Aberlemnia is a genus of extinct vascular plants of the Early Devonian (around 420 to 390 million years ago), which consisted of leafless stems with terminal spore-forming organs (sporangia). Fossils found in Scotland were initially described as Cooksonia caledonica.[2] A later review, which included new and more complete fossils from Brazil, showed that the specimens did not fit the circumscription of the genus Cooksonia; accordingly a new genus Aberlemnia was proposed.[1]
Fossils from which the genus was first described were found in the Aberlemno quarry, Scotland. Other fossils now assigned to Aberlemnia caledonica have been found in Wales, Brazil and possibly Bolivia. Plants consisted of smooth leafless stems (axes) up to 1.4 mm wide, decreasing in width at each branching. Specimens branched up to five times, at angles between 25 and 55°, mainly dichotomously, although those from Brazil had some trichotomies. Spore-forming organs or sporangia were borne at the ends of the stems. Individual sporangia varied in shape. Smaller ones were more or less circular in outline, larger ones were kidney-shaped (reniform), up to 2 mm high and 3 mm wide. The difference in shape is interpreted as being due to growth and maturation. To release their spores, the sporangia split into two valves along the border opposite to the stem on which they were attached (i.e. distally).[1]
Taxonomyedit
Specimens were first attributed to Cooksonia caledonica by Edwards in 1970.[2] According to a review of the genus Cooksonia by Gonez and Gerrienne, the sporangium of the type species (C. pertoni) is formed by a widening of the end of a stem. At maturity the sporangium is topped by a flattish disk (an operculum) and releases its spores when this breaks up.[3] The sporangia of C. caledonica are quite different. No existing genus was considered to cover the precise morphology of this plant, so that a new genus Aberlemnia was put forward. The name is based on the location where the first fossils were found, Aberlemno in Scotland.[1]
In 2013, Hao and Xue classified Aberlemnia as a rhyniopsid, in the subgroup they called "renalioids", along with Renalia and Hsua.[4]
Phylogenyedit
Gonez and Gerrienne consider that Cooksonia is the most basal of the stem group of the lycophytes, whereas their genus Aberlemnia diverged later and is more derived. Consistent with this position, the genus has a combination of inherited features or plesiomorphies, such as dichotomous branching and terminal sporangia, with more advanced features, such as bivalved sporangia, which are characteristic of the lycophytes.[1] A cladistic study in which they included the two best-characterized species of Cooksonia, C. paranensis and C. pertonii, together with Aberlemnia caledonica (then still called C. caledonica) produced the following cladogram:[5]
^ abcdefGonez, P. & Gerrienne, P. (2010b), "Aberlemnia caledonica gen. et comb. nov., a new name for Cooksonia caledonica Edwards 1970", Review of Palaeobotany and Palynology, 163 (1–2): 64–72, doi:10.1016/j.revpalbo.2010.09.005
^ abEdwards, D. (1970), (PDF), Palaeontology, 13 (45): 1, archived from the original (PDF) on 2011-07-27, retrieved 2011-03-16
^Gonez, P. & Gerrienne, P. (2010a), "A New Definition and a Lectotypification of the Genus Cooksonia Lang 1937", International Journal of Plant Sciences, 171 (2): 199–215, doi:10.1086/648988, S2CID 84956576
^ abHao, Shougang & Xue, Jinzhuang (2013), The early Devonian Posongchong flora of Yunnan: a contribution to an understanding of the evolution and early diversification of vascular plants, Beijing: Science Press, p. 329, ISBN978-7-03-036616-0, retrieved 2019-10-25
aberlemnia, genus, extinct, vascular, plants, early, devonian, around, million, years, which, consisted, leafless, stems, with, terminal, spore, forming, organs, sporangia, fossils, found, scotland, were, initially, described, cooksonia, caledonica, later, rev. Aberlemnia is a genus of extinct vascular plants of the Early Devonian around 420 to 390 million years ago which consisted of leafless stems with terminal spore forming organs sporangia Fossils found in Scotland were initially described as Cooksonia caledonica 2 A later review which included new and more complete fossils from Brazil showed that the specimens did not fit the circumscription of the genus Cooksonia accordingly a new genus Aberlemnia was proposed 1 AberlemniaTemporal range Early Devonian PreꞒ Ꞓ O S D C P T J K Pg NScientific classificationKingdom PlantaeClade StreptophytaClade EmbryophytesClade PolysporangiophytesClade TracheophytesGenus AberlemniaGonez amp Gerrienne 2010 1 Type speciesAberlemnia caledonicaGonez amp Gerrienne 2010 SpeciesA bohemica Schweitzer 1980 Sakala Psenicka amp Kraft 2018 A caledonica Edwards 1970 Gonez amp Gerrienne 2010 1 Contents 1 Description 2 Taxonomy 3 Phylogeny 4 See also 5 ReferencesDescription editFossils from which the genus was first described were found in the Aberlemno quarry Scotland Other fossils now assigned to Aberlemnia caledonica have been found in Wales Brazil and possibly Bolivia Plants consisted of smooth leafless stems axes up to 1 4 mm wide decreasing in width at each branching Specimens branched up to five times at angles between 25 and 55 mainly dichotomously although those from Brazil had some trichotomies Spore forming organs or sporangia were borne at the ends of the stems Individual sporangia varied in shape Smaller ones were more or less circular in outline larger ones were kidney shaped reniform up to 2 mm high and 3 mm wide The difference in shape is interpreted as being due to growth and maturation To release their spores the sporangia split into two valves along the border opposite to the stem on which they were attached i e distally 1 Taxonomy editSpecimens were first attributed to Cooksonia caledonica by Edwards in 1970 2 According to a review of the genus Cooksonia by Gonez and Gerrienne the sporangium of the type species C pertoni is formed by a widening of the end of a stem At maturity the sporangium is topped by a flattish disk an operculum and releases its spores when this breaks up 3 The sporangia of C caledonica are quite different No existing genus was considered to cover the precise morphology of this plant so that a new genus Aberlemnia was put forward The name is based on the location where the first fossils were found Aberlemno in Scotland 1 In 2013 Hao and Xue classified Aberlemnia as a rhyniopsid in the subgroup they called renalioids along with Renalia and Hsua 4 Phylogeny editGonez and Gerrienne consider that Cooksonia is the most basal of the stem group of the lycophytes whereas their genus Aberlemnia diverged later and is more derived Consistent with this position the genus has a combination of inherited features or plesiomorphies such as dichotomous branching and terminal sporangia with more advanced features such as bivalved sporangia which are characteristic of the lycophytes 1 A cladistic study in which they included the two best characterized species of Cooksonia C paranensis and C pertonii together with Aberlemnia caledonica then still called C caledonica produced the following cladogram 5 Cooksonia paranensisCooksonia pertoniiSartilmania Uskiella YuniaRenaliaAberlemnia caledonica lycophytes zosterophyllslycopsids renalioids sensu Hao amp Xue 2013 4 See also editDevonian List of Early Devonian land plantsReferences edit a b c d e f Gonez P amp Gerrienne P 2010b Aberlemnia caledonica gen et comb nov a new name for Cooksonia caledonica Edwards 1970 Review of Palaeobotany and Palynology 163 1 2 64 72 doi 10 1016 j revpalbo 2010 09 005 a b Edwards D 1970 Fertile Rhyniophytina from the Lower Devonian of Britain PDF Palaeontology 13 45 1 archived from the original PDF on 2011 07 27 retrieved 2011 03 16 Gonez P amp Gerrienne P 2010a A New Definition and a Lectotypification of the Genus Cooksonia Lang 1937 International Journal of Plant Sciences 171 2 199 215 doi 10 1086 648988 S2CID 84956576 a b Hao Shougang amp Xue Jinzhuang 2013 The early Devonian Posongchong flora of Yunnan a contribution to an understanding of the evolution and early diversification of vascular plants Beijing Science Press p 329 ISBN 978 7 03 036616 0 retrieved 2019 10 25 Gonez amp Gerrienne 2010a redrawn from fig 13 p 213 Retrieved from https en wikipedia org w index php title Aberlemnia amp oldid 1068296670, wikipedia, wiki, book, books, library,
