Hanshessia, Thuy & Meyer, 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 : 123

Hanshessia sp.

Fig. 22 : 1-2

Material examined

GZG.INV.78641, GZG.INV.78642 and GZG.INV.78643 (dissociated LAPs) from the Callovian lower Chari Formation of Jumara (sample 95), India; GZG.INV.78644 (dissociated LAP) from the Callovian of Bauer-Wehrland, Germany.

Description

Moderately large, dissociated proximal to median LAPs; dorsally and ventrally fragmentary; originally at least twice higher than wide; distal edge convex; preserved portion of proximal edge nearly straight to slightly concave, with small, round, poorly defined, prominent and slightly protruding spur; outer surface with finely meshed stereom, no vertical striation. At least five very large, ear-shaped spine articulations in very shallow notches of strongly elevated distal portion of LAP; dorsal and ventral lobes of spine articulations merged into continuous, round volute; spine articulations proximally bordered by poorly defined, weakly prominent, undulose ridge; relatively large gap separating spine articulations and distal edge of LAP; dorsalward increase in size of spine articulations and of gaps separating them.

Inner side of LAPs largely obscured by sediment; large, sharply defined, prominent ridge composed of bent ventral part and straight, near-vertical dorsal part abruptly interrupted at some distance from dorsal edge of LAP; dorsal and ventral parts of ridge separated by kink devoid of conspicuous, ventroproximally pointing angle; inner side of distal edge of LAP with well-defined, round, slightly prominent spur composed of densely meshed stereom.

Remarks

Although, unfortunately, the limited available material is highly fragmentary, the specimens display sufficient morphological detail to allow them to be firmly assigned to Hanshessia on the basis of the shape of the ridge on the inner side and the shape and arrangement of the spine articulations. Similarities are closest with the LAPs of the type species, H. trochitophila . On the basis of the currently available material, however, it is impossible to decide whether the present specimens are conspecific with H. trochitophila or, instead, represent a new species.

Figures

Fig. 22. Lateral arm plates (LAPs) of fossil and Recent ophiacanthid brittle stars in external (a) and internal (b) views. 1-2. Hanshessia sp. from the Callovian (Middle Jurassic) of Jumara, India. 1. GZG. INV.78641, proximal to median LAP. 2. GZG.INV.78642, proximal LAP. 3-4. Ophiocopa spatula Lyman, 1883, Recent. 3. Proximal LAP. 4. Distal LAP. 5. Alternacantha? sp. from the late Pliensbachian (Early Jurassic) of Amellago, Morocco; GZG.INV.78645, proximal LAP. 6. Alternacantha sp. nov. innom. 1 from the middle Toarcian (Early Jurassic) of Le Clapier, France; GZG.INV.78647, proximal to median LAP. 7-8. Alternacantha occulta Thuy & Meyer, 2013, from the early Bajocian (Middle Jurassic) of Longwy, France. 7. GZG.INV.78648, proximal LAP. 8. GZG.INV.78649, distal LAP. 9-10. Alternacantha sp. nov. innom. 2 from the Callovian (Middle Jurassic) of Jumara, India. 9. GZG.INV.78652, proximal to median LAP. 10. GZG.INV.78653, median LAP. One common scale bar per species.