Soluta (echinoderm)

Soluta is an extinct class of echinoderms that lived from the Middle Cambrian to the Early Devonian.[1] The class is also known by its junior synonym Homoiostelea. Soluta is one of the four "carpoid" classes, alongside Ctenocystoidea, Cincta, and Stylophora, which made up the obsolete subphylum Homalozoa. Solutes (or solutans) were asymmetric animals with a stereom skeleton and two appendages, an arm extending anteriorly and a posterior appendage called a homoiostele.

For the beetle, see Soluta gramineoides.

Soluta
Temporal range: Drumian – Lower Devonian
Fossil specimen of Coleicarpus sprinklei
Scientific classification
Kingdom: Animalia
Superphylum: Deuterostomia
Clade: Ambulacraria
Phylum: Echinodermata
Class: †Soluta
Jaekel, 1901
Orders
  • †Syringocrinida
  • †Dendrocystitida

Biology

Most solutes were free-living, but the basal solutan Coleicarpus used its homoiostele as a holdfast, as did juvenile Castericystis.[2][3]

Classification
 

Coleicarpus

 
 
 

Castericystis

 
 

Minervaecystis

 
 
 

Girvanicystis

 
 

Dendrocystites

 
 
 

Maennilia

 
 

Heckericystis

 
 
 
 

Dendrocystoides

 
 
 

Claritacarpus

 
 
 

Rutroclypeus

 
 
 
 

Iowacystis

 
 

Scalenocystites

 
 
 
 

Syringocrinus

 
 
 

Myeinocystites

 
 

Belemnocystites

 
 
 
 
 
 
 
 
 
Phylogenetic relationships within Soluta[4]

The phylogenetic position of Soluta is contentious. Solutans are widely agreed to be echinoderms, though the outmoded[5] calcichordate hypothesis held that they were ancestral to both echinoderms and chordates.[6] Within echinoderms, one hypothesis holds that stylophorans are stem-group echinoderms which branched off before echinoderms evolved radial symmetry.[7] Another hypothesis holds that they are specialized descendants of radiate echinoderms which lost radial symmetry, likely belonging to Blastozoa.[8]

Solutes are divided into two orders, Syringocrinida and Dendrocystitida.[9]

Distribution

The earliest solutes, Coleicarpus and Castericystis, lived during the Drumian age of the Cambrian.[3] Solutes were the last of the four carpoid classes to appear in the fossil record. Solutes appear to have evolved in Laurentia,[3] but became more widespread during the Ordovician.[10]

gollark: Behind you! A khusa!
gollark: Dragons.
gollark: Every channel is everything.
gollark: This is weird given no context.
gollark: If I breed every single dragon I own *before* then the resulting wall should keep the prizes from view.

References
  1. Lefebvre, Bertrand; Derstler, Kraig; Sumrall, Colin D. (2012). "A reinterpretation of the solutan Plasiacystis mobilis (Echinodermata) from the Middle Ordovician of Bohemia". Zoosymposia. 7: 287–306. doi:10.11646/zoosymposia.7.1.27.
  2. Daley, Paul E. J. (1996). "The first solute which is attached as an adult: a Mid-Cambrian fossil from Utah with echinoderm and chordate affinities". Zoological Journal of the Linnean Society. 117 (4): 405–440. doi:10.1111/j.1096-3642.1996.tb01659.x. ISSN 0024-4082.
  3. Lefebvre, Bertrand; Lerosey-Aubril, Rudy (2017). "Laurentian origin of solutan echinoderms: new evidence from the Guzhangian (Cambrian Series 3) Weeks Formation of Utah, USA". Geological Magazine. 155 (5): 1190–1204. doi:10.1017/S0016756817000152.
  4. Parsley, Ronald L.; Rozhnov, Sergei V.; Sumrall, Colin D. (2012). "Morphologic and systematic revision of the solute Maennilia estonica (Homoiostelea, Echinodermata) from the Upper Ordovician of Estonia". Journal of Paleontology. 86 (3): 462–469. doi:10.1666/11-083.1.
  5. Rahman, Imran A. (2009). "Making sense of carpoids". Geology Today. 25 (1): 34–38. doi:10.1111/j.1365-2451.2009.00703.x.
  6. Jefferies, R. P. S. (1990). "The solute Dendrocystites scoticus from the Upper Ordovician of Scotland and the ancestry of chordates and echinoderms". Palaeontology. 33 (3): 631–679.
  7. Smith, Andrew B. (2005). "The pre-radial history of echinoderms". Geological Journal. 40 (3): 255–280. doi:10.1002/gj.1018.
  8. David, Bruno; Lefebvre, Bertrand; Mooi, Rich; Parsley, Ronald (2000). "Are homalozoans echinoderms? An answer from the extraxial-axial theory". Paleobiology. 26 (4): 529–555. doi:10.1666/0094-8373(2000)026<0529:AHEAAF>2.0.CO;2.
  9. Noailles, Fleur; Lefebvre, Bertrand; Kašička, Libor (2014). "A probable case of heterochrony in the solutan Dendrocystites Barrande, 1887 (Echinodermata: Blastozoa) from the Upper Ordovician of the Prague Basin (Czech Republic) and a revision of the family Dendrocystitidae Bassler, 1938". Bulletin of Geosciences. 89 (3): 451–476. ISSN 1214-1119.
  10. Zamora, Samuel; Lefebvre, Bertrand; Javier Álvaro, J.; Clausen, Sébastien; Elicki, Olaf; Fatka, Oldrich; Jell, Peter; Kouchinsky, Artem; Lin, Jih-Pai; Nardin, Elise; Parsley, Ronald; Rozhnov, Sergei; Sprinkle, James; Sumrall, Colin D.; Vizcaïno, Daniel; Smith, Andrew B. (2013). "Cambrian echinoderm diversity and palaeobiogeography". Geological Society, London, Memoirs. 38 (1): 157–171. doi:10.1144/M38.13.
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