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Oligocene epoch
(Encyclopedia)Oligocene epoch ŏlˈəgōsēnˌ [key], third epoch of the Tertiary period in the Cenozoic era of geologic time, lasting from 38 to 24 million years ago. More of North America was dry land during the ...Iguanodon
(Encyclopedia)Iguanodon ĭgwănˈədŏn [key] [Gr., = iguana tooth], herbivorous ornithiscian dinosaur, characterized by teeth similar to those of the iguana, a horny beak, spikelike thumbs, and a powerful tail...Cambrian period
(Encyclopedia)Cambrian period [Lat. Cambria=Wales], first period of the Paleozoic geologic era (see Geologic Timescale, tablegeologic timescale, table) extending from approximately 570 to 505 million years ago. It ...trilobite
(Encyclopedia) CE5 Dorsal view of a trilobite trilobite trīˈləbītˌ [key], subphylum of the phylum Arthropoda that includes a large group of extinct marine animals that were abundant in the Paleozoic era. Th...Leidy, Joseph
(Encyclopedia)Leidy, Joseph līˈdē [key], 1823–91, American scientist, b. Philadelphia, grad. Univ. of Pennsylvania medical school. From 1853 he taught anatomy at his alma mater. He was also professor of natura...monkey-puzzle tree
(Encyclopedia)monkey-puzzle tree, evergreen tree (Araucaria araucana) native to Chile and widely cultivated elsewhere as an ornamental. The symmetrical branches have an unusual angularity and are completely covered...Piltdown man
(Encyclopedia)Piltdown man, name given to human remains found during excavations (1908–15) at Piltdown, Sussex, England, by Charles Dawson. The find led to much speculation and argument. Since they were found wit...ginkgo
(Encyclopedia)ginkgo gĭngˈkō [key] or maidenhair tree, tall, slender, picturesque deciduous tree (Ginkgo biloba) with fan-shaped leaves. The ginkgo is native to E China, where it was revered by Buddhist monks an...shale
(Encyclopedia)shale, sedimentary rock formed by the consolidation of mud or clay, having the property of splitting into thin layers parallel to its bedding planes. Shale tends to be fissile, i.e., it tends to split...Old Red Sandstone
(Encyclopedia)Old Red Sandstone, series of red and brown sandstones, conglomerates, and shales deposited in Wales and Scotland and in England near the Welsh and Scottish borders in the Devonian period of geologic t...Browse by Subject
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