There are several other families with members sharing the common name dory, some of which—i.e., those of genera Capromimus, Cyttomimus, and Cyttus—were once treated within the Zeidae. The first two genera are now found within the Zenionidae (or Zeniontidae), and the last genus has been given its own family, Cyttidae.
The pelvic fins are thoracic, spineless, and greatly elongated; the rays are free of their membranes distally. The pectoral fins are small, short, and rounded, inserted fairly low on the body and posterior to the pelvics. The anal fin contains 1–4 spines anteriorly and 20–39 soft rays with their height, direction, origin, and terminus mirroring those of the soft dorsal fin. Along the belly are a series of spinous scutes—scales modified into hard, bony plates—forming an armoured ventral keel. Similar scutes also cover the base of the dorsal and anal fins. The opercular bones are free of any spines or serrations. The vertebrae number 29–34, and adults possess degenerate gill rakers.
The body is apparently naked; if present, the scales are microscopic. Coloration in life is typically a highly lustrous silver, with younger dories covered in a number of randomly-placed dark, dusky spots. These spots tend to fade with age; the largest (and oldest) specimens have only one dark spot, located roughly central on the flanks. In the cape dory (Zeus capensis) this spot is located just below the junction of the spinuos and soft dorsal fins; in the John dory the spot is central and surrounded by a yellow ring, with the body also covered in cloud-like splotches of muddy sepia. Zeus capensis and Z. faber are tied as the largest dory species at a maximum 90 centimetres total length, with the other three species only slightly smaller.
As benthic fish, dories are typically found close to or directly over the sea bottom, but occasionally in midwater as well. Depths frequented are moderate, from ca. 50–800 metres; muddy substrates are preferred, usually over the continental shelf and slope, near the coast. Some, such as the silvery John dory (Zenopsis conchifera), form small and loose schools; while others, such as the John dory, are generally solitary when not spawning. Dories are poor swimmers; they propel themselves primarily via a balistiform (i.e., like the triggerfishs) mode of locomotion, with the dorsal and anal fins undulating in unison as the main propulsive force and the pectoral fins used for stabilisation and turning.
The reproduction of the Zeidae are not well studied as a whole; all are assumed to be non-guarding, substrate scatterers; that is, a large number of tiny eggs and sperm are released en mass and scattered over a wide area. The fertilized eggs are negatively buoyant and sink into the substrate, to which they adhere. Spawning activity appears to peak in the summer months in the John dory, and in the winter months in the mirror dory (Zenopsis nebulosa). In the latter species fertilization is reported to be internal (within the oviduct), whereas in the former species it is external. Growth is rapid and sexual maturity is reached by 3–4 years.
The Zeidae are top predators in their habitat and are noted for their marked stenophagy: juveniles feed exclusively on zooplankton, such as copepods, euphausiids, mysids, apheids, pandalids, palaemonids, and other small crustaceans. Conversely, adults feed almost exclusively on active schooling fish, such as pearlsides, porgies, young carangids (e.g., mackerels), and clupeids (e.g., sardines and pilchards); and other benthic fish, such as dragonets, gobies, filefish, flatfish, bandfish, and sea chubs; and occasionally on cephalopods such as squid and cuttlefish.