Earliest Marsupial Relative Found – Sinodelphys

The Carnegie Museum announced this new finding in Science along with a team of Chinese scientists. They have named the fossil animal Sinodelphys szalayi for Chinese basal marsupial and for a mammal expert F.S. Szalay. The mouse sized animal (15 cm or 6 in.) is dated to 125 MYA and was found in the Mesozoic Yixian Formation in Lianoning (where else?). There are impressions of fur and some carbonized soft tissue. It probably weighed about one ounce and had marsupial features in the wrist, ankles, and the front teeth. It probably ate insects and worms. Its shoulders and limbs indicate that it lived in the trees and was a good climber.

Marsupials are the second most diverse groups of mammals with over 270 species (placentals have over 4,300 species). Marsupial reproduction differs from placental mammals by giving birth to very undeveloped fetuses that feed in the mother’s pouch for long periods of time. Today most marsupials live in Australia and South America. Only one, the Virginia opossum, lives in North America. During the Mesozoic marsupials evolved in Asia and North America and spread to the rest of the world after the Mesozoic ended. Previously the oldest known marsupial material (isolated teeth) was dated at 110 MYA from North America. Uzbekistan had the oldest jaw fragments at 90 MYA and the oldest complete skeleton was from Mongolia at 75 MYA. Needless to say this new specimen is extremely important because of its date and fantastic preservation.

Giant Dragonflies in News Again

The New York Times Science Times of February 3 had an article by Fountain on the giant arthropods from the Carboniferous. Many grew to a very large size in the oxygen rich atmosphere 300 MYA ending in the Permian. Arthropleura grew to 5 feet and dragonflies had a wingspan of 2 ½ feet. Scientists have been trying to explain how this could happen and there is no agreement to date. These arthropods breathed through holes called spiracles drawing air into a network of hollow tubes called tracheas that distribute it throughout the body. With 35% oxygen instead of the 21% prevalent now, their system would have been more efficient allowing greater growth. However, some do not agree thinking it could have been a lack of predators or preservational bias with small arthropods unfound yet. Some researchers have tested the high oxygen level on today’s insects and one study has found a 20% increase in the size of fruit flies over 5 generations. Some worry about the dissipation of heat from the large muscles needed for those dragonflies to fly. One newer theory suggests that the high oxygen level spurred molting. Insects typically double their weight before molting and more oxygen would help to promote the growth. And so this saga continues.

New Early Northern Shark

Sharks are believed to have originated near Laurasia so this 409 MY old specimen of Doliodus problematicus was found in Canada. That puts shark origins up for grabs again. But there are other interesting aspects brought out by this fossil. Instead of just finding dissociated teeth, they found the whole head indicating a five foot long animal that resembled the current angel shark (more like a ray). Oddly it has a pair of inch long bony spines protruding from the front of the fins, a feature seen in acanthodian fish that are considered to be more closely related to bony fish than sharks. It has 60 sharp teeth with two rows of teeth ready to move into place.

30,000 Year Old Siberian Site Found

The date of the first crossing of the Bering Strait has been debated with most believing that it occurred about 11,000 YA based upon known sites in Asia and Alaska. Now Donald Grayson of the University of Washington reports in Science that they have found a site in the river basin of the Yana that indicates human habitation carbon dated to 30,000 YA. This area was ice-free at the time and had abundant game. These people would have had easy access to North America at that time. They have found stone tools, ivory weapons, and butchered bones of bison, bear, lion, mammoth and hare. Some of the weapons resemble those also found at Clovis sites as well as some Asian and European sites. Earlier sites in North America would help to strengthen this theory.

Early Eocene Primate from China – Teilhardinia
55 MYA the earliest primates called euprimates appeared in the northern continents. A report in Jan. 1 Nature by Ni et al discuss the finding of a well preserved partial skull and jaws from China. It is a new species of Teilhardina – T. asiatica. It is the more primitive of species in the genus and indicates a common ancestor as a small diurnal predator. It has a bony ring around the eye socket, forward-rotated orbits, and a large braincase. The skull is a little over one inch long with an estimated body mass of 28 grams (almost one ounce). They have the full dentition with four premolars on each side that is the most for any primates. It was probably an insectivore. They are believed to be the precursors of the tarsiers that were large eyed nocturnal animals. The Field Museum’s Robert Martin wrote a related article where he did not agree with all their conclusions about its vision capabilities. It also has a large nerve opening in the snout thought to be for whiskers that are common in nocturnal animals. There is also the question of migration to Europe. There were geographical blocks between Asia and Europe, but the alternate would put the move through North America and them to Europe through Greenland. This is not supported by the species of Teilhardinia recorded. The early primates had to migrate to Africa where primates originated to fit current thinking. In addition it throws the diagnosis of a 55 MYA early North American primate Carpolestes in question because it differs significantly from this new find. With its large eyes and being a fruit eater may mean that it is not on the primate line but only developed some features like them.

New Orangutan Relative Found – Khoratpithecus

The evolution of orangutans has been disputed with two primary theories. Some relate it to the Lufengpithecus because of dental similarities found in South China and Thailand. Others believe that Sivapithecus from Indo-Pakistan has similar facial similarities indicating a close relationship. Now a new lower jaw from the Late Miocene (9-7 MYA) of Thailand shows characteristics that place it closer to orangutans than to other hominoids of the same time. They have named it Khoratpithecus piriyai (ape from Khorat and for a finder of the fossil). They have most of the mandible and reported it in the Jan. 29 Nature by Chaimanee et al. It is a U-shaped dental arcade widest at the large canine teeth. Other animals found in the sandpit include proboscidians, pigs, rhinos, bovids, and giraffids. They estimate it was a large animal with an estimated weight of 70-80 kg (34 pounds average) based on molar dimensions compared with modern animals. It also lived in a tropical environment more like the extant animals than the other possible relatives.

DNA Puts Snake Origins on the Ground

A study in the May 7 issue of Biology Letters by Vidal and Hedges at Penn State help to answer the snake origin debate that we know well here. The Field Museum’s Olivier Rieppel (Geology Department Chair) has been arguing that snakes came from terrestrial relatives and others have theorized an aquatic origin because of similar jaw structures of snakes, monitor lizards and mososaurs. An extensive analysis of 64 species representing all 19 families of living lizards and 17 of the 25 families of living snakes was used. They argue that if the origin were aquatic then the closest relative of the snake would be most similar to those of the closest living relative today – the Komodo Dragon. Instead the tests showed that snakes and the Komodo are not closely related. They go a step further and suggest that a terrestrial origin also help to explain the loss of limbs. A burrowing lifestyle would be easier without limbs to better fit into small openings when going after prey.

Madagascar Sloth Lemurs

Much has been done in Madagascar to learn more about the many extinct sloth lemurs or Palaeopropithecidae. Four of the 8 extinct genera of extinct lemurs are sloth lemurs with a wide range in body size from 10 kg to over 200 kg. Their closest lemur relatives are the Indri with its long hindlimbs and shorter forelimbs. This is just the opposite of the sloth lemurs with long arms and short legs. The first fossil humerus was found in 1868 was not described for decades as belonging to Palaeopropithecus. A gorilla-sized skull was named Archasoindrus. Many expeditions found many more fossils in the north, central and southwest of the island. Initially the elevated nasals and eyes led them to believe that they were aquatic. Even the limb bones indicated that until they determined that they were not lemur limb bones. New elements including wrist and anklebones that show that they had suspensory limbs and would have walked awkwardly on the ground between trees. The ancestors of sloth lemurs and indriids appear to have been leapers, hangers and climbers. The sloths then lost the leaping and the Indriids kept leaping. They are all gone now, but some may have died out only 500 years ago. As usual the arrival of humans is suspected to be the chief explanation. Careful studies of some of their bones show evidence of hunting and consumption with signs of butchering. They have not been able to date all the bones but one has been dated to 2,325 YA that is early considering that humans are believed to have arrived about 2,000 YA. The article by Godfrey & Jungers was in Evolutionary Anthropology (12:252).

          Karen Nordquist, ESCONI Paleontology Study Group