The first report of a vauxiid sponge from the Cambrian Chengjiang Biota

Abstract

Non-spicular sponges constitute >8% of the extant sponge biodiversity at the species level, yet their evolutionary history is poorly known due to a sparse fossil record. The genus Vauxia, previously only known from middle Cambrian (Miaolingian, Wuliuan) Lagerstätten, was regarded as the earliest fossil record of non-spicular demosponges. Here we describe the first vauxiid sponge, Vauxia leioia new species, from the early Cambrian Chengjiang Biota (Series 2, Stage 3). This sponge exhibits a double-layered fibrous skeleton: the mesh and fiber thickness of the endosomal layer are irregular while the dermal layer, which directly connects with the endosomal skeleton without intermediate supporting fibers, is regular in both aspects. Measurements using scanning electron microscope and Raman spectroscopy revealed that the endosomal fibers are composed of carbonaceous material, but are tomographically indiscernible from the host rock, while the dermal fibers are preserved as impressions without obvious accumulation of carbonaceous material. Although the original composition of the dermal skeleton is now hard to establish, we cannot rule out that it was siliceous. The morphological characters of V. leioia n. sp. represent an intermediate state between other Vauxia species and the recently established vauxiid genus Angulosuspongia. However, more data are required to reconstruct the phylogenetic relationship among these taxa.UUID: http://zoobank.org/0ebb91b8-5dad-420f-bb2c-dc203d37bebd

Revisiting the phosphorite deposit of Fontanarejo (central Spain): new window into the early Cambrian evolution of sponges and the microbial origin of phosphorites

“…The best-known fossil taxon is the middle Cambrian Vauxia from the Burgess Shale, which has recently also been discovered in the lower Cambrian Chengjiang Biota (Series 2, Stage 3) (Luo et al 2020). The presence of chitin in this genus is in good accordance with the skeletal composition of the Verongiida (subclass Verongimorpha) (Ehrlich et al 2013).…”

“…To date, articulated, well-preserved sponge fossils in Burgess-Shale-type preservation and deep-water black shales have only been reported after the beginning of Cambrian Age 3 (e.g. Steiner et al 1993;Luo et al 2020). Furthermore, described three-dimensionally preserved sponge skeletal frames from the basal Niutitang Formation (Stage 2) near Sancha in China that have illuminated the nature of stem-group hexactinellids.…”

Vauxiids as descendants of archaeocyaths: a hypothesis

“…Furthermore, the polygonal (basically hexagonal) meshwork of vauxiid skeletons is morphologically similar to that of the verongiid Aplysina (Cruz-Barraza et al 2012, fig. 2 Some Cambrian sponges, such as Angulosuspongia sinesis from the Kaili Biota and Vauxia leoia from the Chengjiang Biota, exhibit partial to complete silicification of vauxiid-type skeletons (Yang et al 2017a,b;Luo et al 2020). This type of mineralization does not contradict their verongiid affinity because authigenic carbonate and silica have been recently reported from chitinous skeletons of verongiid genera Aplysina, Verongula and Suberea (Ehrlich et al 2010(Ehrlich et al , 2017.…”

“…Archaeocyaths had originally high-magnesium calcitic skeletons, which was altered diagenetically into microgranular low-magnesium calcite (Zhuravlev & Wood 2008); a consistent exception is Dictyocyathus translucidus, whose skeletons are invariably preserved as moulds filled with late-stage coarse cement, implying a primary aragonitic mineralogy (Kruse et al 1995). In turn, vauxiid sponges were thought to be the earliest aspiculate demosponges possessing organic skeletons ('keratose sponges' sensu Minchin (1900); that is, orders Dictyoceratida, Dendroceratida and Verongiida) (Rigby 1986;Ehrlich et al 2013;Luo & Reitner 2014;Botting & Muir 2018;Luo et al 2020).…”

“…Archaeocyaths appeared during the following Cambrian Age 2 in carbonate facies of the Siberian Platform, rapidly diversified there and spread out the carbonate basins of the entire world (Riding & Zhuravlev 1995;Debrenne et al 2015). First representatives of the family Vauxiidae occurred in siliciclastic Lagerstätten of South China of the Cambrian Stage 3, which were formed when archaeocyaths were close to their acme of biodiversity and reef-building activity (Luo et al 2020).…”