Gracilithecidae Syssoiev, 1972

Malinky, John M. & Skovsted, Christian B., 2004, Hyoliths and small shelly fossils from the Lower Cambrian of North-East Greenland, Acta Palaeontologica Polonica 49 (4), pp. 551-578 : 565

Family Gracilithecidae Syssoiev, 1972 Genus Gracilitheca Syssoiev, 1968

Diagnosis.—Orthothecid hyolith with shallow ventral furrow, grading into blunt lateral edges that extend to form a distinct protrusion along the entire length of the lateral edges of the conch (emended from Syssoiev 1968: 39).

Remarks.—Representatives of this genus are distinguished by a conch with a pronounced triangular cross−section that includes longitudinal protuberances extending from each lateral edge, and extending for the entire length of the conch. The type species, G. ternata Syssoiev, 1968 is known only from an impression of the venter, but the presence of the protuberances is beyond question.

Stratigraphic range and distribution.—Lower Cambrian; eastern Canada ( Matthew 1899), England ( Cobbold 1921), Siberian Platform ( Syssoiev 1968; Val’kov 1975, 1987), Morocco ( Marek et al. 1997), and North−East Greenland.