Gondwanatheria

Gondwanatheria is an extinct group of mammals that lived during the Upper Cretaceous through the Eocene in the Southern Hemisphere, including Antarctica. They are known only from isolated teeth and a few lower jaws, and because of this fragmentary knowledge, their placement is not clear.

Classification

The affinities of the group are not clear, but gondwanatherians were first interpreted as early xenarthrans, or "toothless" mammals similar to the modern anteater. This is somewhat ironic, given that they were originally known only from teeth. They were also treated as members of the Multituberculata.

The latest thinking is apparently returning towards the xenarthran affinities, or something else entirely. Though generally no longer seen as multituberculates, "a few specimens described as ?Ferugliotherium," are Multituberculates (Kielan-Jaworowska & Hurum, 2001, p.411). "These poorly known specimens (not discussed herein) demonstrate that a branch of multituberculates apparently lived during the Late Cretaceous in South America."

There are two known families within Gondwanatheria. The family Sudamericidae was named by Scillato-Yané and Pascual in 1984, and includes the genera Sudamerica, Gondwanatherium and Lavanify. The family Ferugliotheriidae was named by José Bonaparte in 1986, and includes one genus, Ferugliotherium.

Further fossils have come from India and Antarctica, where gondwanatherids once lived in the lush forests of the Eocene.

Antarctica

Antarctica has more to offer than just marsupials:

"The occurrence on Seymour Island of sudamericids, that had become extinct in South America in the Paleocene, also indicates that isolation may have allowed extended survival of this Gondwanan group in the Eocene of Antarctica and the factors that caused their extinction did not affect this continent." (Reguero et al., 2002, p.189)

From the same paper, (p.203):

"For the sudamericids, Koenigswald et al. (1999) inferred a semi-aquatic and perhaps a burrowing way of life, similar to that of living beavers. Regarding this, the presence of two Antarctic taxa at Seymour Island (Goin, personal communication, 2000) suggests an important paleoecological constraint related to dietary preference of this group.”

The Antarctic peninsula of the "late Early to latest Eocene" seems to have been a lively place.

Represented by the fossils and the geological conditions of the La Meseta Formation (dated to about 40 million years ago) suggest a nearby forest populated by a diverse fauna, which had many similarities with the slightly earlier residents of Patagonia; small, arboreal, fruit and insect-eating possums, 10 kg sloths, middle-to-large sized grazers (sparnotheriodontids and Trigonostylops), falcons, ratites (big flightless birds like the rhea) and penguins. At the end of the Eocene the climate seems to have become unsuitable.

References and external links

• Z. Kielan-Jaworowska and J. H. Hurum. (2001) "Phylogeny and Systematics of multituberculate mammals". Paleontology 44, pages 389–429.
• M. A. Reguero, A. M. Sergio and S. N. Santillana. (2002) "Antarctic Peninsula and South America (Patagonia) Paleogene terrestrial faunas and environments: biogeographic relationships". Palaeogeography-Palaeoclimatology-Palaeoecology, 179, pages 189–210.
• Much of this information has been derived from MESOZOIC MAMMALS; Gondwanatheria, an Internet directory.