Noren & Jondelius (2002) (citation) declare "The Neoophora is rendered non-monophyletic by the sister-group position of the ‘archoophoran’ Haplopharynx rostratus Meixner, 1938 (Haplopharyngida) to the Lecithoepitheliata, with moderate support" on p. 408. However, Rieger (2001) (citation) also considered such molecular-sequence data (from Littlewood et al. 1999) (citation) and rejected the notion that Haplopharynx rostratus would fall outside of the Macrostomorpha in light of the numerous morphological characters and their evolution within the Macrostromorpha. That is, a split of the Macrostomida and Haplopharyngida is not valid, and a sister-group relation between Haplopharyngida and Lecithoepitheliata is unlikely. The only morphological characters supporting the Haplopharyngida/Lecithoepitheliata relationship are those of the penial structures and the follicular surrounding of accessory cells.
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