Zenaspididae Stensiö, 1958

Voichyshyn, Victor, 2006, New osteostracans from the Lower Devonian terrigenous deposits of Podolia, Ukraine, Acta Palaeontologica Polonica 51 (1), pp. 131-142 : 132

Family Zenaspididae Stensiö, 1958

Type genus: Zenaspis Lankester, 1870 , see below.

Diagnosis.— Zenaspidida of average to large size. The headshield is dome−shaped and massive. The abdominal part of the shield has a low, more or less developed, median dorsal crest. The hypophysial division of the nasohypophysial opening is, as a rule, larger than the nasal division. The pineal plate is feebly developed or absent. The median dorsal field is broad. The lateral fields have a conspicuous dilatation (or widening) in their posterior parts reaching backwards no further than the proximal part of the dorsal surface of the cornual processes. The ornamentation includes either single large tubercles, or groups of tubercles of different size on tesserae.

Genera included.— Diademaspis Janvier, 1985 , and, possibly, Tegaspis Wängsjö, 1952 .

Remarks.—The genus Tegaspis has several features in which it appreciably differs from other zenaspidids, such as the shape of the headshield (its anterior margin and cornual processes), approximately same size of the two divisions of the nasohypophysial opening, a comparatively narrow median dorsal field, and the position of the posterior parts of the lateral fields, which does not extend on the dorsal surface of cornual processes at all.