Posts Tagged ‘pygmy sperm whales’

Pygmy Sperm Whales of the Pliocene

May 14, 2017

The transition between the Pliocene and the Pleistocene about 2 million years ago was  marked by a major marine extinction event.  By contrast there was far less faunal turnover on land.  Many species of whales that no longer exist swam in Pliocene oceans.  Paleontologists recently analyzed fossil whale ear bones excavated from sites in Florida and North Carolina and determined at least 2 morphotypes of pygmy sperm whales occurred in the Atlantic Ocean during the Pliocene.  These specimens may represent different species or size variations within a single species.  Scientists can’t make a certain determination based on just the ear bones.  Extant bottle-nosed dolphins ( Tursiops truncatus ) occur as 2 different morphotypes in the Atlantic Ocean. Deep sea dolphins are larger and more powerful than near coastal dolphins, and dolphins living in estuaries and tidal rivers don’t even interbreed with dolphins living off the coast.  Yet, these 3 separate populations are considered the same species.  The extinct species of pygmy sperm whales may have also occupied different habitats.

The pygmy sperm whale fossils came from phosphate mines in Florida and spoil piles originating from Lee Creek Mine in North Carolina.  The Florida site is thought to yield fossils that are 5-4.7 million years old, and fossils from Lee Creek Mine are estimated to be between 4.8-3.1 million years old.  Ear bones of the larger morphotype were found at both sites, but the smaller morphotype was found exclusively in Florida.

Image result for pygmy sperm whales

Pygmy sperm whales are barely bigger than bottle-nosed dolphins.

Dwarf Sperm Whale Ear

Dwarf sperm whale ear bone.  The dwarf sperm whale is not the same species as the pygmy sperm whale.

The extant pygmy sperm whale ( Kogia breviceps ) grows to 11 feet long and feeds upon squid, octopus, and shrimp.  They release a kind of ink from their intestines when they are attacked by large sharks or killer whales.  I think this defense strategy is unknown among any other species of mammal.  Pygmy sperm whales are related to dwarf sperm whales ( K. sima ), and the more famous hero of the novel, Moby Dick ( Physeter macrocephalus ).  Like their larger cousin, pygmy sperm whales locate their prey using echolocation.

The sperm whale family had more relatives during the Pliocene, but those extinct species are so little known and so little evidence of them remains that we will probably never know what made each unique.

Reference:

Velez-Jaurbey, Jorge; A Ward, and C. Pimento

“Pygmy Sperm Whale (Odostecenti, Kogiidae) from the Pliocene of Florida and North Carolina”

Journal of Vertebrate Paleontology 2016