Article: Cortezorthinae, a new subfamily of Siluro–Devonian dalmanellid

Cortezorthinae is proposed for the Siegenian-Eifelian septate dalmanellid Cortezorthis gen. nov., its Silurian to Lower Devonian aseptate precursor Protocortezorthis gen. nov., and their derivatives, Reeftonia Allan and Cariniferella Schuchert and Cooper. New species are Protocortezorthis windmillensis and Cortezorthis cortezensis from Nevada and Cortezorthis maclareni and C. bathurstensis from the Canadian Arctic. Cortezorthis maclareni is type species of Cortezorthis; 'Dalmanella' fornicatimcurvata is designated type species of Protocortezorthis,Protocortezorthis windmillensis is a temporal and morphologic intermediate between fully differentiated members of Protocortezorthis and of Cortezorthis. Its incipient median septum is recapitulated in early growth stages of Cortezorthis, and its dorsal adductor field is variable between patterns typical of both older and younger forms.The new subfamily Cortezorthinae arose from an as yet undesignated Silurian species of Isorthis. The Silurian members of Protocortezorthis developed distinctive ventral musculature, in part reminiscent of the rhipidomellids. The Devonian members of the Cortezorthinae (Cortezorthis, Reeftonia, and Cariniferella) evolved away from standard isorthoid muscle patterns and also showed some convergence toward rhipidomellid internal morphology.