Tag Archives: dinosaurs

Ginormous, or The Canseco Conjecture

35.9-33.9 million years ago

The Eocene epoch, which we leave behind, saw super-greenhouse conditions, and tropical forests extending to high latitudes. The Oligocene, starting 34 million years ago, sees a drop in atmospheric COlevels. Glaciers begin forming in Antarctica, and the world cools sharply. There are extinctions in a number of groups (although not on the scale of the Big Five mass extinctions), after which the fauna, at least in Eurasia/North America, starts looking like what we’re used to: versions of horses, deer, camels, elephants, cats, dogs, and many rodent families begin to dominate.

The Oligocene also boasts also the largest land mammal of all time, Indricotherium (or Baluchitherium, discovered 1922), related to living rhinoceroses, but 15 feet high at the shoulders, and weighing as much as three or four African elephants. (The picture below compares them.) Indricotherium was big enough to browse high up on trees. By contrast, living big browsers (giraffes, elephants) use special bits of anatomy (long necks, trunks) to reach that high, and don’t get quite as big.indricotherium

This is still a lot smaller than the biggest dinosaurs, the sauropods. Ginormousness is one of the things dinosaurs are famous for, even though there were plenty of small dinosaurs too. Two things that keep mammals from getting truly huge are probably (1) a different respiratory system, without the extensive airsacs and aerated bones of dinosaurs, and (2) live birth. Gigantic sauropods could lay eggs and produce (relatively) small offspring which grew up quickly, so they didn’t pay as high a reproductive penalty for being big.

There are other possibilities. Jose Canseco, former Major League Baseball player, and authority on being large (he is the author of Juiced: Wild Times, Rampant ‘Roids, Smash Hits, and How Baseball Got Big), published his theory on Twitter in 2013 (February 17-18). “My theory is the core of the planet shifted when [a] single continent formed to keep us in a balanced spin. The land was farther away from the core and had much less gravity so bigness could develop and dominate.” Anticipating possible criticism, he tweeted, “I may not be 100% right but think about it. How else could 30 foot leather birds fly?”

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The last of (most of) the dinosaurs

The end-Cretaceous extinction isn’t the biggest ever, but it’s the one everybody knows about. The Disney movie Fantasia (1940) did a version of the event, set to Stravinsky (and mixing up Jurassic and Cretaceous dinosaurs). In Terence Malik’s movie The Tree of Life, a predatory dinosaur discovers compassion in an encounter with a hadrosaur just before all their kind are wiped out by an asteroid: mass extinction meets the Book of Job.

The discovery that dinosaurs (and about 70% of all species in total) probably went extinct as a result of an extraterrestrial impact did more than anything else to bolster catastrophism. For most of the history of modern geology, geologists have mostly argued instead for uniformitarianism: the same slow processes we see today caused past geological and evolutionary changes. When evidence for an impact was first discovered – a thin layer of iridium, presumably extraterrestrial — paleontologists were pretty uniformly hostile: no physicist was going to tell them how to do science. But by now the evidence is overwhelming that the asteroid impact that left the Chixculub crater, in what is now the Yucatan, was largely responsible for the end-Cretaceous extinctions (although the volcanic eruptions that created the Deccan traps in India may also have played a role).

But at the same time that evidence has increasingly vindicated the catastrophist position, new discoveries in paleontology have increasingly brought home that one group of dinosaurs survived the extinction. Most people think of birds and dinosaurs as two quite distinct kinds of animal. But birds are just as much dinosaurs as bats are mammals. Many dinosaurs had many of the distinctive features of birds – warm-bloodedness and high metabolic rates (probably), wishbones, an advanced respiratory system, feathers (sometimes brightly colored, sometimes used for courtship), and parental care for nests of eggs and juveniles. It’s even possible that some flightless dinosaurs, like the turkey-sized Caudipteryx, were secondarily flightless, descended from flying ancestors like Archeopteryx. We don’t have to hope for The Lost World or Jurassic Park to come true to see living dinosaurs; a trip to the park, with The Sibley Guide to Birds in hand, will do it.

Leaves of grass

Not as dramatic as the evolution of Triceratops, Tarchea giganta, or T. rex, but of more lasting consequence, is the evolution of grasses (Poaceae). We know from coprolites – fossil feces — that grass was around by the Late Cretaceous, so the coevolution of grass and grazers had already begun with dinosaurs. These early grasses were not widespread. It would take climate shifts and more evolution (toward using carbon dioxide more efficiently) to create the sort of grasslands we are familiar with.

Grasses have played a central role in human evolution and human history. Human beings evolved in tropical grasslands, and some evolutionary psychologists think we still have an instinctive affinity for this environment. The domestication of grasses (wheat, barley, oats, millet, rice, corn) was one of the great revolutions in human prehistory, and grasses provided most of the calories people ate for most of recorded history. Contact along the frontier between grasslands supporting pastoralists and grain growing lands supporting peasants is one of the great engines of historical dynamics.

Grasses grow from the base of the leaf, not the tip of the stem, which is what allows them to recover from being grazed. This makes them a recurring symbol both of the transitoriness of life (“All flesh is grass, and all the goodliness thereof is like the flower of the field,” Isaiah 40:6) and its resilience.

The most famous poem about grass, by Walt Whitman, perhaps strikes the right elegiac note for the dinosaurs, who meet their doom tomorrow:

A child said, What is the grass? fetching it to me
with full hands;
How could I answer the child?. . . .I do not know what it
is any more than he.

I guess it must be the flag of my disposition, out of hopeful
green stuff woven.
Or I guess it is the handkerchief of the Lord,
A scented gift and remembrancer designedly dropped,
Bearing the owner’s name someway in the corners, that we
may see and remark, and say Whose?

Or I guess the grass is itself a child. . . .the produced babe
of the vegetation.

Or I guess it is a uniform hieroglyphic,
And it means, Sprouting alike in broad zones and narrow
zones,
Growing among black folks as among white,
Kanuck, Tuckahoe, Congressman, Cuff, I give them the
same, I receive them the same.

And now it seems to me the beautiful uncut hair of graves.
Tenderly will I use you curling grass,
It may be you transpire from the breasts of young men,
It may be if I had known them I would have loved them;
It may be you are from old people and from women, and
from offspring taken soon out of their mother’s laps,
And here you are the mother’s laps.

This grass is very dark to be from the white heads of old
mothers,
Darker than the colorless beards of old men,
Dark to come from under the faint red roofs of mouths.

O I perceive after all so many uttering tongues!
And I perceive they do not come from the roofs of mouths
for nothing.

I wish I could translate the hints about the dead young men
and women,
And the hints about old men and mothers, and the offspring
taken soon out of their laps.

What do you think has become of the young and old men?
What do you think has become of the women and
children?

They are alive and well somewhere;
The smallest sprouts show there is really no death,
And if ever there was it led forward life, and does not wait
at the end to arrest it,
And ceased the moment life appeared.

All goes onward and outward. . . .and nothing collapses,
And to die is different from what any one supposed, and
luckier.

Griffinoceratops

Blog about dinosaurs and you also end up blogging about the great age of dinosaur discovery that began almost 200 years ago. But dinosaurs hunting didn’t begin with the Victorians. Adrienne Mayor wrote a great book called The First Fossil Hunters, about how many of the monsters of ancient Greek and Roman myth were based on the discovery of the bones of extinct species, from mammoths (likely basis for the legend of Cyclops) to dinosaurs.

The griffin is a fine example. The Greeks from the 7th century BCE picked up stories from the Scythian nomads of the Eurasian steppe about griffins far to the east who guarded treasures of gold. These griffins were supposed to be “four-legged birds” with feathers, wings, eagle-like beaks, and clawed feet. The legendary homeland of the griffins was explored in 1922 by the great fossil-hunting expedition of Ray Chapman Andrews, which discovered abundant remains of the late Cretaceous (about 83 million years ago) Protoceratops, along with dinosaur eggs. The resemblance to the legendary griffins is striking.

griffinceratops copy

Mayor argues that Scythian discoveries of ceratopsian skeletons inspired the story of the griffin. The main difference is the griffin’s wings, which might have been a misreading of ceratopsian collar bones. Remarkably, the ancient idea of the griffin is close to recent reconstructions of feathered agile dinosaurs. The word “dinosaur” literally means “terrible lizard,” but many dinosaurs really were closer to “four-legged birds.”

Archaeopteryx, Bird, Fish, Snake

The first Archaeopteryx discovered, found in 1861, is the most famous fossil ever (barring maybe some close human relations). It came at the right time, providing dramatic evidence for the theory of evolution.

archaeopteryx

There may be psychological reasons why Archaeopteryx had the impact it did. Here’s my argument anyway:

According to Jorge Luis Borges, the following is a classification of animals found in a Chinese Encyclopedia, the Celestial Emporium of Benevolent Knowledge.

  • Those that belong to the Emperor
  • Embalmed ones
  • Those that are trained
  • Suckling pigs
  • Mermaids (or Sirens)
  • Fabulous ones
  • Stray dogs
  • Those that are included in this classification
  • Those that tremble as if they were mad
  • Innumerable ones
  • Those drawn with a very fine camel hair brush
  • Et cetera
  • Those that have just broken a flower vase
  • Those that, at a distance, resemble flies

Although some scholars have taken this list seriously (Hi, Michel Foucault!), there’s no evidence that this is anything but a Borgesian joke. Anthropologists have actually spent a lot of time investigating the principles underlying native categorizations of living things, and found they are not nearly as off-the-wall as Borges’ list. These categorizations obey some general principles, not quite the same as modern biologists follow, but not irrational either. (Naming Nature: The Clash Between Instinct and Science is good popular review of ethno-biology, the branch of anthropology that studies different cultures’ theories of biology and systems of classification Did you know there are specialized brain areas that handle animal taxonomy? Or try here for a scholarly treatment.)

At the highest level is usually a distinction between plants and animals. This doesn’t necessarily match the biologists’ distinction between Plantae and Animalia, but rather usually follows a distinction between things that don’t and do move under their own power. Even babies seem to make a big distinction between shapes on a screen that get passively pushed around, and shapes that move on their own. i.e. are animated.

Among larger animals (non-bugs/worms) the first large scale groups to receive a label of their own are almost always birds, fish, and snakes, in no particular order. These categories are telling: each represents a variety of locomotion (flying, swimming, slithering) other than the stereotypical mammalian walking/running. (Many folk classifications lump bats with birds and whales with fish, and they may also separate flightless birds like the cassowary from others.) So whether a creature moves on its own, and how it moves are central to folk categorizations of living kinds, even if not to modern scientific taxonomy. And so finding an animal that seems to be a missing link between two (psychologically) major domains of life — birds and terrestrial animals — is going to be a Big Deal, cognitively, upsetting people’s ideas that it takes God’s miraculous intervention to create animals that fly, or to condemn the Serpent to slither.

The People of the Wind

163-154 million years ago

John W. Campbell, the editor of Astounding Science Fiction magazine, used to challenge writers with new premises. One of his challenges was to imagine an alien that is to mammals as mammals are to reptiles. Science fiction writer Poul Anderson took up this challenge by inventing the Ythri, flying intelligent aliens of the planet Avalon, for his novel The People of the Wind. The Ythri were able to support the high metabolisms necessary for flight because they had a special system for supercharging their bloodstreams with extra oxygen.

Since Anderson’s time, we’ve learned that birds – and some dinosaurs – are actually somewhat Ythri-like. To begin with, consider non-dinosaur reptiles, like lizards: their sprawling posture means that their legs compress and expand their lungs as they run, so they can’t run and breathe at the same time. (David Carrier, a biologist at the University of Utah, was a main guy to figure this out.) If you had traveled back in time to the Paleozoic, before the dinosaurs took over, and if you had good endurance training, you would have found the hunting easy, because the sprawling reptiles of the time would not have been able to run away for more than a short sprints. The predators to worry about would have been ambush hunters, not endurance hunters.

Dinosaurs got around these constraints in the first place by running bipedally (although some later reverted to quadrupedalism). And it now looks like at least some of them also had the sort of respiration we find in birds. Lungs are only part of birds’ respiratory systems. Birds also have an extensive network of air sacs running through their bodies, and even air passages in their bones. Air moves in both directions, in and out, like a bellows, through the air sacs, but only one direction through the lungs. This allows for more efficient circulation than mammalian lungs, where air has to move both in and out of the lungs. Just recently (2008), it’s been shown that Allosaurus, only distantly related to birds, had the same system, so it was probably widespread among dinosaurs. This breathing system may have helped dinosaurs to survive low-oxygen crises at the end of the Triassic, and flourish in the low oxygen Jurassic and Cretaceous. It may also have helped one group of dinosaurs to evolve into birds.

Anderson’s book isn’t just about respiratory physiology. It’s also about perennial issues of loyalty and identity. Avalon also has human settlers, who have so absorbed Ythri values — some of them even yearning, impossibly, to be Ythri — that they fight for an independent Avalon against an expanding Terran Empire. (Compare the movie Avatar.)

We’ll have more to say about bipedalism and breathing — and language — when human evolution comes up.

Ginormous, or The Canseco Conjecture

The Eocene epoch, which we leave behind, saw super-greenhouse conditions, and tropical forests extending to high latitudes. The Oligocene, starting 34 million years ago, sees a drop in atmospheric CO2 levels. Glaciers begin forming in Antarctica, and the world cools sharply. There are extinctions in a number of groups (although not on the scale of the Big Five mass extinctions), after which the fauna, at least in Eurasia/North America, starts looking like what we’re used to: versions of horses, deer, camels, elephants, cats, dogs, and many rodent families begin to dominate.

The Oligocene also boasts also the largest land mammal of all time, Indricotherium (or Baluchitherium, discovered 1922), related to living rhinoceroses, but 15 feet high at the shoulders, and weighing as much as three or four African elephants. (The picture below compares them.) Indricotherium was big enough to browse high up on trees. By contrast, living big browsers (giraffes, elephants) use special bits of anatomy (long necks, trunks) to reach that high, and don’t get quite as big.indricotherium

This is still a lot smaller than the biggest dinosaurs, the sauropods. Ginormousness is one of the things dinosaurs are famous for, even though there were plenty of small dinosaurs too. Two things that keep mammals from getting truly huge are probably (1) a different respiratory system, without the extensive airsacs and aerated bones of dinosaurs, and (2) live birth. Gigantic sauropods could lay eggs and produce (relatively) small offspring which grew up quickly, so they didn’t pay as high a reproductive penalty for being big.

There are other possibilities. Jose Canseco, former Major League Baseball player, and authority on being large (he is the author of Juiced: Wild Times, Rampant ‘Roids, Smash Hits, and How Baseball Got Big), published his theory on Twitter in 2013 (February 17-18). “My theory is the core of the planet shifted when [a] single continent formed to keep us in a balanced spin. The land was farther away from the core and had much less gravity so bigness could develop and dominate.” Anticipating possible criticism, he tweeted, “I may not be 100% right but think about it. How else could 30 foot leather birds fly?”

http://phenomena.nationalgeographic.com/2013/02/25/dinosaur-reproduction-not-ancient-gravity-made-sauropods-super-sized/