Order Cetacea

The whales, dolphins and porpoises, sea creatures of magnificence and intelligence, are members of the only mammal order that have become thoroughly adapted to living their whole lives in the open oceans. The most specialized of all mammals, their sleek, streamlined bodies and fishlike shape allow them to swim with ease, but deny them any kind of life on land. However, they have retained the basic mammalian features of warm-bloodedness, the ability to suckle their young and the necessity to...

From Mammallike Reptile To Mammal

AN ADVANCED MAMMAL LIKE REPTILE (Thrinaxodon) Thrinaxodon walked like a mammal, with its legs directly beneath its body. Its teeth and jaws were powerful, with a high coronoid process on the lower jaw for strong muscle attachment. The rib cage was probably closed off by a muscular diaphragm, which allowed the lungs to expand and contract for efficient breathing. Dentary (lower jaw) Synapsid opening A mammal's strong, biting jaws resulted from progressive changes in the skull and lower jaws of...

Infraorder Prosauropoda

Like the theropods, the sauropodomorphs can be grouped according to their size. There were gigantic types, with long necks and tails, placed in the Infraorder Sauropoda (see pp. 126-133). Apatosaurus (previously known as Brontosaurus) is the most famous sauro-pod (see p. 132). These gentle, plant-eating giants lived throughout the Jurassic and Cretaceous periods, and then met a similar fate to all other dinosaurs mass-extinction. There were also smaller sauropodomorphs (though some were still...

Hesperornithiformes

This Cretaceous group of toothed birds were specialized diving seabirds that had lost the power of flight. Although they had a well-developed sternum, the keel was reduced, and the wings had degenerated. These birds seem to have fished the shallow waters that covered much of central North America during Cretaceous times, and would have nested on low shores. name Hesperornis regalis time Late Cretaceous locality North America (Kansas) size 6 ft 1.8 m tall This large, flightless bird differed...

Time Late Miocene to Early

Pleistocene locality North America (Nebraska) size 2 ft 6 in 80 cm long Osteoborus was a member of the borophagines, a group of scavenging dogs that first appeared in the Late Miocene, about 8 million years ago. Its heavy build and swollen forehead made it look rather bearlike, but its hyenalike habits were partly reflected in the huge, bone-crushing premolar teeth lining its jaws. Its skull was shortened to accommodate the massive muscles needed to work the powerful jaws, which enabled it to...

Family Arctocyonidae

This is the earliest and most primitive family of the order, and may be close to the ancestors of the later hoofed animals. Arctocyonids were mostly short-limbed, rather clumsily-built animals, up to the size of small bears. This agile climbing animal may have scampered about in the tropical forests of Early Tertiary North America, sniffing out and eating insects, small animals and fruit. It had powerful limbs, versatile joints and a semi-prehensile tail. Chriacus had plantigrade feet the full...

Order Carnivora

Cats, civets and mongooses, dogs, bears and pandas, stoats, weasels and otters, seals, sealions and walruses all these mammals belong to the order Carnivora (see pp. 194-195). They are all carnivores, meaning meat-eaters, and they all share a common feature relating to their teeth. Living carnivores have (or their ancestors had) a pair of meat-shearing teeth, called carnassial teeth, which are specialized for slicing flesh. Some members of the Carnivora, such as seals, have lost these teeth,...

Family Placodontidae

This group of semi-aquatic reptiles were equally at home walking along the seashore or swimming in the coastal shallows. Both areas provided them with rich feeding grounds for their preferred diet of shellfish, which were crushed between the broad teeth. name Placodus time Early to Middle Triassic locality Europe (Alps) size 6 ft 6 in 2 m long The skull of Placodus shows that this reptile was a specialized feeder. Its teeth were fully adapted to a shellfish diet. An array of blunt teeth...

Order Leptictida

The leptictids were one of many primitive groups of shrewlike mammals known from the Late Cretaceous, about 70 million years ago. They became prolific during the early part of the Tertiary and were widespread animals, appearing in North America, Asia, Africa and Europe. name Leptictidium time Middle Eocene locality Europe (Germany) size 2 ft 6 in 75 cm long Leptictidium probably resembled the modern elephant shrew, except for its longer hind legs and tail. It was a bipedal runner, like humans...

Family Argyrolagidae

This family consists of animals very similar to the kangaroo rats and jerboas of today, but are completely unrelated to them. Like such rodents they may have lived in deserts and been mostly nocturnal animals. They would have moved swiftly over the open ground by a series of prodigious leaps, and fed on the shoots and roots of desert plants. name Argyrolagus time Late Miocene to Late Pliocene locality South America (Patagonia) size 16 in 40 cm long Just like modern kangaroo rats and other...

Hesperocyon

Led to the rapid evolution of swift-footed hunters such as dogs. There were still 5 toes on each of Cynodesmus' feet, although the first toes were smaller than the rest. Its claws were narrow and partially retractable, like those of a cat, rather than the thick, blunt, weight-bearing structures that developed in later dogs. It was probably Cynodesmus' habit to ambush its prey, cat-style, rather than running it down, dog-style. name Cerdocyon time Pleistocene locality South America (Argentina)...

Family Amphicyonidae

The amphicyonids were a family of bear-dogs that existed from Eocene to Miocene times, between about 50 million and 5 million years ago. A varied and successful group of large hunters, they spread throughout Europe, Asia, Africa and North America. They replaced the creodonts when they declined, and were themselves replaced by the true dogs during the Pliocene. Their common name bear-dogs refers to their similarity to both creatures. The body was bearlike in shape and bulk, and they walked with...

Family Hyaenidae

The hyenas, also members of the order Carn vora, appeared only relatively recently, in Mid-Miocene times, about 15 million years ago. They probably evolved on the African continent, and then spread throughout the Old World. The only hyena known from the New World is Ch.asmaporth.etes, which lived in North America during the Pleistocene. It also lived throughout Africa, Asia and Europe. It was a fast-running hunter rather than a scavenger, and its legs and teeth were similar to those of the...

The missing link controversy

Archaeopteryx makes an ideal link between the reptiles and the birds, and it is therefore a major piece of evidence for the theory of evolution. Its importance was recognized when the first specimen was discovered, in 1861, only a few years after Darwin had published his theory of evolution by natural selection. Archaeopteryx has, therefore, always been a particular target of attack for those who do not favor the theory that living organisms have undergone gradual evolutionary change. For...

Families Mylodontidae Megatheriidae And Megalonychidae

Today's tree sloths of Central and South America look and behave quite differently from their ancestors, the extinct ground sloths. Many of these creatures were so large that they could never have climbed trees, and so were permanently grounded. One of the largest, Mega-therium, was some 10 times bigger than its living relatives. Ground sloths were slow-moving creatures and strict vegetarians. They appeared in the Early Oligocene, some 35 million years ago, and survived up to recent times. name...

Order Proboscidea

The African and Indian elephants are the only 2 surviving species of a once diverse and widespread group. Proboscids evolved from a basal stock of primitive hoofed animals that also gave rise to the modern hyraxes (see pp. 262-265) and the aquatic sirenians (the dugongs and manatees see pp. 226-229). From their origins in northern India in the Eocene as pig-sized creatures without tusks or trunks, pro-boscids had evolved by Pliocene times, 50 million years later, into giants that had spread...

Order Anseriformes

The ancestors of today's waterfowl the ducks, geese and swans belong to this order. They diverged from other birds early in the Cretaceous. One family, the presbyornithids, evolved into long-legged wading birds (below). name Presbyornis pervetus time Late Cretaceous to Early Eocene locality Europe (England), North America (Utah and Wyoming) and South America (Patagonia) size 3 ft 3 in 1 m tall Presbyornis was a typical member of its family a long-legged, long-necked bird, so slenderly built...

Family Pelomedusidae

These aquatic turtles were the most prolific of all the pleurodires during Late Cretaceous and Early Tertiary times. There are only 19 living species in the rivers and lakes of tropical Africa, Madagascar and South America. name Stupendemys time Early Pliocene locality South America (Venezuela) size 6 ft 6 in 2 m long This turtle, extinct for some 3 million years, was a giant among the pleurodires in fact, it was the largest freshwater turtle that has ever existed. None of its modern relatives...

Family Testudinidae

Modern land tortoises belong to this family, the most successful of the cryptodires. They appeared in modern form during the Eocene, some 50 million years ago, and have remained practically unchanged since then. All tortoises have high, domed shells to accommodate the capacious gut needed to digest their plant food. The shell also offers complete protection, since the animal can withdraw its head and elephantine legs inside. name Testudo atlas time Pleistocene locality Asia (India) size up to 8...

Family Nodosauridae

The nodosaurs were the earlier and more primitive of the 2 families of ankylosaur, and ranged throughout the Cretaceous period. Some paleontologists think that they may have evolved in Europe during the Late Jurassic, and then spread to the other northern continents. Some types at least also reached the southern hemisphere iMinmi is a recent discovery from Australia. Nodosaurs had narrow skulls, longer than they were wide. Solid, bony plates covered the body from neck to tail, and long spikes...

How Animals Are Classified

Animals are classified in groups of decreasing diversity. The smallest unit of classification is the species. Species that share several common characteristics are grouped together into genera, genera into families, and so on. The largest group, the animal kingdom, embraces animals of all kinds, including trilobites and other creatures without backbones. The diagram shows the classification of the imperial mammoth (Mammuthus imperator). Mammuthus imperator (imperial mammoth) Mammuthus...

Family Protoceratopidae

The protoceratopids constitute the family of early, primitive horned dinosaurs, although only some of them had horns. They evolved in Asia, in the same region as the parrot dinosaurs (from which stock they probably evolved), but lived there many millions of years later, in the Late Cretaceous period. They also spread to western North America. Like the parrot dinosaurs, the protoceratopids could walk upright, although they probably spent most of their time browsing on all-fours, and only rose up...

Locality North America Alberta

And Montana) size 17ft 5.2 m long One of the most spectacular of the short-frilled family of horned dinosaurs was the well-armed Styracosaurus. It had an enormous, straight horn on its snout, directed upward and forward. Two smaller horns grew above the eyes. The remarkable neck frill, like an oriental dancer's head-dress, had six main spikes arrayed around its top, some as large as the nose horn, and a number of smaller spikes made up a defensive fringe. As in other short-frilled ceratopids,...

Suborder Moeritherioidea

The name moerothere is derived from the word Moeris an ancient Greek name for the lake in Egypt's Fayum province where its remains were found. In Eocene and Oligocene times, this area would have consisted of fertile, forested coastal plains. time Late Eocene to Early Oligocene Senegal) size 2 ft 60 cm high This pig-sized, low-slung animal resembled a tapir or a pygmy hippopotamus more than an elephant. The external nostrils were at the front of the skull, which implies that it did not even...

Order Primates

The primates are a very ancient group of mammals, known from Late Cretaceous times, as long as 70 million years ago. The more advanced members are dealt with on pp. 286-297, but a primitive form is described here for comparison with contemporary mammals. The family Paromomyidae consisted of small creatures like tree shrews, which may have been the ancestors of the later lemurs, monkeys and apes. However, some paleontologists do not regard them as members of the primate order at all, but place...

Order Notoungulata

The notoungulates literally southern hoofed animals were the largest order of South American ungulates. There are about 100 genera grouped into 4 suborders. The suborders may already have diverged by the time South America was detached from North America at the end of the Paleocene. The isolation of South America allowed the separate evolution of its mammal groups, many of which diversified into ecological niches taken, elsewhere in the world, by other groups. Many notoungulates were small...

Family Chalicotheriidae

Whereas the rest of the ungulates have hooves on their toes, these animals evolved large claws instead and evidently could not run. The dentition and other features of some of the advanced chalicotheres, such as Chalicotherium from the Miocene of Europe, suggests that they were forest browsers, and may have been able to rear up on their hind legs while feeding on the succulent leaves of trees and shrubs. Although fossil evidence is sparse, chalicotheres seem to have been a remarkably successful...

Family Procyonidae

The procyonids, including the modern raccoons, pandas and coatis, first appeared in the Early Oligocene, about 35 million years ago. They had the typical meat-shearing blades on their premolar and molar teeth, the characteristic feature of the true carnivores. But this design has been lost in modern members, and their premolars and molars have reverted to a purely grinding and crushing function. This dentition suits the omnivorous diet of most modern procyonids. However, the diet of the giant...

Family Stegosauridae

All the familiar stegosaurs belong to this family, including Stegosaurus itself. They evolved in Mid-Jurassic times, some 170 million years ago, and reached their peak of diversity by the end of that period. They spread through western North America, western Europe, East Asia and East Africa. By Early Cretaceous times, the group had started to decline, although some species may well have survived in isolated pockets until the end of the Cretaceous. name Stegosaurus time Late Jurassic Oklahoma,...

Subclass Actinopterygii

The ray-finned actinopterygians were the earliest bony fishes to appear. A great diversity, first of marine and then of freshwater types, evolved some 400 million years ago. Today, this ancient group lives on in the vast and varied assemblage of modern teleosts, as well as in the much rarer representatives the sturgeons, paddlefishes, bowfin, gar-pike and birchirs. The characteristic feature of all the actinopterygians, both fossil and modern, is the skeleton of parallel bony rays that supports...

Order Osteolepiformes

The osteolepiforms were the longest-lived group of rhipidistian fishes. They appeared in the Early Devonian and died out during the Early Permian, a span of some 130 million years. Many paleontologists are convinced that these rhipidistians were the ancestors of the amphibians (see p. 48). name Osteolepis time Middle Devonian locality Antarctica, Asia (India and Iran) and Europe (Latvian SSR and Scotland) size 8 in 20 cm long This early member of the osteolepiforms was encased in thick, square

Family Manidae

The sole family in the Order Pholidota, these are the pangolins curious mammals covered in scales made of densely fused hairs, which give them the appearance of giant animated pine cones. They have stout limbs adapted for digging. Pangolins are often grouped together with the anteaters and armadillos because of their similar lifestyle they feed largely on ants and termites. However, this is probably an arrangement of convenience rather than a reflection of any close relationship. The extreme...

Infraclass Metatheria

The two major subgroups of the subclass Theria the Metatheria and Eu-theria diverged from a common ancestor early in the Cretaceous. The Metatheria contains only one order, the Marsupialia, or pouched mammals. This group is dealt with in detail on pp. 202-205, but a primitive member is described here as a comparison with other primitive mammals. New Mexico) size 1 ft 30 cm long Primitive marsupials such as Alphadon were probably very similar to modern opossums. They were omnivores, and ate a...

Subclass Prototheria

The most primitive mammals belong to this group of first mammals. They evolved from the cynodonts, a group of synapsid reptiles (see p. 192), during the late Triassic, some 220 million years ago. The only surviving prototherians are the monotremes the echidnas, or spiny anteaters, and the duck-billed platypus, all of which are found only in Australasia. The reproductive method of the monotremes reflects their reptilian ancestry they all lay eggs. However, the newly hatched young then suckle...

Desmatophcci

Name Desmatophoca time Middle Miocene locality Asia (Japan) and North America (California and Oregon) size 5 ft 6 in 1.7 m long The typical streamlined shape of the modern sealion had begun to appear with Desmatophoca. As in its living relatives, its forelimbs were stronger than the hindlimbs, and the feet were modified to form paddles, with the fingers elongated, splayed out and held together by webs of skin to produce a large surface area for swimming. All the bones in the limbs were...

Order Chelonia

Turtles, tortoises and terrapins are the only surviving members of this ancient group of reptiles, the chelonians. They differ from all other reptiles in having their bodies, except for the head, tail and legs, enclosed within a shell, above and below. Many of them can pull their heads and legs into the shell for total protection. Even the earliest chelonians, dating from the Late Triassic, had a shell in fact, today's turtles and tortoises have hardly changed since those times, over 200...

Family Diplodocidae

Diplodocids were sauropod dinosaurs with enormously long necks and even longer tails. Their bodies and limbs were slender, and their heads tiny. But despite their great length, these giant plant-eaters were lightweights in comparison to their relatives, the bulky brachiosaurs (see pp. 128-129). This was because the vertebrae of diplodocids had been reduced to a complex latticework of bony struts, designed to save weight, yet take maximum stress. The diplodocid family thrived worldwide during...

Order Ichthyostegalia

The ichthyostegalians are the earliest-known amphibians and the first labyrinthodonts to evolve. Their remains have been found only in eastern Greenland in rocks of Late Devonian age. name Ichthyostega time Late Devonian locality Greenland size 3 ft 3 in 1 m long Ichthyostega is the earliest well-known amphibian. It was a large, semi-aquatic animal, larger than any of its fish ancestors, with a long, deep body and a heavy skull of solid bone (see p. 48). Its 4 limbs, each with 5 toes, splayed...

Family Macropodidae

The most familiar of the modern marsupials, the kangaroos and wallabies, are included in the family Macropodidae. name Procoptodon time Pleistocene locality Australia size 10 ft 3 m long Extinct kangaroos tended to be larger than modern forms, and had some different features. Procoptodon was the largest of these, and was distinctive because of the short face and the fact that each hindfoot had only a single long, functional toe (the fourth), with mere nailless stumps on either side. Procoptodon...

Suborder Mysticeti

The mysticetes, or baleen whales, are first known from marine rocks in New Zealand dating from Early Oligocene times, some 35 million years ago. Only 8 genera survive today, and most are under severe threat from hunting. Baleen whales have evolved a unique method of feeding on the tiny, shrimplike animals in the plankton. They have no teeth in their jaws. Instead, great plates of a fibrous, horny substance, known as whalebone or baleen, hang from their upper jaws on either side. These baleen...

Family Canidae

The canids including the modern foxes, jackals, coyotes, wolves and dogs are a successful group of all-rounders. With an evolutionary history of some 40 million years, they have become adapted to a great range of habitats and a variety of diets. As members of the order Carnivora (see p. 216), they are related to the otters and weasels, cats and mongooses, and to the seals, sealions and walruses. First known from Late Eocene times, about 40 million years ago, the earliest canids were relatively...

Dlophosaui

Found actually attached to the skull, but lying nearby, so there is a certain amount of educated guesswork about their position in life. The jaws of Dilophosaurus give a clue to its lifestyle. The lower jaw was strong and full of long, sharp, thin teeth. The upper jaw had a cluster of teeth at the front, separate from the rest of the teeth rather like the arrangement in the jaws of a modern crocodile. So, although Dilophosaurus had a large head and strong jaws, it probably did not kill its...

Fueling the changes

As well as all these structural modifications to the skeleton, internal changes were necessary in a bird's physiology to cope with the heavy energy demands of flight. For example, the respiratory system became more efficient. The unique arrangement of numerous air sacs off the main respiratory passage ensures that air passes through a bird's lungs in a continual stream, rather than circulating solely within the blind-ending sacs that make up the lungs of other vertebrates. More fundamentally,...

Order Anthracosauria

The anthracosaurs (also known as batra-chosaurs) were labyrinthodonts that arose during the Carboniferous and survived until the middle of the Permian. They were not so numerous or diverse as the temnospondyls (above), but among their members were the ancestors of the reptiles. name Eogyrinus time Late Carboniferous locality Europe (England) size 15 ft 4.6 m long Eogyrinus was a long-bodied aquatic predator, probably living an alligator-type life in the deltas and swamps of the Carboniferous...

Suborder Odontoceti

The odontocetes the toothed whales probably evolved from the arch-aeocetes in the Late Eocene, about 40 million years ago. Odontocetes make up the majority of the modern whales, including the sperm, beaked, pilot and killer whales, the belugas and narwhals, the dolphins and porpoises. All these modern species had appeared by Late Miocene times, some 10 million years ago. The teeth of odontocetes tended to be simpler than those of the archaeocetes, losing their cusps and becoming rounded pegs or...

Family Ceratosauridae

This family of megalosaur-type dinosaurs was characterized by a small horn on the snout. Contemporaries of the other large carnosaurs, they lived in North America and East Africa in Late Jurassic times. But their remains are rare in comparison to those of their relatives. This horned lizard had a heavier skull than other carnosaurs because of the presence of a pair of bony ridges above its eyes, and a low crest, or horn, on its snout. The function of the horn remains a mystery, although various...

Family Ankylosauridae

This family of armored dinosaurs became abundant toward the end of the Cretaceous period, and largely replaced their relatives, the nodosaurs, in western North America and East Asia. Like the nodosaurs, they were heavily armored on the back with thick plates and spikes. But the head armor was more extensively developed, and there was a unique weapon at the tip of their tails. This was a large ball of fused bone, which could be swung like a club from side to side with potentially lethal effect...

Miocene locality Europe France size ft cm tall

This medium-sized, long-legged shore-bird is related to the modern wading and water birds, seabirds and birds of prey (grouped in the Order Ciconiiformes, see p. 177). It is often suggested that Palaelodus and its relatives represented early flamingos. But recent assessment suggests that they were more likely to be of shorebird origin they branched off fairly late from the main shorebird assemblage, and lived from the Late Oligocene to the Early Pliocene in Europe, North Africa and North...

Family Ursidae

The bears surface later in the fossil record than many other carnivores. They first appeared in Europe during the Oligocene, and since then have spread throughout most of the world. However, there are no bears native to Africa today, although there are 2 separate records of bears in that continent in the past. The primitive Agriotherium (below) lived in southwestern Africa during the Pliocene, some 5 million years ago, and brown bears are known to have lived in the Atlas Mountains of northern...

Family Proterotheriidae

The spread of the open plains over the South American continent helped induce the evolution of lightly-build running animals. The proterotheres first creatures were horselike animals ranging from late Paleocene to late Pliocene times. Prototheres appear to have undergone many of the same adaptive changes as the early horses in North America, sometimes in advance of developments elsewhere. It is unlikely that they were able to graze, though, since their dentition remains that of browsing...

Interpreting The Fossil Record

The transformation of a fossil found into a rock into a likeness of a once-living creature involves a series of skills. The fossil must first be discovered and cleaned of concealing sediment right . Next, the individual bones must be reconstructed and linked together accurately to form a skeleton below . Finally bottom , the creature must be restored, with the body fleshed and clothed with skin, to show how it may have looked. The skeleton of Archaeopteryx, the first bird above is shown as it...

Eurhinodelphis

About two-thirds of the way down the animal, and the bones of the hindlegs could still articulate with them. However, the limb bones were so small that it is difficult to imagine what use they would have been, or indeed if they showed outside the body at all. Basilosaurus must have swum in the Eocene oceans by undulating its long body and tail. For the cylindrical body to have worked efficiently as a swimming organ, this whale most probably had tail flukes. The head was typical of the early...

Name Thoatherium time Early Miocene locality South America

Argentina size 2 ft 4 in 70 cm long The smallest of the known litopterns, Thoatherium probably resembled a small gazelle. The feet and legs were very long for the size of the body, and it must have been a graceful runner. Although the paired bones of the lower limbs were reduced, they did not fuse. But the reduction of lateral toes which can be seen in both the true horses and in Diadiaphorus is here taken to an extreme. Indeed, the vestiges of its other 2 toes were even smaller than those of...

Order Desmostyla

The desmostylians were a group of strange aquatic mammals that have been aptly described as seahorses. About the size of a pony, and superficially similar in appearance, they lived along the coasts of the North Pacific in Miocene times, between about 25 and 5 million years ago. The single record of a fossil from coastal Florida suggests that desmostylians found their way from the Pacific into the Atlantic via the narrow seaway that separated North and South America until the Pliocene, about 5...

Family Phocidae

Seals may not look much like dogs or cats, but they are nonetheless members of the order Carnivora. Grouped as phocids, they probably evolved from an otterlike mustelid, such as Potamo-therium see p. 214, 216 , in the Late Oligocene, some 30 million years ago. They first appeared in European waters, and then spread north and south to the Arctic and Antarctic Oceans, and west to the Pacific, adapting rapidly to a marine, fish-eating lifestyle. However, they must still leave the sea to breed on...

Convergent Evolution

Cuvier had been sent some drawings of the recently discovered fossil of a giant ground sloth, Megatherium, of South America. He showed by means of com-, parative anatomy that it was similar in structure to the living tree sloths. But he also realized that there was little chance that such an enormous, browsing creature could still be alive but undetected, even in the great forests of South America. Cuvier's colleague at the National Museum of Natural History in...

Suborder Pinnipedia

The order Carnivora includes not only the dominant carnivores of the land, the cats, dogs and bears, but also a successful group of marine carnivores, grouped together as the pinnipeds. They include the familiar modern sea-lions and fur seals Otariidae , walruses Odobenidae and the true seals Phoci-dae . All have their feet modified into flippers, or pinnae, hence their name. The pinnipeds probably evolved in the northern hemisphere during the Late Oligocene, about 30 million years ago. They do...

Order Anaspida

The anaspids lacked the heavy head shields of other armored agnathans. Covered in thin scales, their bodies were slender and flexible, with stabilizing fins. Numerous in the seas of Late Silurian Europe and North America, these active swimmers later invaded rivers and lakes during the Devonian, and survived to the end of that period. They are the likely ancestors of the modern lampreys. name Jamoytius time Late Silurian locality Europe Scotland size 11 in 27 cm long Named for the English...

Family Megalosauridae

The earliest well-known carnosaurs belong to this family of great lizards. Their remains have been found in North America, Africa and Europe, and as a group they span a period of 140 million years from the Early Jurassic to the end of the Cretaceous. All were massively built, big-boned .creatures. The large head was high and narrow, equipped with powerful jaws and many sharp, saw-edged teeth. The arms were short but strong. The legs were long and massive enough to support the great body weight...

Amphibians Invaders of the land

Although one of the most obvious char-acteristics of living amphibians is their moist skins, this is, in fact, one of the ways in which they differ most markedly from their Paleozoic ancestors. Modern amphibians supplement their normal respiratory exchange through the lungs by breathing through their moist skins. But this, in turn, limits their size and way of life. Many Paleozoic amphibians had scales or armor covering their bodies, and many of them grew to a great size. Both these facts...

Family Mesonychidae

When plant-eating mammals excluding multituberculates first flourished at the beginning of the Paleocene, there were no carnivores to prey on them. By the mid-Paleocene, however, above 60 million years ago, some primitive and generalized stock had developed into a new order, the Acreodi. Among them were mesonychids wolflike, hyenalike or bearlike omnivores able to take advantage of this new source of food. They varied from the size of foxes to the immense Andrewsarchus. The mesonychids...

Family Psittacosauridae

The parrot dinosaurs were a rare group of ornithischian dinosaurs, found only in the Early Cretaceous rocks of East Asia. Their skulls show many features that suggest that they were the ancestors of the horned dinosaurs, or ceratopians. Their bodies, however, were similar to those of the gazellelike hypsilophodonts, from which stock they probably arose see pp. 138-141 . Like the hypsilophodonts, the parrot dinosaurs could rise up on 2 legs to run away from predators. The suggestion, therefore,...

Family Coeluridae

The coelurids flourished worldwide from the Late Jurassic through to the Early Cretaceous. In lifestyle, they were similar to the podokesaurs lightweight, active predators, running about on long legs, and grasping prey with their strong, clawed fingers. The number of fingers on each hand was reduced to 3. name Coelurus time Late Jurassic locality North America Wyoming size 6 ft 6 in 2 m long Like all members of the coelurid family, Coelurus had a small, low head only about 8 in 20 cm long , and...

Dinosaur Hips

When dinosaurs evolved an upright, 2-legged posture, they had to evolve a new attachment site for the muscles that swung the powerful hindlimbs forward. Lizard-hipped dinosaurs top evolved a downward and forward extension of the pubis bone to which the muscles attached. In bird-hipped dinosaurs right the muscles were attached to either a forward extension of the ilium, or, in later types, to a new pre-pubic extension of the pubis. was first explored by parties from the American Museum of...

Cohort Edentata

The edentates are represented today by the anteaters, tree sloths and armadillos. The name of the cohort a grouping of many orders means without teeth, but in fact only the anteaters are completely toothless. The other members have teeth, although these are reduced to a few rudimentary pegs, often without roots or an enamel covering. The edentates comprise some of the world's most bizarre mammals. As well as the living anteaters with their greatly elongated snouts, the armadillos with their...

Order Microsauria

The microsaurs, or small lizards, were the most varied group of lepospondyls, with terrestrial types that lived like lizards, burrowing types with legs, and aquatic types that kept their larval gills into adult life. All microsaurs had small legs and short tails. The group evolved late in the Carboniferous period, and survived into the Early Permian. They may have been the ancestors of the newts and salamanders. name Microbrachis time Late Carboniferous locality Europe Czechoslovakia size 6 in...

Family Ornithomimidae

The so-called bird mimics were a specialized offshoot of the coelurosaurs. About the same height and proportions as a modern ostrich, they seem to have had a similar lifestyle to that bird, hence the popular name of the group ostrich dinosaurs. They were widespread in North America and East Asia in Mid-Cretaceous times, but seem to have died out before the end of that period. All were large, long-legged sprinters. They probably traveled the open plains in groups, looking after their young while...

Order Anura

Modern frogs and toads are grouped together as anurans. As adults, they are the most specialized of all vertebrates, with the shortest backbones in the animal kingdom and powerful jumping legs not known in any other creature. It is not surprising, therefore, that an anuran must undergo a profound transformation, or metamorphosis, to change from the limbless, herbivorous, swimming larval tadpole with a long tail, to the jumping, insectivorous, tailless, bulging-eyed adult. Paleontologists are...

USSR size ft m long

Prehistoric Animals

Cetotherium belonged to a family of early baleen whales which evolved in the Late Oligocene and reached their peak during the Miocene, some 15 million years ago. It looked strikingly similar to the modern gray whale of the North Pacific, although it was less than a third of its length. Its baleen plates were probably quite short, although this is difficult to determine, since baleen, like horn and hair, does not fossilize. However, the skulls retain the marks of blood vessels which supplied the...

Family Miacidae

The miacids were the earliest true carnivores to appear, during the Paleocene, some 60 million years ago. This is an artificial group, since it contains animals that were not closely related. However, it is a convenient classification that distinguishes these early car Miacids were mostly small mammals that lived in woodlands, where they were unlikely to become fossilized. The scant remains they have left indicate that they resembled the creodonts in many ways, although they were possibly more...

Order Lipotyphla

The Lipotyphla includes 5 fossil and 7 living families. The latter include hedgehogs, shrews and moles, as well as sole-nodons of the West Indies, golden moles of Africa, tenrecs of Madagascar and otter shrews of Central Africa. name Palaeoryctes time Early Paleocene to Early Eocene A well-preserved skull shows Palaeoryctes must have closely resembled a modern shrew in appearance, with a small sleek body and a pointed snout armed with little insect-crushing teeth. Although it ate mostly...

Diadecte

This phenomenon is called paedomorphosis, and is seen in several modern salamanders, such as the cave-dwelling olm of Europe and the North American mudpuppy. The Mexican axolotl goes one step further it also retains the tadpole tail of its youth. name Pantylus time Early Permian locality North America Texas size 10 in 25 cm long A great head on a small, scaly body characterized this microsaur. It was a well-adapted land animal, moving about on short, sturdy limbs. It probably lived...

Time Late Jurassic to Early

Cretaceous locality North America Colorado, Utah and Wyoming , Africa Tanzania . Possibly Australia and Europe England and Romania size up to 10 ft 3 m long Dryosaurus also known as Dysalo-tosaurus was one of the largest of the hypsilophodonts. Although it was also one of the earliest, its anatomy was advanced in several ways. For example, each long, slender leg had only 3 toes. And there were no teeth in the front part of the upper jaw the horny beak at the front of the lower jaw met with a...

Name Ursus spelaeus time Pleistocene to Recent locality Europe Austria

Germany, Netherlands, Spain, UK and USSR size 6 ft 6 in 2 m long The genus Ursus is represented today by the brown, or grizzly, bear, the polar bear and the American black bear. But in Pleistocene times, the cave bear, Ursus spelaeus, was a particularly numerous and impressive species. It lived in Europe during the height of the Ice Age, and often escaped the worst of the winters by hibernating in Alpine caves. Many bears seem to have congregated together for this long, annual sleep, to judge...

Wyoming Asia China and

Europe France size 5 ft 1.5 m long Hyrachyus was generally very similar to Heptodon see pp. 258-261 , but a little larger and more heavily built. It was a common and widespread animal. Many species are known, ranging from the size of a modern tapir to that of a fox. Hyrachus appears to be ancestral to both the later tapirs and the rhinoceroses. Indeed, its resemblance to a primitive form of the latter group is so .pronounced that it is often classed as rhinoceros, albeit a lightweight one.

Order Dermoptera

The dermopterans constitute the group of flying lemurs a confusing name since they are neither lemurs, nor do they fly. Only 2 species survive today the colugos Cynocepkalus of Southeast Asia, both strict vegetarians. These modern animals, less than 1 ft 30 cm long, can glide as far as 450 ft 137 m from tree to tree on outstretched skin membranes. It is assumed, though there is no direct evidence for this, that Mid-Paleocene and Early Eocene dermopterans could do likewise. There is some...

Family Viverridae

This family of small carnivores contains the modern civets, genets and mongooses. The viverrids are among the oldest of the carnivores, with an ancestry dating back as far as the Middle Paleocene, about 60 million years ago. They are also among the most adaptable and least specialized of all carnivores. Viverrids are mostly long-bodied, short-legged animals. Many of them are opportunistic omnivores, eating a great variety of food from earthworms, mollusks, crabs, fish, birds and reptiles...

Suborder Protosuchia

Although their skulls were slightly more crocodilelike in appearance, the proto-suchians were still long-legged land-dwellers like the sphenosuchians above . They lived all over the world during the early part of the Jurassic period. Some members may have developed a secondary palate that separated the mouth from the nasal passages, but it could only have been made of a fleshy membrane as yet, since there is no sign of the solid bony palate developed in later crocodiles. name Protosuchus time...

Introduction

The solar system, which includes the Earth, is about 4-6 billion years old. The earliest traces of life on our planet are microscopic fossils of blue-green algae and bacteria that are found in rocks some 3.5 billion years old opposite . The atmosphere of the ancient Earth contained no oxygen. Like most modern green plants, the early algae produced oxygen, but this would have quickly disappeared because it combined readily with various elements and compounds in the Earth's crust. Not until about...

Suborder Cryptodira

The cryptodires were the most successful group of chelonians, and survive to this day most modern turtles and tortoises belong to this group. Many of them can retract their heads into the shell by lowering the neck and pulling it back vertically. As a group, the cryptodires evolved along with their pleurodire cousins during Jurassic times. But by the end of that period they had become enormously diverse, and replaced the pleurodires in the seas, rivers and lakes of the world. New forms...

Family Tapiridae

Prehistoric Chinese

The family to which the modern tapirs belong, the Tapiridae, can be traced back as far as the Early Oligocene, about 40 million years ago. The 4 species of living tapirs are all placed in the single genus Tapirus. Two species occur in Central America and northern South America and 2 in Southeast Asia none remain in the group's original northern stronghold. This scattered relict distribution has often been cited as evidence for the existence of the southern supercontinent of Gondwanaland. It is...

Order Actinistia

The actinistians, or coelacanths, have a long evolutionary history, longer in fact than anyone thought. They arose in the Middle Devonian and the last fossils found come from Late Cretaceous rocks, some 70 million years old. Then, in 1938, a living coelacanth was caught in the deep waters of the trench that separates Madagascar from southern Africa. The people of the nearby Comoro Islands had known of this fish for generations, but it was new to science. The term living fossil was awarded to...

Locality Africa Namibia Asia

China and Europe France size 6 ft 6 in 2 m long Although bears are not found in Africa today, they lived there in the past. Agriotherium lived in southwestern Africa, a whole continent away from its usual haunts of Europe and Asia. Agriotherium was a very large bear, even larger than the Kodiak bear above . It was also very primitive, and looked rather like a dog in some ways. However, its teeth had developed the typical bear pattern. It is therefore safe to assume that was omnivorous. name...

Name Scarrittia time Early Oligocene locality South America

Argentina size 6 ft 2 in 2 m long Scarrittia is the only member of the Leontiniidae that we know from a well-preserved skeleton. In life, it probably looked much like a lumbering, flat-footed rhinoceros. Scarrittia was a rather heavy animal with a long body and neck, stout legs, 3-toed hoofed feet, and a very short tail. The tibia and fibula were partly fused at the top, so the feet could not be turned sideways. The face was quite short and the jaws contained the full complement of 44...

Name Thesodon time Early Miocene locality South America

Argentina size 6 ft 6 in 2 m long Trotting across the Pampas plains, this browsing and grazing long-necked creature would have looked much like a modern guanaco. The main difference would have been in the feet, which in Thesodon were 3-toed and hence rather heavier. The position of the nostrils in the skull suggests that a trunk was also present, but this may have been no more prominent than the one carried by the living saiga antelope. The lower jaw was very slim and the mouth had a full set...

Order Therapsida

The therapsids were advanced synapsid reptiles, and the direct ancestors of the mammals. Although the remains of the first therapsids are found at the base of the Late Permian, they had diverged from the sphenacodont pelycosaurs more than 20 million years before, probably during the Early Permian. They spread rapidly to all parts of the world, including Antarctica. The therapsids are grouped into several suborders see pp. 58-59 , only one of which, the cynodonts, survived into the Jurassic see...

Family Elephantidae

This is the family to which the modern elephants belong. They differ from their earlier relatives, the mastodonts, principally in the form of the teeth. True elephants have lost the tusks of the lower jaw, and this has enabled them to modify their method of mastication. Mastodonts ground their food in a complex rotary motion, whereas elephants cut or shear it. The change of action has also affected the teeth, which are taller, with longer, more complex enameled surfaces. In many species, there...

Order Sirenia

The sirenians, or sea cows, are the only group of mammals to have become fully adapted, aquatic herbivores. Today, they are represented by 3 species of manatee Trichechus and a single species of dugong Dugong dugon . They all have bulbous bodies, forelimbs modified into flippers, no hindlimbs and a horizontally flattened tail, like that of a whale, which they use to propel themselves through the water at a leisurely pace. Sirenians are known from the Early Eocene of Hungary. Their evolution is...

Subclass Lepospondyli

Contemporary with the large, bulky labyrinthodonts see pp. 50-53 were a group of smaller, insectivorous amphibians, grouped together as the lepospondyls. The anatomical feature that unites them is the structure of their vertebrae. These amphibians evolved in the Carboniferous period, and survived until the end of the Permian. During this span of some 100 million years, a variety of small lepospondyls evolved, which tended to look like salamanders or snakes. They can be grouped into 3 major...

Family Myrmecophagidae

The myrmecophagids, or true ant-eaters to distinguish them from the completely unrelated marsupial ant-eaters such as the modern numbat Myr-mecobius are highly specialized for exploiting a diet of ants and termites. Their evolution is little known an early form, Protamandua, from the Early Miocene about 20 million years ago, was already a typical anteater. name Eurotamandua time Middle Eocene locality Europe Germany size 3 ft 90 cm long Until recently, when a fossil anteater was discovered in...

Protorothyrididae

Members of this family are the earliest-known reptiles. They first appeared in the Late Carboniferous period, and survived into Mid-Permian times, a span of some 50 million years. The protorothy-ridids were the basal stock from which many specialized groups evolved, including the ruling reptiles the dinosaurs, crocodiles and flying pterosaurs see pp. 90-93 . name Hylonomus time Late Carboniferous locality North America Nova Scotia size 8 in 20 cm long Hylonomus is the earliest-known,...

Family Enaliarctidae

The enaliarctids were the earliest members of the otarioids to evolve, and were the ancestors of the modern sealions, fur seals and walruses. They lived during the Early Miocene, about 23 million years ago, and like the phocids above , probably evolved from among the mustelids. Later in the Miocene, about 18 million years ago, enaliarctids gave rise to another extinct family of early seals, the desmatophocids below . Later still, about 15 million years ago, some of the enaliarctids evolved into...

Family Mosasauridae

Pachyrhachis

The mosasaurs were a successful, though short-lived, offshoot from the monitor lizard group. They were fully adapted to a marine life, living in inshore waters during the Late Cretaceous period. Some of them were giants. name Platecarpus time Late Cretaceous locality Europe Belgium and North America Alabama, Colorado, Kansas and Mississippi size 14 ft 4.3 m long Many specimens of this marine lizard have been found in the chalk deposits of Kansas, laid down in the warm, shallow seas that covered...

Locality Australia New Zealand

And South America size 7 ft 5 in 2.3 m long Prosqualodon and its immediate family may have been ancestral to all the other toothed whales. It probably looked like a small modern dolphin, with a long, narrow snout armed with pointed, fish-catching teeth. But the teeth were primitive, since there were still triangular teeth at the back of the jaws, as there had been in the earlier whales, the archaeocetes above . Prosqualodon's skull had become lightweight as a result of several modifications to...

Locality South America

Thotobolosaurus

Argentina size up to 33 ft 10 m long The limb bones, and the shoulder and hip girdles of this large prosauropod, were much more massive than those of its relatives, the plateosaurs above . This indicates that it was an obligatory quadruped that is, it had to walk on 4 legs in order to support its great weight. The skeleton was modified accordingly. The limb bones were thick and solid, and held vertically beneath the body. The hips were fused to the backbone by 3 vertebrae, giving a solid...

North America Nebraska size ft m high

This 4-tusked mastodont was wide-ranging, cropping up as fossils on 4 continents. As a result, the same fossil animal has been given a variety of names, including Trilophodon and Tetrabelodon. The lower jaw, with its parallel tusks, was very long. It was probably used in conjunction with an equally long trunk on the upper jaw. There was a progressive reduction in the number of teeth, but those that remained developed a number of high ridges or cusps to increase the grinding area. This was...

Seymouria

Cacops was a member of the dissoro-phids. This diverse family of temno-spondyls arose slightly later than the eryopids above , and became extinct after them, in the Early Triassic. Many members of this family were fully adapted land-living amphibians. Their heyday came in the Early Permian, when the climate in Euramerica changed from the warm, humid conditions of the Carboniferous to the more arid conditions of the Permian. Cacops and its relatives, along with some of the eryopids, were quick...

Hypsilophodontidae

Hypsilophodonts were the gazelles of the dinosaur world. They probably lived in social herds, like modern deer, and would have been continually alert. When danger threatened and there were many carnivorous dinosaurs around to attack them they sprinted off at high speed, their lightweight bodies and long, running legs facilitating a fast retreat. Hypsilophodonts were among the most successful of the dinosaurs. As a group they flourished for about 100 million years, from the Late Jurassic to the...

Order Nectridea

The nectrideans were 4-legged amphibians, newtlike in appearance and with long, flattened tails for swimming. Exclusively aquatic in lifestyle, they evolved during the Late Carboniferous, and survived until the end of the Permian. Early nectrideans had a skull structure very like that of a labyrinthodont. Their limbs were well developed, with 5 toes on each. The later members of the group tended to have small forelimbs, and a toe had been lost from each. The snout also became greatly elongated...

Family Millerettidae

The millerettids were a family of anap-sid reptiles with a pair of openings in the skull behind the eyes. This may sound like a contradiction, since the anapsids are that group of reptiles with no openings in their skulls, apart from the eyes and nostrils. In the case of the millerettids, other features of the skull place them firmly in the anapsid group. Most likely, they represent a specialized side branch of the main reptilian tree, and evolved these openings independently. Millerettids were...