Molpadia Cuvier, 1817

Genus Molpadia Cuvier, 1817 View in CoL

Diagnosis. (following O’Loughlin et al., 2015, after Pawson, 1977). “Calcareous deposits include tables, anchors, and rosettes of racquet-shaped plates and large fusiform rods in various combinations. Tail deposits tables or fusiform rods. Phosphatic deposits present or absent.”

Remarks. Samyn and VandenSpiegel (2016) commented that there has been no complete revision of Molpadia since Pawson put Trochostoma and eight other genera into the group between 1965 and 1977. Pawson himself noted the ongoing issues with successfully splitting the loosely defined group into multiple genera, and the acceptance between taxonomists to maintain it for practical purposes, until more is known ( Pawson, 1977). There are 60 currently accepted species within Molpadia (WoRMS 2024) , with eight of these previously known from Australia: M. adamanensis , M. antarctica , M. dissimilis , M. scabrum , M. abyssicola , M. granulata , M. musculus and M. lenticula ( Rowe et al., 2017) , though there are some discrepancies between this list and genera recorded in ALA and in the NMV catalogue. Additional work will be needed to resolve the distribution discrepancies for the genus within Australia. In the IOT we found two lots of Molpadia , both from stations over 3700 m, which we have identified here as Molpadia cf blakei . Tri-radiate tables with a three-pillared spire, along with the presence of phosphatic deposits and lack of plate/cup ossicles, puts specimens into Molpadiidae rather than Caudinidae , while lack of three-armed anchor plates puts them in Molpadia rather than Heteromolpadia ( Pawson, 1977 key). Although we have a reduced dataset, both COI and 16S sequence data indicates that Molpadia is paraphyletic, which is concordant with previous findings ( Miller et al., 2017). Specific genetic placement of these IOT specimens is noted in Remarks for the species description below.