Asthenognathus atlanticus, from here.

Belongs within: Brachyura.

The Pinnotheridae, pea crabs, are small crabs found living as commensals of other invertebrates such as bivalves, ascidians, etc. The free-living males are generally much smaller than the females.

Characters (from Davie 2002): Carapace typically more or less round or transversely oval, often poorly calcified (especially in commensal females); anterolateral margins smooth or laterally toothed; front narrow; orbits and eyes very small; cornea sometimes obsolescent. Antennules and antennae usually very small. Interantennular septum reduced to a thin plate or absent. Buccal cavern broad, short, usually semicircular. Third maxilliped with merus often very large; ischium usually smally, sometimes completely lost or fused with merus; exopod small, more or less concealed. Male genital openings sternal, but originally coxal; female openings sternal. Male abdomen narrow.

<==Pinnotheridae [Pinnotheroidea]
    |  i. s.: Pinnixa White 1846 CA04
    |           |--P. chaetopterana K-M02
    |           |--P. petersi Bott 1955 B55
    |           |--P. retinens Rathbun 1918 B55
    |           |--P. richardsoni Glassel 1936 B55
    |           `--P. salvadorensis Bott 1955 B55
    |         Dissodactylus Smith 1870 B55
    |           |--D. glasselli B55
    |           |--D. lockingtoni B55
    |           |--D. meyerabichi Botts 1955 B55
    |           `--D. nitidus Smith 1870 [incl. D. smithi Rioja 1944] B55
    |         Pinnotheres parvulus GLT03
    |         Mortensenella Rathbun 1909 CA04
    |         Hapalonotus de Man 1879 CA04
    |         Viapinnixa Schweitzer & Feldmann 2001 CA04
    |         Nannotheres moorei MD01
    |         Clypeasterophilus MD01
    |         Xanthasia murigera TSH09
    `--Asthenognathinae CA04
         |--Tritodynamia Ortmann 1894 CA04
         `--Asthenognathus Stimpson 1858 CA04
              |--*A. inaequipes Stimpson 1858 CA04
              |--A. atlanticus Monod 1933 CA04
              |--A. cornishorum Schweitzer & Feldmann 1999 CA04
              |--A. gallardoi Serène & Soh 1976 CA04
              |--A. globosa (Karasawa 1990) [=Tritodynamia globosa] CA04
              |--A. hexagonum Rathbun 1909 CA04
              |--A. microspinus Casadío, de Angeli et al. 2004 CA04
              `--A. urretae Schweitzer & Feldmann 2001 CA04

*Type species of generic name indicated


[B55] Bott, R. 1955. Dekapoden (Crustacea) aus El Salvador. 2. Litorale Dekapoden, außer Uca. Senckenbergiana Biologica 36: 45-70.

[CA04] Casadío, S., A. de Angeli, R. M. Feldmann, A. Garassino, J. L. Hetler, A. Parras & C. E. Schweitzer. 2004. New decapod crustaceans (Thalassinidea, Galatheoidea, Brachyura) from the Middle Oligocene of Patagonia, Argentina. Annals of Carnegie Museum 73 (2): 25-47.

Davie, P. J. F. 2002. Zoological Catalogue of Australia vol. 19.3B. Crustacea: Malacostraca: Eucarida (Part 2). Decapoda—Anomura, Brachyura. CSIRO Publishing: Collingwood (Victoria).

[GLT03] Glenner, H., J. Lützen & T. Takahashi. 2003. Molecular and morphological evidence for a monophyletic clade of asexually reproducing Rhizocephala: Polyascus, new genus (Cirripedia). Journal of Crustacean Biology 23: 548-557.

[K-M02] Klein-MacPhee, G. 2002. Croakers, drums, and weakfishes. Family Sciaenidae. In Bigelow and Schroeder’s Fishes of the Gulf of Maine (B. B. Collette & G. Klein-MacPhee, eds) 3rd ed. pp. 435-446. Smithsonian Institute Press: Washington.

[MD01] Martin, J. W., & G. E. Davis. 2001. An updated classification of the Recent Crustacea. Natural History Museum Los Angeles County, Science Series 39: 1-124.

[TSH09] Titelius, M. A., A. Sampey & C. G. Hass. 2009. Crustaceans of Mermaid (Rowley Shoals), Scott and Seringapatam Reefs, north Western Australia. Records of the Western Australian Museum Supplement 77: 145-176.


  1. Hi Chris,

    It's probably my fault, having missed something, but I haven't figured out how or from where the sort-of-cladograms you include are generated, and I also don't understand the alphanumeric codes. I love the diversity you include, and am a regular reader. I'm only commenting this time because I did my masters on pinnotherids (Dissodactylus)and was a coauthor of Clypeasterophilus. Of course I want to know more about how they all fit in.

    Keep up the great work,


  2. Hi Hugh,

    Thanks for commenting! The dendrograms* I put together myself by hand from what I've found in the literature. Because (a) the sources I've incorporated into them so far may not necessarily be the most up-to-date ones, and (b) even if they are up-to-date, there's every possibility I've misunderstood them, the results are of varied reliability. You can probably see just from looking at it that this page's tree, for instance, is certainly not one of the best.

    *(My preferred term [meaning 'tree diagrams'] for these things, as not all of them are meant to represent phylogeny. Many of them simply represent taxonomic groupings.]

    The alphanumeric codes indicate the source of each component of the dendrogram, generated from the initials of the authors and the date of publication. So, in the tree above, 'CA04' against a name indicates that I sourced it from Casadío, de Angeli et al. 2004. The source indicated by each code is labelled as such in the reference list.

  3. hi, Chris
    many of the pinnotherids you include are NOT pinnotherids anymore. Check Ng et al. (2008) at
    But you probably know that by now (I just notice this is more than two years old ;-) )

  4. Thanks for that, Emma. I have the publication you recommended on the to-do list :-)


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