Paractaea, Guinot, 1969

Ossó, Àlex, Kendrew, Eric & Luque, Javier, 2018, New occurrences of crabs (Decapoda, Brachyura, Eubrachyura) in the Pliocene of Florida (United States), Geodiversitas 40 (24), pp. 549-556 : 554-555

Paractaea cf. P. nodosa ( Stimpson, 1860) Fig. 3 A-C

MATERIAL. — One carapace, USNM PAL 720105, with cuticle preserved, partially embedded on limestone matrix, and with broken posterolateral margins.

MEASUREMENTS (in mm). — Length = 27; width = 38; fronto-orbital width = 20; posterior margin = 12.

DESCRIPTION Carapace transversely hexagonal, strongly sculpted, much wider than long, approximately 70% as long as the carapace maximum width. Fronto orbital approximately 50% the carapace maximum width. Carapace vaulted longitudinally at anterior third, weakly convex transversely. Regions well marked and defined by strong sub-regional lobules, except urogastric region; all sub-regional lobules covered by clusters of rounded granules. Grooves separating regions and subregions, broad, smooth. Front bilobed, slightly advanced, medially notched, sinuous with granulated edges; separated from the inner orbital angle by notches. Orbits directed for-

wardly; supraorbital margin raised, edges granulated, with two distal fissures separated by a medial tooth; infraorbital margin visible dorsally. Anterolateral margins convex with five granulated teeth or nodes (extraorbital tooth included; epibranchial tooth not preserved). Posterolateral margins straight. Posterior margin straight, rimmed, ornate with a row of granules, about 30% of total width. Frontal region smooth; post-frontal lobule distinct. Gastric process well defined by lobules; Protogastric region distinct of divided and parallel protogastric lobes. Mesogastric region three lobed, anterior small, reaching half of protogastric lobes, and the two-posterior subtriangular; metagastric region indistinct from posterior part of mesogastric region; urogastric region flattened, smooth, separated of meso- metagastric region by two gastric pits. Cardiac region V-shaped, divided posteriorly; intestinal region narrow, inflated laterally. Hepatic region smooth. Outer epibranchial lobe do not reaches anterolateral margin; inner epibranchial lobe V-shaped. Meso and metabranchial lobules distinct. Sternal, pleonal, and appendicular elements not preserved.

REMARKS

The general outline of the Florida’s specimen and its sculptured dorsal carapace indicates it belongs to Paractaea (see Guinot 1969). Nevertheless, its specific affinities are less clear given the great similarity among the different species and subspecies of Paractaea , all of them extant. Indeed, besides the number of existing species and subspecies of this genus, a number of forms of the type species P. rufopunctata (H. Milne Edwards, 1834) ( Fig. 4C ) have been erected through time, mostly based on differences in the dorsal sculpture, setations, appendages, and even geographic distribution (e.g. Guinot 1969; Mendoza et al. 2014: 275). In this respect, herein we follow the list of species and subspecies available of Paractaea , validated by Ng et al. (2008: 195, 196, 207). The anterolateral margin with five nodose teeth, and the pattern of the dorsal sculpture of the Florida’s specimen, fit perfectly within the anatomical range seen in P. rufopunctata . However, the fossil specimen has broader grooves separating the lobes and lobules than modern P. rufopunctata , in particular the urogastric region, which is large and smooth, and the two posterior lobules of metagastric region, which are subtriangular. Those characters match the diagnosis of Guinot (1969: 252, 253) for the American Atlantic species P. nodosa (as P. rufopunctata forme nodosa ): “un très large sillon entre l’aréole mésogastrique et la région cardiaque […] notons chez les nodosa des sillons dorsaux plus larges et, en conséquence, des lobules plus espacés.”(see also Rathbun 1930: 251, 257, 258). Therefore, in absence of other diagnostic features as chelae, ambulatory legs or ventral parts, missing in the specimen here studied, we consider it tentatively as P. nodosa ( Fig. 4D ).

Previously, Collins & Morris (1976: 125, 126, pl. 19, fig. 7) reported a specimen from the Pleistocene Coral Rock Series of Barbados as Actaea rufopunctata nodosa ( Luque et al. 2017: 55) . That specimen matches well the general diagnoses of either P. rufopunctata or P. nodosa . However, its lobules appear larger and tighter than in the specimen from Florida, and consequently the grooves separating them appear very narrow instead of broad as in the latter, which would separate it from the diagnosis of P. nodosa (sensu Guinot 1969). To our knowledge, the specimen from the Pliocene of Florida represents the second record of Paractaea in the fossil record and the oldest for the genus known to date.

Figures

FIG. 3. — Paractaea cf. P. nodosa (Stimpson,1860),USNM PAL 720105 from the Pinecrest Member of Tamiami Formation (middle Piacenzian, Pliocene) of locality B in Sarasota County, Florida (United States): A, dorsal view; B, frontal view; C, posterior view. Scale bar: 10 mm. Photographs by À. Ossó.

FIG. 4. — A, B, Persephona subovata (Rathbun, 1893) type material: A, USNM 17385 (as Myra subovata Rathun, 1893); B, USNM 69260 (as Iliacantha hancocki Rathbun, 1935),(photographs by Karen Reed); C, Paractaea rufopunctata (H. Milne Edwards, 1834) from Surigao Island, Philippines (Crab Database) (photograps by Ondřej Radosta); D, Paractaea nodosa (Stimpson, 1860) from Guadeloupe (from Legall & Poupin [2018]) (photographs by Joseph Poupin).