Ranina americana Withers, 1924

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 : 44-45

? Ranina americana Withers, 1924

Fig. 1

Ranina americana Withers, 1924: 125-127 , Pl. 4, figs. 1-3.

Ranina americana - Rathbun 1926: 91, Pl. 23, figs. 1-4. – Glaessner 1929: 360. – De Angeli et al. 2009: 120. – Waugh et al. 2009: 20, Tab. 1 . – Schweitzer et al. 2010: 74. – De Angeli & Beschin 2011: 13. – Van Bakel et al. 2012: 208. – Karasawa et al. 2014: 260.

Hela americana - Lőrenthey in Lőrenthey & Beurlen 1929: 109.

Type material: holotype, NHM 23798.

Type locality: Clallam Bay , south shore of Strait of Juan de Fuca , Washington State, USA; Blakeley Formation, Late Oligocene .

Geological age: Late Oligocene.

Examined material: holotype; 4 specimens reported by Rathbun (1926) from the middle Eocene Hoko River Formation , Washington State, USA (Stanford University, N. Pac. 167) ; 3 specimens reported by Karasawa et al. (2014), KSU D675-678, from the the middle Eocene Hoko River Formation , Washington State, USA .

Description by Whiters (1924): “ Cephalothorax elongate-ovoid, moderately convex transversely, width of orbito-frontal margin about equal to half that of the carapace; length, imperfect, 60 mm; breadth 48 mm; anterolateral margins with three large lobes, very narrowly and deeply separated; the anterior lobe on the left side is the only one preserved entire, and this has a broadly rounded margin; the middle lobe is of about the same width, but evidently projected beyond the others; the third and posterior lobe being small and projected only to a small extent; the postero-lateral margins converge posteriorly, are slightly raised to form a rim, which is weakly serrated above; the orbito-frontal margins broken away, but on the right side is an impression of the eye-stalk and on the left the eye-stalk itself; outer surface smooth except on the sides of the anterior half of the carapace, where there are semicircular incisione, behind which the surface is raised and the edges slightly toothed; these markings are somewhat coarser anteriorly; on the inner surface only the anterior half of the specimen is preserved, and the pterygostomian plates, the third maxillipedes, and the first sternal plate are displaced; pterygostomian plates extremely convex, with the sides bordering the buccal cavità slightly excavated, and below there is a small rounded excavation for the basal joint of the third maxillipedes; the inner half of the surface is smooth and minutely pitted, and the outer half is coarsely ornamented with raised scale-like markings, toothed on the anterior edge, and these markings become more closely disposed towards the outer margin; third maxillipedes much elongated; first sternite widely trifid, with the outer lobes widely rounded, wider than the middle lobeor episternum; the sides curve downward and become subparallel; surface of first scernite marked by a number of pits, forming an almost symmetrical pattern; episternum with the anterior margins forming an obtuse angle and the posterior margins slightly inclined outwards; branchiostergite with the buccal margin sinuous, obliquely inclined outwards, and the margin adjoining the pterygostomian plate bordered by a close line of pits; the middle of the plate is raised to form a ridge, steep-sided and somewhat concave on the outer side, where there are a number of corse but small scale-like markings; a few similar, but smaller, markings are situated near to the buccal margin. ”

Discussion. Withers (1924) described R. americana from the late Oligocene Blakeley Formation of Clallam Bay, Washington State, USA, based upon a single poorly preserved specimen lacking the frontal margin and the anterolateral spines, the main characters useful for a specific assignment. The correct locality where this specimen was collected is unknown except for Clallam Bay which has exposures from Upper Oligocene to Lower Miocene Clallam Formation ( Arnold, 1906; Addicott, 1976; Prothero & Burns, 2001). The Blakeley Formation is limited to exposures west of Seattle, Washington ( Prothero & Nesbitt, 2008). This is the only report of a Ranina crab coming from this formation and area. The sole specimen lacks enough diagnostic characters for assignment to specific level. In conclusion the inability to recognize the diagnostic characters of Ranina questions the placement of americana within this genus.

Rathbun (1926: 91, Pl. 23, figs. 1-4) described four poorly preserved specimens from the Hoko River Formation referring them to R. americana . However, as stated above, the type species does not have enough diagnostic features to make a comparison with the other species of Ranina .

Karasawa et al. (2014: 250, fig. 18C) figured a specimen of R. americana from the late Eocene Hoko River Formation ( KSU D677). This specimen is better preserved than the ones reported by Rathbun (1926) in having a wide, subtriangular first anterolateral spine, a second, directed outward, anterolateral spine with accessorial denticles on anterior edge of the spine, and a dorsal surface ornated by scabrous granules arranged in different ways along the carapace but never forming transverse rims. In addition, Karasawa et al. (2014) also lists three specimens of R. americana ( KSU D675, D676, D678) without any comparison with the type material. Indeed these specimens cannot be compared with the type material because they do not preserve the anterolateral spines and the frontal margin, main characters necessary to comparisons at specific level in Ranina .

Both specimens referred to R. americana by Rathbun (1926) and Karasawa et al. (2014) could be assigned to Raninidae sensu stricto. However, previous authors have not compared these specimens with the holotype or considered the differences in age and formations. Therefore, until new specimens are found preserving specific level characters these specimens should be referred as? Ranina sp.

Figures

Fig. 1 -?Ranina americana Whiters, 1924; holotype, NHM 23798. A) Dorsal view. B) Ventral view. (x 1.3).