Hebertides jurassica Guinot, De Angeli & Garassino, 2007

Ossó, Àlex & Gagnaison, Cyril, 2019, An appraisal of the Middle-Late Miocene fossil decapod crustaceans of the ‘ Faluns’ (Anjou-Touraine, France), Geodiversitas 41 (9), pp. 367-383 : 372-373

Hebertides jurassica Guinot, De Angeli & Garassino, 2007 ( Fig. 3 F-J)

Hebertides jurassica Guinot, De Angeli & Garassino, 2007b: 241- 260 , fig. 1-3. — Van Bakel et al. 2009: 80. — Schweitzer et al. 2010: 104. — Taylor et al. 2012: 71-83, fig. 1; — Taylor 2012: 9-11, fig. 2. — Jagt et al. 2015: 882. — Emmerson 2017: 323.

Corystid – Guinot et al. 2007a: 53-55, fig. 1.

MATERIAL EXAMINED AND MEASUREMENTS (in mm). — Carapace, MS 2018-1-1: L = 16.5, W = 13, FOW = 13. — Fragment of carapace, ULB-SO-1: L = 11.4; W = 5.8.

LOCALITY AND HORIZON. — Carapace: ‘La carrière-musée’ (Channay-sur-Lathan, Indre-et-Loire). Bioclastic calcarenite with Anadara turonica, Tortonian (Late Miocene). Fragment of carapace: ‘La Sonneterie’ quarry, Meigné-le-Vicomte (Maine-et-Loire). ‘Savignean facies’, Langhian-Serravallian (Middle Miocene).

DESCRIPTION (modified from Guinot et al. 2007b) Carapace longitudinally ovate, longer than wide, convex in both sections; maximum width at the epibranchial teeth level; W/L ratio about 0.75. Cuticle well preserved. Regions relatively well defined, slightly swollen and separated by weak, smooth grooves; medial regions faintly distinct, forming a continuous medial area. Dorsal surface of carapace covered by rounded tubercles in anterior half, grouped and aligned in posterior half. Front narrow, broken, medially V-notched. Orbits broad; inner orbital tooth blunt, as a fold; supraorbital margin sinuous, finely serrated, with two V-shaped fissures; outer orbital tooth triangular, acute, prominent. Supraorbital area slightly depressed, smooth. Anterolateral margin convex, with three granular teeth (excluded the extraorbital one); the second sunken, placed at lower level that the rest; the third the larger; the fourth the smallest. Posterolateral margin slightly convex. Posterior margin convex, with marked granular rim. Protogastric regions slightly swollen, with two tubercles obliquely aligned at each lobe. Mesogastric region subpentagonal, slender and elongate anteriorly, broad posteriorly. Metagastric region indistinct from mesogastric region. Urogastric region subrectangular elongate, separated from meso-, metagastric regions by two gastric pits. Cardiac region subhexagonal, somewhat raised respect to urogastric region. Meta-, urogastric and cardiac regions, bounded laterally by well-marked branchiocardiac groove. Intestinal region indistinct. Hepatic region subtriangular, well delimited by cervical and hepatic groove. Branchial regions slightly swollen, epi- and mesobranchial lobes delimited by a weak oblique groove. Ventral parts and appendages not present.

REMARKS

Hebertides jurassica was erected based on a unique specimen found as a loose block in a quarry of Ranville (Normandy). In spite of the strikingly fine preservation of the specimen, its age was considered as the same as the rocks of the quarry, i.e., Bathonian (Middle Jurassic) ( Guinot et al. 2007a, b). Further examination of the matrix of this specimen revealed that the bryozoans (mainly cheilostomes) attached to the matrix and specimen were not Jurassic in age but younger, Cenozoic, and probably Miocene in age. Therefore, it was assumed that the specimen was accidentally discarded in the quarry by a fossil collector. Thus, the provenance of that specimen remained unknown (Taylor 2012; Taylor et al. 2012).

Despite this, complete specimens of Hebertides jurassica are known among French collectors’ private collections, which regularly collect in the ‘Faluns’ of Anjou-Touraine. Fragmentary remains of their carapaces are relatively common among the typical shell grit of the ‘Faluns’ ( Fig. 3 I-J). Therefore, the common occurrence of H. jurassica in the ‘Faluns’ leads us to suggest that, likely, the holotype comes from a locality in this region whose age is confirmed as Middle-Late Miocene.

Figures

FIG. 3. — A-C, Calappa praelata Lőrenthey in Lőrenthey & Beurlen, 1929, MS2006 FS 134a: A, dorsal view; B, frontal view; C, close-up of posterolateral margin; D, E, Calappa sp., MS2018-2-1: D, left chela, MS2018-2-2; E, right chela; F-J, Hebertides jurassica Guinot, De Angeli & Garassino, 2007; F-H, MS2018-1-1: F, right lateral view; G, frontal view; H, dorsal view; I, J, ULB-SO-1: I, fragment of right dorsal carapace; J, the same fragment showing bryozoans incrusted. Scale bars: A-H, 10 mm; I, J, 5 mm. Photographs by À. Ossó.