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Dinogymnium pustulicostatum
Dinogymnium pustulicostatum May, 1977
Holotype: May 1977: Plate 1, Figures 2, 3
Locus typicus: Atlantic Highlands, New Jersey.
Stratum typicum: Mount Laurel Sand.
Age: Late Campanian-Early Maastrichtian
Description: May 1977, p. 115-118
Test elongate, width generally greater than 1/2 length, divided approximately midway by cingulum. Epitract and hypotract tapering; apex narrow and rounded; antapex broad and rounded. Sparse, narrow, longitudinal costae may be heterocostate, especially on hypotract; the longer costae extend toward, but not into the polar areas and become shorter on the ventral hypotract toward the sulcus. Test wall single layered ca. 0.5Ám thick; accordian-like in transverse section; bears pustules densely arranged. Pustules which penetrate cyst wall occur between and on the costae, causing a blistered appearance. Pustules bear wall canals; wall canals concentrated mainly near apex. Cingulum well defined, deeply indented, levorotatory with ca. one cingulum width offset. Well-defined, comma-shaped sulcus extends about halfway down the hypotract, terminating in a point. Possible anterior and posterior flagellar pores consisting of 2 broad tubes with pores visible at cingulum-sulcus intersection. Archeopyle apical; operculum biconvex, ca. twice as long as wide, tapering ventrally and dorsally to a narrow isthmus, and is attached at the dorsal and ventral tips.
Discussion: May 1977, p. 115-118
High numbers (45-64 percent) of D. pustulicostatum n. sp. occurring in the Mount Laurel Sand (samples 204-206) provides an opportunity to describe this species in great detail. Ninety-four specimens were selected, measured and studied.
Constant features of D. pustulicostatum appear to be the biconical shape of the epi- and hypotract; the broadly rounded antapex and narrowly rounded apex; cingulum position at or slightly posterior of equator; heterocostae best developed on hypotract; pustules densely arranged on external cyst surface; wall canals penetrating most pustules near apex, penetrating fewer pustules over most of remaining cyst surface; and costae slanting towards sulcus on ventral hypotract giving a chevron appearance. The surface of the cingulum and sulcus appears to be granular; however, scanning electron microscopy reveals the granae to be pustules bearing wall canals (Plate 1, Figures 11-13). The sulcus is mainly limited to the hypotract (Plate 1, Figures 1, 6, and 8). All specimens observed lacked a ventrally directed antapical point (e.g. D. acuminatum, Evitt et al. 1967), instead, being rounded. Size is quite variable among the Mount Laurel Sand specimens, the smallest specimen measuring 46 x 261Jm and the largest measuring 69 x 37Ám, representing a length difference of 1.5x. Variation in size appears to have little or nothing to do with the number of costae. For example specimens differing in length by a factor of 1.3 display the same number of costae on the hypotract. It does appear, however, that large specimens do display better developed costae. Distortion is common in D. pustulicostatum, and generally is the result of collapsing along the cingulum, causing a reduction in length by as much as 18 percent. Dorso-ventral compression is also common, possibly caused by compression in the sediment. Because of the corrugate nature of the cyst wall, both lateral expansion and contraction are possible. Tests are frequently observed in an expanded state, such that the costae are very low in relief, and test width is greatly increased. Also, tests are frequently observed in a contracted state, such that the costae have high relief and test width is greatly decreased. Thus, for studies involving natural variability, nondistorted specimens should be selected, or distortion should be compensated for when making measurements. For statistical analysis 94 specimens were measured from samples 204 and 205. The features measured were overall length, distance from apex to middle of cingulum, and width at the cingulum. These data were used to determine width-length ratios and cingulum indices. Cingulum index is the distance from the apex to the middle of the cingulum divided by the pole to pole distance times 100 (Evitt, Clarke, and Verdier, 1967). A summary of the data is listed below and plotted in Figures 3, 4a, and 4b.
Minimum Maximum Mean Holotype
Length46Ám69Ám56Ám60Ám
Width21Ám46Ám34Ám31Ám
CI45625350
Correlation Coefficient of length and width: 0.37
Significance of C. C. for length and width: 49.75
Correlation Coefficient of length and CI: -0.01
A comparison of length and width and cingulum index illustrates the effects of distortion on the various statistics summarized above. Variability between length and width has a rather low correlation coefficient (0.37), which is compatible with the nearly nonlinear scatter of points seen in Figure 4a, caused most likely by various types of distortion of the test length and width. It is likely that distortion has greater effect on width than on length because of the lateral flexibility of the accordian-like costae, which apparently causes most of the length-width variability. Thus, it is difficult to understand the meaning of this statistic; i.e., how much of the variability is natural and how much is caused by distortion? The scatter diagram of cingulum index (CI) versus length (Figure 4b) has a very low correlation coefficient (-0.01) suggesting a very low degree of association between these two statistics. Evitt (1967, page 14) indicated that this is important when the largest and smallest specimens differ by a marked factor. Evitt, also concludes, that the CI is essentially not affected by many distortions that apparently alter the cyst width, and that it is affected less than might be expected by longitudinal compression or extension of the cingulum. This applies only for specimens with a cingulum index near 50. A comparison of histograms for length, width, width-length ratio, and CI (Figure 3) illustrates the degree of normality of these statistics, suggesting that all measurements were made on one species. The Width-length ratio histogram has a much more expanded distribution with low amplitude suggesting distortion mainly of width.
Ornamentation consists of pustules densely arranged on the costae and in the depressions between the costae. The pustules bear wall canals which are especially concentrated near the apex. The wall canals are ca. 0.1 Ám across, pass from the cyst interior toward the exterior, and many of them open to the exterior, especially near the apex. On most of the epitract and hypotract only about 50 percent of the wall canals actually penetrate through the pustules to the exterior. The porous nature of the wall of D. pustulicostatum illustrates a striking similarity with the trichocyst pore-bearing tests of living motile stages of dinoflagellates. Evitt (1967, page 362) reported the possibility that Dinogymnium fossils could be motile stages. Further evidence of possible motility is found in the presence of openings similar in position to anterior and posterior flagellar pores (Pl. 3, Figs. 3a-6b). The anterior pore could have directed the transverse flagellum onto the cingulum, while the posterior pore could have directed the longitudinal flagellum onto the sulcus.
Affinity: D. pustulicostatum lacks a ventrally directed antapical point, and therefore differs from D. acuminatum Evitt et al. 1967. It is similar to D. acuminatum in that both species are somewhat bi-conical, heterocostate, bear numerous pustules and wall canals, and have similar cingulum index ranges (50-60).
D. pustulicostatum has marked levorotatory cingulum displacement and narrow, pustulate ridges, distinguishing it from D. microgranulosum Clarke and Verdier 1967. It is also generally smaller than D. microgranulosum.
Dimensions: Holotype L x W, 60Ám x 31Ám; epitract length 30Ám. Observed range (94 specimens measured): length 49Ám-66Ám; width, including dorsoventrally compressed specimens 23Ám-56Ám; width of noncompressed specimens 23Ám-43Ám. Cingulum Index 50-62%. Width: length ratio 43:98.
Occurrence: Mount Laurel Sand, extremely rare to abundant; Navesink Formation, extremely rare. Greatest occurrence, sample numbers 204, 205, and 206. Occurred in seven samples
Holotype: May 1977: Plate 1, Figures 2, 3
Locus typicus: Atlantic Highlands, New Jersey.
Stratum typicum: Mount Laurel Sand.
Age: Late Campanian-Early Maastrichtian
Description: May 1977, p. 115-118
Test elongate, width generally greater than 1/2 length, divided approximately midway by cingulum. Epitract and hypotract tapering; apex narrow and rounded; antapex broad and rounded. Sparse, narrow, longitudinal costae may be heterocostate, especially on hypotract; the longer costae extend toward, but not into the polar areas and become shorter on the ventral hypotract toward the sulcus. Test wall single layered ca. 0.5Ám thick; accordian-like in transverse section; bears pustules densely arranged. Pustules which penetrate cyst wall occur between and on the costae, causing a blistered appearance. Pustules bear wall canals; wall canals concentrated mainly near apex. Cingulum well defined, deeply indented, levorotatory with ca. one cingulum width offset. Well-defined, comma-shaped sulcus extends about halfway down the hypotract, terminating in a point. Possible anterior and posterior flagellar pores consisting of 2 broad tubes with pores visible at cingulum-sulcus intersection. Archeopyle apical; operculum biconvex, ca. twice as long as wide, tapering ventrally and dorsally to a narrow isthmus, and is attached at the dorsal and ventral tips.
Discussion: May 1977, p. 115-118
High numbers (45-64 percent) of D. pustulicostatum n. sp. occurring in the Mount Laurel Sand (samples 204-206) provides an opportunity to describe this species in great detail. Ninety-four specimens were selected, measured and studied.
Constant features of D. pustulicostatum appear to be the biconical shape of the epi- and hypotract; the broadly rounded antapex and narrowly rounded apex; cingulum position at or slightly posterior of equator; heterocostae best developed on hypotract; pustules densely arranged on external cyst surface; wall canals penetrating most pustules near apex, penetrating fewer pustules over most of remaining cyst surface; and costae slanting towards sulcus on ventral hypotract giving a chevron appearance. The surface of the cingulum and sulcus appears to be granular; however, scanning electron microscopy reveals the granae to be pustules bearing wall canals (Plate 1, Figures 11-13). The sulcus is mainly limited to the hypotract (Plate 1, Figures 1, 6, and 8). All specimens observed lacked a ventrally directed antapical point (e.g. D. acuminatum, Evitt et al. 1967), instead, being rounded. Size is quite variable among the Mount Laurel Sand specimens, the smallest specimen measuring 46 x 261Jm and the largest measuring 69 x 37Ám, representing a length difference of 1.5x. Variation in size appears to have little or nothing to do with the number of costae. For example specimens differing in length by a factor of 1.3 display the same number of costae on the hypotract. It does appear, however, that large specimens do display better developed costae. Distortion is common in D. pustulicostatum, and generally is the result of collapsing along the cingulum, causing a reduction in length by as much as 18 percent. Dorso-ventral compression is also common, possibly caused by compression in the sediment. Because of the corrugate nature of the cyst wall, both lateral expansion and contraction are possible. Tests are frequently observed in an expanded state, such that the costae are very low in relief, and test width is greatly increased. Also, tests are frequently observed in a contracted state, such that the costae have high relief and test width is greatly decreased. Thus, for studies involving natural variability, nondistorted specimens should be selected, or distortion should be compensated for when making measurements. For statistical analysis 94 specimens were measured from samples 204 and 205. The features measured were overall length, distance from apex to middle of cingulum, and width at the cingulum. These data were used to determine width-length ratios and cingulum indices. Cingulum index is the distance from the apex to the middle of the cingulum divided by the pole to pole distance times 100 (Evitt, Clarke, and Verdier, 1967). A summary of the data is listed below and plotted in Figures 3, 4a, and 4b.
Minimum Maximum Mean Holotype
Length46Ám69Ám56Ám60Ám
Width21Ám46Ám34Ám31Ám
CI45625350
Correlation Coefficient of length and width: 0.37
Significance of C. C. for length and width: 49.75
Correlation Coefficient of length and CI: -0.01
A comparison of length and width and cingulum index illustrates the effects of distortion on the various statistics summarized above. Variability between length and width has a rather low correlation coefficient (0.37), which is compatible with the nearly nonlinear scatter of points seen in Figure 4a, caused most likely by various types of distortion of the test length and width. It is likely that distortion has greater effect on width than on length because of the lateral flexibility of the accordian-like costae, which apparently causes most of the length-width variability. Thus, it is difficult to understand the meaning of this statistic; i.e., how much of the variability is natural and how much is caused by distortion? The scatter diagram of cingulum index (CI) versus length (Figure 4b) has a very low correlation coefficient (-0.01) suggesting a very low degree of association between these two statistics. Evitt (1967, page 14) indicated that this is important when the largest and smallest specimens differ by a marked factor. Evitt, also concludes, that the CI is essentially not affected by many distortions that apparently alter the cyst width, and that it is affected less than might be expected by longitudinal compression or extension of the cingulum. This applies only for specimens with a cingulum index near 50. A comparison of histograms for length, width, width-length ratio, and CI (Figure 3) illustrates the degree of normality of these statistics, suggesting that all measurements were made on one species. The Width-length ratio histogram has a much more expanded distribution with low amplitude suggesting distortion mainly of width.
Ornamentation consists of pustules densely arranged on the costae and in the depressions between the costae. The pustules bear wall canals which are especially concentrated near the apex. The wall canals are ca. 0.1 Ám across, pass from the cyst interior toward the exterior, and many of them open to the exterior, especially near the apex. On most of the epitract and hypotract only about 50 percent of the wall canals actually penetrate through the pustules to the exterior. The porous nature of the wall of D. pustulicostatum illustrates a striking similarity with the trichocyst pore-bearing tests of living motile stages of dinoflagellates. Evitt (1967, page 362) reported the possibility that Dinogymnium fossils could be motile stages. Further evidence of possible motility is found in the presence of openings similar in position to anterior and posterior flagellar pores (Pl. 3, Figs. 3a-6b). The anterior pore could have directed the transverse flagellum onto the cingulum, while the posterior pore could have directed the longitudinal flagellum onto the sulcus.
Affinity: D. pustulicostatum lacks a ventrally directed antapical point, and therefore differs from D. acuminatum Evitt et al. 1967. It is similar to D. acuminatum in that both species are somewhat bi-conical, heterocostate, bear numerous pustules and wall canals, and have similar cingulum index ranges (50-60).
D. pustulicostatum has marked levorotatory cingulum displacement and narrow, pustulate ridges, distinguishing it from D. microgranulosum Clarke and Verdier 1967. It is also generally smaller than D. microgranulosum.
Dimensions: Holotype L x W, 60Ám x 31Ám; epitract length 30Ám. Observed range (94 specimens measured): length 49Ám-66Ám; width, including dorsoventrally compressed specimens 23Ám-56Ám; width of noncompressed specimens 23Ám-43Ám. Cingulum Index 50-62%. Width: length ratio 43:98.
Occurrence: Mount Laurel Sand, extremely rare to abundant; Navesink Formation, extremely rare. Greatest occurrence, sample numbers 204, 205, and 206. Occurred in seven samples