A heavy-bodied biped as long as the largest modern crocodile,
'slow lizard' is often thought of as having a small, narrow skull with a shallow lower
jaw, a toothless beak, rather sharp yet prosauropod-like cheek teeth, and fleshy cheek
pouches. Segnosaurus had muscular arms, and its three-fingered hands probably bore huge,
curved claws. Between its broad back and bulky belly, the pubic hip bones slanted
backwards. Other peculiarities included short, possibly webbed, feet with four clawed
toes.
Segnosaurus belongs to the-segnosaurs, an unusual group of saurischians with features
that are reminiscent of theropods, prosauropods, and ornithischlans. Few other dinosaurs
have posed greater puzzles to scientists in their attempt to build up a picture of a
particular creature's way of life.
One possibility is that Segnosaurus might have used its strong arms and hands, probably
equipped with long, sharp claws, to rake open termites' nests to feed on the insects. The
great anteater, which lives in South America today, wields its claws in this way.
Powerful arms and talons could also have served as defensive weapons. Some people
believe that Segnosaurus swam in lakes or rivers, catching fish to cat - a notion that
derives from the discovery, near a find of Segnosaurus bones, of fossil tracks preserving
a series of four-toed, web-footed imprints. Yet Segnosaurus's mouth seems ill designed for
gripping slippery water animals. Instead, it may have been an animal with a toothless
beak, ridged teeth, and roomy cheeks, well equipped for nipping off leaves and biting them
into smaller pieces. Segnosaurus's hip structure also suggests a plant diet since the
back-turned pubis would have made room for the great gut needed to digest large quantities
of low-grade plant material.
If the third possibility is true, it might make Segnosaurus into a dinosaur oddity - a
plant-eating theropod. Its jaw and hip structure would be similar to those of many
plant-eating dinosaurs, but no other theropod had these features. The limb bones indicate
that Segnosaurus might have managed only a brisk walk or a slow run. Certainly, with
longer thighs than shins, and short, broad feet, Segnosaurus would have moved around too
slowly to pursue and catch active prey in the manner of most ordinary theropods.