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On the separation of Thaumatophyllum from Philodendron

Last Edit: 2018/8/7

According to Sakuragui et al (2018), members of the new Thaumatophyllum group are easily distinguished by diagnostic morphological characters as well as by a distinct ecology and geographical distribution. They proposed the recognition of P. subg. Meconostigma as a distinct genus based on molecular, morphological and cytological evidence:

• Molecular studies consistently showed Thaumatophyllum as monophyletic and a sister group to the rest of the Philodendron.
  
  
• Thaumatophyllum can be defined as having an arborescent habit, with thickened spathe, well developed sterile intermediate zone in the inflorescence equal or longer than the staminate zone, the gynoecium always having stylar lobes, and an axial vascular system independent of the funicle supply.
  
  
• In Thaumatophyllum, the squamules occur immediately below the prophyll scar and often surround the foliage leaf scar as well, unlike in mature internodes of Philodendron, where the squamules are always found immediately above the prophyll scar.
  
  
• In the Thaumatophyllum spadix, the long staminodial zone equals or exceeds the fertile male zone, which distinguishes it from the genus Philodendron.
  
  
• Chromosome number in the Thaumatophyllum range from 2n = 28 to 36, with a clear prevalence of 2n = 36, while chromosome numbers for Philodendron range from 2n = 28 to 40 with a prevalence of 2n = 32.
  
  
• Thaumatophyllum species have a preference for open environments with higher light intensity, and the ability to tolerate a certain degree of drought.

Reference:

Sakuragui CM, Calazans LSB, de Oliveira LL, de Morais EB, Benko-Iseppon AM, Vasconcelos S, Schrago CEG, Joseph Mayo SJ (2018) Recognition of the genus Thaumatophyllum Schott - formerly Philodendron subg. Meconostigma (Araceae) - based on molecular and morphological evidence. PhytoKeys 98: 51–71.