Bucculentum plettenbergense, Krzemińska & Starzyk & Fraaije & Schweigert & Lukeneder, 2021

Krzemińska, Ewa, Starzyk, Natalia, Fraaije, René H. B., Schweigert, Günter & Lukeneder, Alexander, 2021, Jurassic brachyurans of the genus Bucculentum, Zootaxa 5032 (3), pp. 395-410 : 402-403

Bucculentum plettenbergense , n. sp.

Fig. 1G , 7

Diagnosis. Metabranchial region large, more than half as long as carapace, and a little wider than hepatic region; augenrest round, slightly concave, shifted more dorsally than in other species of genus, and flanked laterally by long, crescent ridge; suborbital spine undivided, curved upwards; epibranchial region very narrow.

Etymology. The new species is named after its type locality.

Material examined. Holotype MAB 3576, Germany: Plettenberg quarry n. Balingen (N 48 o 21’, E 8 o 80’), coll. RHB Fraaije, Late Oxfordian: Planula Zone ( Schweigert & Callomon 1997; Jantschke & Schweigert 2020).

Description. The carapace is 8.43 mm long. The rostrum and centro-anterior portion have been split off. Left augenrest complete, large, round, shifted to dorsal side at an angle c. 50 o to the surface of carapace and delimited laterally by a narrow, crescent-like ridge. The suborbital spine is directed upwards ( Fig. 7A, B , arrows). The epibranchial region is very narrow (less than 10% of the total lateral length of carapace), with two symmetric swellings over the cardiac region. The cardiac region has three tubercles arranged axially, the distalmost one being the largest, and also the highest point of the carapace. The metabranchial region is characteristically large, a little bit wider than the hepatic region, and more than half as long as the carapace.

Remarks. Bucculentum plettenbergense , n. sp., is distinguished because of having the largest metabranchial region amongst all bucculentids, combined with the narrowest epibranchial region. Such proportions are not met in any other congener.

Figures

FIGURE 1. Nomenclature of carapace and ground plans of species of Bucculentum: A, B, Bucculentum bucculentum (dorsal and frontal view, respectively); C, D, Bucculentum bachmayeri (dorsal and frontal view, resp.); E, F, Bucculentum horstkuscheli, n. sp. (dorsal and frontal view, resp.); G, Bucculentum plettenbergense, n. sp., dorsal view (a, augenrest; ag, augenrest groove; bcg, branchio-cardiac groove; c, cardiac region; cg, cervical groove; h, hepatic region; ebr, epibranchial region; mbr, metabranchial region; mg, mesogastric region; msbr, mesobranchial region; pcg, postcervical groove; s, suborbital spine).

FIGURE 7. Bucculentum plettenbergense, n. sp., holotype MAB 3576, Plettenberg quarry (Lower Kimmeridgian). A, dorsal view; B, lateral view (suborbital spine is arrowed). Bars 1 mm.