Bandringa

Credit: John Megahan.

*Bandringa*, sometimes called the "spoonbill dogfish", is an extinct genus of ctenacanthiforme elasmobranch that lived in the United States during the Late Carboniferous.

## History

Rainer Zangerl (1969) first named *B. rayi* from exceptionally-preserved specimens recovered by Ray Bandringa from Mazon Creek. PF 5686, a juvenile, is the holotype, and was recovered from an ironstone concretion in summer 1967. Originally, *B. rayi* and *B. herdinae* were erected as different species, but later analyses found they were no different; only changed by taphonomic causes. All Mazon Creek specimens appear to be juveniles, due to a lack of developed cartilaginous skeletal structures, and it was suggested the area was a nursery, which was supported to fossil egg capsules of unknown affinities. *B. rayi* has also been recovered from spoil heaps in Five Points coal mines near Conesville, Pennsylvania.

The holotype comes from a Pit 11 concretion, measuring ~110 millimeters (4.5 inches), and is preserved in a 2D concretion. It is oriented face-down, with the eyes (who are large), dorsal fins and spines and tail fins visible. D. Baird (1978) described another specimen from Cannelton, which had remained in the Princeton Museum since 1877, undescribed. It was 5x the length of the holotype, having larger teeth, suggesting a more mature individual. This aided greatly in paleoart. Baird called it a "spoonbill dogfish". In Pit 11, more specimens were son recovered from the Essex biota (marine animals/animal who were swept from fresh or brackish water and fossilized).

## Description

*Bandringa* bears a notable elongate snout that reaches up to half of the total body's length. The two previous species are noted to be "differentiated" via "differential taxonomy in adjacent marine and non-marine deposits", and thus, no evidence of morphologically-distinct populations are found. Preserved fossils often give an an outline of the animal as it was in life, being one of the most complete hard-soft tissue datasets in the Mazon fauna. Lauren Cole Sallan and Michael I. Coates (2013) found new characters previously ignored in *Bandringa*; ventrally-directed jaws, stellate squamation, a bifurcated lateral fin and fin spines with smooth costae. Still, even with a better understanding of its remains, *Bandringa* remains an anomaly, as its taxonomic position is often disputed. However, it resembles sphenacanthids, hybodontiforms and other stem clades.

One of the most striking features of *Bandringa* is the sawfish-like rostrum, which is a great example of convergent evolution observable in nature. It was probably a bottom-dweller, who disturbed mud with its snout to find food. It's body is very shark-like, lacking of dermal denticles and a cartilaginous skeleton, similar, but unrelated, to *Polyodon*. It has spheroid melanosomes in the eyes, which has been used to argue for non-vertebrate affinities in *Tullimonstrum*.

## Paleobiology

Bandringa is an anomaly among fossil fish for having a fully known breeding cycle, with adults living in freshwater swamps and rivers and the juveniles in brackish and saltwater environment, opposite of salmon. The juveniles would swim upstream into freshwater, which aligns with the geography of the time, with a diagonally-running stream that connected the two bodies. This is indicated by the freshwater individuals preserving skeletal elements and the marine individuals preserving soft tissues, as studied by Sallan and Coates (2014). This study examined autapomorphies, morphology and examined the two species. They also found egg cases and juveniles in the same marine sediments in a 310 million-year-old shark nursery. Females would have traveled downstream to lay their eggs in shallow marine waters, where the cycle would repeat.

## Paleoecology

*Bandringa* is interpreted as a freshwater-dwelling, benthic, suction-feeding fish, possibly comparable to modern Pristidae. Juveniles appear to inhabit a type of nursery, being one of the earliest-known sites. Mazon Creek would have been brackish, an environment where they would spawn, mature and migrate into freshwaters when mature. Preserved gut contents preserve articulate arthropods.

In the Mazon Creek beds, it was part of the Essex fauna, which consists 42% of *Essexella*, and lived with *Tullimonstrum*, sea worms (including *Etacystis*), snails, saltwater clams, shrimp (including *Belotelson*), sea scorpions, cephalopods and fish. In some areas, it may have been roughly contemporaneous with the Kittaning Formation.

## References

1. ↑ https://www.biodiversitylibrary.org/bibliography/5206#/summary
2. ↑ 2.0 2.1 https://www.esconi.org/esconi\_earth\_science\_club/2020/08/mazon-monday-19-species-spotlight-bandringa-rayi-mazoncreek-fossils-mazonmonday-shark.html
3. ↑ Creature Corner, April 1990
4. ↑ R. Zangerl. (1979). New Chondrichthyes from the Mazon Creek fauna (Pennsylvanian) of Illinois. *Mazon Creek Fossils* 449-500
5. ↑ https://web.archive.org/web/20200311005108/http://pure-oai.bham.ac.uk/ws/files/39492257/Tullimonstrum\_Palaeo\_Revision\_FINAL.pdf
6. ↑ https://news.upenn.edu/news/tully-monster-mystery-far-solved-penn-led-group-argues
7. ↑ http://www.sci-news.com/paleontology/science-nursery-bandringa-sharks-01678.html
8. ↑ https://www.tandfonline.com/doi/abs/10.1080/02724634.2013.782875
9. ↑ https://doi.org/10.1111%2Fj.1502-3931.1987.tb02028.x
10. ↑ https://books.google.ca/books?vid=ISBN9781840766233&redir\_esc=y