The phylogeny and generic delimits within the Homalomena clade and Philodendron clade have been receiving considerable attention from systematists in recent years.  Relevant papers include the following:

Ferreira et al (2020) : Anatomy of the adventitious roots of Philodendron (Araceae) and its importance for the systematics of the genus 

Vasconcelos et al. (2018): New insights on the phylogenetic relationships among the traditional Philodendron subgenera and the other groups of the Homalomena clade (Araceae)

Canal et al. (2018): Phylogeny and diversification history of the large Neotropical genus Philodendron (Araceae): Accelerated speciation in a lineage dominated by epiphytes

Sakuragui et al. (2018): Recognition of the genus Thaumatophyllum Schott − formerly Philodendron subg. Meconostigma (Araceae) − based on molecular and morphological evidence

Loss-Oliveira et al. (2016): Evolution of Philodendron (Araceae) species in Neotropical biomes

Wong et al. (2016): Resurrection and New Species of the Neotropical Genus Adelonema (Araceae: Philodendron Clade)

Loss-Oliveira et al. (2014): Floral Evolution of Philodendron Subgenus Meconostigma (Araceae)

Calazans, L.S.B., Sakuragui, C.M., Mayo, S.J. (2014): From open areas to forests? The evolutionary history of Philodendron subgenus Meconostigma (Araceae) using morphological data

Wong et al. (2013): Phylogeny of Asian Homalomena (Araceae) based on the ITS Region Combined with Morphological and Chemical Data

Mayo et al. (2013): Recent progress in the phylogenetics and classification of Araceae

Nauheimer et al. (2012): Global history of the ancient monocot family Araceae inferred with models accounting for past continental positions and previous ranges based on fossils

Cusimano et al. (2011): Relationships within the Araceae: comparison of morphological patterns with molecular phylogenies

Gauthier et al. (2008): Molecular phylogeny of the genus Philodendron (Araceae): delimitation and infrageneric classification

Gonçalves and Salviani (2002): New species and changing concepts of Philodendron subgenus Meconostigma (Araceae)

Mayo, Bogner and Boyce (1997): The genera of Araceae

Mayo (1991): A revision of Philodendron subgenus Meconostigma (Araceae)

Mayo (1990): History and infrageneric nomenclature of Philodendron (Araceae)