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Topic: Extant taxon

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RedNova News - Science - The Evolution of Long Bone Microstructure and Lifestyle in Lissamphibians An important limitation of our study, and of any conceivable study using extant tetrapods to assess the lifestyle of early stegocephalians, is that the taxa for which we have inferred the lifestyle are not part of the clade of extant taxa (Lissamphibia and Caudata) that form the basis for that inference (Fig. The sampling of extant taxa cannot be expanded further out because the Dipnoi, the closest extant relatives of Tetrapoda, do not possess limbs; even though a femur (and humerus) is present, it is entirely cartilaginous, like most of the endoskeleton (Carroll 1988). This is best done by studying extant tetrapods because we know their lifestyle; in the case of extinct vertebrates, we can only infer it with a variable degree of uncertainty. www.rednova.com /news/display?id=101557

Lazarus taxon - Wikipedia, the free encyclopedia Lazarus taxa that reappear in nature after being known only as old enough fossils can be seen as an informal subcategory of the journalist's "living fossils", because a taxon cannot become globally extinct and reappear. In paleontology, a Lazarus taxon (plural taxa) is a taxon that disappears from one or more periods of the fossil record, only to appear again later. The terms "Lazarus effect" or "Lazarus species" have also found some acceptance in neontology— the study of extant organisms, as contrasted with paleontology— as an organism that is rediscovered alive after having been widely considered extinct for years (a recurring IUCN Red List species for example). en.wikipedia.org /wiki/Lazarus_taxa   (450 words)

EVALUATING SHIFTS IN ANGIOSPERM DIVERSIFICATION RATES Here we use species richness estimates of extant angiosperm genera and families and sister taxon relationships from published molecular phylogenies to test (1) how sister pair tests are affected by inaccuracies in phylogenetic relationships and composition and (2) how well distributions of species among higher taxa match model predictions. The distribution of pair asymmetries (i.e., ratio of the smaller taxon to its larger sister taxon) is a hollow curve, skewed toward 1.0. By definition, monophyletic sister taxa share a common time of origin; greater species richness in one taxon relative to its sister may be interpreted as the result of higher origination rates or lower extinction rates (or both). gsa.confex.com /gsa/2001AM/finalprogram/abstract_27950.htm   (450 words)

..::treeBASE::.. When morphology was analyzed alone, Gavialis was the sister taxon of all other extant crocodylians whether or not fossil ingroup taxa were included, and a sister-group relationship between Gavialis and Tomistoma was significantly less parsimonious. In combination with published sequence and restriction site fragment data, Gavialis was the sister taxon of all other living crocodylians, but the position of Tomistoma depended on the inclusion of fossil ingroup taxa; with or without fossils, preferred morphological and molecular topologies were not significantly different. Fossils closer to Gavialis than to Tomistoma can be recognized in the Late Cretaceous, and fossil relatives of Tomistoma are known from the basal Eocene, strongly indicating a divergence long before the Late Tertiary. www.phylo.org /treebase/view/view_study.php?studyID=S329   (450 words)

Lazarus taxon - Enpsychlopedia In paleontology, a Lazarus taxon (plural taxa) is a taxon that disappears from one or more periods of the fossil record, only to appear again later. The terms "Lazarus effect" or "Lazarus species" have also found some acceptance in neontology — the study of extant organisms, as contrasted with paleontology — as an organism that is rediscovered alive after having been widely considered extinct for years (a reoccurring IUCN Red List species for example). The fossil record is inherently imperfect and contains gaps not necessarily caused by extinction, particularly when the number of individuals in a taxon becomes very low. www.grohol.com /psypsych/Lazarus_taxon   (450 words)

Auk, The: Phylogeny of early tertiary swifts and hummingbirds (Aves: Apodiformes) Monophyly of the taxon (Jungornis + Trochilidae) is supported by unique derived characters, and the osteology of Jungornis provides a transition between the highly derived morphology of extant Trochilidae and that of a more generalized apodiform bird (Figs. Sister group relationship between Argornis and the taxon (Jungornis + extant Trochilidae) is in concordance with the temporal occurrence of the fossil genera, with the Upper Eocene Argornis being geologically older than the Lower Oligocene Jungornis. The "Jungornithidae" sensu Karhu (1999) are shown to be paraphyletic with the Upper Eocene Argornis being the sister taxon of the taxon (Jungornis + extant Trochilidae). www.findarticles.com /p/articles/mi_qa3793/is_200301/ai_n9214314   (1141 words)

Auk, The: Phylogeny of early tertiary swifts and hummingbirds (Aves: Apodiformes) The "Jungornithidae" sensu Karhu (1999) are shown to be paraphyletic with the Upper Eocene Argornis being the sister taxon of the taxon (Jungornis + extant Trochilidae). Monophyly of a clade including extant Hemiprocnidae, the fossil Scaniacypselus, and extant Apodidae is in concordance with previous phylogenetic hypotheses. A few isolated bones from the Upper Eocene to Lower Oligocene deposits of the Quercy were assigned to Cypselavus gallicus Gaillard 1908 (Mourer-Chauvire 1978) which is currently recognized as the earliest taxon of the Hemiprocnidae (Harrison 1984, Peters 1985, Mourer-Chauvire 1988). www.findarticles.com /p/articles/mi_qa3793/is_200301/ai_n9214314   (1141 words)

Auk, The: Phylogeny of early tertiary swifts and hummingbirds (Aves: Apodiformes) The "Jungornithidae" sensu Karhu (1999) are shown to be paraphyletic with the Upper Eocene Argornis being the sister taxon of the taxon (Jungornis + extant Trochilidae). However, Karhu (1988) described a new apodiform taxon, Jungornis tesselatus, from the Lower Oligocene of the Northern Caucasus which agrees with extant Trochilidae in highly characteristic derived features of the humerus (Karhu 1988, 1992). Monophyly of extant Trochilidae to the exclusion of Jungornis is supported by numerous derived features including a peculiar morphology of the coracoid in which the processus procoracoideus is connected to the processus acrocoracoideus by an osseous bridge (Fig. www.findarticles.com /p/articles/mi_qa3793/is_200301/ai_n9214314   (1141 words)

The Prometheus Taxonomic Model: a practical approach to representing multiple classifications Extant taxonomic databases are not capable of dynamically handling multiple, contradictory classifications, nor do they differentiate completely between nomenclature and classification. Furthermore, the separation of the processes of nomenclature and classification, and implementation of the automatic naming of taxa, allows the model to be used as an experimental tool with which a taxonomist can manipulate taxon concepts without regard to the names of the concepts, therefore avoiding unintentional bias. Each taxon defined by this method is given a working name, and the current botanical name can be obtained at any time by examining the distribution and priority of types included in the circumscription. www.dcs.napier.ac.uk /~prometheus/prometheus_1/publications/ntct.htm   (1141 words)

EVALUATING SHIFTS IN ANGIOSPERM DIVERSIFICATION RATES Here we use species richness estimates of extant angiosperm genera and families and sister taxon relationships from published molecular phylogenies to test (1) how sister pair tests are affected by inaccuracies in phylogenetic relationships and composition and (2) how well distributions of species among higher taxa match model predictions. By definition, monophyletic sister taxa share a common time of origin; greater species richness in one taxon relative to its sister may be interpreted as the result of higher origination rates or lower extinction rates (or both). The distribution of pair asymmetries (i.e., ratio of the smaller taxon to its larger sister taxon) is a hollow curve, skewed toward 1.0. gsa.confex.com /gsa/2001AM/finalprogram/abstract_27950.htm   (459 words)

!Diapsida.nex Archosauromorpha : Extant archosaurs and all extinct saurians that are closer to them than they are to extant lepidosaurs (Gauthier, 1984, 1994). Some of these taxa have been given multiple definitions, and some of these definitions have been applied to more than one taxon, but the definitions of taxa given above appear to have priority (de Queiroz and Gauthier, 1990, 1992, and 1994). Lepidosauromorpha : Extant lepidosaurs and all extinct saurians that are closer to them than they are to extant archosaurs (Gauthier, 1984; Gauthier et al., 1988a). ag.arizona.edu /ENTO/tree/eukaryotes/animals/chordata/!Diapsida.nex   (459 words)

EMPIRICAL ESTIMATES OF MINIMUM VIABLE POPULATION SIZES FOR PRIMATES: TENS TO TENS OF THOUSANDS Assuming extinction on the small islands, the MVP size is somewhere between the population size on the smallest island on which the taxon is extant and that on the largest island on which the taxon no longer exists (population size calculated as density of taxon by area of land available). Results for eight to 10 genera (depending on the taxonomy) on 35 islands indicate MVPs of perhaps a few score for Nycticebus (loris) and Macaca (macaque) to several thousands, or scores of thousands, for Pongo (orang-utan) and Symphalangus (siamang). Only four protected areas in south-east Asia are large enough to conserve the smaller MVPs of the siamang and orang-utan. www.anthro.ucdavis.edu /faculty/harcourt/mvpab.htm   (219 words)

biolrev The crown-clade concept, where commonly used taxon terms apply to extant species and their ancestors, is treated as a part of phylogenetic nomenclature by many, but not all, of its proponents (de Queiroz and Donoghue, 1988; de Queiroz and Gauthier, 1990, 1992, 1994; Rowe and Gauthier, 1992; Wyss and Meng, 1996). In the Linnaean system, taxon names are assigned categorical levels, where the category is a measure of rank, such as species, genus, family, order, class, and so on. In their agonizing over how to strip out all the inconsistencies in achieving that identity, they have progressively abandoned modifiable taxon definitions, Linnaean ranks, and the species binomen (some even abandon the notion of species as entities), and the next logical step is clearly to abandon classification. palaeo.gly.bris.ac.uk /Essays/phylocode/biolrev.html   (219 words)

Auk, The: Phylogeny of early tertiary swifts and hummingbirds (Aves: Apodiformes) Extant Podargidae (Podargus strigoides) and Aegothelidae (Aegotheles cristatus) were used for outgroup comparisons. That species, which is known from a few isolated bones of only a single individual, was classified into a monotypic taxon, Eocypselidae, by Harrison (1984) but included in the Hemiprocnidae by Mourer-Chauvire (1988). Comparisons with extant taxa are based on skeletons in the collection of Forschungsinstitut Senckenberg; concerning extant Apodiformes the following species were studied: Aegothelidae: Aegotheles cristatus; Hemiprocnidae: Hemiprocne comata; Apodidae: Chaetura vauxi, Apus apus, Collocalia vanikorensis, Co. salangana; Trochilidae: Phaethornis pretrei, Glaucis hirsuta, Amazilia versicolor, Archilochus colubris, Calypte anna, Anthracothorax sp., and Chrysolampis mosquitus. www.findarticles.com /p/articles/mi_qa3793/is_200301/ai_n9214314   (1141 words)

EVALUATING SHIFTS IN ANGIOSPERM DIVERSIFICATION RATES Here we use species richness estimates of extant angiosperm genera and families and sister taxon relationships from published molecular phylogenies to test (1) how sister pair tests are affected by inaccuracies in phylogenetic relationships and composition and (2) how well distributions of species among higher taxa match model predictions. The distribution of pair asymmetries (i.e., ratio of the smaller taxon to its larger sister taxon) is a hollow curve, skewed toward 1.0. Simulations indicate that a constant rates model accurately predicts species distributions among angiosperm genera but not among families, paralleling work on some animal clades (e.g., rodents). gsa.confex.com /gsa/2001AM/finalprogram/abstract_27950.htm   (1141 words)

Ensifera.nex Sharov (1968) lists a number of extinct families and represents Ensifera as a paraphyletic taxon (showing the order Phasmatodea and suborder Caelifera as being derived from ancestral ensiferan stock) but places all extant families in one clade. Gorochov (1995a) recognizes two extinct ensiferan infraorders, Elcanidea and Oedischiidea, placing all extant (and some extinct) taxa in the infraorders Tettigoniidea and Gryllidea. The three superfamilies of Beier (1972) Key (1970) and Rentz (1991) (Tettigonioidea, Gryllacridoidea and Tettigonioidea) are shown as separate clades only in the trees of Zeuner (1939) and Ragge (1955). ag.arizona.edu /ENTO/tree/eukaryotes/animals/arthropoda/hexapoda/orthoptera/Ensifera.nex   (1141 words)

Molecular Systematics Morphological data provide some support for a sister group relationship between Glires and the order Macroscelidea (elephant shrews) in the superordinal taxon Anagalida, although this taxon is characterized by only two unique synapomorphies. Morphological systematists vary in their support for Glires (Rodentia+ Lagomorpha), but recent morphological work on extant and extinct taxa favors this grouping based on the acquisition of at least six unique traits. The strong support for Glires likely can be ascribed to improvement in phylogenetic reconstruction brought about by thorough taxonomic sampling. www.bio.umass.edu /biology/adkins/Systematics.html   (1141 words)

Andreas Brösing To address questions of evolutionary transformations within the Brachyura from the mid-Jurassic to the present, as a first step the reconstruction of the phylogenetic relationships of the extant brachyuran taxa is necesarry. Within the Decapoda the taxon Brachyura is the species-richest taxon with up to 10000 species. Dissertation “Die Magenstrukturen der Brachyura (Crustacea, Decapoda), Morphologie und phylogenetische Bedeutung.”- (The foregut structures of the Brachyura, morphology and phylogenetic significance.) within the Graduate Colleg “Evolutionary Transformations and Mass Extinction” at the Humboldt University Berlin. www.biologie.hu-berlin.de /~zoologie/andreasb.html   (850 words)

SPECIES ACCOUNTS The definition of species used is the most liberal and relies on the species definition used by experts in the study of each taxonomic group of organisms. Among the over 1 million described extant species the detailed relationships in evolution are seldom fully known. The most conservative opinion accepted by most experts in a given taxon is used. www.speciesaccounts.org   (888 words)

3 PLANTS FROM THE WAIANAE MTNS., OAHU, HAWAII, U.S. Fish & Wildlife Service This taxon is known to be extant in Kaluaa Gulch, but may also still exist in Ekahanui and North Palawai Gulches. With its major infestations in the Waianae Mountains, it is also a probable threat to the only known extant population of Gouania vitifolia (HHP 1992c5). The Waianae Mountains are in the rain shadow of the parallel Koolau Mountains. www.fws.gov /endangered/r/fr94541.html   (5026 words)

Journal of Paleontology: DEVELOPING A PROTOCOL FOR THE CONVERSION OF RANK-BASED TAXON NAMES TO PHYLOGENETICALLY DEFINED CLADE NAMES, AS EXEMPLIFIED BY TURTLES A second problem is that there is no widely accepted protocol for associating a particular node-, stem-, or apomorphy-based clade with one among a realm of possible candidate names from the traditional taxonomic literature (e.g., Sereno, 1998, 1999). Among extant vertebrates, turtles are an ideal clade to lead the transition from a rank-based nomenclatural system (ICZN, 1999) to a rank-free nomenclatural system that is based on phylogenetically defined clade names (PhyloCode, 2003). We consequently focus our efforts toward converting the names associated with the most widely studied, uncontroversial, long-recognized phylogcnetic units, which include extant species, and intentionally leave the conversion of currently ill-supported eladcs, or clades that contain fossils only, to subsequent reviewers. www.findarticles.com /p/articles/mi_qa3790/is_200409/ai_n9448252   (1102 words)

Digimorph - Zaglossus bruijni (long-nosed echidna) Observations on the skulls of fossil and extant echidnas (Monotremata: Tachyglossidae). Zaglossus bruijni, the long-nosed echidna, is one of the three extant members of Monotremata; the others being Tachyglossus aculeatus and Ornithorhynchus anatinus. An alternative hypothesis based on some molecular and morphological data places Monotremata as the sister taxon to Marsupialia (Gregory, 1947; Penny and Hasegawa, 1997). digimorph.org /specimens/Zaglossus_bruijni   (1102 words)

..::treeBASE::.. When morphology was analyzed alone, Gavialis was the sister taxon of all other extant crocodylians whether or not fossil ingroup taxa were included, and a sister-group relationship between Gavialis and Tomistoma was significantly less parsimonious. In combination with published sequence and restriction site fragment data, Gavialis was the sister taxon of all other living crocodylians, but the position of Tomistoma depended on the inclusion of fossil ingroup taxa; with or without fossils, preferred morphological and molecular topologies were not significantly different. Fossils closer to Gavialis than to Tomistoma can be recognized in the Late Cretaceous, and fossil relatives of Tomistoma are known from the basal Eocene, strongly indicating a divergence long before the Late Tertiary. www.phylo.org /treebase/view/view_study.php?studyID=S329   (1102 words)

JVP Content If the new taxon is correctly attributed to the Cordylidae, it constitutes a significant temporal and geographic range extension for the clade since cordylids have no definite representatives in the fossil record and extant forms are restricted to the sub-Saharan portion of mainland Africa. This new record also indicates that cordylids, after their occurrence in the Maastrichtian, became extinct on Madagascar, leaving only zonosaurine Gerrhosauridae as extant representatives of Cordyliformes on the island. We report here the first unequivocal record of a pre-Late Pleistocene lizard from the island of Madagascar, based on a nearly complete lower jaw, elements of both the pectoral and pelvic girdles, several vertebrae and ribs, and numerous osteoderms of what is presumed to be a single individual. www.vertpaleo.org /jvp/23-842-856.html   (280 words)

Devonian Times - More about Ferns This monophyletic group and its sister group, the spermatophytes (seed plants and progymnosperms) form the two extant (not-extinct) clades of the euphyllophytes; this latter taxon, along with its sister group, the lycophytes (including lycopsids) form the two major lineages of vascular plants. The most widely accepted previous schemes placed three groups of extant ferns (Marattiales, Ophioglossales and leptosporangiate ferns) within the "true ferns" while two other groups, sphenophytes (horsetails) and Psilotales (whisk ferns) were regarded as more distantly related "fern allies" that may or may not be "true ferns". Whisk ferns (Psilotales) have no roots, greatly reduced leaves and spore producing organs that are borne on short lateral branches; all other ferns produce spores on their leaves. www.devoniantimes.org /who/pages/ferns.html   (1914 words)

Paleobiology: Reassessing hominoid phylogeny: evaluating congruence in the morphological and temporal data Abstract.-The phylogenetic relationships of fossil and extant members of the primate superfamily Hominoidea are reassessed by using both conventional (morphological) cladistic and stratocladistic (incorporating morphological and temporal data) techniques. Thirteen fossil and five extant genera of the primate superfamily Hominoidea constituted the ingroup of this analysis. The morphological data matrix was modified from the character-by-taxon matrix of Begun et al. www.findarticles.com /p/articles/mi_qa4067/is_200410/ai_n9458411   (1187 words)

Taxon Search : View Taxon Details It conflicts with a historical interpretation of Ornithurae as a receptacle for taxa closer to extant birds, Gauthier’s original definition, Martin’s stated intentions, and apomorphies suggested by the etymology of the taxon. Chiappe (1995:350), in contrast, redefined Ornithurae as a less inclusive, node-based taxon: “All birds derived from the common ancestor of Hesperornithiformes and Neornithes.” This matches the taxonomic content of Martin’s Ornithurae, which is presumably the raison d’etre for the redefinition. All birds derived from the common ancestor of Hesperornithiformes and Neornithes. www.taxonsearch.org /dev/taxon_edit.php?Action=View&tax_id=233   (366 words)

Cornet & Habib 1992 Pocock and Vasanthy (1988) described a new late Carnian (Late Triassic) pollen taxon from the Chinle Formation of Arizona, USA and compared it with the late Carnian Equisetosporites chinleanus from the same formation, and with the pollen of fossil and extant Tricanthereae of the Acanthaceae (also Vasanthy et al., 1990). A, closely resembling the pollen of extant Bravaisia and Sanchezia (Acanthaceae) in size and sculpture is described and compared to a similar morphotype (Cornetipollis) from the late Triassic Richmond basin of Virginia. Magnetostratigraphy and paleomagnetoc poles from Late Triassic-earliest Jurassic strata of the Newark basin. bcornet.tripod.com /Cornet92/CH92a.htm   (7317 words)

RedNova News - Science - Miocene Songbirds and the Composition of the European Passeriform Avifauna Those studies have shown that New Zealand wrens (Acanthisittidae) are the sister group of all other extant passerines (the Eupasseres, which are further divided into suboscines and oscines; Fig. The hypotarsus of the Acanthisittidae, sister taxon of the Eupasseres, bears only two ossified canals for the deef flexor tendons of the toes (fhl and fdl in Fig. Judging from current phylogenies, the presence of plantarly open canals for the superficial tendons fp3-4 and fpp3 in a few extant Eupasseres is most likely a reversal to the primitive condition in those unrelated taxa nested deeply within crown-group Eupasseres (e.g. www.rednova.com /news/display?id=102755   (7317 words)

ScienceWeek The two kinds of bacteria, in the vast majority of their characteristics, are exceedingly similar to each other and fundamentally so different from the eukaryotes that they have to be ranked as a single *taxon, the prokaryotes, different from the only other taxon of this rank, the eukaryotes. Eventually, these bacteria relinquished their ability to live on their own and transferred some of their genes to the nucleus of the host cell, and these bacteria then evolved into the extant mitochondria. In purple bacteria, the size of this unit varies with the light intensity at which the bacteria are grown. www.scienceweek.com /2000/sw000728.htm   (7317 words)

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