THE PALAEARCTIC REALM

The Palaearctic realm is the largest of the zoogeographical realms, covering as it does the largest continental area on the planet. From east to west the landmass stretches 17,000 kilometres (10,500 m), but from north to south its maximum width is about 7,000 kilometres (4350 m).
Historically, the continent consists of the largest part of the supercontinent Laurasia (see page 16). On its western margin it is moving away from the other large piece of Laurasia – the Nearctic continent – but on its eastern point it remains very close to it. Many times in the past the continents have been united at this point and there has been a free interchange of animals across the isthmus that has formed there. The southern boundary has always been the Tethys sea, but since Tertian times other continents have moved northwards and united with it. This collision of continents has thrown up the greatest mountain chain in the world and this has acted as a natural barrier to migration, so defining the edge of the realm. In the south-west the continent that now holds the Ethiopian realm has not quite united with the Palaearctic realm. There is still an inland sea between them. The animal and plant life around this sea is broadly similar so this whole area is regarded as part of the Palaearctic realm as well.
Most of the mountains of the continent are quite recent and lie along the southern edge and around the inland seas in the south-western corner, although there are several older ranges. One of these fringes the islands and peninsulas of the north-west coast, and another runs north-south showing where two ancient continents fused together.
The habitats of the Palaearctic realm tend to run in parallel east-west bands. In the far north is the tundra, a treeless region of permanent chill enlivened by a brief summer. To the south of the tundra lies the largest uninterrupted forest belt on the planet. A vast expanse of coniferous trees stretches from one shore to another. This cold forest is home to a number of dinosaurs that are adapted to feeding on conifer needles and cones, and to the dinosaurs that hunt them. Further south again, the centre of the continent, far from the sea. is a dry grassland grading into desert towards the barrier mountains. This is the domain of hardy animals like armoured dinosaurs.
Closer to the sea, by the gulfs and archipelagoes of the eastern and western shores, the climate is less extreme, being modified by the regular moist winds from the sea. Deciduous forests grow here, and these support numerous varieties of dinosaurs, pterosaurs, birds and small mammals.

Deciduous and mixed woodland

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GESTALT

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Formisaura delacasa

The most remarkable animal of the Palaearctic realm must be the gestalt. It is unique among the vertebrates because it pursues a communal existence. The gestalt evolved fairly recently, in the Ice Age, when there were few reptiles existing in the western portion of the continent and food was scarce. The animals that did survive there had to develop all kinds of strategies in order to make best use of the food available under the harsh circumstances. The gestalt evolved from one of the smaller pachycephalosaurs – the bone-headed dinosaurs – that lived in herds, mostly in mountainous areas.
The gestalt’s strategy was to delegate the breeding of the herd to one individual female, freeing the rest to become food gatherers. They developed the ability to build citadels to guard their hard-won food against other animals. Within this citadel the individuals adhere to a strict discipline and a hierarchy that is based on age and sex. Now that the Ice Age has passed, the gestalt has found that its evolved way of life is still very efficient and successful.
Among the pachycephalosaurs the armoured head developed as a display structure, particularly in the males. In the gestalt, the male still has a very specialized head, but it is not used for fighting or intimidating members of its own species. The armour has developed spines containing a lethal poison, now used when protecting the colony from predators.
In times of plenty the population tends to grow too big for the colony to sustain. Small groups of adult males and females then leave to start up new colonies. Streams in the temperate regions of the Nearctic continent may be marked by lines of the conical citadels.

The males are soldiers and have poison spines that grow outwards from the headshield (c). They stand guard at the nest entrances, warning of approaching danger by head-banging against the branches (d). Old males may come into breeding condition, shedding their spines (e), adopting a more subdued colour and living inside the nest with the queen. Breeding males are short-lived and are replaced every ten days or so.

The largest individual in the gestalt colony is the queen (a), almost a metre (3 ft) long and with a bloated body. She lays, on average, one egg per day all year round. Each egg hatches into a juvenile that is cared for by adult worker females that never leave the colony. When the juveniles, both male and female, reach an adolescent stage they work outside the nest. Adult females (b) eventually return to the nest and work as nursemaids. They are prevented from coming into a breeding condition by pheromones (chemical secretions) emitted by the queen. When the queen dies the pheromones stop and a new queen develops from one of the female workers. The female workers and the queen have very small eyes. They find their way about the gloom of the nest’s interior by means of sensory hairs growing from their shoulders.

The nest is built and kept in repair by the females. It is a thatched structure, built of twigs and straw, usually around a sloping tree trunk over a stream. The interior is a mass of tunnels and chambers and each nest usually has the same layout. The egg chamber (f) is near the apex where it will be warmed by the sun. The queen chamber (g) is directly below. The nursery chamber (h), where the hatchlings are tended is below that. The toilet area (i) is directly over the stream. The food store (j) is attached to the main trunk and there are up to six additional food stores (k) on other branches of the tree. Long sticks and saplings are woven into the structure to supply escape routes if the main entrance along the tree trunk is rendered impassable by attack or weather damage.

Deciduous and mixed woodland

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BRICKET

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Rubusaurus petasus

The deciduous woodlands of the Palaearctic realm are found mostly north of the mountains at the western end of the continent, where the continent narrows and few places are far from the sea. It is a region of high rainfall and temperate climate. There are four marked seasons: dormant winter; spring in which leaves and flowers appear; summer with the most vigorous growth; and autumn, which is a time of fruiting just before the trees lose their leaves for winter. The predominant trees are oaks, ashes and beech, below which is usually an understorey of smaller trees and a thick undergrowth.
A typical animal of this environment is the bricket, a small browsing hadrosaur, not dissimilar from its Cretaceous ancestors. In the Cretaceous period there were only the non-crested hadrosaurs living in this corner of the continent, but later the crested forms migrated here from further east - part of the great spread of the hadrosaurs over the northern continents. The bricket lives in small herds in the dense undergrowth and bramble thickets, usually resting during the day and feeding at dusk and at dawn. The expanded crest, found in both males and females, is both used as a display structure, particularly during the autumnal mating season, and as a deflecting device when it must move swiftly through the vegetation.

The long flat tail of the bricket is used both as a prop (a), when browsing from high branches, and as a warning flag (b) at times of danger. Stuck straight up in the air its bright colours warn the rest of the herd of approaching predators.

The bricket’s streamlined shape is ideal for fast movement through the tangles and thickets of the temperate woodlands. The shape of the crest (c) parts the vegetation as the animal runs, and the slim body allows it to pass between close-growing trees. The brownish colour camouflages the animal when motionless, but when it breaks cover and runs it can do so quickly, vanishing at speed into the depths of the forest.

Deciduous and mixed woodland

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ZWIM

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Naremys platycaudus

In outward appearance many of the mammals have changed little since they evolved from the mammal-like reptiles in Triassic times. Throughout the Jurassic, Cretaceous and Tertiary periods they have remained small, compact creatures, not adapting into any of the wide ranges of life styles occupied by the great reptiles. However, some of them have a number of interesting specializations.
The zwim is an aquatic, insect-eating mammal. It inhabits the streams and rivers of the Palaearctic realm and is particularly common in regions of deciduous forest. It has a length of about 30 centimetres (1 ft), most of which is taken up by a long flattened tail. The tail, and the long webbed hind feet, allow the animal complete freedom in the water. Its long sensitive snout is used for probing under stones and in dead vegetation for the insects and other invertebrates on which it feeds, both at the bottom of the stream and on land. It lives in burrows on the river banks and can defend itself against predatory reptiles and fish by biting with its sharp teeth. The saliva is venomous and any bite is quickly effective. The zwim is a social animal and as many as a dozen burrows can be found within a short distance from one another on heavily wooded river banks. Large numbers may congregate at the wallowing-pools of the bricket in order to feast on the parasites that are shed there.

The zwim is an active swimmer, thanks to its webbed hind feet and its flattened tail that works with a strong up and down undulation. The eye is large and it can adjust its focus to see both underwater and on land.

The coneater is an animal of small herds, each herd consisting of about a dozen individuals. Its body is insulated from the intense winter cold by deep folds and wrinkles of fat. Its beak can snip twigs and cones (a), and its tough food is ground up between batteries of grinding teeth at the back of the mouth.

The jinx usually hunts in pairs. A pair insinuate themselves into a herd of coneaters as they move through the forest (1). The jinx’s scent glands give off a smell similar to that of its quarry, aiding the disguise. Suddenly, when the herd least expects it, one jinx kills a coneater. The rest of the herd, including the other jinx, scatters (2). When they come-together again after the first panic passes (3), the second jinx attacks and also kills.

Coniferous forest

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CONEATER

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Strobofagus borealis

The coniferous forest of the Palaearctic realms is the largest area of unbroken forest on Earth. It stretches right across the continent along the sub-polar latitudes and, but for the narrow inlet of the sea, would be continuous with that of the northern Nearctic realm. It is bounded by the tundra to the north and the deciduous forests and cold grasslands to the south. The coniferous forests contain relatively few species, compared with other forests further south. The most common conifers are pines, firs, spruces and larches. These reproduce by means of seed-dispersing cones, and it is these cones that provide the food for most of the animal life of the region. Almost the only large animal found here is the coneater, a 3-metre-long (10 ft) hypsilophodont that resembles its Cretaceous ancestors.
The hypsilophodonts were a very widespread and successful group in Cretaceous times. Lightly built running animals, very much like small iguanodonts, they spread over all the continents before the end of the period. They have continued to be successful all over the world until the present day, occupying a large number of different niches. In the dark depths of the coniferous forest they run in small herds, over the soft undergrowth-free forest floor, and browse in more open country along the river banks. Although the coneater generally eats the cones and the seeds they contain, in winter it eats tree bark, needles, mosses and lichens, and seeks out stores of nuts hoarded by smaller animals.

Coniferous forest

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JINX

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Insinuosaurus strobofagoforme

There is not much to eat in the coniferous forest compared with the food available in other parts of the world. Hence there are fewer types of animals here, and each type is very highly adapted for its particular life style. Nowhere is this more evident than in the case of the jinx. The jinx eats coneaters, and nothing else. Its whole physiology has developed to aid this. Since the Cretaceous period, the most successful medium-sized carnivorous dinosaurs have been the dromaeosaurs and the saurornithoids. These are generally lightly built bipedal animals, about 3 metres long (10 ft), with long, stiff tails, which means they resemble hypsilophodonts in bodily shape. There are differences, of course, especially in the teeth and claws. Both the saurornithoids and dromaeosaurs have a large killing claw on the second toe, obliging them to walk on only their third and fourth toes. This is quite different from the three-toed arrangement of the feet of the hypsilophodonts. The long mouth conceals a battery of meat-shearing teeth. They have grasping hands but with only three fingers, compared with the five of the plant-eaters. The meat-eaters also lack the characteristic pot belly of the browsers. Nevertheless, the superficial resemblance is so close that one dromaeosaur, the jinx, has adopted a coloration that disguises it as a hypsilophodont and allows it to infiltrate the coneater herds. The deception is so successful that a herd of coneaters may travel for quite some distance without noticing the danger in its midst.

 

The tromble, a 3 metre (10 ft) high flightless bird, with legs as massive as tree-trunks, migrates in huge herds across the waterlogged landscape of the summer tundra above. Eggs are laid in temporary nests at the northernmost point of the migration, and they hatch very quickly with the young able to travel immediately.

 

The very large body of the tromble helps to retain its natural warmth. A large animal such as this has a small surface area compared to its bulk, and heat cannot escape easily. The thick coat of hair-like feathers helps the insulation, especially during the winters spent in the shelter of the coniferous forests to the south.

 

Tundra and alpine

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TROMBLE

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Gravornis borealis

To the north of the vast belt of coniferous forest that circles the northern hemisphere in the bleaker sections of the Palaearctic and Nearctic continents, the trees give way to a cold region of open landscapes called the tundra. Here the conditions are too tough even for the hardiest of trees, and the vegetation consists of short grasses, mosses and lichens. During the long northern winter, when the sun does not rise for weeks or months at a time, nothing grows. Then, when the bleary summer finally dawns, the winter snows melt away and all the plants grow frantically to best harness the short living season. Animals migrate northwards from the coniferous forests where they have wintered, to take advantage of the sudden harvest of food. They spend the summer months moving northwards, grazing as they go.
The largest animal to migrate in this fashion is the tromble, a massive flightless bird that evolved when the tundra regions appeared during the Ice Age. There are no dinosaurs this far north. Even though the dinosaurs developed a warm-blooded system that enabled them to survive a great range of climates, the chill tundra environment was still too extreme for them. The warm-blooded physiology of birds was much more efficient and therefore the birds were able to move into this harsh ecosystem. Several ground-dwelling birds evolved here since there were no terrestrial predators to threaten them.

The beak of the tromble is broad and hard, for cropping great mouthfuls of the coarse tundra vegetation. The food is ground up in the crop with the aid of swallowed stones. Fresh stones are available every year, brought to the tundra surface by frost. The mating season is early summer, when the males sprout bright yellow display plumes.

Several species of whiffle are found on the tundra, but they are all rather similar to one another. The body is round and the neck short, to minimize heat loss. Long slender legs enable it to wade in ponds, and the long beak, with the sensitive tip, can probe into mosses and under stones for insects.

 

 

Tundra and alpine

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WHIFFLE

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Adescator rotundus

Summer in the tundra reveals not only a rapid growth of plants, but a sudden flourishing of insects as well. Thick black clouds of flying creatures rise from the waters and hover like smoke over the tundra landscape. The mosses and lichens are, for a few short months, alive with scurrying beetles, springtails and mites. Such a harvest of food cannot fail to bring in flocks of insect-eating birds, and huge formations can be seen swooping and diving above the lakes and bogs in the summer.
One particular bird has abandoned its powers of flight, leaving the clouds of flying mosquitoes, midges and caddis flies for the airborne hunters, and has concentrated its feeding to the insect life on the ground. Large ground-scurrying flocks of whiffles follow the tromble herds, pecking here and there in the stunted vegetation with their long beaks. Through the weight of their passage, the trombles cause such a disturbance to the soil and moss, churning up the mud and crushing down the vegetation in deep footprints, that the insects that live there are sent scattering for new cover. The whiffles following behind are quick to snap them up. Each tromble, representing a huge mass of flesh, is prey to warble flies, fleas and all manner of other parasites which are also eaten by the whiffle flocks.

When asleep, the whiffle can draw its head into the hairy plumage of its body, and hide its sensitive beak among the narrow feathers of its chest. Like most tundra creatures, the tromble and the whiffle are found in the cold northern regions of both the Palaearctic and Nearctic realms.

Steppe and grassland

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TARANTER

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Herbasaurus armatus

In the windswept heartland of the Palaearctic continent, the continuous belt of coniferous forest is replaced to the south by cold grassland of mixed grasses and narrow-leaved flowering plants. At the forest edge the grasses are rooted in a rich black soil, but further south the soil is redder and drier. These grasslands are known as the steppe. Beyond the steppe a wilderness of drifting sand, hard-packed clay and shattered stone sweeps southwards to the foothills of the huge mountain chain that marks the southern limit of the Palaearctic realm.
The steppe grassland is home to many small seed-eating burrowing animals, particularly mammals. Their burrowing way of life keeps the soil churned up and aerated and prevents all the rich topsoil of the surface layers from being used up too quickly. In this way the plant-life is maintained. In the spring the steppe is a blaze of colour as the flowering plants come into bloom, while in summer the feathery seedheads of the grasses create a totally different landscape.
As in most of the great grasslands of the world, the steppe supports a variety of grazing animals, all of which have evolved since the Mesozoic era. The taranter has evolved from the ankylosaurs, such as Euoplocephalus and Saichania that became so plentiful at the end of the Cretaceous period. The ankylosaurs were divided into two groups. The first were quite lightly built and came to their peak early in Cretaceous times. The more advanced group were heavily built, with massive armour and a weapon on the end of the tail, and were successful after the first group began to decline. Most of the ankylosaurs that exist today are descended from the heavily armoured forms. They were always abundant in this part of the world and fossils reveal that they evolved into grazing animals as the grasslands developed. In the taranter the armour, developed from horn-covered bones set in the skin, has become a continuous covering for the back. This, and the bulbous shape of the body, help to prevent dessication in the dry winds.

Desert and desert scrub

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DEBARIL

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Harenacurrerus velocipes

The deserts of the southern edge of the Palaearctic realm are among the harshest environments on Earth. Vast expanses of sand, clay, rock and rubble are baked by a broiling sun during the day and frozen by cold at night. There are no barriers to the chilling winds that blow southwards from the northern icecap, or downwards from the mountain peaks in the south. Rainfall is infrequent and confined to spring and autumn. The vegetation is sparse and only appears when rain has fallen. Animals must be quite hardy to exist in such an environment, and most of the plant-eating creatures found here are cold-blooded. The slow metabolism of such herbivorous animals as tortoises and plant-eating lizards enables them to gorge themselves when the plants are available, and to sleep away the harsher times in burrows. Of the warm-blooded animals the mammals are most successful, avoiding the extreme conditions by being active only at dawn and dusk.
One of the few warm-blooded dinosaurs that live here is the diminutive debaril. In its life style and, to some extent, its appearance, it parallels the desert mammals. It is active at dawn and dusk, eats roots and seeds, conserves its water efficiently and burrows in the sand.

Ankylosaur armour, consisting of horn-covered bone, evolved as a defensive mechanism. In the taranter it has become more important as a means of conserving moisture. Hollows inside the skull are lined with damp membranes that moisten the dusty air as it is breathed in. Defensive armour is still present as horny spikes along the flanks and the heavy club on the tail.

The debaril, like most of the small, plant-eating modern dinosaurs, is descended from a hypsilophodont ornithopod. It is about 60 centimetres (2 ft) long and is well adapted to the extremes of its environment. Under cold conditions it hunches itself up to present a small surface area to the wind (a). The wrinkles in the skin bunch together to form an insulating coat. Heavy lids fold over the eye to prevent chilling. During cold conditions it moves in a series of bounds (b). When it is hot it stretches itself out (c), presenting a large surface area that is easily cooled, and travels by running on hind legs (d).

The head armour of the taranter is a horny covering that forms a grass-cutting beak along the edges of the broad mouth. Flat teeth in the back of the mouth grind up the plant food.

By settling down into a hollow and presenting its streamlined armoured surfaces to the wind the taranter can withstand the stinging sand and duststorms that are common in the area.