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Any of various extinct primitive jawless fishes of the Ordovician through the Devonian periods, having bodies encased in an armor of bony plates.

[Greek ostrakon, shell; see ost- in Indo-European roots + -derm.]


(ˈɒstrəkəˌdɜːm; ɒsˈtrækə-)
(Palaeontology) any extinct Palaeozoic fishlike jawless vertebrate of the group Ostracodermi, characterized by a heavily armoured body
[C19: via New Latin from Greek ostrakon shell + -derm]


(ˈɒs trə koʊˌdɜrm)

any of several extinct jawless fishes of the Ordovician to Devonian periods that had the body enclosed in an armor of bony plates.
[1890–95; < New Latin Ostracodermi, pl. of Ostracodermus < Greek ostrakódermos with a shell]
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.ostracoderm - extinct fish-like jawless vertebrate having a heavily armored bodyostracoderm - extinct fish-like jawless vertebrate having a heavily armored body; of the Paleozoic
agnathan, jawless fish, jawless vertebrate - eel-shaped vertebrate without jaws or paired appendages including the cyclostomes and some extinct forms
order Ostracodermi, Ostracodermi - extinct group of armored jawless vertebrates; taxonomy is not clear
References in periodicals archive ?
Marine organisms such as sponges and algae, along with primitive snails, clams, cephalopods and jawless fish called ostracoderms, all suffered as a consequence.
The so-called 'Atholville Beds' (Dineley and Williams 1968), exposed at Campbellton and Atholville, have been examined by paleontologists since 1881 and have yielded ostracoderms, arthrodires, acanthodians and chondrichthyans (Whiteaves 1881, 1889; Woodward 1889, 1892; Traquair 1890, 1893).