Serratolamna: a Cretaceous shark known from distinctive teeth

Serratolamna was a lamniform shark whose fossil record consists chiefly of teeth. The best-known species, S. serrata, is recognised by an asymmetrical crown with small divergent cusplets along the shoulders. Its story spans an early nineteenth-century species name, a genus erected in 1991, and later records from Cretaceous deposits in Cuba and Egypt. The teeth are distinctive, but they do not reveal a complete body. Serratolamna is one of the sharks represented in the ancient fish catalogue.

Quick facts

From Lamna serrata to Serratolamna

Louis Agassiz described the species now called Serratolamna serrata in 1843, originally using the name Lamna serrata. Landemaine erected the genus Serratolamna in 1991 for a distinctive set of fossil lamniform teeth. Historical literature contains several combinations and names as palaeontologists compared isolated crowns with those of other sharks. The naming trail is a record of changing classification, not evidence that the animal itself changed.

The teeth are commonly asymmetric, with a principal cusp and small divergent cusplets on the shoulders. Specimens described from the Fox Hills Formation are noted for smooth crown faces and a characteristic arrangement of multiple cusplets. The exact outline differs with the tooth's position in the jaw: front, lateral, and rear teeth in one shark can look unlike one another. This positional variation matters when researchers sort isolated fossils into species.

What the teeth reveal: what they do not

Tooth shape supports identification as a lamniform shark and suggests a predatory feeding apparatus. It does not provide a reliable whole-body length unless teeth can be associated with a jaw or a well-calibrated set of related measurements. Nor does the word “mackerel shark” establish a modern-style swimming speed or a precise prey list.

Most named material is isolated teeth. Scattered vertebrae and associated remains may broaden the anatomical record, but a tooth and a vertebra from one formation are not automatically from the same individual or even the same genus. Associations need evidence such as close articulation, matching size and preservation, or repeated co-occurrence in a well-understood deposit.

The family assignment has also varied. Some classifications place the genus in Serratolamnidae, while others treat the relationships more cautiously. A family name is a hypothesis about shared ancestry, tested with characters and comparison to other lamniforms. A single recognisable tooth pattern can support a genus assignment without resolving every branch of the shark tree.

Late Cretaceous records across ancient seas

S. serrata is reported from Late Cretaceous marine deposits, including Maastrichtian material. A study of sharks from Cuba documented a Maastrichtian tooth assigned to the species, alongside other, less diagnostic shark remains. The find broadened the documented occurrence of the species in the Caribbean region; it did not provide a complete skeleton or settle all questions about its range.

A 2026 study of the Duwi Formation at Abu-Tartur in Egypt described a diverse Late Cretaceous lamniform assemblage that includes material referred to Serratolamna. These teeth come from phosphate-bearing deposits in a region that was marine during the Cretaceous. Such records help compare shark communities across basins, but isolated fossils must be distinguished from reworked material and uncertain species-level identifications.

Tooth assemblages can preserve a detailed record of shark diversity because teeth are shed continuously and fossilise more readily than cartilage. The same strength creates a limitation: a bed may concentrate teeth from many individuals, species, and habitats. Abundance in a deposit is not a direct census of the living sea.

A careful reconstruction

A reconstruction of Serratolamna can show a lamniform body plan based on living relatives and the limited fossil anatomy. The diagnostic teeth and their cusplets are better grounded than the exact body proportions, skin pattern, or hunting behaviour. Fossils do not demonstrate a specific attack style or preferred prey species.

The secure story is that a distinctive shark lineage persisted in Cretaceous seas and left teeth that can be compared across deposits. Its nomenclature has shifted, its fossil record is geographically broad, and new assemblages continue to add occurrences. A tooth can identify an important part of that history, while the rest of the animal remains a comparative reconstruction.

Explore related evidence in the ancient fish catalogue.