Fossil Sperm Whale Had Strikingly Uneven Skull

WHO:

Nature - The study describes *Scaphokogia huachafo*, a newly identified pygmy sperm whale species, and other members of the fossil genus *Scaphokogia*.

Nature - *Scaphokogia huachafo* is identified as the most derived species of its genus in the study’s phylogenetic analyses.

Nature - The study compares *Scaphokogia* with other odontocetes, including physeteroids, kogiids, platanistids, the walrus-like dolphin *Odobenocetops*, and the stem sperm whale *Rhaphicetus*.

WHAT:

Nature - Three-dimensional morphometric analyses found *Scaphokogia* to be the most asymmetric cetacean genus in the sample; *S. totajpe*, the smallest species in the genus, was the most extreme in the analysis of left–right premaxillary differences.

Nature - *S. huachafo* has disproportionately positioned external bony nares and premaxillary bones, a massive tubular rostrum, and a ventrally angled snout. Its rostrum angle is 31°; the reported angles are approximately 16–21° in *S. cochlearis* and 27° in *S. totajpe*.

Nature - The skull’s bone growth is pachyostotic, and the mesorostral cavity is partly ossified. The authors say these features likely shifted the animal’s centre of gravity forward.

Nature - The atlas-bearing specimen MUSM 171 allowed reconstruction of neck-joint motion: the rostrum formed a 22° ventral angle at maximum dorsal neck flexion and a 55° angle at maximum ventral flexion.

Nature - The right occipital condyle is broader and more dorsolaterally oriented; the left is larger and slightly more ventrally positioned. The atlas facets and bone are also asymmetric, suggesting a curved rather than linear joint-motion path.

Phys.org - Sperm whales and pygmy sperm whales are known for unusually shaped heads; toothed whales have asymmetrical skulls that accommodate specialized sound-production and echolocation organs.

WHERE:

Nature - *S. huachafo* is from the Pisco Formation in Peru. The study places its habitat in shallow coastal environments and discusses benthic-feeding cetaceans in the region.

WHY:

Nature - The authors propose that *Scaphokogia* was a specialized benthic feeder, using its ventrally oriented skull and pachyostotic skull surface for hydrostatic control while foraging near the seafloor.

Nature - Because *Scaphokogia* appears to lack specialized orofacial feeding structures, the authors propose it may have used distinctive echolocation adaptations to detect and acquire prey in soft substrates.

HOW:

Nature - The study used craniofacial morphometrics, phylogenetic principal-component analysis, asymmetry analysis, and reconstruction of the atlanto-occipital joint’s range of motion.

(UPDATED November 10, 2026 02:03 UTC)

A newly identified pygmy sperm whale from Peru had an exceptionally asymmetric skull, researchers found. Its heavy, downward-angled snout may have helped control buoyancy while feeding near the seafloor. Without specialized feeding structures, the whale may have used echolocation to find prey buried in soft sediment.