Difference between revisions of "Invertebrate" - New World Encyclopedia

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Invertebrate is a term used to describe any animal without a backbone or spinal column. The group includes about 97% of all animal species; that is, all animals except vertebrates, (subphylum Vertebrata of the phylum Chordata), which have a backbone or spinal column. Invertebrates include simple organisms, such as sponges and flatworms, and more complex animals, such as arthropods and molluscs. Vertebrates include the familiar fish, reptiles, amphibians, birds, and mammals. Since invertebrates include all animals except a certain group, invertebrates form a paraphyletic group.

Phyla of invertebrates

The term invertebrate was coined by Jean-Baptiste Lamarck, who divided these animals into two groups, the Insecta and the Vermes. Today, invertebrates are classified into about 30 phyla.

All phyla of animals are invertebrates with the exception that only two of the three subphyla in Phylum Chordata are invertebrates: Urochordata and Cephalochordata. These two, plus all the other known invertebrates, have only one cluster of Hox genes, while the vertebrates have duplicated their original cluster more than once. The largest subphyla in Chordata is Vertebrata.

The exact number of phyla of invertebrates varies according to the taxonomic scheme. For example, some taxonomists recognize a phylum Endoprocta (or Ectoprocta) that exists independently of phylum Bryozoa, but others place both in the single phylum Bryozoa (Colancecco et al. 2001). Some taxonomic schemes recognize Phylum Echiura (spoon worms) and Phylum Pogonophora (beard worms), while other taxonomists assign these the rank of class, with Class Echiura and class Pogoonophora part of the Plylum Annelida. The following is a broad listing of invertebrate phyla:

Phylum Placozoa (Placozoa)
Phylum Porifera (sponges)
Phylum Cnidaria (coral, jellyfish, anemones)
Phylum Ctenophora (comb jellies)
Phylum Platyhelminthes (flatworms)
Phylum Gnathostomulida (jaw worms)
Phylum Mesozoa (mesozoa)
Phylum Nemertina (or Phylum Rhynchocoela) (proboscis worms)
Phylum Gastrotricha (gastrotrichs)
Phylum Rotifera (rotifers)
Phylum Nematoda (roundworms)
Phylum Nematomorpha (horsehair worms)
Phylum Kinorhyncha (mud dragons, spiny-crown worms)
Phylum Acanthocephala (acanthocephalans, spiny-headed worms)
Phylum Loricifera (brush heads)
Phylum Cycliophora (pandora, cycliophorans)
Phylum Entoprocta (goblet worms or marine mats)
Phylum Bryozoa or Phylum Ectoprocta (or Endoprocta) (moss animals or bryozoans)
Phylum Phoronida (horseshoe worms)
Phylum Brachiopoda (brachipods, lampshells)
Phylum Mollusca (molluscs: slugs, snails, squid)
Phylum Priapulida (priapulid worms)
Phylum Sipuncula (peanut worms)
Phylum Annelida (segmented worms: earthworms, ragworms)
Phylum Echiura (or Class Echiura of Annelida) (spoon worms)
Phylum Pogonophora (or class Pogonophora of Annelida) (beard worms)
Phylum Tardigrada (water bears)
Phylum Onychophora (velvet worms)
Phylum Arthropoda (insects, spiders, crabs, etc.)
Phylum Echinodermata (starfish, urchins)
Phylum Chaetognatha (arrow worms)
Phylum Hemichordata (acorn worms)
Phylum Chordata (vertebrates and invertebrates, etc.)
- Subphylum Urochordata
- Subphylum Cephalochordata

Select phyla of invertebrates

The following are descriptions of some well-known invertebrate phyla.

Porifera: sponges

The sponges or poriferans are primitive, sessile, mostly marine, water dwelling filter feeders that pump water through their bodies to filter out particles of food matter. With no true tissues, they lack muscles, nerves, and internal organs. There are over 5,000 modern species of sponges known, and they can be found attached to surfaces anywhere from the intertidal zone to as deep as 8,500 meters (29,000 feet) or further. The fossil record of sponges dates back to the Precambrian era.

Cnidarians: jellyfish, corals, sea anemones

Cnidaria is a phylum containing some 11,000 species of relatively simple animals found exclusively in aquatic, mostly marine, environments. Cnidarians get their name from cnidocytes, which are specialized cells that carry stinging organelles. The corals, which are important reef-builders, belong here, as do the familiar sea anemones and jellyfish. Cnidarians are highly evident in the fossil records, having first appeared in the Precambrian era.

Platyhelminthes: flatworms

The flatworms are relatively simple soft-bodied invertebrates. With about 25,000 known species they are the largest phylum of acoelomates. Flatworms are found in marine, freshwater, and even damp terrestrial environments. Most are free-living forms, but many are parasitic on other animals. They include flukes and tapeworms.

Nematoda: roundworms

The nematodes or roundworms are one of the most common phyla of invertebrates, with over 20,000 different described species, of which over 15,000 are parasitic). They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as Antarctica and oceanic trenches. There are a great many parasitic forms, including pathogens in most plants and animals, humans included.

Annelida: earthworms

The annelids comprise the segmented worms, with about 15,000 modern species, including the well-known earthworms and leeches. They are found in most wet environments, and include many terrestrial, freshwater, and especially marine species (such as the polychaetes), as well as some which are parasitic or mutualistic. They range in length from under a millimeter to over 3 meters (the seep tube worm Lamellibrachia luymesi).

Echinodermata — sea star, sea urchins, sea cucumbers

Echinoderms are a phylum of marine invertebrates found at all depths. This phylum appeared in the early Cambrian period and contains about 7,000 living species and 13,000 extinct ones. They include starfish, sea daisies, crinoids, sea urchins, sand dollars, sea cucumbers, and brittle stars. Echinodermata is the largest animal phylum to lack any freshwater or terrestrial representatives.

Mollusca — squid, snails

The mollusks (American spelling) or molluscs (British spelling) are the large and diverse phylum Mollusca, which includes a variety of familiar animals well-known for their decorative shells or as seafood. These range from tiny snails, clams, and abalone to squid, cuttlefish and the octopus (which is considered the most intelligent invertebrate). There are some 112,000 species within this phylum (Feldkamp 2002). The giant squid, which until recently had not been observed alive in its adult form, is the largest invertebrate; although it is possible that the colossal squid is even larger.

Arthropoda — insects, ticks, spiders, grasshoppers, lobsters, crabs

Arthropods are the largest phylum of animals and include the insects, arachnids, crustaceans, and others. More than 80% of described living animal species are arthropods (Thanukos 2006), with over a million modern species described and a fossil record reaching back to the early Cambrian. Arthropods are common throughout marine, freshwater, terrestrial, and even aerial environments, as well as including various symbiotic and parasitic forms. They range in size from microscopic plankton up to forms several meters long.

Arthropods are characterized by the possession of a segmented body with appendages on each segment. They have a dorsal heart and a ventral nervous system. All arthropods are covered by a hard exoskeleton made of chitin, a polysaccharide, which provides physical protection and resistance to desiccation. Periodically, an arthropod sheds this covering when it moults.

External links

Beatty, J. A., and R. E. Blackwelder. 1974. Names of invertebrate phyla. Systematic Zoology 23(4):545-547.
Colancecco, M., R. Brittingham, M. Wells, and b. MacKeverican. 2001. The Endoprocta controversy: A review. Journal of Systematic Biology at Susquehanna University 8(1).
Feldkamp, S. 2002. Modern Biology. United States:Holt, Rinehart, and Winston.
Maggenti, A. r., and S. Gardner. 2005. Online Dictionary of Invertebrate Zoology. (accessed November 13, 2006).
Thanukos, A. 2006. The Arthropod Story. University of California, Berkeley.

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Invertebrate
Sea_sponge
Cnidaria
Flatworm
Nematode
Annelid
Echinoderm
Mollusca
Arthropod
Bryozoa
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@@ Line 8: / Line 8: @@
 All phyla of animals are invertebrates with the exception that only two of the three subphyla in Phylum Chordata are invertebrates: [[Urochordata]] and [[Cephalochordata]]. These two, plus all the other known invertebrates, have only one cluster of [[Hox genes]], while the vertebrates have duplicated their original cluster more than once. The largest subphyla in Chordata is Vertebrata.
-The exact number of phyla of invertebrates varies according to the taxonomic scheme. For example, some taxonomists recognize a phylum Endoprocta that exists independently of phylum Bryozoa, but others place both in the single phylum Bryozoa (Colancecco et al. 2001). Some taxonomic schemes recognize Phylum Echiura (spoon worms) and Phylum Pogonophora (beard worms), while other taxonomists assign these the rank of class, with Class Echiura and class Pogoonophora part of the Plylum Annelida. The following is a broad listing of invertebrate phyla:
+The exact number of phyla of invertebrates varies according to the taxonomic scheme. For example, some taxonomists recognize a phylum Endoprocta (or Ectoprocta) that exists independently of phylum Bryozoa, but others place both in the single phylum Bryozoa (Colancecco et al. 2001). Some taxonomic schemes recognize Phylum Echiura (spoon worms) and Phylum Pogonophora (beard worms), while other taxonomists assign these the rank of class, with Class Echiura and class Pogoonophora part of the Plylum Annelida. The following is a broad listing of invertebrate phyla:
 *Phylum Placozoa (Placozoa)
@@ Line 26: / Line 26: @@
 *Phylum [[Loricifera]]* (brush heads)
 *Phylum [[Cycliophora]]* (pandora, cycliophorans)
-*Phylum [[Bryozoa]]* or Phylum Ectoprocta (moss animals or bryozoans)
 *Phylum [[Entoprocta]]* (goblet worms or marine mats)
+*Phylum [[Bryozoa]]* or Phylum Ectoprocta (or Endoprocta) (moss animals or bryozoans)
-***[[Echinoderm]]ata (starfish, urchins)
+*Phylum [[Phoronida]]* (horseshoe worms)
-***[[Chaetognatha]] (arrow worms)
+*Phylum [[Brachiopoda]]* (brachipods, lampshells)
-**'''Superphylum [[Ecdysozoa]]''' (shed exoskeleton)
+*Phylum [[Mollusca]] (molluscs: slugs, snails, squid)
+*Phylum [[Priapulida]]* (priapulid worms)
+*Phylum [[Sipuncula]]* (peanut worms)
-***[[Priapulida]] (priapulid worms)
+*Phylum [[Annelida]] (segmented worms: earthworms, ragworms)
+*Phylum Echiura (or Class Echiura of Annelida) (spoon worms)
+*Phylum Pogonophora (or class Pogonophora of Annelida) (beard worms)
-***[[Onychophora]] (velvet worms)
+*Phylum [[Tardigrada]]* (water bears)
-***[[Tardigrada]] (water bears)
+*Phylum [[Onychophora]]* (velvet worms)
-***[[Arthropoda]] (insects, etc.)
+*Phylum [[Arthropoda]] (insects, spiders, crabs, etc.)
-**'''Superphylum [[Platyzoa]]'''
+*Phylum [[Echinoderm]]ata (starfish, urchins)
+*Phylum [[Chaetognatha]]* (arrow worms)
+*Phylum [[Hemichordata]] (acorn worms)
-***[[Micrognathozoa]] (limnognathia)
-**'''Superphylum [[Lophotrochozoa]]''' (trochophore larvae / lophophores)
-***[[Sipuncula]] (peanut worms)
-***[[Nemertea]] (ribbon worms)
-***[[Phoronida]] (horseshoe worms)
-***[[Brachiopoda]] (brachipods)
-***[[Mollusca]] (molluscs)
-***[[Annelida]] (segmented worms)
 *Phylum [[Chordate|Chordata]] (vertebrates and invertebrates, etc.)
 **Subphylum [[Urochordata]]
 **Subphylum [[Cephalochordata]]
-**Phylum [[Hemichordata]] (acorn worms)
-*[[Orthonectida]] (orthonectids)
-*[[Rhombozoa]] (dicyemids)
-*Phylum[[Acoelomorpha]] (basal)
-**[[Myxozoa]] (slime animals)
+==Select phyla of invertebrates==
+The following are descriptions of some well-known invertebrate phyla.
 ===[[Porifera]]: sponges===
-The '''sponges''' or '''poriferans''' are [[animal]]s of the [[phylum]] '''Porifera'''. They are primitive, [[sessile]], mostly [[ocean|marine]], water dwelling [[filter feeder]]s that pump water through their bodies to filter out particles of food matter. With no true tissues ([[parazoa]]), they lack [[muscle]]s, [[nerve]]s, and internal [[organ (anatomy)|organ]]s. There are over 5,000 modern species of sponges known, and they can be found attached to surfaces anywhere from the [[intertidal zone]] to as deep as 8,500 [[metre|m]] (29,000 [[foot (unit of length)|feet]]) or further. The [[fossil]] record of sponges dates back to the [[Precambrian]] era.
+The '''sponges''' or '''poriferans''' are primitive, sessile, mostly [[ocean|marine]], water dwelling filter feeders that pump water through their bodies to filter out particles of food matter. With no true tissues, they lack [[muscle]]s, [[nerve]]s, and internal organs. There are over 5,000 modern species of sponges known, and they can be found attached to surfaces anywhere from the intertidal zone to as deep as 8,500 meters (29,000 feet) or further. The [[fossil]] record of sponges dates back to the [[Precambrian]] era.
 ===[[Cnidarians]]: jellyfish, corals, sea anemones===
-'''Cnidaria''' (silent c - pronounced /{{IPA|naɪˡdeɹiə}}/ from [[New Latin]] ''cnida'', fr. [[Greek language|Gk]] ''κνιδη'' "[[nettle]]", "[[sea anemone]]"<ref>{{cite book |last=Dalby |first=Andrew |title=Food in the Ancient World: from A to Z |origyear=2003 |publisher=Routledge |location=London, New York |language=English |pages=296 |chapter=Sea anemone }}</ref>) is a [[Phylum (biology)|phylum]] containing some 11,000 [[species]] of relatively simple [[animal]]s found exclusively in aquatic, mostly marine, environments. Cnidarians get their name from [[cnidocyte]]s, which are specialized cells that carry stinging [[organelle]]s. The [[coral]]s, which are important [[reef]]-builders, belong here, as do the familiar [[sea anemone]]s, [[jellyfish]], [[sea pen]]s, [[sea pansies]] and [[sea wasp]]s. The names '''[[Coelenterata]]''' and '''Coelentera''' were formerly applied to the group, but as those names included the [[Ctenophore]]s (comb jellies), they have been abandoned. Cnidarians are highly evident in the [[fossil]] records, having first appeared in the [[Precambrian]] era.
+'''Cnidaria''' is a phylum containing some 11,000 [[species]] of relatively simple [[animal]]s found exclusively in aquatic, mostly marine, environments. Cnidarians get their name from cnidocytes, which are specialized cells that carry stinging organelles. The [[coral]]s, which are important [[reef]]-builders, belong here, as do the familiar [[sea anemone]]s and [[jellyfish]]. Cnidarians are highly evident in the [[fossil]] records, having first appeared in the [[Precambrian]] era.
 ===[[Platyhelminthes]]: flatworms===
-The '''flatworms''' ('''Platyhelminthes''', Greek "platy"': flat; "helminth": worm) are a [[Phylum (biology)|phylum]] of relatively simple soft-bodied invertebrate [[animal]]s. With about 25,000 known [[species]] they are the largest phylum of [[body cavity|acoelomates]].  Flatworms are found in marine, freshwater, and even damp terrestrial environments. Most are free-living forms, but many are [[parasitic]] on other animals. There are four [[class (biology)|class]]es: [[Trematoda]] (Flukes), [[Cestoda]] (Tapeworms), [[Monogenea]], and [[Turbellaria]].
+The '''flatworms''' are relatively simple soft-bodied invertebrates. With about 25,000 known [[species]] they are the largest phylum of acoelomates.  Flatworms are found in marine, freshwater, and even damp terrestrial environments. Most are free-living forms, but many are [[parasite|parasitic]] on other animals. They include flukes and tapeworms.
 ===[[Nematoda]]: roundworms===
-The '''nematodes''' or '''roundworms''' ([[phylum (biology)|Phylum]] '''Nematoda''' from Gr. nema, nematos "thread" + ode "like") are one of the most common phyla of [[animal]]s, with over 20,000 different described species (over 15,000 are [[parasite|parasitic]]). They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as [[Antarctica]] and [[oceanic trench|oceanic trenches]]. Further, there are a great many parasitic forms, including [[pathogen]]s in most plants and animals, humans included. Only the [[Arthropod]]a are more diverse.
+The '''nematodes''' or '''roundworms''' are one of the most common phyla of invertebrates, with over 20,000 different described species, of which over 15,000 are [[parasite|parasitic]]). They are ubiquitous in freshwater, marine, and terrestrial environments, where they often outnumber other animals in both individual and species counts, and are found in locations as diverse as [[Antarctica]] and oceanic trenches. There are a great many parasitic forms, including pathogens in most plants and animals, humans included.
 ===[[Annelida]]: earthworms===
-The '''annelids''', collectively called '''Annelida''' (from [[Latin]] ''annellus'' "little ring"), are a large [[Scientific classification|phylum]] of [[animal]]s, comprising the segmented [[worm]]s, with about 15,000 modern species including the well-known [[earthworm]]s and [[leech]]es. They are found in most wet environments, and include many [[Terrestrial animal|terrestrial]], [[fresh water|freshwater]], and especially [[Marine (ocean)|marine]] species (such as the [[polychaete]]s), as well as some which are parasitic or mutualistic. They range in length from under a millimeter to over 3&nbsp;[[metre]]s (the seep tube worm ''[[Lamellibrachia]] luymesi'').
+The '''annelids''' comprise the segmented [[worm]]s, with about 15,000 modern species, including the well-known [[earthworm]]s and [[leech]]es. They are found in most wet environments, and include many terrestrial, freshwater, and especially marine species (such as the polychaetes), as well as some which are parasitic or [[symbiosis|mutualistic]]. They range in length from under a millimeter to over 3 meters (the seep tube worm ''Lamellibrachia luymesi'').
 ===[[Echinodermata]] — sea star, sea urchins, sea cucumbers===
-'''Echinoderms''' (Phylum '''Echinodermata''', from the [[Greek language|Greek]] for ''spiny skin'') are a [[Phylum (biology)|phylum]] of marine [[animal]]s found at all depths. This phylum appeared in the early [[Cambrian]] Period and contains about 7,000 living [[species]] and 13,000 extinct ones. Five or six [[class (biology)|classes]] (six counting Concentricycloidea) are alive today:
+'''Echinoderms''' are a phylum of marine invertebrates found at all depths. This phylum appeared in the early [[Cambrian]] period and contains about 7,000 living [[species]] and 13,000 extinct ones. They include starfish, sea daisies, crinoids, sea urchins, sand dollars, sea cucumbers, and brittle stars. Echinodermata is the largest animal phylum to lack any freshwater or terrestrial representatives.
-* [[Sea star|Asteroidea]] (asteroids, starfish, or sea stars): about 1,500 species that capture prey for their own food.
-* [[Sea daisy|Concentricycloidea]] (sea daisies), notable for their unique water vascular system; two species; recently merged into Asteroidea.
-* [[Crinoidea]] (crinoids, feather stars or sea lilies): about 600 species that are suspension feeders.
-* [[Sea urchin|Echinoidea]] (echinoids, sea urchins and [[sand dollar]]s): notable for their movable spines; about 1,000 species.
-* [[Sea cucumber|Holothuroidea]] (sea cucumbers): elongated animals resembling slugs; about 1,000 species.
-* [[Brittle star|Ophiuroidea]] (brittle stars and basket stars), the physically largest of echinoderms; about 1,500 species.
-Extinct forms known from [[fossil]]s include [[blastoid]]s, [[edrioasteroid]]s, and several early [[Cambrian]] animals such as ''[[Helicoplacus]]'', [[carpoid]]s, [[Homalozoa]], and possibly [[machaerid]]s.
-Echinodermata is the largest animal phylum to lack any [[fresh water|freshwater]] or terrestrial representatives.
 ===[[Mollusc]]a — squid, snails===
-The '''mollusks''' (American spelling) or '''molluscs''' (British spelling) are the large and diverse [[Phylum (biology)|phylum]] '''Mollusca''', which includes a variety of familiar [[animal]]s well-known for their decorative shells or as [[seafood]]. These range from tiny [[snail]]s, [[clam]]s, and [[abalone]] to [[squid]], [[cuttlefish]] and the [[octopus]] (which is considered the most intelligent [[invertebrate]]). There are some 112,000 [[species]] within this phylum.<ref>Feldkamp, Susan (2002). Modern Biology. United States: Holt, Rinehart, and Winston. pp. 725</ref>
+The '''mollusks''' (American spelling) or '''molluscs''' (British spelling) are the large and diverse phylum '''Mollusca''', which includes a variety of familiar animals well-known for their decorative shells or as [[seafood]]. These range from tiny [[snail]]s, [[clam]]s, and abalone to [[squid]], cuttlefish and the [[octopus]] (which is considered the most intelligent invertebrate). There are some 112,000 [[species]] within this phylum (Feldkamp 2002). The giant squid, which until recently had not been observed alive in its adult form, is the largest invertebrate; although it is possible that the colossal squid is even larger.
-The [[giant squid]], which until recently had not been observed alive in its adult form, is the largest invertebrate; although it is possible that the [[colossal squid]] is even larger. The scientific study of mollusks is called '''malacology'''.
 ===[[Arthropod]]a — insects, ticks, spiders, grasshoppers, lobsters, crabs===
-'''Arthropods''' ([[Scientific classification|Phylum]] '''Arthropoda''', from the [[Greek language|Greek]] ἀρθρον, meaning [[joint]] and πούς/ποδός, meaning [[foot]]) are the largest [[phylum]] of [[animal]]s and include the [[insect]]s, [[arachnid]]s, [[crustacean]]s, and others. More than 80% of described living animal species are arthropods&nbsp;<ref>{{cite web |author=Anna Thanukos |url=http://evolution.berkeley.edu/evolibrary/article/arthropodstory |title=The Arthropod Story |publisher=[[University of California, Berkeley]]}}</ref>, with over a million modern species described and a [[fossil record]] reaching back to the early [[Cambrian]]. Arthropods are common throughout marine, freshwater, terrestrial, and even aerial environments, as well as including various [[symbiosis|symbiotic]] and [[parasite|parasitic]] forms. They range in size from microscopic [[plankton]] (~¼&nbsp;[[millimetre|mm]]) up to forms several [[metre]]s long.
+'''Arthropods''' are the largest phylum of [[animal]]s and include the [[insect]]s, [[arachnid]]s, [[crustacean]]s, and others. More than 80% of described living animal species are arthropods (Thanukos 2006), with over a million modern species described and a [[fossil]] record reaching back to the early [[Cambrian]]. Arthropods are common throughout marine, freshwater, terrestrial, and even aerial environments, as well as including various [[symbiosis|symbiotic]] and [[parasite|parasitic]] forms. They range in size from microscopic [[plankton]] up to forms several meters long.
-Arthropods are characterised by the possession of a [[segment]]ed body with [[appendage]]s on each segment. They have a [[Dorsum (biology)|dorsal]] heart and a [[ventral nervous system]]. All arthropods are covered by a hard [[exoskeleton]] made of [[chitin]], a [[polysaccharide]], which provides physical protection and resistance to [[desiccation]]. Periodically, an arthropod sheds this covering when it [[ecdysis|moults]].
+Arthropods are characterized by the possession of a segmented body with appendages on each segment. They have a dorsal heart and a ventral [[nervous system]]. All arthropods are covered by a hard exoskeleton made of chitin, a [[carbohydrate|polysaccharide]], which provides physical protection and resistance to desiccation. Periodically, an arthropod sheds this covering when it [[ecdysis|moults]].
-*[[Bryozoa]] — moss animals, sea mats (occasionally resemble corals)
-'''Bryozoans''' are tiny colonial animals that generally build stony [[skeleton]]s of [[calcium carbonate]], superficially similar to [[coral]]. They are also known as '''moss animals''' or '''sea mats'''. They generally prefer warm, tropical waters but are known to occur worldwide. There are about 5,000 living [[species]], with several times that number of fossil forms known.
+==External links==
+* Beatty, J. A., and R. E. Blackwelder. 1974. Names of invertebrate phyla. ''Systematic Zoology'' 23(4):545-547.
+* Colancecco, M., R. Brittingham, M. Wells, and b. MacKeverican. 2001. The Endoprocta controversy: A review. ''Journal of Systematic Biology at Susquehanna University'' 8(1).
+* Feldkamp, S. 2002. ''Modern Biology''. United States:Holt, Rinehart, and Winston.
+* Maggenti, A. r., and S. Gardner. 2005. [http://digitalcommons.unl.edu/onlinedictinvertzoology Online Dictionary of Invertebrate Zoology]. (accessed November 13, 2006).
+* Thanukos, A. 2006. [http://evolution.berkeley.edu/evolibrary/article/arthropodstory ''The Arthropod Story'']. University of California, Berkeley.
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-==External links==
-*{{cite book |author=A. R. Maggenti & S. Gardner |url=http://digitalcommons.unl.edu/onlinedictinvertzoology/ |title=Online Dictionary of Invertebrate Zoology |year=2005}}
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 [[Category:Life sciences]]