Morphological, molecular, and chemical characters support the transfer of the tropical demosponge genus Rhabdastrella to the family Geodiidae
Abstract
Rhabdastrella is a subtropical/tropical demosponge genus holding 18 species distributed predominantly in the Indo-Pacific region. Rhabdastrella is currently part of the Ancorinidae family (order Tetractinellida). However, previous molecular phylogenetic analyses and chemistry studies have repeatedly suggested that it has close evolutionary relationships with the genus Geodia, in the Geodiidae family (order Tetractinellida). This study provides new data from morphology, molecular markers (COI, 28S, and 18S) and sterols to re-evaluate this relationship. By revising several species of Rhabdastrella, including the type species of the genus Rhabdastrella distincta, this study strongly supports that this genus is polyphyletic and distributed within a group of Geodia, here informally called ‘Isops’. Moreover, Rhabdastrella and Geodia species from this group share unique C29-C30 sterols with additional alkyl groups in carbons 24 and 26, precursors of the 26-methylstigmastane (26-mes) sterane—a hypothesized ‘sponge biomarker’ identified in Neoproterozoic oils/rocks. We propose to formally reallocate Rhabdastrella to the Geodiidae, including a total of 14 species kept together for the time being until full revision of these species. As for other species, we propose (i) to move Rhabdastrella virgula to the genus Caminus, (ii) to reallocate four species of Rhabdastrella to the genus Geodia, and (iii) to move Jaspis coreana to the genus Rhabdastrella.
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BibTeX
@article{cardenas2026morphological,
title = {{Morphological, molecular, and chemical characters support the transfer of the tropical demosponge genus Rhabdastrella to the family Geodiidae}},
author = {Paco Cárdenas and Jayani Gamage and J Alex Zumberge and Hesham El-Seedi and Julio Díaz and Yusheng Huang and Jean Vacelet and Nathan Marshall and Merrick Ekins and R Jayasinghe and Chamari Hettiarachchi and Gordon Love and Sunithi Gunasekera},
journal = {Zoological Journal of the Linnean Society},
year = {2026},
month = sep,
doi = {10.1093/zoolinnean/zlag138},
url = {https://hal.science/hal-05748450v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Morphological, molecular, and chemical characters support the transfer of the tropical demosponge genus Rhabdastrella to the family Geodiidae
AU - Paco Cárdenas
AU - Jayani Gamage
AU - J Alex Zumberge
AU - Hesham El-Seedi
AU - Julio Díaz
AU - Yusheng Huang
AU - Jean Vacelet
AU - Nathan Marshall
AU - Merrick Ekins
AU - R Jayasinghe
AU - Chamari Hettiarachchi
AU - Gordon Love
AU - Sunithi Gunasekera
PY - 2026
DA - 2026/09/01
JO - Zoological Journal of the Linnean Society
DO - 10.1093/zoolinnean/zlag138
UR - https://hal.science/hal-05748450v1
AB - Rhabdastrella is a subtropical/tropical demosponge genus holding 18 species distributed predominantly in the Indo-Pacific region. Rhabdastrella is currently part of the Ancorinidae family (order Tetractinellida). However, previous molecular phylogenetic analyses and chemistry studies have repeatedly suggested that it has close evolutionary relationships with the genus Geodia, in the Geodiidae family (order Tetractinellida). This study provides new data from morphology, molecular markers (COI, 28S, and 18S) and sterols to re-evaluate this relationship. By revising several species of Rhabdastrella, including the type species of the genus Rhabdastrella distincta, this study strongly supports that this genus is polyphyletic and distributed within a group of Geodia, here informally called ‘Isops’. Moreover, Rhabdastrella and Geodia species from this group share unique C29-C30 sterols with additional alkyl groups in carbons 24 and 26, precursors of the 26-methylstigmastane (26-mes) sterane—a hypothesized ‘sponge biomarker’ identified in Neoproterozoic oils/rocks. We propose to formally reallocate Rhabdastrella to the Geodiidae, including a total of 14 species kept together for the time being until full revision of these species. As for other species, we propose (i) to move Rhabdastrella virgula to the genus Caminus, (ii) to reallocate four species of Rhabdastrella to the genus Geodia, and (iii) to move Jaspis coreana to the genus Rhabdastrella.
SN - 0024-4082
SN - 1096-3642
ER -