P.S.
Ro
672
no. 4

ATT^TWHEN?*«0?w=MfU)iU)t

Ft

IL

1H ONTARIC

M8 Hi L@m@)it

Royal Ontario Museum / University of Toronto

/ keep six honest serving-men

(They taught me all I knew);

Their names are what and why and when

And how and where and who. rudyard kipling

ROYAL ONTARIO MUSEUM SERIES

WHAT ? WHY ? WHEN ? HOW ? WHERE ? WHO ?

1 K. B. Brett: women's costume in early Ontario

2 Gerald Stevens: early Ontario glass

3 Walter M. Tovell: the Niagara escarpment

4 R. R. H. Lemon: fossils in Ontario

5 W. E. Swinton: dinosaurs of Canada

6 L. S. Russell: the mastodon

© The Governors of the University of Toronto, 1965

This series was edited in the Information Services of the Royal Ontario Museum by
Ian Montagnes. It was designed by Harold Kurschenska, and printed at the University
of Toronto Press. Illustrations in this booklet are by Paul Geraghty, rom artist
craftsman, and Lee Warren, rom photographer.

Quotation from the just so stories by Rudyard Kipling, by permission of
Mrs. George Bambridge and The Mac mill an Company of Canada Limited

WHAT? %®W*

</1

WHERE

HEN? JJJUOt

Fossils in Ontario

by R.R.H. LEMON

m®

are fossils formed?

Fossils are the remains or impressions of animals and plants which lived in
prehistoric times. In Ontario we have some of the richest fossil-bearing
rocks in the world. We also have some of the very oldest known fossils —
traces of primitive plants which lived in the morning of life on earth, 2000
million years ago, when even the most complex form of life consisted of only
a single cell. And we have some very recent fossils, such as the bones of
mastodons which lived only 6000 years ago when Indians already were
hunting in the area. In one small corner near Hudson Bay there may be the
remains of dinosaurs, but over the rest of the province the rocks from that
era (and therefore also the fossils) have all been eroded away. We have,
however, copious records of the period before the dinosaurs, when for
hundreds of millions of years Ontario was covered by warm seas which
swarmed with a variety of bizarre animals without backbones. It is their
remains which are most commonly found in Ontario, and which form the
subject matter of this booklet.

Fossils may be preserved in many different ways, depending upon when
and where the animal or plant lived, how it died, and what subsequently
happened to the matter entombing it. Some of the processes are quite

simple. A mastodon, for example, blunders into a muskeg and drowns; its
bones, protected and preserved by the swamp, may lie undisturbed for
thousands of years until a bulldozer tears up the land. Or a flying insect is
trapped in the sticky resin oozing from a prehistoric pine; the resin hardens
into clear amber, preserving every detail of the tiny animal from decay. It is
even possible for animals to remain deep-frozen for tens of centuries,
embedded in the ancient ice and frozen mud of Alaska and Siberia. One of
the most unusual banquets in history was held in St. Petersburg, Russia, at
an International Geological Congress at which mammoth steaks were
served: one report says the meat was quite edible, though somewhat lacking
in flavour!

The most common fossils owe their existence to a much more complex
process. In many, the original shell material or skeleton has been replaced
completely by another harder and more durable mineral. Let us take one
instance. A clam — very much like the ones we eat today — died millions of
years ago and its shell, lying on the sea bottom, gradually was buried by a
slow rain of sand and mud and organic debris. As the centuries passed the
covering layer grew deeper and deeper. Still, water could pass through the
sediment and reach the shell. (Obviously, more water would reach the shell
if the sediment was coarse-grained, such as gravel or sand, than if it were
clay.) In time, the deposits which buried the animal turned into rock. But
at the same time, as a result of chemical reactions between the shell material
and minerals carried in solution in the water, the shell itself also changed:
gradually it dissolved and was replaced, molecule by molecule, by the
mineral (usually calcite or silica) deposited out of the water. Thus the
original shape and even the finest details of the shell were preserved for the
fossil hunter, yet no trace was left of the original material secreted by the
clam. It had all been turned into stone.

Often this process happened quite quickly as geological time goes, over
perhaps 100,000 years. On the other hand original shell material has been
found dating back to the Cretaceous period (see time chart, page 15) and in
some shells the mother of pearl has retained its glistening beauty for more
than 100 million years.

Unfortunately in the replacement process the shell invariably loses its
natural colour, though occasionally faint markings on the fossil suggest the
original patterns. Sometimes, on the other hand, the shell assumes a new
and alien beauty from the mineral which now forms it, such as the metallic
glitter of the iron mineral pyrite or the gemstone colours of chalcedony and
jasper. Most likely in their lifetimes the invertebrates of prehistory were no
less brightly coloured than those alive today. It seems certain that if a time
traveller were to walk along the fringe of some Palaeozoic sea, his eyes
would be attracted by many colours among the shells on the beach.

When an animal dies its fleshy parts soon decay and usually only the hard

Warm salt seas once covered the area we now call Ontario. In them flourished
a rich variety of creatures. Some appear in this rom reconstruction of life in the
Devonian period, 400 to 350 million years ago. The tall objects at the centre
are sponges. Brachiopods, crinoids, horn corals and trilobites also are evident.
Fish, like the armoured specimen at the right, were by this time common.
Devonian fossils may be found in the vicinity of Stratford and London.

skeleton or shell survives long enough to become a fossil. Yet under excep-
tional conditions decay may be inhibited until the soft remains have been
buried and the surrounding sediment hardened sufficiently to retain an
impression. Alternatively, traces of the soft parts may be preserved in shale
and other rocks as films of organic carbon resting upon the bedding surface
which once was the bottom of a sea. What exceptional conditions make this
possible? Decay is largely caused by aerobic bacteria, which like all animals
must have oxygen to live: in stagnant pools the oxygen in the water, and

particularly in the mud at the bottom, can be so depleted that the bacteria
cannot survive. This can happen even in the sea, in enclosed bays or fiords
where neither tide nor wind stir up the water sufficiently to replace the
oxygen consumed by bottom-living organisms. Under such antiseptic cir-
cumstances, the soft parts are preserved for at least a time. Happily for the
scientist these same conditions caused mass destruction of life in prehistoric
seas, producing a great abundance of fossils of all kinds in fine-grained
black shales which occur in rock sequences of all ages.

Fossils may be preserved in any kind of sedimentary rock, not only in
ancient sea bottoms, but also in rock formed from the sediment on the beds
of lakes and rivers, or even from land features such as sand dunes. But
some sedimentary rocks are much more likely to contain fossils than others.
Many things can happen even after the special circumstances which record
the imprint of a living creature.

The older the rock, the more likely it is to have been metamorphosed, or
altered, under great pressure and heat within the earth's crust. In these
changes new minerals form, old ones are recrystallized, and invariably any
fossils are completely obliterated. Again, rocks are subject to folding or
squeezing in the episodes of mountain building which have occurred from
time to time through the history of the world. This is another process which
destroys, or at least distorts, the fossil record. Then there are the attacks of
wind and water. Sedimentary rocks formed in lakes or rivers, or on dry
land, are particularly vulnerable and may easily be obliterated as the land-
scape is sculptured by erosion. This is what happened to the Mesozoic rocks
of Ontario. On the other hand, the shallow seas which once bordered ancient
continents, and the inland seas which once covered much of today's land
mass, often persisted for millions of years, and in them thick sediments of
all kinds formed and were protected. Moreover, the rocks laid down in such
seas were often very widespread; a single limestone formation may cover
tens of thousands of square miles. Yet even deep-lying strata may be lifted
to the surface by earth movements and thus exposed to erosion.

"W'HErLE do we find fossils in Ontario?

The landscape of southwestern Ontario is new for the most part, as such
things go. Large areas of it were formed by glaciers which advanced from
the north during the Ice Ages, carrying with them vast quantities of clay,
sand, gravel and even boulders which they stripped from the surface in their
path. In intervals of warmer climate the glaciers melted, leaving behind
their burden. These giant ice fields advanced and retreated during the
Pleistocene period, which began some 1 ,000,000 years ago and lasted until
only about 10,000 years ago. Today, in certain sands and gravels laid

Legend

Queenston delta

Prehistoric seas covered much of what is today the interior of North America.
This map shows their extent about 450 million years ago, during Ordovician
times. One pocket of dry land was formed by the young Appalachian Mountains
and a series of huge deltas which built up to the west of them.

down by run-off from the glaciers, we find fossil shell fish and land snails.
Occasionally twigs and leaves and other plant remains turn up, and even
more rarely traces of large animals, such as the bones, teeth and tusks of
mastodons and mammoths.

Beneath the glacial deposits, in solid rock, lies the record of a much more
remote time. Hundreds of feet of limestones, shales and sandstones were
deposited as mud or sand at the bottom of great inland seas which once
covered large parts of North America. Ontario was under water during
much of the Ordovician, Silurian and Devonian periods (450 to 350 million

In the wavering light beneath the surface of an Ordovician sea, a time-travelling
scuba diver might encounter such a scene as this. In the foreground crawls a
species of trilobite, Isotelus, which today is a common Ontario fossil. To the right
a group of Rugose corals wave their tentacles from atop their horn-shaped
homes. The animals growing on low stalks nearby are brachiopods.

years ago). During these 110 million years the seas changed constantly,
growing larger or shrinking as the land about them fell or rose. It was a slow
and complex process : it took millions of years for the shoreline to advance
a few hundred miles, and even then the land might rise again, and for a
second time be submerged. At river mouths, deltas formed and added other
chapters to this story in the rocks. Fortunately, the interior of North
America has been largely still over long periods of geologic time. The
upthrusts which produced the Appalachian and Rocky Mountain chains on
the margins of the continent left the centre largely undisturbed, or at the

most faulted, gently tilted or flexed. The record remains for us to read — and
the inland seas produced some of the richest fossil-bearing rocks in the
world.

In southern Ontario, limestones, shales and sandstones range in age from
Middle Ordovician to earliest Mississippian, with a few patches of Cambrian
strata around Kingston. These sedimentary rocks form a series of relatively
thin layers above an ancient basement of Precambrian rocks. Some time
after their formation a large scale tilting of the whole region caused these
layers to dip in a shallow angle towards the southwest. Later still, erosion
stripped off the uppermost rocks in the north and northeast regions. As a
result the oldest rocks, mostly of Ordovician age, are found at or near the
surface to the east and northeast, while the youngest formations of early
Mississippian age are confined to a small area in the extreme southwest.

The rock formations of southern Ontario slope gently to the southwest. As a
result, fossils can be found from several different periods, progressively more
recent from east to west.

If you were to drill below the glacial deposits near Toronto you would
encounter only Ordovician and Cambrian rocks before reaching the Pre-
cambrian basement; on the Niagara escarpment you would pass through
Silurian rocks as well, and further southwest the succession is still more
complete.

Wherever streams have cut down through the mantle of glacial drift to
expose the sedimentary rocks, there is a potential site for fossil collecting.
The richness and variety of specimens of course varies enormously. Many
limestones of the Niagara escarpment contain an abundance of brachiopods,

corals, crinoids and other Silurian remains. On Georgian Bay, in the black
shales of the Collingwood Ordovician formation, it is possible to find trilo-
bites, brachiopods, crinoids and graptolite fossils in outcrops along the
shore.

Fossil hunting is better in natural rocky outcrops than in areas which
have been artificially exposed, such as highway cuttings or quarries. The
slow weathering of the exposed rock plays a big part in etching the fossils
on the surface and in releasing them from the surrounding matrix. On
freshly broken rock surfaces fossils are usually very difficult to discover,
and even more difficult to extract. This is particularly true of limestones,
which are perhaps the most characteristic form of sedimentary rock in
Ontario.

You may also find fossils in loose stones lying in river beds and open
fields throughout southern Ontario. An hour spent on a farmer's rock pile,
cracking open stones of sedimentary origin left behind by the glaciers, can
turn up a number of smaller species.

WH

did life begin in Ontario?

Few fossils exist in rocks which date from before the Cambrian period,
simply because life forms then were so very primitive. The hard structures
capable of preservation were extremely rare, or absent. But the Precambrian
basement is not entirely void of evidence of organic life. In a few places in
the Grenville limestones there have been found concentrically laminated
structures, built up in layers something like cabbages, and measuring up to
several feet in diameter. These are thought to represent the work of algae
(a primitive plant) capable of secreting a limey framework. Something
similar exists today in calcareous algae such as Lithothamnion. Numerous
different species have been recognized by specialists studying these ancient
plants, and the name Eozoon was given to one kind found in Ontario. By
methods of radioactive dating, using the measured rate of change of uranium
to lead, and of potassium to argon, these rocks have been shown to be some
1000 million years old.

Although these fossils are among the oldest direct manifestations of life
on earth, similar or more primitive life forms existed alongside Eozoon, and
for 1000 million years before. In 1965 scientists reported the discovery
near Schreiber, Ontario, of fossil algae 2000 million years old, visible only
with a microscope. The fossil record becomes more easily discernible,
however, at the beginning of the Cambrian period, some 600 million years
ago, and through the periods which followed the number, variety and
complexity of animals and plants gradually increased.

WHAT

m

fossils are found in Ontario?

Several thousand fossil species have been found in the province. Some of the
most common forms are shown on the following pages. (The name and
geological age of each specimen illustrated appears in parentheses after a
brief general description. )

graptolites are true mystery creatures, without living relations, extinct for
nearly 400 million years. They were colonial animals which floated on the ocean
surface, forming delicate, often branching, chitinous skeletons, typically no
more than % inch wide and perhaps % to 4 inches long. Because they were so
fragile, graptolite fossils are usually found only in fine-grained rocks such as
shales, deposited in quiet water. On the bedding surfaces they look much like
pencil marks. Under a magnifying glass you can see small saw-like serrations
along the branches, and under rather high magnification these appear as pores,
each of which contained a soft-bodied animal. Graptolites appeared at the close
of the Cambrian Period and died out during the Devonian. (Climacograptus
aequalis: Ordovician)

crinoids looked like flowers, but were really animals related to the starfishes
and sea urchins. The crinoid's soft body was protected by a series of hard limey
plates which formed a small cup-like structure. To this were attached long
jointed arms, radiating outwards and upwards, which gathered food. The animal
was anchored to the sea bed by a long, flexible jointed stem, made up of small
discs connected by muscular tissue. After death the tissue decayed and the discs
scattered on the sea bed. Fossil discs (Js to % inch in diameter) are extremely
common in some limestones. Numerous species still survive. {Cupulocrinus
jewetti: Ordovician)

trilobites were marine animals with segmented bodies and jointed limbs,
related to the crabs, spiders and insects. They appeared in the lower Cambrian,
reached their zenith about the middle of the lower Palaeozoic and died out in
the Permian. Most trilobite fossils are only an inch or so long, but during the
Cambrian and Ordovician, when they were among the dominant life forms, they
reached more than 18 inches. In Ontario, Ordovician, Silurian and Devonian
rocks contain several fairly common species, (lsotelus maximus: Ordovician)

cephalopods, related to modern squids and cuttlefish, swarmed in the ancient
seas. At times they were the dominant invertebrates, and some reached over
4 feet in length. In shape they ranged from straight-shelled species to ones
elaborately coiled and ornamented. The straight, cone-shaped variety is perhaps
the most common fossil found in the Ordovician limestones of Ontario. Only the
wide end of the shell was occupied by the soft-bodied animal which built it:
the rest was closed off and divided into a series of chambers by cross walls.
When the fossil is broken open these walls often are mistaken for the vertebrae
of a fossil fish. (1. Michelinoceras sp.: Ordovician. 2. Plectoceras halli: Ordo-
vician. 3. Reconstruction of Michelinoceras sp.)

10

(jraptolites

l^rilobite

Crinoid

Cephalopods

M

gastropods (snails) existed as early as the Cambrian Period, and are fairly
common in Palaeozoic rocks of Ontario. They lived in both fresh water and
marine environments. Pleistocene fossils of freshwater gastropods sometimes
can be found in interglacial sands and gravels. (Fusispira subfusiformis:
Ordovician)

pelecypods (clams) are bivalved shellfish. Fossils found in sedimentary rocks
throughout the world suggest that during most of their long history (beginning
in the Cambrian) they have lived in both fresh and salt water. Since the Meso-
zoic pelecypods have become increasingly prolific and varied. A few fossil
species may be found in Ontario, notably in the Ordovician limestones of the
Toronto area and the Silurian Guelph formation. {Byssonychia radiata:
Ordovician)

brachiopods superficially resemble clams, but belong to a completely different
division of animals. They have an extremely ancient lineage: fossils occur even
in Precambrian rocks deposited perhaps 700 million years ago. They were
abundant in Palaeozoic seas, and at times were the dominant animal, but have
dwindled since the Mesozoic Era. Lingula, a small horny brachiopod still found
burrowing in mudflats today, is very little different from its ancestors of Ordo-
vician times. (Spirifier radiatus: Silurian)

corals may be found in many limestones of southwestern Ontario, sometimes
in reef masses up to several feet across. Two main groups are represented,
Rugose and Tabulate corals. A third major group, which includes all modern
reef-forming corals, had not yet evolved when the rocks of Ontario were laid
down.

You may find two kinds of Rugose corals. The solitary variety (cup, or horn,
corals) are shaped like straight or gently curved cones, within which numerous
vertical walls, or septa, radiate from the centre. The walls were formed by
in-foldings on the bottom of the soft polyp animal which rested upon this
skeleton. Horn corals up to 12 inches long and nearly two inches wide have been
found, but are exceptional. Colonial Rugose corals are similar in their internal
structure to the solitary variety, but in effect they have been squeezed together
in a group — so closely that their skeleton tubes have become roughly pentagonal
or hexagonal. The tubes are usually smaller than those of horn corals but contain
the same radiating septa.

Tabulate (or honeycomb) corals look superficially like colonial Rugose
corals, but are very different within. Instead of septa they contain horizontal
platforms, or tables, which fill the coral tubes at intervals from top to bottom,
rather like floors in a very tall and narrow skyscraper. These can be seen clearly
when a colony is broken open. Tabulate corals are never found as solitary
individuals and their tubes are invariably smaller than those of colonial Rugose
corals. (1. Heliophyllum halli: Devonian. 2. Prismatophyllum williamsi:
Devonian. 3. Favosites maximus: Devonian)

12

Cfastropod

Brachiopods

Te key pod

J^ugosz solitary-

Corals

7{ugosz colonial

Tabulate

13

///?M aren't these animals alive today?

Nothing in nature is constant. Even the landscape changes, far more than
we often realize. Mountains rise and are eroded away, seas dry up, the
climate may grow warmer or colder, new forms of vegetation appear and
crowd out the old ones. Sometimes the change is violent, as when a volcano
erupts in the middle of a cornfield. More often, these transformations take
millions and millions of years.

Most animals are suited to live in a particular environment. If it grows
too hot or too cold, or their food dies out, or a new species appears which
preys upon them, then they may not be able to survive. But if the change is
gradual enough, their bodies may adapt, generation by generation, to the
newr conditions, for the process of change extends to every living creature.
Variations, or mutations, are always occurring, and are passed on from one
generation to the next. Sometimes they fit the animal better to live in a
changing environment. For example, its colour may alter, so that it is better
camouflaged from predators, or it may be able to digest a wider variety of
plants. Within a particular species, the animals that are better fitted to
survive will pass on these changes to their descendants; the animals not so
well fitted will gradually disappear; and over tens of thousands of years the
whole species will subtly be transformed.

This is a greatly over-simplified explanation of the theory of natural
selection, the main factor in evolution, but it suggests some answers to our
question. If the environment changes too rapidly for the animals to adapt
to the new conditions they will die out. Even if the change is very gradual,
it is possible that no favourable mutations will occur. Or if the animals are
able to adapt, in the process an entirely new species may evolve and the old
one disappear. There is one other possibility: that some individuals will be
able to find an environment which remains favourable. That is why —
300 million years after the last seas dried up in Ontario — a very few so-called
living fossils from those days still survive in other oceans of the world.

UUI0

studies fossils?

The palaeontologist (from the Greek: palaios, ancient; onta, existing things;
logos, a discourse) is a scientist who studies the succession of life through
the ages, from its earliest beginnings thousands of millions of years ago up
to the present. His only clues are the fossil remains, so in part he is a fossil
hunter — but that is only the beginning of his work.

In the laboratory his discoveries are cleaned and prepared for detailed
study. This may simply involve a small amount of brushing and scraping to
remove loose sand or clay. When the fossil is embedded in hard rock,

14

RECORD Of LIFE, THROUGH GEOLOGICAL TIME

ERA

PERIOD

DOMINANT LIFE

Mammals

Reptiles
Ammonites

Amphibians

Fishes

Invertebrates

ARCHAEOZOIC

Rise of
Invertebrates

however, it may mean hours of painstaking drilling, scraping and chipping
with the delicate instruments used by dentists and surgeons. In some cases
the surrounding rock, especially when it is limestone, may have to be
removed by dilute acid which dissolves the matrix without harming the
fossil. As in so many things, Nature is sometimes better at such work than
man, for rain water is slightly acid due to the presence in it of minute
quantities of carbon dioxide from the atmosphere. Thus fossils which have
weathered over thousands of years often show details that could never be
brought out in any other way.

Even if a fossil cannot be freed from the surrounding rock, it is far from
useless. The rock can be cut into thin slices, and when these are etched with
acid the internal structure of the fossil can be clearly seen. It is also possible
to grind down these slices until they are less than a thousandth of an inch
thick, so that they are transparent and their finest details can be studied
under a microscope.

Since palaeontology embraces a vast variety of life forms, it is clearly
impossible for any one man to study the entire field. Some palaeontologists
specialize in the prehistoric animals which had backbones, or even in one
kind such as the armoured dinosaurs, or the early mammals, or a particular
group of fishes. The invertebrate palaeontologist deals with molluscs, corals,
crustaceans and other lower animals, though even here he may specialize in
one or two closely related groups. He may for example concentrate on
animals like the protozoans which can be seen only with a microscope.
Others concentrate on palaeobotany, the rapidly growing study of plant
remains — and even of their spores and pollen. Or he may be an applied
palaeontologist, using his specialized knowledge to help in the search for oil.

Beside the zoologist who studies living creatures, the palaeontologist
faces severe disadvantages: he usually has no direct evidence of what the
soft parts of the animal looked like, nor can he observe his subjects' growth
and habits. On the other hand, he can accurately reconstruct fossil animals
— as they looked in their lifetimes — by studying the remaining hard parts,
which may show muscle scars, and by analogy with living relatives. The
latter method becomes increasingly dangerous, however, the further he goes
back in geological time, for the relationship with living species grows
correspondingly more tenuous.

The palaeontologist has one important advantage over the zoologist. He
has access to a whole new dimension — time. By studying the fossil faunas
through successively younger layers of rock, he is often able to piece
together the life history not of an individual, but of a whole race of animals.
He can often discern the earliest beginnings of a group and follow its
gradual evolutionary changes over millions of years, seeing how one
particular species evolved and gave rise to others. Thus he can trace the
various branches and stems of the tree of life.

16

SUGGESTED READING

BUCHSBAUM, R. Animals without Backbones (Chicago University Press, 1948)

CARRINGTON, richard. A Guide to Earth History (Penguin Books, 1958)

goldring, Winifred. Handbook of Paleontology for Beginners and Amateurs
( Handbook No. 9, New York Museum, Ithaca, N.Y., 1960)

OAKLEY, kenneth p. and helen m. muir-wood. The Succession of Life through
Geological Time (British Museum (Natural History), London, 1962)

Rhodes, f. T., H. s. zim and P. r. shaffer. Fossils — A Guide to Prehistoric Life
(Golden Press, New York, 1962)

smith, john maynard. The Theory of Evolution (Penguin Books, 1958)