elasmobranch
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vertebrateAnnotated classificationSubclass Elasmobranchii (sharks and rays) Numerous teeth derived of placoid scales; 5 to 7 gill clefts; operculum absent; cloaca; upper jaw not fused with braincase; dorsal fin nonerectile; with spiracles; worldwide distribution. Subclass Holocephali (chimeras) Teeth fused to bony plates; no scales; 4 gill
Read MoreSubclass Elasmobranchii (sharks and rays) Numerous teeth derived of placoid scales; 5 to 7 gill clefts; operculum absent; cloaca; upper jaw not fused with braincase; dorsal fin nonerectile; with spiracles; worldwide distribution. Subclass Holocephali (chimeras) Teeth fused to bony plates; no scales; 4 gill
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fishAnnotated classificationSubclass Elasmobranchii Chondrichthians with 5–7 pairs of gill clefts not covered by a fold of skin, opening separately to the exterior. Order Selachii (sharks) Elasmobranchs with gill clefts opening at least partly on the side of the body. More than 400 species. Order
Read MoreSubclass Elasmobranchii Chondrichthians with 5–7 pairs of gill clefts not covered by a fold of skin, opening separately to the exterior. Order Selachii (sharks) Elasmobranchs with gill clefts opening at least partly on the side of the body. More than 400 species. Order
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chondrichthyanAnnotated classificationClass Chondrichthyes Subclass Elasmobranchii (sharks and rays) Chondrichthyans with 5–7 pairs of gill clefts not covered by a fold of skin, opening separately to the exterior. Order Selachii (sharks) Elasmobranchs with gill clefts opening at least partly on the side of the body.
Read MoreClass Chondrichthyes Subclass Elasmobranchii (sharks and rays) Chondrichthyans with 5–7 pairs of gill clefts not covered by a fold of skin, opening separately to the exterior. Order Selachii (sharks) Elasmobranchs with gill clefts opening at least partly on the side of the body.
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animal reproductive systemGonads, associated structures, and productsIn cyclostomes (lampreys and hagfish), elasmobranchs (sharks, skates, and rays), and teleosts most of it differentiates, and the gonads extend nearly the length of the body trunk. In tetrapods (amphibians, reptiles, birds, and mammals), the cranial portion, at the anterior end, generally does not differentiate; in toads only the more…
Read MoreIn cyclostomes (lampreys and hagfish), elasmobranchs (sharks, skates, and rays), and teleosts most of it differentiates, and the gonads extend nearly the length of the body trunk. In tetrapods (amphibians, reptiles, birds, and mammals), the cranial portion, at the anterior end, generally does not differentiate; in toads only the more…
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animal reproductive systemProvisions for the developing embryoIn viviparous elasmobranchs development takes place in the uterus, the lining of which develops parallel ridges or folds covered with villi or papillae (trophonemata) that constitute a simple placenta (site of fetal–maternal contact). In contact with this region is the yolk sac of the embryo, which serves…
Read MoreIn viviparous elasmobranchs development takes place in the uterus, the lining of which develops parallel ridges or folds covered with villi or papillae (trophonemata) that constitute a simple placenta (site of fetal–maternal contact). In contact with this region is the yolk sac of the embryo, which serves…
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