Middle Devonian Gladbachus enters the LRT alongside the previously omitted whale shark, Rhincodon

Gladbachus adentatus (Heidtke & Krätschmer 2001; Burrow and Turner 2013; Coates et al. 2018; Middle Devonian, est. 54cm; Figs. 1, 2) was originally considered an ‘unfamiliar’ basal chondrichthyan close to acanthodians (spiny sharks) and placoderms.

By contrast
in the large reptile tree (LRT, 2005 taxa) Gladbachus (Figs. 1, 2) nests with the whale shark, Rhincodon (Figs. 3, 4), derived from Early Silurian Loganellia (Fig. 5). Gladobachus was a toothless taxon with a low, wide gape, filtering small, nektonic (= free swimming) prey with enormous gill bars, yet has never been compared to the quite similar whale shark.

References
Burrow C and Turner S 2013. Scale structure of putative chondrichthyan Gladbachus adentatus Heidtke & Krätschmer, 2001 from the Middle Devonian Rheinisches Schiefergebirge, Germany. Historical Biology 25(3):385–390.
Coates et al. (7 co-authors) 2018. An early chondrichthyan and the evolutionary assembly of a shark body plan. Proc. R. Soc. B 285:20172418. http://dx.doi.org/10.1098/rspb.2017.2418
Heidtke UHJ and Krätschmer K 2001. Gladbachus adentatus nov. gen. et sp., ein primitiver Hai aus dem Oberen Givetium (Oberes Mitteldevon) der Bergisch Gladbach – Paffrath-Mulde (Rheinisches Schiefergebirge). Mainzer geowiss. Mitt. 30, 105–122.

Publicity from 2018:
https://www.livescience.com/61315-humans-sharks-common-ancestor.html

https://news.uchicago.edu/story/study-ancient-fossil-complicates-shark-family-tree

https://www.marinetechnologynews.com/news/ancient-sharks-likely-diverse-556106 “This research, supported by the National Science Foundation (NSF), pushes the date for the last common ancestor between sharks and other types of jawed vertebrates back to 440 million years ago – more than 17 million years older than the previous estimate – and raises new questions about what life was like during a prehistoric period long shrouded in secrecy.”

wiki/Gladbachus