Bucculentum bucculentum ( Wehner, 1988 )

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 : 396-400

Bucculentum bucculentum ( Wehner, 1988)

Fig. 1A, B , 2 , 3

1988 Nodoprosopon bucculentum Wehner , p. 53, pl. 4, figs. 1–2, 6.

2009 Bucculentum bucculentum ( Wehner, 1988) in: Schweitzer & Feldmann, 2009a: p. 79, fig. 3.3–3.4.

Diagnosis. After Schweitzer & Feldmann (2009), amended. Carapace from longer than wide to almost quadrangular, widest across hepatic regions; rostrum tri-lobed, armoured with spines, central lobe being longest and depressed; augenrest positioned perpendicular to body long axis, laterally flanked by short ridge; suborbital spine strong, single, with several sharp terminal spines; cardiac region with three tubercles arranged along body long axis, distalmost tubercle being largest.

Age and distribution. From at least Middle Oxfordian ( Poland) to Early Kimmeridgian: Platynota-Divisum zones ( Germany); the specimen SMNS 66654 described here as „ Bucculentum cf. bucculentum ” would extend the range of this species to the Late Kimmeridgian Pseudomutabilis Zone.

Materials examined. Holotype SNS̲-̲SPG 1980 XXX 1255 ( Fig. 2A, B ), Biburg ( Germany), age Early Kimmeridgian: Planula Zone ( Schairer 1982; Schweitzer & Feldmann 2009a). Paratype SNS̲-̲SPG 1980 XXX 1254 ( Fig. 2C ), same locality and age. Specimen SNS̲-̲SPG 1987 I 55 ( Fig. 2D, E ), Unterwilflingen ( Germany), age Early Kimmeridgian: Platynota-Divisum zones ( Wehner 1988). Specimens from the Polish Jura Chain described and illustrated by Starzyk et al. (2012) were re-examined for this study; they come from two quarries: Ogrodzieniec (Lower and Middle Oxfordian) and Niegowonice (from Cordatum to Transversarium zones, except discontinuous Mariae Zone; Głowniak 2006).

New material: MAB 3572 ( Fig. 3 E, F ), Geisingen ( Germany; N 47 o 93’, E 8 o 67’), age Late Kimmeridgian: Mutabilis/Acanthicum Zone (Van Bakel et al. 2008); MAB 3577, MAB 3579 ( Fig. 3G ), MAB 3582a (positive, Fig. 3A ) and MAB 3582b (negative, Fig. 3B, C, D ), Plettenberg quarry n. Balingen, Germany; all coll. R. H. B. Fraaije), age Early Kimmeridgian, Planula Zone ( Schweigert & Callomon 1997; Jantschke & Schweigert 2020); I-F/MP/6210/1578/11 ( ISEA) and I-F/MP/4648/1534/08 ( ISEA), Wysoka n. Łazy (N 50 o 25’44’’, E 19 o 21’13’’), Polish Jura Chain, age Middle Oxfordian ( Głowniak 2002).

Additional description. The rostrum is tri-lobed, the central lobe being the longest and directed downwards while the two flanking lobes are raised; together, they form a kind of a scoop armoured with terminal rows of sharp spines. The entire rostrum, or almost so, is preserved only in the specimens MAB 3572 from Plettenberg and I-F/ MP/6210/1578/11 from Poland ( Fig. 3E, H , respectively), but it is fragmentarily present in several other specimens, including the holotype ( Fig. 2A, B ) and specimen SNSB-BSPG 1987 I 55 ( Fig. 2D, E ). The augenrest is convex and directed frontally, i.e, at an angle c. 90 o to the body long axis. The suborbital spine is single, massive, and oval in cross section. The distal portion of this spine is armoured with few teeth (traces of four teeth are visible in two specimens, Fig. 2B and 3G ). The epibranchial region of the holotype ( Fig. 2A ) and MAB 3572 has six ridges ending in rows of tubercles, fan-like spreading just over the cardiac region; in other specimens this feature is weakly expressed or absent. Along the lateral sides there are strong spines ( Fig. 3D, F, G ).

Remarks. Noteworthy is the specimen MAB 3852, preserved in positive (convex) and negative (concave) parts ( Fig. 3A, B , resp.), which supplement each other with details; the concave mould of the rostrum with white depressions left by the warts is completely preserved in the negative part ( Fig. 3C ); this part retained also the traces of lateral spines along the metabranchial region ( Fig. 3D ), and almost complete cover of white cuticle, visible from the inner side. The specimen MAB 3572 ( Fig. 3F ) shows that the pattern of tubercles is preserved both on the cuticle and on the surface of the mould beneath.

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 2. Bucculentum bucculentum, type material.A–B, holotype # SNSB-BSPG 1980 XXX 1255: dorsal view (A), frontal view (B); C, paratype SNSB-BSPG 1980 XXX 1254; D, E, specimen SNSB-BSPG 1987 I 55. Bars 1 mm.

FIGURE 3. Bucculentum bucculentum, cont. A–D, MAB 3582: A, positive; B, negative (arrow, end of rostrum); C, negative of rostrum magnified (note white traces of tubercles on surface); D, traces of lateral spines. E–F, MAB 3572 (Geisingen, lower Upper Kimmeridgian): E, rostrum (note three lobes surrounded with spines); F, habitus. G, MAB 3579 (Plettenberg quarry, Lower Kimmeridgian), frontal portion (note lateral spines on hepatic margin). H, F/MP/6210/1578/11 (Poland, Wysoka, Oxfordian), frontal portion. Bars 1 mm.