EPERISOCRINUS NEW GENUS (CRINOIDEA, INADUNATA): TYPE SPECIES DELOCRINUS MISSOURIENSIS MILLER AND GURLEY, 18901 J. J. BURKE, Cleveland Museum of Natural History, Cleveland, OH 44106 Abstract. Reexamination of the holotype specimen of Delocrinus missouriensis showed that it is referable to the Erisocrinidae, rather than to the Catacrinidae, the family to which Delocrinus is presently assigned. A new genus, Eperisocrinus, with Delocrinus missouriensis the type species, is proposed, based on the following characters: Dorsal cup with radial plates having articular facets and obtuse proximal angles, essentially as in Erisocrinus but differing in having a considerably higher basal impression; in- frabasal plates much more reduced and steeper walled adjacent to the stem; larger basal plates; interbasal and interradial sutures nearly equal in length; and anal X represented on outer wall of cup. OHIO J. SCI. 77(4): 174, 1977 In 1890, when Miller and Gurley pro- by acronyms that identify the institution posed the genus Delocrinus, and desig- in which they are reposited. These nated Poteriocrinus hemisphericus Shu- acronyms and the institutions to which mard as the type species, they described they apply are as follows: UC, Field and attributed to the genus a second Museum of Natural History; UI, Uni- species, Delocrinus missouriensis. Re- versity of Illinois, and UT, University of cent study of the holotype of Delocrinus Texas. missouriensis demonstrates that it is an erisocrinid and only distantly related to SYSTEMATIC PALEONTOLOGY the Catacrinidae, the family to which Class: CRINOIDEA Miller, 1821 Delocrinus is presently assigned. Subclass: INADUNATA Wachsmuth and Two specimens were referred to D. missouriensis at the time of its initial Springer, 1897 description. One of these, a dorsal cup, Order: CLADIDA Moore and Laudon, 1943 UC 6233A, was declared the holotype Suborder: POTERIOCRININA Jaekel, 1918 (lectotype) of the species by Moore and Family: ERISOCRINIDAE Wachsmuth Hummer (1940) and is the subject of and Springer, 1886 this discussion. The second, UC 6233B, Genus: EPERISOCRINUS, n.g. part of a crown preserving long primi- DIAGNOSIS. Dorsal cup with radial brach spines and a portion of the stem, plates having articular facets and obtuse had the anal plates buried in matrix at proximal angles essentially as in Eriso- the time of the original description. crinus, but differing in having (1) a con- Since then the dorsal cup and arms have siderably higher basal impression; (2) in- been skillfully extricated from the ma- trix (possibly by Moore himself). The frabasal plates much more reduced, and cup bears three anal plates; this crown steeper walled adjacent to the stem; (3) quite evidently represents a species of larger basal plates; (4) interbasal and Plaxocrinus but treatment of it is beyond interradial sutures nearly equal in length, the scope of the present article. and (5) anal X represented on outer wall of the cup. Specimens cited in this discussion are distinguished by numbers, or numbers ETYMOLOGY. From the Greek epi = combined with letters, which are preceded heside-\- Erisocrinus, the genus. Manuscript received October 19, 1976 (#76- TYPE SPECIES. Delocrinus missourien- 81). sis Miller and Gurley, 1890. 174 Ohio J. Sci. EPERISOCRINUS, NEW GENUS 175 LOCALITY AND HORIZON. Kansas City, posits, the sutures of the holotype dorsal Missouri, Upper Coal Measures (Mis- cup, UC 6233A, are difficult to discern. sourian). I have resorted to tracing them in pencil to indicate them in the photographs from EPERISOCRINUS MISSOURIENSIS which my illustrations were taken. (MILLER AND GURLEY) At first glance this dorsal cup resembles Figs. 1-4 those of various species of Delocrinus, the Delocrinus missouriensis (part) Miller genus to which it has been assigned since and Gurley, 1890a, p. 14, pi. 2, fig. 12-13 1890. The cups of those species, how- (not fig. 11); 1890b, p. 12, pi. 2, fig. 12-13 ever, are less pentagonal in dorsal and (not fig. 11); 1890c, p. 336, pi. 2, fig. 12- ventral views than that of UC 6233A. 13 (not fig. 11); Delocrinus missouriensis The outline of this specimen is also in- Miller and Gurley, Moore and Plummer, terrupted by a sharp interradial notch in 1940, p. 255, 256, fig. 57a; Moore and dorsal view; the notch is less prominent Laudon, 1944, p. 173, pi. 62, fig. 24; pi. in ventral aspect (fig. 1, fig. 4). 65, fig. 14. In height of basal impression UC 6233A DIAGNOSIS. Same as that of genus likewise approaches species which have (see above). been attributed to Delocrinus; the height is nearly }4 that of the cup. Neverthe- DESCRIPTION AND COMPARISONS. Be- less, in erisocrinids, as exemplified by the cause they are obscured bv secondary de- genus Erisocrinus proper, a very shallow FIGURES 1-4. Eperisocrinus missouriensis (Miller and Gurley). Holotype, UC 6233A. Fig. 1, dorsal view; fig. 2, posterior view; fig. 3, anterior view; fig. 4, ventral view. All approximately twice natural size. External sutures traced in pencil prior to photographing. 176 J. J. BURKE Vol. 77 basal impression is not entirely char- little concave within the impression, but acteristic. In UI X-264, the specimen (except for the CD basal) are slightly or selected as the lectoholotype of Eriso- moderately convex at the basal plane. crinus typus Meek and Worthen by The CD basal lies above the basal plane Knapp (1969) the impression is quite ap- and is nearly flat from side to side in that parent and it is also clearly distinct in region. Beyond the basal plane the UT K-4732, the holotype of Rrisocrinus basals take on the contour of the radials, erectus Moore and Plummer (1940). In sloping out and flaring, and are only Erisocrinus knoxvillensis, the impression slightly convex. As in most species of is more pronounced than in Erisocrinus Erisocrinus, the basals occupy the greater typus (Strimple 1975, pi. 1, fig. 11). The part of the dorsal surface of the cup and higher cavity of Eperisocrinus missouri- their distal borders are rounded. ensis is simply an exaggeration of the The radials originate in the vicinity of shallower cavities found in species of the basal plane, but because the basals Erisocrinus. are convex, the proximal tips of the basals The infrabasals of Eperisocrinus mis- lie above the basal plane, not in it. In souriensis are very much reduced, more the prolongation of the proximal tips of so than in any species of Erisocrinus, the radials toward the base of the cup, and they would be barely visible on the Eperisocrinus resembles Erisocrinus erec- dorsal surface if the stem of UC 6233A tus Moore and Plummer, 1940. But one were in place. As in Erisocrinus typus of the most striking erisocrinid char- and Erisocrinus knoxvillensis the C in- acteristics of Eperisocrinus consists in frabasal is the most prominent plate of the very obtuse proximal angles of the that circlet. These plates slope steeply radial plates (about 140°); much wider downward and flare outward slightly from than the same angles in species of Delo- their origin at the summit of the stem crinus, with the possible exception of impression. For most of their length Delocrinus vulgatus Moore and Plummer, they must have constituted a very slightly 1940. rounded, almost pentagonal wall around The radial walls are outflaring to about the stem. the same extent as in Erisocrinus knox- To my knowledge, it has not been villensis, but much less than in Eriso- noted previously that the crenulae in crinus terminalis Strimple (1962), which Erisocrinus extend downward along the represents the extreme in this respect. walls of the stem impression and are not The radials, except the posterior two, are confined to the summit of the impression. about twice as wide as long and, except Strimple's illustrations (1975, pi. 1) of in length, have all the characteristics of Erisocrinus typus (fig. 8) and Erisocrinus Erisocrinus. There is practically no out- knoxvillensis (fig. 11) demonstrate this swelling of the outer radial wall below the quite clearly. Despite the crude prepara- summit; it bends in very slightly as it tion of this region of UC 6233A, the steep approaches the articular surface. infrabasal plates still retain traces of The entire radial articular surface is crenulae, distributed much as in the two definitely Erisocrinus-like. At best the species figured by Strimple. facet is little deeper than the inner wall In keeping with the reduced infra- of the radial at the summit of the plate; basals, the basals of Eperisocrinus mis- this contrasts with the deeper facet in souriensis are relatively large, larger than Delocrinus, which extends inward beyond in any species of Erisocrinus, and the in- the radial wall, rimming the body cavity. terbasal sutures are longer, practically as The outer marginal ridge faces outward, long as the interradial sutures. The bows downward, does not extend to the basals extensively wall the basal impres- full width of the facet and its inner wall sion, whereas in most species of Eriso- bears fine denticles. The outer ligament crinus they barely participate in the im- furrow is expanded transversely, lies well pression (Erisocrinus knoxvillensis ap- below the transverse crest and its inner pears to be an exception to this). wall is denticulate. The external liga- For the most part, the basals of ment pit is slitlike and moderate in Eperisocrinus miss our iensis are flat or a transverse extent. The transverse crest Ohio J. Sci. EPERISOCRINUS, NEW GENUS 177 is denticulate, visible in lateral view of tion of these plates of the posterior inter- the cup, narrows adjacent to the external radius; previous descriptions have not ligament, then expands but gradually noted these features and accompanying narrows again into delicate lateral ex- illustrations were inaccurate. Distally, tremities that do not extend to the full anal X bears a single articular facet, width of the plate.