[Invertebrate • 2024] Rhabdopleura chathamica, R. emancipata, ... • Four New Species and A ribosomal Phylogeny of Rhabdopleura (Hemichordata: Graptolithina) from New Zealand, with A Review and Key to all described extant taxa

Rhabdopleura emancipata

Gordon, Quek & Huang, 2024

 DOI: doi.org/10.11646/zootaxa.5424.3.3

 

Abstract

All eight extant species of Rhabdopleura described between 1869 and 2018 are provisionally accepted as valid based on a review of the literature and new data on two little-known species from the Azores. Additionally, four new species are described from the New Zealand region, increasing global diversity by 50%, and a dichotomous key to all 12 described species is provided based on morphological criteria. The distinction between colony morphologies based on erect-tube inception is regarded as particularly helpful in initial characterization of species. Erect ringed tubes are either produced directly from the surface of creeping-tubes or indirectly, i.e. a short adherent side branch from a creeping tube is interpolated between the creeping tube and an erect tube; such side branches are blind-ending. These two modes of erect-tube origination are here respectively termed direct and indirect. Species with indirect erect-tube budding are predominant in the North Atlantic whereas species with direct erect-tube budding dominate in New Zealand waters. The only indirect-erect species from New Zealand, Rhabdopleura chathamica n. sp., was discovered on deepwater coral from 1008‒1075 m, constituting the deepest record of the genus to date. Rhabdopleura emancipata n. sp., collected only in a detached state, constitutes a three-dimensional tangled growth that grew freely into the water column—a unique morphology hitherto unknown among extant species. Owing to this growth mode, it provided a substratum for epibionts from several phyla. Rhabdopleura francesca n. sp. and Rhabdopleura decipula n. sp. are morphologically very similar but are distinguishable by their distinct placements in a phylogeny based on 16S mitochondrial and 18S nuclear rRNA genes. Phylogenetic reconstructions based on rRNA and mitochondrial genome data contribute to an updated phylogeny of all Rhabdopleura species sequenced thus far, some of which require more molecular sequences and morphological analyses for taxonomic determination.

 Hemichordata, Pterobranchia, Rhabdopleurida, mitogenome, erect-tube inception, deepest record epibionts, ribosomal phylogeny

Dennis P. GORDON, Z. B. Randolph QUEK and Danwei HUANG. 2024. Four New Species and A ribosomal Phylogeny of Rhabdopleura (Hemichordata: Graptolithina) from New Zealand, with A Review and Key to all described extant taxa.  Zootaxa. 5424(3); 323-357. DOI: doi.org/10.11646/zootaxa.5424.3.3 [2024-03-14]

[Paleontology • 2023] Rotaciurca superbus • A Silurian pseudocolonial pterobranch

 

Rotaciurca superbus

Briggs & Koch, 2023

DOI: 10.1016/j.cub.2023.10.024

 twitter.com/phyloprog

yale.edu

 

Summary

Pterobranchs, a major group of the phylum Hemichordata, first appear in the fossil record during the Cambrian, and there are more than 600 fossil genera dominated by the mainly planktic graptolites of the Paleozoic, which are widely used as zone fossils for correlating sedimentary rock sequences. Pterobranchs are rare today; they are sessile marine forms represented by Rhabdopleura, which is considered the only living graptolite, and Cephalodiscus. Unlike their sister taxon, the colonial graptolites, cephalodiscids are pseudocolonial. Here, we describe a problematic fossil from the Silurian (Pridoli) Bertie Group of Ontario (420 mya), a sequence of near-shore sediments well known for its remarkably preserved diversity of eurypterids (sea scorpions).5 The fossil, Rotaciurca superbus, a new genus and species, was familiarly known as Ezekiel’s Wheel,5 with reference to the unusual circular arrangement of the tubes that compose it. The structure and arrangement of the tubes identify Rotaciurca as a pterobranch, and phylogenetic analysis groups it with the cephalodiscids. We place it in a new family Ezekielidae to distinguish it from Cephalodiscidae. A large structure associated with the tubes is interpreted as a float, which would distinguish Rotaciurca as the only known planktic cephalodiscid—thus cephalodiscids, like the graptolites, invaded the water column. This mode of life reflects the rarity of pseudocolonial macroinvertebrates in planktic ocean communities, a role occupied by the tunicates (Chordata) known as salps today. Our estimates of divergence times, the first using relaxed total-evidence clocks, date the origins of both hemichordates and pterobranchs to the earliest Cambrian (Fortunian).

 Derek E.G. Briggs and Nicolás Mongiardino Koch. 2023. A Silurian pseudocolonial pterobranch. Current Biology. In Press, DOI: 10.1016/j.cub.2023.10.024

 twitter.com/phyloprog/status/1721620500244582805

The last turn of ‘Ezekiel’s Wheel’ honors a Yale-affiliated fossil hunter

Yale paleontologists have identified a “problematic” fossil as an ancient sea creature that lived in the plankton 420 million years ago.

 news.yale.edu/2023/11/06/last-turn-ezekiels-wheel-honors-yale-affiliated-fossil-hunter