Paguristes liwinskii, Fraaije, René H. B., Van Bakel, Barry W. M., Jagt, John W. M. & Machalski, Marcin, 2015

Fraaije, René H. B., Van Bakel, Barry W. M., Jagt, John W. M. & Machalski, Marcin, 2015, A new hermit crab (Anomura, Paguroidea) from the upper Albian (Cretaceous) of Annopol, Poland, Zootaxa 3955 (4), pp. 588-594 : 589-592

Paguristes liwinskii n. sp.

( Fig. 1 C)

Diagnosis. Cross section of right cheliped transversely oval; dorsal and ventral sides convex, with regular, dense cover of forwardly directed, fine tubercles, largest arranged in row along dorsal outer side and along central proximal inner side; fixed finger short, stout and triangular; dactylus short and triangular, about twice length of fixed finger.

Etymology. Named in honour of the mayor of Annopol, Mr Wiesław Liwiński, who facilitated large-scale excavations conducted in this area in recent years by a team led by the last author (for details, see Machalski & Kennedy 2013 and Popov & Machalski 2014).

Type. The holotype, and sole specimen known ( ZPAL Cr.9/43), is a near-complete right palm with fixed finger and dactylus, measuring 10 mm in length, and 7 mm in greatest width.

Locality and stratigraphy. Kopiec near Annopol, lower part of unit 3 ( Fig. 1A ), upper upper Albian. Unit 3, c. 50 cm thick, is composed of quartz sand with abundant glauconite, passing gradually upwards into quartzglauconitic marl. A distinct bed of phosphatic clasts and fossils occurs in the upper part of unit 3. Its upper boundary is sharp, whereas the lower boundary is diffuse due to bioturbation ( Marcinowski & Walaszczyk 1985). The phosphatic clasts are c. 10 mm in diameter, but in the upper part of the layer they commonly form larger aggregates, up to 120 mm in diameter. Unit 3 of the Annopol succession is dated on the basis of specifically indeterminate specimens of the ammonite Mortoniceras (Subschloenbachia) , preserved as attachment scars on the left valves of some oysters ( Machalski and Kennedy 2013). These specimens are closest to Mortoniceras (Subschloenbachia) that characterise the upper upper Albian Mortoniceras perinflatum Zone.

Description. Globose right cheliped, cross section transversely oval; convex dorsal and ventral sides; all sides with regular, dense cover of forwardly directed, fine tubercles, largest in a row along dorsal outer and along central proximal inner sides. Fixed finger short, stout, curved, with a row of about four large setal pores on the inner and outer cutting edge and numerous irregular, longitudinal rows of finer pores on central and ventral parts; tip spatulate; cutting edge near-straight with concave central part. Dactylus short, triangular, curved, about twice the length of fixed finger; covered with irregular rows of setal pores smallest in dorsal half; tip pointed; strongly concave dorsal side here considered to be a preservational artefact, possibly resulting from unsuccessful predatory attack as some regeneration cuticle is visible on the proximal dorsal part of dactylus and the distal part of dorsal palm.

Discussion. The generic placement of fossil paguroid chelae is difficult in that claws and, occasionally, meri and carpi are all that is preserved. The specimen studied has been assigned to Paguristes because the claws of Paguristes santamartaensis are remarkably similar and members of Paguristes tend to be isochelous, whereas most other diogenid genera comprise species that are predominantly heterochelous with the left chela considerably larger. We have to keep in mind that the lefthandedness of most diogenids probably is the result of gastropod shell inhabitation, the great majority of marine snails being dextral. Fraaije (2003) noted a shift in molluscan inhabitation from ammonites to gastropods during the Cretaceous Period; this affected the morphology of hermit claws that ’blocked’ the aperture. It is also highly probable that Cretaceous species of Paguristes had isochelous chelae and that left heterochely mainly occurred subsequent to the Cretaceous/Paleogene boundary in relation to this shift in inhabitation.

To date, about 120 extant species of Paguristes are on record ( McLaughlin et al. 2010; Komai et al. 2015), illustrating that this genus is the most successful member of the Diogenidae by far. From the fossil record, Schweitzer et al. (2010) recorded a total of 15 species. Here, we list 17 species ( Tab. 1), inclusive of the new form, which extends the stratigraphic range of Paguristes downwards into the late Albian by about 25 myr. Four of the listed species ( P. santamartaensis , P. ouachitensis , P. whitteni and P. florae ) are of late Late Cretaceous, eight ( P. baldoensis , P. extentus , P. prealpinus , P. wheeleri , P. mexicanus , P. johnsoni , P. hokoensis and P. lineatuberculatus ) of Paleogene, two ( P. oligotuberculata and P. cserhatensis ) of Neogene and two ( P. cf. lymani and P. cf. syrtensis ) of Quaternary age. Only one of these records, i.e., that of P. cf. syrtensis , is based on a fragmentary dorsal shield (see Garassino et al. 2014).

Species Stratigraphic/geographic occurrence

P. liwinskii sp. nov. upper Albian, Poland P. santamartaensis Feldmann, Tshudy & Thomson, 1993 upper Santonian/lower Campanian, Antarctica P. ouachitensis Rathbun, 1935 upper Campanian, USA P. whitteni Bishop, 1983 Maastrichtian , USA

P. florae Collins, Fraaye & Jagt, 1995 upper Maastrichtian, the Netherlands – Belgium P. baldoensis Garassino, De Angeli & Pasini, 2009 Lower Eocene, Italy

P. extentus Beschin, Busulini, De Angeli & Tessier, 2007 Lower Eocene, Italy

P. prealpinus Beschin, De Angeli, Checchi & Zarantonello, 2005 Middle Eocene , Italy

P. wheeleri Blow & Manning, 1996 Middle Eocene , USA P. mexicanus Vega, Cosma, Coutiño, Feldmann ,

Nyborg, Schweitzer & Waugh, 2001 Middle Eocene, Mexico P. johnsoni Rathbun, 1935 Eocene , USA

P. hokoensis Schweitzer & Feldmann, 2001 Upper Eocene, USA

P. oligotuberculatus Müller & Collins, 1991 Upper Eocene, Hungary P. lineatuberculatus Beschin, De Angeli, Checchi & Mietto, 2006 Upper Eocene–Oligocene, Italy P. cserhatensis Müller, 1984 Miocene , Hungary

P. cf. lymani A. Milne-Edwards & Bouvier, 1893 Pleistocene , Jamaica

P. cf. syrtensis de Saint Laurent, 1971 Pleistocene, Italy

In overall shape and dense uniform ornamentation, Paguristes liwinskii sp. nov. most closely resembles P. santamartaensis , although the latter differs in having a smooth inner surface, a flattened dorsal surface and coarser tuberculation. The new species can be differentiated from P. ouachitaensis in that the palm has a convex inner side and transverse rows of tubercles are lacking. Paguristes whitteni has a much coarser ornament and a longer, strongly deflected fixed finger, while P. f l or a e is less globose, has fingers with a lesser curvature and the ornamentation is more subdued.

Paguristes baldoensis and P. extensus are less convex, have straighter dorsal and ventral sides and much longer fingers, whereas P. prealpinus has a smoother inner surface and a much longer and downturned fixed finger. Paguristes lineatuberculatus has a different ornamentation and the distal tip of the fixed finger is directed downwards, whereas P. wheeleri shows a strongly curved occlusal surface and much coarser tubercles and spines on both sides. The ornamentation in P. mexicanus is less uniform, with a reticulate outer surface near the upper margin.

Paguristes johnsoni can be differentiated in having a less globose palm, a longer fixed finger, and less dense and coarser ornamentation, while P. hokoensis has a significantly longer, downturned fixed finger and fewer, yet larger tubercles, arranged in longitudinal rows on the outer side of the manus.

Paguristes cserhatensis is less globose, and has fewer, yet much larger tubercles arranged in longitudinal rows; in addition, the fixed finger has a lesser curvature. The outer surface of the palm in P. oligotuberculatus has only few rows of coarse tubercles and the dorsal margin is straight and spinose, while P. cf. lymani differs in showing a smoother inner surface, straighter dorsal and ventral margins. Moreover, it does not have a uniform ornamentation.

Rathbun (1926: 101) described the preservation of the type and only known specimen of P. subequalis as follows, ‘ [.....] so crumbly that no more can be uncovered without destroying it. Only the form of the fingers is seen, and in the case of the propodal finger, nothing but the impression.’ Paguristes chipolensis was erected by Rathbun (1935) on the basis of a single, incomplete dactylus and propodus. The preservation of both P. subequalis and P. chipolensis is so poor that a detailed comparison is impossible; we propose that they are best regarded as nomina dubia and recommend removal from decapod crustacean species lists.

Figures

FIGURE 1. A, Litho- and chronostratigraphic column of the Annopol sedimentary succession (modified from Machalski & Kennedy 2013), level of Paguristes liwinskii sp. nov. is arrowed. B, Geological map of the Annopol area (inset: Poland). C, Paguristes liwinskii sp. nov., ZPAL Cr. 9 / 43 (holotype), from the lower part of unit 3, upper upper Albian, locality Kopiec; in outer (1), inner (2), ventral (3) and dorsal (4) views, respectively.