Undetermined undetermined, Macleay, 1838, Macleay, 1838

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 : 218-219

Subfamily and genus indeterminate

( Fig. 5L, M )

MATERIAL EXAMINED AND MEASUREMENTS (in mm). — One right chela, ULB-IV-A (52): L = 30; H = 16; T = 11. — One left chela, ULB-IV-A (50): L = 20; H = 10.5; T = 6.5.

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

DESCRIPTION

Palm stout, subtrapezoidal, longer than high, higher distally; subhexagonal elongate in cross section; surface coarsely granulate; upper margin straight, flattened, with keeled lateral angles, scar of spinule at inner distal corner, over the dactylus insertion; outer margin convex, with two transverse keels, one at halfway up of palm, the second below, near the lower margin and continues along the index; inner margin convex medially, with two transverse weak keels; lower margin slightly convex, flattened, rounded lateral angles. Index straight, slightly concave proximally, keeled, occlusal margin with serial conical teeth.

REMARKS

The two chelae described herein exhibit the typical long and keeled ‘portunid’ shape, but no ‘portunid’ carapace to which they can be related has been found in the ‘Faluns’. Strictly, although both chelae possess very similar construction and ornamentation, we cannot affirm that they are conspecific. Despite this, the absence of spines in their upper margin, mainly at the proximal articulation with carpus, discards their affinities with Portunidae s.s. ( Spiridonov et al. 2014: 423). Nevertheless, the general shape of that chelae, shorter as in Portunidae , and the ”lacking spines except for a distal spinule on upper face of manus”, exactly in the inner distal corner over the dactylus insertion, is characteristic for the Carcinidae , and for at that time considered full family Polybiidae , now subfamily of Carcinidae ( Spiridonov et al. 2014: 422) .

In view of the aforementioned, we assign both chelae to Carcinidae , which in fact, as seen below, has representatives in the ‘Faluns’ such as Liocarcinus spp. , albeit the small size of the specimens available prevent us from relating them at a generic or specific level with confidence.

The two fragments of dactyli attributed byCouffon (1908: 2, pl. 1, fig. 5) to Neptunus aff. monspeliensis A. Milne-Edwards, 1861 (sic), could likely belong to the chelae of Carcinidae species such as the described herein.

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.