Fossil embryos reveal early animals.Paleontologists have discovered the oldest known examples of animal embryos, preserved within tiny fossilized fos·sil·ize v. fos·sil·ized, fos·sil·iz·ing, fos·sil·iz·es v.tr. 1. To convert into a fossil. 2. To make outmoded or inflexible with time; antiquate. v.intr. eggs in China and Siberia. The recognition of these 540-million-year-old embryos illuminates a route scientists could take to determine when animals originated--a subject of much debate. The new work builds on research by Chinese scientists, who 20 years ago described egglike fossils in rocks from the early Cambrian The Early Cambrian (also known as the Caerfai, Waucoban, or Georgian) is the first of three geological epochs of the Cambrian period. It spans the time between 542 ± 0.3 Ma and 513 ± 2 Ma (million years ago). period. They named these half-millimeter-wide, globe-shaped fossils Olivooides. Now, analysis of the eggs with a scanning electron microscope scan·ning electron microscope n. Abbr. SEM An electron microscope that forms a three-dimensional image on a cathode-ray tube by moving a beam of focused electrons across an object and reading both the electrons scattered by the object and reveals that they contain embryos from a known Cambrian animal, report Stefan Bengtson of the Swedish Museum of Natural History The Swedish Museum of Natural History (in Swedish Naturhistoriska riksmuseet, literally, the National Museum of Natural History), in Stockholm, is one of two major museums of natural history in Sweden, the other one being located in Gothenburg. in Stockholm and Yue Zhao of the Institute of Geology in Beijing. The researchers described the findings in the Sept. 12 Science and last month at a meeting of the Geological Society of America The Geological Society of America (or GSA) is a nonprofit organization dedicated to the advancement of the geosciences. The society was founded in New York in 1888 by James Hall, James D. in Salt Lake City. Bengtson and Zhao discovered telltale spikes on parts of the embryos that match protrusions on much larger, cone-shaped fossils that apparently belonged to juvenile forms of jellyfish jellyfish, common name for the free-swimming stage (see polyp and medusa), of certain invertebrate animals of the phylum Cnidaria (the coelenterates). The body of a jellyfish is shaped like a bell or umbrella, with a clear, jellylike material filling most of the . By examining many fossils, the researchers tracked the animal's embryonic development through several stages of cell division as well as its growth after hatching. In the past, paleontologists had presumed that egg and embryo fossils were scarce, especially from times near the dawn of animal life. "Maybe eggs are not at all uncommon. Maybe we've been just looking for Looking for In the context of general equities, this describing a buy interest in which a dealer is asked to offer stock, often involving a capital commitment. Antithesis of in touch with. them in the wrong way," says Bengtson. When he and Zhao used their new knowledge to examine early Cambrian rocks from Siberia, they discovered a set of embryos from an as-yet-unknown animal. Genetic evidence suggests that animals may have originated 1,200 million years ago, but paleontologists have failed in their attempts to find adult animal fossils in rocks more than 600 million years old. The embryo discoveries suggest that researchers should try searching these ancient rocks for tiny eggs, which may have fossilized more readily than adult animal bodies, says Bengtson. "This is a promising avenue to search for the missing fossil record." |
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