and density in the snailfishes (family Liparidae)

We tested the hypothesis that deep-sea fishes have poorly mineralized bone relative to shallower-dwelling species using data from a single family that spans a large depth range. The family Liparidae (snailfishes, Cottiformes) has representatives across the entire habitable depth range for bony fishes (0 m–> 8000 m), making them an ideal model for studying depth-related trends in a confined phylogeny. We used micro-computed tomography (micro-CT) scanning to test three aspects of skeletal reduction in snailfishes (50 species) across a full range of habitat depths: 1) reduction of structural dimensions, 2) loss of skeletal elements, and 3) reduction in bone density. Using depth data from the literature, we found that with increasing depth, the length of the dentary, neurocranium, and suborbital bones decreases. The ventral suction disk decreases width with increasing maximum habitat depth and is lost entirely in some deeper-living taxa, though not all. Although visual declines in bone density in deeper-living taxa were evident across full skeletons, individual densities of the lower jaw, vertebra, suction disk, hypural plate, and otoliths did not significantly decline with any depth metric. However, pelagic and polar taxa tended to show lower density bones compared to other species in the family. We propose that skeletal reductions allow snailfishes to maintain neutral buoyancy at great depths in the water column, while supporting efficient feeding and locomotion strategies. These findings suggest that changes in skeletal structure are non-linear and are driven not only by hydrostatic pressure, but by other environmental factors and by evolutionary ancestry, calling the existing paradigm into question.

Zandtfuro and Schernfeldfuro, new genera of Halecomorphi (Actinopterygii) from the Upper Jurassic Solnhofen Archipelago

ABSTRACTIn the Late Jurassic Plattenkalk deposits of the Solnhofen Archipelago and of Nusplingen (both southern Germany), there are a considerable number of as yet undescribed genera and species of ganoin-scaled Halecomorphi. Some species were preliminarily assigned to the genus ‘Furo’; however, as noted by previous authors, the taxon ‘Furo’ is not a monophyletic genus. A description of two new genera and species, Zandtfuro tischlingeri and Schernfeldfuro uweelleri is presented here, with further descriptions of new species to follow separately. These new taxa are characterized by a specific combination of features, including: body shape; number of suborbital bones, infraorbitals, extrascapulars, dorsal and caudal fin rays, and vertical scale rows; number and shape of maxillary teeth; presence or absence of sclerotic ring ossification; shape of the ventral postinfraorbital; insertion of dorsal, pelvic, and anal fins; position of lateral line in caudal fin area; and shape and distribution of scales. The more basal Halecomorphi with massive ganoin scales (Parasemionotiformes, Panxianichthyformes, and Ophiopsiformes) remain poorly known, compared with the more advanced halecomorph group of the Amiiformes (especially the Amiidae). Closer investigation of their taxonomic relationship is therefore important for understanding broader patterns of halecomorph evolution.

A new lower actinopterygian fish from the Upper Mississippian Bluefield Formation of West Virginia, USA.

The Upper Mississippian Bluefield Formation of the Mauch Chunk Group in southeastern West Virginia is known for its preservation of a variety of invertebrate taxa and early tetrapod trackways, but no lower actinopterygian remains have been formally described from these Carboniferous rocks. Here, the first lower actinopterygian fish is described from the Bluefield Formation of West Virginia. This fish is represented by a nearly complete articulated specimen with a three-dimensional snout and an unobstructed view of the gular and branchiostegal region. This new taxon is defined by a unique set of characters, which include features of the snout, circumorbital series, cheek, and operculo-gular region. These features make this fish different and distinct from previously described Carboniferous fishes. Some of the morphological features of note include the presence of a distinct lacrimal, premaxillary, ventral rostral and dorsal rostral bones, a narrow infraorbital ventral to the orbit, and a large crescent shaped infraorbital that contacts a single dermosphenotic. There is an anteriorly inclined hatchet-shaped preoperculum and six small suborbital bones anterior to the expanded region of this bone that filling the space between the preoperculum, dermosphenotic, and infraorbital. Posterior to the preoperculum, there is a single wedge-shaped dermohyal and a series of three rectangular anteopercular bones. The anteopercular bones extend halfway down the anterior border of the rectangular operculum. A median gular, two pairs of lateral gulars, and at least eight branchiostegal rays are present. The heterocercal caudal fin is deeply cleft and inequilobate. The scales have pectinated posterior margins and bear diagonal ridges of ganoine. The description of this new taxon represents the first actinopterygian and the first vertebrate body fossil described from the Bluefield Formation and the second actinopterygian taxon described from the Mauch Chunk Group in West Virginia.

Canal neuromast position prefigures developmental patterning of the suborbital bone series in Astyanax cave- and surface-dwelling fish

Developmental patterning is a complex biological phenomenon, involving integrated cellular and molecular signaling across diverse tissues. In Astyanax cavefish, the lateral line sensory system is dramatically expanded in a region of the cranium marked by significant bone abnormalities. This system provides the opportunity to understand how facial bone patterning can become altered through sensory system changes. Here we investigate a classic postulation that mechanosensory receptor neuromasts seed intramembranous facial bones in aquatic vertebrates. Using an in vivo staining procedure across individual life history, we observed infraorbital canal neuromasts serving as sites of ossification for suborbital bones. The manner in which cavefish departed from the stereotypical and symmetrical canal neuromast patterns of closely-related surface-dwelling fish were associated with specific changes to the suborbital bone complex. For instance, bony fusion, rarely observed in surface fish, was associated with shorter distances between canal neuromasts in cavefish, suggesting that closer canal neuromasts result in bony fusions. Additionally, cavefish lacking the sixth suborbital bone (SO6) uniformly lacked the associated (sixth) canal neuromast. This study suggests that patterning of canal neuromasts may impact spatial position of suborbital bones across development. The absence of an eye and subsequent orbital collapse in cavefish appears to influence positional information normally inherent to the infraorbital canal. These alterations result in coordinated changes to adult neuromast and bone structures. This work highlights complex interactions between visual, sensory and bony tissues during development that explain certain abnormal craniofacial features in cavefish.

Increasing the fish diversity of the Triassic faunas of Gondwana: a new redfieldiiform (Actinopterygii) from the Middle Triassic of Argentina and its palaeobiogeographical implications

AbstractA new actinopterygian, Calaichthys tehul gen. et sp. nov. is described on the basis of a few, well‐preserved specimens from the Anisian Cerro de Las Cabras Formation, Cuyo Basin in Mendoza Province. The new genus shows a combination of primitive characters (e.g. deep posterior region of the maxilla contacting the preopercle, a suspensorium backwardly oriented) and more advanced characters (e.g. distally segmented fin rays, hemiheterocercal caudal fin) and is thus considered to be a ‘subholostean’ fish. The new taxon is assigned to Redfieldiiformes on the basis of its single branchiostegal plate‐like ray, a median gular plate, pectoral fins with stout, stiff, mainly non‐segmented and distally branched fin rays, long and robust fringing fulcra in all fins, basal fulcra bordering both lobes of the caudal fin, and opposite dorsal and anal fins. Calaichthys is characterized by a combination of characters some of which are unique among redfieldiiforms (i.e. strongly ornamented but thin scales with a serrated posterior margin, smooth skull roof bones, extrascapulars with a bifid posterior margin, three suborbital bones, a hatchet‐shaped preopercle, rectangular and slender opercle, deep mouth gape, entopterygoid and ectopterygoid with small pointed teeth disposed in several series, unornamented rostral bone, massive pectoral fins and delicate dorsal, pelvic and anal fins). Calaichthys provides novel information about the anatomy of redfieldiiforms, in particular in relation with the fins and associated scaly elements, as well as the scale morphology and their disposition over the body. Our work confirms for the first time that redfieldiiforms occur in South America. Redfieldiiforms seem to have originated in Gondwana and shown two diversity peaks: in the Anisian and the Carnian. Calaichthys is coeval with those redfieldiiforms of the Middle Triassic (Anisian) of Africa and Australia dwelling in ephemeral lakes.

Early Osteological Development of Larvae and Juveniles in Red Spotted Grouper, Epinephelus akaara (Pisces: Serranidae).

We observed the osteological development of larval and juvenile red spotted grouper (Epinephelus akaara) in order to generate data for the assessment of skeletal deformities and to inform phylogenetic systematics research. Larvae and juveniles were obtained from a aquafarm in Muan-gun, Jeolla-namdo Province, Korea. The average water temperature at the time of breeding was 23.0°C and average water salinity was 33.0 psu. Freshly hatched fish larvae had not undergone any ossification, but ossification of the parasphenoid bone, which forms the base of the cranium, occurred as the juveniles reached an average body length (BL) of 2.49 mm. At the same time, ossification of the preopercle and opercle occurred in the operculum, and ossification of the maxilla, which forms the upper jaw, and the dentary bones, which form the lower jaw, began. In addition, ossification of the vertebra occurred by formation of 7 vertebral centra and the neural spine in the abdominal vertebra. When the juveniles reached an average (BL) of 5.22 mm, ossification of the nasal, lateral ethmoid, and alisphenoid bones occurred in the cranium; ossification of the endopterygoid and metapterygoid bones began in the palatine region; and ossification of the hypohyal and interhyal bones occurred in the hyoid arch. At an average (BL) of 20.9 mm, ossification of the basisphenoid bone in the cranium and the suborbital bone in the orbital region occurred. Ossification of the vertebra then occurred by the formation of long pairs of ribs from the third to the ninth abdominal vertebrae, completing osteological development.

Revision of the genus Melamphaes (Melamphaidae): 1. Oligo-Raker species M. laeviceps, M. spinifer, and M. eulepis

The redescription of three oligo-raker species of Melamphaes genus (≤19 rakers on the gill arch)—M. laeviceps, M. spinifer, and M. eulepis—is presented. These species are characterized by eye diameter that is similar or exceeds the width of the suborbital bone. M. laeviceps and M. spinifer inhabit the tropical and subtropical areas of the eastern Pacific Ocean, and M. eulepis inhabits the tropical, mostly equatorial waters of the Atlantic, Indian, and western Pacific oceans.

Complex Craniofacial Changes in Blind Cave-Dwelling Fish Are Mediated by Genetically Symmetric and Asymmetric Loci

The genetic regulators of regressive craniofacial morphologies are poorly understood. To shed light on this problem, we examined the freshwater fish Astyanax mexicanus, a species with surface-dwelling and multiple independent eyeless cave-dwelling forms. Changes affecting the skull in cavefish include morphological alterations to the intramembranous circumorbital bones encircling the eye. Many of these modifications, however, have evolved separately from eye loss, such as fragmentation of the third suborbital bone. To understand the genetic architecture of these eye-independent craniofacial alterations, we developed and scored 33 phenotypes in the context of an F2 hybrid mapping pedigree bred from Pachón cavefish and surface fish. We discovered several individuals exhibiting dramatic left-right differences in bone formation, such as extensive fragmentation on the right side only. This observation, along with well-known eye size asymmetry in natural cave-dwelling animals, led us to further evaluate left-right genetic differences for the craniofacial complex. We discovered three phenotypes, inclusive of bone fragmentation and fusion, which demonstrated a directional heritable basis only on one side. Interestingly, the overall areas of affected bones were genetically symmetric. Phenotypic effect plots of these novel craniofacial QTL revealed that cave alleles are associated with abnormal conditions such as bony fusion and fragmentation. Moreover, many linked loci overlapped with other cave-associated traits, suggesting regressive craniofacial changes may evolve through linkage or as antagonistic pleiotropic consequences of cave-associated adaptations. These novel findings illuminate significant craniofacial changes accompanying evolution in complete darkness and reveal complex changes to the skull differentially influenced by genetic changes affecting the left and right sides.

WallagoBleeker, 1851 andWallagoniaMyers, 1938 (Ostariophysi, Siluridae), Distinct Genera of Tropical Asian Catfishes, with Description of †Wallago maemohensisfrom the Miocene of Thailand

Abstract The Southeast Asian silurid catfish genus Wallagonia Myers, 1938, although regarded as a junior synonym of Wallago Bleeker, 1851 by recent authors following Myers (1948), differs fundamentally from it in many external and osteological characters. The genera evidently have been distinct since at least the middle Miocene and apparently are not closely related to each other. Wallagonia seems most similar to the silurid genus Ompok. Wallago differs most strikingly from all other silurids in having a much longer gape, extending ventroposteriorly well beyond the eyes. The extremely elongate upper jaw has a unique bony composition and suspension. It consists of three bones: the toothed premaxillary bone anteriorly, and the toothless suborbital and first postorbital bones posteriorly. The premaxillary bone is partially suspended from the cranium by the infraorbital bone. The closest relatives of Wallago have not been identified. Wallagonia and Wallago have no previously reported fossil records. Fossils o...

Genetic analysis of dermal bone fragmentation in a natural model system.

Natural model systems that reside in extreme environments can provide powerful insights into fundamental biological processes. For instance, many of the genetic and cellular regulators of normal dermal bone formation have been clarified. However, the precise genetic and molecular bases for altered bone phenotypes evolving under environmental pressure remain largely uncharacterized. In this study, we evaluated a dermal bone fragmentation phenotype that occurs in the blind Mexican cavefish (Astyanax mexicanus). We investigated this phenotype using exhaustive cranial bone measurements in the context of an F2 pedigree of surface fish × cavefish hybrids. We determined that fragmentation of the suborbital bones occurs in a largely asymmetric fashion. Further, we clarified the genetic architecture for left‐sided and right‐sided suborbital bone fragmentation from our hybrid pedigree. Our results indicated that while the area of the face occupied by suborbital bones is constrained between different‐sized individuals, the pattern and severity of fragmentation could not easily be predicted by co‐occurrence of other degenerative characteristics. Our results may indicate a pleiotropic interaction between genes selected in the cave environment for constructive traits that interfere with normal patterns of bone ossification. Research supported by NIDCR (NIH) R03DE022403.Grant Funding Source: grossja@ucmail.uc.edu

Early lens ablation causes dramatic long-term effects on the shape of bones in the craniofacial skeleton of Astyanax mexicanus.

The Mexican tetra, Astyanax mexicanus, exists as two morphs of a single species, a sighted surface morph and a blind cavefish. In addition to eye regression, cavefish have an increased number of taste buds, maxillary teeth and have an altered craniofacial skeleton compared to the sighted morph. We investigated the effect the lens has on the development of the surrounding skeleton, by ablating the lens at different time points during ontogeny. This unique long-term study sheds light on how early embryonic manipulations on the eye can affect the shape of the adult skull more than a year later, and the developmental window during which time these effects occur. The effects of lens ablation were analyzed by whole-mount bone staining, immunohistochemisty and landmark based morphometric analyzes. Our results indicate that lens ablation has the greatest impact on the skeleton when it is ablated at one day post fertilisation (dpf) compared to at four dpf. Morphometric analyzes indicate that there is a statistically significant difference in the shape of the supraorbital bone and suborbital bones four through six. These bones expand into the eye orbit exhibiting plasticity in their shape. Interestingly, the number of caudal teeth on the lower jaw is also affected by lens ablation. In contrast, the shape of the calvariae, the length of the mandible, and the number of mandibular taste buds are unaltered by lens removal. We demonstrate the plasticity of some craniofacial elements and the stability of others in the skull. Furthermore, this study highlights interactions present between sensory systems during early development and sheds light on the cavefish phenotype.

Macrosemimimus, gen. nov. (Actinopterygii, Semionotiformes), from the Late Jurassic of Germany, England, and France

ABSTRACT We describe a new semionotiform genus, which was recognized while studying Macrosemimimus fegerti, gen. et sp. nov., from the Late Jurassic Solnhofen Archipelago, Germany. Macrosemimimus (Lepidotes) lennieri from the early Kimmeridgian of Cap de la Hève, France, including Lepidotes toombsi from the Lower Kimmeridge Clay in Cambridgeshire, England, as a junior synonym, also belong to the new genus. Though different species, the presence of the same fish genus in different biodiversity zones suggests that semionotiforms might have been less sensible to the ecological and physical factors that caused the endemisms recognized in the invertebrate faunas. Macrosemimimus is mainly distinguished by the peculiar shape of the antorbital portion of the frontal bones, a single pair of extrascapular bones that do not reach the dorsal midline, anteriorly open circumborbital ring, only two suborbital bones, edentulous maxilla, a large quadratojugal involved in the jaw articulation, four postcleithra, and the pectoral fins placed very low and joining ventrally. The two included species differ in the ornamentation of the skull bones, the morphology of the scales, the relative size and position of the extrascapular bones, the dorsal extension of the preoperculum, and the kind of dentition. Although the phylogenetic relationships of Macrosemimimus are not yet established, the particular shape of the antorbital portion of the frontals and the patterns of the extrascapular and suborbital bones indicate possible systematic affinity with the macrosemiids, “Lepidotes” gloriae from the Oxfordian of Cuba, and “Lepidotes” microrhis and “Lepidotes” tanyrhis from the Barremian of Las Hoyas, Spain.

New species of Sangiorgioichthys Tintori and Lombardo, 2007 (Neopterygii, Semionotiformes) from the Anisian of Luoping (Yunnan Province, South China)

We report on a new species of the neopterygian genus Sangiorgioichthys Tintori and Lombardo, 2007, from middle Anisian (Pelsonian) deposits in South China (Luoping County, Yunnan Province). Sangiorgioichthys was previously known from a single species, S. aldae, from the late Ladinian of the Monte San Giorgio (Italy and Switzerland). The recognition of the new species helped to improve the diagnosis of the genus, which is mainly characterized by the presence of broad posttemporal and supracleithral bones, one or two suborbital bones occupying a triangular area ventral to the infraorbital bones and lateral to the quadrate, and elongate supramaxilla fitting in a an excavation of the dorsal border of the maxilla. Sangiorgioichthys sui n. sp. differs from the type species in having two pairs of extrascapular bones, the medial pair usually fused to the parietals, maxilla with a complete row of small conical teeth, long supramaxilla, more than half of the length of the maxilla, only two large suborbital bones posterior to the orbit, and flank scales with finely serrated posterior borders. With the discovery of S. sui n. sp., the number of fish genera shared by the Anisian/Ladinian deposits in the Alps and the Anisian deposits in South China increases, including not only the cosmopolitan Birgeria and Saurichthys, but also, among others, the subholosteans Colobodus (so far only in Panxian), Luopingichthys (so far only in Luoping), Peltopleurus, Habroichthys, and the very specialized neopterygians Placopleurus and Marcopoloichthys (only in Luoping). Therefore, although several fish taxa remain to be studied in the Chinese faunas, the so far available evidence indicates close biogeographic relationship between the Middle Triassic marine faunas of the Western Tethys region.

A new halecomorph fish from the Middle Triassic of Switzerland and its Systematic implications

ABSTRACT The described actinopterygian—from the Middle Triassic of Canton Graubünden, Switzerland—is a small fish with bones and scales covered with a thick layer of ganoine and with a cranium characterized by large nasal bones sutured medially, an orbital region with an uncommon, large postero-dorsal infraorbital 4+5, possibly one small accessory suborbital bone, and an enlarged preopercle with an expanded antero-ventral region that almost contacts the lateral margin of the skull roof throughout the dorsal limb. The new fish shares with halecomorphs the presence of a supra-maxillary bone, and a new halecomorph synapomorphy—the presence of a well-developed dorsal supramaxillary process of the maxilla bearing a posterior notch or articulatory surface for contact with the supramaxilla. The interopercle is small and far away from the posterior part of the lower jaw unlike the condition in halecomorphs and teleosts. †Prosantichthys buergini new genus and new species is proposed as a Halecomorphi incertae sedis, probably close to parasemionotids, but not yet assignable to any of the known halecomorph subgroups.

A NEW EARLY SEMIONOTIDAE (SEMIONOTIFORMES, ACTINOPTERYGII) FROM THE UPPER LADINIAN OF MONTE SAN GIORGIO AREA SOUTHERN SWITZERLAND AND NORTHERN ITALY)

The early history of the Semionotiformes is still scarcely known as, apart from the Permian Acentrophorus , most of the Early and Middle Triassic taxa traditionally ascribed to this order are often poorly known and/or they actually belong to other groups. Sangiorgioichthys aldae gen. n. sp. n. is described from the Upper Ladinian Kalkschieferzone (Upper Meride Limestone) of the Monte San Giorgio area on specimens coming from both Italy and Switzerland. The new genus is ascribed to the family Semionotidae as it shows several of the characters usually considered as diagnostic of the family itself, even if no real synapomorphies have been so far proposed for it. As a Semionotidae, Sangiorgioichthys gen. n. has an almost complete circumorbital series, large ascending process of the premaxilla, rostral and nasals almost tube-like, short maxilla, several suborbital bones posterior and ventral to the infraorbitals, long antero-dorsal process of the suboperculum, sensory canal system very rich in pores, mid dorsal ridge scales with an incipient spine. Peculiar characters of the new genus are dermal skull bones completely covered by ganoine, a very large ventral infraorbital almost attaining the anterior edge of the preoperculum, two ‘ventral’ suborbitals, very elongate anterior supraorbital bone, dentition made of a number of tiny pencil-like teeth, anterior and posterior lateral line scales differentiated.

Magadania skopetsi , a new genus and species of Zoarcidae (Teleostei: Perciformes) from the Sea of Okhotsk

A new genus and species of zoarcid fish, Magadania skopetsi, is described on the basis of 17 specimens (83.4–115.9 mm SL) from the intertidal zone of the northern coast of the Sea of Okhotsk, near Magadan, Russia. This species differs from other known zoarcid genera and species by having the following combination of characters: suborbital bones 5, the suborbital canal with 6–8 small pores; first epibranchial fan-shaped; palatopterygoid series reduced; supraoccipital broadly contacting exoccipital; posttemporal ventral ramus weak; upper lip continuous at symphysis; palatine teeth, pelvic fins and scales present; lateral line configuration mediolateral, incomplete, absent on posterior half of body; vertebrae 18–22 + 78–83 = 97–104. The closest genus cannot be determined cladistically except that the species is a member of the subfamily Gymnelinae. During the spawning season, M. skopetsi lives under stones near the outer marginal area of the intertidal zone.

Pyrolycus manusanus, a new genus and species of deep-sea eelpout from a hydrothermal vent field in the Manus Basin, Papua New Guinea (Zoarcidae, Lycodinae)

A new genus and species of deep-sea zoarcid fish, Pyrolycus manusanus, is described on the basis of eight specimens collected from a hydrothermal vent field in the Manus Basin, Papua New Guinea, at depths of 1623–1971 m. This genus is distinguished from other scaleless eelpout genera in the subfamily Lycodinae by the following combination of characters: six suborbital bones; six to seven suborbital pores; flesh gelatinous; gill slit large, extending ventrally beyond pectoral fin base; three postorbital pores; single occipital pore; two to three pelvic fin rays; palatopterygoid series weak; vomer and palatine teeth present; pseudobranch, scales, lateral line absent; pyloric caeca present; 16–17 pectoral fin rays; 22–23 + 56–59 = 78–81 vertebrae.