Pilumnus mediterraneus ( Lőrenthey, 1897 )

Ossó, Àlex, Gagnaison, Cyril & Gain, Olivier, 2022, A re-appraisal of the middle-late Miocene fossil decapod crustaceans of the ‘ Faluns’ (Anjou-Touraine, France), Geodiversitas 44 (6), pp. 207-228 : 217-218

Pilumnus mediterraneus ( Lőrenthey, 1897)

( Fig. 5F-K )

Pilodius mediterraneus Lőrenthey, 1897: 160 , 167, 169; 1898a: 105, 113, 115; 1898b: 126-129, pl. 8, figs 5, 6; 1898c: 99-101, pl. 8, figs 5, 6. — Glaessner 1929: 315.

Pilumnus sp. – Glaessner 1928: 190.

Chlorodopsis mediterraneus – Lőrenthey in Lőrenthey & Beurlen 1929: 34, 225-227, pl. 12, figs 13-17, 19.

Chlorodopsis mediterranea – Bachmayer 1953a: 253, pl. 3, fig. 5. — Bachmayer & Tollmann 1953: 314.

‘ Pilodius ’ mediterraneus – Müller 1974a: 122, pl. 3, fig. 3.

Pilumnus mediterraneus – Müller 1974b: 280; 1976a: 510; 1976b: 152; 1979: 274, pl. 21, fig. 3; 1984: 93, 94, pl. 87, figs 2-5, pl. 88, figs 1-5. — Radwański et al. 2006: 96, pl. 2, fig. 7. — Ossó & Stalennuy 2011: 37, fig. 9.3. — Górka et al. 2012: 171. — Górka in Wysocka et al. 2016: 379, fig. 14E. — Ossó & Gagnaison 2019: 373, 374, fig. 4G-L . — Hyžný & Dulai 2021: 192-194, fig.73.1-6.

Pilumnus sp. – Förster 1979: 260-261, pl. 3, fig. 6, pl. 5, fig. 1, 3, text-figs 8, 9.

Pince d’une patte de crabe – Gagnaison et al. 2009: 1, fig. 3.

Pilumnus cfr. P. mediterraneus – De Angeli et al. 2011: 112, fig. 4.

MATERIAL EXAMINED AND MEASUREMENTS (in mm). — Six complete dorsal carapaces with cuticle well preserved, ULB-IV-A (4) L = 8, W = 9, FOW = 7; ULB-IV-A (8): L = 6.5, W = 8, 8, FOW = 6.5; ULB-IV-A (14): L = 11, W = 14.5, FOW = 10.5; ULB-IV-A (18): L = 8.5, W = 11, FOW = 8; ULB-IV-A (37): L = 10, W = 13, FOW = 11; ULB-IV-A (38): L = 7.5, W = 9.5, FOW = 7. —Two right chelae, ULB-IV-A (39): L = 12.5, H = 6; ULB-IV-A (40): L = 11, H = 7. — One left chela, ULB-IV-A (20): L = 25.5, H = 11.5, T = 7.

LOCALITY AND HORIZON. — ‘Blandinerie’ quarry, Breil (Maine-et-Loire). ‘Savignean facies’, Langhian (middle Miocene).

DESCRIPTION

Carapace relatively small, subhexagonal, longitudinally vaulted anteriorly, regions faintly marked; surface smooth, weakly ornate with small acute granules and small clusters of acute granules of squamous aspect, spread mainly by anterior half of carapace; setal pits visible. Maximum width at level of fourth anterolateral tooth, at the anterior half of carapace. Front bilobed, medially notched, each half with inner lobes very wide, and the outer lobes smaller, and separated from the inner orbital angle by notches. Orbits small, subrectangular, complete, forward directed; supraorbital margin finely serrate, with two fissures, one median and a second close to outer orbital tooth. Anterolateral margin with four subtriangular teeth (excluding outer orbital tooth), the first one semifused with the outer orbital one, the second one broad, the third and fourth acute. Posterolateral margin slightly convex, smooth. Posterior margin clearly convex medially, rimmed.Frontal region with a short, longitudinal deep groove, lobes slightly swollen. Gastric process fairly defined. Epigastric lobes faintly swollen, ornate. Protogastric lobes rounded, swollen, faintly ornate. Mesogastric region subpentagonal elongate anteriorly, wider posteriorly. Metagastric region indistinct. Urogastric region slightly depressed and separated from meso- and metagastric lobes by two gastric pits. Cardiac region diamond shaped, weakly swollen. Intestinal region narrow, transversely elongate, faintly swollen laterally. Hepatic region with a short granulate ridge paralleling the anterolateral margin. Epibranchial region with a short, acute, half-moon ridge not reaching the fourth (epibranchial) anterolateral tooth. Meso- and metabranchial regions indistinct, swollen. Gastrohepatic groove well marked; cervical and branchiocardiac grooves slightly marked. Thoracic and pleonal features not preserved. Right chela stout, palm slightly wider than high, outer side smooth, spiny in the upper margin and the distal portion of palm, mainly in smaller individuals; articulation with the dactylus strong; dactyli stout, about one third of chela length; dactylus curved with blunt teeth in occlusal margin; index strong, with three to four massive acute teeth in the occlusal margin; setal pits visible in both dactyli. Carpus stout, angle of upper and outer surface with scattered spiny tubercles; upper inner angle with prominent tooth.

REMARKS

As pointed out by Ossó & Gagnaison (2019: 380), the decapods population of the ‘Faluns’ appears clearly dominated by Pilumnus mediterraneus , as the new collection of decapods from the ‘Blandinerie’ quarry also confirms. This species, represented usually by undetermined cheliped remains in the ‘Faluns’ outcrops, was confirmed as such by the report of two complete dorsal carapaces ( Ossó & Gagnaison 2019: 373- 374, figs 4G-J). In the same text, the authors suggested that the type of Haydnella pulchellus, figured in A.Milne-Edwards (1863: pl. 9, figs 2, 2a, as Titanocarcinus pulchellus) was likely a specimen of P. mediterraneus , based upon the drawings of the holotype, which is lost (see Couffon 1908: 1), and on the description of it (see A. Milne-Edwards 1864: 33, 34). A careful reading of the French text of the description, reveals details such as: “ La surface est ornée, sur toutes ses parties, de petites granulations, qui sont plus nombreuses près des bords [...] Les régions branchiales sont décomposées en leurs lobes antérieurs, moyens et postérieurs, par des sillons peu profonds ”(The surface is adorned in all its parts with small granulations, which are more numerous near the edges [...] The branchial regions are decomposed into their anterior, middle and posterior lobes, by shallow furrows), characters that are more typical, for instance, of Xantho moldavicus , whose presence in the ‘Faluns’ is confirmed herein (see below), rather than of Pilumnus mediterraneus . Thus, it is plausible that the holotype was in fact, a small sample either of Pilumnus mediterraneus or Xantho moldavicus instead of a third species. In any case, the continuity of Haydnella pulchellus as a valid taxon, based on a lost holotype and two schematic drawings, appears problematic now, and should be considered as nomen nudum.

Figures

FIG. 5. — Decapods from the ‘Savignean facies’ (Langhian) of the ‘Blandinerie’ quarry,Breil (Maine-et-Loire):A, indeterminate majoid,ULB-IV-A (26): dorsal view;B-E, Derilambrus cf.szaboi (Müller,1974):B, ULB-IV-A (33),right propodus,outer margin;C, inner margin;D, ULB-IV-A (35),right propodus,outer margin;E, right propodus, inner margin;F-K, Pilumnus mediterraneus (Lőrenthey, 1897):F, ULB-IV-A (14),dorsal view;G, frontal view;H, ULB-IV-A (18),dorsal view;I, frontal view;J, ULB-IV-A (20), left chela,outer margin;K, inner margin;L-M, undeterminated Carcinidae:L, ULB-IV-A (52),right chela;M, ULB-IV-A (50) left chela;N-Q, Liocarcinus kuehni (Bachmayer, 1953a):N, ULB-IV-A (10),dorsal view;O, frontal view;P, ULB-IV-A (13), dorsal view;Q, frontal view.Scale bars:A-I, N-Q, 5 mm;J-M, 10 mm. Photographs by À. Ossó.