| Ptychodus Temporal range: Early-Late Cretaceous | |
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| Restoration of Ptychodus sp. by Gojiraaaaaaaaaa | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Family: | †Ptychodontidae |
| Genus: | †Ptychodus Agassiz, 1835 |
| Species: | †P. latissimus |
| Type species | |
| †Ptychodus latissimus | |
| Referred Species | |
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Ptychodus is an extinct genus of durophagous (shell-eating) shark from late Cretaceous (Albian to Campanian). It was an agile lamniform shark that feeds on ammonites and potentially sea turtles. It has a worldwide distribution. Some species were as large as 10 metres long.
Discovery and Naming[]
Because of its worldwide nature, many undescribed fragments of Ptychodus specimens have been found prior to their formal discovery by palaeontologists in the first half of the 18th century. This holotype was originally described as teeth from the palates of giant porcupinefish, which had superficially similar teeth specialized for crushing their prey. However, several authors demonstrated the teeth's affinities with those of chondrichthyian fish. Eventually, more teeth were discovered in Kansas in what would be the Western Interior Seaway, marking its global distribution.
The genus was formally named by Dr. Louis Agassiz in 1835 with the type species P. latissimus along with several other species in his later papers. The generic name stems from the Greek words "ptychos" and "odon" to mean "folding tooth" in reference to the unique crushing teeth the genus has.
Classification[]
After being described as some sort of chondrichthyian rather than a member of Diodontidae (porcupinefish), a general consensus emerged that Ptychodus was some sort of hybodontiform shark, later being reassigned to be part of the neoselachians (true sharks). While generally described as some sort of benthic, slow moving bottom feeder, few well-preserved skeletons show Ptychodus as a pelagic species of shark specialized for hunting species such as ammonites. Early in 2024, in the Agua Nueva Formation, several complete, exceptionally preserved skeletons of Ptychodus were found, which depicts it as a fast moving, agile shark, now found to be a lamniform. Ptychodus is currently housed as the sole genus of its family, Ptychodontidae.
Description[]
Ptychodus was a genus that had numerous species of differing sizes, ranging from the tiny, P. occidentalis at 1.4 m long to the massive P. latissimus, which is up to 10 metres long. Most species were around 4 to 5 metres long. As a shark, Ptychodus has a large, agile form with a fusiform body, perfect for slicing through the water and swimming at high speeds. It has a large and elongated head with a broad snout and large jaws which possessed numerous, blunt and globular teeth which were typically arranged in large teeth plates, which could number to up to 550 teeth in a jaw. Morphology of the teeth varies among species and can be cuspidate or non-cuspidate and can have different arrangements. Like most pelagic sharks, it would have most likely had countershaded coloration allowing it to conceal itself from predators and prey, from above and below.
Paleoecology[]
Ptychodus would have filled a very unique niche; it was a specialized durophagous hunter perfectly adapted to hunt shelled prey such as ammonites and sea turtles, which it would have hunted by using its batteries of teeth to crush and masticate. Previously thought to be a benthic hunter of rudists, inoceramids and crustaceans, its pelagic nature would have made these most likely only infrequent prey items which it would have snacked on time to time. However, it was specialized specifically for ammonites and sea turtles. This would have made it fill a convergent niche with species such as Globidens.
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