Pseudocybele Ross, 1951

Mcadams, Neo E. B. & Adrain, Jonathan M., 2010, A new species of the Lower Ordovician pliomerid trilobite Pseudocybele and its biostratigraphic significance, Zootaxa 2550, pp. 21-38 : 24-25

Pseudocybele Ross, 1951

Type species. Pseudocybele nasuta Ross, 1951 .

Other species. Pseudocybele altinasuta Hintze, 1953 ; P. paranasuta n. sp.

Discussion. Members of Pseudocybele are common as disarticulated silicified sclerites at many horizons throughout the Blackhillsian in the Great Basin. At Ibex, species ranges extend through the upper part of Section H (from H 191.7 m [Hintze's (1953) H-20/ 434'] upwards) and the lower part of Section J. Ross's (1951) Clarkston Mountain and Round Hill localities in northern Utah, and Hintze's (1953) Yellow Hill locality in eastern Nevada also yield species of Pseudocybele . Dean (1989) assigned several crack-out specimens from the Canadian Rocky Mountains to Pseudocybele nasuta . However, their poor state of preservation likely precludes identification to species level.

Pseudocybele nasuta Ross, 1951 , is difficult to interpret pending new collections from the type locality. Ross's specimens are small and were figured at low magnification without a full complement of views. The largest cranidium figured in dorsal view ( Ross, 1951, pl. 33, figs 1, 2, 5), which is fragmentary, is 2.75 mm long, whereas typical large cranidia of P. paranasuta figured herein are around 4 mm long. Ross's holotype cranidium of P. nasuta is about half the size (length 2 mm) of the holotype of P. paranasuta . Most are likely immature, and Ross reported (1951, p. 139) that he found only immature silicified pygidia. Although we have found many species of Pseudocybele in our samples, we have not yet resampled the Clarkston Mountain type locality, and it is difficult in the present state of knowledge to determine which species from other localities (if any) truly represent P. n a s u t a. Further complicating matters, Ross (1951, p. 140) reported P. nasuta from a 35 foot (10.7 m) interval at Clarkston Mountain, and from a 30 foot (9.1 m) interval at Round Hill. He did not specify a footage for any of his figured specimens. We have resampled Round Hill, and two species of Pseudocybele , one of which may be P. n a s u t a, co-occur at several horizons there. This suggests that Ross's material from Clarkston Mountain may also contain more than one species, and that the figured material of P. nasuta must be interpreted with caution. Comparison below is therefore made with reference only to Ross's figured specimens from the type locality, but more material from Clarkston Mountain will be required before P. nasuta may be interpreted with confidence.

All specimens of Pseudocybele reported to date have been assigned to either Pseudocybele nasuta Ross , P. altinasuta Hintze , or P. lemurei Hintze, 1953 . Our new data indicate that the species diversity of Pseudocybele has been substantially underestimated, as multiple new species occur in the sections. Some new species have been misidentified in the past, and some occur in previously unsampled faunas. Further, " Pseudocybele " lemurei has been reassigned to the new genus Lemureops McAdams and Adrain, 2009a, which is the probable sister taxon of Pseudocybele . Full revision of Pseudocybele and phylogenetic analysis of its broader relationships is beyond the scope of this paper, but will be dealt with in a future publication.