Sidetes chagrinensis (Ruedemann, 1916)
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Figure 3 Sidetes chagrinensis (Ruedemann, 1916). 1. Neotype, CMNH 3745, from Big Creek in Cleveland. 2. CMNH 3746, from Chance Creek in Lorain Co. 3. USNM 112031, from the Arbuckle Mountains of Oklahoma. (Spathiocaris tenuicosta Cooper, 1932). Scale is one centimeter. Click on the thumbnails for enlargements.
Spathiocaris chagrinensis RUEDEMANN, 1916, p. 95.
Spathiocaris tenuicosta COOPER, 1932, p. 350.
Diagnosis.--Structure elongate semielliptical, length greater than width. Posterior margin strongly rounded and narrow; greatest width anterior near rostrum. Lateral margins but slightly curved, extending obliquely forward; anterior margin straight or broadly concave. Concentric ridges closely arranged, not very prominent. Fine longitudinal lines along hood radiate from rostrum to posterior tip.
Description.--Fossil elongate semielliptical, appearing as a rounded isosceles triangle with base at anterior margin. Length about one quarter greater than width, ranging from 25 to 38mm. Posterior margin strongly rounded and narrow, lateral margins slightly sinuously curved, extending obliquely forward to anterior margin, which is straight or slightly obtuse and concave. Concentric ridges closely arranged (14-28/cm), not very prominent. Fine longitudinal lines along hood radiate from rostrum to posterior tip, diverging slightly.
S. newberryi, S. lutheri, and S. lata are each broader than S. chagrinensis, with width/length ratios approximately one or greater. S. ulrichi and S. emersoni, while also narrow, differ significantly in that the anterior margins are strongly curved rather than straight.
Type.--Ruedemann's holotype was collected from the Chagrin Shale at Chippewa Creek in Brecksville, Ohio. It was part of the Western Reserve University collection, which was transferred to the Cleveland Museum of Natural History. This specimen has not been located, however. In this light, we designate CMNH 3745 as neotype to serve in place of the missing holotype.
Material.--Examined in this study were two specimens collected in June or July of 1965 by William Hlavin from the Cleveland Shale. CMNH 3745 is from Big Creek near W. 117th St. in Cleveland, and CMNH 3746 is from Chance Creek, Lorain County. Also studied were two specimens from the Woodford Shale assignable to this species, namely USNM 112031, Cooper's (1932) holotype of S. tenuicosta, and one of the syntypes of S. gouldi, USNM 112035, both from the Arbuckle Mountains of Oklahoma.
Remarks.--Few specimens from the Chagrin Shale are well-preserved, and none of those now available represent this species. Even though the specimens in this study are from a different unit than the primary types, in all other respects they appear to conform to Ruedemann's description and illustrations of the species.