New ediacaran rangeomorphs from Mistaken Point, Newfoundland, Canada

Abstract

Hapsidophyllas flexibilis new genus and species and Frondophyllas grandis new genus and species are rare Ediacaran (ca. 565 Ma) rangeomorph forms, herein termed “hapsidophyllids,” which are endemic to Mistaken Point, Newfoundland, Canada. These two taxa are highly disparate in overall morphology, the former being a low-level, multibranched “network of leaves” and the latter a meter-long frond. Despite their dissimilarity in gross morphology, the two genera share a unique flexible, leaflet-type structure with a fine-scale branching structure that resembles that of charnid rangeomorphs. These leaflet structures are unknown from any other rangeomorph or Ediacaran group, and are herein termed “hapsidophyllid leaflets.” Hapsidophyllids grew by an iteration of structural units, with small rangeomorph modules making up the larger hapsidophyllid leaflets, which in turn composed the larger hapsidophyllid organism. The presence of hapsidophyllid leaflets in both Hapsidophyllas and Frondophyllas suggest the two genera were related taxonomically, with their very different gross morphologies reflecting ecological adaptations to exploit different suspension-feeding tiers.