The position of the Hymenosomatidae MacLeay, 1838, within the Brachyura (Crustacea, Decapoda)

Abstract

The Hymenosomatidae is unique among the Brachyura on the basis of spermatozoal ultrastructure and morphological characters of the adults and larvae. The location of the hymenosomatid male gonopore, always a controversial question, is here shown to be sternal, not coxo-sternal. This disposition, analogous to the arrangement of Thoracotremata, contradicts all morphological characters that indicate a heterotreme affiliation, close to the Majoidea and Dorippoidea. Molecular data also support such an assignment. The multiple hymenosomatid plesiomorphies are reviewed. The exceptional male reproductive system, a new scheme for the Eubrachyura, is assumed, at least in part, to be the result of a strong carcinisation in an ancient, deeply rooted group, at present the most ecologically diverse in Brachyura. The presence of the Hymenosomatidae on the former Gondwanan landmasses and its worldwide pattern of distribution are consistent with the hypothesis of a Gondwanan origin of the family.

Archaeochiapasidae n. fam., a new early Cenomanian brachyuran family from Chiapas, Mexico, new hypothesis on Lecythocaridae Schweitzer & Feldmann, 2009, and phylogenetic implications (Crustacea, Decapoda, Brachyura, Eubrachyura)

“…The 'incorporation' of lateral parts of the pleurites (and also of the first male pleonal somite) into the cephalothorax is only a false, misleading appearance (and many authors, such as Rathbun 1925; Garth 1958, have been invariably mistaken). In Inachoididae the exposed areas beyond the sides of the carapace are a part of the axial skeleton (Drach & Guinot 1982, 1983Guinot 1984;Guinot & Richer de Forges 1997;Santana 2008;Guinot 2011bGuinot , 2012Guinot et al 2013;Colavite et al 2019). Conversely, in Archaeochiapasidae n. fam.…”

Remarks on Inachoididae Dana, 1851, with the description of a new genus and the resurrection of Stenorhynchinae Dana, 1851, and recognition of the inachid subfamily Podochelinae Neumann, 1878 (Crustacea, Decapoda, Brachyura, Majoidea)

“…There is probable link between Inachoididae and Hymenosomatidae (Guinot 2011a(Guinot , 2011b. The deep grooves on the dorsal surface of the inachoidid carapace are different from the "grooves" that result into subdivisions forming marked plates in hymenosomatids.…”

“…A recent comparison of the brachyuran families Hymenosomatidae MacLeay, 1838 (Guinot 2011a(Guinot , 2011b and Inachoididae Dana, 1851, provided the opportunity to re-examine the morphology and taxonomic position of Paradasygyius Garth, 1958, previously studied by Drach & Guinot (1982, Guinot (1984), and . The heterogeneous nature of the genus suggested a reappraisal of its two species: P. depressus (Bell, 1835), its type species, and P. tuberculatus (Lemos de Castro, 1949).…”

Comparative ultrastructure of the spermatozoa of the Majoidea (Crustacea, Decapoda, Brachyura) with new data on six species in five genera

“…() showed several distinct lineages concurring with multiple groupings based on the overall carapace morphology and structure of the first gonopods (the first and second abdominal pleopods in males are modified into two pairs of gonopods for reproduction). From morphology, the superfamily Dorippoidea (Dorippidae and Ethusidae, in the past considered as two subfamilies of Dorippidae), is considered to be basal in the Heterotremata, like the Majoidea, but the precise relationships between the two superfamilies remain unknown (see Guinot ; 46–48). It is suggested (p. 48 in the latter work) that hymenosomatids, majoids and dorippids had a common ancestor, and that hymenosomatids and majoids subsequently diverged (hence the morphological and molecular similarities between hymenosomatids and the basal majoids such as inachoidids and inachids) while dorippids retained these ancestral relations.…”

“…The list of Ng et al . () included the five families quoted in Table , plus the Hymenosomatidae that is often elevated to superfamilial rank (see Guinot ); the genus Stenorhynchus , usually placed in Inachidae, is here assigned to the Inachoididae, as proposed by Guinot ().…”