Propeamussium Gregorio, 1884
GREGORIO, A. DE. 1884. Nota intorno ad alcune nuove conchiglie mioceniche di Sicilia. Il Naturalista Siciliano, 3 (4): 119-120. [p. 119]
«Propeamussium n. sot. g. Questo sotlogenere è da me proposto per la specie descritta di seguito, È ad esso forse che dovrebbero pure riferirsi i P. semiradiatus e unguiculus Mayer (in Hofmann) etc.
Pecten (Propeamussium) Ceciliae De Greg. Conchiglia estremamente tenue e compressa; con superficie interna ed esterna levigala. Diam. 35 ͫ ͫ. Spess. 4 ͫ ͫ. La scultura consiste in filetti lineari sottilissimi, concentrici , e raggianti; nella regione periferica sono essi quasi del tutto cancellati, solo ve ne rimane qualcuno dei concentrici confondentesi con i segni di accrescimento. I filetti raggianti sono distinti nella regione umbonale.—Ciò che è più caratteristico in questa specie sono circa 9 raggi rossi color sangue, larghi abbastanza, quasi quanto gl'interstizi. Detti raggi non sono punto prominenti all'esterno (uè a quanto pare) all'interno, se se ne toglie forse parte della regione umbonale.—Essi non sono nò coste, nò mere zone colorate; affettano l'interna struttura e si possono isolare del resto della conchiglia come altrettante stecchette sottili.
La valva destra è appena convessa quasi piana; i raggi restano incastrati nella parte interna, ma traspaiono; essi stanno nella regione unibonale, arrivano alla mediana senza però traversarla tutta. La valva sinistra è ancor piìi piana; infatti è appena appena convessa nella regione umbonale, del resto è anche un po' concava, ciò però è forse dovuto a compressione subita nel fossilizzarsi. I raggi sono assai più marcati e appariscentij traversano non solo la regione umbonale, ma anche la mediana. Ha molta analogia co'll Amussium lucidum Jeffr., da cui si distingue per le zone colorate e per la diversa scullura principalmente pei filetti raggianti. Di questa interessantissima specie la mia guida V. Meneguzzo trovò vari frammenti ed un esemplare, privo però delle orecchiette, nella contrada Terrebianche in una marna bianca a forominifere che mi pare molto simile a quella di Malta.» ANTOINE DE GREGORIO, 1884
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P. (Propeamussium) Ceciliae De Greg.; A. de Gregorio, 1898, Etudes sur le genre Amussium, plate 4, figures 10-14.
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H. H. Dijkstra & A. G. Beu, 2018, Living scallops of Australia and adjacent waters, figure 1; Propeamussium alcocki (Smith), figures 1A, 1D; Propeamussium caducum (Smith), figures 1B, 1C, 1I; Propeamussium investigatoris (Smith), figures 1E, 1K-1M; Propeamussium siratama (Oyama, 1951), figures 1F-1H, 1J, 1N.
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«Propeamussium de Gregorio, 1884
Propeamussium de Gregorio, 1884: 119 (proposed as a subgenus of Pecten). Type species (by original designation): Pecten (Propeamussium) ceciliae de Gregorio, 1884; Miocene, Sicily, Italy.
Paramusium Verrill, 1897: 72. Type species (by original designation): Amussium dalli E. A. Smith (1885: 308); Recent, off Bermuda, W Atlantic, 796 m. Occultamussium Korobkov, 1937: 56 (proposed as a subgenus of Amusium). Type species (by original designation): Pecten semiradiatus Mayer, 1861; upper Eocene, Tyrol, Austria. Pseudopalliorum Oyama, 1944: 244 (proposed as a subgenus of Propeamussium). Type species (by original designation): Pecten interradiatus Gabb (1869: 199, 251); Eocene, E of New Idria, San Bernardino County, California, U.S.A. Bathyamussium Oyama, 1951: 79 (proposed as a subgenus of Ctenamusium). Type species (by original designation): Amussium jeffreysii E. A. Smith (1885: 310); Recent, N Sulu Sea, Philippine Islands, 686 m. Micramussium Oyama, 1951: 80 (proposed as a subgenus of Ctenamusium). Type species (by original designation): Ctenamusium (Micramussium) siratama Oyama (1951: 80); Recent, Sagami Bay, Japan, 234–291 m. Flavamussium Oyama, 1951: 81 (proposed as a subgenus of Parvamussium). Type species (by original designation): Amussium caducum E. A. Smith (1885: 309); Recent, W of Luzon, Philippine Islands, 1280 m. Luteamussium Oyama, 1951: 82. Type species (by original designation): Amussium sibogai Dautzenberg & Bavay (1904: 207); Recent, Bali Sea, Indonesia, 289 m. Diagnosis. Shell almost equivalve, fragile, rather small in most species, translucent in most species, laterally compressed, gaping along lateral margins; left valve smooth or sculptured with fine radial and/or commarginal riblets or striae, right valve with commarginal lines or lirae; auricles almost equal to equal; byssal notch moderately slight; ctenolium lacking; internal riblets commence in early ontogeny and extend to near the central region or to the pallial line.
Distribution. Eocene?–Recent. Cosmopolitan, 275–2740 m (Waller, 1971). Waller (2006a) thought that Jurassic species previously included in Propeamussium would be better assigned to Parvamussium. Schneider et al. (2013: 221) also stated that “All Jurassic to Oligocene propeamussiids that have been studied thoroughly to date belong to Parvamussium … Propeamussium did not evolve earlier than the Miocene.” D. Jablonski (pers. comm. 27 Jun 2017) pointed out that P. interradiatium (Gabb 1869), occurring in the Lutetian–Bartonian (Eocene) Tejon Formation, California, USA (Stewart, 1930: 123; Addicott, 1971; Moore, 1984: 7) “seems a potential species of Propeamussium given the equal auricles and nature of the internal ribs”. Further study is required of pre-Miocene records of these subtly distinct genera before the range of Propeamussium is certain, but a range from at least Eocene onwards seems likely.
Discussion. Grau (1959) restated the original diagnosis of Propeamussium de Gregorio, 1884, and of the type species P. ceciliae, with a translation into English. The type specimen subsequently was figured by de Gregorio (1898: pl. 4, figs 10–12). Gregorio’s figures 13 and 14, also mentioned by Grau (1959: 9), do not show the type species. Hertlein (1969: N350) supposedly refigured the right [sic] valve of the holotype, although North (1951b: 123) reported that he could not trace the holotype.
Grau (1959: 9) placed Paramussium, Pseudopalliorum, Flavamussium and Luteamussium in the synonymy of Propeamussium, and Hertlein (1969: N350) subsequently added also Occultamussium and Actinopecten Bonarelli, 1951 with a question mark. Hayami (1988a) enumerated also Parvamussium Sacco, 1897a (type species: Pecten duodecimlamellatus Bronn, 1832: 624), Ctenamussium [sic] Iredale, 1929 (type species: Amusium thetidis Hedley, 1902: 304), Glyptamusium Oyama, 1944 [sic] (= Glyptamusium Iredale, 1939) (type species: Amussium torresi E. A. Smith, 1885: 311), Bathyamussium Oyama, 1951 (type species: Amussium jeffreysii E. A. Smith, 1885: 310) and Micramussium Oyama, 1951 (type species: Ctenamusium (Micramussium) siratama Oyama, 1951: 80) as synonyms of Propeamussium. The type species of Ctenamusium and Glyptamusium are morphologically inseparable from Parvamussium, whereas the type species of Bathyamussium and Micramussium are more nearly similar to the morphological characters of Propeamussium. For the distinctive shell microstructure of Propeamussiidae see Waller (1972b) and Schein (1989).» DIJKSTRA, H. H. & A. G. BEU. 2018. Living scallops of Australia and adjacent waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae). Records of the Australian Museum, 70 (2): 113-330, figs. 1-102. [p. 121]
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Propeamussium (Striatoamussium) patriciae Poulton 1991; M. Aberhan, 1998, Early Jurassic Bivalvia of western Canada. Part I. Subclasses Palaeotaxodonta, Pteriomorphia and Isofilibranchia, plate 11, figures 1, 3, 5, 7.
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«Remarks. As pointed out by Damborenea (1998) there is some confusion regarding the generic relationships of internally ribbed propeamussiid bivalves. For example, in the Treatise (Hertlein in Cox et al. 1969) Variamussium SACCO was placed in the synonymy of Parvamussium SACCO, disregarding clear differences in the style of ornamentation on both valves. Furthermore, the time ranges of Propeamussium s.s. and Parvamussium are mixed. Damborenea (1998) concluded that most Jurassic species belong to Parvamussium rather than Propeamussium s.s. I regard Parvamussium and Propeamussium s.s. as subgenera of Propeamussium and a new subgenus, Striatoamussium, is herein erected.»
ABERHAN, M. 1998. Early Jurassic Bivalvia of western Canada. Part I. Subclasses Palaeotaxodonta, Pteriomorphia and Isofilibranchia. Beringeria, 21: 57-150, text-figs. 1-14, pls. 1-19. [p. 100]
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