he Lower Jurassic. From this point, India is usually shown as traveling northward largely in isolation, finally colliding with the Asian continent during the lower Miocene sedimentation. The author shows that this scenario based on geophysical interpretations is not consistent with paleobiogeographical evidence. India does not show evidence of an endemic fauna or flora, but shows fossil similarities with other continents. The author supplies maps showing his interpretation of the evidence as indicating India made contact with Asia during Eocene sedimentation.
Comment.The conflict between interpretations based on geophysical vs paleobiogeographical evidence remains an unsolved problem for plate tectonic theory.
Smithson TR. 1989. The earliest known reptile. Nature 342:676-678.
Summary. A nearly complete, articulated skeleton of a four-legged reptile has been recovered from the black shale member of the East Kirkton Limestone in Scotland. The skeleton is about 8 inches in length. Classification has not yet been completed, but it is neither a synapsid nor a diapsid.
Comment. The fossil was discovered by a private collector, and controversy has arisen over the proposed sale of the fossil for nearly $350,000.
Mount JF. 1989. Re-evaluation of unconformities separating the “Ediacaran” and Cambrian systems, South Australia. Palaios 4:366-373.
Summary. The top of the proposed Ediacaran stratotype in the Flinders Ranges of South Australia was previously believed located at a regional unconformity. Reinterpretation suggests it is an abrupt facies change instead, and that the Ediacaran System stratotype may actually lie well within the Lower Cambrian.
RAPID CHANGE IN BIRDS
Diamond J, Pimm SL, Gilpin ME, LeCroy M. 1989. Rapid evolution of character displacement in myzomelid honeyeaters. American Naturalist 134:675-708.
Summary. A volcanic explosion, probably about four centuries ago, destroyed all life on Long Island, an island about 50 km off the northeastern coast of New Guinea. Long Island and two nearby islands have been repopulated by a bird fauna different from that of other islands in the area which were not depopulated by the volcanic activity. The difference in species composition has apparently affected the body sizes of two species of honeyeaters.
Nine cases are known in which two species of the same genus are found living on the same newly populated island. In only one of these nine cases the two species do not occur together on any other island. In only this case individuals from Long Island differ in size as compared to individuals from other islands where the two species do not coexist. The larger species has increased in size on Long Island, while the smaller species has decreased in size. This appears to be a case of character displacement, in which size has changed in response to competition pressures, preventing one species from out-competing and eliminating the other species from the island. This change could not have taken longer than four centuries, and might have taken much less time.
RAPID CHANGE IN INSECTS
Mallet J. 1989. The evolution of insecticide resistance: have the insects won? Trends in Evolution and Ecology 4:336-340.
Summary. Resistance of insects to chemical pesticides has developed rapidly. Mechanisms of resistance include adaptations that increase behavioral avoidance, reduce cuticle permeability, increase the rate of destruction of insecticide molecules, and decrease sensitivity to the insecticide. Most of these mechanisms seem to depend on single genes, or very few genes, contrary to the expectations of neo-Darwinian theory. “Standard population genetic models have been of little use....” Mutations in regulatory genes seem more important than mutations in structural genes.
RAPID OIL FORMATION
Didyk BM, Simoneit BRT. 1989. Hydrothermal oil of Guaymas Basin and implications for petroleum formation mechanisms. Nature 342:65-69.
Summary. Oil being released in association with hydrothermal vent activity in the Gulf of California has been radiocarbon dated at less than 5000 years. The oil has similar 