The Indo-Pacific genus Halgerda Bergh, 1880a Verhandlungen Der Koniglich-Kaiserlichen Zoologisch-Botanischen Gesellschaft in Wien 30:155–200, is one of the most diverse and better-studied genera within the nudibranch family Discodorididae. Previous studies have been predominantly based on morphology; however, the addition of molecular data has led to new species descriptions as well as unresolved species complexes. Here, we broaden the available molecular data within Halgerda by utilizing two mitochondrial and two nuclear genes in coordination with morphology to describe 14 new Halgerda species. Bayesian inference, maximum likelihood, and species delimitation analyses were used to clarify previously established relationships and evaluate the new species positions within Halgerda. Based on our results Halgerda elegans Bergh, 1905 is synonymized with Halgerda willeyi Eliot, 1904 and new descriptions for Halgerda mango sp. nov., Halgerda berberiani sp. nov., Halgerda biqiea sp. nov., Halgerda paulayi sp. nov., Halgerda labyrinthus sp. nov., Halgerda anosy sp. nov., Halgerda mesophotica sp. nov., Halgerda profunda sp. nov., Halgerda takipsilim sp. nov., Halgerda scripta sp. nov., Halgerda hervei sp. nov., Halgerda maaikeae sp. nov., Halgerda pattiae sp. nov., and Halgerda radamaensis sp. nov. are provided here. We also provide an updated morphological description for juvenile specimens of Halgerda dalanghita Fahey & Gosliner, 1999a; expand upon the two unresolved species complexes previously identified in Tibiriçá et al. (2018); and identify a new mesophotic clade in the Central Pacific.

Depth range
3- 100 m

Mesophotic “mentions”
89 x (total of 36194 words)

Classification
* Presents original data
* Reports new species
* Focused on 'mesophotic' depth range
* Focused on 'mesophotic coral ecosystem'

Fields
Biodiversity
Evolution
Molecular ecology
Taxonomy

Focusgroups
Other invertebrates

Locations
Australia - Great Barrier Reef
Cook Islands
Djibouti
French Polynesia
Indonesia
Japan - Ryukyu Islands (Okinawa)
Madagascar
Mayotte
Micronesia - Guam
New Caledonia
Papua New Guinea
Philippines
Saudi Arabia - Red Sea
South Africa
Tanzania
USA - Hawaii
Mozambique