The Sauropodomorpha were a group of long-necked,
herbivorous dinosaurs that eventually dropped down on all fours
and became the largest animals that ever walked the earth.
Sauropodomorphs were adapted to browsing higher
than any other contemporary herbivore, giving them access to high
tree foliage. This feeding strategy is supported by many of their
defining characteristics, such as: a light, tiny skull on the
end of a long neck (with ten or more elongated cervical vertebrae)
and a counterbalancing long tail (with one to three extra sacral
vertebrae).
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The
pictures of sauropodomorphs are grouped alphabetically on
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Their teeth were weak, and shaped like leaves
or spoons (lanceolate or spatulate). Instead of grinding teeth,
they had stomach stones (gastroliths), similar to the gizzard
stones of modern birds and crocodiles, to help digest tough plant
fibers. The front of the upper mouth bends down in what may be
a beak.
The earliest known sauropodomorph, Saturnalia,
was small and slender (1.5 metres, or 5 feet long), but by the
end of the Triassic they were the largest dinosaurs of their time,
and in the Jurassic/Cretaceous they kept on growing. Ultimately
the largest sauropods like the Supersaurus, Diplodocus
hallorum, and Argentinosaurus reached 30–40
metres (100–130 ft) in length, and 60,000–100,000
kilograms (65–110 US short tons) or more in mass.
Initially bipedal, as their size increased they
evolved to become graviportal quadrupeds (like elephants). The
early sauropodomorphs were most likely omnivores as their shared
common ancestor with the other saurischian lineage (the theropods)
was a carnivore. Therefore their evolution to herbivory went hand
in hand with their increasing size and neck length.
They also had large nostrils (nares), and retained
a thumb (pollex) with a big claw which may have been used for
defense — though their primary defensive adaptation was
their extreme size.