The Teleost Fuse

A while back, I discussed the group of fish known as the Holostei, the gars and bowfin. The Holostei constitute one branch of the clade Neopterygii which includes the majority of living ray-finned fishes. However, their success in the modern environment pales in comparison to that of their sister group, the Teleostei. Siemensichthys macrocephalus, an… Continue reading The Teleost Fuse

Carcharhiniformes

Gulf catshark Asymbolus vincenti, copyright Seaborn. Belongs within: Selachimorpha. Contains: Hemigaleidae, Sphyrnidae, Carcharhinidae, Triakidae, Scyliorhinus, Apristurus, Galeus, Halaelurus. The Carcharhiniformes are a diverse group of sharks with dorsal fins lacking anterior spines, and the posterior gill slit(s) overlapping the base of the pectoral fins. Characters (from Compagno 1984): Trunk cylindrical to slightly compressed or depressed… Continue reading Carcharhiniformes

Carcharhinidae

Graceful shark Carcharhinus amblyrhynchoides, copyright Tassapon Krajangdara. Belongs within: Carcharhiniformes. The Carcharhinidae, requiem sharks, are a group of actively swimming sharks including many of the most commonly encountered species in tropical waters. Characters (from Compagno 1984): Head without laterally expanded blades; eyes circular, vertically oval, or horizontally oval, their lengths 1.5 times their height or… Continue reading Carcharhinidae

Sphyrnidae

Scalloped hammerhead shark Sphyrna lewini, copyright NOAA Photo Library. Belongs within: Carcharhiniformes. The Sphyrnidae, hammerhead sharks, are a group of actively swimming sharks in which the head has been expanded laterally into a mallet- or hammer-like shape. Characters (from Compagno 1984): Head with laterally expanded blades, shaped like a double-bitted axe or mallet in profile;… Continue reading Sphyrnidae

Scyliorhinus

Dogfish Scyliorhinus canicula, copyright Joe. Belongs within: Carcharhiniformes. Scyliorhinus is a genus of catsharks with the second dorsal fin much smaller than the first, and labial furrows present on the lower jaw only (Compagno 1984). Characters (from Compagno 1984): Body not tadpole-shaped, moderately stout to slender and cylindrical or spindle-shaped, tapering considerably to caudal fin;… Continue reading Scyliorhinus

Triakidae

Starry smooth-hound Mustelus asterias, copyright Hans Hillewaert. Belongs within: Carcharhiniformes. The Triakidae, houndsharks, are a group of small to medium-sharks that are most diverse in waters of the continental shelf, often at or close to the bottom of the water column (Compagno 1984). Characters (from Compagno 1984): Head without laterally expanded blades; eyes elongated and… Continue reading Triakidae

Galeus

Blackmouth catshark Galeus melastomus, photographed by Pierluigi Angioi. Belongs within: Carcharhiniformes. Galeus is a genus of catsharks with a caudal crest of enlarged denticles and large pectoral fins (Compagno 1984). Characters (from Compagno 1984): Body not tadpole-shaped, slender and subcylindrical to rather compressed, tapering slightly to considerably to caudal fin; body firm and thick-skinned, with… Continue reading Galeus

Apristurus

Brown catshark Apristurus brunneus, from the US National Oceanic and Atmospheric Administration. Belongs within: Carcharhiniformes. Apristurus is a genus of catsharks with a broad, flattened head and long snout (Compagno 1984). Characters (from Compagno 1984): Body not tadpole-shaped, stocky and more or less compressed, increasing in height up to the pectoral and trunk region and… Continue reading Apristurus

Halaelurus

Tiger catshark Halaelurus natalensis, copyright S. du Preez. Belongs within: Carcharhiniformes. Halaelurus is an Indo-Pacific genus of catsharks with a relatively short snout and caudal fin (Compagno 1984). Characters (from Compagno 1984): Body not tadpole-shaped, slender to moderately stout and cylindrical or fusiform, tapering slightly or moderately to caudal fin; body firm and thick-skinned, with… Continue reading Halaelurus

Selachimorpha

Japanese angelshark Squatina japonica, copyright Ryo Sato.Belongs within: Chondrichthyes. Contains: Carcharhiniformes, Lamniformes, Orectolobiformes, Hexanchiformes, Squalidae. The Selachimorpha are the clade including all modern sharks, distinguished from the rays by the pectoral fins remaining separate from the head. Most living sharks can be divided between the clades Galeomorphii and Squalomorphii with members of the latter clade… Continue reading Selachimorpha