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Hadrosaur

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Hadrosaur
Hadrosaurus.jpg
Scientific Classification
Genera

Subfamily: Hadrosaurinae (lacked the crest)

  • Anasazisaurus
  • Anatotitan
  • Aralosaurus
  • Brachylophosaurus
  • Edmontosaurus
  • Gryposaurus
  • Hadrosaurus
  • Kerberosaurus
  • Kritosaurus
  • Lophorhothon
  • Maiasaura
  • Naashoibitosaurus
  • Prosaurolophus
  • Saurolophus
  • Shantungosaurus
  • Tanius[1]

Subfamily: Lambeosaurinae (have a skull crest )

  • Arenysaurus
  • Barsboldia
  • Charonosaurus
  • Corythosaurus
  • Hypacrosaurus
  • Lambeosaurus
  • Nipponosaurus
  • Olorotitan
  • Parasaurolophus
  • Tsintaosaurus[2]
Hadrosaur-tree.jpg
Hadrosaur family tree

Hadrosaurs are extinct dinosaurs that are commonly called the "duck-billed dinosaurs" due to their distinctive bill-like mouth shaped similar to those possessed by many waterfowl. Their name Hadrosaur means "big lizard" which is aptly applied as some varieties reached 50 feet in length and weighted upwards of 5 tons.[3] They are perhaps best known for their varieties, such as parasaurolophus that possessed a pronounced cranial crest whose function remains mysterious.[4]

They have been found in Asia, Europe and North America,[5] but many species are poorly understood. A species from the genus Hadrosaurus was the first dinosaur found in North America (1858) from more than just isolated teeth, and in 1868 it became the first ever mounted dinosaur skeleton.[6]

Hadrosaurs 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 herbivores (plant eaters) with the front of the skull was flat and broad to form a beak that was ideal for clipping leaves.[5] They were also equipped with strong jaws and teeth designed for grinding and crushing plant parts. Their teeth were diamond shaped and they had more than any other dinosaur (up to 2000) with new teeth constantly replacing those that were old and worn out.[3] Although once thought to be semi-aquatic grazers that often fed on twigs, studies of stomach contents and teeth from several hadrosaurs suggests that they were primarily terrestrial browsers that fed largely on leaves and horsetails.[7]

Anatomy

Hip bones of the Edmontosaurus with the bird-hipped arrangement found in all Ornithischians.

Hadrosaurs were bipedal/quadrupedal (walked primarily on two legs) with powerful hind legs and the bird-like hips similar to all ornithischians. They probably only walked on all four legs when browsing for vegetation. They also possessed strong backs that were reinforced with bony rods, and bird-like feet (ornithopods).[3]

The Hadrosauridae is divided into two subfamilies (Lambeosaurinae, Hadrosaurinae). They are generally distinguished in that lambeosaurines (Lambeosaurinae) have the large cranial crests or tubes, and are smaller. The hadrosaurines (Hadrosaurinae) lack the cranial crests, and are larger.[5]

Hadrosaurinae

Edmontosaurus mummy with skin.

Edmontosaurus was one of the largest hadrosaurs, measuring about 43 feet in length and weighing 3-3.5 tons. Fossils of well preserved specimens from Wyoming USA had been buried so quickly that the flesh did not have time to decay and a perfect impression of the skin remained. From these findings it is clear that they had no armor or scaly skin for protection, but instead their skin was much like a modern gila monster. Although they lacked the head crest, they had a flap of loose skin on the top of their head that they could inflate.[8]

Lambeosaurinae

All Lambeosaurinae species have a head crest. A genus of this subfamily was named Corythosaurus ("Helmet Lizard") for its distinctive hollow, bony, crest atop its head that resembled a Corinthian soldier's helmet.[9] The head crest was more prominent in males than in females and filled with a complex system of tubes.[4] Their body measured approximately 35 feet long and up to 5 tons in weight. It had a beak, but the back of the jaws contained hundreds of small, interlocking teeth.[9]

Parasaurolophus is a little known genus. Only a few have been found and all from North America. It was about 30 feet tall and probably weighed about 5 tons. Its name means "near crested lizard" referring to its prominent and unusually long crest that extended way out behind its head.[4] It is best know for its elaborate cranial crest, which in some caused the skull to reach 5.2 ft in length (1.6 meters). Like other hadrosaurids, it was able to walk on either two legs or four. It probably preferred to forage for food on four legs, but ran on two.[10]

Head crest

Parasaurolophus head crest.

Many hypotheses have been advanced as to the function of the cranial crest, but most have been discredited.[10] The nasal passages extend into the crest, first into separate pockets in the sides, then into a single central chamber and onward into the respiratory system.[9] The most widely accepted purpose for the crest has been sound amplification. In his 1992 book Dinosaurs by Design Duane Gish said “The function of this hollow, skin-covered spike-like crest is uncertain, but perhaps it helped to amplify sound.[11] Any vocalization would travel through these elaborate chambers, and probably get amplified. Scientists speculate that they could make loud, low pitched cries. The sounds might serve to alert others to the presence of food or a potential threat from a predator.[9]

Recent CT-scanning has added further support for the theory that they served as vocal resonance chambers. The scans provided details of the shape of the mystery chambers, which are connected to the nasal passages and housed within what are often oddly-shaped bony protrusions extending above or behind the dinosaur’s head. In addition, the scans illustrated that Corythosaurus possessed a delicate inner ear that confirms that the dinosaurs could hear low-frequency calls. The researchers were also surprised to find that their brain possessed a large center associated with higher cognitive functions. It had previously been assumed by evolutionists that such capability had not yet evolved. “But now we see that they had the brain power”, said Lawrence Witmer of Ohio University. [12]

Many believe the crest might have had several functions: visual display for identifying species and sex, sound amplification for communication, and perhaps thermoregulation. Other proposed they housed specialized organs such as salt glands or olfactory tissue providing much improved sense of smell.[10] Since the hadrosaurs did not possess any protective armor like the ankylosaurs, some have suggested a defensive role. In 1991 Mace Baker stated that "the sounds they produced may have been so irritating to the other animals that they were left quite to themselves."[13] Duane Gish suggested that the crest could have housed chemical glands that allowed it to throw a combustible mixture at enemies, which would spontaneously ignite when mixed with oxygen in the air (similar to the modern-day bombardier beetle). If true, the hadrosaur may have been one of the creatures described to have possessed fire-breathing capability in dragon legends, and similar in that respect to the Biblical leviathan described in the book of Job.[14]

His snorting throws out flashes of light; his eyes are like the rays of dawn. Firebrands stream from his mouth; sparks of fire shoot out. Smoke pours from his nostrils as from a boiling pot over a fire of reeds. His breath sets coals ablaze, and flames dart from his mouth. Job 41:18-21

Polar dinosaurs

A hadrosaur tooth was recently discovered on James Ross Island, Antarctica (2000). Additionally, dinosaurs have been found throughout northern Canada from the Yukon Territory to the Queen Elizabeth Islands, as well as central Siberia, Alaska, 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.[15]. According to a recent article in the journal Science:

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.[16]

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.[17] 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’. [15]

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.[15]

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References

  1. Hadrosaurinae by Wikispecies
  2. Lambeosaurinae by Wikispecies.
  3. 3.0 3.1 3.2 Gish, Duane T., Dinosaurs by Design. Green Forest, AR: Master Books, 1992. p38.
  4. 4.0 4.1 4.2 Gish, p40.
  5. 5.0 5.1 5.2 Hadrosaurid by Wikipedia
  6. Hadrosaurus by Wikipedia.
  7. Hadrosaur diet by Wikipedia.
  8. Gish, p39
  9. 9.0 9.1 9.2 9.3 Corythosaurus by Wikipedia
  10. 10.0 10.1 10.2 Parasaurolophus by Wikipedia.
  11. Gish, p39
  12. The Call of the Hadrosaur by Brian Thomas. Daily Science Updates, Institute for Creation Research. Oct 22, 2008.
  13. Baker, M., Dinosaurs. Redding, CA: New Century Books, 1991. p95.
  14. Gish, p82
  15. 15.0 15.1 15.2 Polar dinosaur conundrum by Michael J. Oard. Journal of Creation 20(2):6–7, August 2006.
  16. Rich, T.H., Vickers-Rich, P. and Gangloff, R.A., Polar dinosaurs, Science 295, p. 979, 2002.
  17. Polar dinosaurs in Australia? by the U.S. Geological Survey

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