A large stone slab containing mudcracks and many footprints left by small theropod dinosaurs, as illustrated in Hitchcock's "Ichnology of New England."
Edward Hitchcock
was one of America’s first dedicated dinosaur paleontologists. He just
didn’t know it. In fact, during the latter part of his career, he
explicitly denied the fact. To Hitchcock, the tracks skittering over red
sandstone in the Connecticut Valley were the marks of prehistoric birds
from when the Creation was new. Hitchcock could not be dissuaded. As
new visions of dinosaurs and the notion of evolution threatened to
topple his life’s work, the Amherst natural theologian remained as
immutable as the fossil footprints he studied.
Hitchcock was not the first to wonder about the prehistoric imprints.
Members of the Lenape, a Native American group in Canada and the
northeastern United States, had seen the bizarre, three-toed tracks and
ascribed them to monsters and other beings. These were the footsteps of
creatures that ruled the world before humans came to dominance. European
settlers and their descendants had to stretch their mythology a little
more to accommodate the tracks. Some thought such tracks might have been
left by Noah’s raven after the biblical deluge, although many simply
called them “turkey tracks” and apparently were little concerned with
where they had come from.
It wasn’t until 1835 that James Deane, a doctor with a curiosity for
natural history, found out about a sample of the peculiar tracks near
Greenfield, Massachusetts. He knew that they represented prehistoric
organisms, but he wasn’t sure which ones. He wrote to Hitchcock, then a
geology professor at Amherst, to inquire about what could have left such
markings in stone. At first Hitchcock didn’t believe Deane. There might
be some quirk of geological formation that could have created
track-like marks. But Deane was persistent. Not only did he change
Hitchcock’s mind, but the geologist became so enthusiastic that he
quickly became the most prominent expert on the tracks—a fact that
frustrated Deane and led to tussles in academic journals over who really
was the rightful discoverer of the Connecticut Valley’s lost world.
Hitchcock began publishing about the peculiar trace fossils in 1836.
He was confident from the very start that they must have been created by
prehistoric birds. (He was so enthused by the idea he even wrote poetry about the “sandstone birds.”)
No variety of creature matched them better. The word “dinosaur” had not
even been invented yet; the British anatomist Richard Owen would
establish the term in 1842. The few dinosaurs that had been found, such
as Iguanodon, Megalosaurus and Hylaeosaurus,
were known only from paltry remains and all were believed to have been
enormous variations of lizards and crocodiles. Dinosaurs were a poor fit
for the tracks, and became even worse candidates when Owen gave them an
anatomical overhaul. Owen not only named dinosaurs, he re-branded them
as reptiles with mammal-like postures and proportions. The huge
sculptures of the Crystal Palace exhibition, created with the help of artist Benjamin Waterhouse Hawkins,
are a testament to Owen’s view of dinosaurs as reptiles that had taken
on the anatomical attitudes of rhinoceros and elephants.
But Owen and other paleontologists did not agree with Hitchcock’s
interpretation. They argued that the tracks could have been made by some
unknown variety of amphibian or reptile. This was not so much because
of the anatomy of the tracks—anyone could see that they were made by
creatures with bird-like feet—but because no one thought that birds
could have lived at so ancient a time or grown large enough to make the
biggest, 18-inch tracks Hitchcock described. Even though early 19th
century paleontologists recognized that life changed through the ages,
they believed there was a comprehensible progression in which so-called
“higher” types of creatures appeared later than others. (Mammals, for
example, were thought to have only evolved after the “Secondary Era”
when reptiles ruled since mammals were thought to be superior to
mosasaurs, ichthyosaurs, and other creatures of that middle time.)
Hitchcock remained steadfast, and his persistence was eventually rewarded with the discovery of the moa.
These huge, flightless birds recently lived on New Zealand—they were
wiped out more than 500 years ago by humans—and in 1839 Richard Owen
rediscovered the birds through a moa thigh bone. He hypothesized that
the bone must have belonged to a large, ostrich-like bird, and this idea
was soon confirmed by additional skeletal bits and pieces. Some of
these ratites stood over nine feet tall. When the news reached Hitchcock
in 1843, he was thrilled. If recent birds could grow to such sizes,
then prehistoric ones could have been just as large. (And, though
Hitchcock died before their discovery, preserved moa tracks
have a general resemblance to some of the largest footprints from the
Connecticut Valley.) Opinion about the New England tracks quickly
changed. There was no longer any reason to doubt Hitchcock’s hypothesis,
and paleontologists hoped that moa-like bones might eventually be found
to conclusively identify the trackmakers.
Lacking any better hypotheses, Hitchcock prominently featured his
avian interpretation of the three-toed tracks in his 1858 book The Ichnology of New England.
It was a gorgeous fossil catalog, but it also came at almost precisely
the wrong time. Gideon Mantell, the British doctor and paleontologist
who discovered Iguanodon, was beginning to wonder if some
dinosaurs primarily walked on their hind limbs in a bird-like fashion,
and the Philadelphia polymath Joseph Leidy described Hadrosaurus,
a dinosaur certainly capable of bipedal locomotion on account of having
shorter forelimbs than hindlimbs, the same year that Hitchcock’s
monograph came out. Dinosaurs were undergoing another major overhaul,
and the few that were known at the time were being recast as relatively
bird-like creatures. Even worse for Hitchcock, the following year
another student of the Connecticut Valley tracks, Roswell Field,
reinterpreted many of the footprints and associated traces as being made
by prehistoric reptiles. Especially damning was the fact that deep
tracks, left when the creatures sunk into the mud, were sometimes
associated with drag marks created by a tail. Hitchcock’s tableau of
ancient Massachusetts moas was becoming increasingly unrealistic.
If Hitchcock ever doubted his interpretation, he never let on. He
reaffirmed his conclusions and modified his arguments in an attempt to
quell dissent. In his last book, A Supplement of the Ichnology of New England, published in 1865, a year after his death, Hitchcock used the recently discovered Jurassic bird Archaeopteryx as a way to save his interpretation. Tail drags were no obstacle to the bird hypothesis, Hitchcock argued, because Archaeopteryx
was generally regarded as being the primordial bird despite having a
long, reptile-like tail. Perhaps such a bird could have been responsible
for the trace fossils Hitchcock called Anomoepus, but the tail
drags left by the animals that dwelled in Jurassic New England were
also associated with tracks indicating that their maker walked on all
fours. In response, Hitchcock cast Archaeopteryx as a
quadrupedal bird—a representative of a new category different from the
classic, bipedal bird tracks he had promoted for so long.
Other paleontologists took a different view. If Archaeopteryx looked so primitive and lived after
the time when the red Connecticut sandstone was formed, then it was
unreasonable to think that more specialized, moa-like birds created
Hitchcock’s tracks. Furthermore, a few bones found in a Massachusetts
quarry of roughly the same age in 1855 turned out to belong to a
dinosaur—a sauropodomorph that Othniel Charles Marsh would later name Anchisaurus.
The bird bones never turned up, and all the while dinosaur fossils were
becoming more and more avian in nature. By the 1870s the general
paleontological opinion had changed. New England’s early Jurassic was
not filled with archaic birds, but was instead home to dinosaurs which were the forerunners of the bird archetype.
Our recent realization that birds are the direct descendants of one group of coelurosaurian dinosaurs has led some of Hitchcock’s modern day fans to suggest that he was really right all along. In an essay for the Feathered Dragons
volume, paleontologist Robert Bakker extolled Hitchcock’s scientific
virtues and cast the geologist’s avian vision for the tracks as
essentially correct. Writer Nancy Pick, in her 2006 biography of the
paleontologist, wondered, “What if Hitchcock clung to his bird theory
because he was right?” But I think such connections are tenuous—it is a
mistake to judge Hitchcock’s work by what we have come to understand a
century and a half later.
