Omanoselache: a Permian shark with a disputed Triassic record

Omanoselache was erected in 2013 for shark teeth from the Wordian, a Middle Permian interval, of Oman's Khuff Formation. Later researchers applied the name to Triassic teeth, including O. halli from Lower Triassic deposits. A 2024 study of tooth replacement challenges the original classification: the Permian type species retains complete roots, unlike the root-resorbing teeth used to diagnose hybodontiforms, while rootless crowns in O. halli may support that placement. The evidence therefore spans fossils with different taxonomic implications, all part of the ancient fish catalogue.

Quick facts

A name introduced for Permian shark teeth

Martha Koot, Gilles Cuny, Andrea Tintori and Richard Twitchett named Omanoselache in 2013 while documenting a diverse shark fauna from the Wordian Khuff Formation in central-eastern Oman. The type species is O. hendersoni; the study also described O. angiolinii. Limestone samples were processed to recover small fossil elements, producing an unusually large set of isolated teeth for comparison.

The crowns have a rounded main cusp, with one or more pairs of lateral cusplets in some tooth positions. The original diagnosis also described a longitudinal crest, a strong lingual peg, vertical crista and variable openings in the root. The pattern changes along a jaw: anterior teeth are more symmetrical, while lateral teeth become asymmetrical. Such positional variation is called monognathic heterodonty and means that a single isolated tooth may not represent the full dentition.

The Permian remains occur in low-palaeolatitude carbonate deposits of the Khuff Formation. They preserve teeth and other small chondrichthyan elements, not an articulated fish. The original paper placed Omanoselache among hybodontiform sharks based on the comparative dental anatomy then available. It did not describe a body skeleton that would independently establish that placement.

A Triassic survival and a later species

In 2015, Koot and colleagues described O. halli from Lower Triassic deposits in Oman. The material included isolated teeth, dermal denticles and fin-spine fragments recovered from residues after processing limestone. Fossils came from several blocks and sections around the Oman Mountains, including Induan and Olenekian deposits. Some host rocks were redeposited as olistoliths, exotic blocks or breccias in younger strata, so the age of the fossil-bearing carbonate must be distinguished from the age of the enclosing deposit.

The new species was significant in a regional extinction context because it extended a genus already known from the Permian into the recovery interval after the end-Permian event. That occurrence is the basis for describing Omanoselache as a survivor across the boundary. It is not evidence that every named species lived continuously through the extinction, and the isolated remains do not show a direct population history.

Why the shark classification is being reconsidered

In 2024, a broad study of tooth replacement in fossil sharks argued that root resorption is a distinctive feature of hybodontiforms. Shed hybodont teeth commonly lack the root, whereas most other elasmobranch teeth are preserved with it. The author examined published descriptions and figured specimens and concluded that the Permian teeth assigned to O. hendersoni and O. angiolinii are complete, retaining roots. On that basis, he argued that those species should be excluded from Hybodontiformes.

The same study treated the Triassic record more cautiously. Most teeth referred to Triassic Omanoselache are described as broken or incomplete, so the mode of tooth shedding is not easy to assess. Some crowns of O. halli lack roots, a condition that could support a hybodontiform interpretation. The author therefore treated O. halli as an exception that may remain within the group, while questioning whether the Permian type species and all the Triassic referrals belong to one hybodont genus.

This is a significant reassessment, not yet a replacement diagnosis based on a new skeleton. The original genus was founded on a tooth sample and the Triassic names were added through later comparisons. Future work must test the similarities against root histology, crown characters and more complete specimens. Until then, “shark” is a safe broad description; “hybodontiform” should be attributed to the particular taxonomic treatment being followed.

What teeth cannot reveal about the animal

The fossils support comparisons of crown shape, tooth position and root construction. They do not provide body length, fin arrangement, colour or a measured swimming style. Fin-spine fragments from the Triassic deposits were assigned to other genera or left uncertain, rather than securely attached to Omanoselache. No named prey item or stomach content establishes what the fish ate.

Its carbonate settings were marine, and the small teeth were recovered alongside diverse shark remains. That establishes marine fossil occurrences, but a processed residue mixes tiny elements from more than one animal and does not show that all specimens shared one exact habitat or depth. A full-body illustration necessarily draws on general shark anatomy, not a preserved Omanoselache outline.

The scientific interest of this genus is therefore twofold: it records diverse Middle Permian shark teeth in Oman and provides a possible link to post-extinction Triassic faunas. At the same time, its classification exposes the limits of naming whole animals from isolated crowns. Keeping the original assignment and the later root-based challenge distinct best reflects what the fossils currently establish.

Explore related evidence in the ancient fish catalogue.