The
New Scientist article
Early dinosaurs crawled before they ran quotes Robert Reisz, of
the University of Toronto: 'I can't think of any living vertebrate
that does this, except possibly us, and we are terribly awkward as
hatchlings.' (What an odd turn of phrase, to specify vertebrates
and qualifying 'us'.)
Reisz led the research team investigating dinosaur eggs discovered
in the Golden Gate Highlands National Park, South Africa in 1978.
They used 'the latest archaeological tools - including miniature
jack-hammers and fine dental drills - to crack open two' of the six
eggs from the South African discovery. From the article:
the shape and size of each embryo's head,
neck and forearms suggests that baby Massospondylus crawled
on four legs after hatching, learning to walk on two legs only
later on in life. The researchers suspect the hatchlings' large
heads may have been too heavy for their long, horizontally oriented
necks to support comfortably.