The style of embryonic development in the lingulids has changed through time; that of Recent lingulids is not primitive for the group. The shell of Devonian lingulids consists of two valves already at the embryonic stage, whereas in Recent hngulids the protegulum originates as a single plate, subsequently folded in two. The protegulum of the Devonian
lingulids is a cup-shaped, subcircular plate, usually with a characteristic radial sculpture suggesting the presence of marginal setae, similar to those occurring in early juvenile stages of Recent discinids. Devonian protegula are 81 to 100 ym in width and thus are three times smaller than protegula of the Recent Lingula and Glottidia and twice as small
as those of the Late Cretaceous Lingula sp. The embryonic development of linulids underwent important modification during last 370 Ma.

Key words: Lingulidae, protegulum, ontogenetic development, Late Devonian.

Andrzej Baliński, Instytut Paleobiologii PAN, uul. Twarda 51/55, PL-00-114 Warszawa, Poland.