Bransonella? nebraskensis ( Johnson, 1984 )

Johnson, Gary D. & Thayer, David W., 2009, Early Pennsylvanian xenacanth chondrichthyans from the Swisshelm Mountains, Arizona, USA, Acta Palaeontologica Polonica 54 (4), pp. 649-668 : 663

Bransonella? nebraskensis ( Johnson, 1984)

Material.—Two teeth, UAPL 23508 and UAPL 23509.

Description.—Base of UAPL 23508 wider (l−l) than long (am−pl; Table 2), apical button in contact with intermediate and principal cusps, with smooth transition between lingual margin and base, appearing to reach lingual bifurcation of base; both principal cusps broken near base, intermediate cusp broken at base. Base of UAPL 23509 wider (l−l) than long (am−pl; Table 2), apical button in contact with one principal cusp and with intermediate cusp, otherwise similar to UAPL 23508; principal and intermediate cusps broken near base. Semicircular basal tubercle in both teeth; both with two aboral foramina; oral foramina absent in both teeth.

Remarks.—Both teeth are questionably assigned to Bransonella nebraskensis , largely because of incompleteness and interference from matrix. They are well within the size range of B. (Xenacanthus) nebraskensis teeth ( Johnson 1984), in which the apical button is always in contact with the intermediate cusp and nearly so with the principal cusps ( Johnson 1984: figs. 3–14). However, the small number of aboral foramina ( Table 2) is unusual for B. (X.) nebraskensis ( Johnson 1984: fig. 1). Besides its occurrence in the Pennsylvanian of North America, Gzhelian age ( Johnson 1984), Bashkirian (this paper), it also occurs in the Mississippian of Europe, Viséan age ( Ivanov and Ginter 1996; Ivanov 1999; Hampe and Ivanov 2007a) and Asia (Siberia) ( Rodina and Ivanov 2002). Hampe (2003: 236) mentioned two other occurrences from Kansas in North America: one is Late Pennsylvanian (Bell Limestone Member, Lecompton Limestone, Shawnee Group, middle Gzhelian; Tway and Zidek 1983: fig. 52, as “Subtype 173”; West 1990: fig. 1; Hills and Kottlowski 1983); the second is Early Permian ( Schultze 1985: fig. 4.1), as Xenacanthus luedersensis, Funston Limestone, Council Grove Group, middle Sakmarian ( Wardlaw et al. 2004). The tooth mentioned by Schultze (1985) is the only known Permian occurrence.