Rare fossils expand evolutionary history of sperm whales

sperm whale skull

This skull belonged to an extinct species of pygmy sperm whale dubbed Nanokogia isthmia that once lived in an outer continental shelf habitat about 100 meters deep off the coast of Panama.

Velez-Juarbe et al. (CC-BY)

Long before Moby Dick scoured the seas for sailors, a pygmy sperm whale called Nanokogia isthmia scoured Panama’s coastal waters for lanternfish and squid.

Fossils from the previously unknown species were unearthed near a sea cliff on the Panamanian coast, researchers report April 29 in PLOS ONE. Sediments surrounding two well-preserved N. isthmia skulls date to around 7.5 million years ago.

Compared with modern specimens, the ancient pygmy sperm whale probably had a larger spermaceti organ, which helps sperm whales make noises and echolocate. Looking across the sperm whale family tree, the work also suggests that this organ shrunk twice in the animal’s evolutionary history. Sperm whale fossils are rare, and it’s unclear what may have driven the shrinkage.

Nanokogia isthmia skulls show evidence of a larger spermaceti organ than that found in modern dwarf and pygmy sperm whales, lending insight into how the organ may have evolved across the sperm whale family tree. Natural History Museum of Los Angeles County
Helen Thompson

Helen Thompson is the associate digital editor. She has undergraduate degrees in biology and English from Trinity University and a master’s degree in science writing from Johns Hopkins University.

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