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A natural endocast of the brain of the Taung Child, a young Australopithecus africanus, with the facial portion of the skull attached

An endocast is the internal cast of a hollow object, often specifically used for an endocasts of the cranial vault.[1] Endocasts can be man-made for examining the properties of a hollow, inaccessible space, or occur naturally through fossilisation.

Cranial endocasts[edit]

Digital cranial endocast of Acrocanthosaurus, an early Cretacious theropod

Manmade casts[edit]

Endocasts of the inside of the neurocranium (braincase) are often made in paleoanthropology to study brain structures and hemispheric specialization in extinct human ancestors. While an endocast can not directly reveal brain structure,[1] it can allow scientists to gauge the size of areas of the brain situated close to the surface, notably Wernicke's and Broca's areas, responsible for interpreting and producing speech.

Traditionally, the casting material is some form of rubber or rubber-like material. The openings to the brain cavity, except for the foramen magnum, are closed, and the liquid rubber is slushed around in the empty cranial vault and then left to set. The resulting hollow sphere can then be drained of air like a balloon and pulled out through the foramen magnum.[2] Rubber endocasts like these were the standard practice until the end of the 20th century and are still used in some fields. However, scientists are increasingly utilizing computerized tomography scanning technology to create digital endocasts in order to avoid risking damage to valuable specimens.[3]

Natural endocasts[edit]

Natural (fossil) endocast of a Tyrannosaurus cranial vault, showing extensive olfactory bulb (left)

Natural cranial endocasts are also known. The famous Taung Child, the first Australopithecus found, consists of a natural endocast connected to the facial portion of the skull. It was the shape of the brain that allowed Raymond Dart to conclude that the fossil was that of a human relative rather than an extinct ape.[4]

Mammal endocasts are particularly useful as they resemble the fresh brain with the dura mater in place. Such "fossil brains" are known from several hundred different mammal species.[1] More than a hundred natural cast of the cranial vault of Bathygenys (a small merycodont) alone are known, some having identifiable features down to the major gyri.[5] A natural cranial endocast of a Tyrannosaurus brain vault is also known, showing the animal had limited intelligence, but a well-developed sense of smell.[6] The oldest known natural cranial endocast is a fossil fish brain from a Holocephalan, some 300 million years old.[7]

Endocasts of other hollows[edit]

Endocast of the shell of an Ordovician straight-shelled cephalopod, showing the internal shell structure

Endocasts fossils from animals with shells that easily disintegrate or dissolve, like the aragonite shells of certain molluscs and the tests of sea urchins can often be encountered free from their mold fossil. A frequent form is the internal mold of brachiopods and bivalves. In the quite symmetrical genus brachiopod Pentamerus the endocast resembles a vulva, giving these fossils the name Schamstein or Mutterstein ("shame stone" og "Mother stone") in German, while some bivalve endocasts are traditionally known as heart-of-stone or bull hearts in Britain.[8] The "Venus of Svinesund", a early mesolithic Venus figurine from Norway is a re-worked ordovician bivalve endocast.[9] Endocasts are also known from snail shells and sea urchins, and even from the stomach hollow of jellyfish, a group that rarely leave fossil traces.

Man-made endocasts are sometimes made from blood vessels for medical or anatomical reasons. The blood vessel of an organ (e.g. brain or liver) is injected with a resin. When it is set, the organ itself is dissolved, leaving a three-dimensional image of the blood supply to the organ.

References[edit]

  1. ^ a b c Jerison, H.J. "Paleoneurology: The study of brain endocasts of extinct vertebrates". Comparative Mammalian Brain Collection. University of Wisconsin, Michigan State University, National Museum of Health and Medicine, sponsored by the National Science Foundation. Retrieved 17 November 2011. 
  2. ^ McGowan, Christopher (1991). Dinosaurs, spitfires, and sea dragons (Compl. rev. and updated version of "The successful dragons" ed.). Cambridge, Mass.: Harvard University Press. ISBN 0-674-20769-6. 
  3. ^ Brett-Surman, edited by M. K.; Buchholtz, E.; Jr., Thomas R. Holtz; director, James O. Farlow; Bob Walters, art. The complete dinosaur (2nd ed.). Bloomington, Ind.: Indiana University Press. pp. 191–208. ISBN 978-0-253-00849-7. 
  4. ^ Brain, C.K. Raymond Dart and our African Origins, in A Century of Nature: Twenty-One Discoveries that Changed Science and the World, Laura Garwin and Tim Lincoln, eds.
  5. ^ Wilson, J.A. (1971). "Early Tertiary vertebrate faunas, Vieja Group: Trans- Pecos Texas: Agriochoeridae and Merycoidodontidae". Texas Memorial Museum Bulletin (18): 1–83. 
  6. ^ Australian museum: Tyrannosaurus rex brain
  7. ^ Oldest Fossil Brain Find Is 'Really Bizarre', LiveScience.com
  8. ^ von Werfring, Johan (2015-05-21). "Schamstein-Therapie nach Krötenbiss". Museumsstücke, ProgrammPunkte (Wiener Zeitung). Retrieved 30 July 2015. 
  9. ^ Glørstad, Håkon; Nakrem, Hans Arne; Ørhaug, Vanja (November 2004). "Nature in society: reflections over a Mesolithic sculpture of a fossilised shell". Norwegian Archaeological Review 37 (2): 95–110. doi:10.1080/00293650410014960. 

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Endocast — Please support Wikipedia.
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82 news items

Science /AAAS

Science /AAAS
Fri, 26 Jun 2015 14:33:45 -0700

Now, using computerized tomography (CT) scanning, researchers have created a 3D digital reconstruction of Hauffiopteryx's skull, making a “ghost image” of its brain known as a digital endocast (above). The team, which reported its findings online ...

Ancient Origins

Ancient Origins
Tue, 21 Jul 2015 19:57:04 -0700

A reconstructed Zhoukoudian skull (A) and endocast (B: superior view; C: left lateral view; D: anterior view; E: posterior view). Public Domain. “The evidence this time is more convincing. It has been found under the earth untouched, without weather ...
 
PLoS Blogs (blog)
Thu, 04 Dec 2014 09:37:30 -0800

Digital endocast and interpretive drawing of the endocast from Rhinodipterus. The front of the brain is on the right, and the back (spinal cord) is at the left. The inner ear region is shown in orange, the hindbrain (including base of the spinal cord ...

Ancient Origins

Ancient Origins
Fri, 13 Mar 2015 15:34:45 -0700

A reconstructed Zhoukoudian skull (A) and endocast (B: superior view; C: left lateral view; D: anterior view; E: posterior view). Public Domain. The tooth, partial skulls, and many other ancient fossils and tools were excavated from a site at ...

Popular Archaeology

Popular Archaeology
Thu, 22 Jan 2015 11:12:15 -0800

Researchers have come across ancient anatomical evidence that suggests that Australopithecus africanus, a hominin species thought to be an ancestor of humans, sported hands capable of making and using stone tools, a capability until now reserved only ...

LiveScience.com

LiveScience.com
Mon, 25 Aug 2014 12:04:56 -0700

The fossil, which is thought to be roughly 3 million to 4 million years old, is a well-preserved cast of the inside of the cranium, known as an endocast. It was the first known fossil of Australopithecus africanus, an extinct close hominid relative of ...

Scientific American (blog)

Scientific American (blog)
Thu, 04 Apr 2013 06:04:57 -0700

Thibaut Bienvenu of the Collège de France and his colleagues reconstructed Toumaï's endocast—a cast of the interior of the braincase, which reveals the shape of the brain. Because the fossil skull is distorted and filled with a highly mineralized ...

Laboratory Equipment

Laboratory Equipment
Thu, 18 Sep 2014 04:03:06 -0700

A: Using the high resolution CT image data, we have reconstructed the endocast of the Taung Child. It is the first time a reconstruction has been made from high resolution images. We are comparing its surface morphology to the surface morphology of ...
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