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''Ptychodus'' (from 'fold' and 'tooth') is a genus of extinct large
accessed on 8/23/09 At least 16 species are considered valid, with the largest members of the genus suggested to have grown up to long. The youngest remains date to around 75
Due to a global distribution ''Ptychodus'' is well represented in the fossil record; many fossils have been uncovered such as isolated teeth, fragments of dentition, calcified vertebral centra, denticles, and associated fragments of calcified cartilage. The very first remains of ''Ptychodus'' were found in England and Germany in the first half of the 18th century. ''Ptychodus'' teeth have long been identified as palates of diodon, or porcupinefish (Osteichthyes, Diodontidae), well-known for their ability to inflate their bodies in defense. At the beginning of the 19th century, several authors including Swiss paleontologist Louis Agassiz eventually demonstrated the affinities of ''Ptychodus'' teeth with those of elasmobranchs (rays and sharks). The first discovery of ''Ptychodus'' teeth in Kansas came in 1868 when Leidy reported and described a damaged tooth near Fort Hays, Kansas. After, many more teeth were uncovered in almost perfect conditions and other species within the genus were identified.
Fossils of species within this genus have been found in the marine strata of United States, Brazil, Canada, the Czech Republic, France, Germany, India, Israel, Japan, Jordan, Mexico, Sweden, and the United Kingdom. The fact that so many fossils of ''Ptychodus'' have been found in different regions of the world provides evidence of a distribution of species during the Albian-Turonian time.
The generic name ''Ptychodus'' comes from the Greek words (fold/layer) and (tooth), so "fold teeth" describing the shape of their crushing and grinding teeth.
While the affinity of ''Ptychodus'' as some kind of
Unlike the colossal nektonic planktivores '' Rhincodon'' (whale sharks) and '' Cetorhinus'' (basking sharks) which relied upon gill rakers to acquire their food, the ''Ptychodus'' had a massive arrangement of crushing plate teeth. A ''Ptychodus'' jaw contains many teeth, up to 550 teeth, 220 of which are on the lower jaw and 260 in the upper jaw. These teeth were very large as well—Paleontologists believe that the largest tooth plate measured 55 centimeters in length and 45 centimeters in width. There are two distinct formations of tooth plates between the genus; one being juxtaposed, non-overlapping tooth rows, and another being imbricated tooth rows.
It is believed that the shape coincides with the diet of the species and their geographic locations, but the time it lived has a big part as well. ''Ptychodus marginalis'' teeth differ from ''Ptychodus polygyrus''. ''P marginalis'' was in the Middle Cenomanian to Middle Turonian deposits in the English Chalk, while ''P. polygyrus'' was in the Late Santonian-Early Campanian deposits.
BBC page on ''Ptychodus mortoni'': "Giant predatory shark fossil unearthed in Kansas"
{{Taxonbar, from=Q648806 Lamniformes Prehistoric shark genera Cretaceous sharks Cretaceous fish of North America Mooreville Chalk Fossil taxa described in 1835 Taxa named by Louis Agassiz Taxa named by Charles Lucien Bonaparte
durophagous
Durophagy is the eating behavior of animals that consume hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil t ...
(shell-crushing) lamniform
The Lamniformes (, from Greek ''lamna'' "fish of prey") are an order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, such as the g ...
shark
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...
s from the Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
period, spanning from the Albian
The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...
to the Campanian
The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...
. Fossils of ''Ptychodus'' teeth are found in many Late Cretaceous marine sediments worldwide.The paleobioloy Database Ptychodus entryaccessed on 8/23/09 At least 16 species are considered valid, with the largest members of the genus suggested to have grown up to long. The youngest remains date to around 75
million years ago
Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds.
Usage
Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
. A large number of remains have been found in the former Western Interior Seaway
The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...
.
Extinct animals of Indonesia
Discovery
Due to a global distribution ''Ptychodus'' is well represented in the fossil record; many fossils have been uncovered such as isolated teeth, fragments of dentition, calcified vertebral centra, denticles, and associated fragments of calcified cartilage. The very first remains of ''Ptychodus'' were found in England and Germany in the first half of the 18th century. ''Ptychodus'' teeth have long been identified as palates of diodon, or porcupinefish (Osteichthyes, Diodontidae), well-known for their ability to inflate their bodies in defense. At the beginning of the 19th century, several authors including Swiss paleontologist Louis Agassiz eventually demonstrated the affinities of ''Ptychodus'' teeth with those of elasmobranchs (rays and sharks). The first discovery of ''Ptychodus'' teeth in Kansas came in 1868 when Leidy reported and described a damaged tooth near Fort Hays, Kansas. After, many more teeth were uncovered in almost perfect conditions and other species within the genus were identified.
Fossils of species within this genus have been found in the marine strata of United States, Brazil, Canada, the Czech Republic, France, Germany, India, Israel, Japan, Jordan, Mexico, Sweden, and the United Kingdom. The fact that so many fossils of ''Ptychodus'' have been found in different regions of the world provides evidence of a distribution of species during the Albian-Turonian time.
The generic name ''Ptychodus'' comes from the Greek words (fold/layer) and (tooth), so "fold teeth" describing the shape of their crushing and grinding teeth.
Taxonomy
While the affinity of ''Ptychodus'' as some kind of cartilaginous fish
Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeleto ...
has long been accepted, the exact position in the group was long uncertain. A 2016 publication found that ''Ptychodus'' are likely true sharks belonging to Selachimorpha, rather than hybodonts
Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and Batoide ...
or batoids
Batomorphi is a division of cartilaginous fishes, commonly known as rays, this taxon is also known as the superorder Batoidea, but the 5th edition of ''Fishes of the World'' classifies it as the division Batomorphi. They and their close relati ...
as previously thought. A 2024 study of a complete skeleton concluded that they belong to the Lamniformes
The Lamniformes (, from Greek ''lamna'' "fish of prey") are an order (biology), order of sharks commonly known as mackerel sharks (which may also refer specifically to the family Lamnidae). It includes some of the most familiar species of sharks, ...
(mackerel sharks).
Description
Size
''Ptychodus'' was a large shark, previously estimated at long based on extrapolation from teeth. The subadult specimen with the largest vertebra showed that it could reach lengths of , so a length is possible, but more analysis is required for verification.Dentition
Unlike the colossal nektonic planktivores '' Rhincodon'' (whale sharks) and '' Cetorhinus'' (basking sharks) which relied upon gill rakers to acquire their food, the ''Ptychodus'' had a massive arrangement of crushing plate teeth. A ''Ptychodus'' jaw contains many teeth, up to 550 teeth, 220 of which are on the lower jaw and 260 in the upper jaw. These teeth were very large as well—Paleontologists believe that the largest tooth plate measured 55 centimeters in length and 45 centimeters in width. There are two distinct formations of tooth plates between the genus; one being juxtaposed, non-overlapping tooth rows, and another being imbricated tooth rows.
It is believed that the shape coincides with the diet of the species and their geographic locations, but the time it lived has a big part as well. ''Ptychodus marginalis'' teeth differ from ''Ptychodus polygyrus''. ''P marginalis'' was in the Middle Cenomanian to Middle Turonian deposits in the English Chalk, while ''P. polygyrus'' was in the Late Santonian-Early Campanian deposits.
Body
The only known complete body remains are from the Agua Nueva Formation in Mexico, which suggest that ''Ptychodus'' had afusiform
Fusiform (from Latin ''fusus'' ‘spindle’) means having a spindle (textiles), spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon (geometry), lemon-shape, but often implies a focal broadening of a ...
body, with a large and elongate head, the primarily dorsal fin was large and placed forward on the body while the second posterior dorsal fin was much smaller, with a small anal fin being present. The overall body form closely resembles that of the great white shark
The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large Lamniformes, mackerel shark which can be found in the coastal surface waters of all the major ocea ...
and '' Lamna'' (which includes the porbeagle and salmon shark).
Paleobiology
Based on analysis of vertebrae from Spain, it is suggested that species of ''Ptychodus'' lived relatively long lives and were slow growing and produced large offspring and small litters.Diet
''Ptychodus'' is thought to have beendurophagous
Durophagy is the eating behavior of animals that consume hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including fossil t ...
, using its low rounded teeth to crush hard-shelled organisms. Many authors have suggested that ''Ptychodus'' fed on bottom dwelling (benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
) prey like bivalves
Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...
(particularly inoceramids) and crustacean
Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s, while also consuming some hard bodied organisms that lived in open water (pelagic
The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...
). A 2024 study suggested that based on its body morphology, the species likely primarily consumed pelagic hard prey, like ammonites
Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...
and marine turtles, rather than benthic prey.
References
* Williston, Samuel (1900) ''University Geological Survey of Kansas, Volume VI: Paleontology part II, (Carboniferous invertebrates and Cretaceous fish)''External links
*BBC page on ''Ptychodus mortoni'': "Giant predatory shark fossil unearthed in Kansas"
{{Taxonbar, from=Q648806 Lamniformes Prehistoric shark genera Cretaceous sharks Cretaceous fish of North America Mooreville Chalk Fossil taxa described in 1835 Taxa named by Louis Agassiz Taxa named by Charles Lucien Bonaparte