| Isurus planus Temporal range:
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|---|---|
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| Isurus planus's tooth | |
Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Division: | Selachii |
| Order: | Lamniformes |
| Family: | Lamnidae |
| Genus: | Isurus |
| Species: | †I. planus
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| Binomial name | |
| †Isurus planus | |
| Synonyms | |
Isurus planus is an extinct shark belonging to the Lamnidae family of the Miocene epoch. It has curved teeth without lateral protrusions, and aside from this, it is similar to mako shark. The tooth length of I. planus reaches up to 4.8 cm (1.9 in).1 This suggests that I. planus was a large predatory shark similar to the modern mako shark.
Description
I. planus lived throughout the entire Miocene epoch, from the earliest to the latest stage. It reached a maximum body length of about 3.2–3.6 m (10–12 ft).2
Its tooth roots are uneven in thickness and shape, with narrow builds and rounder lobes. The crowns of the lower teeth of this species are described to be more straight and identical to the lower teeth of C. hastalis.3The hooked teeth, which probably would be efficient for gripping prey, would suggest a diet of smaller and medium-sized animals.4
Paleobiology
I. planus is presumed to have preferred a diet similar to that of extant mako shark. The shape of its teeth is small, fast, and structured to catch slippery prey. This suggests that it primarily fed on small to medium-sized fish.4 It is also possible that it preyed on dolphins or pinnipeds smaller than itself.
References
References
- "Isurus planus". Shark-References. Retrieved 22 April 2026.
- Ehret, D. J.; Tennyson, A. J. D.; Richards, M. D.; Boessenecker, R. W. (2023). "First records of two mackerel shark species (Carcharodon planus comb. nov. and Carcharodon hubbelli; Lamnidae) from New Zealand". Journal of the Royal Society of New Zealand. 54 (5): 1–11. doi:10.1080/03036758.2023.2278730. PMC 11459750. PMID 39440289.
- Cocke, Joe (2002). Fossil Shark Teeth of the World: A collector's guide.
- Ciampaglio, C., Ricketts,D. Miocene Madness: Fossil Finder ID and Information Guide. Bakersfield, California. Buena Vista Museum of Natural History.