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The Mesozoic age or formation.

any genera and species, and all are extinct, the typical forms having existed only in the Mesozoic age, when they were exceedingly numerous. They differ from the nautili in having the margins of the septa very much lobed or plaited, and the siphuncle dorsal. Also called serpent stone, snake stone, and cornu Ammonis.…

An extensive group of fossil cephalopods often very abundant in Mesozoic rocks. See Ammonite.

An extinct animal of large size, known from its three-toed footprints in Mesozoic sandstone.

A genus of ganoid fishes, of the order Dipnoi, first known as Mesozoic fossil fishes; but recently two living species have been discovered in Australian rivers. They have lungs so well developed that they can leave the water and breathe in air. In Australia they are called salmon and baramunda. See Dipnoi, and Archipte…

Diagram under Geology. -- Cretaceous period (Geol.), the time in the latter part of the Mesozoic age during which the Cretaceous formation was deposited.

An order of extinct mesozoic reptiles, mostly of large size (whence the name). Notwithstanding their size, they present birdlike characters in the skeleton, esp. in the pelvis and hind limbs. Some walked on their three-toed hind feet, thus producing the large "bird tracks," so-called, of mesozoic sandstones; others wer…

A genus of fossil encrinoidea, from the Mesozoic rocks.

lizards. It is the only living representative of the order Rhynchocephala, of which many Mesozoic fossil species are known; -- called also Sphenodon, and Tuatera.

A term applied to many American Mesozoic strata, in which the characteristics of the Jurassic and Triassic periods appear to be blended. -- Ju`ra-tri*as"sic, a.

Of the age of the middle Mesozoic, including, as divided in England and Europe, the Lias, Oölite, and Wealden; -- named from certain rocks of the Jura mountains. -- n.

More recent than the Paleozoic, -- that is, including the Mesozoic and Cenozoic.

A group of Mesozoic birds having the jaws armed with teeth, as in most other vertebrates. They have been divided into three orders: Odontolcæ, Odontotormæ, and Saururæ.

An extinct order of Mesozoic marine reptiles including the genera Plesiosaurus, and allied forms; -- called also Sauropterygia.

eptiles, having a very long neck, a small head, and paddles for swimming. It lived in the Mesozoic age.

An extinct order of flying reptiles of the Mesozoic age; the pterodactyls; -- called also Pterodactyli, and Ornithosauria.

Pertining to, or of the same horizon as, certain Mesozoic strata of the Rhetian Alps. These strata are regarded as closing the Triassic period. See the Chart of Geology.

hilis. Secondary accent. See the Note under Accent, n., 1. -- Secondary age. (Geol.) The Mesozoic age, or age before the Tertiary. See Mesozoic, and Note under Age, n., 8. -- Secondary alcohol (Chem.), any one of a series of alcohols which contain the radical CH.OH united with two hydrocarbon radicals. On oxidation t…

An extinct order of amphibians found fossil in the Mesozoic rocks; called also Stegocephali, and Labyrinthodonta.

nus of pearly bivalve shells, numerous extinct species of which are characteristic of the Mesozoic rocks. A few living species exist on the coast of Australia.