Bucculentum horstkuscheli, 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

Bucculentum horstkuscheli , n. sp.

Fig. 1E, F , 6

Diagnosis. Hepatic regions large, much wider than metabranchial regions; metabranchial region not expanded laterally; augenrest directed laterad at c. 60 o to body long axis and aligned with proximal portions of hepatic region; suborbital spine wide, directed outwards and downwards, and ending in two short, triangular teeth; cardiac region with one distalmost dominant tubercle accompanied anteriorly by row of small tubercles.

Etymology. Trivial name is dedicated to Horst Kuschel (Faurndau), who found and donated the holotype of this species.

Material examined. Holotype: # SMNS 70607 (leg. H. Kuschel), Germany: Bad Überkingen-Oberböhringen, near Geislingen a. d. Steige. Age : Late Kimmeridgian: Acanthicum Zone ( Fraaije et al. 2017).

Description. The holotype represents an internal mould, with only the traces of the white cuticle in the grooves. It is excellently preserved and symmetrical, lacking only the rostrum. The hepatic regions are very wide, c. 1.4x wider than the mesobranchial region and 1.2x wider than the metabranchial region. The frontal portions containing the augenrests and anterior portions of hepatic regions are aligned, obliquely set to the long axis at an angle of 57 o, symmetrical on both sides. Augenrests are almost perpendicular to the plane of carapace, only very slightly shifted dorsally ( Fig. 6B ), at an angle of c. 80 o to the upper surface of the carapace; they are laterally flanked by single, broad, triangular tubercles. The suborbital spine is very broad, supporting most of the lower margin of the augenrest, directed down- and outwards, and terminating in two short, triangular teeth ( Fig. 6B, C , arrows). The epibranchial region is narrow; the cervical groove is almost straight. The cardiac region is equipped at its distal end with a large tubercle (which is the highest point of the carapace) and a median row of small tubercles towards the mesobranchial region. The metabranchial regions are narrow, almost rectangular; the distal end is broad, stretched over the entire distal portion of the metabranchial region and upturned.

Remarks. The new species resembles B. bachmayeri in having a large hepatic region, a divided suborbital spine, and a cardiac region with one large tubercle, but differs in having the augenrests directed outwards and positioned obliquely to body long axis. The suborbital spine is divided into two short, triangular lobes, unlike the long, thin prongs in B. bachmayeri .

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 6. Bucculentum horstkuscheli n. sp., holotype SMNS 70607, Bad Überkingen-Oberböhringen, Upper Kimmeridgian. A, dorsal view; area of augenrest is between the arrows and is aligned with outline of hepatic region. B–C, two views of suborbital spine (arrows); note its various appearance. D, lateral view (most prominent tubercle of cardiac region is marked). Bars 1 mm.