Persephona, Leach, 1817

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 : 550-554

Persephona cf. P. subovata ( Rathbun, 1893) Fig. 2 A-D

MATERIAL. — One dorsal carapace, USNM PAL 720104, found inside the shell of a specimen of the gastropod Hexaplex hertweckorum ( Petuch, 1988) .

MEASUREMENTS (in mm). — Length = 17; width = 14; fronto-orbital width = 5.4; posterior margin = 6.9.

DESCRIPTION

Carapace roundish, sub-ovate to sub-pyriform, slightly longer than wide, strongly vaulted, with coarse granulation dorsally, particularly towards the carapace margins. Fronto-orbital margin prominent, about two times as wide as it is long, somewhat upturned, extending forward well beyond the anterolateral margin ( Fig. 2A ); front narrow, wider than the orbits; orbits bearing two closed orbital fissures, the innermost orbit almost half as long as the outermost orbit ( Fig. 2B ). Sub-hepatic region not inflated and lacking a subhepatic spine or tubercle. Lateral margins ornamented with aligned coarse granules ( Fig. 2C ). Posterior margin bearing three well-developed marginal conical spines nearly as long as they are wide at their bases ( Fig. 2D ); mesial spine slightly longer than lateral spines; posterior margin between the lateral spines with large conspicuous granules. Sternal, pleonal, and appendicular elements not preserved.

REMARKS

Based on the overall carapace form, the dorsal granulation, and the presence of three posterior spines, the specimen studied could be assigned to either Persephona or Iliacantha Stimpson, 1871 , both closely related leucosiid genera within the Ebaliinae , and co-occurring in the western Pacific and eastern Atlantic coasts of the Americas. However, species within these genera are sometimes difficult to differentiate ( Hendrickx 1997), and most of their diagnostic characters are found on their chelipeds, ambulatory legs, mouthparts, pleon, gonopods, sternum, and carapace color patterns, which are not preserved in the fossilized studied material. Furthermore, juvenile specimens of Iliacantha spp. and Persephona spp. may lack some conspicuous traits seen in adults of their species such as the sub-hepatic swelling and the development of a sub-hepatic spine, obscuring the placement of incomplete fossil taxa.

Today, several species of Persephona occur in the coasts of Florida, such as P. aquilonaris Rathbun, 1933 , and P. mediterranea (Herbst, 1794) . Nevertheless, and despite the incompleteness of the material available for study, the fossil specimen does not seem to match any of the extant species currently known from the eastern Atlantic and the Gulf of Mexico (D. Felder and B. Galil, pers. comms. June 2018). In fact, the fossil from the Tamiami Formation seems to be more similar to either P. edwardsii Bell, 1855 , or P. subovata ( Rathbun, 1893) ( Fig. 4A, B ); both species from the eastern Pacific of the Americas. These species share with the fossil from the Tamiami Formation here reported the subovate carapace outline and the lack of a strong sub-hepatic tubercle (compare to Boone 1930: pl. 10; Hendrickx 1997: fig. 104; Magalhães 2012: fig. 16). Although P. edwardsii and P. subovata are restricted to the western Pacific and the fossil here studied comes from the Atlantic Gulf, it is possible that ancestral populations of P. edwardsii or P. subovata were present at both sides prior to the closure of the connectivity of water masses between the tropical Eastern Pacific and the Atlantic, and that the fossil from Florida is part of a relict population of P. edwardsii or P. subovata that disappeared in the Atlantic.

Several fossil records of Persephona are known from the Neogene and Quaternary of the tropical and subtropical Americas (see summary in Luque et al. 2017), including a similar specimen from the early-middle Pleistocene of Fort Drum, Okeechobee County, Florida, assigned to P. mediterranea by Portell & Agnew (2004) ( Luque et al. 2017: 49, 50, fig. 14F). Both specimens from Florida share the presence of some small granulations on the posterior margin between the main lateral spines, a carapace longer than wide, a similar dorsal granulation pattern, and a fronto-orbital margin extending well beyond the anterolateral margin, although the Pleistocene specimen from Okeechobee County is almost three times larger than the Sarasota specimen herein illustrated. In the Florida Museum of Natural History (FLMNH) Invertebrate Paleontology webpage, there are several records of Persephona sp. from the Tamiami Formation, most being cheliped articles (meri). Several other Persephona sp. remains from the Plio-Pleistocene Nashua and Caloosahatchee formations, and the Bermont and Fort Thompson formations are also included in the Invertebrate Paleontology collections at the FLMNH (see also Portell & Agnew 2004, and references therein). The new carapace confirms the presence of the genus in the Pliocene of Florida. Persephona aquilonaris has been reported for the Pleistocene Beaumont Formation of Texas ( Collins et al. 2014). Although it is tempting to include the Pliocene fossil here studied within P. aquilonaris due to the overlapping geographic ranges that include eastern United States and Mexico ( Magalhães et al. 2016), based on the evidence available it is not possible for us to include the new fossil among other Atlantic taxa with certainty, and rather seems to be more similar to P. subovata . For the time being, we assign this fossil to the latter species until more complete specimens become available for a more thorough comparison.

Superfamily XANTHOIDEA MacLeay, 1838

Family XANTHIDAE MacLeay, 1838

Figures

FIG. 2. — Persephona cf.P.subovata (Rathbun,1893),USNM PAL 720104 from the Pinecrest Member of Tamiami Formation (middle Piacenzian,Pliocene) of locality A in Sarasota County, Florida (United States):A, dorsal view; B, frontal view; C, left lateral view; D, 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).