Rotaciurca

{{Short description|Extinct genus of pterobranch}} {{Speciesbox | fossil_range = Late Silurian, {{fossil range|420}} | image = | image_caption = | display_parents = 3 | grandparent_authority = Briggs & Mongiardino Koch, 2023 | genus = Rotaciurca | parent_authority = Briggs & Mongiardino Koch, 2023 | species = superbus | authority = Briggs & Mongiardino Koch, 2023 }}

'''''Rotaciurca''''' is an extinct genus of Silurian cephalodiscid pterobranchs. The genus contains a single species, '''''Rotaciurca superbus''''', known from the Bertie Group of Ontario, Canada.<ref name="Briggs and Koch">{{cite journal |last1=Briggs |first1=Derek E.G. |last2=Mongiardino Koch |first2=Nicolás |title=A Silurian pseudocolonial pterobranch |journal=Current Biology |date=4 December 2023 |volume=33 |issue=23 |pages=5225–5232 |doi=10.1016/j.cub.2023.10.024 |pmid=37935193 |bibcode=2023CBio...33E5225B |doi-access=free }}</ref><ref name="Shelton">{{Cite news |last=Shelton |first=Jim |date=2023-11-06 |title=The last turn of 'Ezekiel's Wheel' honors a Yale-affiliated fossil hunter |url=https://news.yale.edu/2023/11/06/last-turn-ezekiels-wheel-honors-yale-affiliated-fossil-hunter |access-date=2024-04-22 |language=en}}</ref>

== Description ==

''Rotaciurca'' is a pseudocolonial (containing multiple clustered individuals which are not connected) pterobranch, unique for being a cephalodiscid rather than a graptolite. The cluster consists of a ring of radiating tubes, likely containing the living individuals, attached to a conical structure interpreted as a float, giving the original fossil the nickname of "Ezekiel's wheel".<ref name="Shelton"/> The whole organism is roughly {{cvt|4|cm}} long, seemingly with two distinct rows of tubes. Its pterobranch affinity is confirmed by lineations within the tubes, which are traces of fuselli, and the irregular arrangement of these group it with the cephalodiscids. ''Rotaciurca'' has a number of similarities to ''Yuknessia'', another enigmatic fossil recently described as a pterobranch, including rigid and similarly sized tubes, although those of ''Yuknessia'' are much finer and have more tightly packed fuselli.<ref name="Briggs and Koch"/>

== Ecology ==

''Rotaciurca'' has been interpreted as a planktonic filter-feeder, with the conical float providing buoyancy like that of a Portuguese man o' war. It is unique in this aspect, as all other known cephalodiscids are benthic and sessile, while the only other planktonic pterobranchs are graptolites, which shows the water column was colonised several times by hemichordates.<ref name="Briggs and Koch"/>

== Distribution ==

''Rotaciurca'' is known from ten specimens, with the holotype nearly complete. Unusually for a planktonic animal, it has only been found in one locality, that being the Bertie Group, however since it was likely soft-bodied, the exceptional preservation of this site may have been necessary for ''Rotaciurca'' to fossilise.<ref name="Briggs and Koch"/>

== Etymology ==

''Rotaciurca'' is named in honour of Samuel J. Ciurca, Jr., who donated thousands of eurypterid fossils to the Yale Peabody Museum, alongside the Latin word ''rota'', meaning "wheel". Its specific name, ''superbus'', from the Latin word meaning "beautiful", acknowledges that Ciurca labelled the holotype fossil "the most beautiful fossil ever found".<ref name="Briggs and Koch"/>

== References ==

Category:Silurian Ontario † Category:Fossil taxa described in 2023 Category:Prehistoric hemichordate genera