The Jawless Fishes

The earliest fishes are sometimes included in the para-phyletic group 'Agnatha' (literally, 'no jaw'), and they Fig. 3.3 The structure of vertebrate hard tissues. (a) Dentine in a dermal tubercle in one of the presumed oldest vertebrates with a dermal skeleton, Anatolepis from the Upper Cambrian of the USA, showing dentine tubules running from the pulp cavity (bottom) to the outer surface (top). Lamellar tissue curves up to the base of the tubercle (arrowed). Photograph X1500. (b) Block...

Carnivora And Pholidota

The final clade to be noted within Laurasiatheria consists of Carnivora plus Pholidota. This rather surprising pairing of carnivorous mammals with pangolins emerges from recent molecular studies (see Box 10.6), and it was not particularly expected from morphological studies. The pairing of Carnivora and Artiodactyla within Ferungulata was, on the other hand, long argued by mammalogists. The living meat-eaters, cats, dogs, hyaenas, weasels and seals are members of the Order Carnivora. These...

Functional morphology

The first question that people ask about any fossil vertebrate is 'what did it do ' Just how did the heavily armoured Devonian fishes manage to swim Why did some mammal-like reptiles have massively thick skull roofs What did Stegosaurus use its back plates for Why did sabre-toothed cats have such massive fangs These are all questions of functional morphology, the interpretation of function from morphology, the shape and form of an animal. The main assumption behind this approach is that...

Box The Largest Rodent Ever

South America has become well known for its giant rodents. The largest ever, Phoberomys, is reported by Sanchez-Villagra etal. (2003). Until then, this form had been known only from isolated teeth and fragmentary postcranial bones, until the discovery of an exceptionally complete skeleton in a rich locality of fossil vertebrates in the Upper Miocene of Venezuela. Phoberomys was 3 m long and it stood 1.3 m at the shoulder. It weighed 700 kg, more than ten times the mass of the largest living...

Box Relationships Of Neopterygii

Fossil Fish Book

The Neopterygii are a vast and diverse group and there is still much contusion over their relationships. Most studies (e.g. Patterson and Rosen, 1977 Lauder and Liem, 1983 Gardiner et al., 1996 Johnson and Patterson, 1996), however, agree on the main points (see cladogram). The basal neopterygians, formerly termed 'holosteans', form a series ot outgroups to the Teleostei. In previous versions, all subsequent taxa formed a series ot outgroups, but new work (Johnson and Patterson, 1996) shows...

Tree Of Life Controversy Boxes

Ch 1 Deuterostome relationships 8 Ch 3 Basal vertebrate relationships 41 Sarcopterygian relationships 68 Ch 4 Phylogeny of the Devonian tetrapods 80 Relationships of the basal tetrapods 98 Ch 5 Relationships of early amniotes 113 Relationships of the synapsid groups 122 Ch 6 Archosaur diversification 138 Ch 7 Chondrichthyan relationships 165 Relationships ofNeopterygii 178 Ch 8 Relationships of the dinosaurs 213 Relationships ofMesozoic reptiles 232 Ch 9 Bird fingers 1,2,3 or 2,3,4 262...

Mass Extinction

The greatest mass extinction of all time took place at the end of the Permian (Benton, 2003), and the tetrapods were involved. Of the 48 families that were present in the last 5 Myr of the Permian, the Tatarian Stage, 36 died out (a loss of 75 ). These include ten families of basal tetrapods (mainly anthracosaurs), captorhinids, millerettids and pareiasaurs, as well as the younginids, and 17 families of therapsids, including the gorgonop-sians, the last dinocephalians, most of the dicynodonts,...

Classification Of The Reptiles

*Order Pelycosauria Family Eothyrididae Family Caseidae Family Varanopidae Family Ophiacodontidae Family Edaphosauridae Family Sphenacodontidae Order Therapsida tSuborder Biarmosuchia tSuborder Dinocephalia tSuborder Dicynodontia tSuborder Gorgonopsia Suborder Cynodontia tFamily Procynosuchidae tFamily Galesauridae tFamily Cynognathidae tFamily Diademodontidae tFamily Chiniquodontidae tFamily Traversodontidae tFamily Tritylodontidae tFamily Tritheledontidae Class Mammalia (see below) Class...

The Diversity Of Ornithischian Dinosaurs

Stegosaurus Bone Names

The Ornithischia are the second major dinosaurian clade and they are relatively easy to diagnose. They have a pubis that points backwards (Figure 8.3(b)) as well as over 30 other derived characters of the skull and skeleton (Sereno, 1986,1999). The ornithischians arose during the Carnian (Late Triassic, 230-220Myr ago), or earlier, but fossils are extremely rare until the Jurassic. The ornithischians were all herbivorous and they divide into two main groups, the Cerapoda (the bipedal...

The Early Sharks And Chimaeras

Bear Gulch Shark Fossil

About 60 families ofsharks and their relatives lived during the late Palaeozoic and Mesozoic, but many of these are known only from teeth and spines. The basal sharks include the Cladoselachidae, such as Cladoselache from the Late Devonian (Figure 3.15), which was surprising ly modern-looking. Recent finds, however, have revealed some quite bizarre chondrichthyans in the Carboniferous (see Box 7.1) and the better known groups of these are reviewed here, as well as their Mesozoic derivatives....

Temnospondyls And Reptiliomorphs After The Carboniferous

Several of the major Carboniferous lineages of tetrapods survived into the Permian (290-251 Myr ago) and beyond. These include groups such as the Anthra-cosauria, Aiistopoda, Nectridea and Microsauria, most of which died out by the end of the Early Permian, as well as the Temnospondyli, which lasted much longer, and two groups that were typically Permian, the Seymouriamorpha and the Diadectomorpha. These last three groups will be described now. 4.5.1 Temnospondyli Permian to Cretaceous history...

Box Relationships Of The Dinosaurs

Nasal Bone And Jaw Fossil

The Dinosauria (see cladogram) consist of two main clades (Gauthier, 1986 Benton, 1990a Sereno, 1999), the Saurischia and Ornithischia. The Saurischia fall into two main clades, the Theropoda and Sauropodomorpha. Within Theropoda, the main outlines are widely agreed, with the coelophysoids and ceratosaurs near the base, then various larger flesh-eating groups (e.g. megalosaurids, allosaurids, spinosaurids), then tyrannosaurids and maniraptorans (troodontids, dro-maeosaurids, birds). Much of the...

In Triassic Seas

There were four main groups of reptiles in Triassic seas (McGowan and Motani, 2003 Rieppel, 2000c), the placodonts, pachypleurosaurs, nothosaurs and ichthyosaurs, all of which have the euryapsid skull pattern (see p. 112), with one (upper) temporal fenestra. Each has very different aquatic adaptations and they represent a major radiation of marine predators, probably from independent sources among the early diapsids. Late Triassic reptile communities are important because they document a major...

Testudines The Turtles

Dorsal And Ventral View Testudines

The turtles and tortoises, Testudines or Chelonia, arose in the Late Triassic and later achieved a diversity of 25 families, of which 13 families and 295 species are extant (Mlynarski, 1976). It seems that early on they hit on a successful design, the 'shell', and stayed with it. Turtle diets are broad-ranging, including herbivores and insectivores on land, and herbivores and carnivores in the water, with diets from jellyfish to fishes. The shell of turtles is composed of two portions, a domed...

Box Archosaur Diversification

The archosaurs underwent a major phase of evolutionary diversification at the end of the Early Triassic. They branched into two major groups, one of which led to the crocodilians and the other to the dinosaurs and birds. The precise compositions of these two lineages were hard to resolve Gauthier, 1986 Benton and Clark, 1988 Sereno, 1991 Gower and Wilkinson, 1996 Benton, 1999a , as there were a large number of convergences, particularly in modifications of the limbs and changes in posture see...

Lemurs and lorises

The remaining groups of basal primates see Box 11.1 are the lemuriforms, the extant lemurs, lorises and their relations. The Lemuriformes all share a tooth-comb composed of the incisors and canines, which are narrow and point forwards used for feeding and for grooming the fur , and a toilet claw on the the second toe. Lemurs now are restricted to the island of Madagascar, and the lorisiforms are found in Africa and southern Asia. There are 54 living species of lemuriforms, which include the...

Continental drift

One of the most dramatic changes that has taken place through geological time see Box 2.2 is continental drift, the movement of continents and oceans relative to each other. The idea that the present layout of continents had not always been the same was suggested in the 19th century, when some geographers noted how the Atlantic coasts of South America and Africa could be fitted together like giant jigsaw pieces. In 1912, Alfred Wegener marshalled a great deal of geological and palaeontological...

Box How Many Fingers And Toes

Digits Horses

For years, everyone had assumed that five fingers and toes was the normal complement for tetrapods. The so-called pen-tadactyl 'five-digit' limb was a classic synapomorphy of all tetrapods, from salamanders to humans. Our counting system is based on ten, in other words, two handfuls of fingers. The new finds of basal tetrapods with six, seven, or eight digits showed that there is nothing special about five digits, and that each finger or toe is not individually mapped to a single gene. The...

Display and study

Bones of spectacular new species of fossil vertebrates, or unusually complete specimens, may be prepared for display. The bones are strung together on metal frameworks or, more frequently, casts are mounted with internal supports. Casts are made in tough lightweight materials, such as fibreglass, from moulds of the original specimens Figure 2.4 a . Most fossil vertebrates, however, are never displayed, but are reserved solely for study. The specimens may be studied at once by scientists in the...

Box The Arthrodires From Gogo

Placoderm Skull Anatomy

The Gogo locality in Western Australia, of Late Devonian age, has produced some of the most spectacular fossil fishes in the world, including 20 species of arthrodires. The specimens are preserved uncrushed and in three dimensions. Fossils were first collected on the lands of the Gogo cattle station in the 1940s, but their true quality was not realized at first, because a great deal of detail was lost when they were cleaned using chisels and needles. It was only in the 1960s, when...

The Triassic Scene

The Triassic world was similar in many ways to that of the Permian. All continents remained united as the supercontinent Pangaea Figure 6.1 , although the North Atlantic Ocean began to open at the very end of the period, with rifting in eastern North America, Fig. 6.1 Map of the Triassic world, showing the arrangement of the present continents light line and the Triassic coastline heavy line . Fossil reptile localities are indicated with symbols Early Triassic B,Middle Triassic , Late Triassic....

Ordovician jawless fishes

After the Cambrian radiation of basal vertebrates, with and without skeletons, and the conodonts, a diversity of groups of fishes appeared in the Ordovician, but most are represented only by dermal elements. Two 'agnathan' clades, the Astraspida and Arandaspida, are known, however, from more complete specimens in the Upper Ordovician Sansom et al., 2001 . Astraspids and arandaspids are small fishes, about 200 mm long. They have a mobile tail covered with small protruding pointed plates, and a...

Further Reading

The biology of amphibians is outlined by Duellman and Trueb 1994 . Heatwole and Carroll 2000 provide a detailed overview of basal tetrapods and fossil amphibians. Zimmer 1999 and Clack 2002c give thorough and clear accounts of all the recent work on Devonian and Carboniferous basal tetrapods, and the new evidence about the transition on to land. These web sites offer fascinating glimpses of the excitement of current work on basal tetrapods http tolweb. Sarcopterygii, the 'Tree of Life' pages...

Preface

Vertebrate palaeontology is always in the news astonishing, ancient basal chordate and vertebrate fossils are announced from China fossil hunters argue about which was the largest dinosaur of all, or the oldest dinosaur with feathers an ancient fossil bird is announced that adds 100 million years to their history ever-older specimens of human beings are unearthed in Africa. When I wrote this book in 1989, I felt that there was a need for an up-to-date account of what is known about the history...

Box Relationships Of The Mesozoic Mammals

Prototherian Mammary Glands

A traditional view of mammalian evolution was that the group was diphyletic, that it had two ancestral lines, one leading to the 'therians' and the other to the 'prototherians'. The 'therians', those forms with a triangular array of cusps on the molars, included Kuehneotherium, the symmetrodonts, marsupials and placentals. The 'prototherians' had the molar cusps aligned and included the morganucodontids, docodonts, triconodonts, multituberculates and monotremes. A second line of evidence for...

South American Mammalsa World Apart

Protemnodon Pelvis

For most of the Cenozoic 65Myr ago to present , South America was an island, isolated from all other parts of the world. As in Australia, a spectacular endemic geographically restricted fauna of mammals evolved that shows little taxonomic similarity to those Fig. 10.17 Australian fossil marsupials a skull of the marsupial 'lion' Thylacoleo, showing the blade-like cheek teeth b skull of the kangaroo Procoptodon c foot of the kangaroo Protemnodon, showing the dominant fourth toe d skeleton of the...

Vertebrates And The Head

Basic Vertebrate

The vertebrates, the major group of chordates, form the subject of this book. They have sometimes been termed craniates since all forms, including the hag- fishes and lampreys, have specialized head features the cranium, the skull . The term vertebrate is better known, so will be used here, following recommendations by Donoghue etal. 1998 . The basic vertebrate body plan Figure 1.9 shows all of the chordate characters so far described notochord, dorsal nerve cord, pharyngeal 'gill' slits,...

The Beginning Of The Age Of Placental Mammals

The Palaeocene Epoch 65-56 Myr ago marks the first phases of the radiation of the placental mammals. While Australia, South America and Africa acquired their own largely unique faunas, the northern continents were home to the Boreoeutheria see Box 10.6 . The death of the dinosaurs must have left vast areas strangely empty of large land animals. A sample of life just after the world began to fill up with mammals may be seen by studying a well-known Palaeocene fauna from North America see Box...

Homo erectusthe first widespread human

A new hominin species arose in Africa about 1.9 Myr ago that showed advances over H. habilis.Thebest specimen, and one of the most complete fossil hominid skeletons yet found Figure 11.12 a , was collected in 1984 by Richard Leakey and colleagues on the west side of Lake Turkana, Kenya. The pelvic shape shows that the individual is a male and his teeth show that he was about 12 years old when he died. He stood about 1.6 m tall and had a brain size of 830 cm3. The skull Figure 11.12 b is more...

The Kt Event

Fossil Range And Relative Abundance

Often the only question people ask about the dinosaurs is why they died out. Paraphrasing the words of Malcolm in Macbeth, 'nothing in their life became them like the leaving it'. Over the years, hundreds of theories for this disappearance 65 Myr ago at the Cretaceous-Tertiary KT boundary have been proposed. It might seem odd that there is still so much debate after all, the KT boundary is the most studied point in geological time. Despite all this study, however, many key questions remain...

Box Basal Vertebrate Relationships

Fossil Calcified Cartilage

The relationships of the basal vertebrate groups to each other have been controversial. For a long time, zoologists grouped the living lampreys and hagfishes together as Cyclostomata. The first cladistic studies, however, broke up Cyclostomata, and distributed the various clades of jawless fishes between the two living groups, either as close relatives of the hagfishes or of the lampreys reviewed, Janvier, 1984 Maisey, 1986 Forey and Janvier, 1993 . A recent comprehensive cladistic analysis...

Cladistics

Cladistic analysis of morphological characters is the main technique used for studies of the relationships of living and fossil vertebrates. The result of a cladistic analysis is a cladogram, such as those in Figure 1.7. A cladogram is a branching diagram that links all the species, living and fossil, that are under investigation, and the branching points, or nodes, mark points at which shared characters arose. A cladogram is not an evolutionary tree because there is no absolute time-scale,...

What Are The Primates

There are over 230 species of living primates, classified in 13 families, of which modern humans, Homo sapiens, are but one. Primates range, in evolutionary terms, from bush babies and tarsiers to gorillas and humans Figure 11.1 , and they range in size from the pigmy mouse lemur weighing 30 g to the gorilla at more than 175 kg. Primates are characterized by 30 or so characters that relate to three major sets of adaptations 1 agility in the trees 2 large brain and acute daylight vision and 3...

The Mesozoic Mammals

Jeholodens

Adelobasileus, Sinoconodon, Morganucodon and Mega-zostrodon were some of the first mammals. Another 20 or so mammalian families have been recorded in the Mesozoic Lillegraven et al., 1979 Kemp,1982 Szalay et al., 1993 Luo et al., 2002 , but many of these are based on incomplete material and their relationships are hard to assess see Box 10.3 . The main groups will be reviewed here in roughly chronological order. The kuehneotheriids, represented primarily by Kuehneotherium from the Lower...

Urochordatasea squirts

Endostyle Zoology

A typical sea squirt,or tunicate,is Ciona Figure 1.2 a , which lives attached to rocks in seas around the world. It is a 100-150 mm tall bag-shaped organism with a translucent outer skin the tunic and two openings, or siphons, at the top. The body is firmly fixed to a hard substrate. The internal structure is fairly complex Figure 1.2 b .A large pharynx fills most of the internal space, and its walls are perforated by hundreds of gill slits, each of which bears a fringe of cilia, fine hair-like...

Box Chondrichthyan Relationships

Ikan Chondrichthyes

Living chondrichthyans are readily classified as either sharks and rays elasmobranchs or chimaeras holocephalans , and most fossil taxa can be assigned to one or other branch of chondrichthyan evolution. There has been a great deal of debate about the placement of major taxa, whether for example the holocephalans are part of the elasmobranch clade, with symmori-dans and cladoselachids as their outgroups, or whether there was a clear division between the clades Elasmobranchii and...

Box African Dinosaurs And Continental Movements

Tarbosaurus Skull Dorsal

Africa became an island during the Cretaceous how did this affect the dinosaurs Following fragmentation of the supercontinent Pangaea, Africa remained linked to South America and other southern hemisphere land masses through most of the Early Cretaceous see Figure 8.2 . Madagascar broke away from the main African land mass by 120 Myr ago and South America followed by 100 Myr ago. A major marine transgression about 95 Myr ago then flooded most of North Africa and the Sahara, forming a seaway...

Cretaceous Birds With And Without Teeth

Until 1990, there was a long gap in the fossil record of birds between Archaeopteryx, dated at 150 Myr ago, and Hesperornis and Ichthyornis from the Upper Cretaceous of North America, dated at 90-65 Myr ago. This time span represents the first half of the history of birds. New discoveries from the Lower Cretaceous of China, Mongolia, Spain and other parts of the world have helped to fill this gap, and they have revealed the existence of several unique Cretaceous bird lineages, and especially...

Archaeopteryx

Draw The Dorsal View These Specimens

Archaeopteryx has been justly famous since its discovery in 1860. At that time, one year after publication of Charles Darwin's'On the Origin of Species', the new fossil seemed to be a perfect 'missing link'between the reptiles and the birds, and enthusiasts for evolution, such as Thomas Henry Huxley, used it as evidence for the new theory here was an animal with a long bony tail, a hand with three separate clawed fingers with claws and toothy jaws all primitive reptilian characters , but also...

Taphonomy

Animal Bones Taphonomy

The mode of burial and preservation of fossils, their taphonomy, is important in their interpretation. The BBC series, Walking with Dinosaurs, was the most successful science documentary series ever made since 1997, it has been seen by over 200 million people in nearly every country in the world. The series of six programmes was conceived by Tim Haines a few years after he had seen Steven Spielberg's Jurassic Park 1993 , in which a clever mix of computer animation and models gave the first...

Box Giant Horseeating Birds Of The Eocene

If tetrapod history had proceeded differently, the major carnivores on land today might have been giant birds. The radiation of mammals in the Palaeocene and Eocene after the extinction of the dinosaurs did not include any very large carnivores see pp. 329-35 , and birds seem to have become top predators in some parts of the world. The gastornithiforms such as Diatryma see Figure 9.12 b may have fulfilled this role in the Palaeocene and Eocene of North America and Europe, although their diet is...

Diverse early chordates

There are four main categories of possible early chordates possible urochordates, possible cephalo-chordates, vetulicolians, and carpoids. At one time, conodonts, represented in the fossil record generally only by their tooth elements, were treated as dubious chordates. Conodonts are now placed firmly within the Vertebrata, as jawless fishes, as are some of the taxa from Chengjiang, such as Haikouichthys and Myllokunmin-gia see Chapter 3 . Urochordates have a patchy fossil record. Isolated...

Orrorin Sahelanthropus Ardipithecus which is the first human

Since 2000, the race to find the oldest possible human fossil has been intense. Several new finds have been announced that have pushed the records back from the Pliocene to the late Miocene. These early dates are of course within the range of molecular estimates for the split of humans from chimps 8-5 Myr ago , but they exceed the favoured estimate of 5 Myr ago that was derived from genetic analyses. There are two ancient contenders, both dated at about 6 Myr old and both announced in rapid...

Were The Dinosaurs Warmblooded Or

A heated debate has raged since 1970 concerning di-nosaurian physiology. Ever since dinosaur palaeobiolo-gists realized that many dinosaurs were active animals e.g. Ostrom, 1969 Galton, 1970a, b , the question has continued to resurface. Bakker 1972,1986 in particular argued that all dinosaurs were fully warm-blooded, just like living birds and mammals, and that this explains their success. His claim was that the dinosaurs were endotherms, animals that control their body temperature internally,...

Lepidosauria

Viperid Skull Illustration

Lepidosaurs today include 4470 species of lizards and 2920 species of snakes, as well as the tuatara, Sphenodon from New Zealand, an isolated member of the clade. This grouping is confirmed by molecular evidence Hedges and Poling, 1999 Zardoya and Meyer, 2001c Rest et al., 2003 . The first known lepidosaurs are sphenodontians, distant ancestors of the living tuatara, and the Lepidosauria radiated dramatically in the Mid-Jurassic, coincident with the oldest known lizards, and again in the Early...

Box Human Relationships

Phylogenetic Tree With Ten Species

Most palaeoanthropologists accept that there are two separate lines or stages of hominin evolution, the australopiths and Homo. The key disputes concern the interpretation of Lucy and her Pliocene relatives, whether Australopithecus is a clade, or splits into several lineages, where A. africanus sits either on the line to Homo, or as part of a distinct australopith clade , whether Homo is monophyletic or not and how many species of hominin to accept as valid. The current consensus see cladogram...

Box Dinosaurs With Feathers

Dinomorph Diplodocus

Professor Chen Pei-ji of the Nanjing institute of Geology and Palaeontology created a sensation at a conference in October 1996 when he announced that he had found a dinosaur with feathers. He showed pictures of a small theropod, preserved complete, with tufts of hair-like structures all along its back and tail. The dinosaur was named Sinosauropteryx and it was shown to be a close relative of Compsognathus, a coelurid, by Chen et al. 1998 . if these truly were feathers of some kind, then all...

Ice Age Extinction Of Large Mammals

Columbian Mammoth

Many fossil mammals ofthe Pleistocene are regarded as typical of the Ice Ages that affected large parts of the world animals such as the mammoth, woolly rhinoceros, giant Irish deer, giant cattle and cave bear. These all disappeared, however, in relatively recent times and there is considerable interest in trying to establish just what happened and why Martin and Klein, 1984 . The Pleistocene Epoch 2-0.01Myr ago is marked by many ice ages, during which the ice sheet covering the North Pole...

Box Semionotid Species Flocks

During the Late Triassic and Early to Mid-Jurassic, a time span of 45Myr, there were 20 or more large lakes on the eastern seaboard of North America along a great rift valley that was formed by the initial phases of opening of the North Atlantic. The sediments deposited in these lakes, the Newark Supergroup, record in detail the histories of filling and drying of the lakes, and in places annual varves have allowed geologists to reconstruct the histories and time-scales in astonishing detail....

Devonian Tetrapods

Knowledge about Devonian tetrapods has increased dramatically since 1990. The oldest potential tetrapod remains are tantalizing some ill-defined footprints from Australia, and isolated bones and footprints from different parts of the Old Red Sandstone continent. Some Late Devonian taxa, Metaxygnathus from Australia, Elginerpeton from Scotland and Obruchevichthys from the Baltic area, are close to the evolutionary transition from sarcopterygian fishes to basal tetrapods. In addition, unequivocal...

Evolution Of Modern Amphibians

Grandisonia

Modern amphibians, the Lissamphibia, are diverse, being represented by more than 4000 species that fall into four distinctive clades, the extinct albanerpeton-tids, the anurans frogs and toads , the urodeles newts and salamanders , and the gymnophionans limbless caecilians . The history of each of these will be outlined briefly before a consideration of their origins and relationships. The albanerpetontids are a family of some five or six genera, known from the Mid-Jurassic to the Miocene of...

Sea Squirt Anatomy

Ciona Adult Sea Squirt

Vertebrates are all the animals with backbones, the fishes, amphibians, reptiles, birds, and mammals. These animals have attracted a great deal of study. The efforts of generations of vertebrate palaeontologists have been repaid by the discovery of countless spectacular fossils the heavily armoured fishes of the Siluro-Devonian, seven- and eight-toed amphibians, sail-backed mammal-like reptiles, early birds and dinosaurs with feathers, giant rhinoceroses, rodents with horns, horse-eating...

Perissodactyla Grazers And Browsers

Chalicotherium

According to the new molecular phylogenies see Box 10.6 , perissodactyls are a part of the clades Laurasiatheria and Ferungulata, and they are a sister group to Carnivora Pholidota . The perissodactyls, such as horses, tapirs and rhinoceroses, are distinguished from the artiodactyls, or even-toed ungulates 2 or 4 toes , by having an odd number of toes 1,3, or 5 . Perissodactyls diversified in the early Eocene, replacing basal placental groups see pp.329-33 as dominant browsing herbivores. Some...

Heterostraci

Sacabambaspis

The heterostracans, a large group of some 300 species, radiated extensively in the Silurian and Early Devonian. Their head shields vary tremendously in shape among different species, and they are distinguished from the astraspids and arandaspids by having a single exhalant opening on each side into which the gills open. Heteros-tracans all have in common a broad ornamented plate on top, one or more plates on either side of this, and a large element covering the underside Halstead, 1973 Blieck,...

Box Tetrapods Of The Volcanic Springs

The Midland Valley of Scotland, around Edinburgh and Glasgow, was an important coal-producing area. The coal is associated with richly fossiliferous Carboniferous rocks, and East Kirkton, near Edinburgh, has become one of the most famous sites Milner et al., 1986 Clarkson et al., 1994 . Fossils were first found there in the 1830s, and include abundant plants and rare eurypterids, i.e. large aquatic arthropods. The rocks consist of volcanic tuffs associated with limestones and unusual layered...

Box Relationships Of The Synapsid Groups

Cynodont Skeleton

Synapsida traditionally have been divided into 'pelycosaurs', a paraphyletic group, and therapsids, a well-characterized clade see cladogram . Both groups together were formerly sometimes called 'mammal-like reptiles'. The pelycosaurs appear to form a sequence of outgroups to Therapsida, with the sphenacodontids being the most derived Reisz, 1986 . The Biarmo-suchia, perhaps a paraphyletic group, are the most basal therapsids. The dinocephalians, dicynodonts and gorgonopsians follow next Hopson...

Cynodonts And The Acquisition Of Mammalian Characters

Zygomatic Arch And Evolution

The cynodonts first appeared in the Late Permian,when forms such as Procynosuchus already showed mammalian characters in the cheek region and palate and in the lower jaw. During the Triassic, several cynodont families appeared, mostly weasel-sized to dog-sized carnivores, but including some herbivorous side branches. With hindsight, a sequence of nine or ten key steps from Procynosuchus to the first mammals may be discerned through the complex pattern of cynodont radiations Figure 10.1 . The...

Preparation and conservation of bones

The key work follows in the laboratory, where the fossils are made ready for study or for exhibition. There are now many professional palaeontology preparators and conservators, and the techniques available have advanced enormously in recent years. The important point to remember is that information is lost at every stage in the process of excavation and preparation, and the good technician seeks to minimize that loss. Back in the laboratory, the plaster jackets are cut off the large bones, and...

Box Tooth Occlusion

Amphibians Jaws

Occlusion is well developed in Scalenodon, a diademodontid from the Middle Triassic of Tanzania. Such occlusion is seen also in traversodontids, tritylodonts and mammals, but is otherwise absent among eucynodonts. The jaw cycle ends with a pronounced backwards pull of the lower jaw, and a powerful shearing and crushing movement is initiated in which all seven lower cheek teeth move tightly back into curved facets of the broad upper cheek teeth see illustration . Food items are sheared by a...

Anaspida and Thelodonti

The anaspids and thelodonts were modest in size, had limited armour, and their affinities are unclear. In recent cladistic analyses Donoghue et al., 2000 Donoghue and Smith, 2001 , anaspids and some thelodonts are successive outgroups to osteostracans, galeaspids and higher forms see Box 3.1 . Anaspids are known from the Silurian and Devonian Blom et al., 2002 . Pharyngolepis Figure 3.9 a is a cigar-shaped animal 200 mm long, with a terminal mouth, small eyes, a single dorsal nostril and a...

Box Relationships Of Mesozoic Reptiles

Postorbital Crest Amphibians

The terrestrial reptiles of the Triassic, Jurassic and Cretaceous periods Chapters 6 and 8 were mainly diapsids, with a few anapsids, essentially the turtles, and their cladistic relationships see cladogram are clear in broad outline. The turtles and tortoises, Testudines, form a well-characterized clade that is part of the larger clade Anapsida see Box 5.1 . Within Testudines, the Late Triassic and Early Jurassic forms, Proganochelyidae and Australochelidae, are outgroups to the Casichelydia,...

Box The Messel Oil Shales Total Preservation Of Mammalian Fossils

Creep Darkness Illustrations

The best-preserved fossils of mammals have been found in the middle Eocene c. 49Myr ago oil shales at Messel, near Frankfurt, Germany Franzen, 1985 Schaal and Ziegler, 1992 . All details of their hair, stomach contents and even internal organs are preserved in some cases. The Messel deposits contain abundant plant remains - laurel, oak, beech, citrus fruits, vines and palms, with rare conifers, and ponds covered by water lilies, which indicate a humid tropical or subtropical climate....

Basal Synapsid Evolution

The synapsids split from the sauroposids anapsids di-apsids in the Mid-Carboniferous, and they expanded in diversity enormously during the Permian, becoming the dominant land animals. The clade is generally divided into two groups. The 'pelycosaurs' Romer and Price, 1940 Reisz, 1986 are a paraphyletic group of six families of basal synapsids that were particularly important in the Early Permian. These were succeeded in the Late Permian by the Therapsida, a diverse clade of small to large plant-...

Conodonta

Conodont Diagram Label

One of the longest-lived groups of early vertebrates, the conodonts, were identified with certainty as fishes only in 1983. Conodont elements, small 0.25-2 mm toothlike structures made from apatite, have been known since 1856, and they are so abundant in many marine rocks from the Late Cambrian to the end of the Triassic that they are used for stratigraphic dating. Particular conodont species, and groups of species, are characteristic of certain stratigraphic zones, and they form the basis of a...

Box The Green River Fishes Of Wyoming

Berycopsis

The Green River Formation of Wyoming, Utah and Colorado preserves some of the most spectacular fish fossils, with over 1 million specimens collected so far. The deposits range in age from late Palaeocene to late Eocene 57-38 Myr ago . Many of the specimens are found in finely layered buff-coloured limestones that were laid down in three large inland lakes, Lake Gosiute, Lake Uinta and Fossil Lake Grande, 2001 . Lake Gosiute and Lake Uinta are interpreted as playa lakes, ephemeral salt-water...

The Great Sea Dragons

Gastralia Elasmosaur

Jurassic and Cretaceous seas were filled with basal neopterygian and teleost fishes and neoselachian sharks that preyed on them Chapter 7 . A broad range of predatory reptiles also hunted fishes, ammonites, belemnites and other marine life. Pterosaurs and croco-dilians seized fishes near the surface see pp. 224-9, 232-7 , and mosasaurs see p. 243 were important carnivores in the Late Cretaceous. Certain groups of birds also fed on marine fishes Chapter 9 ,but the main reptilian predators were...

Box Bird Fingers Or

Alien Tree Dweller

How do you number the fingers of a bird This may seem a bizarre question surely modern bird fingers are unimportant and does it really matter what they are called All birds, from Archaeopteryx onwards, have three fingers. It is clear in the evolution of theropods, that digits four and five equivalent to our ring finger and little finger were reduced and then lost, and that the three digits of Deinonychus and of Archaeopteryx have to be the numbered 1-3. Studies of the embryos of modern birds,...

The Origin Of The Dinosaurs

Herrerasaurus Skeleton

The major radiation of archosaurs in the Mid- to Late Triassic, marked by the split of the Crurotarsi and the Ornithodira see pp. 138-45 , provided a starting point for the radiation of the dinosaurs. The oldest dinosaurs date from the earliest Late Triassic mid-Carnian , although their sister group, Marasuchus, is latest Mid-Triassic in age, which implies an origin of dinosaurs at least by that time. The dinosaurs radiated dramatically during the last 20 Myr of the Triassic, the Norian Stage,...

Box The Chengjiang Fossil Site

The Chengjiang fossil site in Yunnan Province, south-west China, is exciting because it is one of the oldest sources of exceptionally preserved organisms, falling early in the great Cambrian radiation of animals in the sea. The fossils come from different levels through several hundred metres of mainly fine-grained sediments. When the site was discovered, in 1984, it was thought to correspond to the already well-known Burgess Shale, a Middle Cambrian locality in Canada that has yielded numerous...

Cambrian Vertebrates

Myllokunmingia

Until recently, the oldest putative vertebrates were isolated fragments of dermal armour from the Upper Cambrian of North America, and possibly also the superficially amphioxus-like Pikaia from the Mid-Cambrian Burgess Shale of Canada. New discoveries from the Chengjiang locality in China see Box 1.2 , the source also of many exceptionally preserved basal deuterostomes, have extended the range of vertebrates back to the Early Cambrian Shu, 2003 . Myllokunmingia, 28 mm long, is streamlined in...

Development and vertebrate origins

Segmentation Amphioxus

The development of living vertebrates and basal chor-dates indicates a great deal about their ancestry. Embryos may be sliced thinly on a microtome, rather like a mini salami-slicer, and three-dimensional reconstructions are made from tracings of the thin-sections by computerized methods. In addition, and most importantly, studies of the genome allow developmental biologists to relate specific anatomical structures to genes. In many cases, they have found that genes that code for particular...

Box Relationships Of The Basal Primates

The traditional classification of the Order Primates was simple the lemurs, lorises and tarsiers were grouped in the Suborder Prosimii, and the monkeys and apes in the Suborder Anthropoidea cladogram a . The Prosimii were clearly paraphyletic, and they could be diagnosed only with respect to the Anthropoidea, in other words, by the absence of characters. A phyloge-netic approach then is bound to break up the classic Prosimii. An early cladistic analysis of primates Andrews, 1988 suggested that...

Glires Rodents Rabbits And Relatives

Sivacanthion

Rodents and rabbits share numerous derived characters of the skull and dentition, such as the large open-rooted incisor teeth. This and other shared characters have suggested that rodents and rabbits are grouped together as the clade Glires Novacek et al., 1988 Meng et al., 2003 . Molecular evidence for this grouping was at first mixed, but it is now generally accepted see Box 10.6 , although one recent study failed to confirm the mono-phyly of Glires Misawa and Janke, 2003 . The success of the...

The Diversity Of Saurischian Dinosaurs

Dinosaurs have traditionally been divided into two groups, the Saurischia and the Ornithischia, on the basis of their radically different pelvic regions. Indeed, the hindlimbs play a large part in characterizing Di-nosauria and clades within Dinosauria. The saurischian dinosaurs, carnivorous theropods and herbivorous sauropodomorphs such as Plateosaurus and its descendants, will be reviewed here. The ornithischians are considered later see pp. 205-19 . Saurischian and ornithischian dinosaurs...

Box The Replacement Of Perissodactyls By Artiodactyls

Diagram For Mesozoic Plants

The history of hoofed terrestrial plant-eaters seems to show a replacement of the perissodactyls by the artiodactyls. The late Eocene woodlands of North America and Asia were dominated by early horses, rhinos and brontotheres, and then from the mid-Miocene onwards the camels, pigs and ruminants rose to prominence. Today, there are 79 genera of artiodactyls and only six of perissodactyls. The story of how this happened is often taken as a classic example of competitive ecological replacement on...

Illustration Of A Cephalaspis

Gnathostomata Origin Jaws Attachment

The classic theory for the origin of jaws is that they formed from modified anterior gill arches Figure 3.11 a . In jawless fishes, the gill slits are separated by bony or cartilaginous arches. A hypothetical ancestral basal vertebrate with eight gill slits and nine gill arches evolves into an early gnathostome by the loss of four gill slits, and the fusion and modification of the anterior three gill arches. The most anterior may form parts of the floor of the braincase. The second gill arch...

Box Jaws And Feeding In Bony Fishes

Fish Premaxilla

Amia illustrates an intermediate kind of jaw apparatus between that of the palaeonisciforms and the teleosts. The skull of Amia illustration I a shows how the jaws are relatively shorter than in the basal actinopterygians cf. Figure 3.19 d, e . The maxilla is highly mobile and a new element, the supramaxilla, is attached to it. This mobile maxilla hinges at the front and can swing out some way to the side. This is associated with changes to the main jaw joint between the lower jaw and an...

Box The Cave Lion Comes To Life

Allodesmus Skeleton

It is startling to realize that our ancestors in France and Germany were accustomed to the cave lion. Lions and tigers are so much associated with hot climates today, that it is easy to forget that cave lions lived side-by-side with mammoths, woolly rhinos, cave bears and the like until the end of the Pleistocene. Cave lions competed for large prey, such as deer, wild cattle and horses, with early Homo sapiens in Europe. The cave lion figured in Palaeolithic art, including cave wall paintings...

The Early Bony Fishes

Supratemporal Canal

The ray-finned bony fishes, Actinopterygii, arose at least as early as the Silurian, and forms such as Cheirolepis radiated in the Devonian see pp. 66-7 . The clade was traditionally subdivided into three, the chon-drosteans, holosteans and teleosts, which form a rough time sequence of origins and radiations. The terms 'chondrostean' and 'holostean', however, refer to para-phyletic groups that include successive outgroups of the teleosts, and they are used here only in that grade-group sense....

Primate Auditory Bulla

Ring Tailed Lemur Skeleton

Fig. 11.1 A selection of modern primates shown in their natural habitats a the ring-tailed lemur, Lemurcatta b the spectral tarsier, Tarsius c the spider monkey, Ateles d the rhesus monkey, Macaca e the gorilla, Gorilla f the early hominin Australopithecus. Based on various sources. Primates are essentially tree-dwellers, although many lack the remarkable agility of certain South American monkeys and the gibbons. Anatomical changes to permit this kind of activity include grasping hands and feet...

The First Mammals

Adelobasileus

The first mammals appeared in the Late Triassic, but the first fossils are incomplete. Adelobasileus and Sinocon-odon appear to be the most basal mammals,but the first reasonably well-represented mammals are the mor-ganucodontids from the Early Jurassic Kermack et al., 1973,1981 Jenkins and Parrington, 1976 . These early mammals were tiny, with 20-30-mm skulls and total body lengths of less than 150 mm. They probably looked generally like shrews. The oldest known mammal, Adelobasileus from the...

Box Phylogeny Of The Devonian Tetrapods

Stegocephalia Bones Carboniferous

The relationships of the Late Devonian tetrapods see cladogram , and their closest fish relatives, are controversial, not least because many of the specimens are incomplete and are currently under study. Panderichthyids seem to be the closest sar-copterygian relatives of tetrapods, sharing various features of the head and body that are not seen in osteolepiforms. The Tetrapoda, literally those vertebrates with 'four feet', certainly include Ichthyostega and Ventastega as basal forms. Their...

Diversity Of Carboniferous Tetrapods

Pulmonoscorpius Kirktonensis

The tetrapods radiated into about 40 families in the Carboniferous. Classically e.g. Romer, 1966 , the basal tetrapods were divided into three main groups, the Labyrinthodontia, characterized by the labyrinthodont tooth structure shared with derived sarcopterygians, Figure 3.24e , large body size, and compound vertebrae the Lepospondyli, characterized by small size, simple tooth structure, and fused spool-like vertebrae and the Lissamphibia, the modern groups such as frogs and salamanders. It...

The Origin Of Bird Flight

Supra Coracoid Muscles Birds

Birds have wings and feathers, and they can fly. The ability to fly is fundamental and the whole bird skeleton is modified for this mode of locomotion. Flight has also modified the soft anatomy of birds, with flight muscles occupying much of the trunk, and a highly efficient metabolism and respiratory system designed to cope with the demands of fast or long-term flapping of the wings. 9.2.1 The flight apparatus of modern birds In the forelimbs of modern birds Figure 9.3 , the hand and wrist...

Jr J J J

Doleserpeton

F BATRACHOMORPHA G LIMNARCHIA I EUSKELIA M LISSAMPHIBIA O BATRACHIA Q LEPOSPONDYLI R HOLOSPONDYLI S REPTILIOMORPHA T BATRACHOSAURIA F BATRACHOMORPHA G LIMNARCHIA I EUSKELIA M LISSAMPHIBIA O BATRACHIA Q LEPOSPONDYLI R HOLOSPONDYLI S REPTILIOMORPHA T BATRACHOSAURIA A thorough new analysis Ruta et al., 2003a, b confirms aspects of both views see cladogram . Temnospondyls lie on the line to lissamphibians, as discovered by Panchen and Smithson 1988 , and the Lepospondyli is indeed a valid clade and...

Box Relationships Of The Basal Birds

Foramen Triosseum Birds

Archaeopteryx is the basal bird, the sister group of Rahonavis and the Pygostylia Chiappe, 2002b , which includes all other birds see cladogram . The Pygostylia, consisting of the Confuciusornithidae and the Ornithothoraces, share the pygostyle fused caudal vertebrae and a backwards-pointing pubis. The oviraptorosaurs fit in the scheme next, controversially they have a pygostyle and other generalized bird characters Maryanska et al., 2002 , as well as other features of the skull, cervical...

Archonta Primates Tree Shrews And Flying Lemurs

Eocene Skull

The primates see Chapter 11 seem to have affinities with tree shrews and flying lemurs Novacek et al., 1988 , based on that fact that these animals are graced with a 'pendulous penis suspended by a reduced sheath between the genital pouch and the abdomen' In addition, archontans all share some specializations of the ear region of the skull Beard, 1993 . Initially, molecular data were unclear about the reality of the clade Archon-ta,but it is confirmed by current analyses see Box 10.6 . Within...

Classification Of The Mammals

Class Mammalia tAdelobasileus fFamily Sinoconodontidae Subclass Mammaliaformes tFamily Morganucodontidae Infraclass Holotheria tFamily Kuehneotheriidae tOrder Docodonta Superdivision Australosphenida tAusktribosphenidae Division Monotremata Superdivision Theriimorpha tOrder Triconodonta Division Theriiformes tOrder Multituberculata Superlegion Trechnotheria tOrder Symmetrodonta Legion Cladotheria tSuperfamily Dryolestoidea tVincelestes Sublegion Boreosphenida tOrder Deltatheroida Infralegion...

Box Giant Ground Sloth Dung A New Kind Of Data Dump

Tamandua Sloth Short Skull

As is well known to viewers of the Jurassic Park films, palaeontologists have been keen to extract DNA from extinct animals. The early excitement has given way to a more sober view that DNA cannot survive for more than 100,000 years or so, and may be useful only in studies of Pleistocene animals. Hendrik Poinar and colleagues from the University of Munich have been searching for DNA in bones, hair and even excrement. They hit a rich trove of DNA in the coprolites fossil excrement of the Shasta...

Vertebrate Hard Tissues

Cellular Bone Shark Tooth

Bone is a key feature of vertebrates. There are different kinds of bone, and other bone-like hard tissues, and it is important for palaeontologists to understand these, especially when they are trying to classify isolated phos-phatic scales and teeth. Bone is made from mineral and protein components. In fine detail, living bone tissue consists of fibres of the protein collagen on which are deposited tiny hexagonal-prismatic crystals ofapatite. Cellular bone is a living tissue. Typical bone...

Biology Of Plateosaurus

Skull Plateosaurus

The oldest-known dinosaurs are dated as Carnian Late Triassic, 230-220 Myr ago and they include forms such as Eoraptor and Herrerasaurus from Argentina see p. 154 and Coelophysis from North America. One of the most abundant Late Triassic dinosaurs was Pla-teosaurus. The first specimens were found in southwestern Germany in 1837, and since then dozens of skeletons have been collected from over 50 localities in Germany, Switzerland and France, mostly dated as mid-Norian c. 215Myr ago . The best...

Modern Homo sapiens

Oldest Dates

When did our own species originate Undisputed modern Homo sapiens fossils were known from several sites in Africa and Israel dated as 120,000-100,000 years old, and one of the most impressive finds, from Herto, Ethiopia, now extends that age range back to 160,000 years White et al., 2003 . Genetic and molecular evidence points to a comparable date Stringer, 2002a . The human remains from Herto consist of three skulls that are modern in most respects Figure 11.14 ,except that the cranium is...

Flightless Birds Palaeognathae

Flightless Birds The Pleistocene

The palaeognathous palate see Box 9.2 shows primitive theropod and avian characters, but there are several synapomorphies the extensive vomer-pterygoid joint, the elongate basipterygoid processes that meet the pterygoid . Palaeognaths also share synapomorphies in other parts of the skull Cracraft, 1988 . Most living palaeognath groups have short fossil records, extending back to the Miocene or Pliocene only. The oldest palaeognaths, the extinct lithornithi-forms Houde, 1986 , are known from the...

The Marsupials

Marsupials probably arose in the Early Cretaceous of Asia see p. 308 , and they spread from there to North America and then to South America and Australasia Szalay, 1994 . It has generally been assumed that the Australian marsupials form an essentially distinctive clade from those of the Americas, and this is confirmed by recent molecular analyses Amrine-Madsen et al., 2003 . For years, the split distribution of marsupials was a mystery and numerous biogeographical theories were proposed....

Box The Fort Union Formation Of The Crazy Mountain Basin

Mega Leptictis

Mammal fossils were first discovered in 1901 in the Fort Union Formation of the Crazy Mountain Basin, Montana, and large collections were made at a number of localities over the next few years. Simpson 1937 described a typical fauna of 79 species from the Gidley and Silberling Quarries see illustration , dominated by multituberculates such as Ptilodus. Some of the mammals belong to familiar modern groups, such as the early lemur-like animal Plesiadapis see p. 353 , the shrew-like insectivore...

Cephalochordata amphioxus

Another chordate generally reckoned to be related closely to the vertebrates is the amphioxus or lancelet, Branchiostoma, a representative of the Cephalochordata or Acraniata . The adult amphioxus is convincingly chordate-like, being a 50 mm long cigar-shaped animal which looks like a young lamprey or eel, yet lacking a head. Amphioxus swims freely by undulating its whole body from side to side, and it burrows in the sediment on the sea-floor Figure 1.3 a . Amphioxus feeds by filtering food...

Box The First Placental Mammal

Sinodelphys

The oldest remains of placental mammals until recently were teeth and jaws from the very top of the Early Cretaceous, and the record improved only in the Late Cretaceous. A new specimen from the famous Liaoning deposits in China has changed all that Ji et a ., 2002 . The new placental, called Eomaia 'dawn mother' , dated at about 125 Myr ago, is some 50 Myr older than the next oldest complete eutherian skeletons from the uppermost Cretaceous of Mongolia. Eomaia is a shrew-sized animal, some 16...

Phylum Hemichordata Pterobranchs And Acorn Worms

Phylum Saccoglossus

Another unusual group ofliving marine deuterostomes may offer further clues about the origin of the chor-dates. These are the hemichordates, a phylum that in- Phylum Hemichordata Pterobranchs and Acorn Worms 5 eludes two superficially very different kinds of marine animals. The first, the pterobranchs such as Cephalodis-cus Figure 1.4 a,b , are small animals that live in loose colonies on the sea-bed in the southern hemisphere and in equatorial waters. Cephalodiscus has a plate-like head...

Box The Wonderful Birds Of Liaoning

Iberomesornis Skeleton

The first reports of spectacular bird fossils from Liaoning Province in north-east China came out in 1984. Farmers and school children had excavated specimens from limestone quarries in their fields and these were sent piecemeal to palaeontologists in Beijing and Nanjing. More concentrated research began in the 1990s and so far some 15 genera of birds have been described, seven of which are enantiornithines Zhou and Hou, 2002 Zhou et a ., 2003 . The fossiliferous horizons are in the Yixian and...

Carpoids

The fourth group of putative fossil chordates is much more diverse. The carpoids, sometimes called sty-lophorans or calcichordates, are a group of about 60 species of asymmetrical organisms that had a calcitic calcium carbonate outer skeleton of a particular kind in which the mineral is pierced by numerous small holes. They date from the Middle Cambrian to Middle Devonian 520-370 Myr . They consist of two parts Figure 1.8 , a compact body portion and a long segmented appendage. Most authors...