Eglonaspididae is a family of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula.

Amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothoracic armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked, in the case of elgonaspidids, very much like a hot water bottle with or without a pair of small, degenerated eyes and a simple, slit-like mouth positioned at the anteriormost portion of the cephalothoracic armor.

Eglonaspis has a flattened, triangular-shaped cephalothoracic shield with large, crenulated fringes at the posteriolateral ends, and an elongated, tube-like head.

The head of Eglonaspis has degenerated into a tube-like mouth which, according to researchers, is hypothesized to have permitted the living animal to filter-feed particles in the water column just above the surface of the substrate while the animal stayed buried beneath the substrate.

Enough of the fragment permits researchers to hypothesize that the complete cephalothorax would have been shaped like a hot water bottle, possibly with crenulated lateral wing-like extensions, and would have had a small tab-shaped head with small eyes.