The endemic New Caledonian Solmsia Baill. (Thymelaeaceae Juss.: Octolepidoideae Gilg) was founded in 1871 on two species, S. calophylla Baill. and S. chrysophylla Baill. Over the past 150 years, the genus has received little attention taxonomically or otherwise. New morphological, ecological and distribution information gathered from 484 herbarium specimens indicate that the two currently recognized species (evaluated as morphogroups) exhibit continuous, overlapping variation based on statistical multivariate analyses. Both partially sympatric morphogroups are treated here as conspecific under S. calophylla, the lectotype of the genus, and formal recognition of either group at any infraspecific rank is deemed unnecessary. The recircumscribed, single species is completely restricted to Grande Terre, where it occurs in maquis vegetation on ultramafic rocks (peridotite and serpentinite) and some form of ferrallitic soil (ferralsols/oxisols). Lectotypes, selected from a total of c. 55 sheets representing probable or possible syntypes, are designated for both of Baillon’s binomials. Full descriptions are provided for the genus and species, accompanied by illustrations, photographs, a distribution map, and a preliminary IUCN conservation assessment of Near Threatened (NT). Morphological and biogeographical relationships of Solmsia are discussed in the phylogenetic context of other Octolepidoideae, a basal subfamily of Thymelaeaceae, along with the closely related, but massively disjunct, Guayana Shield-centered Tepuianthus Maguire & Steyerm. (formerly Tepuianthaceae Maguire & Steyerm.). Dehiscence and capsule size at maturity are also confirmed and documented, respectively, for the first time in the closely related, Deltaria Steenis, another poorly known New Caledonian monospecific endemic genus.
Thymelaeaceae, Deltaria, Lethedon, Octolepidoideae, New Caledonia, Grande Terre, morphometric analysis, ecology, ultramafic substrate, IUCN Red List, lectotypification