일반명 : 해백합 캘릭스 (Crinoid Calyx)

학명 : Rhodocrinites sp.

지질시대 : Mississippian Period (354 to 325 Million Years)

지층 : Borden Formation

원산지 : Eastern Kentucky USA

바다나리류는 바다나리강에 속하는 극피동물의 총칭이다. 극피동물 중 가장 원시적인 것으로서 다섯 개의 여러 형태의 판으로 팔이 있으며 캘릭스라는 술잔처럼 생긴 몸체에서 방사상(여러갈래)으로 팔이 나 있는데 이들은 대부분 5의 배수로 만들어져 있다. 또한 자루 같은 다리가 바닥의 물체나 떠 다니는 물체에 감겨져 있어서 고정된 것처럼 보이지만 이들은 고착성과 부유성으로 매우 다양한 형태로 살아간다. 이 종은 바닥에 고정되듯 뿌리의 형태를 가지지만 이곳은 고정지지대 역할을 할 뿐 먹이를 취하는 곳은 캘릭스 상단에 있으며 입과 똥고가 비슷한 위치에 있는 재미 있는 종이다. 전 세계에 약 620종 가량이 알려져 있으며, 바다나리, 바다술 갯고사리 등이 여기에 해당한다.

Crinoids comprise three basic sections; the stem, the calyx, and the arms. The stem is composed of highly porous ossicles which are filled with muscular tissue. The calyx contains the crinoid's digestive and reproductive organs, and the mouth is located at the top of the dorsal cup, while the anus is located peripheral to it. The arms display pentamerism or pentaradial symmetry and comprise smaller ossicles than the stem and are equipped with cirri which facilitate feeding by moving the organic media down the arm and into the mouth.

The majority of living crinoids are free-swimming and have only a vestigial stalk. In those deep-sea species that still retain a stalk, it may reach up to 1 metre (3.3 ft) in length, although it is usually much smaller. The stalk grows out of the aboral surface, which forms the upper side of the animal in starfish and sea urchins, so that crinoids are effectively upside-down by comparison with most other echinoderms. The base of the stalk consists of a disc-like sucker, which, in some species, has root-like structures that further increase its grip on the underlying surface. The stalk is often lined by small cirri.

Like other echinoderms, crinoids have pentaradial symmetry. The aboral surface of the body is studded with plates of calcium carbonate, forming an endoskeleton similar to that in starfish and sea urchins. These make the calyx somewhat cup-shaped, and there are few, if any, ossicles in the oral (upper) surface. The upper surface, or tegmen, is divided into five ambulacral areas, including a deep groove from which the tube feet project, and five interambulacral areas between them. The anus, unusually for echinoderms, is found on the same surface as the mouth, at the edge of the tegmen.

The ambulacral grooves extend onto the arms, which thus have tube feet along their inner surfaces. Primitively, crinoids had only five arms, but in most living species these are divided into two, giving ten arms in total. In most living species, especially the free-swimming feather stars, the arms branch several times, producing anything up to two hundred branches in total. The arms are jointed, and lined by smaller feather-like appendages, or pinnules, which also include tube feet.