Marylyreidus, Van Bakel & Guinot & Artal & Fraaije & Jagt, 2012

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 : 86-87

Genus Marylyreidus n. gen.

Type species. Notopocorystes punctatus Rathbun, 1935b .

Diagnosis. As for subfamily.

Derivation of name. In honour of the late Mary J. Rathbun, in recognition of her highly valuable work on fossil and extant crabs. Gender masculine.

Remarks. Notopocorystes punctatus (see Rathbun 1935b: 8, pl. 12, figs. 14–16; Haj & Feldmann 2002: 473, figs. 3, 4.1–4.6), which is a senior synonym of both Notopocorystes parvus (see Rathbun 1935b: 48, pl. 12, figs. 11–13) and Raninella mucronata (see Rathbun 1935b: 50, pl. 14, figs. 32, 33), from the upper Albian–lower Cenomanian of Texas, was originally referred to Raninidae . It has typically been attributed to Cretacoranina (e.g., Haj & Feldmann 2002; Waugh et al. 2009) or Raninella (e.g., Rathbun 1935b; Feldmann & Maxey 1980; Tucker 1995; Bishop & Williams 2000). Haj & Feldmann (2002: 478) mentioned that the species was distinguished from other members of Cretacoranina by the fainter carapace areolation and weaker lateral and frontal spines. Waugh et al. (2009: 33) noted that the thoracic sternum and frontal arrangement of the present species did not conform to that of Cretacoranina , but that the cuticle microstructure (fungiform nodes) was remarkably similar. Marylyreidus n. gen. is erected herein to accommodate Notopocorystes punctatus , and placed in Lyreididae , as the only member of Marylyreidinae n. subfam. The new genus can easily be distinguished from Cretacoranina by those characters that exclude it from Palaeocorystoidea (see above).

Characters distinguishing Marylyreidus punctatus n. comb. from members of Raninella are a carapace that is much less wide, anterolateral margin with one small spine (two strong, flattened spines in Raninella ), posterolateral margin rounded (sharp, with distinct rim in Raninella ), cuticle with fungiform nodes (inclined nodes in Raninella ); pterygostome areolated (evenly swollen in Raninella ), sternite 4 narrow, not connected to pterygostome (clearly widened anteriorly, junction sternum-pterygostome in Raninella ), and sternite 5 devoid of medial line (medial line present in Raninella ).

The presence of a single anterolateral spine, the rounded nature of the posterolateral margin and cuticle microstructure serve to distinguish the carapace of Marylyreidus n. gen. from Bournelyreidus n. gen. The condition of the pterygostome is remarkably similar in these genera. The unique condition in Marylyreidus n. gen. of sternite 4 (i.e., not widened anteriorly, no junction sternum-pterygostome) and sternite 5 (extremely wide between P1 and P2), however, is absent in Bournelyreidus n. gen.