Triangular flexed and flanged teeth have a prominent angular flexure of one or both margins
(Figure 61).
The width of the flexure is at least 0.2 the length of the maximum tooth width. Like Tofino Basin triangular flanged teeth, triangular flexed teeth have a cutting edge (occlusal crest) that traverses the apex and tooth crown margins and may traverse the tooth base margins
(Figure 47). At the tooth margins, the occlusal crest may be broad or flanged.
Damaged (unidentified) flanged teeth (8 specimens) were mainly from the Pluto I-87 well and the base of the Zeus D-14 well (upper Eocene/Oligocene or lower Miocene). They could be specimens of triangle double flex Dunsworth et al. 1975, centrally inflated triangle with canals new subtype, or narrow triangle straight inbase Doyle et al. 1974.
List of identified triangular flexed teeth:
cf. flexed triangle asymmetric Doyle and Riedel 1985b
wide triangle double flex Gupta 1991
triangle double flex Dunsworth et al. 1975; emend. Doyle and Riedel 1979a
cf. flexed triangle asymmetric
Doyle and Riedel 1985b,
p. 357-358
Figure 62
a8/b5+8/c1,2/d1,2/e120-150°/f25-30°/g1,2/h1,2/i2
Characters: Tooth triangular; one margin longer than other; margins both with prominent flexure; flexure closer to apex with greatest angle (about 150°) and gently rounded; flexure closest to base angled (120-130°); inline base or inline transverse line shallowly curved, concave-down, and at or below flexure bases; inline apex high in apical region and shape similar to outline; apical angle 25-35°; taller than wide, height to width ratio about 2:1; slightly asymmetric-elliptical (one face slightly flatter) and acute laterally in cross-section; slightly inflated basally; margins straight with occlusal lateral flanges.
Remarks: This specimen shows several similarities to flexed triangle asymmetric especially in the nature of the flexed margins and the asymmetry in the relationship of the margins to the inline that is common to many of the flexed triangle subtypes. Flexed triangle asymmetric occurs in the Paleocene and earliest Eocene (Doyle and Riedel 1985b). The Hesquiat Peninsula specimen differs from flexed triangle asymmetric by having: 1) two flexures; 2) one flexure nearer the apex that is curved and with a larger angle at about 150°; 3) a second basal flexure angled at about 120-130°; 4) two straight margins; and 5) a higher inline apex. This specimen only differs from triangle double flex Dunsworth et al. 1975 by having two flexes that are different and not at the same basal level.
Occurrence: 1 specimen; Hesquiat Peninsula; Oligocene; sample may be reworked.
wide triangle double flex Gupta 1991, p. 24
Figure 63
a8/b5+8/c2/d1,2/e90-115°/f35-40°/g1,2/h4/i≤1.5
Remarks: Tofino Basin teeth are triangular, symmetric-elliptical and acute laterally in cross-section, and taller than wide (ratio about 1.5:1). Both tooth basal margins have angled flexure (angle about 90-115°) and each terminate below the inline base/transverse line. The apical angle is about 35-40°. Tooth margins have occlusal lateral flanges. The inline is high (near outline apex) and a similar shape to the outline.
Wide triangle double flex differs from triangle double flex Dunsworth et al. 1975 by having a greater apical angle (35-40°) and a height to width ratio of about 1.5:1 or less. Wide triangle double flex is known from Paleocene and Eocene deep-sea core strata, central Indian Ocean.
Occurrence: 4 specimens, 1 questionable specimen; Nootka Island, Hesquiat Peninsula, and offshore well Shell-Anglo Pluto I-87; Centrally Inflated Triangle With Canals ichthyolith interval; upper Eocene and Oligocene.
triangle double flex
Dunsworth et al. 1975, p. 857
emend. Doyle and Riedel 1979a, p. 71
Figure 64
a8/b5+8/c2/d1,2/e90-130°/f25-35°/g1,2/h1,4/i≥1.5
Remarks: Tofino Basin teeth are triangular, symmetric-elliptical and acute laterally in cross-section, and taller than wide (commonly >2:1; may be ≥1.5:1). Both tooth basal margins have angled flexure (angle about 90-130°) and each terminate below the inline base/transverse line. The apical angle is about 25-35°. The margins have occlusal lateral flanges. The inline is high (near outline apex) and a similar shape to the outline.
Triangle double flex is known to occur in the middle Eocene through the middle Miocene (Doyle and Riedel 1979a, p. 70).
Occurrence: 4 specimens; Nootka Island, Hesquiat Peninsula, and offshore well Shell-Anglo Zeus D-14; Centrally Inflated Triangle With Canals ichthyolith interval; upper Eocene and Oligocene, reworked in lower Miocene.
