Convergent evolution: A new subfamily for bipaliin-like Chilean land planarians (platyhelminthes)

The monotypic genus of land planarians Timyma (Rhynchodeminae, Geoplanidae) has been suggested to be a relict that could reflect a pre-Tertiary Antarctic connection between South America and Australia and New Zealand. Two species belonging to this genus, Timyma juliae E. M. Froehlich, 1978 and Timyma olmuensis Almeida & Carbayo sp. n., are (re)described herein. Both species present ventral testes and a semilunate headplate, the same as the members of the Oriental subfamily Bipaliinae. Timyma olmuensis Almeida & Carbayo sp. n. is studied by means of an integrative approach. Two nuclear gene fragments (28S, EF) and a mitochondrial gene fragment (COI) were sequenced. Phylogenetic analyses pointed out that Timyma is the sister-group of the Neotropical Geoplaninae and is phylogenetically distant from Bipaliinae, contradicting the hypothesis of Timyma as a South American relict of a Gondwanan taxon. These results indicate that the headplate evolved independently in Timyma and Bipaliinae. Morphological data reinforce this view. Accordingly, Timyminae subfam. n. is proposed for Timyma and a new diagnosis for the genus is proposed.

Automated summary

The monotypic genus of land planarians Timyma is suggested to be a relict reflecting a pre-Tertiary connection between South America and Australia and New Zealand, with unique morphological characteristics. Research indicates that Timyma is more closely related to the Neotropical Geoplaninae subfamily and distantly related to the Bipaliinae subfamily in terms of phylogenetic relationships.