Incakujira (meaning Inca whale) is a genus of rorqual whales that lived during the Late Miocene epoch in what are now the coasts of Peru, about 8 million to 7.3 million years ago. It contains two species, Incakujira anillodefuego and Incakujira fordycei, both from the Aguada de Lomas locality of the Pisco Formation. The type species, I. anillodefuego, was named and described in 2016 while the second species was described in 2024. All currently known specimens are immature, representing old calves to subadults, though already of significant size. The largest specimen of I. anillodefuego measures a total of 8.25 m (27.1 ft) while the holotype of I. fordycei, which is skeletally younger, has been estimated to have reached a total length of up to 10.47 m (34.4 ft), suggesting that the species may have been larger on average. While phylogenetic analysis suggest that Incakujira was closely related to modern rorquals, it may have differed somewhat in its preferred hunting method. The proportions of the vertebrae suggest that it was better adapted for maneuverability rather than stability while swimming, which today generally corresponds to a broader diet of both non-evasive prey (like copepods) and evasive prey such as schooling fish. Aspects of the cranial anatomy on the other hand could indicate that it was less adapt at lunge feeding as its modern relatives, with the craniomandibular articulation restricting the rotation of the mandible and therefore likely limiting the amount of water and therefore prey the animal could take in with a single gulp. Instead Incakujira may have employed a skim feeding strategy convergent with sei and right whales.
History and naming Incakujira is known from three almost completely preserved specimens belonging to two species, all found in the Pisco Formation of Peru. The first Incakujira skeleton to be found was GMNH-PV-159, a nearly complete skeleton which was recovered from the Aguada de Lomas locality by the Black Hills Institute of Geological Research in 1987. Shortly afterwards, between 1989 and 1990, Siber and Siber likewise collected fossils at Aguada de Lomas, resulting in the discovery of a further two fossil whale specimens, both similarly complete as the specimen discovered in 1987. In both instances the material was recovered with permission by the Peruvian government and ended up being sold to institutions in Japan. The Black Hills Institute remains were passed onto the Gunma Prefectural Museum of History before moving to the Gunma Museum of Natural History, while the specimens prepared by Siber and Siber were brought to the Gamagori Natural History Museum and the Kanagawa Prefectural Museum of Natural History. Though discovered a year later, the two Siber and Siber specimens would come to be described first, with Felix G. Marx and Naoki Kohno recognizing them as representing a single species they named Incakujira anillodefuego in 2016. Eight years later the specimen at the Gunma Museum of Natural History was recognized as representing a second species of the genus, named Incakujira fordycei. The name Incakujira represents a combination of the taxon's country of origin and the current whereabouts of the fossil material, as the first part of the name is derived from the Inca Empire and the Japanese kujira (鯨（クジラ）, "whale"). Similarly, the name of the type species, I. anillodefuego, references the Pacific Rim of Fire as it geographically connects Peru and Japan. The second species on the other hand, I. fordycei, takes its name from paleontologist Robert Ewan Fordyce, both for his general contribution to the study of fossil whales as well as his specific input on the specimen.
Description
Incakujira differs from other rorquals (fossil and extant) in having a less attenuated rostrum and the features of the maxilla, supraorbital, and remainder of the cranium. All currently known specimens of Incakujira are interpreted to represent immature individuals. The holotype of Incakujira fordycei is clearly not a young calf, but may represent an old calf or even a young subadult. The holotype specimen of I. anillodefuego similarly was interpreted as a subadult, albeit an older individual than the holotype of I. fordycei. Despite this, the latter is slightly larger, reaching a skull length of 2.377 m (7 ft 9.6 in) while the type of I. anillodefuego measures only 2.260 m (7 ft 5.0 in). This may suggest that individuals of Incakujira fordycei were on average larger than those of Incakujira anillodefuego. The preserved skeleton of Incakujira fordycei, which misses a few tail vertebrae reaches a length of 9.22 m (30.2 ft) and Kimura and Hasegawa estimated a total length of 10.47 m (34.4 ft). The two known specimens of Incakujira anillodefuego meanwhile measure 7.15 m (23.5 ft) and 8.25 m (27.1 ft) respectively.
Phylogeny Incakujira is a member of the family Balaenopteridae, the rorquals, which includes animals like the humpback whale and the blue whale. However the precise placement of the genus is somewhat unclear as morphological, molecular and total evidence analysis often yield contradictory results as to the internal composition of the family, sometimes resulting in the inclusion of gray whales. In their morphology-only analysis Marx and Kohno recover Incakujira as the sister taxon to a monophyletic Balaenoptera to the exclusion of gray and humpback whales, while the total-analysis places it as the sister taxon of the modern humpback whale (Megaptera novaeangliae). The authors do however note that the placement alongside Megaptera is poorly supported while the morphology-only analysis may be influenced by characters that are merely convergently evolved between forms. Following the description of the second species another phylogenetic analysis was conducted, confirming Incakujira anillodefuego and Incakujira fordycei as each others closest relatives. The analysis places them at the base of the balaenopterid crown-group, basal to Archaebalaenoptera and Balaenoptera but more derived than Megaptera.
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