科研之友
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摘要
Abundant fossil material of extinct brachyurans has revealed morphological details hitherto rarely used in palaeontological studies. Detailed comparisons between extant and extinct material have been carried out, with an emphasis on thoracic sternum, abdomen and appendages. Documented for the first time is the unique character of Raninoidea De Haan, 1839, their 'gymnopleurity', which is not found in their predecessors, the Palaeocorystidae Lorenthey in Lorenthey & Beurlen, 1929. Palaeocorystidae, together with four other families (Camarocarcinidae Feldmann, Li & Schweitzer, 2008; Cenomanocarcinidae Guinot, Vega & Van Bakel, 2008; Necrocarcinidae Forster, 1968 emend.; and Orithopsidae Schweitzer, Feldmann, Fam, Hessin, Hetrick, Nyborg & Ross, 2003a emend.), is assigned here to the superfamily Palaeocorystoidea, of similar rank to Raninoidea. Both Raninoidea and Palaeocorystoidea are afforded a subsection rank and referred to as subsection Raninoidia De Haan, 1839 emend. New or emended diagnoses are provided for all higher taxonomic levels, and all members of Raninoidia are listed in an appendix. A unique abdominal holding structure, the double peg, is described for the first time. Its gradual evolution is documented and the phylogenetic implications are discussed. Comparative morphology of the thoracic sternum, abdominal holding structures, the sternumpterygostome configuration, respiratory physiology and spermathecae, all reveal polarities of the raninoidian clade. The configuration of the sternum with the pterygostome, which is related to body strength and respiratory physiological efficiency, differs significantly between the two superfamilies, Raninoidea showing a derived condition. An evolutionary lineage, leading from Palaeocorystidae, via Lyreididae to Raninidae is recognised, and an intermediate form, Marylyreidus punctatus n. comb., is discussed. Several hitherto unknown structures in extant raninoids, an obstruction system for the abdomen and a telson protection valve, are documented. The cryptic spermathecal apertures of raninoids, so far barely understood, are re-examined and compared to those of palaeocorystoids. The phylogeny of Podotremata, often debated in the recent literature, is discussed anew on the basis of these observations. A position of Raninoidea within Eubrachyura, recently claimed by several authors, cannot be maintained, an observation supported by documentation of the basal condition of Raninoidia. A new basal lyreidid clade, Marylyreidinae n. subfam., is erected, whereas new genera and species include Antonioranina n. gen. (Cyrtorhininae), Bournelyreidus teodorii n. gen., n. sp. (Lyreidinae), Cenocorystes bretoni n. sp. (Palaeocorystidae), Cenomanocarcinus cantabricus n. sp. (Cenomanocarcinidae), Eosymethis aragonensis n. gen., n. sp. (Symethinae), Eucorystes iserbyti n. sp., Eucorystes navarrensis n. sp. (both Palaeocorystidae), Ferroranina tamilnadu n. gen., n. sp. (Palaeocorystidae), Joeranina gaspari n. gen., n. sp. (Palaeocorystidae), Marylyreidus n. gen. (Marylyreidinae n. subfam.), Paranecrocarcinus balla n. sp. (Paranecrocarcininae), Symethoides monmouthorum n. gen., n. sp. (Symethinae) and Vegaranina n. gen. (Ranininae). Several raninoid and palaeocorystoid genera are revised, and emended diagnoses given.
- 出版日期2012-2-29
