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Diaphorodendron, Gen. Nov., a Segregate from Lepidodendron (Peiiiisylvaiiian Age) William A. Dimichele Systematic Botany, Vol. 1

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Diaphorodendron, Gen. Nov., a Segregate from Lepidodendron (Peiiiisylvaiiian Age) William A. Dimichele Systematic Botany, Vol. 1 Diaphorodendron, gen. nov., a Segregate from Lepidodendron (Peiiiisylvaiiian Age) STOR William A. DiMichele Systematic Botany, Vol. 10, No. 4 (Oct. - Dec, 1985), 453-458. Stable URL: http://links.jstor.org/sici?sici=0363-6445%28198510%2F12%2910%3A4%3C453%3ADGNASF%3E2.0.CO%3B2-0 Systematic Botany is currently published by American Society of Plant TaxonomisLs. Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/about/teiTns.html. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http: //w w w .j s tor. org/j oum al s/aspt. h tml. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is an independent not-for-profit organization dedicated to creating and preserving a digital archive of scholarly journals. For more information regarding JSTOR, please contact [email protected]. http: //w w w .j s tor. org/ ThuSep 2 10:51:30 2004 SysUmaia: Balann (I9i&), 10(4): pp. 453-458 © Copyright 19flS by the Atnericari Society of PLarkt TijtorkOmists DiAphorodendron, gen. nov., a Segregate from Lepidodendron (Pennsylvanian Age) WILLIAM A. DIMICHELE Department of Botany, UaLversity of Washington, Seattle, Washington 98195 ABSTRACT. Diaphorodendron is described as a new genus on the basis of anatomically preserved specimens previously included in Lepidodendroti. Species include D. vasculare (type species), D. sderolii^tiW., D. dicentricum, and D. phillLpsii. Circumscription of this new genus leaves Lepidodendron as a monophyletic, morphologically cohesive taxon. Traditionally Lepidodendron has been recog- nized by its higher-than-wide leaf cushions, a character that appears to be the ancestral (pleslo- morphic) state in the Lepldodendrales. The consequence of relying on this single trait has been inclusion of forms distinct in most aspects of basic morphology within Lepidodendron, masking rather extensive diversification in the Lepidodendrales. While sharing basic leaf-cushion shape, Diaphorodendron and Lepidodendron differ in. many anatomical features and details of leaf-cushion, morphology (especially relative "thickness" of leaf cushions and presence or absence of infrafoliar parichnos). By correlating anatomy and leaf-cushion morphology, characteristics can be recognized by which Diaphorodendron and Lepidodendron can be distinguished in compression preservation. The purpose of this report is to establish a was associated with leaf cushions having height new generic name for a distinctive, structural- to width ratios greater than one {the principal ly-preserved group of Pennsylvanian-age lep- character by which Lepidodendron was recog- idodendrid lycopods previously included in the nized). They concluded that anatomy varied genus Lepidodendron Sternberg. The species that greatly within a genus and therefore was not form the nucleus of this segregate genus are useful in distinguishing genera of lepidoden- Lepidodendron vasculare Binney, L. sderoticum drids. This view has prevailed in the literature Pannell, L. phillipsii DiMichele, and L. dicentri- until recently even though it would appear cum Felix {=L. schizostelicum Arnold) {see more reasonable to conclude that the character DiMichele 1979b, 1981, 1983a). of having higher-than-wide leaf cushions is in- Historical factors have confused and compli- appropriate for delimiting Lepidodendron. cated the taxonomy of lepidodendrids. This is The extensive anatomical data base can be most apparent in the application of taxonomic used to resolve questions of lycopod taxonomy concepts based on compression-impression if anatomically preserved leaf-cushion mor- specimens to anatomically-preserved speci- phologies are characterized in such a way that mens. Compression specimens display only ex- they can he compared to the compression rec- ternal morphology; many such characters po- ord. This, in turn, would allow correlation of tentially have a high degree of covariation and compression taxa with more broadly-circum- probable correlation {leaf cushion traits such as scribed anatomical taxa, and improve our un- height, width, etc.). Anatomically-pre served derstanding of the taxonomic significance of specimens offer a much larger suite of charac- variability in leaf-cushion form. For example, ters for comparison, and include most of those the type species of Lepidodendron, L. aculeatum that can be observed in compressions. Generic Sternberg {Thomas 1970), is based on compres- concepts in lycopods, in almost all cases, were sion specimens. While several distinctive ana- first established on the basis of compression tomically-based taxa have leaf cushions that are specimens. Thus, the application of names be- higher than wide, only one, Lepidodendron hickii tween preservational-types has been largely Watson, has leaf cushions with the character- unidirectional. Names used for compression- istics found only in L. aculeatum and similar impression specimens have been used to en- compression forms: radially raised or protrud- compass anatomically preserved forms. One of ing leaf cushions that bear infrafoliar parich- the best examples of this is provided by Lepi- nos, and that change shape from slightly elon- dodendron. Scott (1906) and Seward (1906) not- gate on small branches to relatively more ed that more than one distinct kind of anatomy elongate on larger stems (Watson 1907; Di- 453 454 SYSTEMATIC BOTANY [Volume 10 Michele 1983a). Height to width ratio alone will In a series of earlier articles I have attempted not permit correlation of the type species of to re-circumscribe these forms and illustrate that Lepidodendron with one of the several distinct no intermediates have yet been found (Di- kinds of stem anatomies that have vertically Michele 1979a, b, 1980, 1981, 1983a). The rec- elongate leaf cushions. Certain "minor" attri- ognition of an additional genus, segregated butes of cushion morphology allow the L. acu- from Lepidodendron, will largely complete the leatum-L. hickii correlation. As a consequence, process of defining architecturally distinct, it is now possible to segregate other taxa from monophyletic genera of Pennsylvanian-age Lepidodendron that have anatomy and aspects of lepidodendrid lycopods. Two genera described leaf-cushion morphology different from those from compressions have yet to be described of L. aaileaium-L. hickii. This paper concerns one convincingly from petrifactions, Bothrodendron of these segregates. and Asolanus. Both of these may be subsumed by already recognized forms, or may be found ANATOMICALLY-PRESERVEDMORPHOTYPES to have distinctive structural organization. {GENERA) OF PENNSVLVANIAN AGE The anatomically-preserved Pennsylvanian- Diaphotodendton DiMichele, gen. nov.—TYPE: age lepidodendrida represent six distinct or- Diaphorodendron vASCulnre (Binney) ganizational plans. Stem organ-taxa can be cor- DiMichele, comb. nov. BASIONYM: Lepido- related with cone organ-taxa by two means, in dendron vasculare Binney, Quart. J. Geol. Soc. the absence of attachment. First, co-occurrence Lond. 18:106-112, pi. IV, figs. 1-5, 1862. in coal balls (concretions of structural peat from Binney described and illustrated only one coal seams) is particularly compelling if only specimen.—TYPE: Slides prepared from one species of lycopod stem and one kind of Binney specimen No, 3—SM M. 4318 a-e; lycopod reproductive organ are known from Sedgwick Museum, University of Cam- the coal deposit. Second, comparison of cone- bridge, Cambridge, England. Collection axis anatomy with various metric and anatom- locality; Bullion Mine, Spa Clough, Burn- ical aspects of stem anatomy and morphology ley, Lancashire, England. Stratigraphy: may indicate that the organs are parts of the Westphalian A {Lower Pennsylvanian), same natural taxon. The following architec- Lower Coal Measures, Lancashire, [Illus- tural groups have been recognized—(stem trations in Binney {1862) include SM M. names are given first, followed by reproductive 4318 a = pi. IV, figs. 2 and 3; SM M. 4318 structures): 1) Lepidophloios-Lepidostrohus old- b = pi. IV, fig. 4; SM M. 4318 c = pi. IV, hamiiis-LepidQcarpon, 2) Sigiilaria-Mazocar- fig. S.] pon, 3) Paralycopodites-Flemingites (Flemingites Description of genus. Diaphorodendron in- is a recent segregate from Lepidostrobus, see cludes lycopods with arborescent habit. Growth Brack-Hanes and Thomas 1983), 4) Sublepi- form is either an excurrent trunk bearing de- dophloios (no cone correlation yet possible), 5) ciduous lateral branches, or a columnar trunk, Ldpidodendron-Achlamydocarpon takhtajanii, 6) which at maturity terminated growth with a "Lepidodendron" {DiaphoTodendrQn)-Achlamydo- dendritic, synchronously determinate crown. carpon varius. The two species of cones included Branching is anisotomous. Leaf cushions are in the genus 4cWarnydocarpon, A. takhtajanii and vertically elongate on stems of all sizes; their A. varius, have no substantive anatomical sim- ornamentation is simple and may include shal- ilarities (DiMichele 1983a), so their placement low plications above or below the leaf scar. in this genus does not reflect close pbyloge- Parichnos are strictly
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