Pustulobolus, Skovsted & Knight & Balthasar & Boyce, 2017

Skovsted, C. B., Knight, I., Balthasar, U. & Boyce, W. D., 2017, Depth related brachiopod faunas from the lower Cambrian Forteau Formation of southern Labrador and western Newfoundland, Canada, Palaeontologia Electronica (Oxford, England: 1990) 17 (15), pp. 1-52 : 29-32

Genus PUSTULOBOLUS n. gen.

zoobank.org/ 0FC76582-4109-4D2E-B1F9-8EAF8C34011C

Type species. Pustulobolus triangulus n. gen et. sp.

Diagnosis. Shell dorsibiconvex, strongly inequivalved linguliform brachiopod; larval shells small, subcircular with pitted microornament; adult valve exterior with anteriorly extended, spine like pustules increasing in size anteriorly; ventral valve with sharply pointed triangular posterior and rounded anterior margins with large orthocline pseudointerarea with narrow pedicle furrow and well developed flexurelines; adult external ornament covering ventral pseudointerareas lateral to flexurelines; dorsal valve subcircular with narrow, linear pseudointerarea, and low median ridge. Differ from Eoobolus by the larger pustules of the adult ornament, the larger size of the ventral pseudointerarea and the smaller pseudointerarea of the dorsal valve. Differ from Spinobolus by the denser distribution of spine like pustules and the larger ventral pseudointerarea. Differ from Botsfordia and other acrotheloids by the large, orthocline ventral pseudointerarea. Differ from Lingulellotreta by the pustulose adult ornament and the ventral pseudointerarea lacking a pedicle tube throughout ontogeny.

Etymology. The name is derived from the characteristic pustulose ornament of the adult shell and ventral pseudointerarea.

Remarks. Pustulobolus exhibits a peculiar combination of characters otherwise associated with different Cambrian linguliforms. The external ornament and the morphology of the dorsal valve interior is extremely similar to that of the acrotheloid genus Botsfordia , while the larval shell, ventral valve exterior, and the shape of the ventral pseudointerarea is more closely comparable to the linguloid genus Eoobolus , and the posteriorly extended ventral pseudointerarea is reminiscent of Lingulellotreta (see Li and Holmer, 2004) while the spine-like pustules of the adult ornament is reminiscent of Spinobolus (see Zhang et al., 2016). This combination of characters is previously unknown in any brachiopod genus, a fact that in combination with the unique presence of the adult pustulose ornament on parts of the ventral pseudointerarea, justifies the introduction of the new generic name Pustulobolus .

Although the new genus exhibits a combination of characters associated with brachiopods of several different families, the most obvious similarities are to Eoobolus and we include Pustulobolus in the family Eoobolidae . The Eoobolidae , which is characterized by having a pitted larval and a pustulose adult shell, has been suggested to be closely related to the similarly ornamented acrotheloid brachiopods, most notably the Botsfordidae ( Holmer et al., 1996). As discussed above, the new genus from the Forteau Formation share characters associated with genera of both families (i.e., Eoobolus and Botsfordia ). To some extent Pustulobolus represents an intermediate condition between Eoobolus and Botsfordia , and the new genus could be interpreted to fill a position in a morphological continuum between the Eoobolidae and the Botsfordidae. The similarities of Pustulobolus with Lingulotreta and Spinobolus are limited to the large ventral pseudointerarea and the spine like pustules respectively and these similarities probably reflects convergence rather than close phylogenetic relationships.