Model Parameters	Value	Source
Y (Young’s modulus)	1	Normalized in simulation units
v (Poisson ratio)	0.5	Assumption of cell incompressibility (Heer et al., 2017)
h (Tissue thickness)	1	Normalized in simulation units
x0 (Contractile region length along AP axis)	20	Consistent with experimentally observed myosin gradients (Heer et al., 2017)
k (Contractility gradient steepness)	0.5	Consistent with experimentally observed myosin gradients (Heer et al., 2017)
y0 (Contractile region length perpendicular to AP axis)	4	Consistent with experimentally observed myosin gradients (Heer et al., 2017)
M0 (Maximum contractility)	5 (Fig 6B) 3-5 (Fig 6C)	Contractility parameter chosen to produce appropriate furrow morphology (Heer et al., 2017)
kmax (EDGE STIFFNESS)	10	Based on difficulty quantifying edge stiffness in vivo, defaulted to a factor of ten stiffer than surrounding tissue
σ (Network edge thickness)	0.25	Edge thickness chosen to be small relative to mean edge length and cell width
μv (Internal compressibility)	0.0001	Parameter value chosen to ensure volume conservation (Heer et al., 2017)
μs (External shell stiffness)	200	Parameter value chosen to ensure small penetration of containing shell (Heer et al., 2017)
y1 (Contractile region length perpendicular to AP axis in Spn27A Mutant)	7.5	Consistent with experimentally observed myosin gradients (Heer et al., 2017)
kx (Gradient along AP Axis for SP)	0.15	Shallow gradient along AP axis consistent with experimental measurements (Streichan et al., 2018)