''Toxoprion'' (

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

for "bow saw") is an extinct genus of eugeneodont holocephalans whose fossils are found in marine strata from the Early

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

until the Late

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

near Eureka, Nevada.

Description

''Toxoprion'' was one of the many

eugeneodonts which bore a palatoquadrate fused to its skull or reduced in other forms, and had its heavily serrated teeth grow outwards on the

symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...

of the lower jaw similar to a rounded saw. Despite its jaw showing similarities to another eugeneodont, ''

Helicoprion ''Helicoprion'' is an Extinction, extinct genus of shark-like Chondrichthyes, cartilaginous fish in the order Eugeneodontiformes. Almost all ''Helicoprion'' Fossil, fossils consist of spirally-arranged clusters of fused teeth, called "tooth whor ...

'', the tooth row of ''Toxoprion'' does not coil back on itself, as seen in ''

,'' but instead forms a downward curved tooth whorl similar to '' Campyloprion'', '' Lestrodus'', and ''

Edestus ''Edestus'' is an extinct genus of Eugeneodontida, eugeneodontid holocephalian fish known from the Late Carboniferous (Pennsylvanian (geology), Pennsylvanian) of the United Kingdom, Russia, and the United States. Most remains consist of isolated c ...

''. As in most members of eugeneodontida, the smaller teeth found near the anterior end of the whorl represent the oldest teeth, which the animal grew as a juvenile and the larger and younger teeth found near the back of the whorl represent teeth grown in adulthood. An interesting distinction of Toxoprion are that its older anterior teeth typically appear more rounded than the younger and sharper teeth near the back of its whorl. This may represent damage from feeding or may signify a change in diet and/or feeding strategy with age.

Taxonomy

The genus acquired its name from the Greek word τόξο (''tóxo''), from the bow-shaped jaw on which the teeth of the creature were arranged, and πριόνι (''prióni''), for the number of triangular serrated teeth it had. While originally suggested to be a member of the genus ''

'', it was later shown to be a distinct animal. The genus contains one species, ''T. lecontei''.

References

Agassizodontidae Permian cartilaginous fish Mississippian first appearances Lopingian genus extinctions {{paleo-holocephalan-stub