Palaeocorystoidea

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 : 168-169

Palaeocorystoidea versus Etyoidea Guinot & Tavares, 2001

Extinct Etyoidea are discussed and listed by e.g. Carter (1898), Rathbun (1935b), Wright & Collins (1972), Schweitzer Hopkins et al. (1999), Guinot & Tavares (2001), Van Bakel et al. (2005), Fraaije et al. (2008b), Karasawa et al. (2008a), Collins & Breton (2009) and Klompmaker et al. (2011).

Carapace.

‒ Carapace varying from elongated to subcircular or subhexagonal in Palaeocorystoidea (exceptionally wide in Etyoidea).

‒ Areolation of dorsal carapace weak in Palaeocorystoidea (marked areolation in Etyoidea).

‒ Orbits medially uninterrupted in Palaeocorystoidea (widely separated through intercalation of antennular fossae in Etyoidea).

‒ Front narrow in Palaeocorystoidea (wide in Etyoidea).

‒ No antennular fossa in Palaeocorystoidea (distinct and large fossa for large basal antennular article in Etyoidea).

Pterygostome, endostome and mxp3.

‒ Endostome elongated (oxystomian condition) in Palaeocorystoidea (normal condition in Etyoidea).

‒ Mxp3 oxystomian in Palaeocorystoidea (entirely operculiform in Etyoidea).

Appendages.

‒ Chelae with spiny lower margin in Palaeocorystoidea for burying (chelae long and slender, without spinose lower margin in Etyoidea).

‒ Pereiopods 2‒4 with flattened articles in Palaeocorystoidea (cylindrical articles in Etyoidea).

Thoracic sternum.

‒ Shallow, lateral sterno-coxal depressions in Palaeocorystoidea (deep, complete sterno-coxal depressions in Etyoidea).

Abdomen.

‒ Female abdomen not reaching mxp 3 in Palaeocorystoidea (reaching mxp 3 in female Etyoidea).

Abdominal holding.

‒ Male abdomen in contact with coxae but no locking by appendages in Palaeocorystoidea (distinct structures on several pereiopods, P1‒P3 may be involved, to hold the abdomen in Etyoidea).