THE LONG-ROSTRUMED ELASMOBRANCH BANDRINGA ZANGERL, 1969, AND TAPHONOMY WITHIN A CARBONIFEROUS SHARK NURSERY

摘要

The shark Bandringa (Elasmobranchii, Chondrichthyes), from the Pennsylvanian (Moscovian) Lagerst?tte of Mazon Creek, Illinois, is notable for an elongated snout constituting up to half of total body length. This genus formerly contained two distinct species (B. rayi and B. herdinae). However, reexamination of all cataloged material from Mazon Creek and similarly aged North American coal measure localities shows that characteristics previously considered diagnostic at the species level can be attributed to differential taphonomy in adjacent marine and non-marine deposits. We find no evidence of morphologically distinct populations. A monospecific Bandringa exhibiting complementary data sets from localities with different modes of preservation provides a more complete picture of hard- and soft-tissue anatomy than resident taxa from a single deposit. Our new reconstruction of Bandringa incorporates several previously unreported features, including ventrally directed jaws, stellate squamation, a branched lateral line, and fin spines bearing smooth costae. Bandringa occupies an unresolved position within total-group Elasmobranchii, but displays similarities with sphenacanthids, hybodontiforms, and other member clades of the stem group. Bandringa is most simply interpreted as a freshwater, benthic, suction-feeding shark, and as a plausible analogue of modern sawfish (Pristidae). Juveniles of the Carboniferous Bandringa appear to have inhabited one of the earliest known shark nurseries at the brackish and marine Mazon Creek before migrating to freshwaters elsewhere.