The feeding holes formed by bottom-feeding rays are not necessarily dug by a "wing-flapping" mechanism. The New Zealand eagle ray, Myliobatis tenuicaudatus , excavates hydraulically much of its vertical-sided feeding depression by the action of water jetted downwards through the mouth and/or gill clefts. We infer that other rays may use a similar mechanism, as evidenced by the deep, vertical-sided holes that they also dig. Although ray feeding holes are very numerous in present day intertidal and sub-tidal sand flats around northern New Zealand, no examples of fossil feeding excavations have been reported from the widespread Quaternary sediments of similar environments nearby.

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