SYSTEMATIC PALEONTOLOGY
The synonymies shown here include the first description and representative references that illustrate the development of the species concept for the taxon.
Genus BACHMANNOCENA Locker, 1974, emend. Bukry, 1987
Bachmannocena diodon (Ehrenberg) Bukry
Mesocena diodon Ehrenberg, 1844, pp. 71, 84.
Bachmannocena diodon (Ehrenberg), Bukry, 1987, p. 404.
Remarks: This species was abundant in Samples 207-1258A-15R-CC through 16R-CC. The specimens are fairly large, with an oval to round basal ring and two prominent basal spines on opposite ends of the long axis of the basal ring, and appear to be very similar to other B. diodon in the literature (see McCartney and Wise, 1987, pl. 4, fig. 5, for a photograph of a typical specimen). The early Eocene age of these samples may be the oldest known occurrence of this taxon. B. diodon is typically found in the middle–upper Miocene (see, for example, Locker and Martini, 1986; McCartney and Wise, 1987). Bachmannocena occidentalis Hanna ex Bukry, 1977, with four spines, is sometimes recorded from the Eocene but was not found in this study.
Three specimens were found that had a third spine in the 2-o'clock or 10-o'clock position with respect to the major axis. These are counted separately in Table T2. The three specimens were found in different samples.
Corbisema apiculata (Lemmermann)
Corbisema triacantha var. apiculata Lemmermann, 1901, p. 259, pl. 10, figs. 19, 20.
Corbisema apiculata (Lemmermann), Ling, 1972, p. 153, pl. 24, fig. 1; Shaw and Ciesielski, 1983, p. 706, pl. 1, figs. 1–3.
Remarks: This taxon was found in the upper Paleocene, Sample 207-1257A-7X-CC, and in the lower Eocene, Samples 207-1258A-3R-CC and 4R-CC.
Corbisema bimucronata Deflandre
Corbisema bimucronata Deflandre, 1950, p. 191, figs. 174–177.
Corbisema bimucronata Deflandre, Bukry and Foster, 1974, p. 307, pl. 1, fig. 1.
Corbisema bimucronata Deflandre, Bukry, 1975, p. 853, pl. 1, fig. 3.
Corbisema sp. cf. C. hastata hastata (Lemmermann), Bukry, 1978, pl. 4, figs. 22–24.
Remarks: This taxon is unusual among Corbisema in having blunt corners on the basal rings, which sometimes have two short spines. There was some variation, with some specimens having short spines and others having blunt corners without spines. Several specimens had both blunt and spined corners. Most specimens had a long axis (see Bukry, 1978, pl. 4, fig. 24). Bukry and Foster (1974) record this as commonly occurring in the middle Eocene Dictyocha hexacantha Zone.
Corbisema hastata (Lemmermann)
Corbisema triacantha var. hastata Lemmermann, 1901, p. 259, pl. 10, figs. 16, 17.
Corbisema hastata (Lemmermann), Ling, 1972, p. 155, fig. 5.
Remarks: This taxon was relatively abundant in Sample 207-1257B-2R-CC and sparse elsewhere. The specimens are fairly small, with very short spines.
Corbisema inermis inermis (Lemmermann)
Dictyocha triacantha var. inermis Lemmermann, 1901, p. 259, pl. 10, figs. 16, 17.
Corbisema inermis inermis (Lemmermann), Bukry, 1976, p. 892, figs. 2, 3.
Remarks: This taxon occurs consistently in the Paleocene in Hole 327A (Bukry, 1976) and in the lower middle Eocene of Site 605 (McCartney and Wise, 1987). It occurs sporadically in the present study.
Dictyocha triacantha var. recta Schulz, 1928, p. 250, fig. 32a, 32b.
Corbisema recta (Schulz), Ling, 1972, p. 155, pl. 24, figs. 6, 7; McCartney and Wise, 1987, p. 804, pl. 1, figs. 11, 12.
Remarks: A single specimen of this taxon was found in Sample 207-1258A-3R-CC.
Corbisema triacantha (Ehrenberg)
Dictyocha triacantha Ehrenberg, 1844, p. 80.
Corbisema triacantha (Ehrenberg), Hanna, 1931, p. 198, pl. D, fig. 1; Bukry and Foster, 1974, p. 305, fig. 1e.
Remarks: This taxon was found in middle Eocene Samples 207-1257A-7X-CC and 207-1257B-2R-CC and lower Eocene Sample 207-1258A-3R-CC.
Genus DICTYOCHA Ehrenberg
Dictyocha bachmanni Dumitricá
Dictyocha bachmanni Dumitricá, 1967, p. 5, pl. 1, figs. 1–17.
Remarks: This very unusual silicoflagellate morphology is a rare exception to a general rule among silicoflagellate skeletons (McCartney and Loper, 1989) that the numbers of struts is equal to the number of basal sides. D. bachmanni has four struts and six basal sides. It appears to be part of an evolutionary lineage that includes Distephanus stauracanthus and, if correct, is one of many examples that illustrate the close biological relationships of the genera Dictyocha and Distephanus. A single specimen was found in Sample 207-1258A-16R-CC. The single occurrence suggests that this could be an aberrant specimen of another taxon, though the specimen was well formed and showed no evidence of skeletal deformity.
Dictyocha fibula Ehrenberg
Dictyocha fibula Ehrenberg, Locker, 1974, p. 636, pl. 1, fig. 6 (= lectotype).
Remarks: Specimens of this taxa were only found in Sample 207-1258A-4R-CC. The specimens were consistent in shape, being small, with a short and thick, almost medusoid, bridge. For a discussion on the species concept for D. fibula used in this study, see McCartney et al. (1995).
Dictyocha spinosa (Deflandre)
Corbisema spinosa Deflandre, 1950, p. 193, figs. 178–182.
Dictyocha spinosa (Deflandre), Glezer, 1970, p. 238, pl. 10, figs. 6–8; McCartney and Wise, 1987, pl. 1, fig. 6; McCartney and Wise, 1990, pl. 2, fig. 2.
Remarks: This taxon was found by Engel and McCartney (2005) to occur in a narrow interval of the Dictyocha hexacantha Zone.
Genus DISTEPHANUS Stohr, 1880
Distephanus crux Ehrenberg
Distephanus crux Ehrenberg, 1840, p. 207; Ehrenberg, 1854, pl. 18, fig. 56; pl. 33(XV), fig. 9.
Genus NAVICULOPSIS Frenguelli, 1940
Naviculopsis biapiculata (Lemmermann)
Dictyocha navicula biapiculata Lemmermann, 1901, p. 258, pl. 10, figs. 14, 15.
Naviculopsis biapiculata (Lemmermann), Bukry, 1978, p. 787, pl. 3, figs. 9, 10; McCartney and Harwood, 1992, p. 825, pl. 1, figs. 3, 7, 8.
Remarks: Naviculopsis biapiculata co-occurs with Naviculopsis constricta, Naviculopsis eobiapiculata, and Naviculopsis foliacea in the interval from Sample 207-1258A-15R-CC through 16R-CC. All four taxa are relatively abundant in that interval but sparse elsewhere. All four taxa had basal rings and spines of similar size and are distinguished one from the other by the size and height of the bridge. N. biapiculata are similar to N. eobiapiculata but have a lower bridge.
Naviculopsis constricta (Schulz)
Dictyocha navicula biapiculata constricta Schulz, 1928, p. 246, fig. 21.
Naviculopsis constricta (Schulz), Bukry, 1975, p. 856, pl. 7, figs. 1, 2; McCartney and Wise, 1987, p. 807, pl. 5, figs. 1, 2; see also fig. 2, p. 807.
Naviculopsis eobiapiculata Bukry
Naviculopsis eobiapiculata Bukry, 1978, p. 878.
Remarks: Naviculopsis eobiapiculata is distinguished from N. biapiculata in having a higher bridge, with the bridge commonly being higher than the width across the basal ring.
Naviculopsis foliacea Deflandre
Naviculopsis foliacea Deflandre, 1950, p. 204, figs. 235–240; McCartney and Wise, 1987, p. 807, pl. 5, figs. 3, 4; see also fig. 2, p. 807.
Remarks: Naviculopsis foliacea is similar to N. constricta but has a much wider bridge.
Naviculopsis lata (Deflandre)
Dictyocha biapiculata lata Deflandre, 1932, p. 500, figs. 30, 31.
Naviculopsis lata (Deflandre), Ling, 1972 (in part), p. 185, pl. 30, figs. 12–14; Bukry, 1975, p. 856, p. 7, fig. 4.
Naviculopsis cf. lata obliqua Bukry
Naviculopsis cf. lata (Deflandre), Sawamura and Otawa, 1979, p. 52, fig. 2 (13); Ling, 1977, pl. 3, fig. 12.
Naviculopsis lata obliqua Bukry, 1982, p. 434.
Remarks: This identification must be considered tentative, as this rare taxon has previously been reported from the lower Miocene of the Pacific (see Bukry, 1982; Ling, 1977). However, it is very similar to the specimen illustrated by Ling (1977) and does not have the more robust skeletal elements and triangular plates where the bridge attaches to the basal ring of N. robusta.
