Belongs within: Compsocrinina.
The Hexacrinitidae are a group of crinoids known from the Upper Silurian to the Upper Devonian with a further possible record in the Middle Carboniferous (Ubaghs 1978).
Characters (from Ubaghs 1978): Calyx medium conical to bowl-shaped, with low to moderately high tegmen; basals three, subequal; primibrachs typically not incorporated in calyx but commonly joined with interprimibrach tegminal plates; primanal generally of approximately same size as radials. Tegmen stout, composed of small to medium-sized plates, orals and ambulacrals commonly distinct; anus opening directly through tegmen or at end of short tube. Arms two in each ray, branching. Column circular in cross section.
<==Hexacrinitidae [Hexacrinidae]
|--Ivanovaecrinus Arendt 1983WM03
|--Adelocrinus Phillips 1841 [incl. Perischodomus Tornquist 1898 non M’Coy 1849]LMW01
| `--*A. hystrix Phillips 1841J78, LMW01 [=Arthroacantha hystrixLMW01]
|--Platyhexacrinus Schmidt 1913U78
| `--*P. inornatus Schmidt 1913U78
|--Prohexacrinus Yakovlev 1946U78
| `--*P. arcticus Yakovlev 1946U78
|--Oehlerticrinus Le Menn 1975U78
| |--*O. seillouensis Le Menn 1975U78
| `--O. lefretensisU78
|--Arthroacantha Williams 1883 [=Arthracantha Hinde 1886; incl. Hystricrinus Hinde 1885]U78
| |--*A. ithacensis Williams 1883 [=*Arthracantha ithacensis]U78
| |--‘*Hystricrinus’ carpenteri Hinde 1885U78
| |--A. depressaU78
| `--A. schwerdiiU78
`--Hexacrinites Austin & Austin 1843WM03 (see below for synonymy)
|--*H. interscapularis (Phillips 1841) (see below for synonymy)U78
|--H. carboniferousU78
|--‘*Triplaricrinites’ exculptus Goldfuss in Schultze 1866 (see below for synonymy)U78
|--H. limbatusWM03
|--H. occidentalisWM03
|--H. pinnulata Waters, Maples et al. 2003WM03
`--H. verrucosusU78
Hexacrinites Austin & Austin 1843WM03 [incl. Hexacrinus Austin & Austin 1844U78, Triplaricrinites Goldfuss in Schultze 1866U78, Triplaricrinus Zittel 1879U78]
*Hexacrinites interscapularis (Phillips 1841) [=Platycrinus interscapularis; incl. *Hexacrinus melo Austin & Austin 1844]U78
‘*Triplaricrinites’ exculptus Goldfuss in Schultze 1866 [=*Triplaricrinus exculptus; incl. Hexacrinus pateraeformis Schultze 1866]U78
*Type species of generic name indicated
References
[J78] Jeffords, R. M. 1978. Dissociated crinoid skeletal elements. In: Moore, R. C., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt T. Echinodermata 2. Crinoidea vol. 3 pp. T928–T937. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).
[LMW01] Lane, N. G., C. G. Maples & J. A. Waters. 2001. Revision of Late Devonian (Famennian) and some Early Carboniferous (Tournaisian) crinoids and blastoids from the type Devonian area of north Devon. Palaeontology 44 (6): 1043–1080.
[U78] Ubaghs, G. 1978. Camerata. In: Moore, R. C., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt T. Echinodermata 2. Crinoidea vol. 2 pp. T408–T519. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).
[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.