Heidelberg man
Advanced human remains from the middle Pleistocene of Africa and Europe in rocks dated from 0.8 to 0.4 Myr ago have suggested that the species Homo heidelbergen-sis, established in 1907 for a jawbone from Germany, might be a valid species. English remains consist of a tibia and some teeth Roberts et al., 1994 , associated with Acheulean tools. These perhaps indicate a unique radiation of humans in the mid-Pleistocene of Europe that were more derived than H. erectus, but ancestral to the...
is
H H I Phase I expression Phase I Hox D-9, D-10 I hB-BH H I Knockout phenotype I Phase II expression Hox D-9, D-10, D-11, D-12, D-13 I Knockout phenotype I Phase III expression Hox A-13, D-13 Hox A-13, D-13, D-12, D-12, D-11, D-10 Tetrapod limb development. Developmental interpretation of the forelimbs of Eusthenopteron a and Acanthostega b . The developmental axis solid line branches radial elements dashed lines in a preaxial anterior direction in both forms, and the digits of tetrapods...
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
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
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 Trq
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
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
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
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
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
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
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
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
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
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
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
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 Not
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
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
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
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
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
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
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
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
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
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
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
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
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,...
Embryology and the position of the anus
In early development each animal starts as a single cell. Soon this cell begins to divide, first into two cells, then four, then eight, sixteen, and so on Figure 1.5 a-c . Eventually a hollow ball of cells is produced, called the blastula stage Figure 1.5 d . A pocket of cells then moves inwards, forming the precursor of the gut and other internal structures. The opening of this deep pocket is called the blastopore.You can imagine pushing in the walls of a hollow rubber squash ball with your...