Dawn of complex animal food webs: A new predatory anthozoan (Cnidaria) from Cambrian

Abstract

Cnidarians diverged very early in animal evolution; therefore, investigations of the morphology and trophic levels of early fossil cnidarians may provide critical insights into the evolution of metazoans and the origin of modern marine food webs. However, there has been a lack of unambiguous anthozoan cnidarians from Ediacaran assemblages, and undoubted anthozoans from the Cambrian radiation of metazoans are very rare and lacking in ecological evidence. Here, we report a new polypoid cnidarian, Nailiana elegans gen. et sp. nov., represented by multiple solitary specimens from the early Cambrian Chengjiang biota (∼520 Ma) of South China. These specimens show eight unbranched tentacles surrounding a single opening into the gastric cavity, which may have born multiple mesenteries. Thus, N . elegans displays a level of organization similar to that of extant cnidarians. Phylogenetic analyses place N . elegans in the stem lineage of Anthozoa and suggest that the ancestral anthozoan was a soft-bodied, solitary polyp showing octoradial symmetry. Moreover, one specimen of the new polyp preserves evidence of predation on an epifaunal lingulid brachiopod. This case provides the oldest direct evidence of macrophagous predation, the advent of which may have triggered the emergence of complex trophic/ecological relationships in Cambrian marine communities and spurred the explosive radiation of animal body plans.

Exceptional soft tissue preservation reveals a cnidarian affinity for a Cambrian phosphatic tubicolous enigma

“…Other taxa known from the Cambrian suggest that many gastric septa are the likely plesiomorphic condition for the cnidarian total group, with approximately 28 such septa present in the stem medusozoan Conicula striata [ 36 ] and 18 gastric septa in dinomischiids [ 32 ]. Regardless of competing interpretations of the latter as either stem ctenophores [ 32 ] or stem cnidarians [ 37 , 38 ] these taxa lie outside of the cnidarian crown group, and likewise suggest that in excess of 10 septa is plesiomorphic, with the four present in crown medusozoans representing a reduction.…”

Anatomy, palaeoautecology and phylogenetic affinity of tubular Glossolites magnus from the early Cambrian Chengjiang biota, South China

“…Glossolites magnus is also similar to the newly discovered Nailiana elegans , but can be easily distinguished from the latter in the possession of a septum, and a broadly conical, chitinous body without closely spaced longitudinal grooves or stripes on the body surface (Ou et al . 2021).…”

Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development

“…The one fossil suggested to represent the soft-tissue preservation of a pterobranch zooid itself, Galeaplumosus (Hou et al, 2011), has subsequently been redescribed as one of the arms of the anemone-like animal Xianguangia (Ou et al, 2017). Xianguangia itself, has since been debated as either a benthic ctenophore (Zhao et al, 2019b) or cnidarian (Ou et al, 2022); neither assignment is relevant to deuterostome origins, but the debate itself underscores the labile nature of both the tissues and phylogenetic placements of early Paleozoic problematica. This lack of zooid preservation poses significant problems for reconstructing the early evolution of the pterobranchia.…”