''Eocyathispongia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of sponge-like organisms which lived in the

Ediacaran The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last ...

period about 60 million years before the

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

. The current fossil record has found this genus in only one location, the

Doushantuo Formation The Doushantuo Formation (formerly transcribed as Toushantuo or Toushantou, from ) is a geological formation in western Hubei, eastern Guizhou, southern Shaanxi, central Jiangxi, and other localities in China. It is known for the fossil Lagers ...

in Guizhou, China.Behrensmeyer, A. K., and A. Turner. 2013. Eocyathispongia. ''Fossilworks'', https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=324165. It lived in the shallow parts of seas, filter feeding.

Description

As of yet, only one fossil of the genus has been found, but it was excellently preserved. The specific attributes for this genus have yet to be confirmed until more specimens are found.

''Eocyathispongia qiania''

''Eocyathispongia qiania'' is the only species in the ''Eocyathispongia'' genus. It was an

epifaunal Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and ''funga'', respectively. Flora, fauna, funga and other forms of life are collectively r ...

filter feeder that consisted of three tubes, with two smaller side tubes that were likely used to filter water in, and a large, twisted centre tube which was likely used to filter the water out. The cells inside the tubes are flat and porous, as would be expected in a filter feeder. The cells located on the bottom of the fossil are less porous and were likely used to keep the animal grounded, and the cells on the outside of the tube differ from those on the inside. The creature is asymmetrical. The fossil found was only about 1.1 millimeters tall and 1.2 millimeters wide, so it can be assumed that the species as a whole would be about the same size since there's no evidence indicating that the fossil found was not a fully grown specimen.

Doushantuo Formation

This is the location where the specimen was discovered. This formation consists of the shallow waters of the Ediacaran and the rocks are made up of six layers of

phosphorite Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock that contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxi ...

and dolomite. The fossil was found in a phosphorite rock near the lower layer of the rock formation. The specimen was fossilized through

lithification Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithificati ...

Etymology

The name of the genus combines the Greek root ''eo-'' meaning dawn, and the Greek word for cup-shaped, ''cyathifer'', to describe what the creature looks like. The word ''spongia'' was added to indicate that the genus is assessed as a sponge.

Relationship and significance

The specimen found is surprisingly similar to sponges alive today. The cellular structure is almost identical to some modern-day sponges, and the less porous basal side is also more consistent with modern sponges alive today. However, because its combination of traits does not resemble any one of the four extant classes of

Porifera Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a Basal (phylogenetics) , basal clade and a sister taxon of the Eumetazoa , diploblasts. They are sessility (motility) , sessile ...

, Yin et al. (2015) assign it to the

stem group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

relative to all living sponges. This genus, if it is indeed a sponge, is significant mostly for the time period it was alive in. Until the discovery of this creature, the existence of sponges in the Ediacaran was only theoretical. The specimen found is nevertheless a problem for theories of early sponge evolution, because all members of the sponge

crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor ...

have a specific type of cell in their inner wall called

choanocytes Choanocytes (also known as "collar cells") are cells that line the interior of asconoid, syconoid and leuconoid body types of sponges that contain a central flagellum, or ''cilium,'' surrounded by a collar of microvilli which are connected by ...

, which are believed to be inherited from the

choanoflagellate Choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of animals. The name refers to the characteristic funnel-shaped "collar" of interconnected microvilli and ...

ancestor of all animals. So it was expected they would be found in "even stem group sponges", but there's no significant evidence to show that the specimen had any of these cells. Cavalier-Smith (2017) challenges the assignment of ''Eocyathispongia'' to the Porifera since, unlike sponges, it "lacks evidence for an quiferous system the tiny putative intercellular spaces being insufficient evidence for ostia and nternal waterchannels penetrating the body wall". Instead he interprets the animal as a "presponge" and groups it with the enigmatic fossil ''

Funisia ''Funisisa'' is a genus of extinct, colonial sponge-like organisms from the late Ediacaran of South Australia. It is a monotypic genus, containing only ''Funisisa dorothea''. Discovery and naming The fossil material of ''Funisia'' was found ...

'' into the Varisarca, a 'non-quilted' subphylum within the oldest animal phylum

Vendozoa Vendobionts or Vendozoans (Vendobionta) are a proposed very high-level, extinct clade of benthic organisms that made up of the majority of the organisms that were part of the Ediacaran biota. It is a hypothetical group. It would be the oldest of ...

(contrasting with the 'quilted' subphylum

Petalonamae The petalonamids (Petalonamae) are an extinct group of archaic animals typical of the Ediacaran biota, also called frondomorphs, dating from approximately 635 million years ago to 516 million years ago. They are benthic and motionless animals, t ...

). If this is correct, ''Eocyathispongia'' is not phylogenetically a member of the sponge line but represents an evolutionary grade out of which ancestral sponges arose.

References