THE NEW DINOSAURS

The distribution of the continents and their environments in the world today is a legacy of the geological history of the planet, and of the current climatic zones. Each continent, or zoogeographic realm, has its own assemblage of wildlife. The particular group is determined by the flexibility of the boundaries to that realm, and by the past geological existence of those boundaries. During the Triassic and early Jurassic periods there was only one zoogeographic realm. The land areas of the world were united as part of the supercontinent of Pangaea and the same assemblage of animals was found everywhere. Since that time Pangaea has split up into individual continents, and remnants of the original fauna have developed independently in each continent. The animal life in a modern realm may be unique if the boundaries are precisely defined and impassable and have been so for tens of millions of years. On the other hand, the realm may reveal an assemblage that shares many species with its neighbouring realm, if the boundaries are ill-defined and easily crossed.
Upon the basic animal group in each zoogeographic realm are superimposed the environmental conditions. A single realm may contain tropical forests and deserts, chill tundra and ice-caps, and every environmental condition that would fall between. As these conditions are relatively new, having developed throughout the Tertiary period and especially since the Ice Age of the last two million years, the varieties of specialized animal on each realm have evolved from that realm’s original animal assemblage.
The dinosaurs and pterosaurs that developed and established themselves during the Triassic, Jurassic and Cretaceous periods have now developed into browsing, tropical forest types; running and grazing grassland types; burrowing desert types; hibernating temperate woodland types, and migrating coniferous forest types. The shapes of the creatures are quite different from those of the Triassic, Jurassic and Cretaceous periods, but they have all evolved from the same original reptile stock.
In the pages that follow we explore the world as it is today. We look at the different zoogeographic realms and see how the combination of geological and climatic changes has allowed the evolution of the huge array of different types of animals. We view the vast and wonderful variety of modern animal life, and in particular, the new dinosaurs.

THE ETHIOPIAN REALM

The continent that contains the Ethiopian realm is almost an island. Its broadest section lies north of the equator, where it stretches 7.000 kilometres (4,350 m) from east to west. South of the equator it narrows to about 3.000 kilometres (1.900 m) as it reaches to its rounded tip in the far south. From south to north the continent is about 7.000) kilometres (4,350 m) long. It is joined to the main northern continent only by a narrow isthmus in the north-east. The Ethiopian realm occupies the whole of this area except for a strip along the northern edge. The boundary that separates it from the Palaearctic realm in the north is the vast expanse of inhospitable desert that stretches across the continent’s widest portion.
The Ethiopian continent was once the central portion of the great southern supercontinent of Gondwana (see page 16). In Triassic times its north-western edge provided the join between Gondwana and the northern supercontinent called Laurasia, uniting the two in the all-encompasing supercontinent called Pangaea. These two supercontinents became separated during early Jurassic times, by an arm of the sea called the Tethys. Then Gondwana began to break up. The block that was to become the Ethiopian continent did not shake itself completely free from its neighbours until the late Cretaceous period, and since that time it has been moving northwards across the Tethys. The Tethys is gone now – closed up by the northward movement of the southern continents. A large island, about 1,200 kilometres (745 m) long, lies about 700 kilometres (430 m) away off the south-eastern coast. This is a mini-continent in itself – another fragment of Gondwana – and has been isolated for so long that it could constitute a tiny zoogeographic realm on its own. The most mountainous regions lie along the eastern edge of the continent. Here there are mountains that are so high that their summits are snow-covered all year round despite the fact that they lie almost on the equator. Along this edge the forces that tore Gondwana apart are still at work. A rift valley, formed by tension in the Earth’s crust, stretches from south to north and shows that the eastern part of the continent is pulling away. Earthquakes and volcanoes are common here, and at some time in the future the whole eastern section of the continent may drift out to join the other continental fragments that are scattered across the ocean to the east. At its northern end this rift valley is already submerged and has formed an inlet of the sea. Other mountains are found along the western coasts. These are the eastern edges of old rift valleys that appeared during the days of Gondwana when the continent began to rip itself away from the surrounding landmasses. The rest of the continent consists of flat river basins and plateaus.
The habitats of this realm are quite varied, and are arranged in a kind of concentric pattern. The central portion, covering the lowland areas through which the equator passes, swelters as a tropical rainforest. The prevailing winds bring constant rain to this hot area, and the water produces vast rivers that drain from the jungle basins into the sea. This is a zone of small tree-living animals, feasting on the myriad fruits and insects of the lush greenery.
To the north, south and east the forest grades into grasslands, where it is still hot, but the rain only falls for one season of the year. Trees do not do well under such conditions but grasses do, and open grasslands and sparsely wooded savanna sweep across the broadest part of the continent in the north, cover the foothills of the eastern mountains, and curve down to the southern hinterland. Long-legged grass-eaters live here, including some strange developments of flightless pterosaurs.
To the north and the south lie the deserts – harsh, hot and arid habitats. These are regions that lie along latitudes that receive only dry winds and little rain. The desert in the north, crossing the greatest width of the continent, is so inhospitable that it provides the barrier which effectively isolates the Ethiopian realm. The desert in the south is less extensive but no less antagonistic to life. Yet in the deserts there are animals – animals that have adapted to survive the waterless conditions. Here live tiny, legless, burrowing dinosaurs that have evolved to withstand the extreme killing conditions, and have gone on to be even more successful in less harsh environments.
The offshore island was once part of the same realm but must now be regarded as an individual environment. With tropical forest and open woodland it still supports the kind of animals that existed on ancient Gondwana before it shattered and scattered. Conditions there have not altered significantly since it became isolated and the animals have therefore not needed to adapt to a changing environment.

Tropical rainforest

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WASPEATER

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Vespaphaga parma

A whole range of tree-living dinosaurs evolved and established themselves in the branches and boughs of the world forest after the end of the Cretaceous period; they rapidly diversified into all kinds of different forms. About that time the social insects – the bees, wasps and ants – began to develop. These live in colonies, usually consisting of an egg-laying queen sustained and protected by an army of workers and soldiers.
The waspeaters were a specialized branch of the tree-dwellers known as the arbrosaurs, that developed at the same time and preyed upon the social insects. After the world forest was broken up by the changing climates and the spread of the grasslands halfway through the Tertiary period, the waspeaters became restricted to a number of tropical forest areas. Most species now live in the equatorial regions of the Ethiopian realm. Their long claws are an adaptation to a climbing way of life, and are also useful for ripping at wasps’ nests. Their scaly hide has grown into a roof of overlapping plates, impenetrable to the stings of the insects. Similar wasp-eating animals have evolved in the tropical forests of the Neotropical and Oriental realms. Many of these are related to the Ethiopian waspeater, having become isolated in the various tropical forest regions. Others, such as the pangaloon Filarmura tuburostra of the Neotropical forest (page 68) are only distantly related, and have evolved similar shapes by parallel evolution – the independent development in related animals of similar adaptations to allow them to follow similar lifestyles.

Most meat-eating dinosaurs have lost their collarbone. They do not need one since the forelimbs do not need to be particularly strong. One or two forms do possess this bone, however, and it is not clear whether their ancestors retained it from the time when they went about on four legs, or whether it ‘re-evolved’ having been first lost – a process known as secondary development. In Arbrosaurus and its relatives, the collarbone provides the anchorage for the very powerful arm muscles with which the animal can brachiate, or swing with an overarm action, through the branches of the trees.

The bones of the waspeater’s skull (a) have become fused into a narrow armoured tube that can penetrate deep into the nests of tree wasps. The strong hind legs and tail allow the animal to hang from the branch and reach into nests that have been built in awkward positions.

An arbrosaur, such as the tree hopper, is agile and perfectly at home in the trees, but is a very ungainly animal on the ground. When it is forced to, it can only move over the ground by a series of undignified leaps, keeping its long arms and heavy tail well up out of the way.

An arbrosaur’s tail is a stiff, straight rod. It uses it for balance when leaping about among the trees. The long claws on the three main toes and the three fingers are useful both for finding purchase on branches and for ripping up bark for insects.

Tropical rainforest

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TREE HOPPER

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Arbrosaurus bernardi

One of the most widespread developments in the dinosaurs after the end of the Cretaceous period was the evolution of the arbrosaurs. These evolved from the small coelurosaur theropods – the lightly built running flesh-eating dinosaurs. In Jurassic times the coelurosaurs gave rise to the birds, and the development of the arbrosaurs from the same stock was brought about by similar evolutionary processes. Perhaps the most typical of the modern arbrosaurs is Arbrosaurus itself. Various species of this animal appear in all the zoogeographical realms.
The main feature that distinguishes the arbrosaurs from other coelurosaurs is the presence of a strong collarbone. In another coelurosaur offshoot, retention of the collarbone allowed for the development of strong flight muscles and paved the way for the evolution of the birds. In the case of the arbrosaurs the collar girdle provides support for the strong arms which are used for climbing and swinging about among the branches. Its endothermic (warm-blooded) physiology enables it to pursue an active hunting life style. Its skull shows adaptations for this, with the big brain box, the eye-sockets directed forwards giving stereoscopic vision, and the narrow, finely toothed jaws - ideal for winkling insects out of crannies in tree-bark.

The lank runs with a pacing motion – both legs at the same side moving in the same direction at the same time. This prevents the long legs from becoming entangled.

Tall grass savanna

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LANK

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Herbafagus longicollum

The tropical grasslands, when they developed and spread halfway through the Tertiary, were a totally novel environment for the great reptiles. Grass is a remarkably tough substance, and a grass-eating animal needs a number of extreme specializations to allow it to survive. Grass is full of hard silica and so it causes a great deal of wear to teeth. A grass-eating animal needs teeth that are constantly growing or frequently replaced. Complex digestive systems are needed to break down and extract nutrients from the substance of grass. On top of all that, a big grassland-living animal needs to have long legs to allow it to run away from danger. In some places, such as the prairies of the Nearctic realm, dinosaurs developed quite happily into grass-eating forms. However, on the savannas of the Ethiopian realm, dinosaurs were not able to establish a foothold. They were beaten to it by their cousins – the pterosaurs. A group of pterosaurs abandoned their powers of flight as soon as the tropical grasslands spread, and they became the main grass-eating animals of the Ethiopian realm. The lank is now the most highly specialized of these, and the one that has become most unlike its flying ancestor. The body has remained short but the forelimbs and hind limbs have become long and equal in length. The neck and face are also long – all plains-living features.

Short grass savanna

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FLARP

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Vexillala robusta

Another of the ground-dwelling pterosaurs of the Ethiopian savanna is the flarp. Its specializations are not so extreme as those of the lank, and its flying ancestry is still evident from the presence of vestigial wings on its forelimbs. It can be thought of as an intermediate evolutionary stage between a conventional flying pterosaur and something as specialized as the lank. Although it lives in the same environment as the lank the two animals do not compete for the same food. Being much smaller, only about a metre (3 ft) high at the shoulder compared to the lank’s head height of 3—4 metres (10—13 ft), it feeds closer to the roots of the plants. The lank tends to graze the tops of the grass heads and leaves. The flarp’s sharp teeth at the front of the mouth enable it to root about among the plants at ground level. It has fleshy lips and copious cheek pouches enabling it to chew the grass and plants thoroughly before swallowing. After digesting for a while in the stomach the grass is brought up again for more chewing before being swallowed for a final time. In this way nutrients are efficiently extracted from the plants. The flarp runs about the plains in small flocks of about a dozen and can often be seen displaying their brightly patterned wings, or squatting down in the grass in groups during the heat of the day and chewing over the morning’s meal.

The long face of the lank means that its eyes are still above the level of the grass even when its snout is grazing at the grass roots. It can thus keep an eye open for danger. On the open plains danger can be seen coming from afar, and the lank’s long legs give it the speed needed to escape from predators.

The structure of the flarp’s forelimb and hand is similar to that of a flying pterosaur. The fourth finger is long and supports a flap of skin - the vestige of the flying wing. Now the wing flap is used for display – for attracting mates or for warning rivals. The fourth finger and the flap are normally held hack out of the way (a), but when displaying they arc-extended and the bright patterns are shown (b). This display is accompanied by raucous screeches that carry for great distances across the plains. Flarps feed on plants and grasses that grow close to the ground. They have short, sharp teeth positioned at the front of the mouth (с).

Desert and desert scrub

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SANDLE

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Fususaurus foderus

Hot deserts are found along the latitudes of the tropics, where air that has risen and lost its moisture at the equator descends and settles dryly over the land. In the Ethiopian realm the deserts are found in the south-west corner of the continent, and all across the north. The northern desert is so vast and inhospitable that it provides the boundary between the Ethiopian and the Palaearctic realms. Nevertheless, despite the harsh conditions, there are some animals that do live here. The coelurosaurs have proved to be adaptable enough to develop forms that are uniquely suited to such an environment – forms such as the sandle and the wyrm.
The days are so hot and the nights so cold that any animal must spend much of its time protected from the extremes. The sandle does this by burrowing in the sand. Its streamlined spindle shape is ideal for a burrowing way of life, since sand grains slide past its smooth contours easily as it tunnels through the dunes, digging and pushing with its stumpy legs. The eyes and nostrils are high up on the head, enabling it to see about and breathe while the rest of the body is buried. Desert animals need to be very careful about water conservation. The sandle never drinks but obtains water from the moist flesh of the animals it eats. Its kidneys are very efficient, allowing almost all the moisture to be retained, and secreting any poisonous compounds in a saliva that helps to paralyze and subdue its prey.

Desert and desert scrub

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WYRM

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Vermisaurus perdebracchius

Like the sandle, the wyrm is a streamlined animal adapted to a burrowing existence. It has also evolved from the lightly built coelurosaurs of the Cretaceous period. Its streamlining takes the form of a great elongation of the body and neck and the total loss of the forelimbs. Its head is trowel-shaped and used to force a path through the sand. There it moves by undulations of the long body and by thrusting with a swimming motion of the broad hind feet.
There are many species of wyrm, not all of which have continued to be burrowers. Many live in the burrows of other animals, such as the small desert mammals. Many others have spread into different habitats and different zoogeographical realms around the world. The long sinuous form that first evolved as a burrowing mechanism has applications in other ways of life. There are swimming wyrms in various parts of the globe and a whole range of tree-living wyrms, especially in the Oriental realm (page 84). The wyrms of the desert of the northern Ethiopian realm, where they first evolved, are still burrowing animals, and hunt small mammals and reptiles usually at dusk and at dawn. Like the sandle they obtain all their moisture from the flesh of their prey, who in turn obtain all theirs from the scrubby desert plants and seeds that they eat. They make very efficient use of their water despite the fact that they have only one kidney, the other having been lost as the narrow shape evolved.

The sandle has come a long way, in evolutionary terms, from the agile bipedal, long-tailed coelurosaur that was its ancestor. The body has become streamlined and covered in smooth fur. The clutching hands on the forelimbs and the strong running hind legs have become digging shovels. The scaly head is flat and chisel-shaped, ideal for thrusting its way through the sand as the tough scales prevent abrasion.

The wyrm is long enough and narrow enough and agile enough to chase its prey down their burrows. Its diet consists mostly of the small hopping mammals that have evolved to live in the desert.

Tropical rainforest —offshore island

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MEGALOSAUR

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Megalosaurus modernus

The boughs and evergreen leaves of the tropical forest filter the sunlight into fine steamy beams that throw a dappled pattern down into the gloom of the jungle floor. This is the domain of the brightly coloured birds, the pterosaurs, with their larger wings, being banished to the more open spaces above. Suddenly the raucous chattering of the birds is hushed, and a deep still silence falls in the shadowy forest. The birds have sensed something dangerous. The light patterns ply upon the leathery surface of something dark and indistinct in the sparse undergrowth. With a gasp of air from cavernous lungs, a huge animal rises to its hind feet, pushing itself up on massive legs, steadying itself with clawed forefeet. The great eyes, gummy after sleep and torpor, blink and look around. The huge head contains only enough intelligence to tell the megalosaur that it is hungry again. Slowly it crushes its way through the shadows to the decaying corpse of a plant-eater, scattering the scavenging birds and mammals, and resumes the meal that it abandoned days before.
Leathery skin? Low intelligence? It is as if time had been turned back to the Mesozoic period when the most important meat-eating dinosaurs were the vast lumbering carnosaurs.
The huge island that the megalosaur inhabits lies off the east coast of the Ethiopian continent. Much of the geographical and climatic changes that affected the rest of the world have passed this island by, and there has been little impetus for evolutionary change. This island is almost a time capsule, revealing what animal life was like on Gondwana hundreds of millions of years ago. The biggest predator of the island is the megalosaur. It is a different species of megalosaur from that which inhabited Gondwana in Jurassic times, but it is still a large and active predator, about 8 to 10 metres (27 – 33 ft) long, that prowls through the forests, sometimes singly and sometimes in packs, hunting the large plant-eaters of the island. As it grows older and slower it lives as a solitary scavenger, devouring the corpses of already dead animals and the remains of the kills of younger megalosaurs.

The skull of the modern titanosaur is almost identical to that of its ancestor of Jurassic and Cretaceous times. It has a steeply sloping face with nostrils at the top of the head and an array of peg-like teeth confined to the front of the mouth. The titanosaur does not chew but merely crops off its food and passes it down to be treated in its gizzard and its stomach.

The extremely long tail of the titanosaur is strong and muscular, and can he used as a whiplash to inflict a severe blow upon an enemy.

Off the east coast of the Ethiopian continent, about 400 kilometres (248 m) out, lies a very large island, 1,300 kilometres (800 m) long, 600 kilometres (370 m) wide, it is a little continent and zoogeographic realm of its own. Since it broke away from Gondwana (a), 145 million years ago, the island has remained relatively stationary and at the same latitude (b). The original animal life has not evolved dramatically, as conditions there have been fairly constant, and much of the island is covered with the same forest that existed there in Jurassic times.

Dry open woodland – offshore island

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TITANOSAUR

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Altosaurus maximus

As the climate and vegetation on the offshore island changed little over the 145 million years since it became isolated, the animals that ate the vegetation did not need to change either. The large sauropod dinosaurs - the long-necked plant-eaters - have remained practically unaltered over that period of time. The largest is the titanosaur that reaches a length of about 18 metres (60 ft) and can reach up to heights of 6 metres (20 ft) to browse from the tops of trees. The body is heavy and supported on stout pillar-like legs. The vertebrae of the neck, body and tail are partially hollowed out to cut down on the weight. The tail is usually carried clear of the ground and ends in a whiplash with which it can defend itself against enemies, such as the megalosaurs. Titanosaurs usually travel through the forests in large family groups, browsing constantly from the trees. The continual chewing of new shoots and buds results in trees on this island having naked trunks rising to a height of about 6 metres (20 ft) before the branches start growing. The food is not chewed but passed down into a voluminous gizzard. There it is ground up by stones that are occasionally swallowed by the animal. From there the food passes into the stomach where it is broken down by bacterial action. The gizzard stones wear away quickly and the worn ones are often vomited up and replaced by fresh ones. The soil of the island is littered with small conical heaps of these rounded, discarded stones. There were many families of sauropod in Jurassic times but it is now only the titanosaurs that survive, and these are found in the Neotropical and Oriental realms as well as on the island – all fragments of the ancient continent of Gondwana.

The classic shape of a carnosaur – one of the large flesh-eating theropod dinosaurs – is retained in the megalosaur. Its sharp teeth and the powerful claws on the forelimbs are used for holding prey and tearing it up. The actual killing is done with great talons on the hind feet. As it walks the heavy head is held out at the front, balanced by the long heavy tail behind.

Shoreline – ocean islands

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DWARF MEGALOSAUR

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Megalosaurus nanus

Black and white seabirds flock along the tidemark on the silvery sand, pecking at the seaweed and the dead animals washed up and left by the ocean. Other more adventurous birds strut about in the dry sand near the fringe of curving palm trees at the head of the beach. They are being watched from the ridge of red granite that sweeps down from the hilly interior of the island and protrudes as a headland at one end of the beach. Suddenly, from the rounded rocks, a sleek green and orange shape darts out onto the dazzling sand and, in a burst and flurry of feathers, one of the more foolhardy birds is caught and killed. The hunter is a tiny megalosaur, similar to that found on the great island 1,000 kilometres (620 m) to the south. It is only about 3 metres (10 ft) long. It picks up its prey and carries it back to eat in peace in the darkness beneath the palms. As Gondwana ripped itself apart and the continents that were to become the Ethiopian and Oriental realms drifted away from one another, many fragments of continental material were left scattered across the ocean in between. One particular fragment is crescent-shaped, about 1,000 kilometres (620 m) long and is almost totally submerged, but its granite mountain peaks protrude as a scatter of islands about 1,000 kilometres (620 m) to the north-east of the island of megalosaurs and titanosaurs. Here again the animals are remnants of the old Gondwana fauna, but they are somewhat different, having evolved to cope with new conditions. On a small island there is not quite so much to eat, and the food is found in a much more limited area. Dwarf forms of animals evolve as the only types that are able to survive the more stringent conditions.
The dwarf megalosaur has the appearance of one of the lightly built coelurosaurs, rather than one of the big carnosaurs. It preys on dwarf versions of the plant-eating dinosaurs, but its light build makes it agile and swift, and it can pursue fast-moving creatures, such as the seabirds that flock along the white palm-fringed beaches of the islands.

 

 

 

 

 

The dwarf titanosaur is very like its large relatives. The main differences are in the slimness of the legs, the weak appearance of the neck, and the shortness of the tail. Like its relatives, it eats forest vegetation which it grinds up in its gizzard with the aid of stomach stones.
There are several islands in the group, and the four largest support different species of dwarf titanosaur. These differ from one another very slightly – a reflection of their diets.

The dwarf megalosaur is a very agile and nimble animal. It usually hunts singly and can prey on the many seabirds that feed in flocks along the tideline. The megalosaur is athletic enough to sprint along the beach and snatch the birds out of the air as they flutter in panic into the sky.

Temperate forest – ocean islands

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DWARF TITANOSAUR

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Virgultasaurus minimus

The amount of plants available on an island leads to restrictions in the sizes of the plant-eating animals. Dwarf titanosaurs live among the coconut palms of the seashore and in the ferny undergrowth beneath the oaks and pines further inland. They feed on the undergrowth and the leaves of the low-growing vegetation. Unlike their larger relatives, the dwarf titanosaur is not a gregarious animal. It lives in small groups of two or three rather than in large herds. The group can move quite quickly through the thickets, long necks waving, when faced with an agile predator like the dwarf megalosaur. The body of the dwarf titanosaur needs smaller legs to support it, but the head is as large as that of a conventional titanosaur, and so it looks proportionally large. Dwarf animals are not unique to these islands. Dwarf forms of other large animals live on other islands in the oceans of the world, where a group of animals has become separated from the mainland population. It often happens that the isolated population has no meat-eaters among its numbers. Under these circumstances small and swiftly moving plant-eating animals may develop into large slow-moving forms, there being no need for speed to escape danger. On an island, therefore, there may be dwarf species of large animals, living beside giant species of small animals.

 

 

 

 

 

The dwarf species of the plant-eaters (a) are only about a fifth of the length of the full-sized forms. The dwarf meat-eaters (b) are relatively larger, being about one third of the size of the larger species. The meat-eaters are less restricted in the amount of food available as they also prey on sea birds.