Notiolofos

Lore & Background

Notiolofos was originally named in 2006 by Bond et al. as Notolophus arquinotiensis, based on a few fossil teeth. However, the name Notolophus was already in use by a genus of moths, so the genus name was changed to Notiolofos by Bond et al. in 2009. The second species, Notiolofos regueroi, was named in 2017 by Gelfo, Lopéz & Santillana, based on a single fossil molar.

Fossils of N. arquinotiensis have been found in multiple layers of the La Meseta Formation of Seymour Island, Antarctica, dated from 55 to 34 million years ago. N. regueroi is only known from the Cucullaea I layer from the Upper Ypresian, dating to 53 million years ago. When Notiolofos lived, Antarctica was still connected to South America by a land bridge, as a remnant of the supercontinent Gondwana.

N. regueroi was around the size of a sheep, with an estimated weight of 25 to 57 kilograms. N. arquinotiensis was much larger, with an estimated weight of 400 kilograms, around the size of a muskox, and is thought to have been a browser.

Reader's Guide

Notiolofos is significant as one of the few known Eocene mammals from Antarctica, providing direct fossil evidence of terrestrial vertebrate life on the continent before its isolation. The genus belongs to the family Sparnotheriodontidae and is most closely related to Victorlemoinea, whose fossils have been found in the Upper Paleocene and Lower Eocene of Patagonia and the Brazilian Itaboraí basin. This relationship supports the idea of faunal exchange between South America and Antarctica via the land bridge that existed during the Eocene. The size difference between the two species—N. arquinotiensis being much larger than N. regueroi—suggests ecological diversity within the genus. The discovery and naming history, including the correction of a preoccupied genus name, illustrate the careful work of taxonomic revision in paleontology. Overall, Notiolofos helps scientists understand the distribution and evolution of South American ungulates in high-latitude environments during the early Cenozoic.

Did You Know?

• Notiolofos was originally named Notolophus in 2006, but the name was changed in 2009 because Notolophus was already used for a genus of moths.
• The second species, N. regueroi, is known only from a single fossil molar found in the Cucullaea I layer dating to 53 million years ago.
• N. arquinotiensis weighed an estimated 400 kilograms, about the size of a muskox, while N. regueroi weighed 25 to 57 kilograms, about the size of a sheep.