The excavation of the palisade also revealed the body of a second infant and the skeleton of a sheep or goat.
A pile of stones had been placed over the animal's head, indicating a sacrificial burial, Pollard said.
(Related: "Stonehenge Was Cemetery First and Foremost, Study Says" [May 29, 2008].)
While it's possible the two infants were human sacrifices, more than likely they died naturally, he said.
"You're dealing with a period when infant mortality was very high, so there would have been a lot of natural death," Pollard added.
The newfound artifact "is, as far as we know, without parallel," according to Stonehenge expert Mike Pitts, editor of British Archaeology magazine.
Pitts agrees that it appears to have been "made for a child as a personal toy."
However he strongly disagrees with those who say it depicts a hedgehog.
"I would say it's without doubt a pig," said Pitts, who noted that both domestic and wild pigs were widespread in the region at the time.
Later, from the start of the Iron Age in Britain, between 700 and 800 B.C., animal figurines become relatively commonplace, Pitts added.
"And once we get into historical times, we know the pig is quite important in Celtic mythology, though not—to my knowledge—hedgehogs," he said.
Initial results indicate the palisade—of which only a short timber section was found—was constructed 1,000 to 1,500 years after Stonehenge's famed stone circle. The ditch appears to form part of a longer boundary system that runs for about 2 miles (3.2 kilometers), dig co-leader Pollard said.
The new findings hint that Stonehenge was still in use as a religious site until much later than previously suspected.
"The monument is in a reserved part of the landscape that was probably being regarded with a degree of veneration or significance," Pollard said.
(Related: "Stonehenge Partiers Came From Afar, Cattle Teeth Show" [September 12, 2008].)
"It's telling us something about the attitude of later communities to the presence of what by that stage would have been quite an ancient monument," he added.
But Pitts of British Archaeology said that the new dating evidence suggests the palisade and ditch may have little connection to Stonehenge.
"It may actually have more to do with a network of new land-boundary divisions that spread across Salisbury Plain, in common with much of southern England in the Bronze Age after Stonehenge was going out of active use," Pitts said.
People and animals were often buried in such ditches, he said.
"For example, we have a number of curious burials of cattle and horse heads and parts like that in ditches elsewhere on Salisbury Plain. It may be part of the way in which boundaries are marked as land is being parceled up into different units."
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