2D Shapes for Outlines and Cross-sections (with reference to appropriate 3D shapes)

Choose the shape state that most resembles the two-dimensional disseminule outline or cross-section (excluding appendages such as spines or bristles or shallow indentations such as notches). Your disseminule need not match the state drawing exactly, as each drawing may represent a range of shapes.

+/- round

elliptic/

biconvex

fusiform

ovate/obovate

lanceolate/ oblanceolate

linear to oblong

circular
Sometimes notched. When one side of the notch conspicuously protrudes, the 2D structure may be called comma-shaped. 3D equivalents of round are globose, orbicular and spherical.

widest at the middle, biconvex (right) has pointier ends
Related terms are lenticular (referring to the 3D shape made up of 2 biconvex surfaces or to its cross-section) and discoid (when the surfaces are more parallel than convex).

tapering at both ends,
spindle-shaped
Most often used to refer to the cross-section of the 3D shape that is flattened ovoid with an extended marginal rim.

tapering at one end,
egg-shaped
Ovate is widest at the bottom (shown); obovate at the top. The 3D shape is referred to as ovoid. When the narrow end is pointed, conical is used to refer to the 3D shape.

narrower than ovate Lanceolate is widest at the bottom; oblanceolate at the top. The 3D shape is referred to as lanceoloid. When one end is pointed (left), the term teardrop-shaped is sometimes used.

opposite sides are
+/- parallel
Shapes range from linear (left) to narrowly oblong to squarish oblong (right).

triangular

sector-shaped

polygonal

trullate/obtrullate

D-shaped/

C-shaped/reniform

bilobed

3-sided — all sides flat
Narrow triangles are sometimes referred to as cuneate or cuneiform. Entities with triangular cross-sections are often referred to as trigonous.

2 flat & 1 curved sides, slice-of-pie-shaped
3D structures with 2 flat and 1 curved surfaces are called sectoroid and typically represent a wedge-shaped slice taken from an ovoid or globose structure.

4- to 5-sided, not necessarily symmetrical
Includes rhombic or diamond-shaped.

trowel-shaped, bilaterally symmetrical, similar to ovate/obovate except that the sides are flatter

1 side convex and the opposite side either flat (for D-shaped or plano-convex) or concave (C-shaped to reniform), not necessarily symmetrical

2 roundish ends joined by a narrower segment
This shape occurs in cross-sections of 3D structures with 2 opposing concave surfaces.