Rich et al., 2002 (polar dinosaurs) Flashcards
In 1960, footprints from … showed that non-avian dinosaurs had once lived at … …. In the 20 years prior to this paper, more and more information about polar dinosaurs was being unearthed (and prob still is)
Spitzbergen, polar latitudes
Why was this area of dinosaur palaeontology late to develop?
Fossil remains of most polar dinosaurs are found today at high latitudes and often in remote areas. Their discovery and collection are therefore more costly and unlikely than is generally the case for comparable lower latitude fossils
Establishing exactly what the climate was like for polar latitudes when these fossils were formed is critical for the accurate interpretation of polar dinosaur finds.
It has been proposed that the … of the earth’s … axis may have been substantially different during the … era (248 to 65 Myr ago), resulting in warmer climates and more even day length at high latitudes.
However, theoretical investigations suggest that the Earth’s axis has remained much the same relative to the plane of the ….
Therefore, polar dinosaurs and their associated biota will have had to contend with the same extremes of … … through the year that characterise comparable latitudes today.
inclination, rotational, Mesozoic,
ecliptic,
day length
However, … … … at these high latitudes may have been very different to today’s.
Temperatures have been estimated in two locations that were polar in the …, when the fossils came from: southeastern … and the … … of Alaska (max temp 13C min 2-8C).
mean annual temperatures, Cretaceous, Australia, North Slope
The dinosaurs found on the North Slope closely resemble those found further south in Alberta, Canada, during the same period. However, there is a clear difference in the animals associated with them: there is a clear…
absence of remains of terrestrial cold-blooded (ectothermic) animals such as lizards and crocodilians, who make up a large part of the more southern faunas. This supports the idea that some non-avian dinosaurs were endothermic (warm-blooded)
In southeastern Australia, evidence for …, ice-wedges and other cold conditions has been found alongside the polar dinosaur fossils. It is suggested that these animals lived there when mean annual temperatures ranged between … and …
- however the diversity of … found exceeds that found in such cold environments today, an anomaly that has not been explained as of yet
permafrost, -6C, 3C (supported by analysis of oxygen isotope deposits), flora
… make up half of the dinosaur taxa in southeastern Australia. Brain … show they have enlarged optic …, suggested to be due to enhanced … …, compared to lower latitude members of the same family of dinosaurs. Evidence from their bones suggests that they were … throughout the year, suggesting that they were well-adapted to polar conditions.
Hypsilophodontids (rare in other parts of world), endocasts, lobes, visual acuity, active (bones constantly growing)
It has been suggested that North American polar dinosaurs may have occupied high latitudes…
This would likely not have been possible in Australia due to seaways in the north of the continent
only at favourable times of the year
During the early cretaceous, southeastern Australia was a … and … for terrestrial vertebrates, evidenced by the fact that various dinosaur taxa have been found in their earliest forms there, and others have been found from periods when they were extinct elsewhere in the world
nursery, refuge
The survival of … long after they became extinct elsewhere has been explained by the greater tolerance of amphibians than … to … ….
labrynthodonts, crocodilians, cold water
Exploration of … in the North Slope of Alaska, using techniques such as …, has the potential to uncover much more extensive records of polar dinosaurs, one not restricted to a single, brief, period of time.
permafrost, tunneling
