Geromura, Thuy, 2013

Thuy, Ben, 2013, Temporary expansion to shelf depths rather than an onshore-offshore trend: the shallow-water rise and demise of the modern deep-sea brittle star family Ophiacanthidae (Echinodermata: Ophiuroidea), European Journal of Taxonomy 48, pp. 1-242 : 73

Genus Geromura gen. nov.

urn:lsid:zoobank.org:act:10BE3FAB-5984-4759-8DF1-172F60DE98CA

Type species

Geromura teckliformis sp. nov., by present designation.

Other species included

Geromura touertensis sp. nov.

Diagnosis

Ophiacanthid genus with relatively small and extremely elongate LAPs, proximal ones at least twice wider than high; well-developed constriction; relatively small spine articulations of rugged appearance, freestanding on slightly elevated distal part of LAP; very large tentacle notch; two separate knobs on inner side at least in median to distal LAPs.

Etymology

Genus named in honour of Gero Moosleitner, who introduced me to the spectacular site at the Glasenbach Gorge near Salzburg, Austria, and who generously provided a major part of the samples used in this study, including those yielding the original material of the type species of the genus; from oura, Greek for “tail”, a commonly used suffix for ophiuroid names, gender feminine.

Remarks

The Mesozoic ophiuroid fossil record includes a highly peculiar type of dissociated LAPs which is characterised by its extraordinary width. In fact, even proximal LAPs of the type in question are more than twice wider than high, a ratio which, in most other ophiuroid lineages, is only found in the very distalmost LAPs. Other distinctive characters of such LAP type are the relatively small, freestanding, ear-shaped spine articulations composed of irregular, rough dorsal and ventral lobes, a very large tentacle notch implying a large tentacle pore as defined by Thuy et al. (2012), a strong constriction, and two separate knobs on the inner side at least of the median to distal LAPs. The last-named character precludes confusion with the LAPs of Lapidaster gen. nov. and Ophiologimus , which share the greatest similarities with the LAP type in question. A new genus, Geromura gen. nov., is therefore introduced here to accommodate the peculiar type of LAPs in question. In spite of their rugged and rather atypical appearance, the spine articulations of Geromura gen. nov. display a sigmoidal fold, which unambiguously places them in the Ophiacanthidae .

The phylogenetic position of Geromura gen. nov. remains elusive as long as no articulated specimens are known on the basis of which a complete character analysis could be performed. It is very likely, however, that it shares greatest phylogenetic ties with the other large-pores lineages, in particular the Lapidaster - Ophiologimus lineage (see above) as suggested by the close similarities in LAP morphology. Interestingly, Geromura gen. nov. is currently known exclusively from deep-water deposits.