This is Mazon Monday post #19. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
-----------------------------------------------------
Reconstruction of Mazon Creek by John Megahan
Would you believe that Illinois has a shark nursery? OK, it is about 307 million years old and the evidence resides in Mazon Creek fossil concretions. The first species, Bandringa rayi, was described in a paper published by Rainer Zangerl in the Field Museum's journal Fieldiana back in 1969. The specimen used is the paper is the one pictured below, which is an absolutely awesome specimen!
In 2014, a paper by Lauren Cole Sallan and Michael I. Coates was published in the Journal of Vertebrate Paleontology called "The long-rostrumed elasmobranch Bandringa Zangerl, 1969, and taphonomy within a Carboniferous shark nursery". It looked at two species, B. rayi and B. herdinae to better understand the morphology of the sharks and the environment they lived in.
The shark Bandringa (Elasmobranchii, Chondrichthyes), from the Pennsylvanian (Moscovian) Lagerstätte 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.
Additionally, Bandringa rayi was discussed in Creature Corner back in April 1990.
Bandringa rayi (fish)
Bandringa rayi is a superb example of Nature copying/developing similar structures in different Phyla or Classes, often millions of years after the extinction of the original design. Much like stealing someone else's patent. That relict of the Cretaceous Period, Polyodon spathula (paddlefish, spoonbill) which is found in the large rivers and lakes of the Mississippi River system has a near relative living in the Yangtze River in China and bears a great resemblance to the Pennsylvanian-Permian freshwater shark Bandringa rayi. Their feeding habits are presumed to have been the same. "My impression of Bandringa is one of a bottom dwelling fish that fed on organisms stirred up from the mud by the rostrum" (D. Baird, 1978). The same can be said of the paddlefish. Physical similarity goes beyond the amazingly like construction of the long paddle/snout/rostrum. Both animals also possess a shark-like tail. have a body lacking scales or dermal denticles, with skeletons that are chiefly cartilage. Yet Bandringa is a member of the Class Chondrichthyes (cartilaginous jawed fishes) Suborder Ctenacanthoidea, while Po/yodon is a member of the Class Osteichthyes (bony fish). Similar life-style, similar construction?
8andringa rayi was first described by Zangerl (1969) from a Pit 11 concretion that contained a small, immature shark about 110 mm (4 and ½ inches) long. This first known specimen of 8. rayi was preserved so as to give an overhead view of it. Long rostrum, large eyes, two dorsal fins with spines, anal and tail fins can be seen. In 1978, D. Baird described a second specimen of 8. rayi from Cannelton, PA that had been laying undescribed in the Princeton Museum collection since 1877. This specimen was five times the length of the type specimen. Several features, notably the larger teeth of this more mature specimen, aided in a better reconstruction of 8. rayi. Baird went on to state that this "spoonbill dogfish" was in truth a freshwater shark, since the Cannelton biota was unquestionably a freshwater environment, and ctenacanthoid sharks were inhabitants of freshwater lakes and streams during the Carboniferous-Permian.
The uncertainly of a freshwater or marine environment for B. rayi continues. Several specimens of this spoonbill shark have been discovered at Pit 11 during the last few years. Since Pit 11 contains the Essex biota , which consists of marine animals and/or animals that have been washed in from fresh or brackish water areas Baird's hypothesis remains in question.
- Andrew A. Hay
