Ophiotreta Verrill 1899
Creators: name: Thuy, Ben
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Ophiuroidea
Ophiurida
Ophiacanthidae
Ophiotreta

description: Ophiotreta sp. nov. innom. 2
Fig. 18: 1-2
Material examined
NHMW 2012/0139/0001 and NHMW 2012/0139/0002 (4 dissociated LAPs) from the Langhian, middle Miocene, of Mannersdorf, Austria; NHMW 2012/0139/0003 (dissociated LAP) from the Langhian of Stotzing, Austria.
Description
Small dissociated LAPs, proximal ones nearly twice higher than wide, median ones slightly higher than wide; dorsal edge straight to very weakly concave; distal edge convex; proximal edge slightly concave, devoid of spurs; outer surface with very narrow band of fine, regular vertical striation composed of few fine lamellae close to spine articulations, replaced by finely meshed stereom on majority of outer surface. Up to six large, ear-shaped spine articulations freestanding on elevated ridge of distal portion of LAP, proximally bordered by slightly (proximal LAPs) to strongly (median LAPs) undulose distalmost lamella; dorsal lobe of spine articulation much larger than ventral one, separated from the latter by small, shallow notch; ventral notch with short, weakly (proximal LAPs) to moderately well-developed (median LAPs) connecting ridge with distalmost lamella; very weak dorsalward increase in size of spine articulations and of gaps separating them. Tentacle notch not visible in external view.
Inner side of LAPs with large, conspicuous, sharply defined and prominent ridge composed of straight, near-vertical dorsal part very close to proximal edge of LAP, and straight, oblique slightly shorter and wider ventral part with slightly widened, round ventral tip; dorsal and ventral parts of ridge separated by angular kink with ventro-proximally pointing angle; no ventral knob discernible; inner side of tentacle notch moderately large. Shallow, moderately well-defined vertical furrow with medium-sized, irregular perforations dorsally bordering inner side of tentacle notch.
Remarks
The highly distinctive shape of the ridge on the inner side along with the arrangement of the spine articulations and the moderately well-developed connecting ridge between the spine articulations and the outer surface leave no doubt as to the assignment of these LAPs to Ophiotreta. Closest similarities are shared with the LAPs of Ophiotreta hedone sp. nov. on account of the small size and the low number of spine articulations. The present specimens, however, differ in having a much shorter ventral portion and up to six, rather than five, spine articulations. All extant species of Ophiotreta have much larger LAPs with numerous spine articulations. Thus, it seems highly probable that the present LAPs represent a new species. I refrain from formally describing this new species here, however, since it is currently represented by a few plates only, most of which are fragmentary. With such limited material available, it cannot be ruled out that the LAPs in question are from juvenile individuals rather than small-sized adults.
description: Published as part of 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), pp. 1-242 in European Journal of Taxonomy 48 on page 94, DOI: 10.5852/ejt.2013.48, http://zenodo.org/record/3822836