Class Crinoidea J.S. MILLER, 1821
Morphogenus Trombonicrinus (col.) gen. nov.
Etymology: From the French trombone (earlier, trombon), a brass wind instrument with a slide bent in a tight U-shape (Little et al. 1983, p. 2368). The overall appearance of this crinoid stem is reminiscent of the slide of a trombone.
Type species: Trombonicrinus (col.) hanshessi gen. et sp. nov. The only species known.
Diagnosis: A long crinoid stem of circular section, tapering distally throughout, with a tight curvature through 180º between the mesistele and proxistele; attached distally by short, pointed, unsegmented pseudoradices.
Remarks: A new term, pseudoradice, is used herein, in the morphogeneric diagnosis and elsewhere, in preference to the widely used pseudocirrus. Moore et al. (1978, p. T240) defined pseudocirrus as an “Unsegmented sideward projection from columnal resembling cirrus in having axial canal but very irregular in form and distribution.” But cirri sensu stricto are flexible appendages with contractile tissues capable of grasping, and are known almost exclusively from post-Palaeozoic isocrinines and comatulids (Donovan 1993). Palaeozoic and certain post-Palaeozoic crinoids, such as bourgueticrinines, have jointed, but inflexible radices (also called radicles or roots) without contractile tissues. As pseudoradices are known mainly (entirely?) from Palaeozoic crinoids and, in their inflexibility, are closer to radices in function than cirri, we consider the term pseudocirrus to be a misnomer that we correct herein.
Range: Lower(?) Devonian of Morocco.
Trombonicrinus (col.) hanshessi gen. et sp. nov.
Figures 1, 2
Etymology: In honour of the late Hans Hess.
Type material: Holotype, RGM.1350539 (Fig. 1); paratype, RGM.1350540 (Fig. 2).
Other material: A third specimen was on sale from the Middle Devonian of Alnif, Morocco [(www.bigfossil.com/undescribed-crinoid—morocco-4707-p.asp) (accessed 17 April 2018)].
Locality and horizon: Lower(?) Devonian of Tafraoute, Anti Atlas Mountains, Morocco.
Diagnosis: As for the morphogenus (see above).
Description of holotype: Total length of stem c. 270 + mm; crown not preserved, but stem may be complete. The stem is divided into the dististele (Fig. 1a, c), mesistele (Fig. 1a, b) and proxistele (Fig. 1a, b), with a transition through 180º between the mesistele and proxistele.
Dististele gently sinuous, slender, circular in section, about 50 mm long, tapering to a point. Pseudoradices common in the more proximal 35 mm of dististele. Pseudoradices pointed, conical, tooth-like, unsegmented, concentrated mainly on the side of the dististele away from the more proximal proxistele (Fig. 1a). Order of columnals not apparent, perhaps obscured by cleaning.
Mesistele longer than dististele, diameter gradually increasing more proximally. Mesistele more convoluted than either proxistele or dististele (Fig. 1a, b), albeit less so in the paratype. Latera spiny, spines shaped like short pseudoradices; latera otherwise planar. Spines are concentrated on the side away from the proxistele. Column appears homeomorphic, latera gently convex.
The mesistele–proxistele transition curves through 180º (Fig. 1a, b). The column is homeomorphic or only weakly heteromorphic, composed of numerous low columnals that are each slightly wedge shaped. Articulation symplectial. Latera gently convex, unsculptured apart from sparse low tubercles only on the outside of the curve and not extending to the proxistele.
Proxistele straight, long, expanding in diameter proximally. Latus unsculptured, planar, lacking pseudoradices and spines. Column appears heteromorphic more proximally in the holotype, perhaps N212, nodals highest et seq., but it is certainly homeomorphic in the paratype (Fig. 2b). A slight flaring of the column at the proximal-most (broken) end may indicate that this was immediately beneath the cup.
Remarks: The type specimens have been cleaned and appear polished. This has the effect of obscuring the fine details of some parts of the stem, so details of the arrangements of columnals (homeomorphic, heteromorphic) are obscure in places.