Smallest Dino Egg Reported
Although the layer of the eggs has not yet been identified, four tiny theropod eggs from the Cretaceous were found in Thailand and are being studied. Two of them contain delicate bones that will be analyzed. They were all crushed but appear to have measured 0.7 inches across which is about the size of the egg of the modern goldfinch (about 4 inches long). The eggs have 3 layers like bird eggs and knobs like dino eggs. They are also oval in shape like those of birds and other feathered dinosaurs. They were found among other bones in 2002 and 2003. The picture is from the web. (Buffetaut et al in Naturwissenschaften Sept. 13)
New Look at Ichthyostega
Jenny Clack and her associates have taken a closer look at the old fossils and some new fossils of the early Devonian tetrapod Ichthyostega. These fossils from Geenland dated to 360 MYA have helped to understand the water to land transition. But now it has a new look with changes to assist both with locomotion on land and in the water. The drawing at left from the article shows the new reconstruction (top), the old reconstruction (middle), and another early tetrapod Acanthostega. Note the structure of the vertebrae on the back. The old picture shows rear facing graduated neural spines on top of them. The new picture shows the forward vertebrae spines face backward, but the back vertebrae spines face forward, forming a cantilevered structure like a suspension bridge. This may have allowed it to move better on land helping to hold the body up. It also suggests that its movement was dorsoventral rather than lateral as believed. The front ribs are also thickened and would have made the spinal column more rigid. They are larger and would have helped protect the organs in the chest cavity on land. In addition there are elaborate ribs at the base of the tail that would have been helpful in swimming. Interestingly, this particular structure did not prove to be successful, as there have been no plausible descendents found yet. Acanthhostega lived at the same time but was about 30% smaller and was able to move the body laterally. (Ahlberg, Clack et al in Nature Vol. 437.Sept.1)
Human Brain Continues to Evolve
A University of Chicago researcher, Bruce Lahn, has been leading a team to determine if the human brain is still evolving since the chimp-human split some 6 MYA and the appearance of modern man some 200,000 YA. The study concentrates on two genes, microcephalin (timed to have occurred about 37,000 YA, a period of creative growth and now found in 70% of population) and ASPM (timed to about 5,800 YA, the time of writing and now found in 30% of people) that cause microcephaly or a reduced brain size. Because they found these in many DNA samples from around the world, they suggest that they were favored by natural selection instead of being random genetic drift. They might have provided an adaptive advantage in some brain-related functions, possibly cognitive. They plan to study modern DNA of living people to see if these appear to relate to cognitive ability. Unexpectedly they have found only 10% of the allele in some African areas and 75% in many Europeans. This may mean that the alleles may have arisen after the trip out of Africa. They believe that when modern humans evolved 200,000 YA their brain was 3 times the size of that of the chimp and that it has continued to grow through selective pressures to become smarter. These two genes work to increase the size of the brain. There are skeptics as expected. There are undoubtedly many more genes involved that have yet to be identified, but it is a good first step. In addition there is the fear that interpretation of this kind of study can lead to problems due to social and ethical issues. (Evans, Lahn et al and Mekel-Bobrov, Lahn et al in Science Vol. 309/Sept 9)
Avian Pulmonary System of Majungatholus Studied
Birds are well known for their extreme pneumatic skeletons that are part of their respiratory systems. Birds have thoracic and abdominal air sacs, lungs, and a flow through system that includes pneumatic bones. Now a new specimen of Majungatholus show that this system may have developed early in neo-theropods not closely related to birds. Pneumatic vertebrae and ribs have been reported before in non-avian theropods with foramina identical to those on the bones of modern birds. It was thought that this pneumaticity began in the skull and evolved backward through the body. This specimen shows that it did have regional patterns with specific cervical and abdominal diverticula along with the lungs. As in birds the forward part of the chest allows less movement with stronger rib articulations constrained by the sternum and pectoral girdle provide protection with enough flex to provide air flow, but the real pump is further back where the ribs are curved backward and the gastralia can help the pump action to pull the air through the air sac system. The fact that there are pneumatic sacral vertebrae indicate the presence of abdominal air sacs and their importance in the early development of pneumaticity further back in the system. This indication of flow through ventilation indicates early evolution of a system that is more similar to birds than reptiles and that is consistent with elevated metabolic rates in predatory dinosaurs. This would mean that this kind of ventilation system goes back far in the dinosaur line. (O.Connor & Claesssens in Nature Vol. 436/July 14)
New Book – “The Pterosaurs from Deep Time”
This is a beautiful new book by Dave Unwin of Humbolt University in Berlin with much of the dramatic art work by Todd Marshall. It describes in non-technical talk about the 220 MYA to 65 MYA history of these flying reptiles. Ranging from wingspans of 8 inches to 40 feet (and now maybe 60 feet!) he studies the fossils and tries to determine their relationships and behavior.
Karen Nordquist, Paleontology Study Group
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