Editing Gnetophyta (section)

===Gnepine hypothesis===
The gnepine hypothesis is a modification of the gnetifer hypothesis, and suggests that the gnetophytes belong within the conifers as a sister group to the [[Pinaceae]].<ref name=Judd/> According to this hypothesis, the conifers as currently defined are not a monophyletic group, in contrast with molecular findings that support its monophyly.<ref name=Rydin/> All existing evidence for this hypothesis comes from molecular studies since 1999.<ref name=Bowe/><ref name=Gugerli/><ref name=Chaw2/><ref name=Hajibabaei/><ref name=Magallon/><ref name=Qui/><ref name=Sanderson/><ref name=Burleigh/><ref name=Ran2018>{{cite journal|doi=10.1098/rspb.2018.1012|title=Phylogenomics resolves the deep phylogeny of seed plants and indicates partial convergent or homoplastic evolution between Gnetales and angiosperms|year=2018|last1=Ran|first1=Jin-Hua|last2=Shen|first2=Ting-Ting|last3=Wang|first3=Ming-Ming|last4=Wang|first4=Xiao-Quan|journal=Proceedings of the Royal Society B: Biological Sciences|volume=285|issue=1881|pmid=29925623|pmc=6030518}}</ref><ref name=Stull2021>{{cite journal|doi=10.1038/s41477-021-00964-4|title=Gene duplications and phylogenomic conflict underlie major pulses of phenotypic evolution in gymnosperms|year=2021|last1=Stull|first1=Gregory W.|last2=Qu|first2=Xiao-Jian|last3=Parins-Fukuchi|first3=Caroline|last4=Yang|first4=Ying-Ying|last5=Yang|first5=Jun-Bo|last6=Yang|first6=Zhi-Yun|last7=Hu|first7=Yi|last8=Ma|first8=Hong|last9=Soltis|first9=Pamela S.|last10=Soltis|first10=Douglas E.|last11=Li|first11=De-Zhu|last12=Smith|first12=Stephen A.|last13=Yi|first13=Ting-Shuang|journal=Nature Plants|volume=7|issue=8|pages=1015–1025|pmid=34282286|s2cid=236141481}}</ref> A 2018 phylogenomic study estimated the divergence between Gnetales and Pinaceae at around 241 millions of years ago, in the early [[Triassic]]<ref name=Ran2018/> while a 2021 study placed it earlier, in the [[Carboniferous]].<ref name=Stull2021/>

However, the morphological evidence remains difficult to reconcile with the gnepine hypothesis. If the gnetophytes are nested within conifers, they must have lost several shared derived characters of the conifers (or these characters must have evolved in parallel in the other two conifer lineages): narrowly triangular leaves (gnetophytes have diverse leaf shapes), [[resin]] canals, a tiered [[proembryo]], and flat woody ovuliferous [[Conifer cone|cone]] scales.<ref name=Magallon/> These kinds of major morphological changes are not without precedent in the [[Pinales]], however: the [[Taxaceae]], for example, have lost the classical cone of the conifers in favor of a single-terminal ovule, surrounded by a fleshy aril.<ref name=Chaw2/>

{{clade 
  |1=[[angiosperm]]s (flowering plants)
  |label2=[[gymnosperm]]s  
  |2={{clade 
    |1=[[cycad]]s 
    |2=''[[Ginkgo]]'' 
    |label3=[[conifer]]s
    |3={{clade 
      |label1=“'''Gnepines'''”
      |1={{clade 
        |1=[[Pinaceae]] (the pine family) 
        |2=[[gnetophytes]]
      }} 
      |2=(other conifers)
    }}
  }}
}}