Birds and mammals are important animal groups today, and the most conspicuous part of the modern fauna.  The mammals originated in the Triassic Period, part of the Mesozoic Era, over 225 million years (Ma) ago, and the first birds arose in the Jurassic Period, over 150 Ma. 

 

The fossil record of the early Mesozoic mammals of the Triassic, Jurassic and Cretaceous periods is particularly good in Great Britain, representing well the early radiations of the initially small forms.  For the first 160 Ma of their history, nearly all of the mammals were smaller than domestic cats, and most were shrew-sized. And yet they diversified considerably at the feet of the contemporaneous dinosaurs.  The British Mesozoic mammal sites are particularly important in the history of palaeontological science, and include the source of the first Mesozoic fossil mammal ever recorded, in the 1820s. Virtually all of the Mesozoic mammal fossils known in the world for the following 100 years were recovered from British sites.

 

The record of Mesozoic birds in Britain is much poorer.  The first bird, Archaeopteryx, is from the Late Jurassic deposits of Germany.  Birds radiated widely in the Cretaceous Period, but mainly outside of Europe.  There are only isolated remains that have been recovered from British rocks so far.

 

After the K–T (Cretaceous ['K']–Tertiary) mass extinction of 65 Ma, major changes occurred in the life on Earth.  Mammals and birds radiated at an accelerated rate to fill niches vacated by dinosaurs and other animals that had died out – the British fossil record of birds and mammals from the Tertiary expands dramatically.  The London Clay, and other Eocene units, have produced famous material of a wide diversity of birds, illustrating early phases in the evolution of modern avian faunas.  The Eocene and Oligocene strata are also a source of a huge diversity of fossil mammals, including some of the earliest horses, primates, artiodactyls, and many other groups.  A major sequence of sites in southern England provides a world-class record of mammalian evolution, plant evolution, and climate change through the period from 56 to 33 Ma.

 

This is the first volume of the GCR series dealing with mammal and bird fossils, charting  nearly 200 million years of Earth history as represented in the networks of Mesozoic and Tertiary mammal and bird sites.  Britain has a long history of collection and study and many specimens have been pivotal in developments in palaeontology, comparative anatomy and evolution.  Many of the sites described are important internationally for faunas of these ages.  The book allows, for the first time, the importance of British fossil mammals and birds to be fully appreciated.