Table 1.

Dimensions (μm) of putative fossil embryos of distinct morphotypes

Type structure	External dimensions	Outer wall	Inner wall(s)	Archenteron diameter
Fig. 2A	234  × 333	13.4	9.0*	—
	207  × 252	13.5	—	—
	234  × 234	13.5	9.0*	—
	252  × 297	9.0	9.0*	—
Fig. 2C	140  × 140	13.4	6.7	—
	126  × 142	13.4	8.0	—
	135  × 144	13.5; 18†	9.0	—
Fig. 3A	196  × 228	16.1§	—	64
Fig. 3C	—‡	16.2	—	52
Fig. 3E	185  × 202	13.4	—	54
Fig. 3G	189  × 197	18.0	—	46
	207  × 234	18.0	—	—
Fig. 3I	177  × 181	13.0	—	75, 101†
	162  × 193	13.5, 22.5†	—	112
	180  × 180	18.0	—	90
Fig. 3J	131  × 137	18.0	—	78
	144  × 153	10.0	—	63

Measurements were taken from photographic representations of sections and converted to μm by reference to size standards. Short horizontal lines denote features not relevant to specimen, or occluded, or otherwise impossible to measure. 

*Average of several measurements of thickness of wall of multiple in-foldings. 

^†Different regions of wall of different thickness. 

^‡ External dimensions not comparable because section is oblique and above the equator of the embryo [it measured 134.4 × 147.8; on the embryo shown in A, this section (white arrowheads) would have measured 153 μm in diameter]. 

^§The “oral” portions of the wall nearest the archenteron were measured.