释义 |
ostracoderm /ɒˈstrakədəːm /nounAn early jawless fossil fish of the Cambrian to Devonian periods, having a heavily armoured body.- Class Agnatha: several orders.
By the Middle Devonian the armoured jawless ostracoderms were in decline, and instead the jawed fish were undergoing a great evolutionary radiation in both the sea and in freshwater....- 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).
- These were jawless, armored fish informally called ostracoderms, but more correctly placed in the taxon Pteraspidomorphi.
Origin Late 19th century: from modern Latin Ostracodermi (former taxonomic name), from Greek ostrakon 'shell' + derma 'skin'. |