Eldonia

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Eldonia
Temporal range: Cambrian Stage 3–Middle Ordovician
Eldonia ludwigii.png
Eldonia ludwigii from the middle Cambrian Burgess Shale.
Eldonia ludwigii life restoration.jpg
Life restoration
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Stem group: Ambulacraria
Clade: Cambroernida
Class: Eldonioidea
Family: Eldoniidae
Genus: Eldonia
Walcott 1911
Type species
E. ludwigi
Walcott 1911
Species [1]
  • E. ludwigiWalcott 1911
  • E. eumorphaSun & Hou 1987
  • E. berberaAlessandrello 2003
Synonyms [2]
  • YunnanomedusaSun & Hou 1987
  •  ? †Stellostomites Sun & Hou 1987

Eldonia is an extinct soft-bodied [3] cambroernid [4] best known from the Fossil Ridge outcrops of the Burgess Shale, particularly in the 'Great Eldonia layer' in the Walcott Quarry. [5] In addition to over 550 specimens collected by Walcott, [6] 224 specimens of Eldonia are known from the Greater Phyllopod bed, where they comprise 0.43% of the community.[ citation needed ] Species also occur in the Chengjiang biota, [7] Siberia, [8] and in Upper Ordovician strata of Morocco. [9]

Contents

Description

It takes the form of a round, medusoid disk (which originally led to suggestions of a jellyfish affinity) [7] with a C-shaped gut trace. The gut is recalcitrant and can be extracted using Hydrofluoric acid. [10]

A specimen from the Lower Ordovician Madaoyu Formation in Hunan, South China, can be interpreted as the incomplete body of Eldonia or the similar animal. However, its annulation, the structure of the intestine and the shape of the body are more similar to those of Ottoia . [11]

Classification

Walcott's original interpretation as a holothurian was rapidly disputed. [12] Alternative affinities to be suggested, which did not stand the test of time, included the siphonophores [13] [14] [15] and a coelenterate medusa. [16]

Eldonia and the other Eldoniidae form a clade, Eldonioidea, with the Rotadiscidae and the informal group known as the paropsonemids. [1] The Eldonioidea are, in turn, part of the stem-ambulacrarian clade Cambroernida. [4]

There are three species within Eldonia, [1] although some authors consider E. eumorpha to be a distinct genus, Stellostomites , as S. eumorphus. [17]

Paleoecology

The organism is frequently found in association with the lobopod Microdictyon , which is presumed to have fed on Eldonia. [18]

See also

Related Research Articles

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<span class="mw-page-title-main">Eldonioid</span> Extinct clade of disc-shaped animals

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The Cambroernida are a clade of Paleozoic animals with coiled bodies and filamentous tentacles. They include a number of early to middle Paleozoic genera noted as "bizarre" or "orphan" taxa, meaning that their affinities with other animals, living or extinct, have long been uncertain. While initially defined as an "informal stem group," later work with better-preserved fossils has strengthened the argument for Cambroernida as a monophyletic clade.

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References

Works cited