Kaikaifilu
Large mosasaur from Antarctica, one of the last of its kind.
Kaikaifilu is an extinct genus of large mosasaurs from the Maastrichtian stage of the Late Cretaceous, inhabiting what is now northern Antarctica. Its sole species, *K. hervei*, was formally named in 2017 based on an incomplete fossil found in the López de Bertodano Formation on Seymour Island, Antarctic Peninsula. The genus name references Coi Coi-Vilu, a reptilian ocean deity from Mapuche mythology. Initially classified within the subfamily Tylosaurinae, later observations have raised doubts about this placement due to several conflicting characteristics.
Based on the skull of *Taniwhasaurus antarcticus*, the skull of Kaikaifilu is estimated to have been 1.1–1.2 meters (43–47 inches) long. The animal likely reached a maximum body length of about 10 meters (33 feet), making it the largest mosasaur known from the Southern Hemisphere and, if its tylosaurine classification holds, one of the largest tylosaurines on record. A notable feature is its well-marked heterodont dentition—a trait rare among mosasaurs and absent in other tylosaurines. Fossil evidence indicates Kaikaifilu lived in waters that may have dropped below freezing. It was an apex predator sharing its habitat with invertebrates, fish, plesiosaurs, and other mosasaurs. Dating to the Cretaceous–Paleogene extinction event, Kaikaifilu is among the last known mosasaurs.
**Discovery and naming** The sole specimen, cataloged as SGO.PV.6509, was discovered in January 2011 by the Chilean Paleontological Expedition in the Upper Maastrichtian beds of the López de Bertodano Formation on Seymour Island. The fossil includes fragmentary skull parts, a jawbone, 30 isolated teeth, and a partial left humerus. Ontogenetic analysis indicates it came from an adult individual. A 2012 scientific chapter described the specimen, with Rodrigo A. Otero tentatively identifying it as a tylosaurine mosasaur but leaving it indeterminate. A 2015 anatomical revision confirmed it as a new genus and species, which Otero and colleagues formally described and named in 2017. The genus name *Kaikaifilu* derives from Mapudungun, referencing Coi Coi-Vilu. The specific epithet *hervei* honors Chilean geologist Francisco Hervé for his contributions to the geology of Chile and the Antarctic Peninsula.
Quick Facts
- Taxon
- Kaikaifilu hervei
Facts from the source article.
Lore & Background
The only known specimen of Kaikaifilu hervei, cataloged as SGO.PV.6509, was discovered in January 2011 by the Chilean Paleontological Expedition in the Upper Maastrichtian beds of the López de Bertodano Formation on Seymour Island. Fossil materials include fragmentary skull parts, a jawbone, 30 isolated teeth, and a partial left humerus. Ontogenetic analysis indicates the remains come from an adult individual. Preliminary descriptions in 2012 classified it as a tylosaurine but left the specimen indeterminate. A 2015 revision confirmed it as a new genus and species, formally named in 2017 by Rodrigo A. Otero and colleagues. The genus name references the Mapuche deity Coi Coi-Vilu, and the specific epithet honors Chilean geologist Francisco Hervé.
Reader's Guide
Kaikaifilu holds significance as the largest mosasaur known from the Southern Hemisphere, with an estimated body length of about 10 meters. Its skull, estimated at 1.1–1.2 meters based on Taniwhasaurus antarcticus, marks it as one of the largest tylosaurines if that classification holds. However, its attribution to Tylosaurinae is disputed: early observations placed it there, but later notes indicate several characteristics contradict that grouping, and the fragmentary nature of the fossils prevents definitive phylogenetic analysis. A distinguishing feature is its well-marked heterodont dentition, a rare trait among mosasaurs and absent in other tylosaurines. Kaikaifilu lived in waters that may have dropped below freezing and was an apex predator sharing its habitat with invertebrates, fish, plesiosaurs, and other mosasaurs. Dating to the Cretaceous–Paleogene extinction event, it is one of the last known mosasaurs, providing insight into the end-Cretaceous marine ecosystems of Antarctica.
Did You Know?
- Kaikaifilu is named after Coi Coi-Vilu, a reptilian ocean deity from Mapuche cosmology.
- Kaikaifilu had heterodont dentition, a rare trait among mosasaurs not found in other tylosaurines.
- The only known specimen was discovered in January 2011 by the Chilean Paleontological Expedition on Seymour Island.
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