Year: 2012

Fossil Focus: Animal embryos

Fossil Focus
by John Cunningham*1 Introduction: Animal embryos are small (typically less than 1 millimetre across), soft and squidgy, so it was traditionally considered impossible for them to be preserved in the fossil record. However, over the past 15 years or so a series of remarkable discoveries have shown that embryos can indeed be fossilized under exceptional circumstances. The microscopic fossils that have been identified as embryos are almost exclusively from the Ediacaran and Cambrian periods, around 635 million to 488 million years ago. This spans the period of time when the major groups of animals are thought to have first appeared, so these fossils allow palaeontologists to study the embryology of some of the earliest animals, shedding light on the evolution of development. The first fo

Fossil Focus: Vertebrate tracks and trackways

Fossil Focus
by Peter Falkingham*1 Introduction: The fossilized footprints and trackways of vertebrates are often overlooked in favour of the skeletal remains of the animals that made them. At museums, for instance, many more people will crowd around the dinosaur skeletons than around the dinosaur tracks nearby, and yet fossilized tracks can provide us with information about extinct animals that is simply not available from the bones alone. A track is the result of an interaction between an animal and a surface, or substrate. The final track shape (morphology) is directly determined by three factors: Producer: the shape of the track-maker's foot Behaviour: the motion and loading (kinematics and kinetics) of that foot Substrate: the conditions of the surface when the track is made (sandy, mudd...