Crassadoma pusio (Linnaeus, 1758)
LINNAEUS, C. 1758. Sistema Naturae per Regna tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio Decima, Reformata, [iii], 824 p. Impensis Direct. Laurentii Salvii. Holmiae [Stockholm], 1758.[p. 698, sp. 169]
1758 Ostrea pusio Linnaeus, 1758
1778 Ostrea miniata Born, 1778
1778 Pecten distortus Da Costa, 1778
1791 Ostrea sinuosa Gmelin, 1791
1827 Pecten spinosus Brown, 1827
1832 Hinnites irregularis Deshayes, 1832
1843 Pecten isabellae Macgillivray, 1843
1853 Pecten crotilus Reeve, 1853
1778 Ostrea miniata Born, 1778
1778 Pecten distortus Da Costa, 1778
1791 Ostrea sinuosa Gmelin, 1791
1827 Pecten spinosus Brown, 1827
1832 Hinnites irregularis Deshayes, 1832
1843 Pecten isabellae Macgillivray, 1843
1853 Pecten crotilus Reeve, 1853
Talochlamys pusio (Linnaeus, 1758); B. K. Raines & G. T. Poppe, 2006, A Conchological Iconography, The Family Pectinidae, plate 240, figures 1-7.
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«O. testa radiis 40 filiformibus uniaurita.
Habitat in O. australiore. Testa magnitudine nucis coryli, utrinque aequaliter convexa. Auricula fere unica» CAROLUS LINNAEUS, 1758
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«Type locality [Ostrea miniata Born, 1778].– Not indicated (Index, 1778). “Patria ignota” [locality unknown (Testacea, 1780).
Type material.– An articulated syntype (H 36.8 mm, W 33.5 mm), NHMW 14095, is figured by Born (1780: pl. 7 fig. 1). On the inside of the left valve there is a label with “2859” and inside the right valve there are two small oval labels on the top of each other with “O. 25”, both in Indian ink. Below the oval labels “Born’s type” is indicated, with also an asterisk in red ink, an indication for the original specimen. This could be the handwriting of Brauer. Another articulated syntype (H 37.7 mm, W 35.2 mm), NHMW 14095, has not been figured by Born. On the outside of the right valve there is a small, oval label, with “O. 25” and on the inside of the left valve a similar label with “O.II.25.”, both in Indian ink. An asterisk in red ink is added on the inside of both valves. Remarks.– Born (1780: 104) repeated the original diagnosis (1778: 88). He also added the measurements “Long. 1 poll. 6 lin. [= 39.51 mm] lat. 1 poll. 4 lin.” [35.12 mm] of the figured type specimen “TAB. VI. fig. 3.”, which more or less agree with the isolated syntypes. He also added as locality “Patria ignota.” Taxonomic position.– Brauer (1878: 21) determined both isolated syntypes as “Pecten pusio: forma irregularis Weinkauff”, which is Ostrea pusio Linnaeus, 1758, placed by Dijkstra & Goud (2002: 69) in Talochlamys Iredale, 1929.» DIJKSTRA, H. H. 2009. Type specimens of Pectinidae (Bivalvia) described by Ignaz von Born (1778 - 1780). Basteria, 73: 99-116. [p. 109]
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Ostrea miniata Born, 1778; H. H. Dijkstra, 2009, Type specimens of Pectinidae described by Ignaz von Born, figures 33-40.
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«Remarks
Specimens of P. albolineatus and O. multistriata labelled as O. pusio are in the UUZM collection. In the LSL collection are also P. albolineatus, but not O. multistriata. Morphological characters of P. albolineatus most resemble Linnaeus’ descriptions (1758, 1764). Waller (1993: 215–6) discussed the selection of the lectotype of O. pusio based merely on the opinions of previous authors (Hanley, 1855; Cox, 1927; Dodge, 1952; Glibert & Van der Poel, 1965; Dance, 1967 and Wallin, 1991). None has compared the material of O. pusio from the UUZM and the LSL with the descriptions of Linnaeus (1758, 1764) in detail. In my opinion only the specimens of P. albolineatus resemble Linnaeus’ descriptions closely and one of these should have been selected as lectotype. However, according to the ICZN Art. 74a (v), it can not be proved that the lectotype selected by Waller, does not belong to the syntype series. Most probably this unmarked distorted specimen of O. pusio belonged to the younger Linnaeus or to Smith. Ostrea pusio of authors is commonly used for the Atlantic, cemented, distorted ‘‘chlamiid’’ species and for the uncemented, byssally attached ‘‘chlamiid’’ species from the Mediterranean Sea, but not for any species from the Indo-Pacific region.» DIJKSTRA, H. H. 1999. Type specimens of Pectinidae (Mollusca: Bivalvia) described by Linnaeus (1758-1771). Zoological Journal of the Linnean Society, 125: 383-443. [p. 419]
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Ostrea pusio Linnaeus, 1758; H. H. Dijkstra, 1999, Type specimens of Pectinidae described by Linnaeus, figures 4C-F.
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«Type specimens.— In the Linnaean Collection at the Linnaean Society, London, the pair of matching valves of a distorted and cemented "Chlamys" present in the tray bearing Collection Sequence No. 179, with height 37 mm and length 35mm, is herein designated the lectotype of Ostrea pusio Linnaeus, 1758. The background and basis for this designation are given in the following discussion.
The type or types of Pecten distortus Da Costa, 1778, have not been examined nor has their depository been; determined. Dance (1966: 283) reported that some Da Costa types are in The Natural History Museum, London, and some are in the Glasgow University Museum. Ms.; Kathie Way, Collections Manager at BMNH (Invertebrates I), reported that no type material for P. distortus has been found there (pers. comm., 1993). The type series of Pecten crotilus Reeve, 1853, BMNH 1993042, consists of four specimens mounted on a board in the Cuming Collection in The Natural History Museum (London). I examined these and determined that they are young Crassadoma pusio. Type locality.— Herein specified as northeastern Atlantic. Diagnosis.— Cemented Crassadoma of moderate size (uncommonly greater than 60 mm in height); ribs introduced continuously throughout ontogeny without distinct clustering or ordering; 60 to 80 ribs and riblets present at distal margin of mature shells; inner surface of valves with small foliated-calcite transgression in umbonal region, seldom extending past level of dorsal edge of adductor in mature shells. Morphological variation.— The height of right valves at the time of their cementation to the substratum varies from about 12 to 25 rnm. There is no evidence in the collections examined for geographic changes in the height at first cementation or in the frequency of cementation within samples. In general, all individuals within populations of Crassadoma pusio seem to become cemented after a certain stage of ontogeny is reached. Harper (1991: 192). however, found that some individuals remain uncemented and merely become lodged into the substratum by means of their irregular growth form. The presence of small foliated-calcite transgressions in the umbonal region of both valves is fairly consistent, again without observed geographic trends. Some exceptional specimens (USNM 543396) collected from floating mines and buoys off the Atlantic coast of Morocco, however, lack foliated calcite in the umbonal region even at a shell height of 36 mm, well past the stage of initial cementation. A foliated-calcite transgression is present, however, in a specimen from deeper water off Morocco (USNM 196510,132-234 m) and in a specimen from 90 m off Ivory Coast (USNM 764327). All of these specimens have coarse microsculpture in the pre-radial stage of the left valve like that of more typical C. pusio. Comparison.— The pre-cemented growth stage of the shell of Crassadoma pusio closely resembles the shell of C. multistriata of a similar size. Refer to the preceding section on C. multistriata for comparative details. C. pusio differs from other cementing "Hinnites" of the eastern Atlantic in being of smaller maximum size and having less extensive foliated calcite inside the pallial line. Both Hinnites corallinus and Chlamys ercolaniana (see above) lack the prominent commarginal lirae that are present between ribs in the early ontogeny of C. pusio. The early Chlamys stage of H. corallinus differs from those of the other two cementing species in having ribs that begin late, following an extensive pre-radial area having antimarginal striae in a uniform sweeping pattern. The Chlamys stage of Chlamys ercolaniana differs from that of C. pusio in having a distinctive microsculpture in rib interspaces. This consists of antimarginal striae of highly irregulaf trends, probably a vestige of the shagreen microsculpture present in the ancestry of this species. Contrary to a statement by Harper (1991: 190), C. pusio lacks shagreen microsculpture. The microsculptural pattern that she interpreted to be shagreen (her fig. 4.4) is a typical plesiomorphic pattern of antimarginal striae. Living habits.— The early growth stage of Crassadoma pusio is byssate on hard objects, particularly rocks or shells, later becoming cemented by the edges of the right valve to the same substratum. Depth records for specimens collected alive range from just below low tide level to about 100 m. Jeffreys (1863: 52) reported that the species lives in depths from 5 to 85 frn (9 to 155 m), with only young specimens found near or in the tidal zone. Geographic range.— Common throughout the British Isles from the Orkney Islands to Cornwall and extending across the North Atlantic as far westward as southwestern Iceland (Madsen, 1949: 30); present along European coasts from northern Norway (69º 22.5' N, Soot-Ryen, 1951) southward to Spain and Portugal; uncommon on African coast from Morocco to Ivory Coast; present in Azores; apparently rare in the westernmost Mediterranean. Stratigraphic range.— Pleistocene? to present. The common tendency for authors to combine cemented and non-cemented Crassadoma in a single species referred to as either Chlamys pusio or C. multistriata makes it difficult to tabulate stratigraphic occurrences from the literature when the presence of cementation is not specified (e.g. Sacco, 1897; Roger, 1939; Eames and Cox, 1956). Roger (1939: 167) noted that fossils with the form of C. distorta, presumably meaning cemented forms, are quite rare in the fossil record of the Mediterranean but occur in the Pliocene of France. Apparently the only cemented pectinid in the Pliocene Coralline Crag of Great Britain is the gigantic form that Wood (1861: 19) referred to as Hinnites cortesyi De France, 1821. Roger (1939) considered the latter to be a junior synonym of H. crispus. Indeed, Wood's superb illustration leaves little doubt that this is a true Hinnites and not a Crassadoma (see above). Fossils that Wood (1861: 33) determined to be "Pecten pusio, Pennant" are also present in the Coralline Crag as well as the younger Red Crag. These shells, as noted by Wood (1861: 34), are not cemented and retain their shell regularity to large size (greater than 50 mrn). Specimens of these that I examined can be identified with Crassadoma harmeri (Regteren Altena, 1937), which Glibert and Van de Poel (1965: 34) consider to be a subspecies of "Mimachlamys" multistriata (Poli). If these fossil Crassadoma are ancestors of true C. pusio, it is possible that the modern cemented form that is so common in British waters originated within the Pleistocene and possibly very late in the Pleistocene. Harper (1991: 197), who studied the phenomenon of cementation among many bivalve clades, also concluded that cementation in this species has a post-Pliocene origin. Discussion.— Malacologists have long acknowledged that the original description of Ostrea pusio by Linnaeus is too generalized to be useful and that the lot in the Linnaean Collection bearing this name contains shells belonging to more than one species. In the first detailed study of the Linnaean Collection after Linnaeus's death, Hanley (1855) reported that the marked receptacle bearing the name O. pusio in the collection "has unfortunately been converted into a general depository for all the loose valves of the smaller Pectens. ..." He acknowledged, however, that the box contained shells belonging to "the pusio of the British writers and the albolineatus of Sowerby's [1842] Monograph," as well as a "white valve of the young Islandicus." He conjured that Linnaeus's ill-fitting description may have been of a composite consisting of the valves of different species. He concluded, however, that the species then known to British writers as "P. sinuosus (= pusio) ... (of which there are many loose specimens in the cabinet) accords the best with the definition ..." This conclusion did little to resolve the problem of a type for Ostrea pusio, and in subsequent years Linnaeus's name, as well as the names Pecten distortus Da Costa, 1778, and O. sinuosa Gmelin, 1791, have all been used for the cemented pectinid of the northeastern Atlantic. Cox (1927: 43), adamantly defending the use of Linnaeus's name but applying it to both the cemented form of the Atlantic and the byssate form of the Mediterranean, said that he would propose "a definite specimen from the Linnaean Collection and figure it as the lectotype of the species." However, I can find no record that he ever did so. Dodge (1952: 178), in a later study of the Linnaean Collection, added nothing new to the findings of Hanley (1855). He urged retention of Linnaeus's name, however, because of its extensive use, particularly by writers in the last half of the nineteenth century. Glibert and Van de Poel (1965: 33) followed Dodge's advice, but noted further that even if O. pusio of Linnaeus be regarded as an unacceptable name, P. pusio Pennant, 1777, which applies to the British cemented species, is available and has priority over O. multistriata Poli, 1795 (and also over P. distortus Da Costa, 1778, and O. sinuosa Gmelin, 1791). Wallin (1991: 154), who reported on the contents of the Queen Ulrica Collection (which contains material that may have been examined by Linnaeus prior to the publication of his tenth-edition names in 1758) found specimens of O. pusio to be present. My own examination of the Linnaean Collection at the Linnaean Society in London in 1977 found that the tray labeled in Linnaeus's hand as O. pusio contains four specimens: a pair of matching valves of cemented Crassadoma pusio, height 37 mm, length 35 mm, with approximately 40 radial ribs (secondary ribs not counted); a pair of matching valves of Mimachlamys albolineata (G.B. Sowerby II, 1842); a single left valve of M. albolineata; and a single juvenile right valve of Chlamys islandica (Müller, 1776). Dance (1967: 8) urged that caution is necessary when designating types from the Linnaean Collection because of the checkered history of the specimens in the collection, which now includes non-Linnaean material. In the case of Ostrea pusio, however, it seems likely that specimens of this common species of the northeastern Atlantic were available to Linnaeus, as indicated by their presence in both the Linnaean and Queen Ulrica Collections. In view of the long history of usage of the name, the above designation of a lectotype from the Linnaean Collection seems to be justified. Material examined.— Recent material: USNM: 55 lots containing about 250 specimens, mainly from Great Britain but including material from Sweden, France, the Azores, Morocco, and the Ivory Coast. In addition, numerous specimens were examined in the collections abroad, mainly at BMNH, BRM, MNHN, AM, LM, and ZMC. Fossil material: No unequivocal cemented Crassadoma pusio were found among material examined at museums abroad, underscoring the apparent late origin of this cemented species. At the time of my European studies, however, the ontogenetic criteria for differentiating C. pusio and C. multistriata had not yet been discovered. WALLER, T. R. 1993. The evolution of Chlamys (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific. American Malacological Bulletin, 10 (2): 195-249 [p. 215-217]
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Crassadoma pusio (Linnaeus, 1758); T. R. Waller, 1993, The evolution of Chlamys, figures 5b, e, h (above); figures 6k, l (below).
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