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Deltoideum
Classification
Phylum:
Mollusca
Class:
None
Subclass:
Pteriomorphia
Order:
Pterioida
Suborder:
Ostreina (oysters)
Superfamily:
Ostreacea
Family:
Gryphaeidae
Subfamily:
Gryphaeinae
Formal Genus Name and Reference:
Deltoideum ROLLIER, 1917, p. 566
Type Species:
Ostrea sowerbyana BRONN, 1836, p. 316 (nom. subst. pro O. delroidea J. SOWERBY, 1816, p. 111, in SOWERBY & SOWERBY, non LAMARCK, 1806, p. 160, = 0 . delta SMITH, 1817, p. 18); SD ARKELL, 1932, p. 149 (footnote)
Images
(Click to enlarge in a new window)
Fig. ]76,1-5. "D. delta (SMITH) (=Ostreum SIIbdeltoideum PELLAT in BAYLE, 1878), U.Jur.(low.Kimmeridg.), LeHavre, France; 1,2, L V int., R V int., XO.5 (Bayle, 1878); 3, R V with LV, ext. (holotype of Ostrea laevitiscula J. DE C. SOWERBY, 1825), XO.5; 4,5, LV ints., X0.5 (3-5, Arkell, 1932-36)
Synonyms
Geographic Distribution
Eu. (Eng.-France-Ger.-Pol.-USSR)- Saudi Arab
Age Range
Beginning Stage in Treatise Usage:
M.Jur .(Bathon.)
Beginning International Stage:
Bathonian
Fraction Up In Beginning Stage:
0
Beginning Date:
168.17
Ending Stage in Treatise Usage:
U.Jur. (Portland.)
Ending International Stage:
Berriasian
Fraction Up In Ending Stage:
25
Ending Date:
141.75
Description
Medium-sized to large (to 17 em. long and 21 em. high), shell very flat, bilaterally much compressed (to 5.5 em. wide), outline spatulate to triangular, pyriform, or crescentic; many individuals with narrow, prominent bran- chitellum pointed toward rear in less extreme spatulate forms, but turning up toward dorsum in extreme more crescentic forms. LV as flat as RV, with low broad smooth irregular concentric undu- lations and few poorly appressed growth squamae; attachment area small to large, covering much of valve. RV very similar to L V , but in some species having short (7 0101.), narrow (0.5 0101.), rounded radial threads separated by flat wide (1.6 0101. or more) interspaces. Ligamental area flat; L V and R V resilifers very shallowly excavate; anterior bourrelet generally flatter and longer (by as much as 50 percent) than posterior one. Ad- ductor-muscle imprint in some individuals with very slightly concave dorsal margin flanked by well-rounded convexities; position of imprint close to posterior valve margin and closer to hinge than to ventral valve margin. No chomata. Ligamental area of older individuals rather high, with sub- parallel anterior and posterior margins, but in many shrinking in length as age advances, so that area constricts as it grows. Some old individuals no longer grew as to size of shell cavity but merely shifted it in ventral direction leaving behind many growth foliations which flank anterodorsal and posterodorsal valve margins. [ROLLlER'S claim that Deitoidelllll was attached by its RV is in error as ARKELL (1935, p. xvi) pointed out. Specimen figured by BAYLE (1878, pI. 132, fig. 1, as Ostreum Subdeltoideum PELLAT), examined by me at the Ecole des Mines, Paris, has large attach- ment area on LV and corresponding xenomorphic features on RV. ORIA (1933, p. 71-72) believed that DeltoideI/ill delta and Gryphaea dilatata J. SOWERBY, 1816, occurred together and had to be regarded as variants of one species. Thus Deltoideum, if accepted as a genus, presumably would be a descendant of Gryplzaea. ARKELL (1932-36, p. xvi-xvii) did not agree with these conclusions, but regarded DeltoideIum as a synonym of Lio-strea. Liostrea, Pernostrea, and DeltoideI/ill are probably close relatives.]
References
Rollier, Louis, 1917, Fossiles nouveaux ou peu connus des terrains secondaires (Mesozoiqutes) du Jura et des contrées environnantes, $b .1$, pt. 6 : Soc. Paléont. Suisse, Mém., v. 42 Rollier, Louis, , p. 501-634+errata page, pl. 33-40.
Museum or Author Information
Classification
Phylum:
Mollusca
Class:
None
Subclass:
Pteriomorphia
Order:
Pterioida
Suborder:
Ostreina (oysters)
Superfamily:
Ostreacea
Family:
Gryphaeidae
Subfamily:
Gryphaeinae
Formal Genus Name and Reference:
Deltoideum ROLLIER, 1917, p. 566
Type Species:
Ostrea sowerbyana BRONN, 1836, p. 316 (nom. subst. pro O. delroidea J. SOWERBY, 1816, p. 111, in SOWERBY & SOWERBY, non LAMARCK, 1806, p. 160, = 0 . delta SMITH, 1817, p. 18); SD ARKELL, 1932, p. 149 (footnote)
Images
(Click to enlarge in a new window)
Fig. ]76,1-5. "D. delta (SMITH) (=Ostreum SIIbdeltoideum PELLAT in BAYLE, 1878), U.Jur.(low.Kimmeridg.), LeHavre, France; 1,2, L V int., R V int., XO.5 (Bayle, 1878); 3, R V with LV, ext. (holotype of Ostrea laevitiscula J. DE C. SOWERBY, 1825), XO.5; 4,5, LV ints., X0.5 (3-5, Arkell, 1932-36)
Synonyms
Geographic Distribution
Eu. (Eng.-France-Ger.-Pol.-USSR)- Saudi Arab
Age Range
Beginning Stage in Treatise Usage:
M.Jur .(Bathon.)
Beginning International Stage:
Bathonian
Fraction Up In Beginning Stage:
0
Beginning Date:
168.17
Ending Stage in Treatise Usage:
U.Jur. (Portland.)
Ending International Stage:
Berriasian
Fraction Up In Ending Stage:
25
Ending Date:
141.75
Description
Medium-sized to large (to 17 em. long and 21 em. high), shell very flat, bilaterally much compressed (to 5.5 em. wide), outline spatulate to triangular, pyriform, or crescentic; many individuals with narrow, prominent bran- chitellum pointed toward rear in less extreme spatulate forms, but turning up toward dorsum in extreme more crescentic forms. LV as flat as RV, with low broad smooth irregular concentric undu- lations and few poorly appressed growth squamae; attachment area small to large, covering much of valve. RV very similar to L V , but in some species having short (7 0101.), narrow (0.5 0101.), rounded radial threads separated by flat wide (1.6 0101. or more) interspaces. Ligamental area flat; L V and R V resilifers very shallowly excavate; anterior bourrelet generally flatter and longer (by as much as 50 percent) than posterior one. Ad- ductor-muscle imprint in some individuals with very slightly concave dorsal margin flanked by well-rounded convexities; position of imprint close to posterior valve margin and closer to hinge than to ventral valve margin. No chomata. Ligamental area of older individuals rather high, with sub- parallel anterior and posterior margins, but in many shrinking in length as age advances, so that area constricts as it grows. Some old individuals no longer grew as to size of shell cavity but merely shifted it in ventral direction leaving behind many growth foliations which flank anterodorsal and posterodorsal valve margins. [ROLLlER'S claim that Deitoidelllll was attached by its RV is in error as ARKELL (1935, p. xvi) pointed out. Specimen figured by BAYLE (1878, pI. 132, fig. 1, as Ostreum Subdeltoideum PELLAT), examined by me at the Ecole des Mines, Paris, has large attach- ment area on LV and corresponding xenomorphic features on RV. ORIA (1933, p. 71-72) believed that DeltoideI/ill delta and Gryphaea dilatata J. SOWERBY, 1816, occurred together and had to be regarded as variants of one species. Thus Deltoideum, if accepted as a genus, presumably would be a descendant of Gryplzaea. ARKELL (1932-36, p. xvi-xvii) did not agree with these conclusions, but regarded DeltoideIum as a synonym of Lio-strea. Liostrea, Pernostrea, and DeltoideI/ill are probably close relatives.]
References
Rollier, Louis, 1917, Fossiles nouveaux ou peu connus des terrains secondaires (Mesozoiqutes) du Jura et des contrées environnantes, $b .1$, pt. 6 : Soc. Paléont. Suisse, Mém., v. 42 Rollier, Louis, , p. 501-634+errata page, pl. 33-40.