Pachycephalosaurus Name

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Pachycephalosaurus Name

Scientists classify living things, including animals, using a hierarchical system of names. The lowest two levels in this system are the Genus (which refers to a closely related group of animals), and the Species (animals so closely related that they can breed and produce fertile offspring). The Genus and Species are often used in combination to identify a particular animal (this is known as the "Scientific Name" or "Binomen") of the animal. This system of naming animals is known as "Binomial nomenclature".

Logical and simple though the name system is, the story of how Pachycephalosaurus got its name is a long and complicated one with many twists and turns. This is partly because early fossils were not always correctly identified as belonging to the animal, and partly because of mistakes made in identifying how the specimens were related to previously known dinosaurs. In the end, the mess was only cleared up when 1985 when Donald Baird successfully campaigned for the adoption of the name "Pachycephalosaurus" regardless of the fact the usual rules for zoological nomenclature would not allow it!

The modern story of Pachycephalosaurus begins in the 19th century, when fossils of the animal were found, but their origin remained uncertain. In 1872, Joseph Leidy identified the then-known fossils as belonging to the armor of a reptile or an armadillo-like animal (more than a century later these turned out to be a bone from the knobs on Pachycephalosaurus's skull).

Joseph Leidy:
Joseph Leidy

The earliest name used to refer to the animal appears to be "Tylosteus", although exactly which animal it described was vague and perhaps a little uncertain (this is one reason why Baird was able to bypass the normal rules of zoological nomenclature more than a century later).

In 1931, Charles W. Gilmore examined the fossils, and incorrectly thought they belonged to a member of the Genus . He therefore suggested the name Troodon wyomingensis (Troodon from Wyoming).

Charles W. Gilmore:
Charles W. Gilmore

In 1945, Barnum Brown and Erich Maren Schlaikjer, using newer and more complete specimens, established the Genus Pachycephalosaurus. They identified two species: Pachycephalosaurus reinheimeri and Pachycephalosaurus grangeri (although neither are generally recognized as distinct species today).

Barnum Brown:
Barnum Brown

In 1985, Donald Baird successfully campaigned to get the officially recognized name of the Genus to be "Pachycephalosaurus", even though the normal rules of zoological nomenclature would dictate "Tylosteus". As a result of this the only species generally recognized today is Pachycephalosaurus wyomingensis - combining the names chosen by Charles W. Gilmore and Barnum Brown
  • "Pachycephalosaurus" means "thick-headed lizard" from the Ancient Greek words "pachys" (thick), "kephale" (head), and "sauros" (lizard).

  • Wyomingensis means from Wyoming. This was chosen by Charles W. Gilmore since he incorrectly believed the fossils to have originated in that state. It was more than 50 years later that Donald Baird was actually able to trace their true origin to Montana.

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