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单词 ostracoderm
释义

Definition of ostracoderm in English:

ostracoderm

noun ɒˈstrakədəːmˈästrəkōˌdərm
  • An early jawless fossil fish of the Cambrian to Devonian periods, having a heavily armoured body.

    Class Agnatha: several orders

    Example sentencesExamples
    • These were jawless, armored fish informally called ostracoderms, but more correctly placed in the taxon Pteraspidomorphi.
    • 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).
    • If lancelets and the fossil ostracoderms are considered out-groups to living craniates, then the brains of the earliest craniates must have been very small for their body size.
    • Enamel, or enameloid tissue covering tubercles, was clearly described in Ordovician vertebrates such as the ostracoderms.

Origin

Late 19th century: from modern Latin Ostracodermi (former taxonomic name), from Greek ostrakon 'shell' + derma 'skin'.

 
 

Definition of ostracoderm in US English:

ostracoderm

nounˈästrəkōˌdərm
  • An extinct jawless fish of the Cambrian to Devonian periods, having a heavily armored body.

    Class Agnatha: several orders

    Example sentencesExamples
    • 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).
    • Enamel, or enameloid tissue covering tubercles, was clearly described in Ordovician vertebrates such as the ostracoderms.
    • These were jawless, armored fish informally called ostracoderms, but more correctly placed in the taxon Pteraspidomorphi.
    • If lancelets and the fossil ostracoderms are considered out-groups to living craniates, then the brains of the earliest craniates must have been very small for their body size.

Origin

Late 19th century: from modern Latin Ostracodermi (former taxonomic name), from Greek ostrakon ‘shell’ + derma ‘skin’.

 
 
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更新时间:2024/12/23 16:17:31