Sunday, 1 November 2009

The Pterosaur Brain

In 1888, Newton published the first account of a pterosaur brain exposed in a skull from the Lias at Whitby, North Yorkshire. The skull fossil had to be excavated to reveal the exposed brain more fully. Before the work, a number of casts of the original were made and one such cast is shown below.
Perhapsicephalus purdoni, National Geographic Survey, Nottingham.

The brain fossil showed the main lobes clearly and the auditory and semicircular canal structures were identified during excavation of the skull. The analysis applied to the brain by Newton suggested that the brain of the pterosaur was in many ways similar to the brain of a lizard, but in some respects it was charactaristically similar to the brain of birds. His conclusion was that pterosaurs, birds and lizards evolved from common ancestors.

In 1941, Tilly Edinger, a German physiologist, examined two distinct pterodactyl fossils where the brain was exposed. Her findings were similar to those of Newton, but with the advantage of the intervening progress of science since the earlier investigation, Edinger was able to make a more defined conclusion about structure.
Pterodactylus elegans, MCZ, No. 1505

The pterosaur fossils that Edinger worked with had been described by several earlier and well respected German scientists, though the work that they did was descriptive and comparative. This later work looked more closely at the structures and extrapolated the knowledge to a general description of the pterosaur brain for the first time.

Developments in the brains of pterosaurs show similarities with the development of the brain in birds. These changes are attributed to the requirements of flight, with a more developed optic lobe and a fissure (Vallecula Silvii) like that found in the fore brain of birds. At this point there is no evidence for the structure of the base of the pterosaur brain.

These are the two defining works on the nature of the pterosaur brain. With the advance in medical scanning techniques, the destructive analysis of pterosaur brains is a thing of the past. It is now possible in some cases, to examine the cranial cavity of a fossil by electronic means to develop an understanding of its brain anatomy.

Newton E. T., 1888, On the skull, brain and auditory organ of a new species of Pterosaurian (Scaphognathus purdoni) from the Upper Lias near Whitby, Yorkshire. Proceedings of the Royal Society, London. 43, pages 436–440.

Edinger T., 1941, The brain of Pterodactylus. American Journal of Science. 239, 665–682.

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