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Topic: Plesiomorphies

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	Kids.Net.Au - Encyclopedia > Cladistics
		Cladistic Methods Typically, an analysis begins by collecting information on certain features of all the organisms in question, and then deciding which versions were present in their common ancestor (plesiomorphies) and which have been derived since (apomorphies).
		If a named group is found to include some but not all of the descendants of the ancestor on which the group is based, it is termed paraphyletic.
		Paraphyletic groups are usually created when organisms are groups on the basis of plesiomorphies instead of apomorphies.
	www.kids.net.au /encyclopedia-wiki/cl/Cladistics (1124 words)

	Cladistics - Palaeos (Site not responding. Last check: 2007-10-10)
		And that is the purpose of this primer: to engender in the reader a sense of the sublimity of systematics— the study of evolution in action—and how it in turn, demonstrates the elegance of evolutionary biology.
		A character state that is present in both the outgroups (the nearest relatives of the group, that are not part of the group itself) and in the ancestors is called a plesiomorphy (meaning "close form", also called ancestral state).
		It is not uncommon to informally refer to a collective set of plesiomorphies as a groundplan for the clade(s) they refer to.
	www.palaeos.org /Cladistics (846 words)

	Glossary for Biological Systematics
		Outgroup comparison - The principle of hypothesizing plesiomorphy for a character state found both in the monophyletic group under study and the monophyletic group which is its closest relative (the outgroup).
		Plesiomorphy - a character state already present in the ancestral species of a group under study.
		Symplesiomorphy - A plesiomorphy shared by two or more species or clades; almost all plesiomorphies are symplesiomorphies.
	www.csupomona.edu /~jcclark/classes/bio406/glossary.html (2761 words)

	Concepts of Macroevolution
		Inferences about phylogenetic patterns are made based on homology For example, a phylogenetic tree illustrates branching patterns that can be used to explain the distribution of apomorphies and plesiomorphies among a group of taxa.
		For example, tetrapody (four-legged condition) is an apomorphy of the reptiles, but a plesiomorphy of snakes (who have apomorphically lost their legs).
		In a phylogenetic data matrix, plesiomorphies are represented as "0".
	snapper.bio.umass.edu /ilip/newmeconcepts.html (861 words)

	Evolutionary Relationships of the Gorgonopsia
		I personally consider the gorgonopsians to form a well-supported clade with the therocephalians and cynodonts called the Theridontia (the cynodonts and therocephalians almost certainly form a clade, the Eutheriodontia).
		That the gorgonopsians are closer to the eutheriodonts than the dinocephalians is practically unquestioned, especially since many taxa previously considered to be "primitive gorgonopsians" based solely on plesiomorphies [shared primitive characteristics] are now excluded from the group and instead make up the probably paraphyletic taxon of basalmost (primitive ancestral) therapsids---the "Biarmosuchia".
		Most of the features used to distance gorgonopsians from the eutheriodonts are plesiomorphies that would be found in the ancestors of any of the three eutherapsid (eutherapsida consisting of the three major therapsid groups dinocephs, anomdonts, and theriodonts), and I'm just not convinced.
	www.kheper.net /evolution/therapsida/gorgons_and_dinocephs.html (702 words)

	Note 6 - What Is a Cichlid? The Technical Details (Site not responding. Last check: 2007-10-10)
		Cichlids are often characterized as freshwater perchlike fishes that have only a single nostril on each side, have a divided lateral line, and lack a subocular shelf, among other features.
		Unfortunately, these characteristics do not a cichlid make, because they are plesiomorphies - character states that are primitive with respect to cichlids.
		To be sure you've got a cichlid, and to substantiate cichlids as a monophyletic group, you need to know the synapomorphies, or shared derived characters, of cichlids.
	www.malawicichlids.com /mw17006.htm (207 words)

	Definition: Pleisiomorphy, Synapomorhy
		Such traits define the strictly monophyletic groups, or clades, which are the basis of cladistic classification systems (see cladistics).
		Shared possession of a symplesiomorph character state is not evidence that the taxa in question are related (Dictionary of Earth Sciences, © Oxford University Press 1999).
		A character is an apomorphy at one branch of the tree, but is a plesiomorphy relative to all the branches after that.
	www.peripatus.gen.nz /Biology/defApomorphy.html (669 words)

	[No title]
		The Gnetales are relatives of angiosperms and Bennettitales that underwent drastic floral reduction and aggregation in response to wind-pollination (Doyle and Donoghue, 1986a).
		The number of similarities or synapomorphies (plesiomorphies for the group) involve nonpreservable characters: siphonogamy, tunica-corpus, lignin chemistry, reduced megaspore wall, and granular exine.
		Additional characters that unite the Bennettitales and Gnetales are stalked or sessile ovules, whorled microsporophylls, and a micropylar tube.
	www.lycos.com /info/cladistics.html (554 words)

	[No title] (Site not responding. Last check: 2007-10-10)
		But if we move to a subset within the vertebrates, to the mammals, then the backbone character is referred to as a plesiomorphy, an ancient characteristic that tells us nothing new about our group of interest, the mammals.
		So, synapomorphies and plesiomorphies are relative, that is, whether or not a feature can be considered a synapomorphy depends on the group being studied within the "tree of all life".
		Finally, an autapomorphy is usually defined as a characteristic (or, sometimes, a suite of characters) shared by all the individuals that make up a species; a feature unique to them and only them.
	oxygen.vancouver.wsu.edu /fac/robson/cl/natrs301/cladintr.htm (660 words)

	Definition: Pleisiomorphy, Synapomorphy
		Note that apomorphy and plesiomorphy are relative concepts.
		For example, hair is a mammalian feature (an apomorphy of mammals), but is primitive in squirrels (a plesiomorphy).
		We can use presence of hair as evidence for the existence of Mammalia, but not for the existence of Sciuridae.
	www.palaeos.com /Systematics/Cladistics/defApomorphy.html (567 words)

	[No title]
		They are instead similar to the nuclei seen in animals cells.
		However, cladistic analysis of many different features indicates these are superficial similarities (in other words homoplasies or plesiomorphies).
		Stephanopogon is not related to animals or to ciliates and therefore can not be the living representative of the ancestor to either group.
	www.gwu.edu /~darwin/BiSc151/Animals/Animals.html (950 words)

	The Deflowering of Seed Plants (Site not responding. Last check: 2007-10-10)
		It is doubtful that bona-fide outgroup comparison would recognize any meaningful plesiomorphies for Angiosperms or Gnetales.
		The genera Bowenia and Stangeria are the most fern-like of Cycads, and their omission from this analysis introduces bias against the recognition of seed plant plesiomorphies in Cycads.
		The sister group relationship between seed plants and Ferns is manifest in primitive fern taxa such as Marattiales and Osmundales, and excluded genera such as Marattia, Dannea, Christensenia, Osmunda, and Todea are the best candidates for recognizing seed plant homologies.
	hometown.aol.com /henniglives/myhomepage/index.html (1445 words)

	IngentaConnect Phylogenetic relationships of spatangoid sea urchins (Echinoidea)...
		By contrast, the trees generated from morphological data differ significantly according to taxon sampling density and only those with dense sampling (after a posteriori weighting) are congruent with molecular estimates.
		With limited taxon sampling, secondary reversals in deep-water taxa are interpreted as plesiomorphies, pulling them to a basal position.
		The addition of fossil taxa with their unique character combinations reveals hidden homoplasy and generates a phylogeny that is compatible with molecular estimates.
	www.ingentaconnect.com /content/bsc/zsc/2005/00000034/00000005/art00001 (341 words)

	Living fossil - Wikipedia, the free encyclopedia
		The resemblance between Peripatus and Aysheaia (an early Cambrian animal from the Burgess Shale) is striking (as of now, both are classified in the Tardipolypoda (Tardigrada and Onychophora), were it not that Aysheaia was a marine animal, while Peripatus lives in tropical leaf mould.
		However, it does not make it clear whether the taxon is truly old, or it simply has many plesiomorphies.
		Note that, as mentioned above, the converse may hold for true living fossil taxa; that is, they may possess a great many derived features (autapomorphies), and not be particularly "primitive" in appearance.
	en.wikipedia.org /wiki/Living_fossil (1186 words)

	MUSSEL Project \| Evolution \| Freshwater Mussel Evolution (Site not responding. Last check: 2007-10-10)
		The HAH, given its ancestral position on the phylogeny, was a chimera of primitive bivalve characters and the derived characters diagnostic of its descendents.
		Of course, it is unnecessary (as well as intractable and meaningless) to list all the plesiomorphies of the HAH.
		Nevertheless, it is useful to establish the ancestral condition of the HAH to polarize character change among the ingroup.
	clade.acnatsci.org /mussel/evol/syst/hah.html (674 words)

	Principles of Classification
		Character states shared by all species in a group undoubtedly were inherited from an earlier species from which the new group was derived.
		These "primitive" or ancestral characteristics are plesiomorphies (plural symplesiomorphies).
		Note - the synapomorphies at an early node become plesiomorphies for successively more recent nodes.
	www-personal.umich.edu /~pwebb/NRE422-BIO440/lec03.html (653 words)

	Primer
		The fundamental idea of cladistics is that features shared by organisms because they share common ancestors (plesiomorphies and apomorphies), rather than features shared by organisms because of convergence or coincidence (homoplasies), should be used to construct family trees.
		All these characters (and many more) are shared by the shark and the mosark because both organisms evolved from a common ancestor; the characters are plesiomorphies ("near-forms").
		The boa, as a vertebrate, will share many plesiomorphies with both the shark and the mosark.
	www.bowdoin.edu /~dbensen/Spec/Primer.html (2667 words)

	Untitled Document
		Natural classifications can be used to predict proprties that are not related to the properties used to create the classification.
		This is because closely related organisms often share ancestral properties (ancestral properties are called "plesiomorphies")
		They are broadly useful because of this predictive value; a classification need not have been designed for a specific purpose to be useful for it.
	www.life.umd.edu /labs/delwiche/bsci348s/lec/DomainsLife.htm (421 words)

	Plesiomorphy - EvoWiki (Site not responding. Last check: 2007-10-10)
		A plesiomorphy is a homologous character within a particular group of organisms, but not unique to members of that group; a basal trait.
		In cladistics, plesiomorphies carry no phylogenetic signal, i.e., cannot be used for classification.
		You can help the EvoWiki by expanding it into a full article.
	wiki.cotch.net /index.php?title=Plesiomorphies&redirect=no (69 words)

	BSC 214 (Site not responding. Last check: 2007-10-10)
		Phylogenies are determined by the use of derived characters (=apomorphies)
		derived characters are different from the character state as it was in the ancestor (called the primitive state (=plesiomorphies).
		In cladistics, organisms are grouped together on the basis of shared derived characters.
	webpages.marshall.edu /~hurlburt/phylolec.html (1108 words)

	Identification of Chaetognaths as Protostomes Is Supported by the Analysis of Their Mitochondrial Genome -- Papillon et ...
		plesiomorphy, the nad3-nad2 block, is conserved in several taxa,
		plesiomorphies, the affinities of arrow worms within protostomes
		exhibit such plesiomorphies: a complete gut with a mouth not
	mbe.oxfordjournals.org /cgi/content/full/21/11/2122 (3825 words)

	Dinosauria Defined
		There are no taxa closer to Triceratops than to Saurischia, once you realize that Triceratops descended from/is nested within Saurischia/Dinosauria.
		Other people may have different opinions, of course; but I've examined all the characters I can find that supposedly unite and distinguish Saurischia from Ornithischia, and they're all questionable: either plesiomorphies, or apomorphies shared with some prosauropod taxa, or just plain ill-defined.
		At the 1994 meeting of the SVP, while talking to Kevin Padian, I mentioned the fact that I regreted the above authors not using Megalosaurus and Iguanodon instead of birds and Triceratops.
	www.dinosauria.com /jdp/dino/dinosaur.htm (784 words)

	CiteULike: The phylogenetic position of the enigmatic wasp family Heterogynaidae based on molecular data, with ... (Site not responding. Last check: 2007-10-10)
		Remarkably, Heterogynaidae is well nested within the Crabronidae + Anthophila clade, which is in conflict with the morphological data.
		This result implies that Heterogynaidae may not have originated from a basal node within Apoidea, as previously considered, and that the character states presumed to be plesiomorphies may instead be homoplasies.
		Our analysis confirms the value of LW opsin in resolving deeper nodes within Apoidea.
	www.citeulike.org /article/586672 (532 words)

	Re: THERIZINOSAURS, SYNAPOMORPHIES, AND PLESIOMORPHIES
		Doesn't change the import of what I say, merely the disposition of the sauropodomorphs.
		<< GO:All the characters that are listed by, say, Benton in _The Dinosauria_ that supposedly unite Theropoda and Sauropodomorpha into a clade Saurischia are either plesiomorphies, homoplasies, or doubtful.
		JW: See Gauthier 1986 To paraphrase nearly every current systematicist, the only way one can determine that a character state is plesiomorphic or homoplastic is by phylogenetic analysis.
	dml.cmnh.org /1997Sep/msg00146.html (1268 words)

	$03siphl (Site not responding. Last check: 2007-10-10)
		Probably a paraphyletic taxon uniting all Tridentiseta except for
		Tetramerotarsata and Ametropus, and characterized by plesiomorphies only.
		(see Plesiomorphies of Siphlonurus/fg1); maxilla with 3 canines and 3
	www.famu.edu /acad/research/mayfly/kluge/03siphl.html (1748 words)

	Amazon.com: "unique apomorphy": Key Phrase page (Site not responding. Last check: 2007-10-10)
		See all pages with references to unique apomorphy.
		subgenus is largely characterized by plesiomorphies relative to Capicola, but the presence of spineiike hairs in the scopa is a unique apomorphy.
		The form of S7 of the male may also be an apomorphy, although, if so, it is a reversion toward...
	www.amazon.com /phrase/unique-apomorphy (518 words)

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