Rhaptagnostus, Whitehouse, 1936

Taylor, John F., Loch, James D. & Repetski, John E., 2024, Taxonomy and stratigraphic distribution of Lotagnostus (Agnostida: Agnostidae) and associated trilobites and conodonts in the Upper Cambrian (Furongian) of Laurentia, Zootaxa 5422 (1), pp. 1-66 : 54

Rhaptagnostus cf. R. convergens ( Palmer, 1955)

( Plate 7.4–7.6 )

Discussion. One largely effaced, subelliptical cephalon in collection 5/22/08B displays the forward placement of the glabellar node between the anterolateral lobes of M3 (the papillionate condition), thereby conforming to the diagnosis of Rhaptagnostus ( Shergold & Laurie, 1997) . In most respects it resembles R. convergens ( Palmer, 1955) , but is more elongate and the median preglabellar furrow is less uniformly impressed, deepest in front of the glabella, shallowing anteriorly and does not reach the border furrow. It also closely resembles R. papilio ( Shergold, 1971) , but that species has much smaller basal glabellar lobes. Given these differences, and lack of an associated pygidium in the collection, the Windfall species is left in open nomenclature.

Figures

PLATE 7. Miscellaneous Windfall taxa.Each white scale bar represents 2mm. 1-3. Lotagnostus cf. L. obscurus. USMN 775722, cephalon, from D3362-CO, dorsal, anterior, and left lateral views. 4-6. Rhaptagnostus cf. R. convergens. Cephalon, CM 41350, from 5/22/08B, dorsal, anterior, and right lateral views. 7-9. Lotagnostus cf. L. obscurus. Cephalon, CM 41351, from 5/22/08B, dorsal, anterior, and right lateral views. 10-12. Homagnostus?. Pygidium, CM 41356, from 5/22/08B, dorsal, posterior, and left lateral views. 13-15. Lotagnostus cf. L. obscurus. Pygidium, CM 41353, from 5/22/08B, dorsal, posterior, and left lateral views. 16. Homagnostus? sp. Pygidium, CM 41401, from 5/22/08B, dorsal view. 17-18. Micragnostus cf. M. intermedius. Cephalon, CM 41358, from 5/22/08B, left lateral and dorsal views. 19. Hedinaspis sp. Fragmentary thoracic and/or pygidial fragment, CM 41359, from 5/22/08C, dorsal view. 20. Machairagnostus cf. M. corrugatus. Pygidium, CM 41349, from 5/22/08B, dorsal view. 21-22. Homagnostus? sp. Cephalon, CM 41357, from 5/22/08B, dorsal and anterior views.