700
Journal of Paleontology 92(4):681–712
(range 0.33–0.86). Calyx medium to low cone shape, height to width ratio 1.7–3.3 (mean=2.5), medium to large size for genus, widest at level of arm openings, straight sided from base to level of arm openings. Outline of calyx at level of arm openings circular. All calyx plates nodose; nodes commonly large, horizontally elongate nodes, terminations sharp, rounded, or fluted (Fig. 8.3, 8.8); proximal elongate nodes may project downward (Fig. 8.9); plate sculpturing dominates appearance of calyx. Basal circlet truncate proximally, high, 6–16% of calyx
height (mean=13%), visible in side view; very shallow basal concavity formed by nodes. Basal plates three (Fig. 8.6, 8.7), equal in size, with an elongate transverse extension of basal plates forming proximal rim of calyx, nodes project horizontally or slightly proximally, but not beyond radials; basal rim always deeply indented at basal-basal sutures. Radial circlet 12–25% of calyx height (mean=18%); radial plates five, hexagonal or heptagonal, 2.2–4.1 times wider than high (mean=3.0). Regular interrays not in contact with tegmen, all plates nodose, typically a single interradial plate, may have one additional plate above; first interradial heptagonal to nonagonal, higher than wide, either smaller or larger than radials. Primanal heptagonal, approximately as wide as high,
central node prominent, but less transversely elongate than node on radials; plating P-3-1, not in contact with tegmen. Fixed brachials all nodose. First primibrachial very small,
wider than high, may not extend full width of ray so that the radial plate is in partial sutural contact with second primibra- chial, much reduced transverse elongate node; second primi- brachial axillary, large, pentagonal, central node. Only one secundibrachial, axillary. Additional fixed brachials slightly wider than high, last fixed brachial commonly tertibrachial three. Free arm facets elongate, inclined slightly upward. Tegmen low inverted cone from arm openings to base of
anal tube; plates large, spinose; anal tube long eccentric toward anterior; one thecal opening on either side of arm facet. Anal tube tall, narrow, small plates without nodes or spines. Free arms 12–15; characters of the free arms are not known. Proximal columnals circular, wide crenularium, very
narrow aureola or absent, wide trilobate or pentalobate lumen; one nudinodal separated by one internodal. Character of remainder of column not known.
Materials.—The holotype of B. spinosus is FMNH UC 6435, and the holotype of A. marineri is USNM 39895. Additional specimens from the Lake Cumberland area are USNM 639928–USNM 639932. OSU 54502–OSU54505, and CMC IP76372–CMC IP76375.
Measurements.—See Supplemental Table 5.
Remarks.—Eretmocrinus spinosus is a Miller and Gurley species that has not been considered for more than one century. Re-examination of Fort Payne Formation specimens from the Lake Cumberland region using the generic definitions of Ausich and Kammer (2010) has revised our understanding of this taxon. In many previous studies the crinoid identified as Magnuscrinus praegravis (né Eretmocrinus praegravis)isnow recognized as Eretmocrinus spinosus (né Batocrinus spinosus).
Magnuscrinus praegravis and E. spinosus are convergent in overall thecal shape with a low calyx, high tegmen, and domi- nant calyx and tegmen plate sculpturing. A key diagnostic character that separates Magnuscrinus and Eretmocrinus is the morphology of the interradial regions. In Magnuscrinus, the plating of the interradial regions is continuous with plating on the tegmen, whereas in Eretmocrinus it is not. The taxon in question lacks a connection between interradial and tegmen plating; thus it should be assigned to Eretmocrinus. Further, the horizontal, elongate, very large, downward-projecting nodes on the specimens now assigned to E. spinosus are consistent with the holotype of E. spinosus and not with that of Magnuscrinus praegravis. The only previous study that included both of these species was Wood (1909). She regarded them as distinct species, and we agree. For comparison to other Fort Payne species of Eretmocrinus,
see remarks of E. magnificus.
Eretmocrinus magnificus Lyon and Cassseday, 1859 × Eretmocrinus spinosus Miller and Gurley, 1895a
1895a Batocrinus laciniosus Miller and Gurley, p. 14, pl. 1, figs. 15, 16.
1994 Eretmocrinus magnificus Lyon and Cassseday × Eretmocrinus praegravis Miller; Ausich and Meyer, p. 362, fig. 1b, c.
2013 Eretmocrinus laciniosus Miller and Gurley; Webster and Webster, p. 1419.
Occurrence.—All specimens currently recognized as Eretmocrinus magnificus ×E. spinosus are from the Fort Payne Formation. The original specimens were described from localities along Lake Cumberland, but with the addition of Batocrinus laciniosus to Eretmocrinus magnificus ×E. spinosus, this hybrid is also recognized from what is interpreted to be the Fort Payne Formation from an unspecified site in Tennessee.
Materials.—The specimens assigned to this hybrid by Ausich and Meyer (1994) are USNM463329 and USNM463330. The holotype of Batocrinus laciniosus, also regarded as this hybrid, is FMNH UC 6433.
Remarks.—As noted above, Lake Cumberland region crinoids previously identified inAusich andMeyer (1994) asEretmocrinus praegravis Miller, 1892a are now regarded as Eretmocrinus spinosus; thus, changing the name of the hybrid specimens recognized by Ausich and Meyer (1994) to Eretmocrinus magnificus Lyon and Cassseday, 1859×E. spinosus Miller and Gurley, 1895a. Only three specimens of this unusual morphology are known and the morphology is variable; therefore, we regard these as hybrid specimens rather than a distinct species with a hybrid origin. As argued by Ausich and Meyer (1994), the three hybrid specimens occurred at localities (Gross Creek Buildup and Cave Springs Buildup) that supported both Eretmocrinus magnificus and Eretmocrinus spinosus. The hybrid specimens have an intermediate calyx shape and calyx plate sculpturing between these two parent species. Using Stepwise Discriminant Functional Analysis, Ausich and Meyer (1994) demonstrated that
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