Ausich et al.—Disparid and hybocrinid crinoids from the Brechin Lagerstätte


Materials.—CMCIP 22560, 36433, and 55395;UMMP74669, 74687.1, and 74687.2.


Measurements.—UMMP 74669: CrH, 30.5*; maximum ACH, 18.2; maximum ACW, 17.3; ArH, 16.2*; CoH, 3.1*.


Remarks.—In describing his new species Hybocrinus pristinus, Billings (1858, p. 24) noted: “This species so closely resembles H. tumidus of the Trenton Limestone, that I have had much doubt as to the propriety of separating it therefrom. The only differences that I can perceive are, that it is always smaller that the Trenton form, the plates more coarsely granulated under a lens, and not so convex in their centres [sic]. In a well-preserved specimen of H. tumidus the column exhibits from eight to ten joints in the length of one line, where as in H. pristinus there are only five. Under these circumstances I have thought it best to distinguish that Chazy specimens by a separate name for the present.” This distinction recognized by Billings is readily explained by ontogenetic variation, and we consider H. pristinus to be a junior synonym of H. tumidus. Therefore, the Katian crinoid faunas have only two species of Hybocrinus, H. conicus and H. tumidus. These two Katian species are distinguished because H. tumidus has a summit surface that is tilted, basal plates unequal in size, the distal margin of the first anal plate with deep grooves, and an asymmetrical position of the column facet. In contrast, H. conicus has a summit surface that is not tilted, basal plates approximately equal in size, the distal margin of the first anal plate lacking deep grooves, and a symmetrical position of the column facet.


Family Hybocystitidae Jaekel, 1918 Genus Hybocystites Wetherby, 1880


Type species.—Hybocystites problematicus Wetherby, 1880, by monotypy.


Occurrence.—Ordovician (Katian), New York, USA and Ontario, Canada.


Remarks.—As noted below, Hybocystites is now considered monospecific with the recommendation herein that H. problematicus and H. eldonensis are conspecific.


Hybocystites problematicus Wetherby, 1880 Figure 9.6


1880 Hybocystites problematicusWetherby, p.7,pl. 5, fig. 1a–c.


1882 Hybocystites problematicus; Carpenter, p. 307, pl. 11, figs. 6–24.


1889 Hybocystites problematicus; Miller, p. 256, fig. 342.


1900 Hybocystis problematicus; Bather in Lankester, p. 95, fig. 1.


1908 Hybocystites problematicus; Parks, p. 232, pl. 2, figs. 1–3, 5.


1908 Hybocystis eldonensis Parks, p. 234, pl. 2, fig. 4. 1911 Hybocystis eldonensis; Springer, p. 13, pl. 2, figs. 1–10. 1915 Hybocystites eldonensis; Bassler, p. 654. 1915 Hybocystites problematicus; Bassler, p. 655. 1938 Hybocystites problematicus; Bassler, p. 115.


867


1943 Hybocystites eldonensis; Bassler and Moodey, p. 515. 1943 Hybocystis problematicus; Bassler and Moodey, p. 516. 1943 Hybocystis eldonensis; Bassler and Moodey, p. 515. 1943 Hybocystites eldonensis; Moore and Laudon, p. 130, pl. 1, fig. 8.


1948 Hybocystis eldonensis; Cuénot, p. 55, fig. 69. 1948 Hybocystites problematicus; Regnell, p. 9, fig. 3B. 1953 Hybocystites eldonensis; Ubaghs, p. 749, figs. 143, 144. 1953 Hybocystites problematicus; Ubaghs, p. 749, fig. 80c. 1973 Hybocystites eldonensis; Webster, p. 152. 1973 Hybocystites problematicus; Webster, p. 152. 1975 Hybocystites problematicus; Strimple, p. 51, fig. 1.


1978 Hybocystites eldonensis; Brett and Liddell, p. 338, figs. 5.8, 7–9.


1978 Hybocystites problematicus; Sprinkle and Moore, p. T572, fig. 365.1a, b.


1978 Hybocystites eldonensis; Ubaghs, p. T138, figs. 109.5– 109.6, 151.4, 174.11.


1978 Hybocystites eldonensis; Sprinkle and Moore, p. T574, fig. 365.1c–j.


1981 Hybocystites problematicus; Arendt, p. 164, fig. 29b. 1981 Hybocystites eldonensis; Arendt, p. 164, fig. 29e–zh. 1985 Hybocystites eldonensis; Rozhnov, p. 5, fig. 1d. 1985 Hybocystis eldonensis; Smith, p. 170, pl. 7.4.22. 1986 Hybocystites eldonensis; Rozhnov, p. 1, fig. 1e. 1986 Hybocystites problematicus; Webster, p. 174. 1986 Hybocystites eldonensis; Webster, p. 174. 1988 Hybocystites problematicus; Webster, p. 96. 1988 Hybocystites eldonensis; Webster, p. 96. 1993 Hybocystites eldonensis; Webster, p. 70. 1999 Hybocystites eldonensis; Brett and Taylor, p. 69, fig. 79. 2002 Hybocystites eldonensis; Rozhnov, p. 584, fig. 44e.


1981 Hybocystites problematicus; Parsley, p. 4, pl. 1, figs. 7, 8, 10.


1944 Hybocystites eldonensis; Moore and Laudon, p. 151, pl. 53, fig. 1.


Holotype.—The holotype of Hybocystites problematicus has not been located with certainty; the holotype of H. eldonensis is ROM 23779.


Occurrence.—Wetherby’s original specimens of Hybocystites problematicus were reportedly from the upper Trenton (Katian) in Mercer County, Kentucky, USA, and H. eldonensis was originally reported from Kirkfield, Ontario, Canada. This taxon is now known from the Curdsville Member of the Hermitage Formation (Katian) in Anderson, Garrard, Hermitage, and Jessamine counties in Kentucky; the HullMember of the Ottawa (now Bobcaygeon) Formation and the Bobcaygeon Formation at Kirkfield, Ontario. New material is from the Bobcaygeon- Verulam contact zone at the Carden Quarry (UMMP 74670) (Ordovician, Katian).


Description.—Crown medium-sized. Aboral cup medium globe-shaped (Fig. 9.6); maximum width to maximum height ratio ~1.0; all plates with coarse sculpture as noted below. Basal circlet ~33% of aboral cup height. Basal plates five,


pentagonal, equal in size, as high as wide; coarsely nodose plate sculpture that can be irregular or roughly arranged in rows


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