Brains and Intelligence

BRAINS AND INTELLIGENCE The EQ or Encephalization Quotient is a simple way of measuring an animal's intelligence. EQ is the ratio of the brain weight of the animal to the brain weight of a "typical" animal of the same body weight. Assuming that smarter animals have larger brains to body ratios than less intelligent ones, this helps determine the relative intelligence of extinct animals. In general, warm-blooded animals (like mammals) have a higher EQ than cold-blooded ones (like reptiles and fish). Birds and mammals have brains that are about 10 times bigger than those of bony fish, amphibians, and reptiles of the same body size. The Least Intelligent Dinosaurs: The primitive dinosaurs belonging to the group sauropodomorpha (which included Massospondylus, Riojasaurus, and others) were among the least intelligent of the dinosaurs, with an EQ of about 0.05 (Hopson, 1980). Smartest Dinosaurs: The Troodontids (like Troödon) were probably the smartest dinosaurs, followed by the dromaeosaurid dinosaurs (the "raptors," which included Dromeosaurus, Velociraptor, Deinonychus, and others) had the highest EQ among the dinosaurs, about 5.8 (Hopson, 1980). The Encephalization Quotient was developed by the psychologist Harry J. Jerison in the 1970's. J. A. Hopson (a paleontologist from the University of Chicago) did further development of the EQ concept using brain casts of many dinosaurs. Hopson found that theropods (especially Troodontids) had higher EQ's than plant-eating dinosaurs. The lowest EQ's belonged to sauropods, ankylosaurs, and stegosaurids. A SECOND BRAIN? It used to be thought that the large sauropods (like Brachiosaurus and Apatosaurus) and the ornithischian Stegosaurus had a second brain. Paleontologists now realize that what they thought was a second brain was an enlargement in the spinal cord in the hip area, perhaps containing fat and nerve tissue. This nerve center may have controlled the animal's hind legs and tail and was larger than the animal's tiny brain. DINOSAUR DEFENSIVE WEAPONS AND MANEUVERS Dinosaurs were armed with built-in defensive weapons and behaviors that were used for dealing with interspecies rivalry or as protection from carnivores (meat eaters). These included: Horns, Claws, and Spikes - Many dinosaurs had deadly, knife-like protuberances that were excellent protection from being eaten (for example, Triceratops and Kentrosaurus ). Some sauropods had large thumb claws; these were especially prominent in the young and in juveniles. Large size - Some adult diplodocids (like Apatosaurus, Diplodocus, Supersaurus, etc.) and other dinosaurs were so large that only the hugest carnivores or packs of carnivores were a danger. Armored plating (bony plates fused into leathery skin) - Ankylosaurids (like Euoplocephalus, Ankylosaurus, and Sauropelta) were plated all over the tops and sides of their bodies. Even their eyelids had armor plating. Only their underbellies were unprotected. To kill an Ankylosaurid, a predator would have had to flip over a terribly heavy animal over - not an easy job. Thick, leathery skin - This would provide only a little bit of protection from predators with sharp, strong teeth like T. rex, Giganotosaurus, and Utahraptor. Head butting - Pachycephalosaurs (like Pachycephalosaurus, Stegoceras, Wannanosaurus, etc.) and other thick-skulled dinosaurs may used head butting to repel predators. It had long been thought that Pachycephalosaur's thick domes may have been used for ramming rivals during mating and dominance combat, for attracting mates, and as a last-ditch self-defense against predators. Paleontologist Mark Goodwin of the University of California at Berkeley has analyzed many pachycephalosaur skulls (including those of Pachycephalosaurus), finding no evidence of healed scars. Also, under close analysis, the thick skull bone is not rigid and solid, but porous and fragile when put under extreme pressure. ``It's time to kill the myth ... It certainly wouldn't be in their own best interests to ram heads in a fight,'' said Goodwin ``They would have killed each other, and a couple of bowling balls would hardly make good targets.'' Speed - Leaving a fight can be easier and safer than fighting. Bludgeon-like tail clubs - Ankylosaurids (like Euoplocephalus and Ankylosaurus) had bony tail-clubs that could easily have been used for defense, which would have been useful for these lumbering, plated grazers. Also, some theropods, like Shunosaurus, Omeisaurus and maybe Mamenchisaurus had tail clubs for protection. Whip-like tail - Some people believe that sauropods may have used their massive tails as a whip to lash at their attackers. This theory seems unlikely given the amount of physiological damage to tail tissue that would be caused by the sudden acceleration near the end of the tail (and the deceleration upon impact). Also, the large sauropods probably grazed on tree leaves, giving them no room to whip their tail around without hitting tree trunks and getting severe tail damage. SEXUAL DIMORPHISM It is very difficult to determine which fossils were male and which were female. Some paleontologists have theorized that the males of some species may have had larger crests, frills, or other showy structures that were used in courtship displays, mating rituals, and/or intraspecies rivalry (contests among members of the same species, like territorial disputes and mating competition), very much like many modern-day animals. The development of these structures occurs with sexual maturity, so example of juvenile fossils would have little or none of these structures. Hadrosaurs Originally, fossils very similar to Parasaurolophus but with smaller crests were thought to belong to a separate species of Parasaurolophus. A similar situation existed for Lambeosaurus and many other crested dinosaurs (the lambeosaurine duck-bills) and dome-headed dinosaurs (Pachycephalosaurs). In 1975, the Canadian paleontologist Peter Dodson showed that many of the supposedly separate species of frilled/crested dinosaurs were the females and juveniles of the species. The anatomist James A. Hopson also interpreted the crest and dome sizes as differing in males and females within a species. Ceratopsians - Many paleontologists believe that the ceratopsians (like Triceratops and Protoceratops) used their horns and frills in territorial disputes, in mating competitions and for attracting females. Pachycephalosaurs, the dome-headed hadrosaurid dinosaurs, also exhibit sexual dimorphism. The anatomist James A. Hopson realized that crest and dome size differs in the male and female of the species. DINOSAUR OFFENSIVE WEAPONS AND MANEUVERS Many dinosaurs were armed with built-in weapons that were used for killing and eating prey, for dealing with interspecies rivalry, or as protection from fellow carnivores (meat eaters). These included: Big, sharp, pointed teeth - Largest, sharp teeth of most carnivores are for tearing flesh from prey. Clawed feet - Many dinosaurs claws on feet and/or hands. Dromaeosaurids and Megaraptor had a huge retractible sickle-like claws on each foot. Grasping hands with clawed fingers - good for catching and slashing prey. Large size - Some dinosaurs, like Giganotosaurus and T. rex were so large that they were at the top of the food chain, and could eat any animal that they could catch. Speed and agility- In order to eat, a predator must catch its prey. The only surviving dinosaurs, the birds, evolved from the speedy, bird-like theropods. Modern-day birds have excellent good color vision; it is likely that the bird-like dinosaurs (advanced theropods like the coelurosaurs) also had color vision. This would have helped them find and catch their prey (just as hawks use their acute vision to spot prey). DINOSAUR REPRODUCTION Very little is known about dinosaur courtship, rivalry, pairing and mating. EGGS Dinosaurs hatched from eggs laid by females after sexual reproduction. The eggs were round or elongated and had hard, brittle shells. Internally, these eggs were similar to those of reptiles, birds and primitive mammals; they contained a membrane (called the amnion) that kept the embryo moist. Some dinosaurs cared for their eggs, others simply laid them and then abandoned them. The first fossilized dinosaur eggs found (and the biggest yet to be found) were football-shaped Hypselosaurus eggs found in France in 1869. These eggs were 1 foot (30 cm) long, 10 inches (25 cm) wide, had a volume of about half a gallon (2 liters), and may have weighed up to 15.5 pounds (7 kg). The smallest dinosaur eggs are about 1 inch across; they are from Mussaurus. Many fossilized dinosaur eggs have been found, at over 200 sites in the USA, France, Spain, Mongolia, China, Argentina, and India. Very rarely, the eggs have preserved parts of embryos in them, which can help to match an egg with a species of dinosaur. Without an embryo, it it difficult to match an egg to a dinosaur species. The embryo in an egg sheds light on dinosaur development. FOSSIL OR ORIGINAL SHELL? According to Dr. Kenneth Carpenter of the Denver Museum, most dinosaur eggshells still have the original shell, not a fossilized replica, "The slightest change in the calcite making up the shell destroys the very fine detail that can be seen with the scanning electron microscope. Amino acids have also been recovered that are very similar to those found in modern bird eggshell." RECENT FINDS About 10 large dinosaur eggs (plus 3 egg impressions) were found 1999 in southwestern France (near Albas, in the foothills of the Pyrenee Mountains). No bone fossils were found. The eggs had been buried in two layers in the sand. No one knows what type of dinosaur the eggs were. Much larger egg sites have been found nearby, in northeastern Spain near Tremp, where hundreds of thousands of eggs (of both sauropods and theropods) have been found. Other huge dinosaur eggs sites have been found in Argentina and China. NESTS Fossils of dinosaurs' burrows and nests can reveal a lot about their behavior. Nests vary from simple pits dug into the Many Maiasaura nests have been earth or sand to more complicated nests found in Montana, USA; nests, eggs, constructed with mud rims.

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