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Pachycephalosaur

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Pachycephalosaur
Pachycephalosaur.jpg
Scientific Classification
Genera

Family: Pachycephalosauridae

  • Dracorex
  • Gravitholus
  • Micropachycephalosaurus
  • Pachycephalosaurus
  • Prenocephale
  • Sphaerotholus
  • Stegoceras
  • Stygimoloch
  • Tylocephale[1]

Family: Goyocephala

  • Goyocephale

Unranked

  • Homalocephale
  • Ornathotholus
  • Stenopelix
  • Wannanosaurus
  • Yaverlandia[2]

Pachycephalosaurs were a group of extinct dinosaurs that are best known for their large dome-shaped skull that is often surrounded by spikes. Protecting its brain was was a layer of bone 9 inches thick, although their head was only 26 inches long. Their name Pachycephalosaur means "thick-headed reptiles". It was once thought that the thick bone in their skull was used for head-butting between males[3], but some now question that view.

Fossils have been found in Asia and North America[4] including polar latitudes on the North Slope of Alaska.[5]. They were first discovered in the 1850s in southeastern Montana, USA. The type genus Pachycephalosaurus has been found only in the United States, and only skull remains have been discovered to date.[6]

Pachycephalosaurs are found in abundance in the fossil record due to the size and durability of their bones. Most creation scientist interpret the existence of such fossils to mean that the organism was alive at the time of the global flood, which is described in the Biblical book of Genesis. Furthermore because the text says that all land animals were placed on Noah's ark, if correct the dinosaur was also included in their number, and became extinct very recently.

Contents

Paleobiology

They were bipedal (walked on 2 legs) and possess bird-like hips similar to all ornithischians. They also had wide hip structures what many believe indicate they gave birth to live young rather than laying eggs like most reptiles. Although they had a relatively small brain, they were equipped with sharp eyesight and a keen sense of smell.[3]

Pachycephalosaur fossils usually consist of only portions of the frontoparietal bone that forms the distinctive dome and many remain incomplete. Therefore little is know about them, but it is believed they were either herbivorous (ate plant) or omnivorous (ate plants or animals). [4] It is not yet known specifically what they ate, but they had very small, ridged teeth. As such they could not have chewed tough, fibrous plants. It is assumed they lived on a mixed diet of leaves, seeds, fruit and insects.[6]

Dome Head

Pachycephalosaurus skull
(Dracorex hogwartsia) possibly a juvenile form of Pachycephalosaurus.

The most unique feature of the Pachycephalosaurs is their distinct dome-shaped skull, and they are classified into genera and species based primarily on differences in cranial characteristics. Early taxonomic classifications defined Pachycephalosaur based exclusively on the dome-shaped skull bone. Later the absence of this feature in some species led to the assumption that they were simply primitive varieties, and the classification was split between domed and non-domed species. However, the discovery of fully developed pachycephalosaurs with flat skulls (such as Dracorex hogwartsia) showed this distinction to be incorrect. It has recently been suggested by independent researchers that several genera (Dracorex, Stygimoloch, and Homalocephale), which have reduced or flattened skulls were simply juveniles, and probably belonged to Pachycephalosaurus and Prenocephale respectively.[4]

It has been long assumed that the skull was used primarily for head-butting during mating competitions between males,[3] similar to those of modern iguana.[7] However, several lines of evidence now call this into question including the ability of pachycephalosaurs to make their head, neck, and body horizontally straight to transmit stress during ramming. No known dinosaur can assume such a position, and the vertebrae of pachycephalosaurs show that the neck was carried in a curved configuration.[4]Some have stated that the absence of scars or other damage on fossilized Pachycephalosaurus skulls argues against this behavior,[6] but similar high-impact dominance competitions in other animals, such as bighorn sheep or musk oxen, are almost never injurious. Perhaps the most significant argument against this original view is the rounded shape of the skull, which would lessen the contacted surface area during head-butting, and result in glancing blows. Other possible uses of the reinforced skull include flank-butting (on the side), or defense against predators.[6]

Polar dinosaurs

Pachycephalosaurs were recently discovered on the North Slope of Alaska (1999). In total, eight types of dinosaurs (four herbivores and four carnivores) are now known from northern Alaska. Additionally, dinosaurs have been found throughout northern Canada from the Yukon Territory to the Queen Elizabeth Islands, as well as central Siberia, Antarctica, and on Svalbard (north of Norway). These discoveries of dinosaurs near the ‘Mesozoic’ poles or at polar latitudes are now calling into question assumptions about dinosaurs, their habitats, physiology, and extinction. Of particular concern is how they could survive the cold and the long periods of darkness. It does not appears that any of the dinosaurs were specifically adapted to polar locations, since the fossils found at high latitudes are also found at lower latitudes.[5]

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.[8]

It had previously been assumed that dinosaurs were tropical animals and cold-blooded (ectotherms), but scientists are now forced to question these assumptions and many assert that some were warm-blooded (endotherms). However, if dinosaurs were indeed warm blooded, it challenges the long held belief that their extinction was the result of a sudden climatic cooling due to meteorite or volcanic debris. It seems highly implausible that such a temperature change would affect dinosaurs capable of living in polar regions and not affect the cold-blooded reptiles that remain today. According to the U.S. Geological Survey: Paleontologists do not have the answers.[9] The following quote from the U.S. Geological Survey

Further complications for standard climate models has come from indicators that polar latitudes during the time of the dinosaurs were once much warmer than today. Cold-blooded animals that cannot survive periods of cold have been found with dinosaurs in regions that are assumed to have been within the Arctic Circle. Tropical trees, such as Swamp Cypress and Breadfruit have been found in areas that should have been at freezing temperatures. In addition, sea floor drilling samples indicate that the Arctic Ocean (which is dark for half of the year) was as warm as 15°C during the ‘Late Cretaceous’. [5]

Michael Oard, a creation scientist (meteorologist) does not believe the existence of polar region dinosaurs can be interpreted from within the secular (uniformitarian) worldview. In the 2006 issue of Journal of Creation, he put forth a hypothesis that the polar plants and animals did not live in these regions, but rather were transported there during the global flood.[5]

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References

  1. Pachycephalosauridae by Wikispecies
  2. Pachycephalosauria by Wikispecies
  3. 3.0 3.1 3.2 Gish, Duane T., Dinosaurs by Design. Green Forest, AR: Master Books, 1992. p42.
  4. 4.0 4.1 4.2 4.3 Pachycephalosauria by Wikipedia
  5. 5.0 5.1 5.2 5.3 Polar dinosaur conundrum by Michael J. Oard. Journal of Creation 20(2):6–7, August 2006.
  6. 6.0 6.1 6.2 6.3 Pachycephalosaurus by Wikipedia.
  7. Homalocephale by Wikipedia
  8. Rich, T.H., Vickers-Rich, P. and Gangloff, R.A., Polar dinosaurs, Science 295, p. 979, 2002.
  9. Polar dinosaurs in Australia? by the U.S. Geological Survey
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