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Polar Dinosaurs

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Science  08 Feb 2002:
Vol. 295, Issue 5557, pp. 979-980
DOI: 10.1126/science.1068920

In 1960, footprints from Spitzbergen showed that nonavian dinosaurs had once lived at polar latitudes [HN1] (1). Initially, this intriguing find remained an essentially isolated discovery, but during the past 20 years, much information about polar dinosaurs [HN2] has been unearthed (2). The late development of knowledge in this field was largely a matter of logistics: The fossil remains of most polar dinosaurs are to be found today at high latitudes and often in remote areas (see the third figure). Their discovery and collection are, therefore, more costly than is generally the case for comparable lower latitude fossils.

Despite these drawbacks, the study of polar dinosaurs provides potentially unique insights into their physiological adaptations because they may have been exposed to extreme conditions not experienced elsewhere. These conditions cannot be assumed to have been the same as at comparable latitudes today, however. Establishing just what the climate was like in polar latitudes is critical for the accurate interpretation of polar dinosaur finds.

It has been proposed that the inclination of Earth's rotational axis [HN3] may have been substantially different during the Mesozoic Era (248 to 65 million years ago) [HN4] than it is today, resulting in warmer climates and more even day length through the year at high latitudes (3). In contrast, theoretical investigations suggest that except for the regular and well-understood variation by a few degrees that takes place on the scale of tens of thousands of years, the inclination of the Earth axis has remained much the same relative to the plane of the ecliptic (4). In the latter case, polar dinosaurs and their associated biota would have had to contend with the same extremes of day length through the year that characterize comparable latitudes today.

Mean annual temperature, on the other hand, may have been substantially different at a given polar location during the Mesozoic than at a comparable latitude today [HN5]. Past mean annual temperatures have been estimated in two areas where polar dinosaurs from the Cretaceous [HN6] (145 to 65 million years ago) have been found: southeastern Australia and the North Slope of Alaska.

For the North Slope, Parrish and Spicer have constructed a mean annual temperature curve spanning the last 35 million years of the Cretaceous based on the leaf shapes of flowering plants [HN7] (5). They inferred a maximum temperature of 13°C and a minimum temperature of 2° to 8°C. For comparison, the mean annual temperature in Portland, Oregon, is 12°C, and that in Calgary, Alberta, is 4°C.

The dinosaurs on the North Slope [HN8] closely resemble contemporaneous ones farther south in Alberta, Montana, and Wyoming, but there is a profound difference in the animals associated with them. On the North Slope, the remains of terrestrial, cold-blooded forms such as lizards and crocodilians are conspicuous by their absence. These missing components constitute a major part of the more southern faunas, supporting the idea that at least some nonavian dinosaurs were warm-blooded [HN9] (6).

In southeastern Australia, evidence for the contemporaneous presence of permafrost, ice wedges, and hummocky ground in association with dinosaur-bearing deposits during the late Early Cretaceous (105 to 115 million years ago) has been found. This suggests that these animals [HN10] lived there when mean annual temperatures ranged between -6°C and +3°C (7). Oxygen isotope studies [HN11] give a mean annual temperature of -2° ± 5°C for the same deposits (8). For comparison, the modern mean annual temperature of Fairbanks is -2.9°C. However, the diversity of the late Early Cretaceous flora in southeastern Australia and the large size of some of its trees far exceed that found in such cold environments today. It is difficult to imagine how this community functioned if the temperatures were as low as the physical indicators suggest. No convincing explanation exists as yet for this apparent anomaly.

Hypsilophodontids [HN12]—rare components of most dinosaur assemblages—make up half of the dinosaur taxa in southeastern Australia (see the first and second figure). Enlarged optic lobes on the only brain endocast (a cast of the inside of the cranium of a fossil skull) available in this family from Australia suggest that Leaellynasaura[HN13] had more pronounced visual acuity than lower latitude hypsilophodontids with existing brain endocasts. Coupled with histological evidence that their bones were constantly growing and that they were thus active throughout the year, this observation suggests that this family of dinosaurs was well adapted to polar conditions (7).

Corpse of Leallynasaura amicagraphica on an Early Cretaceous (110 million years ago) sand bar in southeastern Australia. The season is autumn, and ice has already began to encroach on a stream that would freeze over during the 3-month-long polar night.

CREDIT: PETER TRUSLER

Qantassaurus intrepidus [HN17] in an Early Cretaceous (115 million years ago) summer forest of southeastern Australia. The forest is composed of ginkgoes and conifers but lacks the variety of flowering plants found here today.

CREDIT: PETER TRUSLER

It has been suggested that North American polar dinosaurs may have occupied high latitudes only at favorable times of the year (10). However, such an annual trek would have been unlikely in southeastern Australia, particularly in the case of small, terrestrial dinosaurs like hypsilophodontids, because seaways to the north blocked the passage to lower latitudes (7).

Sites of Jurassic (208 million to 145 million years ago) and Cretaceous (145 million to 65 million years ago) polar tetrapod finds.

The base map shows the continental configuration in the late Early Cretaceous (100 million years ago). Modified from (7).

SOURCE: DRAGA GELT

During the Early Cretaceous, southeastern Australia was both a nursery and a refugium for terrestrial vertebrates. Early, if not the earliest, records of protoceratopsians, dromaeosaurids, ornithomimosaurs, and oviraptorosaurs have been found there [HN14] (7). On the other hand, allosaurids [HN15], which elsewhere became extinct 30 million years before, survived here along with “labyrinthodont” amphibians [HN16]. The survival of the labyrinthodonts long after they became extinct elsewhere has been explained by the greater tolerance of amphibians than crocodilians to cold water. Labyrinthodonts were superficially crocodile-like and may have been finally displaced by them when temperatures rose in southeastern Australia in the Early Cretaceous (11). The other chronological anomalies cannot be similarly explained by a polar habitat.

These studies in southeastern Australia and the North Slope of Alaska have yielded tantalizing glimpses of polar dinosaurs and their habitat. Elsewhere, studies of polar dinosaurs have focused on establishing what is there: Siberia; Bylot Island, the Yukon, and Northwest Territories, Canada; Talkeetna Mountains, Alaska; Beardmore Glacier, Antarctica; Antarctic Peninsula; New Zealand; and Queensland, Australia (2, 12-15). New genera have been named, but no major groups restricted to high latitudes have been recognized.

One location is particularly promising for future investigations (2, 7, 16). A well-exposed sequence of rocks running more than 100 km along the left bank of the Colville River on Alaska's North Slope spans the last 40 million years that nonavian dinosaurs existed. Exploration of this site will be facilitated when collecting techniques, in particular tunneling (7), are tailored to take advantage of the fact that these fossils are entombed in permafrost. It is there that the greatest known potential exists for recovering the most extensive record of polar dinosaurs, one that is not restricted to a single, brief period of time.

HyperNotes Related Resources on the World Wide Web

General Hypernotes

Dictionaries and Glossaries

The Academic Press Dictionary of Science and Technology includes definitions of paleontology terms.

A dinosaur and paleontology dictionary is included on the Zoom Dinosaurs Web site from Enchanted Learning.

J. Poling's Dinosauria On-line includes a dictionary and pronunciation guide.

A dinosaur dictionary and a glossary are available on the Dinosaur Database from Arts&Letters.com.

Web Collections, References, and Resource Lists

The Google Web Directory offers links to Internet resources about dinosaurs, paleontology, and paleogeography and paleoclimatology.

The BIOSIS Resource Guide for Zoology includes sections of Internet resources related to paleontology and dinosaurs.

The Earth Science Resources Web site is maintained by R. H. Cummins, School of Interdisciplinary Studies, Miami University, OH.

The Royal Tyrrell Museum, Drumheller, Alberta, Canada, provides a fossil encyclopedia.

Dino Russ's Lair, presented by R. Jacobson, Illinois State Geological Survey, offers annotated links to Internet dinosaur resources and makes available the Dinosaur Encyclopaedia.

Kuban's Paleo Place provides links to Internet resources on fossils, dinosaurs, paleontology, natural history, and related topics.

West's Geology Resources, maintained by I. West, School of Ocean and Earth Science, Southampton University, UK, includes a section of links to dinosaur information.

Dinobase is a dinosaur database maintained by the Palaeontology Research Group, Department of Earth Sciences, University of Bristol, UK. The Palaeontology Research Group provides a collection of Internet paleontology links and a brief history of dinosaur paleobiology by M. Benton.

The Dino Directory is provided by the UK Natural History Museum (NHM).

F. Bervoets' DinoData provides reference information on dinosaurs as well as links to Internet resources

T. M. Keesey's Dinosauricon provides reference pages on dinosaur species. Links to Internet resources are also provided.

Online Texts and Lecture Notes

Discovering Dinosaurs is an educational feature of Britannica.com.

The University of California Museum of Paleontology (UCMP) provides information about dinosaurs with links to Internet resources. The DinoBuzz exhibit explores current research into the biology of dinosaurs.

Zoom Dinosaurs is an online hypertext book about dinosaurs.

Walking with Dinosaurs is a presentation of BBC Online. A dinosaur fact file and glossary are provided.

P. Gore, Georgia Geoscience Online, Georgia Perimeter College, Clarkston, provides lecture notes and Web links for a course on historical geology.

R. Freeman-Lynde, Department of Geology, University of Georgia, provides chapter notes for a course on dinosaurs

D. Russell, Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, provides an online text for a course on dinosaurs.

P. Olsen, Department of Earth and Environmental Sciences and Lamont-Doherty Observatory, Columbia University, provides lecture notes for a course on dinosaurs and the history of life.

T. Holtz, Department of Geology, University of Maryland, provides lecture notes for course on dinosaurs.

S. Fitzsimons, Department of Geography, University of Otago, NZ, offers lecture notes for a course on climate change of the past.

General Reports and Articles

Palaeontologia Electronica is an online journal from Coquina Press sponsored by the Palaeontological Association, the Society of Vertebrate Paleontology, and other organizations.

Several sample articles from the Encyclopedia of Dinosaurs are made available (in Adobe Acrobat format) by the publisher Academic Press.

New Scientist presents the Rex Files of articles about dinosaurs.

The 25 June 1999 issue of Science had a review by P. Sereno titled “The evolution of dinosaurs.”

The 18 December 1998 issue of Science had an Enhanced Perspective by B. Huber titled “Tropical paradise at the Cretaceous poles?” about a report in that issue by J. A. Tarduno et al. titled “Evidence for extreme climatic warmth from Late Cretaceous arctic vertebrates.” The 27 April 2001 issue had a review by J. Zachos et al. titled “Trends, rhythms, and aberrations in global climate 65 Ma to present.”

Numbered Hypernotes

1. Spitzbergen footprints. The Palaeontological Museum, University of Oslo, provides information about the Iguanodon footprints discovered in 1960 in Svalbard (Spitzbergen); a photograph of the cast is provided. “Footprints of dinosaur in the Lower Cretaceous of Vestspitsbergen-Svalbard” by Albert F. de Lapparent was published (abstract) in the 1960 annual report of the Norwegian Polar Institute. A brief profile of de Lapparent is provided by Zoom Dinosaurs. The BBC's Walking with Dinosaurs provides information about the Iguanodon. The Dinosaurium of the Hooper Virtual Natural History Museum, presented by the Department of Earth Sciences, Carleton University, Ottawa, offers a presentation on dinosaur tracks.

2. Polar dinosaurs. The Department of Geology, University of Oulu, Finland, offers a presentation by J. Kokkonen titled “Cold-Footed Dinosaurs - Dinosaurs and Polar Climate.” New Scientist makes available an 8 April 1989 article by S. Bunney titled “Some dinosaurs liked it cold.”

3. Earth's axial inclination. B. Turcotte's Solar System Tourist Web site offers a presentation on Earth's axial tilt. The NOAA Paleoclimatology Program provides an introduction to Earth's axial tilt. The 10 December 1998 issue of Nature had a Science Update by H. Gee titled “At full tilt.”

4. The geologic time scale and the Mesozoic era. The U. S. Geological Survey (USGS) offers a presentation on geologic time. The Department of Geology and Geophysics, University of Alaska, Fairbanks, presents a geologic time scale. The Geological Society of America provides a detailed geologic time scale. UCMP provides a geologic time scale and an introduction to the Mesozoic. T. M. Keesey's Dinosauricon provides a chart of the ages of the Mesozoic and paleo-maps of continents.

5. Mesozoic climate. L. Stott, Department of Earth Sciences, University of Southern California, provides lecture notes on the Mesozoic climate for a course on climate change. The Department of Earth and Environmental Sciences, Lehigh University, makes available lecture notes on Mesozoic climate for a course on paleontological evidence for Earth evolution. R. Freeman-Lynde offers a presentation on the Mesozoic and its climate for a course on dinosaurs.

6. The Cretaceous period and its climate. Zoom Dinosaurs has a presentation on the Cretaceous. P. Gore's Georgia Geoscience Online provides an overview of the Cretaceous period for a course on historical geology. UCMP provides an introduction to the climate and tectonics of the Cretaceous period. R. Scotese's Paleomap Project has a section on climate history with presentations on Early and Late Cretaceous climate. NOAA's Paleo Perspective on Global Warming has a presentation on Cretaceous climate. The Palaeontology Research Group, University of Bristol, offers a student presentation on the Cretaceous climate and climate change. Regional Paleogeographic Views of Earth History, presented by R. Blakey, Department of Geology, Northern Arizona University, Flagstaff, includes a collection of tectonic and paleogeographic maps of the Late and Early Cretaceous.

7. Parrish and Spicer, and plants as climate indicators. R. Spicer, Palaeoenvironmental Research Group, Open University, UK, offers a presentation on plants as climatic indicators, as well as an information page about the Climate Leaf Analysis Multivariate Program (CLAMP). J. T. Parrish is in the Department of Geosciences, University of Arizona; information about the Phanerozoic Climates Research Project is provided. The UCMP Virtual Paleobotany Laboratory for a course on plant evolution includes a section on interpreting ancient climates from fossil leaves.

8. Dinosaurs of Alaska's North Slope. The National Geographic Society provides a map of Alaska. The Conservation GIS Center provides a map of Arctic Alaska and northwest Canada. The Alaska Museum of Natural History offers a presentation on Alaskan dinosaurs. ABC News makes available a feature article by L. Dye titled “Tracking Arctic dinosaurs.” The 14 October 1998 issue of the Yukon News had an article about the research of R. Gangloff titled “Dinosaurs once ruled North Slope.” The University of Alaska issued a 11 September 1998 press release titled “New evidence from dinosaur footsteps show massive herds once roamed northern Alaska.” R. Taggart, Paleontology Program, Department of Geological Sciences, Michigan State University, makes available in Adobe Acrobat format an article (from the Fall-Winter 1994 issue of Natural Science magazine) titled “Up on the Colville: The search for Arctic dinosaurs.” The Alaska Science Forum presented by the Geophysical Institute, University of Alaska, Fairbanks, presents a series of articles about dinosaurs.

9. Warm-blooded or cold-blooded? Scientific American offers an “Ask the Experts” column in response to the question “What kind of evidence could be found in the fossil record (or anywhere else) that would prove whether or not some dinosaurs were warm-blooded?” UCMP's DinoBuzz provides a presentation on warm-blooded versus cold-blooded dinosaurs. P. Olsen provides lecture notes on hot-blooded dinosaurs for a course on dinosaurs. T. Holtz offers lecture notes on warm-blooded dinosaurs for course on dinosaurs. The Web page for the third edition of History of Life by R. Cowan, Department of Geology, University of California, Davis, includes a presentation (with Internet links) about warm-blooded dinosaurs. The January 1998 issue of Fossil News had an article by L. Clos titled “Brain/body allometry in dinosaurs: Implications for endothermy.”

10. Dinosaurs of southeastern Australia. The National Geographic Society provides a map of Australia (and also). The Tourism Victoria Web site offers a collection of maps of Victoria. The USGS online publication This Dynamic Earth: The Story of Plate Tectonics includes a section titled “Polar dinosaurs in Australia?” The Australian Broadcasting Corporation's Walking with Dinosaurs Web page offers a presentation about Australian dinosaurs. The Museum Victoria offers a presentation on the dinosaurs of Victoria; an essay by T. Rich on the history of the discovery of Dinosaur Cove is also available. New Scientist makes available an 18 April 1998 article by I. Anderson titled “In from the cold” about dinosaur discoveries on the southern coast of Australia. Dann's Dinosaur Reconstructions Web site includes presentations on Australia's polar dinosaurs and the Dinosaur Cove site. Dinosaur Dreaming is a presentation about the dinosaur research of the Monash University Paleolab, Department of Earth Sciences; a fact sheet about Australian dinosaurs is provided.

11. Oxygen isotope analysis is defined in S. Baum's glossary of oceanography and the related geosciences. The NASA Goddard Institute for Space Studies makes available an article by G. Schmidt titled “Cold climates, warm climates: How can we tell past temperatures?” about oxygen isotope analysis. E. Thomas, Department of Earth and Environmental Sciences, Wesleyan University, provides lecture notes titled “Oxygen isotopes: The thermometer of the Earth” in a collection of notes on paleoceanography. W. White, Department of Earth and Atmospheric Sciences, Cornell University, provides lecture notes (in Adobe Acrobat format) for a course on isotope geochemistry; a presentation on using stable isotopes in paleoclimatology studies is included.

12. Hypsilophodontids. The glossary of the Dinosaur Database defines Hypsilophodontidae (hypsilophodonts). The Dinosaur Encyclopaedia has an entry for hypsilophodontids. Dann's Dinosaur Reconstructions Web site has a presentation on hypsilophodontids. DinoData provides a list of Hypsilophodontidae.

13. Leaellynasaura. Dann's Dinosaur Reconstructions Web site includes an image of the brain endocast of Leaellynasaura amicagraphica. Zoom Dinosaurs offers an introduction to Leaellynasaura. One of the programs (“Spirits of the ice forest”) of the BBC's Walking with Dinosaurs was about Leaellynasaua. Information about Leaellynasaura is provided in the Dinosaur Encyclopaedia, in DinoData, and in the NHM Dino Directory.

14. Types of Early Cretaceous dinosaurs found in southeastern Australia. The glossary of the Dinosaur Database has entries for Protoceratopsidae (protoceratopsians), Dromaeosauridae (dromaeosaurids), Ornithomimidae (ornithomimids), and Oviraptoridae (oviraptorid). Information about the Protoceratopsidae is provided by M. Thom's Ceratopsia Web page. UCMP provides information about ceratopsians, Dromaeosauridae, Oviraptoridae, and Ornithomimidae. The Dinosauricon has entries for Ceratopsinae, Dromaeosaurus, Ornithomimosauria, and Oviraptorosauria.

15. Allosauridae (allosaurids) is defined in the glossary of the Dinosaur Database. The Dinosaur Encyclopaedia has an entry for allosaurids. The Dinosauricon provides information about the Allosauridae.

16. Labyrinthodontia is defined in the Academic Press Dictionary of Science and Technology and in xrefer's Dictionary of Earth Sciences. The Russian Dinosaur Exposition Web site offers a presentation on Labyrinthodonts. Dinosaur Dreaming offers information about a Labyrinthodont discovered in southeastern Australia.

17. Qantassaurus intrepidus. DinoData has an entry for Qantassaurus intrepidus. Dann's Dinosaur Reconstructions Web site provides information about Qantassaurus intrepidus. Monash University issued a press release about Qantassaurus and its discovery.

18. T. H. Rich is at the Museum Victoria, Melbourne, Australia.

19. P. Vickers-Rich is in the Department of Earth Sciences, Monash University, Victoria, Australia.

20. R. A. Gangloff is at the University of Alaska Museum and in the Department of Geology and Geophysics, University of Alaska, Fairbanks.

References

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