Fishionary

A blog about fish words!

By Abigail Lynch

A blog about fish words!

placoid denticles

Cartilaginous

September 25, 2020 by abby

If you’ve ever eaten a fish fillet, you’ve probably had the ‘pleasure’ of picking out fish bones from your meal.  While most fish are, indeed, bony (superclass: Osteichthyes), certain lineages of fish have cartilaginous skeletons, meaning that their skeletal structure is composed of cartilage, like a human ear or nose, rather than bone.  Elasmobranchs (sharks, skates, … [Read more…]

Posted in: C Tagged: chimaera, chondrichthyes, elasmobranchs, genetics, osteichthyes, placoid denticles, placoid scale, primitive fishes, rays, scute, sharks

Chondrichthyes

October 9, 2015 by abby

Chondrichthyes are a taxonomic class of cartilaginous fishes that encompass sharks and rays (elasmobranchs) and chimaera.  Though there are exceptions, in general, Chondrichthyes have exposed gills, no swim bladder, internal fertilization, and placoid denticles.  These characteristics differentiate them from the more evolutionarily derived branch of fishes, bony fish (Osteichthyes).

Posted in: C Tagged: chimaera, chondrichthyes, elasmobranchs, placoid denticles, placoid scale, rays, sharks

Placoid denticles

September 25, 2015 by abby

Placoid denticles are found on sharks, rays, and chimaeras.  Not really a true “scale,” like ctenoid or cycloid scales, placoid denticles are actually modified teeth.  They have an inner tissue component, which contains both blood vessels and nerves, that is covered by a layer of dentin and an outer enamel.  They form a tough protective skin … [Read more…]

Posted in: P Tagged: chimaera, chondrichthyes, ctenoid, cycloid, placoid denticles, placoid scale, rays, scales, sharks

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