Orthacanthus, meaning “straight spine”, was a 10 foot long freshwater shark-like fish which lived during the late Carboniferous Period and early Permian Period roughly 315-275 million years ago. The genus Orthacanthus is divided into twelve different species, two of which lived in Texas during the early Permian Period approximately 280 million years ago, and thus inhabited the same landscape as more famous early Permian creatures like Dimetrodon, Edaphosaurus, and Eryops.
Orthacanthus belonged to an order of cartilaginous fish called the xenacanthids, meaning “strange spines”, which existed from the Carboniferous to the Triassic Period. The xenecanthids were not true sharks, but were close relatives. The group’s most famous member, the eponymous Xenacanthus, measured 6 feet long and its fossils have been found around the world in rocks dated to the Carboniferous and Permian Periods. The xenacanthids were freshwater species, and they may have been the largest fish species within their particular environments. At 10 feet long, Orthacanthus was far larger than any of the amphibians it shared its habitat with, and it was likely the top predator in its environment. In fact, evidence shows that it cannibalized other members of its kind.
Below is a drawing which I made of Orthacanthus. The illustration was made with No.2 pencil, No.3 pencil, and Crayola colored pencils on printer paper. I decided to give this animal a brownish-tan coloration to blend in with the supposed murky water of its bayou-like habitat, as well as faint dark stripes reminiscent of a modern-day Tiger Shark to provide added camouflage.
Orthacanthus. © Jason R. Abdale (August 27, 2023).
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Categories: Paleontology, Uncategorized
DINOSAURS AND BARBARIANS 
I love prehistoric shark relatives, especially when it means discovering a new one (for me)! The colors are lovely and very plausible for a bayou environment. I love to see the layering of color with colored pencils. It provides a lot of depth and subtlety to the pattern that I’m sure looks even better in person. 🙂