A new species ofBransonella(Chondrichthyes, Xenacanthimorpha, Bransonelliformes) from the Middle Permian Kaibab Formation of northern Arizona

Abstract

Isolated teeth from the Middle Permian (early Guadalupian) Kaibab Formation of Arizona are described as a new species of the xenacanth shark genus Bransonella. Bransonella tribula n. sp. is a small tooth in which the intermediate cusp is 65% of the length of the principal cusps and the cristae on the labial face extend down over the base, covering it, and bifurcating to form distinctive double crested ridges. Fin spines from the same localities in the Kaibab Formation show the characteristic xenacanth feature of a double row of large thorn-like denticles along the posterior margin. Bransonella tribula n. sp. is the only xenacanth shark known from the Kaibab Formation at present, however, due to the lack of articulated material the fin spines are attributed to ?Bransonella tribula n. sp. The ecomorphology of Bransonella suggests a primitive, small, gracile, marine xenacanth that fed near the sea floor like the modern catsharks (Scyliorhinidae).

Carboniferous chondrichthyan assemblages from the Surprise Canyon and Watahomigi formations (latest Mississippian–Early Pennsylvanian) of the western Grand Canyon, Northern Arizona

“…Remarks.-Bransonella is known from four species and ranges from the Middle Mississippian to the middle Permian worldwide (Elliott and Hodnett, 2013). Of these four, B. lingulata Ivanov and Ginter, 1996 and B. nebraskensis occur in the latest Mississippian.…”

“…Bransonella is known from four species and ranges from the Middle Mississippian to the middle Permian worldwide (Elliott and Hodnett, 2013). Of these four, B .…”

“…The oldest xenacanthids are Diplodoselache woodi Dick, 1981 from the Visean of the Oil Shale groups of Scotland, which comes from a lagoonal deposit that had both marine and brackish influences (Dick, 1981), and Reginaselache morrisi Turner and Burrow, 2011 from the mid-Visean Ducabrook Formation of central Queensland, which comes from estuarine deposits (Turner and Burrow, 2011). Bransonella itself is primarily known from marine environments (Ivanov and Ginter, 1996; Elliott and Hodnett, 2013), but was also recovered from the estuarine Lower Pennsylvanian Black Prince Limestone in the Swisshelm Mountains in Southern Arizona, together with the xenacanths Triodus and Orthacanthus and lepospondyl amphibians (Thayer, 1985; Johnson and Thayer, 2009). The Watahomigi Formation has no indication of brackish or fresh water influences and so we consider Hokomata parva n. gen. n. sp.…”