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Information about Hemichordata

Hemichordata
Fossil range: Cambrian - Recent
Scientific classification
Kingdom:Animalia
Subkingdom:Eumetazoa
Superphylum:Deuterostomia
Phylum:Hemichordata
Bateson, 1885
Classes


Hemichordata is a phylum of worm-shaped marine deuterostome animals, generally considered the sister group of the echinoderms. They date back to the Lower or Middle Cambrian and include an important class of fossils called graptolites, most of which became extinct in the Carboniferous. They seem to have a primitive form of notochord, but this is most likely the result of convergent evolution. A hollow neural tube exists among some species (at least in early life), probably a primitive trait they share with the common ancestor of chordata and the rest of the deuterostomes.

The Body of Hemichordates are divided into three parts, proboscis, collar and trunk. They have open circulatory systems also complete digestive tract but the musculature in their gut is very poorly developed, and food is mostly transported through it by using the cilia that cover its inside surface.

Hemichordata are divided into two classes: the Enteropneusta, commonly called acorn worms, and the Pterobranchia, which may include the graptolites. A third class, Planctosphaeroidea, is proposed based on a single species known only from larvae. The phylum contains about 100 living species. The exact taxonomic position of hemichordata and whether the group is monophyletic is currently under debate. One of the suggestions is that the pterobranchs are more basal deuterostomes, while the enteropneusts are an early offshoot of the lineage who are leading to Chordata.

References

  • [https://www.webdepot.umontreal.ca/Usagers/cameroc/MonDepotPublic/Cameron/Species.html Cameron, C. B. Classification of the extant hemichordata]
  • At the Tree of Life
The Cambrian is a major division of the geologic timescale that begins about 542 ± 1.0 Ma (million years ago) at the end of the Proterozoic eon and ended about 488.3 ± 1.7 Ma with the beginning of the Ordovician period (ICS, 2004).
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The Holocene epoch is a geological period, which began approximately 11,550 calendar years BP (about 9600 BC) and continues to the present. The Holocene is part of the Neogene and Quaternary periods.
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Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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Eumetazoa
Butschli, 1910

subgroups
  • Placozoa
  • Radiata
  • Bilateria


Eumetazoa is a clade comprising all major animal groups except sponges.
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Deuterostomia
Grobben, 1908

Phyla
  • Xenoturbellida (2 species)
  • Vetulicolia † (8 species)
  • Echinodermata (20,000 species)
  • Hemichordata (71 species)
  • Chordata (63,000+ species)


Deuterostomes (taxonomic term:
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William Bateson (August 8, 1861 – February 8, 1926) was a British geneticist. He was the first person to use the term genetics to describe the study of heredity and biological inheritance, and the chief populariser of the ideas of Gregor Mendel following their rediscovery in
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Enteropneusta

Families

Harrimaniidae
Protoglossidae
Ptychoderidae
Saxipendiidae
Spengelidae
Torquaratoridae

The Acorn worms or Enteropneusta are a hemichordate class of invertebrates.
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Pterobranchia is a clade of small, worm-shaped animals. They belong to the hemichordata, and live in secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia attached to tentacles.
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phylum (Greek Φῦλον plural: Φῦλα phyla) is a taxon in the rank below kingdom and above class.
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Deuterostomia
Grobben, 1908

Phyla
  • Xenoturbellida (2 species)
  • Vetulicolia † (8 species)
  • Echinodermata (20,000 species)
  • Hemichordata (71 species)
  • Chordata (63,000+ species)


Deuterostomes (taxonomic term:
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Echinodermata
Klein, 1734

Subphyla & Classes
  • Homalozoa Gill & Caster, 1960
Homostelea
Homoiostelea
Stylophora
Ctenocystoidea Robison & Sprinkle, 1969
  • Crinozoa

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The Cambrian is a major division of the geologic timescale that begins about 542 ± 1.0 Ma (million years ago) at the end of the Proterozoic eon and ended about 488.3 ± 1.7 Ma with the beginning of the Ordovician period (ICS, 2004).
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For other uses of the term, see Fossil (disambiguation)


FOSSIL is a standard for allowing serial communication for telecommunications programs under the DOS operating system.
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Graptolithina

Orders
  • Dendroidea
  • Tuboidea
  • Camaroidea
  • Crustoidea
  • Stolonoidea
  • Graptoloidea
  • Dithecoidea


Graptolites
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The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359.2 ± 2.5 Ma (million years ago), to the beginning of the Permian period, about 299.0 ± 0.8 Ma (ICS 2004).
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The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo.
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In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches[1].
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Chordata
Bateson, 1885

Typical Classes

See below

Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates.
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cilium (plural cilia) is an organelle found in eukaryotic cells. Cilia are thin, tail-like projections extending approximately 5–10 micrometers outwards from the cell body.
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Enteropneusta

Families

Harrimaniidae
Protoglossidae
Ptychoderidae
Saxipendiidae
Spengelidae
Torquaratoridae

The Acorn worms or Enteropneusta are a hemichordate class of invertebrates.
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Pterobranchia is a clade of small, worm-shaped animals. They belong to the hemichordata, and live in secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia attached to tentacles.
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In phylogenetics, a group is monophyletic (Greek: "of one race") if it consists of an inferred common ancestor and all its descendants. A taxonomic group that contains organisms but not their common ancestor is called polyphyletic, and a group that contains some but not all
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Chordata
Bateson, 1885

Typical Classes

See below

Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates.
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