Antarctic Dinosaur Paleobiology: Inferences from Paleobotany and Climate

Antarctic dinosaurs including those from Australia have been portrayed as having to live in an environment where freezing temperatures were a possibility. This notion is contrary to data from fossil wood that has been collected from the Antarctic Peninsula from Cretaceous to Paleocene. This wood has yet to show any evidence of frost rings, indicating unexpected cold periods during the growing season that cause damage to plant cells, which are typical of modern trees even in temperate latitudes, were not present in the Cretaceous of greater Antarctica. Tree ring data also indicate that the growth period ends abruptly each year presumably due to decreasing light availability. As most species of Cretaceous Antarctic plants are evergreen, browse for herbivorous dinosaurs would be available year-round, thus the ecosystem would not shut down during the long polar nights, but would be a time of a maintenance-only phase, with growth for both plants and dinosaurs occurring in the summertime with the warmer long polar days. Adaptations of both nocturnal and high latitude lizards living today, would serve as good physiological analogs for polar dinosaurs having to live during the dark, yet not cold, polar winters. These nocturnal lizards compensate for living at temperatures below their optimal temperatures by employing low costs of locomotion, and by having their energy-dependent activity less sensitive to environmental temperatures, both of which do not require biochemical adaptations. Thus Antarctic dinosaurs could easily function during the long nights but would wait for the better thermal regimes of the summer to put on additional growth, which would parallel what is happening with the plants. This hypothesis would preclude dinosaurs having to seasonally migrate out of the high latitude regions due to the onset of polar winters as has been suggested elsewhere.