Eryma georgeii Carter, 1886

Devillez, Julien & Charbonnier, Sylvain, 2021, Review of the Late Jurassic erymoid lobsters (Crustacea: Decapoda), Geodiversitas 43 (2), pp. 25-73 : 28-30

Eryma georgeii Carter, 1886

( Fig. 2 A-D)

Eryma georgeii Carter, 1886: 549 , pl. 16, fig. 4. — Van Straelen 1925: 267. — Woods 1930: 78, pl. 21, fig. 9. — Secrétan 1964: 69. — Schweitzer et al. 2010: 24.

Clytia georgei – Glaessner 1929: 115.

Eryma stricklandi – Förster 1966: 111, fig. 18, pl.15, fig. 1 (non 2-3, 6).

TYPE MATERIAL. — Holotype SM J 3247 ; one paratype SM J 3248 .

TYPE LOCALITY. — St. Ives, Cambridgeshire, United Kingdom.

TYPE AGE. — Oxfordian.

DESCRIPTION

Carapace

Sub-cylindrical carapace; deep and wide cervical groove, strongly inclined dorsally, sub-vertical under its strong median inflexion, joined to dorsal margin and to antennal groove; deep and shallow antennal groove, curved; short gastro-orbital groove, deep and wide, originating as median inflexion of cervical groove; deep postcervical groove, sinuous, joined to dorsal margin and to branchiocardiac groove at carapace mid-height, with a long and sinuous ventral extension; branchiocardiac groove slightly curved, narrow dorsally, joined to dorsal margin and to hepatic groove; shallow and narrow hepatic groove, concavo-convex, joined to cervical groove; inflated ω area; flat χ area; deep and wide inferior groove.

Thoracic appendages

Chelate P1; P1 propodus trapezoidal, inner and outer margins slightly rounded in shape, compressed dorso-ventrally; narrow dactylar bulge, posteriorly delimited by a deep groove; long P1 fingers, strongly curved inward, progressively narrowing to their distal extremity, basis of occlusal margin of the dactylus strongly curved, with small conical teeth very closely spaced.

Ornamentation

Carapace homogeneously covered by small and prominent tubercles, separated by wide rounded depressions; P1 propodus covered by small tubercles preceded by deep crescent-shaped depressions; fingers covered by depressions.

DISCUSSION

Eryma georgeii was described on a carapace and an isolated P1 chela. It is assigned to Eryma because of the short gastro-orbital groove, the presence of a junction between postcervical and branchiocardiac grooves at carapace midheight, the sinuous hepatic groove and the shape of the chela (trapezoidal, compressed propodus bearing curved fingers narrowing to their distal extremity).

Förster (1966) considered this species as a junior synonym of Eryma stricklandi ( Phillips, 1871) . This latter is based on a P1 chela which has not the classical morphology of those of the erymoid lobsters (see discussion above about Eryma for more details). However, Carter’s species is clearly an erymid, so E. georgeii is here considered as a valid species.

Eryma georgeii has an extremely elongated ventral extension of the postcervical groove, which is a unique feature among the genus. The ornamentation of this species made of tubercles separated by depressions is present in some species of the genus, but the tubercles of E. georgeii have the particularity to be strongly prominent. Moreover, the clearly trapezoidal shape of the P1 propodus of this species is distinct from that of E. jungostrix , E. lerasi , E. major , E. mandelslohi , E. modestiforme , E. quadriverrucatum , E. veltheimii , E. ventrosum , and E. westphali .

Figures

FIG. 2. —Eryma georgeii Carter,1868 and Eryma jungostrix Feldmann & Titus,2006 from the Oxfordian:A, B, holotype SM J 3247 of E.georgeii (St Ives,United Kingdom): general view (A), schema (B); C, paratype SM J 3248 of E. georgeii (St Ives,United Kingdom);D, carapace of E.georgeii NMB F501 (Soyhières,Switzerland),left lateral view;E-G, holotype USNM 530027 of E. jungostrix (Utah,United States):left lateral view (E), schema (F), right lateral view (G). Abbreviations:a, branchiocardiac groove; b, antennal groove;b1, hepatic groove;c, postcervical groove;cr, carpus;d, gastro-orbital groove;e1e, cervical groove;i, inferior groove;md, mandible;PoA, post-orbital area; pr, propodus; ω: attachment site of mandibular muscle. Photographs:A, C, D, J. Devillez; E, G, L. O’Reilly.Line drawings: J. Devillez.Scale bars: 1 cm.