Macrorhizodus nolfi

Macrorhizodus nolfi

Zhelezko, 1999

Common name Mackerel shark
Fossil group Sharks & Rays
Order Lamniformes
Family Lamnidae
Genus Macrorhizodus
Taxonomic status Accepted
Geological age Ypresian

Summary

Macrorhizodus nolfi was a lamnid mackerel shark and an active predatory member of the early Eocene marine fauna. Lamnids are built around high-performance swimming and pursuit predation, and the robust cutting teeth of M. nolfi are consistent with a shark hunting sizeable mobile prey.

Its dentition was suited to gripping and tearing rather than crushing. Fishes were probably the principal prey, with cephalopods and other nekton also plausible. The changing shape of the teeth around the jaw suggests a feeding apparatus in which different tooth positions contributed to capture and processing.

The species is known mainly from isolated teeth, so its exact swimming performance and body proportions cannot be measured directly. It nevertheless represents the early history of the mackerel-shark style of active open-water predation.

Quick Identification

Look for: a robust smooth-edged lamnid tooth with a triangular cutting crown, a broad root and small lateral cusplets that may be reduced or partly fused to the crown; complete basal corners are important.

Diagnostic Features

  • Anterior roots are arched and moderately thick, with rounded branches tapering distally.
  • Main crown is cutting-adapted and approaches an isosceles triangular outline in lateral and posterior files.
  • One or two pairs of small lateral cusplets may occur and are often reduced.
  • Cutting edge is normally continuous rather than interrupted between crown and accessory cusplets.
  • Root branches of lateral and posterior teeth are broad and relatively flat internally.

Fossil Details

Preservation
The reduced lateral cusplets are easily lost and root branches commonly break. Worn specimens can therefore resemble other early lamnids; species-level identification should use the complete crown-root proportions.

Similar Species

Recorded Fossil Sites

References

  • Rayner, D.; Mitchell, T.; Rayner, M. (2009). London Clay Fossils of Kent and Essex. 228 pp.. Medway Fossil and Mineral Society, Rochester, Kent View reference
  • Zhelezko, V.I.; Kozlov, V.A. (1999). Elasmobranchii and Palaeogene biostratigraphy of Transural and Central Asia. Materialy po Stratigrafii i Paleontologii Urala, 3, 324 pp.. UrO RAN, Ekaterinburg View reference
Last Reviewed
10 August 2026 Reviewed by Sam Harris