. Bulletins of American paleontology. CoRBULiD Bivalves: Anderson C. ser/cea--Rght Valves 2 - c g â 5 c o [D 0) > Deeper Marine Intermediate Shallow Marine Brackish 0 a 5 ^ o°5i°q,o >p. D Hg ° <^ 5Ch^ JT _ S _ IS A. -3 -2 - 1 0 1 2 3 PC1: Size and Size-correlated Shape Text-figure 4.âPlot of lirst and second principle component scores (PCI and PC2) of right valves of Corhiila sericea. Procedures and results of the principal components analysis (PCA) are outlined in Anderson (1994). PCI (explaming about 55 % of the variance) represents size and size-correlated shape variability. PC2
. Bulletins of American paleontology. CoRBULiD Bivalves: Anderson C. ser/cea--Rght Valves 2 - c g â 5 c o [D 0) > Deeper Marine Intermediate Shallow Marine Brackish 0 a 5 ^ o°5i°q,o >p. D Hg ° <^ 5Ch^ JT _ S _ IS A. -3 -2 - 1 0 1 2 3 PC1: Size and Size-correlated Shape Text-figure 4.âPlot of lirst and second principle component scores (PCI and PC2) of right valves of Corhiila sericea. Procedures and results of the principal components analysis (PCA) are outlined in Anderson (1994). PCI (explaming about 55 % of the variance) represents size and size-correlated shape variability. PC2 (explaining about 16 % of the variance) represents valve elongation, more elon- gate valves have negative principle component scores. Criteria used to distinguish environmental categories are outlined in Appendix 1. See Appendix 2 for samples used for each category. (>100 m deep) that show evidence of downslope movement, such as the top of the Ri'o Gurabo section (Text-fig. 3), the top of the Rio Yaque del Norte sec- tion, and in the Canada Zalaya section (Saunders et 1986; Anderson, 1994). Intraspecific variability in the two most abundant corbulid species, C. sericea and C. viminea. are also related to paleoenvironmental factors. Corhiila sericea shows continuous morphologic variability along a pa- leoenvironmental gradient of salinity, depth, and bio- clastic fabric (Text-fig. 4). The smallest and least elon- gate C. sericea valves are found in intermediate and deeper marine deposits. Intermediate morphologies oc- cur in shallow-marine deposits, and larger (but not more elongate) valves generally occur in brackish-wa- ter deposits. A few valves categorized as "brackish- water" from the Lopez section of the Ri'o Yaque del Norte, however, do not fit this trend (triangles with negative values on the first principle component axis [PCI C\i o 3- C. sericea Right Valves Shallow rv larlne D â¡ R. Mao 1 - â R. Cans _ n m «= _ 0- 1 -rl â .â â â â
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