释义 |
placoderm /ˈplakə(ʊ)dəːm /nounA fossil fish of the Devonian period, having the front part of the body encased in broad flat bony plates.- Class Placodermi: several orders.
Such giant cephalopods play or played a similar ecological role of top predator to that of Devonian arthrodire placoderms, Mesozoic pliosaurs and Cenozoic toothed whales....- During this period the agnathan and gnathostome fishes, too, gave rise to many distinctive groups: the armoured ostracoderm and placoderms, the bony fishes, and elasmobranchs to populate marine and freshwater environments.
- With their armored head shield and trunk shield composed of overlapping bony plates, the placoderms appear at first glance extremely similar to the ostracoderms (armoured jawless fish).
OriginMid 19th century: from Greek plax, plak- 'flat plate' + derma 'skin'. |