| 21. | Because they had reduced armor, the ptyctodontids were once thought to be the most primitive of the placoderms.
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| 22. | From these analysises, this idea of a gradient from least armored to most armored in placoderms was discarded.
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| 23. | Vertebrates included armored fishes, also preserved in the Llano Uplift . Contemporary placoderms were preserved in central Texas.
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| 24. | There is also a unique organ of yunnanolepid antiarch placoderms named " Chang's Apparatus " after her.
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| 25. | It was thought for a time that placoderms became extinct due to competition from the first Devonian / Carboniferous extinction events
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| 26. | This hypothesis helps to explain the placoderms'seemingly instantaneous appearance and diversity at the very beginning of the Devonian.
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| 27. | "' Aspinothoracidi "'is a clade of placoderms, restricted that family to only its type species.
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| 28. | There are three main groups of placoderms that have been found in Michigan, the antiarchs, arthrodires, and ptyctodonts.
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| 29. | "' Holonematidae "'is an family of relatively large arthrodire placoderms from the Early to Late Devonian.
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| 30. | During the Devonian, the placoderms went on to inhabit and dominate almost all known aquatic ecosystems, both freshwater and saltwater.
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