by David Button1 Introduction The sauropods are some of the most iconic prehistoric vertebrates. Their unique body plan — long neck and tail, bulky body and proportionately tiny head — is perhaps the most famous image of ‘a dinosaur’ and the group includes household names such as Brontosaurus, Diplodocus and Brachiosaurus. Sauropod remains have been found on every continent, and they were one of the most important groups of terrestrial giant plant eaters, or megaherbivores, throughout the Jurassic and Cretaceous periods (201 million to 66 million years ago). The single most notable sauropod trait is their gigantic size: the largest sauropods would have measured more than 40 metres from nose to tail, reached 18 metres tall and tipped the scales in the region of 60–80 tonnes, making them t
by Charlotte Brassey1 Introduction Body mass is so fundamental to an organism that it is often overlooked, yet it has considerable importance in animal biology. It is, quite literally, the amount of matter making up an individual. On a day-to-day basis, we encounter values for body mass as we step onto our bathroom scales and are encouraged to maintain a healthy weight (not too heavy or too light). Veterinarians are interested in body mass for much the same reason: the weight of an animal can provide an indication of its health and is commonly used to plan medical treatments. Body mass is also tied to an animal’s physiology (including speed of metabolism and length of pregnancy), ecology (diet, home-range size) and behaviour (social status, aggression). For these reasons, zoologists are
by Chris Basu1 Giraffes (Giraffa camelopardalis) are charismatic and iconic animals. Together with their closest living relatives, okapis (Okapia johnstonii), they are remnants of an otherwise diverse group of even-toed ungulates - Giraffidae. Giraffids are ruminants (they have a specialized four-chambered stomach), and are related to other ruminant groups such as bovids (including cattle and antelopes), cervids (deer) and antilocaprids (pronghorns). Ruminants use microbes in their stomachs to ferment and break down vegetation that would otherwise be impossible to digest. The origins of Giraffidae are hazy. DNA analysis confirms that they are a valid group, and that they diverged from other ruminants approximately 25 million years ago. This agrees with what is generally understood f
By Ryan Marek*1 Introduction A literal translation of ichthyosaur is 'fish lizard', yet ichthyosaurs were neither fish nor members of the lizard family; they were a group of highly successful marine reptiles who lived from the early Triassic period to the late Cretaceous period, around 248 million to 90 million years ago. Ichthyosaurs were among the first diapsids (a group of animals which have evolved two holes on each side of their skulls, includes birds and all reptiles except turtles) to evolve a thunniform (fish-like) body plan as an adaptation to life in the sea (Fig. 1). They were also the first air-breathing vertebrates to evolve this body plan; the only other group to do so was the whales and dolphins, millions of years later. Most ichthyosaurs after the Triassic had the fish-l
by Sven Sachs1 and Benjamin P. Kear2 Introduction: Elasmosaurs were a group of marine reptiles that lived during the Cretaceous period (about 145 million to 66 million years ago). They were fully adapted to an aquatic lifestyle, and had a distinctive body plan comprising a compact, streamlined body, long, paddle-like limbs and an extremely elongated neck with a large number of vertebrae (Fig. 1). The first named elasmosaur was Elasmosaurus platyurus from the Late Cretaceous (Campanian stage, about 83.6 million to 72.1 million years ago). It was found in Kansas and described by the famous US scientist Edward Drinker Cope (1840–97, Fig. 2), who, when he first wrote about it in 1868, believed that the almost complete series of 72 neck vertebrae came from a massively long tail. Today, many
by Dave Hone(1) Introduction: Thanks to Tyrannosaurus rex, the tyrannosaurs are among the most famous of the extinct dinosaur groups. They receive a disproportionate amount of attention in the media and hold a firm place in the public imagination. However, this also means that more misconceptions and out-of-date ideas are promoted for this group than any other, and the excess of attention detracts from the fact that they are a genuinely interesting clade of animals. In fact, thanks to a great deal of research effort, we may know more about tyrannosaurs than any other group of dinosaurs from the Mesozoic era (252 million to 66 million years ago). This alone makes them a key part of palaeontology. All tyrannosaurs were carnivores, and although the most famous forms from the last part o...
by James M. Neenan1 Introduction: The placodonts were a group of marine reptiles that lived in shallow coastal waters, and mostly ate hard-shelled prey such as mussels and other bivalves (that is, they were durophagous). They lived during the Triassic period, and have so far been found in modern-day Europe, the Mediterranean and South China (Fig. 1). The Triassic was a very special time for marine-reptile evolution, with their greatest morphological diversity being known from this period. The beginning of the Triassic was characterized by the largest mass-extinction event that has ever occurred on Earth (the Permian–Triassic extinction), in which around 95% of all marine life went extinct. This marked the start of the Mesozoic era (the ‘age of dinosaurs’ that contains the Triassic, Juras
by Bernat Vila1 Introduction Of all the dinosaur fossils, skeletons are most fascinating to the public, because they represent real evidence of dinosaurs’ existence. When the study of skeletons is combined with information from fossilized footprints (which show how and how fast dinosaurs walked), dinosaurs seem to come to life: the body seems to move and interact with the substrate. But in real life, dinosaurs lived in similar ways to modern animals, and by asking the proper questions of some singular fossils, researchers can find out about their biology, such as their feeding strategies, growth and reproduction. Fossil eggs and nests are the only evidence about the reproductive biology of dinosaurs. The study of oological fossils Eggs and nests are called indirect fossils because they
by Holly M. Dunsworth Humans would not have evolved if the ancestors of the African great apes had not. The ape fossil record begins 23 million years ago with the earliest putative apes, including Morotopithecus and Proconsul (Figure 1), from sites in East Africa, followed by many others throughout Africa, Europe and Asia. Although this record is fairly rich, it has done no better than DNA-based estimates at helping researchers to determine how living apes are related. Genetic studies estimate that gorillas split off from other apes about 9 million to 8 million years ago, and that the ancestors of bonobos and chimpanzees began evolving separately from the ancestors of humans 7 million to 6 million years ago. Comparative anatomy, physiology, behaviour and genetics provide enough e...
by Christine Janis1 Ladies and gentlemen, I give you tree-kangaroos. These wonderful animals can, in myriad ways, demonstrate the power of evolutionary biology and geology in explaining the patterns we see in modern ecosystems. Here, I want to show how palaeontologists can piece together multiple lines of evidence to understand the evolutionary relationships of fossil and living organisms. Introduction First, a little introduction to the tree-kangaroos (genus Dendrolagus). These small, tree-dwelling (‘arboreal’) marsupials live in the rainforests of Australia and New Guinea, and belong to the macropod family of animals, which also includes ground-dwelling kangaroos and wallabies. They grow up to about 80 centimetres long, not including the tail, and mainly eat vegetation (see Fig