View source for Pleiacanthus spinosus

{{Treatment/ID
|accepted_name=Pleiacanthus spinosus
|accepted_authority=(Nuttall) Rydberg
|publications={{Treatment/Publication
|title=Fl. Rocky Mts.,
|place=1069. 1917
|year=1917
}}
|common_names=Thorny skeletonweed
|special_status={{Treatment/ID/Special_status
|code=F
|label=Illustrated
}}{{Treatment/ID/Special_status
|code=E
|label=Endemic
}}
|basionyms={{Treatment/ID/Basionym
|name=Lygodesmia spinosa
|authority=Nuttall
|rank=species
|publication_title=Trans. Amer. Philos. Soc., n. s.
|publication_place=7: 444. 1841
}}
|synonyms={{Treatment/ID/Synonym
|name=Stephanomeria spinosa
|authority=(Nuttall) Tomb
|rank=species
}}
|hierarchy=Asteraceae;Asteraceae tribe Cichorieae;Pleiacanthus;Pleiacanthus spinosus
|hierarchy_nav=<div class="higher-taxa"><div class="higher-taxon"><small>family</small>[[Asteraceae]]</div><div class="higher-taxon"><small>tribe</small>[[Asteraceae tribe Cichorieae]]</div><div class="higher-taxon"><small>genus</small>[[Pleiacanthus]]</div><div class="higher-taxon"><small>species</small>[[Pleiacanthus spinosus]]</div></div>
|volume=Volume 19
|mention_page=page 351
|treatment_page=page 361
}}<!--

--><span class="statement" id="st-undefined" data-properties=""><b>Stems:</b> branches 4–8 cm. <b>Leaves</b>: proximal 3–7 cm. <b>Peduncles</b> 1–4 mm. <b>Calyculi</b>: bractlets 4–8 × 1.5–2.5 mm, glabrous. <b>Involucres</b> 7–12 mm. <b>Cypselae</b> 6–8 mm; pappus bristles: the longer 7–11 mm, shorter 5–7 mm. <b>2n</b> = 16.</span><!--

-->{{Treatment/Body
|phenology=Flowering Jul–Sep.
|habitat=Open, sandy, gravelly washes and slopes, desert shrub, pinyon-juniper communities
|elevation=1500–2900 m
|distribution=Ariz.;Calif.;Idaho;Mont.;Nev.;Oreg.;Utah.
|discussion=<p><i>Pleiacanthus spinosus</i> was first collected by Nuttall, who placed it in <i>Lygodesmia</i>. Rydberg elevated it to the genus level; his proposal was not taken up by others. The species remained in <i>Lygodesmia</i> until A. S. Tomb (1970) transferred it to <i>Stephanomeria</i>. Tomb made the transfer because <i>P. spinosus</i> has the same base chromosome number as <i>Stephanomeria</i> (x = 8) as well as similar echinate pollen grains (Tomb 1974; Tomb et al. 1974) and thereby differs from <i>Lygodesmia</i>, which has x = 9 and echinolophate pollen. <i>Pleiacanthus spinosus</i> also has morphologic traits not shared with any stephanomeria. These include dense, long tufts of wool in the ground-level axils of the bud scales of the stems, sharp-tipped branches and stems, and pappus bristles that are of two lengths and not plumose. Recent results of DNA sequencing studies of <i>Stephanomeria</i> and related North American genera showed that <i>P. spinosus</i> is not a member of the clade of all stephanomerias (J. Lee et al. 2002).</p>
|tables=
|references=
}}<!--

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-->{{#Taxon:
name=Pleiacanthus spinosus
|authority=(Nuttall) Rydberg
|rank=species
|parent rank=genus
|synonyms=Stephanomeria spinosa
|basionyms=Lygodesmia spinosa
|family=Asteraceae
|phenology=Flowering Jul–Sep.
|habitat=Open, sandy, gravelly washes and slopes, desert shrub, pinyon-juniper communities
|elevation=1500–2900 m
|distribution=Ariz.;Calif.;Idaho;Mont.;Nev.;Oreg.;Utah.
|reference=None
|publication title=Fl. Rocky Mts.,
|publication year=1917
|special status=Illustrated;Endemic
|source xml=https://bibilujan@bitbucket.org/aafc-mbb/fna-data-curation.git/src/bb6b7e3a7de7d3b7888a1ad48c7fd8f5c722d8d6/coarse_grained_fna_xml/V19-20-21/V19_573.xml
|tribe=Asteraceae tribe Cichorieae
|genus=Pleiacanthus
|species=Pleiacanthus spinosus
}}<!--

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