Hexacrinitidae

Hexacrinites sp., from Lithos Harelbeke.
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 1983 WM03
|–Adelocrinus Phillips 1841 [incl. Perischodomus Tornquist 1898 non M’Coy 1849] LMW01
|    `–*A. hystrix Phillips 1841 J78, LMW01 [=Arthroacantha hystrix LMW01]
|–Platyhexacrinus Schmidt 1913 U78
|    `–*P. inornatus Schmidt 1913 U78
|–Prohexacrinus Yakovlev 1946 U78
|    `–*P. arcticus Yakovlev 1946 U78
|–Oehlerticrinus Le Menn 1975 U78
|    |–*O. seillouensis Le Menn 1975 U78
|    `–O. lefretensis U78
|–Arthroacantha Williams 1883 [=Arthracantha Hinde 1886; incl. Hystricrinus Hinde 1885] U78
|    |–*A. ithacensis Williams 1883 [=*Arthracantha ithacensis] U78
|    |–*Hystricrinus’ carpenteri Hinde 1885 U78
|    |–A. depressa U78
|    `–A. schwerdii U78
`–Hexacrinites Austin & Austin 1843 WM03 (see below for synonymy)
|–*H. interscapularis (Phillips 1841) (see below for synonymy) U78
|–H. carboniferous U78
|–*Triplaricrinites’ exculptus Goldfuss in Schultze 1866 (see below for synonymy) U78
|–H. limbatus WM03
|–H. occidentalis WM03
|–H. pinnulata Waters, Maples et al. 2003 WM03
`–H. verrucosus U78

Hexacrinites Austin & Austin 1843 WM03 [incl. Hexacrinus Austin & Austin 1844 U78, Triplaricrinites Goldfuss in Schultze 1866 U78, Triplaricrinus Zittel 1879 U78]

*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.

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