34-456: The zosterophylls are a group of extinct land plants that first appeared in the Silurian period. The taxon was first established by Banks in 1968 as the subdivision Zosterophyllophytina ; they have since also been treated as the division Zosterophyllophyta or Zosterophyta and the class or plesion Zosterophyllopsida or Zosteropsida . They were among the first vascular plants in
68-486: A and b to harvest the light energy in sunlight for carbon fixation from carbon dioxide and water in order to synthesize carbohydrates while releasing oxygen as a byproduct . The Embryophytes emerged either a half-billion years ago, at some time in the interval between the mid- Cambrian and early Ordovician , or almost a billion years ago, during the Tonian or Cryogenian, probably from freshwater charophytes ,
102-419: A and b , generally giving them a bright green color. Embryophyte cells also generally have an enlarged central vacuole enclosed by a vacuolar membrane or tonoplast, which maintains cell turgor and keeps the plant rigid. In common with all groups of multicellular algae they have a life cycle which involves alternation of generations . A multicellular haploid generation with a single set of chromosomes –
136-464: A clade of multicellular green algae similar to extant Klebsormidiophyceae . The emergence of the Embryophytes depleted atmospheric CO 2 (a greenhouse gas ), leading to global cooling , and thereby precipitating glaciations . Embryophytes are primarily adapted for life on land, although some are secondarily aquatic . Accordingly, they are often called land plants or terrestrial plants. On
170-465: A microscopic level, the cells of charophytes are broadly similar to those of chlorophyte green algae, but differ in that in cell division the daughter nuclei are separated by a phragmoplast . They are eukaryotic , with a cell wall composed of cellulose and plastids surrounded by two membranes. The latter include chloroplasts , which conduct photosynthesis and store food in the form of starch , and are characteristically pigmented with chlorophylls
204-433: A mistaken belief that the two groups were related. David P. Penhallow 's generic description of the type genus Zosterophyllum refers to "Aquatic plants with creeping stems, from which arise narrow dichotomous branches and narrow linear leaves of the aspect of Zostera ." Zosterophyllum rhenanum was reconstructed as aquatic, the lack of stomata on the lower axes giving support to this interpretation. However, current opinion
238-399: A single cell. In the bryophytes the sporophyte remains dependent on the gametophyte, while in all other embryophytes the sporophyte generation is dominant and capable of independent existence. Embryophytes also differ from algae by having metamers . Metamers are repeated units of development, in which each unit derives from a single cell, but the resulting product tissue or part is largely
272-473: A slit-like opening in the middle of a single elongated guard cell, leading to comparison with the stomata of some mosses. However, this is now thought to result from the loss of the wall separating paired guard cells during fossilisation. At first most of the fossilized early land plants other than bryophytes were placed in the class Psilophyta, established in 1917 by Kidston and Lang. As additional fossils were discovered and described, it became apparent that
306-952: A unified cladogram for the polysporangiophytes (plants with branched stems bearing sporangia ), based on cladistic analyses of morphological features. This suggests that the zosterophylls were a paraphyletic stem group, related to the ancestors of modern lycophytes. † Hicklingia †basal groups ( Adoketophyton , Discalis , Distichophytum (= Rebuchia ), Gumuia , Huia , Zosterophyllum myretonianum , Z. lianoveranum, Z. fertile ) †'core' zosterophylls ( Zosterophyllum divaricatum , Tarella , Oricilla , Gosslingia , Hsua , Thrinkophyton , Protobarinophyton , Barinophyton obscurum , B. citrulliforme , Sawdonia , Deheubarthia , Konioria , Anisophyton , Serrulacaulis , Crenaticaulis ) †basal groups ( Nothia , Zosterophyllum deciduum ) lycopsids (extant and extinct members) Genera which are included at or around
340-820: Is not known. The affinity with zosterophylls is recognized in the cladogram published in 2004 by Crane et al. in which Hicklingia is placed as a sister to all the other lycophytes (living and extinct clubmosses and relatives). † Hicklingia Adoketophyton , Discalis , Distichophytum (= Rebuchia ), Gumuia , Huia , Zosterophyllum myretonianum , Z. llanoveranum, Z. fertile Zosterophyllum divaricatum , Tarella , Oricilla , Gosslingia , Hsua , Thrinkophyton , Protobarinophyton , Barinophyton obscurum , B. citrulliforme , Sawdonia , Deheubarthia , Konioria , Anisophyton , Serrulacaulis , Crenaticaulis Nothia , Zosterophyllum deciduum extant and extinct members Hao and Xue in 2013 listed
374-512: Is that the Zosterophylls were terrestrial plants, and Penhallow's "linear leaves" are interpreted as the aerial stems of the plant that had become flattened during fossilization. Stomata were present, particularly on the upper axes. Their absence on the lower portions of the axes suggests that this part of the plants may have been submerged, and that the plants dwelt in boggy ground or even shallow water. In many fossils these appear to consist of
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#1732855726033408-578: The Ordovician , streptophytes invaded the land and began the evolution of the embryophyte land plants. Present day embryophytes form a clade. Becker and Marin speculate that land plants evolved from streptophytes because living in fresh water pools pre-adapted them to tolerate a range of environmental conditions found on land, such as exposure to rain, tolerance of temperature variation, high levels of ultra-violet light, and seasonal dehydration. The preponderance of molecular evidence as of 2006 suggested that
442-570: The gametophyte – produces sperm and eggs which fuse and grow into a diploid multicellular generation with twice the number of chromosomes – the sporophyte which produces haploid spores at maturity. The spores divide repeatedly by mitosis and grow into a gametophyte, thus completing the cycle. Embryophytes have two features related to their reproductive cycles which distinguish them from all other plant lineages. Firstly, their gametophytes produce sperm and eggs in multicellular structures (called ' antheridia ' and ' archegonia '), and fertilization of
476-444: The mosses (Bryophyta), hornworts (Anthocerotophyta), and liverworts (Marchantiophyta), are relatively small plants, often confined to environments that are humid or at least seasonally moist. They are limited by their reliance on water needed to disperse their gametes ; a few are truly aquatic. Most are tropical, but there are many arctic species. They may locally dominate the ground cover in tundra and Arctic–alpine habitats or
510-574: The Psilophyta were not a homogeneous group of plants, and in 1975 Banks developed his earlier proposal to split it into three groups, which he put at the rank of subdivision. One of these was the subdivision Zosterophyllophytina, named after the genus Zosterophyllum . For Banks, zosterophyllophytes or zosterophylls comprised plants with lateral sporangia which released their spores by splitting distally (i.e. away from their attachment), and which had exarch strands of xylem . Bank's classification produces
544-550: The Viridiplantae split 1,200 million years ago to 725 million years ago into two clades: chlorophytes and streptophytes . The chlorophytes, with around 700 genera, were originally marine algae, although some groups have since spread into fresh water . The streptophyte algae (i.e. excluding the land plants) have around 122 genera; they adapted to fresh water very early in their evolutionary history and have not spread back into marine environments. Some time during
578-431: The ends by unrolling, a process known as circinate vernation . The stems had a central vascular column in which the protoxylem was exarch , and the metaxylem developed centripetally. The sporangia were kidney-shaped (reniform), with conspicuous lateral dehiscence and were borne laterally in a fertile zone towards the tips of the branches. The zosterophylls were named after the aquatic flowering plant Zostera from
612-565: The epiphyte flora in rain forest habitats. Hicklingia Hicklingia is a genus of extinct plants of the Middle Devonian (around 393 to 383 million years ago ). Compressed specimens were first described in 1923 from the Old Red Sandstone of Scotland . Initially the genus was placed in the " rhyniophytes ", but this group is defined as having terminal sporangia (spore-forming organs), and later work showed that
646-573: The fossil record, and had a world-wide distribution. They were probably stem-group lycophytes , forming a sister group to the ancestors of the living lycophytes. By the late Silurian (late Ludlovian, about 420 million years ago ) a diverse assemblage of species existed, examples of which have been found fossilised in what is now Bathurst Island in Arctic Canada . The stems of zosterophylls were either smooth or covered with small spines known as enations , branched dichotomously , and grew at
680-515: The genus, as having evolved separately from the lycopsids, so that its taxonomic placement was uncertain. Barinophytes , like Barinophyton , have been considered to be possible lycopsids, or to fall between the lycopsids and the euphyllophytes . Land plants Traditional groups: The embryophytes ( / ˈ ɛ m b r i ə ˌ f aɪ t s / ) are a clade of plants , also known as Embryophyta ( / ˌ ɛ m b r i ˈ ɒ f ə t ə , - oʊ ˈ f aɪ t ə / ) or land plants . They are
714-465: The groups making up the embryophytes are related as shown in the cladogram below (based on Qiu et al. 2006 with additional names from Crane et al. 2004). Liverworts [REDACTED] Mosses [REDACTED] Hornworts [REDACTED] Lycophytes [REDACTED] ( ferns and horsetails ) [REDACTED] Angiosperms ( flowering plants ) [REDACTED] Gymnosperms [REDACTED] An updated phylogeny of Embryophytes based on
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#1732855726033748-459: The hierarchy: Those who treat most of the extant groups of plants as divisions may raise both the zosterophylls and the Lycophytina sensu Banks to the rank of division: In their cladistic study published in 1997, Kenrick and Crane provided support for a clade uniting both the zosterophylls and the lycopsids, producing a classification which places the zosterophylls in a class Zosterophyllopsida of
782-459: The land plants in the streptophyte lineage, some species within their relatives Coleochaetales , Charales and Zygnematales , as well as within subaerial species of the algae order Trentepohliales , and appears to be essential in the adaptation towards a terrestrial life style. The green algae and land plants form a clade , the Viridiplantae . According to molecular clock estimates,
816-901: The most familiar group of photoautotrophs that make up the vegetation on Earth 's dry lands and wetlands . Embryophytes have a common ancestor with green algae , having emerged within the Phragmoplastophyta clade of freshwater charophyte green algae as a sister taxon of Charophyceae , Coleochaetophyceae and Zygnematophyceae . Embryophytes consist of the bryophytes and the polysporangiophytes . Living embryophytes include hornworts , liverworts , mosses , lycophytes , ferns , gymnosperms and angiosperms ( flowering plants ). Embryophytes have diplobiontic life cycles . The embryophytes are informally called "land plants" because they thrive primarily in terrestrial habitats (despite some members having evolved secondarily to live once again in semiaquatic / aquatic habitats ), while
850-437: The ovum takes place within the archegonium rather than in the external environment. Secondly, the initial stage of development of the fertilized egg (the zygote ) into a diploid multicellular sporophyte, takes place within the archegonium where it is both protected and provided with nutrition. This second feature is the origin of the term 'embryophyte' – the fertilized egg develops into a protected embryo, rather than dispersing as
884-450: The related green algae are primarily aquatic. Embryophytes are complex multicellular eukaryotes with specialized reproductive organs . The name derives from their innovative characteristic of nurturing the young embryo sporophyte during the early stages of its multicellular development within the tissues of the parent gametophyte . With very few exceptions, embryophytes obtain biological energy by photosynthesis , using chlorophyll
918-405: The same for each cell. The whole organism is thus constructed from similar, repeating parts or metamers . Accordingly, these plants are sometimes termed 'metaphytes' and classified as the group Metaphyta (but Haeckel 's definition of Metaphyta places some algae in this group ). In all land plants a disc-like structure called a phragmoplast forms where the cell will divide , a trait only found in
952-423: The sporangia of Hicklingia were lateral rather than strictly terminal, so that it is now regarded as having affinities with the zosterophylls . The sporophyte had a tufted growth habit, with narrow leafless stems (axes) up to 17 cm high which branched dichotomously. Sporangia were borne on short stalks (up to 3 mm), on all sides of the stem and also terminally. There are oval scars on specimens where
986-428: The stalks are presumed to have broken off. The lateral sporangia were closely adpressed to the stem. The effect is of a 'spike' of sporangia which terminates some stems. The sporangia opened via slits, but these did not have the thickened borders which are a feature of some Zosterophyllum species. The vascular system of the stem was not observed. Spores are up to 50 μm in diameter and trilete. The gametophyte
1020-435: The subdivision Lycophytina: This approach has been widely used alongside previous systems. A consequence is that "lycophyte" and corresponding formal names such as "Lycophyta" and "Lycophytina" are used by different authors in at least two senses: either excluding zosterophylls in the sense of Banks or including them in the sense of Kenrick and Crane. A further complication is that the cladograms of Kenrick and Crane show that
1054-980: The work by Novíkov & Barabaš-Krasni 2015 and Hao and Xue 2013 with plant taxon authors from Anderson, Anderson & Cleal 2007 and some additional clade names. Puttick et al./Nishiyama et al. are used for the basal clades. Anthocerotophytina (Hornworts) Bryophytina (Mosses) Marchantiophytina (Liverworts) † Horneophytopsida [Protracheophytes] † Cooksoniaceae † Aglaophyton † Rhyniopsida † Catenalis † Aberlemnia † Hsuaceae † Renaliaceae † Adoketophyton †? Barinophytopsida † Zosterophyllopsida † Hicklingia † Gumuia † Nothia Lycopodiopsida (Clubmosses, Spikemosses & Quillworts) † Zosterophyllum deciduum † Yunia † Eophyllophyton † Trimerophytopsida † Ibyka † Pauthecophyton † Cladoxylopsida Polypodiopsida (ferns) † Celatheca † Pertica † Progymnosperms (paraphyletic) Spermatophytes (seed plants) The non-vascular land plants, namely
Zosterophyll - Misplaced Pages Continue
1088-410: The zosterophyll position in the cladogram or have otherwise been included in the group by at least one source, and hence may be considered zosterophylls in the broadest sense, are listed below. "B" indicates genera included by Banks in his 1975 description of Zosterophyllophytina. Genera may not be assigned to this group by other authors; for example, Adoketophyton was regarded by Hao et al., who named
1122-632: The zosterophylls have been divided into orders and families , e.g. the Zosterophyllales containing the Zosterophyllaceae and the Sawdoniales containing the Sawdoniaceae. Since the publication of cladograms showing that the group is paraphyletic divisions of the class have been less used, being ignored, for example, in the 2009 paleobotany textbook by Taylor et al. In 2004, Crane et al. published
1156-457: The zosterophylls, broadly defined, are paraphyletic, but contain a 'core' clade of plants with marked bilateral symmetry and circinate tips. The class Zosterophyllopsida sensu Kenrick & Crane may be restricted to this core clade, leaving many genera (e.g. Hicklingia , Nothia ) with no systematic placement other than Lycophytina sensu Kenrick & Crane, but nevertheless still informally called "zosterophylls". Under whatever name and rank,
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