Theropods Week 1

Dollo's law

Louis Dollo's 'law of irreversibility', which is no longer accepted, was an evolutionary theory suggesting that lost structures of ancestors could not be regained by decedents.

Saurischia

Lizard-hipped dinosaurs; have a forward facing orientation of the pubis in the pelvis. Includes Theropoda and Sauropodomorpha.

Sir Richard Owen

Coined the term 'dinosauria' in 1842, and was instrumental in the early description, publication and display of the earliest dinosaur finds.

Ornithischia

Bird-hipped dinosaurs; have a backward facing orientation of the pubis in the pelvis. Includes Thyreophora, Ornithopoda and Marginocephalia.

Sauropodomorpha

Clade of saurischian dinosaurs that includes the long necked sauropods and their basal relatives such as Plateosauria (formerly referred to as Prosauropods). Characteristics include large nares, elongated necks, and spatulate teeth.

Theropoda

meaning 'beast feet', theropods were a group of typically bipedal saurischian dinosaurs originating in the Late Triassic period, that evolved a number of bird-like features, such as pneumatic bones and a furcula. This clade includes extant birds.

Charles Darwin

'The father of evolutionary science' who's most well known work: 'On the Origin of Species', published in 1859, suggested that inherited traits were changed over time by natural selection and that species descended from common ancestors becoming "branches in the lines of descent".

Thomas Huxley

Darwin's Bulldog; early champion of Darwin's ideas on natural selection. He became the first person to draw comparisons between carnivorous dinosaurs and birds, by comparing a skeleton of Compsognathus with the skeleton of Archaeopteryx.

Gerhard Heilmann

Early twentieth century palaeontologist who, on the basis of Dollo's Law, rejected theropods as the ancestors of birds in favour of thecodonts.

John Ostrom

Paradigm-shifting palaeontologist who first discovered and described Deinonychus; he made anatomical and behavioural comparisons between theropods and birds which gained large scale acceptance in the late 1960s/70's and catalyzed the 'Dinosaur Renaissance'.

Pneumatization

A process which creates hollow, lightweight bones in the skeleton; a condition shared by both birds and non-avian theropod dinosaurs.

Air Sacs

Air pockets in the bones that form part of the respiratory system in birds, and probably theropod dinosaurs.

Keel

Structure on the sternum that provides a broad surface for the attachment of the flight muscles; less pronounced in non-flying birds/theropods

Sternum

The breastbone of vertebrates- a site for rib attachment that is particularly large in flying birds/theropods as it is also the main attachment sight for flight muscles.

Pectoral Girdle

Formed by the shoulder blades or scapulae, the wishbone or furcula and the coracoids.

Scapulae

Shoulder blades in vertebrate animals.