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from article Galliformes
White-tailed ptarmigan (Lagopus leucurus), Glacier National Park, Montana. (Photo by Gerald and Buff Corsi, copyright © California Academy of Sciences)
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Image
from article Echinoida
Tripneustes ventricosus (Lamarck), tropical eastern and western Atlantic, found at depths of 0–55 m (0–180 ft). (From G. Hendler et al., Sea Stars, Sea Urchins and Allies: Echinoderms of Florida and the Caribbean, Smithsonian Press, Washington, DC,…
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from article Echinoida
A pyramid from Aristotle's lantern, showing epiphyses joined and tooth with keel. (After H. L. Hawkins, The lantern and girdle of some Recent and fossil Echinoidea, Philos. Trans. R. Soc. Lond. Ser. B, 223:617–649, 1934)
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from article Echinoida
An ambulacral plate from the test, with the lowest element being the largest. (After T. Mortensen, A monograph of the Echinoidea: Camarodonta, C. A. Reitzel, Copenhagen, 1943)
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from article Euryalida
Aboral body of a basket star, Euryale aspera (family Euryalidae, order Euryalida), clinging to a red soft coral colony and spreading its branching arms.
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from article Euryalida
A snake star, Astrochele pacifica (family Gorgonocephalidae, order Euryalida): (a) aboral body; (b) aboral arms; and (c) a scanning electron microscope (SEM) image of a separated microscopic hook. (Credit for photo a: Shimoda Marine Research Center,…
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from article Cordaitales
Cross sections of cordaitean stems, with simple wood. Left, Cordaixylon iowensis, with septate pith. Right, Mesoxylon priapi, with solid pith. (Photographs by M. L. Trivett)
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from article Cordaitales
Shoot of Cordaixylon dumusum illustrating strap leaves and nonaxillary Cordaitanthus-type cones. (Courtesy of G. W. Rothwell)
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from article Cordaitales
Compound Gothania-type cone of Mesoxylon priapi with bracts subtending secondary shoots. (Courtesy of M. L. Trivett)
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from article Pinnipeds
Walrus (Odobenus rosmarus). (Credit: Donna Dewhurst Collection/U.S. Fish and Wildlife Service)
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from article Pinnipeds
Steller sea lion and pup (Eumetopias jubatus). (Credit: Alaska Image Library/U.S. Fish and Wildlife Service)
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from article Pinnipeds
Evolutionary relationships and stratigraphic ranges of major groups of pinnipeds. Shaded bars correspond to known ranges, and white bars correspond to inferred ranges. Ma = million years ago. (Copyright © McGraw-Hill Education)
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from article Eocrinoidea
Reconstructions of Cambrian and Ordovician eocrinoids. (a) Gogia spiralis, from the Middle Cambrian of Utah, showing the primitive holdfast; sutural pores between the numerous thecal plates; and long, spiraled brachioles attached to the summit…
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from article Meteor
Leonid meteor shower observed at the Modra Astronomical Observatory in Slovakia through a fisheye lens. The exposure on November 16–17, 1998, lasted 4 h. About 150 bolides brighter than magnitude −2 can be seen; the brightest fireball is about…
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from article Conulariida
Conulariid morphology. (a) Paraconularia byblis, a well-preserved specimen in siderite (iron carbonate) from the Carboniferous (Mississippian) of Ohio showing two adjacent sides meeting at a deep corner groove (arrow). Ridges along each side meet at…
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from article Conulariida
Conulariid paleoecology and taphonomy. (a) Cluster of Conularia congregata compacted in shale from the Devonian of New York. The specimens show apical walls (lower arrow), indicating detachment from, or nonpreservation of, their attachment stalks.…
Image
from article Pteridosperms
Suggested reconstruction of Callistophyton. (After G. W. Rothwell, The Callistophytaceae (Pteridospermopsida): I. Vegetative structures, Palaeontographica, 151B:171–196, 1975)
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from article Pteridosperms
Transverse section of Stenomyelon. (From C. B. Beck, The appearance of gymnosperm structure, Biol. Rev., 45:379–400, 1970)
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from article Craniiformea
Isocrania egnabergensis (Retzius): (a) dorsal valve interior; (b) dorsal valve exterior; (c) ventral valve interior; (d) ventral valve exterior; (e) complete shell, lateral view, dorsal valve above; 8 mm (0.32 in.) in width. Danocrania tuberculata…
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from article Craniiformea
Muscle system of Novocrania viewed (top) dorsally and (bottom) laterally. (Adapted from O. M. B. Bulman, Muscle systems of some inarticulate brachiopods, Geol. Mag., 76:434–444, 1939; after R. L. Kaesler, ed., Treatise on Invertebrate Paleontology,…
Image
from article Proboscidea
African bush elephant (Loxodonta africana). (Credit: Gary M. Stolz/U.S. Fish and Wildlife Service)
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from article Proboscidea
Indian elephant (Elephas maximus) in Kerala region, southern India. (Credit: Nidish K. Viswanathan)
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from article Lycophyta
Cladistic phylogeny of the Lycophyta. Only Huperzia and Lycopodium include extant species. (After P. G. Gensel, Phylogenetic relationships of the zosterophylls and lycopsids, Ann. Mo. Bot. Gard., 79:450–473, 1992)
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from article Lycophyta
Reconstruction of Sawdonia ornata. (After A. R. Ananiev and S. A. Stoepanov, Finds of sporogenous organs of Psilophyton princeps Dawson emend, Treat. Tomsk Lab. St. Univ. Geol. Ser., 202:30–46, 1968)
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from article Lycophyta
Lycopodiella annotina, an extant club moss. (After W. N. Stewart and G. W. Rothwell, Paleobotany and the Evolution of Plants, 2d ed., Cambridge University Press, 1993)
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from article Ursa Major
Modern boundaries of the constellation Ursa Major, the Great Bear. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension…
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from article Inadunata
Inadunates. (a) Monocyclic. (b) Dicyclic.
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from article Calcichordates
Evolutionary relationships of calcichordates (Soluta, Cornuta, and Mitrata). The oldest events are at the bottom and the most recent are at the top. D = Dendrocystoides; C = Cothurnocystis; M = Mitrocystites.
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from article Calcichordates
The Cephalodiscus-like ancestor, by falling over on its right side, became the dexiothetic ancestor. This form acquired a calcite skeleton and gave rise both to the echinoderms and to the chordates.
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from article Calcichordates
The three main groups of calcichordates. (a) Soluta; dorsal view of Dendrocystoides (Ordovician, Scotland, about 440 million years old). (b) Cornuta; dorsal view of Cothurnocystis (Ordovician, Scotland, about 440 million years old). (c) Mitrata;…
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from article X-ray telescope
Wolter type I x-ray telescope, in this case the Chandra X-ray Observatory. Two surfaces of revolution (paraboloid and hyperboloid) reflect the incident x-rays to a common focus. The horizontal scale is greatly compressed. (Chandra X-ray Center)
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from article X-ray telescope
A composite image of the Sun using the Solar Dynamics Observatory (SDO). The x-rays are shown in three colors: red (21.1 nm), green (19.3 nm), and blue (17.1 nm). (Lockheed Martin Solar and Astrophysics Laboratory, Smithsonian Astrophysical…
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from article X-ray telescope
Schematic of a microcalorimeter. An absorber is kept very cold. Then when an x-ray hits, the temperature change is measured. From this, the energy of the x-ray can be computed. (NASA)
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from article Tertiary
Tertiary, the first period of the of the Cenozoic Era.
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from article Tertiary
Baluchitherium, the largest land mammal known, from the Tertiary (Oligocene Epoch) of Asia. It was 18 ft (5.4 m) high at the shoulders. (After R.A.Stirton, Time, Life and Man, Wiley, 1959)
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from article Tertiary
Mollusk fossils used by Lyell to zone the Tertiary. (a) Miocene. (b) Eocene. (After C.Lyell, Principles of Geology, 1833)
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from article Sirenia
West Indian manatee (Trichechus manatus) and calf. (Credit: Galen Rathbun/U.S. Fish and Wildlife Service)
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from article Sirenia
The dugong (Dugong dugon) is the only extant sirenian in the family Dugongidae. (Credit: Niklas Flindt)
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from article Xenacanthidae
Xenacanthus meisenheimensis, from the Permo-Carboniferous Saar-Nahe Basin, southwestern Germany. (After U. H. J. Heidtke, 2003)
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from article Ornithischia
Pelvis of the Lower Jurassic ornithischian dinosaur Scelidosaurus harrisonii from England (Natural History Museum, London specimen BMNH R1111). The front of the animal is to the right of the photograph. Note that the pubis bone has rotated backward…
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from article Ornithischia
Skull of the Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki from South Africa (Iziko: South African Museum specimen SAM-PK-K1332). Note the predentary bone at the tip of the lower jaw, the palpebral bone crossing the eye socket, and…
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from article Rocket astronomy
Launch of a NASA Black Brant XII sounding rocket. (NASA Goddard Space Flight Center)
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from article Rocket astronomy
Current NASA sounding rockets (2012). (NASA Sounding Rockets Projects Office, Wallops Flight Facility)
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from article Rocket astronomy
Lift capability of NASA sounding rockets. Apogee is shown as function of payload weight.
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from article Homalozoa
Examples of homalozoans. (a, b) Phyllocystis blayaci, an Early Ordovician cornute stylophoran from Morocco. Note heavier, elongate, marginal plates around thin-plated, upper (a) and lower (b), central areas in theca; about half of the attached,…
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from article Stenolaemata
Some morphologic features of autozooids of Cyclostomata, the only living order of stenolaemates.
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from article Scorpius
Modern boundaries of the constellation Scorpius, the Scorpion. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension representing…
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from article Ostracoda
Ostracode, a typical marine species of the suborder Podocopina, Macrocypris minna. (a) Male with left valve removed to show appendages; the internal paired Zenker's organs act as pumps to eject the exceptionally large sperm. (b) Male left first leg,…
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from article Ostracoda
Biodiversity of the eight orders of Ostracoda showing numbers of families known from the fossil record.
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from article Pseudoborniales
Pseudobornia node with a whorl of three leaves.
