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Hemichordata
Hemichordata
Hemichordata (Stomochordata) A phylum first encountered in the Middle
Cambrian Burgess Shale, British Columbia, Canada. The hemichordates are related to the chordates (
Chordata), for although they lack a
notochord, the gill slits are very similar to those of primitive vertebrates and the dorsal collar nerve cord of hemichordates, which is sometimes hollow, is similar to the dorsal, hollow nerve cord of chordates. Hemichordates are exclusively marine. The body and
coelom are divided into three sections, the middle section bearing gill slits. Development is by a
tornaria larva, indicating affinities with the
Echinodermata; the link between echinoderms and chordates is supported by biochemical evidence, all three groups containing
creatine phosphate in the muscles whereas in all other invertebrates the phosphate is a compound of
arginine. The two classes,
Enteropneusta and
Pterobranchia, may not be descended from a common stock and nowadays are often ranked as separate phyla.
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The anatomy, life habits, and later development of a new species of enteropneust, Harrimania planktophilus (hemichordata: Harrimaniidae) from barkley sound.
Magazine article from: The Biological Bulletin; 4/1/2002; ; 700+ words
; Introduction The deuterostome phylum Hemichordata is composed of three extant classes: the Enteropneusta are solitary worms, the Pterobranchia are colonial tube-dwelling suspension...
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Fenestrate graptolite theoretical morphology: Geometric constraints on lophophore shape and arrangement in extinct hemichordates
Magazine article from: Journal of Paleontology; 3/1/2003; ; 700+ words
; ...Fenestellidae and Polyporidae (Stenolaemata: Bryozoa), and from species of the graptolite genus Dictyonema (Pterobranchia: Hemichordata), all of which are extinct. The zooids of fenestrate bryozoans and fenestrate hemichordates are believed to have filtered...
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New marine biology study findings have been reported from University of Oxford.
Newspaper article from: Ecology, Environment & Conservation; 10/10/2008; 700+ words
; "Pterobranchs are small marine filter feeders in the phylum Hemichordata. Their phylogenetic position and anatomical structure has resulted in pterobranchs featuring in many scenarios concerning the...
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Research on life sciences published by scientists at University of Western Ontario.
Newspaper article from: Biotech Week; 9/2/2009; 700+ words
; ...sequences in members of the animal phyla Porifera, Placozoa, Cnidaria, Mollusca, Annelida, Nematoda, Echinodermata, Hemichordata and Chordata. Using reverse-transcriptase polymerase chain reaction (RT-PCR) with degenerate primers designed to recognize...
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New biology study findings have been published by M. Nomaksteinsky and colleagues.
Newspaper article from: Science Letter; 10/13/2009; 613 words
; ...dorsalization and internalization from a diffuse nerve net coextensive with the skin of the animal, such as enteropneust worms (Hemichordata, Ambulacraria) are supposed to have [3]. We show here that juvenile and adult enteropneust worms in fact have a bona...
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Particle retention and flow in the pharynx of the enteropneust worm Harrimania planktophilus: the filter-feeding pharynx may have evolved before the chordates.
Magazine article from: The Biological Bulletin; 4/1/2002; ; 700+ words
; Introduction The enteropneust worms and bryozoan-like pterobranchs constitute the small deuterostome phylum Hemichordata, which is generally regarded as an early offshoot from the chordate line of evolution (Ruppert and Barnes, 1994). Such...
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Sports active: Childhood? I can't recall last week Fishing lines
Newspaper article from: The Independent on Sunday; 8/10/2003; ; 662 words
; ...College, Cambridge, reader in palaeo- biology and curator of the Sedgwick Museum. His research interests include phylum hemichordata; systematics, evolution and mode of life of graptolites from Middle Cambrian to Carboniferous (but especially Silurian...
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What missing link? Reports of huge gaps in the fossil record have been greatly exaggerated, says geologist Donald Prothero.(Cover story)
Magazine article from: New Scientist; 3/1/2008; ; 700+ words
; ...molecular biology. We also have an array of fossils and living organisms to tell the story of the transition. One of these is the living phylum Hemichordata (the acorn worms and filter-feeding pterobranchs). These are neither ec
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NEW THRUST AREAS TO BE ADDED TO BIO-DIVERSITY
News Wire article from: The Hindustan Times; 3/12/2007; 453 words
; ...of India. Similarly, according to Zoological Survey of India, a total of 91206 species of animals [Invertebrates and Hemichordata (86212), Chordata (4994) = 91206] are known from India. The thrust areas, for biodiversity conservation among others...
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Hemichordata
Book article from: The Columbia Encyclopedia, Sixth Edition
Hemichordata , small phylum of marine invertebrates closely related to both the echinoderms (phylum Echinodermata ) and chordates (phylum...
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Acorn worm
Encyclopedia entry from: The Gale Encyclopedia of Science
...sand or mud burrows. Acorn worms are members of the phylum Hemichordata, which includes two classes — the Enteropneusta...resemble the larvae of Hemichordates. This suggests that the Hemichordata may have given rise to the Chordata and, therefore, vertebrates...
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acorn worm
Book article from: The Columbia Encyclopedia, Sixth Edition
acorn worm see Hemichordata .
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Rhabdopleurida
Book article from: A Dictionary of Zoology
Rhabdopleurida (phylum Hemichordata , class Pterobranchia ) An order of colonial animals in which zooids are pectocaulus . The mesosoma bears one pair of arms. The...
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Planktosphaeroidea
Book article from: A Dictionary of Zoology
Planktosphaeroidea (phylum Hemichordata ) An extant class of hemichordates, of which only two specimens of planktonic, ciliated larvae have been found (in the Bay of Biscay). The internal structures indicate they are hemichordates but the adults are unknown.
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