Bull. rial. Hist. Miis. Land. (Geol.) 53(2): 135-138 



Issued 27 November 1997 



New information on Cretaceous crabs 



C.W. WRIGHT 



The Old Rectory. Seaborough, Beaminster, Dorset DT8 3QY 



Synopsis. Re-examination of the supposedly Jurassic, Tithonian crab fauna from Klement in Austria shows that it is 

 Cretaceous, Cenomanian, thus removing the puzzling record of Diaulax from the Jurassic. A new species of Paranecrocarcinus 

 is described from the Lower Cretaceous, Barremian of Zululand, South Africa. New material from the English Lower Cretaceous 

 is described, including a new species of Rathbunopon from the Lower Aptian and important new information about Wither.sella. 



THE KLEMENT TITHONIAN' CRAB FAUNA 



In 1 93 1 Glaessner listed a small fauna of Crustacea from a block of 

 presumed Tithonian limestone in a conglomerate at Klement in 

 Lower Austria. It is of importance because it included a species of 

 Diaulax, a relatively advanced genus otherwise known only from the 

 Cretaceous, Lower Albian to Cenomanian. Shortly before his death 

 Glaessner entrusted me with his Klement specimens with a view to 

 joint description, since he had doubts about their Jurassic date. 

 These doubts were fully justified, since revised identifications indi- 

 cate that the fauna is almost certainly of Cenomanian date. 

 The original (Glaessner, 1931) and the new identifications are: 



Original: 



Prosopon verrucosum Reuss 



Pithonoton marginatum Meyer 



Cyphonotus oxythyreiformis 



(Gemmellaro) 

 Diaulax sp. 



Revised: 



Rathbunopon obesum (Van 



Straelen) 

 Pithonoton cenomanense 



Wright & Collins 



Palaeodromites incertus (Bell) 

 Diaulax oweni (Bell) 



The 'Prosopon verrucosum' (BMNH IC 6, Fig. 1) resembles very 

 closely the fragmentary English Cenomanian specimen identified 

 by Wright & Collins (1972: 23, pi. l,fig. 8) as Rathbunopon obesum 

 (Van Straelen), a species originally described from the Cenomanian 

 of Navarre, Spain. A second, minute, specimen (BMNH IC 14, Fig. 

 2) probably belongs to the same species but is too juvenile for certain 

 attribution. 



The 'Pithonoton marginatum' (BMNH IC 17, Fig. 3) conforms 

 well with P. cenomanense Wright & Collins in the outline of the 

 cephalothorax, the course of the cervical and branchiocardiac 

 grooves, and the disposition of the granules. Differences between 

 species of Pithonoton are generally fine, but identity with P. 

 cenomanense seems highly probable. 



The 'Cyphonotus oxythyreiformis' (BMNH IC 8, Fig. 4), though 

 incomplete, is beautifully preserved and is undoubtedly identical 

 with Palaeodromites incertus, of which an English specimen of the 

 same size is figured for comparison (Fig. 5). Species of 

 Palaeodromites were shown by Wright & Collins to have a short 

 range in the Cretaceous and this Klement specimen alone is suffi- 

 cient to demonstrate the Cenomanian age of the fauna. 



The 'Diaulax sp.' (BMNH IC 7, Fig. 6) is certainly a Diaulax and 

 differs in no way from the abundant English material of D. oweni 

 from the Lower Albian to the Cenomanian. The immediate ancestor 

 ofD. owen/ has not been identified but Wright & Collins (1972: 55) 

 referred to the origin of Diaulax in "broad flat species of Pithonoton'; 



they commented (p. 56) on the supposed Upper Jurassic occurrence 

 from Klement as representing 'a very early development of a 

 relatively advanced carapace form', an anomaly now removed by 

 the revised dating of the Klement fauna. 



A NEW SPECIES OF PARANECROCARCINUS 

 FROM THE BARREMIAN OF ZULULAND 



Genus Paranecrocarcinus Wan Straelen, 1936 



Type species. Paranecrocarcinus hexagonalis Van Straelen, 1 936 

 (p. 36, pi. 4, figs. 6, 7) from the Hauterivian of Auxerre, France, by 

 monotypy. 



Discussion. Wright & Collins (1972) differentiated 

 Paranecrocarcinus from Necrocarcinus by the bifid rostrum of the 

 former and the trifid rostrum of the latter. They then united Forster's 

 ( 1 968) Protocarcinus, as a synonym, and Pseudonecrocarcinus as a 

 subgenus of Paranecrocarcinus, separating the two subgenera partly 

 on the basis that P. (Paranecrocarcinus) did not have and P. 

 (Pseudonecrocarcinus) did have post-rostral slits in the carapace. 

 This distinction was false, since the type species/^ hexagonalis Ao^s 

 have post-rostral slits. The remaining diagnostic character of 

 Pseudonecrocarcinus, the many small rounded tubercles on the 

 surface of the carapace, as seen both in the Maastrichtian type 

 species P. (Pseudonecrocarcinus) quadriscissus (Noetling) and in 

 the Cenomanian P. (P) biscissus Wright & Collins, might be thought 

 sufficient to justify the two subgenera. However, some doubt is cast 

 on this idea by the juvenile specimen of fl biscissus discussed in the 

 last section of this paper below. Provisionally I am inclined to 

 abandon the distinction of two subgenera. 



Paranecrocarcinus kennedyi sp. nov. 



Figs 7, 13 



Name. For Professor W J Kennedy who found the specimen. 



HOLOTYPE. BMNH IC 16, from the Barremian Makatini Forma- 

 tion, Mlambongwenya Spruit, Zululand, South Africa. 



Diagnosis. A Paranecrocarcinus with a transverse row of nine 

 tubercles across the gastric regions and a single one on each 

 metabranchial lobe and with two prominent spines on the anterola- 

 teral border; apparently without post-rostral slits. 



Description. The holotype consists of an internal mould with the 

 rostrum and margins only partially preserved, together with the 

 counterpart showing the central area of the cephalothorax in hard 



) The Natural History Museum, 1997 



