Orithopsis tricarinata ( Bell, 1863 )

Van Bakel, Barry W. M., Guinot, Danièle, Artal, Pedro, Fraaije, René H. B. & Jagt, John W. M., 2012, A revision of the Palaeocorystoidea and the phylogeny of raninoidian crabs (Crustacea, Decapoda, Brachyura, Podotremata) 3215, Zootaxa 3215 (1), pp. 1-216 : 69

Orithopsis tricarinata ( Bell, 1863)

( Fig. 22A–F )

Necrocarcinus tricarinatus Bell, 1863: 21 .

Orithopsis bonneyi Carter, 1872: 530 .

Material examined. Holotype of Orithopsis bonneyi Carter, 1872 , upper Albian (upper Greensand), Lyme Regis, Dorset, UK ( SM B58557); female, carapace and abdomen, Cambridge Greensand, Cambridge, UK ( SM B58557); upper Albian, Cambridge Greensand, Cambridge, England, partial carapace with partial thoracic sternum ( IRScNB unnumbered (Van Straelen Collection, see also Guinot et al. 2008: fig. 9f); carapace, upper Albian, ‘Gault’, Folkestone, England ( NHM BM 59808); lectotype, designated by Wright & Collins (1972: 67), carapace, upper Greensand (probably uppermost Albian according to Wright & Collins 1972: 67), Wiltshire, England ( NHM BM 59519); female, carapace with sternum, abdomen and bases of pereiopods, Albian, ‘Gault’, Folkestone, England ( NHM In. 30297).

Emended description. Subhepatic region narrow, with single, blunt, granular crest. Pleural line distinct, raised, granular. Pterygostome tumid, with blunt crest parallel to subhepatic crest, becoming more acute anteriorly; second blunt crest less well-defined, parallel to margin of P1 coxa. Buccal cavity wide, buccal margin weakly concave, with broad, smooth buccal collar; posterior corner of pterygostome simple. Branchiostegite developed, tumid. Sternites 1‒4 exposed: sternites 1, 2 on lower level; sternite 1 small, oval; sternite 2 trapezoidal; sternite 3 diamond shaped with apex pointing downwards; separated from sternite 4 by deep lateral grooves; sternite 4 large, trapezoidal, anterior margin slightly wider than sternite 3, lateral sides concave, surface with deep axial gutter; episternite 4 large, wide, gynglyme for P1 large, visible in dorsal view. P1–P4 coxae large, on same level, slightly decreasing in size posteriorly; P5 (sub)dorsal, reduced. Female abdomen with all somites free, covering thoracic sternum in width, thus in contact with coxae of pereiopods. Abdominal somite 1 not preserved; somites 2–5 progressively increasing in width, tricarinate, with strong, widened, thorn-like tubercles, strongest on somite 4; somite 6 long, widening towards telson, surface with central spine, anterior corners swollen. Telson incompletely preserved, granular.

Remarks. Discovery of a specimen with well-preserved ventral characters (NHM In. 30297) necessitates an amendment of the description; the dorsal carapace was described by Wright & Collins (1972: 67). Orithopsis tricarinata (see Bell 1863: 21, pl. 4, figs. 9–11), from the upper Aptian-lower Cenomanian of southern England, northern Spain, plus the lower Cenomanian of Mangyshlak, Kazakhstan ( Ilyin 2005, as Necrocarcinus tricarinatus ) and?upper Albian of Angola, of which O. bonneyi Carter, 1872 (upper Aptian-lower Cenomanian, southern England) is a junior synonym, was previously known mainly from the dorsal carapace. Guinot et al. (2008: 32) stated that, ’ Orithopsis tricarinata has remained an insufficiently known species and, moreover, lacks preserved ventral structures, except for the trituberculate (?male) abdominal segments described by Wright & Collins (1972: 68) ’. Specimen NHM In. 30297 shows well-preserved features of the thoracic sternum and abdomen for the first time.

Figures

FIGURE 22. A, B, D, E, Orithopsis tricarinata (Bell, 1863) (Orithopsidae), NHM In.30297 (female), Albian, Folkestone (southern England); ventral view; posterior view showing abdomen; detail of abdomen, anterior portion of thoracic sternum and bases of pereiopods, and detail of abdomen and pereiopods in posterior view; C, F, Orithopsis tricarinata (Bell, 1863), IRScNB unnumbered [Van Straelen Collection; indeterminate sex], upper Albian Cambridge Greensand, Cambridge (southern England); dorsal view of carapace, and ventral view showing anterior part of thoracic sternum; G, Orithopsis angelicus (Fraaije, 2002), MAB k. 2548 (holotype; indeterminate sex), upper Maastrichtian, Maastricht, the Netherlands; dorsal view of carapace (composite photograph). 1, 2, 3, 4, thoracic sternites 1, 2, 3, 4; 4/5, thoracic sternal suture 4/5; a2, a3, a4, a5, a6; abdominal somites 1, 2, 3, 4, 5, 6; cx1, cx2, cx3, cx4, cx5, P1-P5 coxae; e4, e5, episternites 4, 5; g1, gynglyme for P1 coxa. Scale bars: 5mm.