Protolamna is an extinct genus of large mackerel shark from the Cretaceous Period.[1] Protolamna fossils indicate gigantism evolved early on in the history of lamniforms.
Fossil record
Protolamna is likely one of the most ancient lamniformes, known from as early as the Valanginian age of Early Cretaceous (ca. 140 Ma).[2] It appears to have had a cosmopolitan distribution throughout its geologic range, with fossils found on every continent except Antarctica.[2]
Paleobiology
Protolamna is known from isolated teeth, and a partial dentition associated with an articulated vertebral column.[3] Despite having small teeth (typically about 2 cm in size), from these more substantial remains, researchers have estimated a total length greater than 6 meters (20 ft).[3] This makes Protolamna the oldest-known gigantic lamniform.
From associated dermal denticles, researches have hypothesized that Protolamna was a pelagic-adapted predator that occupied near-shore environments.[3] As a slow but active swimmer with a tearing type dentition, it likely preyed on bony fishes, small sharks, squids, and crustaceans in its environment.
Species
Seven species are currently attributed to this genus, including the following:[1]
- P. borodini (Maastrichtian, New Jersey)
- P. carteri (Cenomanian, Texas)
- P. compressidens (Turonian–Coniacian, Belgium, France, Texas)
- P. gigantea (Cenomanian, Minnesota)
- P. ricaurtei (Barremian–Aptian Paja Formation, Colombia)[2]
- P. roanokeensis (Albian, Texas)
- P. sokolovi (Aptian–Albian, Russia)
References
- ^ a b Kriwet, Jürgen; Klug, Stefanie; Canudo, José I.; Cuenca-Bescos, Gloria (October 2008). “A new Early Cretaceous lamniform shark (Chondrichthyes, Neoselachii)”. Zoological Journal of the Linnean Society. 154 (2): 278–290. doi:10.1111/j.1096-3642.2008.00410.x.
- ^ a b c “A new lamniform shark Protolamna ricaurtei sp. nov. from the Lower Cretaceous of Colombia”. Cretaceous Research. 95: 336–340. 2019-03-01. doi:10.1016/j.cretres.2018.12.007. ISSN 0195-6671.
- ^ a b c “A large lamniform shark from the Aptian of Villa de Leiva (Boyacá, Colombia), based on the first Lower Cretaceous shark specimen preserving both teeth and vertebrae”. Cretaceous Research. 178 106211. 2026-02-01. doi:10.1016/j.cretres.2025.106211. ISSN 0195-6671.
Bibliography
- Carrillo Briceño, Jorge D.; Parra, Juan; Luque, Javier (2019), “A new lamniform shark Protolamna ricaurtensis sp. nov. from the Lower Cretaceous of Colombia”, Cretaceous Research, 95: 336–340, Bibcode:2019CrRes..95..336C, doi:10.1016/j.cretres.2018.12.007, retrieved 2019-03-12