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Lystrosaurus as drawn by willemsvdmerwe on Deviant Art

Let’s escape today’s world and visit an endearing little friend from down under! This sausage-shaped creature was neither a reptile nor a mammal and it lived in what is now Antarctica. The creature’s name is Lystrosaurus, and it has been in the news recently because scientists analyzed its banded tusks and realized that it most likely hibernated during the dark times of winter.

This information is remarkable because Lystrosaurus lived in the Triassic Period–about 250 million years ago. As you might imagine, the world of a quarter of a billion years ago was very different than that of today. Not only had life just experienced the most catastrophic mass die-off in planetary history (the poorly understood end Permian mass-extinction, which ushered in the age of the dinosaurs), but the continents were all annealed together in one huge super continent, Pangea. Even though the contnents were in different places, the land which is now Antarctica was still by the South Pole.

During the time of Pangea, the world was much hotter than now, yet the axis of the Earth was not terribly different–so South Pole winters grew dark. This was a problem for Lystrosaurus, since its dentition indicates it lived on tubers, roots, and vegetation (and other things) which it grubbed up with its cute little tusks. When the world darkened every year, it became hard for lystrosaurus to find food, and so it slumbered.

Despite its dinosaur-like name, Lystrosaurus was a dicynodont therapsid, a sort of proto-mammal which flourished in the late Paleozoic and the early Mesozoic (before dinosaurs monopolized the scene).

To my eyes there is something appealing about the portly dog-sized lystrosaurus, and it amuses me to imagine it dozing through a dark foggy Pangea winter before awakening to run around gobbling up tree fern roots and weird amphibians with tombstone heads. Life has showed up in some strange and remarkable forms over the long years but certain habits and behaviors reappear again and again!

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My favorite mammals are the mighty proboscideans—elephants, mammoths, mastodons, gomphotheres, moeritheriums, and so on.  I have not written about them more because the only proboscideans we know a lot about are the elephants–and elephants are complicated—they are smart and they have human length lives of great social complexity, all of which makes them hard to write about.  Additionally elephants are tragic—their populations keep shrinking away as humankind grasps for ever more land and poachers kill the great sentient giants for their ivory.  Yet elephants still have a perilous chance to keep on living. What is even sadder than the senseless slaughter of the magnificent elephants are the other proboscideans, which have vanished one by one from earth.  Everyone knows about the woolly mammoth and Cuvieronius, the new world gomphothere, but the last non-elephant proboscideans to have died out were even more contemporary.

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The stegodons (from the extinct subfamily Stegodontinae) evolved in Southeast Asia approximately eleven and half million years ago.  They lived in large swaths of Asia throughout the Pliocene and Pleistocene epochs and they survived in Indonesia deep into the Holocene epoch. Radio-carbon dating has dated the last living stegodons to 2,150 BC.  The giants died after the pyramids were built at Giza and great cities had begun to sprout up in Mesopotamia and along the Indus valley.

Stegodons looked much like elephants—a resemblance which has caused much taxonomical confusion. Paleontologists once believed elephants descended from stegondons but It seems now that both stegodons and modern elephants descended from Gomphotheriidae (a sister group to the mammoths).   Stegodons had different molars and their tusks were so close together that their long trunks draped over the sides. There were many species of stegodons, the largest of which were among the largest of proboscideans, far more immense than today’s two elephant species.  The biggest stegodont were 4 m (13 ft) high at the shoulders and had a body length of 8 m (26 ft) which does not even count their 3 meter (10 foot) tusks!

 

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Modern humans reached Southeast Asia 50,000 years ago so we lived in proximity with the stegodons for some time before they vanished.   Certain species of stegodons reached isolated Indonesian islands where, over generations, they shrank into dwarf forms.  These tiny stegodons were hunted by Homo floresiensis, which seems to have been a dwarf species of human (although the scientific community has not reached consensus concerning the nature of Homo floresiensis).  Imagining tiny versions of humans hunting tiny versions of huge elephant-like creatures boggles the mind!  I am profoundly sorry the stegodons dwarf, giant, or otherwise could not have held on for a few more millennia.  I would love to have seen them—or by 4000 years ago were they already as the Saola is now—ever retreating from a world that did not seem to fit them?

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Odobenocetops as digitally rendered by the BBC for “Chased by Seamonsters”

This blog has featured posts concerning saber-toothed seals and saber-toothed marsupials but did you know that the oceans around South America once contained a saber-toothed whale?  Odobenocetops lived during the Pliocene era (around 2.5 to 5 million years ago).  Two similar species are known in the genus from fossils discovered in coastal Peru.  An early member of the dolphin superfamily, Odobenocetops was probably more closely related to narwhals and belgugas then to modern dolphins and killer whales.

Measuring only a little longer than 2 meters (6 feet) in length, Odobenocetops was remarkable (at least among whales) for its flexible neck–which could turn 90 degrees.  The powerful blunt snout of the endearing little whale suggests that it fed from beds of mollusks and other bottom dwelling shellfish, which it rasped from their shells with a muscular tongue.  Additionally, the  Odobenocetopsidae had echolocation abilities like modern dolphins–although probably not so amazingly precise, since the extinct whales’ echolocation melons were much smaller than those of living dolphins.

Odobenocetops feeding

Of course the most distinctive features of Odobenocetops were their long spiky teeth running parallel along their sides.  Scientists speculate that these tusks could have been used to seek food or as a sensory organ–like the narwhal’s sensitive tusk.  Perhaps male whales used their tusks to battle for females, like walruses do (although they seem awfully brittle for such battles).   Some males had uneven tusks.  The sole known skull of a male Odobenocetops leptodon features a right-hand tusk 1.2 m (4 ft.) long, while the left-hand tusk is only 25 cm (10 in.) long.  Since this is the only male O. leptodon skull currently known,  it is unclear whether such asymmetry was normal.

It is striking that the whales’ saber teeth were held next to the body and it makes one think that the whale did not execute many sharp turns.  A humorous but somewhat sad cartoon which I found unattributed on the web demonstrates the potential drawbacks of the Odobenocetops’ striking saber toothed design.

Aww…the poor whale…

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