Data from: An edrioasteroid from the Silurian Herefordshire Lagerstätte of England reveals the nature of the water vascular system in an extinct echinoderm

Echinoderms are unique in having a water vascular system with tube feet,
which perform a variety of functions in living forms. Here, we report the
first example of preserved tube feet in an extinct group of echinoderms.
The material, from the Silurian Herefordshire Lagerstätte, UK, is assigned
to a new genus and species of rhenopyrgid edrioasteroid, Heropyrgus
disterminus. The tube feet attach to the inner surface of compound
interradial plates and form two sets, an upper and a lower, an arrangement
never reported previously in an extant or extinct echinoderm. Cover plates
are absent and floor plates are separated creating a large permanent
entrance to the interior of the oral area. The tube feet may have captured
food particles that entered the oral area and/or enhanced respiration. The
pentameral symmetry of the oral surface transitions to eight columns in
which the plates are vertically offset resulting in a spiral appearance.
This change in symmetry may reflect flexibility in the evolutionary
development of the axial and extraxial zones in early echinoderm
evolution.

棘皮动物（Echinoderms）的独特特征在于拥有配备管足（tube feet）的水管系统，该结构在现生类群中可执行多种生理功能。本研究首次报道了已灭绝棘皮动物类群中保存完好的管足实例。本次研究的化石标本采自英国志留纪（Silurian）赫里福德郡化石库（Herefordshire Lagerstätte），被归为菱皮海座星类（rhenopyrgid edrioasteroid）的一个新属新种，命名为赫罗皮古斯·迪斯蒂尔努斯（Heropyrgus disterminus）。管足附着于复合间辐板的内表面，分为上下两组，这种排列模式在现生或已灭绝的棘皮动物中均未曾被报道过。该类群不存在覆盖板，底板相互分离，形成通往口区内部的大型永久开口。管足或可捕获进入口区的食物颗粒，同时/或辅助提升呼吸效率。口面的五辐射对称演变为八列骨板结构，骨板垂直偏移形成螺旋外观。这种对称模式的转变，或许反映了早期棘皮动物演化过程中，轴区与轴外区的发育演化具备灵活性。