Goneplax gulderi Bachmayer, 1953

Charbonnier, Sylvain, Garassino, Alessandro, Pasini, Giovanni & Chény, Cédric, 2024, Review of brachyuran crabs from the late Miocene (Messinian) of Oran, Algeria, Geodiversitas 46 (2), pp. 13-29 : 27

Goneplax gulderi Bachmayer, 1953

( Fig. 7 D-F)

Goneplax gulderi Bachmayer, 1953: 143 , 144, pl. 9, figs. 1-3. — Müller 1984: 96, pl. 93, figs. 2-3. — Müller 1993: 23, fig. 11 K. — Mayoral et al. 1998: 508, 509, fig. 2 (5). — Müller 1998: 38. — Garassino & De Angeli 2004: 45. — De Angeli & Garassino 2006: 65. — Castro 2007: 686. — De Angeli et al. 2009: 187, 188, 189, fig. 18 A, B. — Schweitzer et al. 2010: 135. — Garassino et al. 2012: 46, 47; 2013: 357, 359, fig. 1a. — Pasini & Garassino 2013: 321, 322.

Goneplax cf. saccoi [sic] – Vía 1948: 146, fig. 6. — Solé & Vía 1989: 34.

Goneplax cf. gulderi – Müller 1979: 6. — Pasini et al. 2019: 36, fig. 3c. — Pasini et al. 2020: 52, fig. 3a.

EXAMINED MATERIAL. — MNHN.F.A57344 , A57347 (Geslin coll.) from the late Messinian of Ravin Blanc quarry , between Es Seddikia and El Makkari districts, Oran .

DESCRIPTION

Carapace

Carapace transversely subtrapezoidal, slightly wider than long, widest at anterolateral spine; front straight; front as wide as orbits; relatively wide orbits; outer-orbital angle with triangular, acute spine; short anterolateral margins slightly narrowing frontally; reduced anterolateral spine; posterolateral margins narrowing posteriorly; straight posterior margin; smooth dorsal surface of carapace, with two raised transverse ridges; regions scarcely evident.

Cephalic appendages

Eyestalk elongate and narrow, as long as the orbit.

Thoracic appendages

Short P1; rounded P1 carpus with one inner distal spine; P1 palm poorly preserved; elongate flat P2-P5.

DISCUSSION

Bachmayer (1953) described Goneplax gulderi based on one complete carapace, decorticated and poorly preserved, and one isolated dactylus. Later, De Angeli et al. (2009) referred some best-preserved specimens from the Miocene of Tuscany to this species. These additional specimens allowed for the first time to highlight the main diagnostic characters of this species. Finally, Garassino et al. (2013: 357) provided an emended diagnosis, confirming the original description and the updated data by Müller (1993) who pointed out that G. gulderi differs from the type species in having two well-marked transverse carinae on the wider than long carapace and especially for the anterior margin where each orbit is as wide as the front (versus orbits wider than front in the type species). The two studied specimens share the main morphological characters of G. gulderi , such as the straight front as wide as orbits; the outer-orbital angle with triangular, acute spine; short anterolateral margins; reduced anterolateral spine; posterolateral margins narrowing posteriorly; straight posterior margin; and smooth dorsal carapace, with two raised transverse carinae.

Goneplax gulderi was previously reported from the Miocene of Austria (Baden) ( Bachmayer, 1953) and Miocene and Pliocene of Italy (Tuscany, Emilia-Romagna) ( Pasini et al. 2019, 2020). Its first report in North Africa enlarges its palaeobiogeographic range around the Proto-Mediterranean Basin.

Figures

FIG. 7. — A-C, Chlinocephalus demissifrons Ristori, 1886 from the late Messinian of Oran (Ravin Blanc quarry, Geslin coll.): A, B, MNHN.F.A87800, dorsal and frontal views; C, MNHN.F.A57345, dorsal view; D-F, Goneplax gulderi Bachmayer, 1953 from the late Messinian of Oran (Ravin Blanc quarry, Geslin coll.); D, E, MNHN.F.A.57347, dorsal and frontal views; F, MNHN.F.A.57344, dorsal view. Scale bars: 1 cm. Photographs: Lilian Cazes.