Friday, December 4, 2009

34ma migrations

Cavies and new world monkeys emigrated from Africa to South America (via antarctica?) 34ma.
Cavioids and New World Monkeys migrated northwards as Antarctica froze 34ma
African Rift formed 34ma
Pinwheeling Pangea
Cosmic impacts (oceanic?) on Earth and Moon 34ma

(Note that Australia separated from Antarctica 64ma, just after the Yucatan cosmic impact, deccan traps and C/K dino extinction of ~65ma) Aust. marsupials dispersed from So. America to Australia via Antarctca during late Cretaceous–early Paleocene.
La Meseta Fauna from Patagonia before early late Paleocene, other taxa arrived in early Eocene.

Fossil Land Mammal from Antarctica

1 Department of Earth Sciences, University of California, Riverside 92521
2 Institute of Polar Studies and Department of Geology, Ohio State University, Columbus 43210

A fossil land mammal, apparently the first found in Antarctica, belongs to the extinct marsupial family Polydolopidae. The fossils were recovered from rocks about 40 million years old on Seymour Island, in the northern Antarctic Peninsula. The newly discovered marsupials support theories that predicted their former presence in Antarctica and strengthen proposals that Australian marsupials perhaps originated from South American species that dispersed across Antarctica when Australia still was attached to it, prior to 56 million years ago.

A Bizarre New Family of Marsupialia (Incertae sedis) from the Early Pliocene of Northeastern Australia: Implications for the Phylogeny of Bunodont Marsupials

We consider the distributions of a number of dental characters in bunodont marsupials and argue that no North American Late Cretaceous taxa can be convincingly referred to the order Polydolopimorphia. Thus, polydolopimorphians continue to be known only from the Cenozoic of Gondwana, with no fossil evidence that their initial divergences occurred in North America

These marsupials went from S America to Antarctica, some continued on to Australia.

Did monkeys and cavies go from Africa to Antarctica to S America? The timing data does not seem to indicate that this had happened. More likely both had rafted across the narrow but widening straits which eventually became the Atlantic Ocean. Currents may have brought vegetative rafts from W Africa westward to approximately Bolivia.

Today Antarctica is compressed gravitationally by millions of tons of glacial ice, pushing the former coastlines far below todays' sea level (highly susceptible to constant erosion from the antarctic circumpolar current), leaving only former highlands and mountain ranges. Fossils from 34ma monkeys and cavioids from the former rainforests there aren't accessible except at rare uplifted areas such as offshore isles, and south Argentina.
The SOFINE project studies the 'frictional' processes that slow down the strongest current on Earth (the Antarctic Circumpolar Current, ACC) and drive the extension of the ocean's overturning circulation across the Southern Ocean. The experiment focuses on a major ACC meander (around the northern Kerguelen Plateau, southern Indian Ocean), which features as an area of intensified 'friction' and cross-ACC flow in most present theories and models of the Southern Ocean circulation.
Geological sampling and scientific drilling shows that it was emergent or under shallow water for up to 40 million years of its history. Wood fragments and coal found in Late Cretaceous sediments indicate that the plateau may have been covered with forests.
among eutherian or placental mammals, the ceboids have one of the oldest histories in South America with 26-27 million year old fossils of the primitive ceboid Branisella (3) documenting that ceboids were already established in South America during the Oligocene. Among extant eutherians, only caviomorph rodents and edentates have older documented histories in South America, the former now being represented by a 34 million year old Eocene fossil (4,5) and the latter by early Cenzoic Paleocene fossils (6)

Branisella: oldest NWM fossil, from Bolivia: As a whole, the dentition of Branisella is very similar to that of Proteopithecus from the Late Eocene of Fayum, Egypt, except in the lower canine morphology, suggesting a close phyletic relationship between them.

New fossil platyrrhines from the Pinturas Formation, southern Argentina
John G. Fleagle

Early Miocene coastal Patagonia: Primates
Two new fossil vertebrate localities are described from the Santa Cruz Formation (late early – early middle Miocene) of coastal Patagonia. They are noteworthy because they are the lowest stratigraphically of any precisely recorded in coastal Santa Cruz Province and they contain a rich fauna including many partially articulated skeletons undisturbed by collecting. Thus, they offer the potential for taphonomic analysis and paleocommunity reconstruction. The latter is particularly intriguing because the fauna document the Miocene Climatic Optimum at >51° South latitude. Together with several previously documented sites in this region, it offers a potential window into the nature of mammalian communities farther south than any other in the world during this time and documents the farthest south distribution of primates.

Radiometric dates indicate that the fossil mammals (including platyrrhine primates) occurring in the lower and middle parts of the formation may range in age from about 16·6 to younger than 13·3 Ma (million years ago) (Santacrucian and, almost certainly, Friasian land-mammal ages). This age range is somewhat younger than previous estimates, and suggests that the Pinturas faunas correlate broadly with those from the type Santa Cruz Formation
Chronology of Cenozoic primate localities in South America
Journal of Human Evolution, Volume 19, Issues 1-2, February-March 1990, Pages 7-21
Bruce J. MacFadden

The available fossil record indicates that primates have occurred in South America since the middle Tertiary. The oldest known primate-bearing locality, Salla, Bolivia, of Deseadan age, was previously thought to be about 35 myr old, or early Oligocene age. However, 12 radioisotopic dates from Salla using40K-40Ar and fission-track methods and magnetostratigraphic correlations indicate a late Oligocene age for this site. The exact level that produced the earliest-known South American primate,Branisella, lies just above a tuffaceous zone that yielded dates of 26·4 ± 1·0 and 25·1 ± 0·7 Ma. The revision of the “primate datum” in Bolivia from early to late Oligocene has ramifications for: (1) the calibration of other, younger primate-bearing localities in South America; and (2) biogeographic hypotheses concerning primate origins in light of plate tectonics. The other known Tertiary primate localities in South America are of Colhuehuapian (ca. 18–19 Ma). Santacrucian (ca. 15–18 Ma) and possible Friasian (ca. 14–15 Ma) ages. There is a major gap of some 14 myr that exists between these primate occurrences of middle Miocene age and the next younger localities, which are all late Pleistocene.

"But some lemurs, oddly enough, have only two nipples, and they're located over the pectoral muscles where we have them, but where most other mammals don't."

Which ones? If only lemurs with enlarged air sacs have one pair of pectoral nipples, that would indicate upright aquatic foraging/floating as in gorillas and apiths (sea cows), parallel convergence.

Anthropoidea: (monkeys) subset of Haplorhines have only two actual breasts, pectoral mammae which are unlike those of other mammals. And unlike lemurs, most monkeys have completely lost the ability to move their ears. Monkeys also lack the specialized sensory whiskers and the wet nose that lemurs and so many "lesser" animals have, and lost the ability to synthesize either vitamin D3 or vitamin C.

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