Belongs within: Blastoidea.
The Astrocrinidae are a Devonian to Permian group of blastoids with eight spiracular slits along the margins of the ambulacra, and no slits on the anal side (Beaver et al. 1967). The genera Astrocrinus and Tripoblastus are believed to have been free-living, sitting directly on the sea floor without an attaching stalk (Waters et al. 2003). The Devonian Cryptoschisma schultzii has completely exposed lancets producing petaloid ambulacra (Beaver et al. 1967).
<==Astrocrinidae [Astracrinidae, Pentephyllidae, Zygocrinidae]
| i. s.: Tripoblastus Waters, Maples et al. 2003WM03
| `--*T. plicatus Waters, Maples et al. 2003WM03
| Pentephyllum Haughton 1859BF67
| `--*P. adarense Haughton 1859BF67
|--Cryptoschisma Etheridge & Carpenter 1886BF67
| `--*C. schultzii (de Verneuil & d’Archiac 1845) [=Pentremites schultzii]BF67
`--+--Pentremitidea d’Orbigny 1850 [=Pentetrematites Steininger 1849, Pentremitidia Quenstedt 1876]BF67
| `--*P. pailletti (de Verneuil 1844) [=Pentremites pailletti, *Pentetrematites pailletti, *Pentremitidia pailletti]BF67
`--Astrocrinus Morris 1843 (see below for synonymy)BF67
|--*A. tetragonus Morris 1843 (see below for synonymy)BF67
|--A. bennieiBF67
`--‘Zygocrinus’ cruciatusH04
Astrocrinus Morris 1843 [=Astracrinites Austin & Austin 1843, Astrocrinites Austin & Austin 1843 non Conrad 1841, Zygocrinus Bronn 1848]BF67
*Astrocrinus tetragonus Morris 1843 [=Astrocrinites tetragonus Austin & Austin 1843 (n. n.), Astracrinites tetragonus, *Zygocrinus tetragonus]BF67
*Type species of generic name indicated
References
[BF67] Beaver, H. H., R. O. Fay, D. B. Macurda Jr, R. C. Moore & J. Wanner. 1967. Blastoids. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt S. Echinodermata 1. General characters. Homalozoa—Crinozoa (except Crinoidea) vol. 2 pp. S297–S455. The Geological Society of America, Inc., and The University of Kansas: Lawrence (Kansas).
[H04] Haeckel, E. 1899–1904. Kunstformen der Natur. Bibliographisches Institut: Leipzig und Wien.
[WM03] Waters, J. A., C. G. Maples, N. G. Lane, S. Marcus, Liao Z.-T., Liu L., Hou H.-F. & Wang J.-X. 2003. A quadrupling of Famennian pelmatozoan diversity: new Late Devonian blastoids and crinoids from northwest China. Journal of Paleontology 77 (5): 922–948.