We derive underdamped evolution equations for the order-parameter (OP ) strains of a ferroelastic material undergoing a structural transition, using Lagrangian variations with Rayleigh dissipation, and a free energy as a polynomial expansion in the N = n + Nop symmetry-adapted strains. The Nop strain equations are structurally similar in form to the Lagrange-Rayleigh 1D strain dynamics of Bales and Gooding (BG), with 'strain accelerations' proportional to a Laplacian acting on a sum of the free energy strain derivative and frictional strain force. The tensorial St. Venant's elastic compatibility constraints that forbid defects, are used to determine the n non-order-parameter strains in terms of the OP strains, generating anisotropic and long-range OP contributions to the free energy, friction and noise. The same OP equations are obtained by either varying the displacement vector components, or by varying the N strains subject to the Nc compatibility constraints. A Fokker-Planck equation, based on the BG dynamics with noise terms, is set up. The BG dynamics corresponds to a set of nonidentical nonlinear (strain) oscillators labeled by wavevector k, with competing short-and long-range couplings. The oscillators have different 'strain-mass' densities ρ(k) ∼ 1/k 2 and dampings ∼ 1/ρ(k) ∼ k 2 , so the lighter large-k oscillators equilibrate first, corresponding to earlier formation of smaller-scale oriented textures. This produces a sequential-scale scenario for post-quench nucleation, elastic patterning, and hierarchical growth. Neglecting inertial effects yields a late-time dynamics for identifying extremal free energy states, that is of the time-dependent Ginzburg-Landau form, with nonlocal, anisotropic Onsager coefficients, that become constants for special parameter values. We consider in detail the two-dimensional (2D) unit-cell transitions from a triangular to a centered rectangular lattice (Nop = 2, n = 1, Nc = 1); and from a square to a rectangular lattice (Nop = 1, n = 2, Nc = 1) for which the OP compatibility kernel is retarded in time, or frequencydependent in Fourier space (in fact, acoustically resonant in ω/k). We present structural dynamics for all other 2D symmetry-allowed ferroelastic transitions: the procedure is also applicable to the 3D case. Simulations of the BG evolution equations confirm the inherent richness of the static and dynamic texturings, including strain oscillations, domain-wall propagation at near sound speeds, grain-boundary motion, and nonlocal 'elastic photocopying' of imposed local stress patterns.