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The Double Dinosaur Brain Myth
Dinosaur brain expert Emily Buchholtz outlined the double brain issue in the newly-published second edition of The Complete Dinosaur. The idea stems from the work of 19th-century Yale paleontologist Othniel Charles Marsh. In an assessment of the sauropod Camarasaurus, Marsh noticed that the canal in the vertebrae over the dinosaur’s hips enlarged into an expanded canal that was larger than the cavity for the dinosaur’s brain. “This is a most suggestive fact,” he wrote, and, according to Buchholtz, in 1881 Marsh described a similar expansion in the neural canal of Stegosaurus as “a posterior braincase.”
Sauropods and stegosaurs seemed like the perfect candidates for butt brains. These huge dinosaurs seemed to have pitiful brain sizes compared to the rest of their body, and a second brain–or similar organ–could have helped coordinate their back legs and tails. Alternatively, the second brain was sometimes cast as a kind of junction box, speeding up signals from the back half of the body up to the primary brain. That is, if such an organ actually existed. As paleontologists now know, no dinosaur had a second brain.
There are two intertwined issues here. The first is that many dinosaurs had noticeable expansions of their spinal cords around their limbs–a feature that left its mark in the size of the neural canal in the vertebrae. This isn’t unusual. As biologists have discovered by studying living species, the enlargement of the spinal cord in the area around the limbs means that there was a greater amount of nervous system tissue in this area, and dinosaurs with larger expansions around the forelimb, for example, probably used their arms more often than dinosaurs without the same kind of enlargement. The expansion of the neural canal can give us some indication about dinosaur movement and behavior.
But the so-called “sacral brain” is something different. So far, this distinct kind of cavity is only seen in stegosaurs and sauropods and is different than the typical expansion of the neural canal. There was something else, other than nerves, filling that space. Frustratingly, though, we don’t really know what that something is.
At the moment, the most promising idea is that the space was similar to a feature in the hips of birds called the glycogen body. As sauropod expert Matt Wedel has pointed out, this space stores energy-rich glycogen in the hips. Perhaps this was true for the sauropods and stegosaurs, too. Again, though, we hit a snag. We don’t really know what the glycogen body does in birds–whether it helps with balance, is a storehouse for nutritious compounds that are drawn upon at specific times or something else. Even if we assume that the expansion in dinosaurs was a glycogen body, we don’t yet know what biological role the feature played. Dinosaurs didn’t have hindbrains, but the significant spaces in the hips of stegosaurs and sauropods still puzzle paleontologists.
Persistent dinosaur myths
Work on dinosaurs for
long enough and do enough engagement and outreach activities and a few myths
and misconceptions will come up again and again. For all that films like Jurassic
Park and documentaries like Planet Dinosaur helped drag the
general view of dinosaurs into the 21st century, a good number of people are
decades behind the research.
Now to be fair, I hardly expect most people to be
that interested in dinosaurs, but equally, almost everyone I come across does
have some residual interest in them and seems to at least know a bit. Keeping
up with every piece of research and new discovery is almost impossible even for
professional dinosaur researchers, but anyone who has taken a look in a decent
natural history museum, read any recent media coverage of dinosaurs or seen any
of a host of documentaries would, you'd hope, have been disabused of some ideas
that were out of date in the 1920s.
There is still much debate among palaeontologists
about some aspects of dinosaurs' lives owing to a lack of data, or data that
are inconclusive or even contradictory. However, there's much we can be certain
about, supported by lots of lines of evidence and good studies. Some of the
things listed below were rejected by the scientific community almost as soon as
they were first hypothesised but have somehow clung on in the public consciousness,
recycled endlessly by bad stereotypes, and cheap and lazy knock-off books and
media coverage.
Dinosaurs were all big
Some dinosaurs were truly colossal and many, indeed
most, dinosaurs when adult were big compared with modern terrestrial mammals.
However, there were plenty of species the size of cows, sheep, small dogs and
even those more the size of a cat or chicken. Birds aside, the smallest
dinosaurs we know of were only about 200g as adults.
They died out for; well any
of dozens of reasons except the right one.
There's an endless supply of ideas about what killed off the dinosaurs (and indeed plenty of other groups that went with them). From the obviously mad (aliens hunted them) to the impractical (they all died of diseases or mammals ate all their eggs) to the reasonable but no longer strongly supported (rise in greenhouse gasses), there's plenty of ideas out there. More than one hundred have been proposed, but the only well supported and universally accepted theory is that of an asteroid impact and subsequent global devastation.
There's an endless supply of ideas about what killed off the dinosaurs (and indeed plenty of other groups that went with them). From the obviously mad (aliens hunted them) to the impractical (they all died of diseases or mammals ate all their eggs) to the reasonable but no longer strongly supported (rise in greenhouse gasses), there's plenty of ideas out there. More than one hundred have been proposed, but the only well supported and universally accepted theory is that of an asteroid impact and subsequent global devastation.
They were stupid
I doubt many were smart, but most people seem to
regard all dinosaurs as being dumb as a bag of hammers. I think this is linked
to the idea that dinosaurs were somehow evolutionary failures and that being
dumb was part of this.
Intelligence is hard enough to quantify in living
species, let alone extinct ones, but there's evidence for things like social
behaviours and group living, parental care and the like, and a least some
dinosaurs had relatively large brains for their body size. Few might have been
intellectual titans, but not all could have really been total dunces and many
were probably much smarter than they are generally given credit for.
They were slow (or for that matter, super-fast)
The old idea of super-slow, lumbering dinosaurs
still hasn't quite died out. But they were not just colossal lizards gasping
from footstep to footstep but were instead largely active and agile animals.
The interesting counter to
this are those who took Jurassic Park a bit too literally and now think Velociraptor could
hit 60 miles an hour, or Tyrannosaurus 30mph or more, when in fact
modern analyses suggest these are gross exaggerations.
Dinosaurs dragged their tails on the ground
Obviously dating from the time when dinosaurs were
considered especially reptilian and lizard-like, dinosaurs posed with their
tails dragging still turn up to this day. The anatomy of the tail bones and
muscles alone suggest this is wrong, but the killer should be the near endless
collections of dinosaur footprints not accompanied by marks left by dragging
tails.
Sauropods lived in swamps/water
This is another idea that lasted only briefly in
scientific circles but which still appears today in books and media articles.
The giant long-necked sauropods were thought too big to survive on land and so must
have walked about while partially submerged in water – despite fairly obvious
problems such as the fact that they would float, and that if submerged that far
their lungs would collapse, and fossilised footprints show them walking on
land, and more.
Tyrannosaurus was a dedicated scavenger
A much more recent idea floated by Jack Horner,
this idea never gained much support from palaeontologists (and apparently even
Horner never really thought much of it) and it has been sunk by a number of
studies and reviews. Nevertheless, the coverage this got when it was first
suggested means that it shows up repeatedly and is fiercely clung to by some.
All dinosaurs lived in jungles/warm climates
On average, the Mesozoic Era in which the dinosaurs
lived was rather warmer than in the modern world. However, dinosaurs lived
across the world for tens of millions of years and they occupied a wide range
of ecosystems that included deserts, plains, coastlines, forests, jungles and
even high arctic environments. It wasn't just steamy rainforests and hot fetid
jungles.
Stegosaurus had two brains
Please not this one. They
just didn't. What they did have is an enlarged nerve cluster at the base of the
spine like lots of vertebrates including humans. To see just how pervasive this
myth is for dinosaurs as a whole (though poor old steggy generally gets picked
out) and how hard this idea is to kill, read this sorry tale by a
friend of mine and his interaction with TV producers and editors (starts a way
down).
There are lots of other
little things about dinosaurs that are quite capable of irritating me, but
these really are the biggies. Readers are of course quite free not to care one
jot about this and to find my frustration incomprehensible.
But part of the job of a scientist is to
communicate new research to the general public and given the interest in
dinosaurs in the media, museum attendances and the endless succession of
documentaries and books out there, it's clear that a great number of people are
interested and engaged. So it is incredible that ideas that have been disproved
a century ago are still hanging around and being actively propagated. It does a
disservice to the actual science and research, and a disservice to those who
want to learn.
Newly Discovered Dinosaur Implies Greater Prevalence of Feathers; Megalosaur Fossil Represents First Feathered Dinosaur Not Closely Related to Birds
A new species of feathered dinosaur discovered in southern Germany is further changing the perception of how predatory dinosaurs looked. The fossil of Sciurumimus albersdoerferi,which lived about 150 million years ago, provides the first evidence of feathered theropod dinosaurs that are not closely related to birds.
The fossil is described in a paper published in the Proceedings of the National Academy of Sciences on July 2.
"This is a surprising find from the cradle of feathered dinosaur work, the very formation where the first feathered dinosaur Archaeopteryx was collected over 150 years ago," said Mark Norell, chair of the Division of Palaeontology at the American Museum of Natural History and an author on the new paper along with researchers from Bayerische Staatssammlung für Paläontologie und Geologie and the Ludwig Maximilians University.
Theropods are bipedal, mostly carnivorous dinosaurs. In recent years, scientists have discovered that many extinct theropods had feathers. But this feathering has only been found in theropods that are classified as coelurosaurs, a diverse group including animals likeT. rexand birds. Sciurumimus -- identified as a megalosaur, nota coelurosaur -- is the first exception to this rule. The new species also sits deep within the evolutionary tree of theropods, much more so than coelurosaurs, meaning that the species that stem from Sciurumimus are likely to have similar characteristics.
"All of the feathered predatory dinosaurs known so far represent close relatives of birds," said palaeontologist Oliver Rauhut, of the Bayerische Staatssammlung für Paläontologie und Geologie. "Sciurumimus is much more basal within the dinosaur family tree and thus indicates that all predatory dinosaurs had feathers."
The fossil, which is of a baby Sciurumimus, was found in the limestones of northern Bavaria and preserves remains of a filamentous plumage, indicating that the whole body was covered with feathers. The genus name ofSciurumimus albersdoerferirefers to the scientific name of the tree squirrels,Sciurus, and means "squirrel-mimic"-referring to the especially bushy tail of the animal. The species name honours the private collector who made the specimen available for scientific study.
"Under ultraviolet light, remains of the skin and feathers show up as luminous patches around the skeleton," said co-author Helmut Tischlinger, from the Jura Museum Eichstatt.
Sciurumimusis not only remarkable for its feathers. The skeleton, which represents the most complete predatory dinosaur ever found in Europe, allows a rare glimpse at a young dinosaur. Apart from other known juvenile features, such as large eyes, the new find also confirmed other hypotheses.
"It has been suggested for some time that the lifestyle of predatory dinosaurs changed considerably during their growth," Rauhut said. "Sciurumimus shows a remarkable difference to adult megalosaurs in the dentition, which clearly indicates that it had a different diet."
Adult megalosaurs reached about 20 feet in length and often weighed more than a ton. They were active predators, which probably also hunted other large dinosaurs. The juvenile specimen of Sciurumimus, which was only about 28 inches in length, probably hunted insects and other small prey, as evidenced by the slender, pointed teeth in the tip of the jaws.
"Everything we find these days shows just how deep in the family tree many characteristics of modern birds go, and just how bird-like these animals were," Norell said. "At this point it will surprise no one if feather like structures were present in the ancestors of all dinosaurs.
The study was financed by the Volkswagen Foundation and the American Museum of Natural History.
