65-409: Aneuraceae Metzgeriaceae † Metzgeriites Anacrogynae (various authors) Frondosae Endlicher , 1841 Metzgeriales is an order of liverworts . The group is sometimes called the simple thalloid liverworts : " thalloid " because the members lack structures resembling stems or leaves, and "simple" because their tissues are thin and relatively undifferentiated . All species in
130-499: A BioCode that would regulate all taxon names, but this attempt has so far failed because of firmly entrenched traditions in each community. Consider a particular species, the red fox , Vulpes vulpes : in the context of the Zoological Code , the specific epithet vulpes (small v ) identifies a particular species in the genus Vulpes (capital V ) which comprises all the "true" foxes. Their close relatives are all in
195-493: A thallus that is very deeply lobed, thus giving the appearance of leafiness. The genus Phyllothallia has a more striking leafiness, with paired lobes of tissue spaced regularly at swollen nodes along a central, forked stem. The several semileafy groups within the Metzgeriales are not closely related to each other, and the currently accepted view is that the leafy condition evolved separately and independently in each of
260-420: A "hybrid formula" that specifies the parentage, or may be given a name. For hybrids receiving a hybrid name , the same ranks apply, prefixed with notho (Greek: 'bastard'), with nothogenus as the highest permitted rank. If a different term for the rank was used in an old publication, but the intention is clear, botanical nomenclature specifies certain substitutions: Classifications of five species follow:
325-567: A fast evolutionary radiation that occurred long ago, such as the main taxa of placental mammals . In his landmark publications, such as the Systema Naturae , Carl Linnaeus used a ranking scale limited to kingdom, class, order, genus, species, and one rank below species. Today, the nomenclature is regulated by the nomenclature codes . There are seven main taxonomic ranks: kingdom, phylum or division, class, order, family, genus, and species. In addition, domain (proposed by Carl Woese )
390-638: A lower level may be denoted by adding the prefix " infra ", meaning lower , to the rank. For example, infra order (below suborder) or infra family (below subfamily). Botanical ranks categorize organisms based (often) on their relationships ( monophyly is not required by that clade, which does not even mention this word, nor that of " clade "). They start with Kingdom, then move to Division (or Phylum), Class, Order, Family, Genus, and Species. Taxa at each rank generally possess shared characteristics and evolutionary history. Understanding these ranks aids in taxonomy and studying biodiversity. There are definitions of
455-429: A midrib and thin lamina, but unlike that taxon the lamina of M. infracretaceus is not lobed. Aneuraceae Riccardiaceae Aneuraceae (sometimes Riccardiaceae ) is a family of thallose liverworts in the order Metzgeriales . Most species are very small with narrow, branching thalli. Aneuraceae is the largest family in the order Metzgeriales, simple thalloid liverworts. The number of species listed
520-399: A new rank at will, at any time, if they feel this is necessary. In doing so, there are some restrictions, which will vary with the nomenclature code that applies. The following is an artificial synthesis, solely for purposes of demonstration of absolute rank (but see notes), from most general to most specific: Ranks are assigned based on subjective dissimilarity, and do not fully reflect
585-459: A particular organism, it is usually not necessary to specify names at ranks other than these first two, within a set of taxa covered by a given rank-based code. However, this is not true globally because most rank-based codes are independent from each other, so there are many inter-code homonyms (the same name used for different organisms, often for an animal and for a taxon covered by the botanical code). For this reason, attempts were made at creating
650-401: A portion of a 2006 cladistic analysis of liverworts based upon three chloroplast genes, one nuclear gene, and one mitochondrial gene. The genus Sandeothallus and the species Mizutania riccardioides and Vandiemenia ratkowskiana (each the only member of its respective family) were not included in the study. Linked names at the tips of clade branches are families currently assigned to
715-451: A separate order. Although these plants are almost entirely restricted to regions with high humidity or readily available moisture, the group as a whole is widely distributed, and occurs on every continent except Antarctica. One simple thalloid liverwort is not photosynthetic . The species Cryptothallus mirabilis is white as a result of lacking chlorophyll , and has plastids that do not differentiate into chloroplasts . This species
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#1732790735980780-634: A single class Cryptogamia . Linnaeus' system was heavily revised by workers in the early nineteenth century, so that by the time Endlicher published his Enchiridion Botanicum in 1841, five orders of liverworts were defined, and the "Frondosae" were segregated as a group that is congruent with the modern concept of the Metzgeriales. Endlicher's "Frondosae" included five subgroups (Metzgerieae, Aneureae, Haplolaeneae, Diplomitrieae, and Codonieae) with no assigned taxonomic rank , but these groups were termed Familien by Dědeček in 1886. The same five subgroups of "Frondosae", without significant change, were used in
845-576: A taxon in a category above the species level). It should be a natural group (that is, non-artificial, non- polyphyletic ), as judged by a biologist, using all the information available to them. Equally ranked higher taxa in different phyla are not necessarily equivalent in terms of time of origin, phenotypic distinctiveness or number of lower-ranking included taxa (e.g., it is incorrect to assume that families of insects are in some way evolutionarily comparable to families of mollusks). Of all criteria that have been advocated to rank taxa, age of origin has been
910-532: A thin, ribbon-like, bifurcating thallus with a thicker central midrib. The plant is remarkably similar in structure to members of the extant liverwort family Pallaviciniaceae , but no reproductive structures have been found. Additional species assigned to the genus Pallavicinites have been found in rocks dating from the Carboniferous to the Pleistocene . Another early fossil probably belonging to
975-493: Is a myco-heterotroph that obtains its nutrients from fungi growing among its tissues. These plants grow in bogs and are typically found under peat moss near birch trees. The beginning of modern liverwort nomenclature is marked with the 1753 publication of Linnaeus' Species Plantarum , although this relied heavily upon the prior work of Micheli (1729) and Dillenius (1741). Linnaeus included all 25 known species of liverworts, together with mosses, algae, and fungi, within
1040-564: Is also called a binomial , that is, a two-term name. For example, the zoological name for the human species is Homo sapiens . This is usually italicized in print or underlined when italics are not available. In this case, Homo is the generic name and it is capitalized; sapiens indicates the species and it is not capitalized. While not always used, some species include a subspecific epithet. For instance, modern humans are Homo sapiens sapiens , or H. sapiens sapiens . In zoological nomenclature, higher taxon names are normally not italicized, but
1105-410: Is considered to be inflated because of a high level of synonymy , and might be reduced from about 300 to about 100 if the family were revised. Species are difficult to delimit because nearly all are morphologically highly variable. Genetic studies suggest that some, such as Aneura pinguis , include morphologically cryptic species. A molecular phylogenetic study in 2010 produced a cladogram showing
1170-639: Is more closely related to the Marchantiales than to members of the Metzgeriales. Likewise, the Treubiaceae is now in its own order Treubiales , within the recently recognized class Haplomitriopsida . A 2016 analysis of liverwort classification has further reduced the Metzgeriales to include only two families, Metzgeriaceae and Aneuraceae , with all other previously included families dispersed into three additional orders: Fossombroniales , Pallaviciniales , and Pelliales . Families reassigned in
1235-467: Is not a requirement of the zoological and botanical codes. A classification in which all taxa have formal ranks cannot adequately reflect knowledge about phylogeny. Since taxon names are dependent on ranks in rank-based (Linnaean) nomenclature, taxa without ranks cannot be given names. Alternative approaches, such as phylogenetic nomenclature , as implemented under the PhyloCode and supported by
1300-435: Is now widely used as a fundamental rank, although it is not mentioned in any of the nomenclature codes, and is a synonym for dominion ( Latin : dominium ), introduced by Moore in 1974. A taxon is usually assigned a rank when it is given its formal name. The basic ranks are species and genus. When an organism is given a species name it is assigned to a genus, and the genus name is part of the species name. The species name
1365-406: Is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of organisms (a taxon ) in a hierarchy that reflects evolutionary relationships. Thus, the most inclusive clades (such as Eukarya and Opisthokonta ) have the highest ranks, whereas the least inclusive ones (such as Homo sapiens or Bufo bufo ) have
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#17327907359801430-789: The Botanical Code , the Prokaryotic Code , the Code for Viruses , the draft BioCode and the PhyloCode all recommend italicizing all taxon names (of all ranks). There are rules applying to the following taxonomic ranks in the International Code of Zoological Nomenclature : superfamily, family, subfamily, tribe, subtribe, genus, subgenus, species, subspecies. The International Code of Zoological Nomenclature divides names into "family-group names", "genus-group names" and "species-group names". The Code explicitly mentions
1495-483: The International Society for Phylogenetic Nomenclature , or using circumscriptional names , avoid this problem. The theoretical difficulty with superimposing taxonomic ranks over evolutionary trees is manifested as the boundary paradox which may be illustrated by Darwinian evolutionary models. There are no rules for how many species should make a genus, a family, or any other higher taxon (that is,
1560-508: The Karagandy Province of Kazakhstan . Mesozoic fossils of Metzgeriites have also been found. Metzgeriites glebosus has been collected from Jurassic strata of Greenland . The type material, and so far only material collected, consists of a midrib with a thin lamina that is deeply and irregularly lobed. A Cretaceous fossil from Portugal has been named Metzgeriites infracretaceus . Like M. glebosus , it possesses
1625-727: The Prokaryotic Code , and the Code for Viruses ) require them. However, absolute ranks are not required in all nomenclatural systems for taxonomists; for instance, the PhyloCode , the code of phylogenetic nomenclature , does not require absolute ranks. Taxa are hierarchical groups of organisms, and their ranks describes their position in this hierarchy. High-ranking taxa (e.g. those considered to be domains or kingdoms, for instance) include more sub-taxa than low-ranking taxa (e.g. those considered genera, species or subspecies). The rank of these taxa reflects inheritance of traits or molecular features from common ancestors. The name of any species and genus are basic ; which means that to identify
1690-508: The Synopsis Hepaticarum of Gottsche, Lindenberg, and Nees. A more thorough understanding of the Metzgeriales was not achieved until the morphological and developmental work of Leitgeb in the late nineteenth century. Leitgeb was among the first to recognize and appreciate the significance of development and reproductive morphology as a guide to distinguishing liverwort groups. His careful examinations guided revisions made in
1755-427: The fruit fly familiar in genetics laboratories ( Drosophila melanogaster ), humans ( Homo sapiens ), the peas used by Gregor Mendel in his discovery of genetics ( Pisum sativum ), the "fly agaric" mushroom Amanita muscaria , and the bacterium Escherichia coli . The eight major ranks are given in bold; a selection of minor ranks are given as well. Taxa above the genus level are often given names based on
1820-418: The type genus , with a standard termination. The terminations used in forming these names depend on the kingdom (and sometimes the phylum and class) as set out in the table below. Pronunciations given are the most Anglicized . More Latinate pronunciations are also common, particularly / ɑː / rather than / eɪ / for stressed a . There is an indeterminate number of ranks, as a taxonomist may invent
1885-473: The 2016 analysis: In previous decades, there has been considerable confusion over the correct attribution of the name "Metzgeriales". The ordinal name Metzgeriales was first published by Chalaud in 1930 with the description “J’ai désigné très généralement les Jungermannniales anacrogynes sous le nom de Metzgériales,” (that is: "I have designated very generally the Jungermannniales anacrogynes under
1950-633: The American Ornithologists' Union published in 1886 states "No one appears to have suspected, in 1842 [when the Strickland code was drafted], that the Linnaean system was not the permanent heritage of science, or that in a few years a theory of evolution was to sap its very foundations, by radically changing men's conceptions of those things to which names were to be furnished." Such ranks are used simply because they are required by
2015-482: The Metgeriales lack hard tissues, and the plants often decay or die back, preservation of fossils is dependent upon rapid burial by floods or volcanic ash . Bryophytes are considered "delicate" plants, and this characteristic is often cited as the reason for the apparently poor fossil record of the group. However, fossils of the Metzgeriales are distributed widely, both geographically and stratigraphically, and
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2080-478: The Metzgeriales is the Carboniferous fossil Thallites willsi , which has been compared to the modern genus Metzgeria . However, it has been assigned to the form genus Thallites , which is used for thalloid fossil plants and algae of uncertain relationships. Most fossils belonging to the Metzgeriales are assigned to the genus Metzgeriites , which was established for this purpose. Specimens from
2145-432: The Metzgeriales itself as a superorder "Metzgerianae", but Schuster's 1984 system rejected most of these changes. The classification of Crandall-Stotler and Stotler (2000) adopted several of Schljakov's orders, while revising their membership and grouping them within a subclass "Metzgeriidae". These changes reflected a morphological analysis of species that had been presented three years earlier. Although their system changed
2210-741: The Metzgeriales. Names which are not linked belong to other groups. The results agree with the view that the Metzgeriales are paraphyletic as a result of including neither the Jungermanniales nor Pleuroziaceae (both shown in bold), which nest among the simple thalloid liverworts. Haplomitriales Treubiales Blasiales Sphaerocarpales Marchantiales Jungermanniales Pleuroziaceae Aneuraceae Metzgeriaceae Pelliaceae Calyculariaceae Makinoaceae Allisoniaceae Fossombroniaceae Petalophyllaceae Phyllothalliaceae Hymenophytaceae Moerckiaceae Pallaviciniaceae Sandeothallaceae Because plants belonging to
2275-605: The Phyllothalliaceae. The Metzgeriales traditionally included fourteen families, as follows: Families marked with an asterisk were classified in the separate order Fossombroniales by Crandall-Stotler and Stotler, but this grouping is not supported by subsequent analysis using DNA sequences. Two additional families were formerly included within the Metzgeriales, but since have been transferred to other classes of liverwort. The Blasiaceae has been assigned its own order Blasiales , and phylogenetic studies show that it
2340-523: The Upper Carboniferous of Shropshire , England, have been named Hepaticites metzgerioides , and (as the specific epithet indicates) these specimens strongly resemble the genus Metzgeria . However, they have been placed instead in the form genus Hepaticites , used for fossils believed to be liverworts but without confident affiliation with any extant order. This species is not restricted to British localities, but has also been found in
2405-596: The classification published from 1893 to 1895 by Schiffner in Engler and Prantl . Schiffner thus divided his "Jungermanniales" into two broad groups according to whether the archegonia were terminal on reproductive branches ( Jungermanniales akrogynae ) or sub-terminal ( Jungermanniales anakrogynae ). This latter group included what are now recognized as the Metzgeriales, Sphaerocarpales , and Haplomitriales . The simple thalloids were not given ordinal status until 1930 by Chalaud. Although subsequent systems similarly treated
2470-433: The correct authority for the ordinal name. He believed that Underwood had first used the term, but concluded that as neither Underwood nor Chalaud had provided a formal description, the order should be cited as "Metzgeriales Schust. emend. Schljak." He ascribed first use of the name with a description to his own 1953 work on the liverworts of Minnesota . This work included a considerable description sufficient to distinguish
2535-432: The family Canidae , which includes dogs, wolves, jackals, and all foxes; the next higher major taxon, Carnivora (considered an order), includes caniforms (bears, seals, weasels, skunks, raccoons and all those mentioned above), and feliforms (cats, civets, hyenas, mongooses). Carnivorans are one group of the hairy, warm-blooded, nursing members of the class Mammalia , which are classified among animals with notochords in
2600-599: The following ranks for these categories: The rules in the Code apply to the ranks of superfamily to subspecies, and only to some extent to those above the rank of superfamily. Among "genus-group names" and "species-group names" no further ranks are officially allowed, which creates problems when naming taxa in these groups in speciose clades, such as Rana . Zoologists sometimes use additional terms such as species group , species subgroup , species complex and superspecies for convenience as extra, but unofficial, ranks between
2665-464: The following taxonomic categories in the International Code of Nomenclature for Cultivated Plants : cultivar group , cultivar , grex . The rules in the ICN apply primarily to the ranks of family and below, and only to some extent to those above the rank of family. (See also descriptive botanical name .) Taxa at the rank of genus and above have a botanical name in one part (unitary name); those at
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2730-404: The fossils which have been found are often highly detailed and well-preserved. The oldest fossil bryophyte is a compression fossil of Pallavicinites devonicus from Upper Devonian rocks that has been confidently assigned to the Metzgeriales. Portions of the fossil that have been isolated for microscopic examination reveal an extraordinary degree of cellular detail. The plant consisted of
2795-480: The gradational nature of variation within nature. These problems were already identified by Willi Hennig , who advocated dropping them in 1969, and this position gathered support from Graham C. D. Griffiths only a few years later. In fact, these ranks were proposed in a fixist context and the advent of evolution sapped the foundations of this system, as was recognised long ago; the introduction of The Code of Nomenclature and Check-list of North American Birds Adopted by
2860-525: The group as distinct, the name of the order was more often given as "Jungermanniales anacrogynae" (or similar), or the group was retained within the Jungermanniales as a suborder with either this name or the name "Metzgerineae". The highly influential and comprehensive 1966 classification found in Schuster's Hepaticae and Anthocerotae of North America firmly established the name "Metzgeriales" for
2925-483: The group, although he had used this name in his earlier works. Schuster revised his system in 1972 and again in 1984. The only change he made in the circumscription of the Metzgeriales was to remove the Treubiales in accordance with that change made in the classification of Schljakov. Schljakov's 1972 classification had elevated several subordinal groups within the simple thalloids to the rank of order, and treated
2990-420: The groups where it occurs. Members of the Metzgeriales also differ from the related Jungermanniales in the location of their archegonia (female reproductive structures). Whereas archegonia in the Jungermanniales develop directly from the apical cell at the tip of a fertile branch, archegonia in the Metzgeriales develop from a cell that is behind the apical cell. As a result, the female reproductive organs, and
3055-434: The hierarchy of taxa (hence, their ranks) does not necessarily reflect the hierarchy of clades . While older approaches to taxonomic classification were phenomenological, forming groups on the basis of similarities in appearance, organic structure and behavior, two important new methods developed in the second half of the 20th century changed drastically taxonomic practice. One is the advent of cladistics , which stemmed from
3120-422: The lowest ranks. Ranks can be either relative and be denoted by an indented taxonomy in which the level of indentation reflects the rank, or absolute, in which various terms, such as species , genus , family , order , class , phylum , kingdom , and domain designate rank. This page emphasizes absolute ranks and the rank-based codes (the Zoological Code , the Botanical Code , the Code for Cultivated Plants ,
3185-405: The most basic (or important) is the species, but this opinion is not universally shared. Thus, species are not necessarily more sharply defined than taxa at any other rank, and in fact, given the phenotypic gaps created by extinction, in practice, the reverse is often the case. Ideally, a taxon is intended to represent a clade , that is, the phylogeny of the organisms under discussion, but this
3250-409: The most frequently advocated. Willi Hennig proposed it in 1966, but he concluded in 1969 that this system was unworkable and suggested dropping absolute ranks. However, the idea of ranking taxa using the age of origin (either as the sole criterion, or as one of the main ones) persists under the name of time banding, and is still advocated by several authors. For animals, at least the phylum rank
3315-419: The name of Metzgeriales "). Chalaud cited Underwood 1894 in support of his treatment, but Underwood himself used only the name Metzgeriaceae for the group, and considered the whole to represent a single family. The publication of the ordinal name by Chalaud was accepted as correct by Grolle in his 1983 synopsis of the generic and higher-rank names of liverworts. Writing in 1984, Rudolf M. Schuster questioned
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#17327907359803380-469: The name, although they restricted their circumscription of the order considerably. However, upon additional review of the Chalaud paper, they reversed their opinion. They concluded that Chalaud's diagnosis, although "terse", was nonetheless adequate to satisfy the requirements for publication of a botanical name , and that the Code' s requirement for a Latin diagnosis did not apply, since the Chalaud paper
3445-521: The order from all others, but Schuster relied on the 1972 emendation by Schljakov to provide the Latin diagnosis required by the International Code of Botanical Nomenclature . Schuster reaffirmed his position on the authority for publication in 1992. In the publication of their revised liverwort classification in 2000, Crandall-Stotler and Stotler agreed with Schuster as to the attribution of
3510-410: The order have a small gametophyte stage and a smaller, relatively short-lived, spore-bearing stage. Although these plants are almost entirely restricted to regions with high humidity or readily available moisture, the group as a whole is widely distributed, and occurs on every continent except Antarctica. Members of the Metzgeriales typically are small and thin enough to be translucent, with most of
3575-479: The phylum Chordata , and with them among all animals in the kingdom Animalia . Finally, at the highest rank all of these are grouped together with all other organisms possessing cell nuclei in the domain Eukarya . The International Code of Zoological Nomenclature defines rank as: "The level, for nomenclatural purposes, of a taxon in a taxonomic hierarchy (e.g. all families are for nomenclatural purposes at
3640-533: The rank and the Latin ending of the name, the composition was identical to the Metzgeriales of Schuster (1966), with only the addition of the Haplomitriales to its membership. Subsequent studies incorporating DNA sequence analysis have removed the Haplomitriales , Treubiales , and Blasiales and place those taxa elsewhere. The remnant of the group, after the removal of these taxa, consists of their Metzgeriales (7 families), Fossombroniales (4 families), and
3705-455: The rank of species and above (but below genus) have a botanical name in two parts ( binary name ); all taxa below the rank of species have a botanical name in three parts (an infraspecific name ). To indicate the rank of the infraspecific name, a "connecting term" is needed. Thus Poa secunda subsp. juncifolia , where "subsp". is an abbreviation for "subspecies", is the name of a subspecies of Poa secunda . Hybrids can be specified either by
3770-653: The rank-based codes; because of this, some systematists prefer to call them nomenclatural ranks . In most cases, higher taxonomic groupings arise further back in time, simply because the most inclusive taxa necessarily appeared first. Furthermore, the diversity in some major taxa (such as vertebrates and angiosperms ) is better known that that of others (such as fungi , arthropods and nematodes ) not because they are more diverse than other taxa, but because they are more easily sampled and studied than other taxa, or because they attract more interest and funding for research. Of these many ranks, many systematists consider that
3835-511: The relationships among the four genera placed in the family Aneuraceae: Riccardia Verdoornia (only species Verdoornia succulenta ) Lobatiriccardia Aneura (including former Cryptothallus ) [REDACTED] Media related to Aneuraceae at Wikimedia Commons This bryophyte -related article is a stub . You can help Misplaced Pages by expanding it . Taxonomic rank In biology , taxonomic rank (which some authors prefer to call nomenclatural rank because ranking
3900-401: The same rank, which lies between superfamily and subfamily)." Note that the discussions on this page generally assume that taxa are clades ( monophyletic groups of organisms), but this is required neither by the International Code of Zoological Nomenclature nor by the Botanical Code , and some experts on biological nomenclature do not think that this should be required, and in that case,
3965-466: The sporophytes that develop within them, are always located on the dorsal surface of the plant. Because these structures do not develop at the apex of the branch, their development in the Metzgeriales is described as anacrogynous , from Greek ἀν- ( an- , "not") + ἄκρος ( akros , "tip") + γυνή ( gynē , “female”). The group was accordingly known as the Anacrogynae prior to being recognized as
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#17327907359804030-485: The subgenus and species levels in taxa with many species, e.g. the genus Drosophila . (Note the potentially confusing use of "species group" as both a category of ranks as well as an unofficial rank itself. For this reason, Alain Dubois has been using the alternative expressions "nominal-series", "family-series", "genus-series" and "species-series" (among others) at least since 2000. ) At higher ranks (family and above)
4095-484: The tissues only a single cell layer in thickness. Because these plants are thin and relatively undifferentiated, with little evidence of distinct tissues, the Metzgeriales are sometimes called the "simple thalloid liverworts". There is considerable diversity in vegetative structure of the Metzgeriales. As a rule, simple thalloid liverworts do not have structures resembling leaves. However, a few genera, such as Fossombronia , and Symphyogyna , are "semileafy" and have
4160-727: The works of the German entomologist Willi Hennig . Cladistics is a method of classification of life forms according to the proportion of characteristics that they have in common (called synapomorphies ). It is assumed that the higher the proportion of characteristics that two organisms share, the more recently they both came from a common ancestor. The second one is molecular systematics, based on genetic analysis , which can provide much additional data that prove especially useful when few phenotypic characters can resolve relationships, as, for instance, in many viruses , bacteria and archaea , or to resolve relationships between taxa that arose in
4225-516: Was published prior to 1 January 1935. Chalaud is therefore the correct authority in citing the name "Metzgeriales". The Metzgeriales are a paraphyletic group of liverworts, in that they do not include all the descendants of their most recent common ancestor. Specifically, the Jungermanniales (leafy liverworts) are more closely related to the Aneuraceae and Metzgeriaceae than are other simple thalloid groups. The diagram at right summarizes
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