Blackwelderia biaverta, Opik, 1967, Opik, 1967

Smith, Patrick M., Paterson, John R. & Brock, Glenn A., 2018, Trilobites and agnostids from the Goyder Formation (Cambrian Series 3, Guzhangian; Mindyallan), Amadeus Basin, central Australia, Zootaxa 4396 (1), pp. 1-67 : 50

Biaverta Öpik, 1967

Type species. Biaverta biaverta Öpik, 1967 .

Discussion. Öpik (1967) originally placed Biaverta Öpik, 1967 in the Menomoniidae Walcott, 1916 based on its concave preglabellar field, large, strongly convex palpebral and posterior areas, deep glabellar furrows that widen (exsag.) slightly adaxially, and anteriorly situated palpebral lobes. Bentley et al. (2009) suggested that Biaverta was better placed in the Nepeidae Whitehouse, 1939 rather than the Menomoniidae (Öpik 1967; Wang, et al. 1989). The characteristics used by Paterson (2005) to define the Nepeidae exclude Biaverta because it lacked a number of key features, including: distinctive palpebral lobes; prominent bifurcating eye ridges; and a preglabellar boss. However, Westrop & Adrain (2009) conducted a cladistic analysis, which revealed Biaverta as an ingroup member of the Nepeidae . This result was largely based on the shared deep lateral glabellar furrows, large, convex palpebral and posterior areas, and a posterior border furrow that is deep abaxially, but shallows at the steep downturn near the extremities of the posterolateral projections.