Three crinoids are known from the Upper Ordovician Hatter Limestone at Union Furnace in central Pennsylvania, i.e., Haptocrinus buttsi n. sp., an unknown crinoid with a lichenocrinid holdfast, and an indeterminate columnal that probably belongs to a crinoid. Two crowns enable H. buttsi n. sp. to be reconstructed. The animal lived about 70 cm above the seafloor and was attached to a strophomenid brachiopod with a lichenocrinid holdfast. Its endotomous arms formed an efficient filtration net that covered much of the water within its planar filtration fan. The application of filtration theory indicates that H. buttsi n. sp. could begin to feed at a comparatively low ambient current velocity and balance its energy budget. Like many other ramulate disparids, H. buttsi n. sp. mainly collected moderately small food particles. As a member of the Tornatilicrinidae, H. buttsi n. sp. is a relatively primitive disparid. Another crinoid taxon bears a longer and thinner stem and a different type of lichenocrinid holdfast cemented to the same strophomenid shell. A third species, most likely a crinoid, is represented by a single columnal. The fauna lived in a quiet water lagoonal area, which is an unusual habitat for Paleozoic crinoids.

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