Rutkowskicrinidae

Partial crown and column of Nassoviocrinus costatus, from McIntosh (2001).

Belongs within: Dendrocrinida.

The Rutkowskicrinidae are a group of crinoids with low conical cups and ridged thecal plates known from the late Silurian to the early Carboniferous (McIntosh 2001).

Characters (from McIntosh 2001): Cup low conical, width approximately equal to or slightly exceeding height, with thecal plates of medium thickness and most commonly ridged. Infrabasal, basal, and radial circlets with five plates each. Number of anal plates variable. Two anal plates present in some genera: radianal quadrangular, below and to left of C radial; anal X approximately pentagonal, slightly smaller than, and aligned with, adjacent posterior radials. Rarely only one anal plate in cup, arranged as above except radianal absent. Most advanced forms with three anal plates: radianal pentagonal, below and to left of C radial; right sac plate immediately above radianal and contacting C radial; and anal X to left of right sac plate and overlying radianal. Radial facets peneplenary, moderately declivate, U-shaped platforms slightly elevated above radial plate surface; transverse ridge invariably present, often prominent, never divided by ventral groove. Tegmen invariably dominated by prominent, relatively narrow anal sac composed of orderly staggered rows of thin, plicate plates; anal sac straight, partially recumbent at distalmost end in some genera; partial median ridge commonly developed on proximal (first two to five median sac plates) posterior side of sac, originating from either anal X or both anal X and right sac plate, never extending entire length of sac. Apparently only a single posterior oral, pierced by numerous hydropores, present on tegmen; other orals either absent or covered by peristomials and interambulacrals; two tegminal flange plates observed in one species. Arms rarely atomous, generally divided into two equal rami at primaxil, structure of main rami variable: isotomous, with branches of unequal length but equal brachial size; partially heterotomous, with armlets slightly smaller than brachials of main rami but branching at same points as in isotomous arms; most commonly fully heterotomous, with unbranched ramules given off main rami in an alternating pattern at equal intervals, generally every second brachial; or pinnulate. Column heteromorphic, pentagonal to pentastellate. Cirri unbranched, partially whorled.

Rutkowskicrinidae
    |--Schmidtocrinus Haarmann 1921 M01
    |    `--*S. winterfieldi (Schmidt 1906) (n. d.) [=Rhenocrinus winterfieldi] M01
    |--Rutkowskicrinus McIntosh 2001 M01
    |    |--*R. patriciae McIntosh 2001 M01
    |    `--R. collieri McIntosh 2001 M01
    |--Decorocrinus McIntosh 2001 M01
    |    |--*D. arkonensis (Goldring 1950) [=Botryocrinus arkonensis] M01
    |    `--D. cooperi (Goldring 1926) [=Charientocrinus cooperi] M01
    |--Iteacrinus Goldring 1923 M01
    |    |--*I. flagellum Goldring 1923 M01
    |    `--I. robustus Goldring 1923 M01
    |--Quantaxocrinus Webby 1965 M01
    |    |--*Q. ussheri Webby 1965 M01
    |    `--Q. clarkei (Williams 1882) [=Poteriocrinites clarkei; incl. P. clarkei var. alpha Williams 1882] M01
    |--Propoteriocrinus Schmidt 1934 M01
    |    |--*P. scopae Schmidt 1934 [=Poteriocrinus scopae (l. c.)] M01
    |    |--P. follmanni Schmidt 1941 [=Poteriocrinus follmanni (l. c.)] M01
    |    `--P. papillaxialis Schmidt 1941 [=Poteriocrinus papillaxialis (l. c.)] M01
    `--Nassoviocrinus Jaekel 1918 M01
         |--*N. pachydactylus (Sandberger & Sandberger 1855) [=Heterocrinus pachydactylus] M01
         |--N. chilmanae McIntosh 2001 M01
         |--N. corcorani Jell 1999 M01
         |--N. costatus (Goldring 1954) [=Botryocrinus costatus] M01
         |--N. duluki (Kesling 1969) [=Poteriocrinites duluki] M01
         |--N. longibrachiatus (Chapman 1903) [=Botryocrinus longibrachiatus] M01
         |--N. ornatus (Goldring 1954) [=Botryocrinus ornatus] M01
         |--N. rarifissus Jaekel 1918 [=Antihomocrinus rarifissus] M01
         `--N. schultzei (Haarmann 1921) [=Botryocrinus schultzei] M01

*Type species of generic name indicated

REFERENCES

[M01] McIntosh, G. C. 2001. Devonian cladid crinoids: families Glossocrinidae Goldring, 1923, and Rutkowskicrinidae new family. Journal of Paleontology 75 (4): 783–807.