What is a fossil,?
From: Phillip Currie
and E.B. Kopplehus, 101 Questions about Dinosaurs, Dover
Publications, 1996 (Philip Currie is Curator of Dinosaurs at the Royal
Tyrell Museum in Drumheller, Alberta, Canada and an Adjunct Professor in
the Departments of Biology, Geology and Geophysics at the University of
What is a fossil?
Although many definitions of "fossil" (derived from the Latin word
for "dug up") have been published, one of the best is that fossils
are simply any evidence of extinct life. Bones do not have to be
"turned into stone" to be fossils, and usually most of the original
bone is present in a dinosaur fossil. Footprints, the impressions
left in mud, as well as dung and eggs, are some of the other common
types of dinosaur fossils. Although the horny beaks of hadrosaurs
(duckbilled dinosaurs), cartilage at the ends of long bones, and
skin usually decompose before they have an opportunity to fossilize,
these things are sometimes pre-served. Most remarkable, perhaps, is
the recent discovery that ancient genetic material, including DNA,
can be extracted from dinosaur teeth, bones and eggs.
How long does it take for a bone to become "fossilized"?
Questions about Dinosaurs (emphasis not in the original):
Fossilization is a
process that can take anything from a few hours to millions of
years. "Fossilized" bone is usually considered to be that which has
"turned to stone." The process is called permineralization. When a
bone becomes buried, groundwater seeps through all of the pores and
openings to invade the spaces inside. Minerals carried by the water
are deposited inside these spaces, and over time can fill them in
completely. This is similar to what happens in the sediments around
the bone, where minerals carried in solution are deposited in the
spaces to cement sand grains together to form sandstones, silts into
siltstones, and so on. The amount of time that it takes for a bone
to become completely permineralized is highly variable. If the
groundwater is heavily laden with minerals in solution, the process
can happen rapidly. Modern bones that fall into mineral springs
can become permineralized within a matter of weeks. The preservation
of soft tissues in some dinosaurs also suggests that, under
exceptional circumstances, fossilization can occur within days.
Some of the more common minerals found in permineralized bone are
cal-cite, iron, phosphate and silica. Virtually any mineral that can
be carried in solution in water can be found in fossilized hones,
however. Dinosaur bones found in northeastern Colorado contain
enough uranium to be located by a geiger counter. Dinosaur bones are
not always permineralized, however. In Dinosaur Provincial Park in
Alberta, dinosaur hones were sometimes encased in ironstone nodules
shortly after they were buried 75 million years ago. The nodules
prevented water from invading the bones, which for all intents and
purposes cannot he distinguished from modern bone. A more
spectacular example was found on the North Slope of Alaska, where
many thousands of hones lack any significant degree of
perrnineralization. The bones look and feel like old cow bones, and
the discoverers of the site did not report it for twenty years
because they assumed they were bison, not dinosaur, bones.
We note that fossils of
dinosaurs can form rapidly, that their bones are discovered on or near
the surface, that the bones look fresh and could even be confused with
bison or cow bones (both large mammals). This means that dinosaur bones
(ancient reptiles) and large mammals are found in the same layer.
From: Duck-bill dinosuars (Hadrosauridae,
Ortnithiscia) from the North Slope of Alaska.
KYLE L. DAVIES. Journal of Paleontology, v. 61, no.1, January 1987, pages
(Davies did this work while at the Vertebrate Paleontology Laboratory, Balcones
10100 Burnet Road. Austin. Texas 78758).
HADROSAUR BONES have been found on the Colville River north of Umiat
on the North Slope of Alaska. This find represents the first report
of dinosaur bones in Alaska and their northernmost reported
The hadrosaur bones were collected in
1961 by the late R. L. Liscomb while working for Shell Oil Company.
Renewed research around the Colville River led to the bones being
sent to the U.S. Geological Survey in Menlo Park, where they were
tentatively identified as hadrosaurian by C. Repenning. He
sent the bones to the Texas Memorial Museum for further
investigation, and the Shell Oil Company was kind enough to donate
the bones to TMM for safekeeping. The bones were found on the
Colville River at approximately 70°N, 151 °W (Figure 1), and the
site was relocated in 1984 by two U.S. Geological Survey field
parties (C. Repenning, personal common.). The site is easily
accessible by float plane or helicopter, common means of
transportation in the area, and to deter possible vandalism it is
felt best not to reveal the exact location of the site. Precise
locality information is on file at TMM.
The site occurs in what is mapped as
undifferentiated Upper Colville Group of Late Cretaceous age,
which is overlain by the Plio(?)-Pleistocene Gubik Formation (Brosge
and Whittington, 1966). Recent studies. however, have indicated
Paleogene rocks in this region (Carter et al., 1977; Nelson, 1981:
Marincovich et al., 1983). Pending resolution of the stratigraphy,
beds underlying the Gubik Formation in the region are being referred
to simply as "pre-Gubik" (Carter et al., 1977; R. V. Emmons,
personal commun.). Hadrosaurs are exclusively Late Cretaceous and
their presence limits the age of the pre-Gubik rocks. "This datum
has allowed H. J. Clippinger to interpret somewhat contaminated
pollen samples and establish a Maastrichtian or possibly Campanian
age for the strata 28 feet above and 12 feet below the dinosaur bed.
Foraminifera 2 feet below the bone bed indicate a shallow marine
environment" (Shell Oil Company memorandum, with per-mission of R.
V. Emmons and H. J. Clippinger).
Shell Oil Company's stratigraphic
section of the locality shows the fossil bones come from a thin
sandstone in pre-Gubik silty sands. Matrix still adhering to the
bones is a soft, brown, sandy silt.
The bones, catalogued as TMM 42475-1.
apparently represent a quick surface collection by Liscomb,
and consist of fragments of limb bones, ribs, and vertebrae. The
quality of preservation is remarkable. The bones are stained a
dark red brown but otherwise display little permineralization,
crushing, or distortion. None of the diagnostic cranial or pelvic
bones were recovered, so determination below family level is not