A team of British researchers has announced that they have identified the first fossilized remains of a part of a brain that came from a dinosaur that lived some 133 mya (Early Cretaceous) in what is now present day southeastern England.

What has been described as "a plain brown pebble" was discovered in 2004 by fossil hunter Jamie Hiscocks (who has also discovered a 140 myo spider's web, thought to be the world's oldest) in some of the fluvial sediments that make up the Tunbridge Wells Sandstone located between Cooden beach and the town of Bexhill-on-Sea (often simply Bexhill) in Sussex, England (84 km or 52 mi. southwest of London).

The fossil, which became exposed due to tidal erosion, drew the attention of study co-author Martin Brasier of Oxford University's Department of Earth Sciences, who asked study co-author David Norman, a dinosaur paleobiologist at Cambridge University's Department of Earth Sciences to examine it. Norman identified it as part of the endocranial cast of an iguanodontian dinosaur, a type of ornithopod dinosaur (herbivore) that could easily shift from bipedality to quadrupedality and which lived between the Late Jurassic to the late Cretaceous Period in Asia, Europe and North America.

Examination of the small fossil using a scanning electron microscopy (SEM) and imaging and computed tomography (CT) scanning revealed the preservation of detailed structures interpreted as meningeal fabrics (a membrane that enveloped and supported the brain), blood vessels (including capillaries) collagen strands and possibly adjacent, superficial cortical tissues, which have been replaced by calcium phosphate (collophane) lined by, or infilled with, microcrystalline iron carbonate (siderite).

The scans of the fossil revealed signs that the dinosaur's meninges and overall brain structure resembled those of living birds and crocodilians.

The iguanodon appears to have died in or near a swamp or bog and ended up flipped over in it so that the top of its skull was submerged in shallow, stagnant, highly acidic, low oxygen water and partially buried in the sediment at the bottom of it. "In effect, that environment pickled the upper part of the head of the animal," Norman explained. This "pickling" allowed the tissue to eventually become fossilized.

In reptiles today, the brain only takes up about half the space within the skull cavity being surrounded by a dense drainage system consisting of blood vessels and vascular chambers. The fact that the brain from this iguanodon was apparently pressed directly against the skull immediately raised the question of whether some dinosaurs had larger brains than was previously thought.

Dr. Norman urges caution and suggests that the most likely explanation for the brain being directly against the skull is that as it decayed after death gravity caused it to settle against the roof of the skull cavity, in that the head decayed upside-down, and not because dinosaur brains were bigger.

The dinosaur brain fragment was described in a special issue of the Geological Society of London honoring study co-author Martin Brasier, who died in 2014 in an auto accident






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