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from article Isoetales

Morphology and anatomy of extant Isoetes. (a) Compact, cormose rhizomorph and unbranched stem of I. melanopoda. (b) More elongate, once-branched rhizomorph and stem of I. andicola. (After W. N. Stewart and G. W. Rothwell, Paleobotany and the…

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from article Literature of science and technology

The Theological Hall of the Strahov Monastery Library, Prague, Czech Republic. This hall contains approximately 42,000 volumes dealing with astronomy, mathematics, and other sciences. (Credit: Copyright © Antonin Vodak/Alamy Stock Photo)

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from article Literature of science and technology

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from article Paracrinoidea

Reconstructions of two paracrinoids showing different proposed living positions. (a) Amygdalocystites from the Late Ordovician of Ontario, Canada, held up some distance in the water column by a curved attached stem (after T. E. Guensburg, J.…

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from article Teleostei

An Atlantic blue marlin (Makaira nigricans) jumping out of the ocean. This popular sport fish is one of the members of the Teleostei. (Photo by Ken Neill, National Marine Fisheries Service, National Oceanic and Atmospheric Administration)

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from article Teleostei

Phylogeny of the Teleostei.

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from article Protolepidodendrales

Early to Middle Devonian Leclercqia complexa, the best-known protolepidodendralean. (a) General growth habit. (b) Pentafid sporophylls bearing sporangia in the fertile region of the axis. (After P. A. Bonamo et al., Leclercqia, Haskinsia, and the…

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from article Extinction (paleontology)

Diversity of marine families and genera in the fossil record. Sharp drops (designated by the numbers 1–5) indicate times of mass extinctions: 1 = Late Ordovician (−12%); 2 = Late Devonian (−14%); 3 = Late Permian (−52%); 4 = Late Triassic (−12%); 5…

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from article Extinction (paleontology)

Times and places of extinctions of large mammals during the Late Pleistocene. (Credit: Adapted from P. S. Martin and R. G. Klein, eds., Quaternary Extinctions: A Prehistoric Revolution, University of Arizona Press, 1984)

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from article Crinoidea

Stemmed crinoid in feeding posture.

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from article Crinoidea

Calyx and proximal stem and arm morphology, vertical section.

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from article Crinoidea

Arm morphology, back (aboral) view.

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from article Crinoidea

Arm morphology, side view.

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from article Coelacanthiformes

Latimeria chalumnae (West Indian Ocean coelacanth), one of the two extant species of the order Coelacanthiformes. (Photo courtesy of the Muséum de Toulouse, France)

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from article Coelacanthiformes

Overall shape and internal structures of Latimeria chalumnae.

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from article Coelacanthiformes

Snout of Latimeria.

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from article Coelacanthiformes

Lower jaw of Latimeria with external bones.

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from article Coelacanthiformes

Endocranium of Latimeria.

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from article Coelacanthiformes

Shoulder girdle of Latimeria.

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from article Acipenseriformes

Atlantic sturgeon (Acipenser oxyrinchus). (Photo by Edith Carson, National Oceanic and Atmospheric Administration)

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from article Rhyniopsida

Rhynia. (a) Reconstruction showing leafless axis, basal rhizome with rhizoids (hairs), and fusiform, terminal sporangia. (b) Photomicrograph of transverse section of petrified stem. (c) Central xylem (vascular) strand. (After J. Walton, An…

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from article Olenellina

A fossilized Olenellus trilobite belonging to the suborder Olenellina. This trilobite was discovered among the Early Cambrian strata of the Eager Formation in British Columbia, Canada. (Credit: Houston Museum of Natural Science)

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from article Fossil primates

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from article Fossil primates

Carpolestes simpsoni, a 55.5-million-year-old plesiadapiform from Wyoming: (a) skeleton as recovered, laid out in approximate anatomical position; (b) reconstruction in life stance on a tree branch; elements in dark gray are known; (c) external…

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from article Fossil primates

Cranium of the omomyoid tarsiiform Teilhardina asiatica, from deposits dated approximately 55 MYA in China: (a) dorsal (top) view as found; (b) left lateral reconstruction. (Credit: Xijun Ni)

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from article Fossil primates

Anjohibe (Madagascar) specimen of Palaeopropithecus ingens (an extinct lemur), mounted in a probable habitat posture. (Credit: American Geological Institute)

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from article Fossil primates

Partly reconstructed skeleton (casts) of Paracolobus chemeroni, a 3.2-million-year-old colobine monkey from Kenya, on exhibit at the American Museum of Natural History in New York. (Credit: Eric Delson)

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from article Fossil primates

Reconstructed skeleton of Proconsul heseloni, an early hominoid (23–14 MYA) from East Africa. Known parts are shaded. (Credit: R. L. Ciochon and R. S. Corruccini)

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from article Science

Italian physicist and astronomer Galileo Galilei (1564–1643) founded the modern scientific method of deducing laws to explain the results of observation and experiment. (Credit: Getty Images)

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from article Kutorginata

Kutorgina, showing (a) exterior of pedicle (ventral) valve; (b) lateral view of shell; (c) exterior of brachial (dorsal) valve. (After C. D. Walcott, Cambrian Brachiopoda, USGS Monogr., vol. 51, 1912)

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from article Fossil seeds and fruits

Early Tertiary fruits and seeds which were found in the Brandon lignite of Vermont. (a) Endocarps of Symplocos. (b) Seeds of grape (Vitis). (c) Seeds of Rubus. (d) Endocarp of extinct species of Nyssa. (e) Seeds of fossil genus of family Rutaceae,…

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from article Pinales

Leaf, branch, and cone characteristics of conifers. (a) Branch of pine with leaves and ovulate cones. (b) Ovulate cone of spruce cut longitudinally to show scales with ovules. (c) Detail of one scale with two ovules. (Copyright © McGraw-Hill…

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from article Pinales

Fertile dwarf shoots of a cordaite and select fossil conifers, representing stages in cone scale evolution. A direct phylogenetic series is not implied. (a) In Cordaites, the ovules were borne terminally on the megasporophylls. (b) Emporia. (c) The…

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from article Selaginellales

Characteristic features of a typical heterophyllous selaginellalean of the Stachygynandrum type. (After T. R. Webster, Developmental problems in Selaginella in an evolutionary context, Ann. Mo. Bot. Gard., 79:633–647, 1992)

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from article Carboniferous

Carboniferous, the fifth period of the Paleozoic Era.

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from article Carboniferous

Development of stratigraphic nomenclature for the Carboniferous.

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from article Carboniferous

Curves outlining the fluctuations of sea level during the Carboniferous. The Mississippian sea-level curve is typical of times when glaciation was not a major factor in controlling sea levels, and the Pennsylvanian sea-level curve is characteristic…

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from article Carboniferous

Paleogeography of the Carboniferous. (a) Early Carboniferous (Mississippian) Tournaisian and Visean epochs, with a major east-west equatorial seaway between Euramerica and Gondwana. (b) Late Carboniferous (Pennsylvanian) Moscovian (or Desmoinesian)…

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from article Carboniferous

Typical shelf sedimentary patterns in Upper Carboniferous depositional sequences. The broken line represents the condensed section that forms during maximum sea-level highstands when sedimentation rates are low. The prominent unconformities at the…

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from article Asteroidea

A five-armed sea star (genus Fromia) resting on coral in the waters surrounding the Maldive Islands. (Credit: Ian Cartwright/Getty Images)

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from article Asteroidea

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from article Asteroidea

The Pacific blue sea star (Linckia laevigata) belongs to the asteroid order Valvatida. This sea star is common in the tropical waters of the Indo-Pacific. (Credit: Comstock Images/Getty Images)

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from article Asteroidea

A large sun sea star (Solaster stimpsoni) in the intertidal-zone waters of Kodiak Island, Alaska. (Credit: Mandy Lindeberg/National Oceanic and Atmospheric Administration)

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from article Asteroidea

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from article Asteroidea

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from article Burgess Shale

Marrella splendens, a characteristic Burgess Shale arthropod. The head shield bears two prominent pairs of spinose extensions; also visible are various appendages that include walking legs and gills. The prominent dark areas appear to represent…

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from article Burgess Shale

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from article Burgess Shale

An articulated halkieriid, Halkieria evangelista, from the Sirius Passet fauna, North Greenland. The body was coated with platelike sclerites, and at either end carried a large shell. (Copyright © Simon Conway Morris)

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from article Platyasterida

Ventral view of an arm and a portion of the disk of Platanaster ordovicus. Note lateral alignment of the arm plates. (After W. K. Spencer and C. W. Wright, Asterozoans, in R. C. Moore, Treatise on Invertebrate Paleontology, Pt. U, Echinodermata 3,…

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from article Rugosa

Rugose corals. (a) Aulacophyllum sp. of horn coral showing the major external features of a solitary coral skeleton; septa pinnately arranged about the cardinal fossula. Devonian, North America, ×0.75. [Most rugose corals need to be studied in thin…

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