Geoscience Reference
In-Depth Information
HYLONOMUS LYELLI
The hollow trunk of a lycopod tree at Joggins, Nova Scotia, yielded what is still the oldest reptile in the fossil
record, dating to 300 million years ago, in the Pennsylvanian period of the Carboniferous. The lycopods are gi-
ant relatives of the living club mosses and grew along river channels on a flood plain. Waters washed down
from nearby highlands and crested the natural riverside levees, depositing sediments over the roots of the trees,
thereby killing them. A windstorm eventually snapped off the trunks, and the soft inner tissues of these primit-
ive trees rotted.
The bark was durable, however, creating a hollow stump, which Sir John William Dawson dubbed a
“strange repository.” With each new flood, sediments accumulated around the base of the dead tree until it
reached the lip of the trunk. At this point, the primitive reptile either fell or crawled into the tree trunk, where it
was preserved when another spate flooded the area. The creature, which Dawson named Hylonomus, or “forest
dweller,” must have been a terrestrial animal to have been preserved in this manner. The skeletons are mixed
with charcoal, suggesting that the reptile may also have entered the trunk through fire scars. The presence of
abundant coprolites, or fossilized feces, also suggests that the reptiles may have used the hollowed-out tree
trunks as dens where they moved in to feed on millipedes, insects, and snails (also preserved in the trunks) and
eventually became trapped. Either way, the fossilized skeletons themselves confirm that this was a new type of
animal, a reptile rather than an amphibian.
QUARRYING FOR TRACKWAYS
THE FIRST
evidence of dinosaurs on the North American continent was discovered in 1802 by a young farm-
boy Pliny Moody. While plowing his father's field in South Hadley, Massachusetts, he uncovered a red sand-
stone slab containing three-toed dinosaur footprints. Pliny and his neighbors jokingly attributed the trackways,
which were proudly displayed above a door in the Moody farmhouse, to “Noah's raven,” thinking they had
been made by ancient birds.
Subsequently, many dinosaur trackways came to light in the New England quarries that supplied brown-
stone for Manhattan's mansions. Reverend Edward Hitchcock, the president of Amherst College, in Massachu-
setts, spent a lifetime collecting and writing about the Connecticut Valley trackways. He died in 1864, persist-
ing in his view that the tracks were made by birds: “Now I have seen, in scientific vision, a [wingless] bird,
some twelve or fifteen feet high,—nay, large flocks of them,—walking over the muddy surface, followed by
many others of analogous character, but of smaller size.”
We now know that Hitchcock was essentially correct in his analysis, for modern birds have since been
shown to be the direct descendants of dinosaurs. We also know that many of the early dinosaurs were the size
of chickens and turkeys, or even smaller. Tracks made by a dinosaur no bigger than a robin were discovered in
the Bay of Fundy in 1984.
One of the most important repositories in the United States is Riker Hill Fossil Site (also referred to as Wal-
ter Kidde Dinosaur Park) in Roseland, New Jersey. This 6.4-hectare (16-acre) site preserves a bounty of dino-
saur tracks. Three teenagers, Paul E. Olsen, Tony Lessa, and Bruce Lordi, began visiting the old quarry in
1968, uncovering more than a thousand dinosaur tracks. They sent a cast of one of the largest—Eubrontes gi-
gantes—to President Nixon in hopes of thwarting a development plan for the site, which was declared a Na-
