706
Journal of Paleontology 92(4):681–712
Remarks.—No specimens ofM. praegravis were collected from the Fort Payne Formation of south-central Kentucky, Tennes- see, or north-central Alabama during this study. For comparison to other species of Magnuscrinus discussed here, see remarks of M. cumberlandensis.
Magnuscrinus cumberlandensis new species Figure 11.1–11.4
2014 Abatocrinus n. sp. Krivicich et al., p. 1155. Holotype.—USNM 639945.
Diagnosis.—Relatively large in size, very low vase-shaped calyx, interradial positions around arm periphery slightly indented, radial plates relatively high, calyx plates with broad, circular to elongate nodes.
Occurrence.—All specimens are from early Viséan strata along the shores of Lake Cumberland. The holotype is from the Gross Creek carbonate packstone buildup. Other localities include Cave Springs South (carbonate packstone buildup facies), Seventy-Six Falls (allochthonous sheetlike packstone facies), and Rowena wackestone buildup facies.
Description.—Calyx large, very low vase shaped, greatly expanded at level of arm openings, straight-sided from base to position where expansion begins in primibrachitaxis; plates on aboral cup with broad, circular or elongate nodes; arms grouped slightly into rays at level of arm openings (Fig. 11.1, 11.3). Basal circlet truncate proximally, high, ~20% of cup
height, very shallow basal concavity formed by nodosity of basal plates; basal-basal sutures indented; basal plates three, equal in size, transverse nodes on basal plates forming basal portion of calyx (Fig. 11.3). Radial circlet ~25% of calyx height; radial plates slightly
Etymology.—The trivial name for this species acknowledges the area of origin of this species, Lake Cumberland, in south-central Kentucky.
Materials.—Seven specimens ofMagnuscrinus cumberlandensis n. sp. have been collected from the southern Lake Cumberland area. A fairly complete sub-adult specimen (USNM 639945) is designated as the holotype, and the six paratypes are USNM 639946–639951. USNM 639946 is partially preserved adult specimen, and USNM 639948–639950 are partially preserved juveniles.
Measurements.—USNM 639945, holotype: CaH, 14.9mm; CaW, 46.8mm; proximal BW, 11.2mm; TH, 12.6* mm. USNM 639946, paratype: CaH, 23.5mm; CaW, 86.7mm; proximal BW, 10.5* mm.
Remarks.—Magnuscrinus cumberlandensis n. sp. is unique
among Fort Payne Formation batocrinids in the considerable flattening and expansion of the calyx at the level of the arm openings. The calyx diameter at the arm openings is nearly three times the diameter of the calyx at the level of the radials. In contrast, in A. steropes the diameter at the arm openings is only 1.5 times greater than that at the radials. Two basic sizes of specimens are assigned to
wider than high, five, hexagonal, ~1.5 times wider than high, supporting the first primibrachial above and an interradial laterally above on each side. In regular interrays a single large interradial plate, octagonal, a large elongate node in center, higher than wide, not in contact with tegmen, smaller than radial plates, concave in profile because situated at position of calyx where expansion to arm openings begins. Primanal heptagonal, slightly higher than wide, equal in
width to adjacent radials, higher than adjacent radials, interrupts radial circlet; large, central, slightly elongate node; three plates in second range; third range not preserved. Fixed brachials gently convex. First primibrachial wider
than high; second primibrachial axillary; second secundibra- chial axillary; three fixed tertibrachials, as known. Tegmen large, flat inverted cone from arm openings to base
of anal tube, height of anal tube not known; tegmen plates large with central circular nodes or spines (Fig. 11.2). Free arms as many as 40, but ~20 in juveniles; facets large,
vertical. Characteristics of free arms not known. Proximal column circular with a pentalobate lumen; other
details of column not known.
M. cumberlandensis n. sp. The smaller specimens have a calyx diameter of 5–6 cm, whereas the larger have a diameter that is 28% larger (as much as 8.5 cm). These specimens also differ in the height of the aboral cup (higher in larger specimens), robustness of radial plate sculpturing (more robust in larger specimens), thickness of calyx plates (thicker in larger speci- mens), and in the number of free arms (more in larger specimens). These two morphotypes either represent juvenile versus adult specimens of a single species or two different species. The basic overall geometry of M. cumberlandensis n. sp., unique among early Viséan batocrinids, is similar for these two morphotypes, and these two morphologies are regarded as ontogenetic variation. The unique morphology of this new taxon makes its
generic assignment a challenge. With the revised diagnosis of the Batocrinidae (Ausich and Kammer, 2010), the combination of a greatly expanded tegmen at the position of the arm facets, slightly grouped arms, and plating in all interrays in contactwith the tegmen ally this species with Magnuscrinus. Extensive calyx flattening and expansion at the level of arm
openings is an iterative convergent design that developed in Mississippian crinoids, including other batocrinids (e.g., Eutro- chocrinus), and actinocrinitids (e.g., Strotocrinus). In comparison to these other examples, M. cumberlandensis n. sp. has a much shorter calyx with expansion developed on more proximal plates. Magnuscrinus cumberlandensis n. sp. is relatively large in
size, with a very low vase-shaped calyx; interradial positions around arm periphery slightly indented; radial plates relatively high; and calyx plates with broad, circular to elongate nodes. Other species of Magnuscrinus have the following characters: M. yandelli, relatively large in size, very low cone-shaped calyx, interradial positions around arm periphery greatly indented, radial plates relatively low, calyx plates with pronounced elongate nodes that dominate calyx appearance; M. kammeri is
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