Ranina berglundi Squires & Demetrion, 1992

Pasini, Giovanni & Garassino, Alessandro, 2017, A preliminary review of the fossil species of Ranina Lamarck, 1801 (Decapoda, Brachyura, Raninidae), with systematic remarks, Natural History Sciences 4 (1), pp. 43-72 : 46-47

? Ranina berglundi Squires & Demetrion, 1992

Fig. 2

Ranina berglundi Squires & Demetrion, 1992: 43 , 44, figs. 128, 129.

Ranina berglundi - Schweitzer et al. 2006: 24, 27, 28, figs. 2.5, 2.6. – Vega et al. 2008: 54, Pl. 1, figs. 13- 15, Pl. 2, figs. 1, 2. – Schweitzer et al. 2010: 74. – De Angeli & Beschin 2011: 13. – Van Bakel et al. 2012: 208. – Karasawa et al. 2014: 260.

Type material: holotype, IGM 5913; paratype, IGM 5914.

Type locality: locality CSUN 1220b; Baja California Sur ( Mexico), Bateque Formation.

Geological age: early Eocene.

Examined material: holotype and paratype; three specimens (IHNFG-3013-3015) from the early Eocene (El Bosque Formation), locality El Veinte (Chiapas, Mexico), reported by Vega et al. (2008); one specimen ( MHN-UABCS /Ba7-3) from the middle Eocene (Bateque Formation), locality Waypoint 70 (26°45.918’N, 113°0.953’W) (Baja California Sur, Mexico), reported by Schweitzer et al. (2006).

Description by Squires & Demetrion (1992): “ Moderate-sized raninid with ovate, moderately convex carapace, very broad in proportion to its length; widest along anterior one-fifth at outermost anterolateral spine area; carapace maximum width (including outermost anterolateral spines) equals total length; carapace width (excluding outermost anterolateral spines) 80 percent of total length; lateral borders curve inward, posterior margin very narrow; surface with small pits, sparse on anterior middle part, closer posteriorly and toward lateral and anterior borders; posterolaterally, pits in transverse rows of about 10; rostrum trifid, small, and pointed; fronto-orbital margin curved with three spines on each side; first (innermost) fronto-orbital spine small, outward-pointing, and separated from wider second spine by a short furrow; second fronto-orbital spine separated from forward-pointing and more prominent third spine by a very short and narrow furrow; length of fronto-orbital area about 60 percent of width of carapace (excluding outermost anterolateral spines); two anterolateral spines, equally spaced; first anterolateral spine forward-pointing, about equal in size to outermost fronto-orbital spine, but more pointed; second (outermost) anterolateral spine widest and strongest of all spines, extended at a 45-degree angle to a blunt point, with four serrations on anterior edge of spine (the middle two the strongest); posteriorly to second anterolateral spine, a fine raised rim extends around the carapace; holotype 39 mm in width (including outermost anterolateral spines), 38 mm in length. ”

Discussion. The type material described by Squires & Demetrion (1992) has trifid rostrum, first anterolateral spine single and second anterolateral spine, strongly directed outward, with four spinules on anterior edge. Schweitzer et al. (2006) assigned six specimens from the Bateque Formation (Baja California Sur) to this species, without adding additional information appreciably to the description of the carapace made by Squires & Demetrion (1992). Later Vega et al. (2008) assigned tentatively three specimens from Chiapas ( Mexico) to this species, pointing out, as difference from the type material, the first anterolateral spine bifid, small size, and distribution of the carapace dorsal pits. However, the review of the type material described by Squires & Demetrion (1992) allow us to establish that the first anterolateral spine is also bifid, well preserved in the left side of the holotype and slightly broken in the paratype, attesting that the specimens from Baja California Sur (holotype and paratype described by Squires & Demetrion, 1992) and Chiapas ( Schweitzer et al., 2006) could belong to the same species, though the smaller size of Chiapas specimens could be a diagnostic characters to distinguish these specimens from the type material (F.J. Vega pers. comm., 2016).

Based upon the main morphological characters of R. berglundi , such as the trifid rostrum and the peculiar shape and arrangement of the anterolateral spines (above all the second one), we can attest that these characters do not fit those of Ranina , questioning the placement of berglundi within this genus.

Indeed R. berglundi from the early Eocene of Mexico and the rich sample of specimens from the late Oligocene (Rupelian) of the Ligure-Piemontese Basin ( NW Italy) ascribed to R. speciosa by Allasinaz (1987) have been assigned to a new genus within the Raninindae sensu stricto ( Pasini & Garassino, 2017).

Figures

Fig. 2 -?Ranina berglundi Squires & Demetrion, 1992. A) holotype, IGM 5913 (x 1.8). B) paratype, IGM 5914 (x 4.5).