Lyreidus, De Haan, 1841

Pasini, Giovanni, Garassino, Alessandro & Sami, Marco, 2018, Decapod crustaceans from the late Pliocene (Piacenzian) nearby Faenza (Emilia-Romagna, N Italy), Natural History Sciences 5 (2), pp. 27-32 : 28-29

Lyreidus cf. L. paronae Crema, 1895

( Fig. 2A )

Note: Though Crema (1895) assigned the species paronae to Lyreidus , later Garassino et al. (2004), De Angeli et al. (2009), Baldanza et al. (2013), and Pasini et al. (2014) changed the systematic position of this species, assigning it to Lysirude . However, according to Karasawa et al. (2014) all reports of the species from Italy must be assigned to Lyreidus until the systematic controversy is solved.

Material and measurements: Two specimens in dorsal view, preserving chelipeds and incomplete ambulatory legs from Podere Tombarona ( MSF 2202 – lcxp: 15 mm; wcxp: 10 mm; – MSF 2203 – lcxp: 24 mm; wcxp: 15 mm); one complete specimen preserving chelipeds and incomplete ambulatory legs, in part and counterpart from Rio Albonello ( MSF 2240 – lcxp: 25 mm; wcxp: 16 mm) .

Description. Carapace – See De Angeli et al. (2009). Cheliped – Flat ovoid palm higher anteriorly, convex smooth upper margin and nearly straight lower margin; pointed index deflected downward and directed-upward distally; slender dacylus gently curved downward, with small, short, pointed teeth on occlusal margin; subrectangular carpus, with a rim of small teeth along the upper margin; rectangular merus, notably elongate, long twice the carpus.

Discussion. Though poor preserved, the studied specimens have the narrow orbito-frontal margin, with one strong extraorbital spine on both margins of rostrum and the possible presence of one spine on both anterolateral margins. These characters allow us to compare the specimens to Lyreidus paronae Crema, 1895 , already reported from the Tortonian (Miocene) of Sciolze and from the Langhian (Miocene) of S. Margherita (Torino, Piedmont) ( Crema, 1895), the Pliocene of Orta San Giulio (Novara, Piedmont) ( Garassino et al., 2004), the early Pleistocene of Poggio I Sodi and Poggi Gialli (Sinalunga, Tuscany) ( De Angeli et al., 2009; Baldanza et al., 2013, 2017) and Volterra (Pisa, Tuscany) (Pasini et al., 2014).

Remarks. The studied specimens seem to have an unusual granulation-ornamentation on the dorsal carapace and appendages. Unfortunately the poor preservation and compression of the carapace do not allow us to understand if this apparent granulation is part of the exocuticle or if it is only the structure of the endocuticle. Moreover the deformation of the anterolateral margins does not allow us to verify the presence of one or two lateral spines. Due to the absence of these diagnostic characters we prudentially compare the studied specimens to Lyreidus paronae . In other way the specimens could also pertain to a new indeterminate taxa.

Figures

Fig. 2 - A) Lyreidus cf. L. paronae Crema, 1895, MSF 2240 (x 2). B) Retropluma craverii (Crema, 1895), MSF 2233 (x 2.6).