Bonnerichthys gladius

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Bonnerichthys gladius

Temporal range: Late Cretaceous (89-83Ma)

Scientific classification:

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: †Pachycormiformes
Family: †Pachycormidae
Genus: †Bonnerichthys
Species: †B. gladius



Bonnerichthys gladius is an extinct species of actinopterygian that lived in the Western Interior Seaway (it was found in the Niobrara Formation in Kansas) during the Late Cretaceous. It was a filter feeder that subsisted on plankton. The pectoral fins each had a sharp edge that could be used as defensive weapons against predators. The tail was crescent-shaped and the upper and lower lobes were equal in length, ergo, it would have been a powerful swimmer.[1]

References:
[1] White, S. (Ed.). (2012). Dinosaur Art: The World's Greatest Paleoart. Titan Books.

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Just to prove I wasn't lying about the whole pectoral fin cutting edge part:


The above photograph is from the same source listed in the OP.



Here's further material from the Ocean of Kansas website-> with italicized captions:

LEFT: Although a fair number (about 20) of specimens of the fins of this species have been collected from as far back as the 1870s (Stewart (1988), up until now, I had only collected a small piece of one... the fin fragment shown above left, discovered a little ways north of Castle Rock in Gove County. In cross-section and front view, this fragment illustrates the sharp leading edge of these fins.
Note: 'Protosphyraena' gladius was the former name of Bonnerichthys gladius.


LEFT: Here's the fin as prepared (Photo by K. Shimada) - Note the heavy and relatively sharp leading edge (lower side of photo):

[kekistani]

Jan 4, 2020 4:50:24 GMT 5 Infinity Blade said:

Just to prove I wasn't lying about the whole pectoral fin cutting edge part:


The above photograph is from the same source listed in the OP.



Here's further material from the Ocean of Kansas website-> with italicized captions:

LEFT: Although a fair number (about 20) of specimens of the fins of this species have been collected from as far back as the 1870s (Stewart (1988), up until now, I had only collected a small piece of one... the fin fragment shown above left, discovered a little ways north of Castle Rock in Gove County. In cross-section and front view, this fragment illustrates the sharp leading edge of these fins.
Note: 'Protosphyraena' gladius was the former name of Bonnerichthys gladius.


LEFT: Here's the fin as prepared (Photo by K. Shimada) - Note the heavy and relatively sharp leading edge (lower side of photo):

What book is this?

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I said the first pic was from the same source I cited in the OP. The other two are from the Ocean of Kansas website, which I also linked to.

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The Shock of Unexpected ConservatismThe Shock of Unexpected Conservatism

Pachycormid taxonomy has accepted the twin lineage pattern of toothed and toothless tribes, leading respectively to the Late Cretaceous Protosphyraena and Bonnerichthys, for over ten years. Recent work on pectoral fin morphotypes has revealed a diversity of forms, reflecting specialization in swimming styles. Examination of pectoral girdle components led to an unexpectedly similar set of characteristics between these two genera, supposedly separated by a gap of over 100 million years since their common ancestor. This raises the question of whether these two taxa are as distantly related as current pachycormid phylogenetic hypotheses suggest.

cienciasdaterra.novaidfct.pt/index.php/ct-esj/article/view/393