PALAEONTOLOGY[online]

Nov12016

Fossil Focus: Acritarchs

Fossil Focus

by Heda Agić*1 Introduction: The acritarchs are a major, long-ranging and successful group of small, capsule-like, organically preserved fossils, which are present in the rock record of most of Earth’s history, dating back 1.8 billion year, or perhaps even as many as 3.4 billion years (Fig. 1). They include mostly single-celled microfossils ranging from a few micrometres (one-millionth of a metre) to one millimetre in size, and each is made up of a sac of organic tissue (vesicle). They are most commonly round, and can be either smooth or covered in spines (Fig. 2). Acritarchs are found in rock deposits that were once marine and terrestrial aquatic environments, and have been described from localities on all continents, as well as from all time periods from the Proterozoic eon (starting 2...

Oct12016

Patterns in Palaeontology: From giants to dwarfs – Estimating the body mass of extinct species

Patterns in Palaeontology

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 ...

Sep12016

Education and Outreach: Dinosaurs in the movies

Education and Outreach

by Szymon Górnicki*1 Introduction: Dinosaurs fit perfectly into the role of movie monsters: many were enormous, or had distinctive characteristics such as spikes, horns, claws and big teeth. The fact that they aren’t found in the modern world (except for birds) excites the imagination, and films represent some of the few opportunities to see them as they may have looked when they were alive. It’s not surprising that the history of movies featuring dinosaurs goes back more than 100 years. The cinematographic rise of the dinosaurs: The first moving picture featuring dinosaurs was Prehistoric Peeps (1905), an adaptation of a cartoon with the same name. The film launched the popular trend of showing primitive humans and non-avian dinosaurs living alongside one another, even though the foss...

Aug12016

Patterns in Palaeontology: A story of vision

Patterns in Palaeontology

by James Fleming*1 Introduction: Photoreception, the ability to perceive light, is a sense shared by many living organisms on Earth. However, only some can take the step beyond merely detecting light levels, and generate an image. Humans are among the animals that have image-forming vision, and are able to see in colour in the day (polychromatic diurnal vision) and in black and white at night (monochromatic nocturnal vision) — the shades of colour that we pick up on an evening out trigger our diurnal receptors at very low levels. However, this is not the only way in which animals can see the world around them. Some species, such as whales and dolphins, can see only monochromatically no matter the time of day, while others see in colour no matter how dark it gets! The elephant hawk-mot...

Jul12016

Patterns in Palaeontology: How and why did the arthropod shed its skin? Moulting in living and fossil arthropods

Patterns in Palaeontology

by Harriet B. Drage*1 Introduction: Arthropods are one of the most successful groups of animals, in the present day and the fossil record. There are more than 1 million described arthropod species, and it has been estimated that there are at least 5 million more undescribed alive today (Fig. 1). This makes up more than 80% of all known animal species! Arthropods also have an extremely diverse fossil record, extending back to the Cambrian Explosion 541 million years ago. For much of the Palaeozoic era (541 million to 252 million years ago), arthropods dominated marine ecosystems, and they have been significant components of all environments since then. The phylum Arthropoda encompasses insects (Hexapoda), crustaceans (such as shrimps and lobsters) and arachnids (such as spiders), a...

Jun12016

Fossil Focus: Mesozoic crocodyliforms

Fossil Focus

by Jonathan P. Tennant*1 Introduction: Crocodilians are truly iconic creatures, and throughout history have inspired stories of dragons and soul-devouring gods. Modern crocodilians are the crocodiles, alligators, caimans and gharials, all part of the crown group Crocodylia (Fig. 1). There are only 23 recognized species alive today, and of these 10 are considered to be endangered, according to the IUCN red list, due to ongoing environmental disruption and human activity. This relative lack of modern diversity stands out in stark contrast to that of their close relatives, the dinosaurs, whose modern descendants, the birds, have about 10,000 species around today! It isn’t obvious from looking at modern birds and crocodiles that they share a common ancestor. For instance, when was the last t...

May12016

Fossil Focus – Marrellomorph arthropods

Fossil Focus

by David Legg*1 Introduction: The Palaeozoic era was a time of incredible biological diversification, which saw the origins and establishment of most modern animal body plans and phyla, particularly during the Cambrian explosion, an event which lasted for about 20 million years during the early Cambrian Period (starting about 542 million years ago), and the subsequent Great Ordovician biodiversification event. During this time, there was a lot of ‘evolutionary experimentation’, with many ancient communities dominated by alien-looking creatures unlike any of their modern counterparts. One such peculiar group is the marrellomorph arthropods, roughly 11 species known exclusively from the lower Cambrian (starting about 542 million years ago) to the lower Devonian period (ending about 393 mil...

Apr12016

Fossil Focus: Cinctans

Fossil Focus

by Imran A. Rahman*1 Introduction: The fossil record of early animals — which dates back at least to the Cambrian period, more than 500 million years ago — is packed full of bizarre sea creatures that seem, at first glance, rather different from anything alive today. These include the armoured slug-like Wiwaxia, the spiny worm-like Hallucigenia and Earth’s first big predator, Anomalocaris. Collectively, these fossils were termed “weird wonders” by the evolutionary biologist Stephen Jay Gould; they possess some, but not all, of the characteristics shared by their modern relatives, and so are crucial for understanding the early evolution of animal phyla. This article focuses on a peculiar extinct group of Cambrian weird wonders called the cinctans, which look more like tennis racquets t...

Mar12016

Fossil focus: Giraffidae — where we’ve been and where we’re going

Fossil Focus

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...

Feb12016

Fossil Focus: Ammonoids

Fossil Focus

by Kenneth De Baets1, René Hoffmann2, Jocelyn A. Sessa3 and Christian Klug4. Introduction: Ammonoids (Ammonoidea) are an extinct group of marine invertebrates with an external shell. They were cephalopods, and hence closely related to modern cuttlefish, squid, octopuses and the pearly nautilus. In a non-scientific context, they are commonly called ammonites, but that term really includes only Jurassic and Cretaceous forms in its stricter scientific sense. The Ammonoidea as a whole lived from the Early Devonian to the earliest Palaeogene period, covering a timespan of about 350 million years. Normally, only their shells, also called conchs, or their internal moulds are found in the fossil record. Conchs from adult ammonoids range from about 5 millimetres to 2 metres in diameter. Due to...