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eocrinoidea

{{short description|Class of echinoderms}}

{{Paraphyletic group

| name = Eocrinoidea

| fossil_range = {{fossil range|Cambrian Stage 3|Silurian}}

| image = Ordovician_hardground_Utah.jpg

| image_caption = Eocrinoid holdfasts (Middle Ordovician, Utah)

| image2 = Gogia_ojenai.jpg

| image2_caption = Colourful reconstruction of Gogia ojenai

| auto = yes

| taxon = Eocrinoidea

| extinct = yes

| authority = Jaekel, 1899

| includes_ref = {{cite web|website=Paleobiology Database |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=31058 |title=†class Eocrinoidea Jaekel 1918 |accessdate=27 November 2024}}

{{small|(Note: order Imbricata was discarded in favor of family Lepidocystoidae in Nardin et al. 2017, and is therefore not shown as a subgroup)}}

| includes =

  • †Ascocystitida
  • †Ascocystitidae
  • †Cambrocystidae{{harvnb|Parsley|2021|page=975}}
  • †Rhopalocystidae
  • †Gogiida
  • †Eocrinidae
  • †Lyracystidae
  • †Trachelocrinida
  • †Heckerocrinidae
  • †Trachelocrinidae
  • †Cryptocrinitidae
  • †Felbabkacystidae
  • †Lepidocystoidae{{harvnb|Nardin|Lefebvre|Fatka|Nohejlová|2017|page=674}} {{small|(Note: discards order Imbricata Sprinkle, 1973 in favor of family Lepidocystoidae Durham, 1968)}}
  • †Lichenoididae
  • †Lingulocystidae
  • †Palaeocystitidae
  • †Rhipidocystidae
  • †Ridersiidae

| excludes =

}}

The Eocrinoidea were an extinct class of echinoderms that lived between the Early Cambrian and Late Silurian periods. They are the earliest known group of stalked, brachiole-bearing echinoderms, and were the most common echinoderms during the Cambrian.

The earliest genera had a short holdfast and irregularly structured plates. Later forms had a fully developed stalk with regular rows of plates. They were benthic suspension feeders, with five ambulacra on the upper surface, surrounding the mouth and extending into a number of narrow arms.{{harvnb|Prothero|2004|page=324}}{{harvnb|Barnes|1982}}

Phylogeny

{{see also|List of echinoderm orders}}

Eocrinoids were a paraphyletic group that are seen as the basal stock from which all other blastozoan groups evolved.{{harvnb|Smith|1984|page=439}}

=Early evolution=

The following cladogram, after Nardin et al. 2017,{{harvnb|Nardin|Lefebvre|Fatka|Nohejlová|2017|page=680}} shows the progression of early eocrinoid families, with all other eocrinoid families (including representatives Trachelocrinus and Ridersia) grouped with "derived Blastozoans" as their relationships with each other and with other blastozoans are not addressed.

{{Clade|style=font-size:85%;line-height:85%

|label1=Lepidocystoidae

|1={{Clade

|1=Kinzercystis

|2=Vyscystis

|3=Lepidocystis

}}

|2={{Clade

|label1=Felbabkacystidae

|1=Felbabkacystis

|2={{Clade

|grouplabel1={{Clade labels |bar1=indigo |label1="Eocrinidae"}}

|1=Lyracystis

|barbegin1=indigo

|2={{Clade

|1={{Clade

|1=Akadocrinus

|2=Gogia

|3=Sinoeocrinus

|4=Ubaghsicystis

}}

|barend1=indigo

|2={{Clade

|label1=Lichenoidae

|1=Lichenoides

|2={{Clade

|1=Trachelocrinus

|2=Ridersia

|3=(derived Blastozoa)

}} }} }} }} }} }}

Note that some other sources use a more restricted definition of Eocrinidae,{{cite web|website=Paleobiology Database |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=txn:120077 |title=†family Eocrinidae Jaekel 1918 |accessdate=27 November 2024}} or use the spelling Lichenoididae in place of Lichenoidae.{{cite web|website=Paleobiology Database |url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=txn:371139 |title=†family Lichenoididae Jaekel 1918 |accessdate=27 November 2024}}

=Relationships to other groups=

Relationships among the eocrinidae and other blastozoan clades are an area of ongoing study. Below are two of many cladograms showing some aspect of eocrinoid paraphyly or polyphyly.

{{col-begin|width=auto}}

{{col-break}}

{{thumb|width=400|content=

{{barlabel|style=font-size:85%;line-height:85%

|size=14

|at1=0 |bar1=brown |label1=Lepidocystoids (Eocrinoids)

|at2=1 |bar2=indigo |label2=Crinoids

|at3=5 |bar3=brown |label3=Eocrinoids

|at4=10 |bar4=green |label4=Dibrachicystids (Rhombiferans)

|at5=12 |bar5=darkgreen |label5=Glyptocystitoids (Rhombiferans)

|at6=15 |bar6=brown |label6=Eocrinoids

|cladogram=

{{clade

|1={{clade

|1=Kinzercystis |barbegin1=brown

|2={{clade

|1={{clade

|1={{clade

|1=Titanocrinus |barbegin1=indigo

|2=Aethocrinus|barend2=indigo

}}

|2=Lyracystis |bar2=brown

}}

|2={{clade

|1=Gogia |bar1=brown

|2=Sinoeocrinus |bar2=brown

|3={{clade

|1=Akadocrinus |bar1=brown

|2={{clade

|1=Tatonkacystis |bar1=brown

|2=Ubaghsicystis |bar2=brown

|3={{clade

|1=Dibrachicystis |barbegin1=green |barend1=green

|2=Pleurocystites |barbegin2=darkgreen

|3={{clade

|1=Velieuxicystis |bar1=darkgreen

|2={{clade

|1=Macrocystella   |barend1=darkgreen

|2=Ridersia |barend2=brown

}} }} }} }} }} }} }} }} }}

}}

|caption=Stalked Cambrian (and select Ordovician) echinoderms, after Zamora & Smith, 2011.{{harvnb|Zamora|Smith|2011}} All genera except those bracketed as "Crinoids" are blastozoans.}}

{{col-break}}

{{thumb|width=400|content=

{{barlabel|style=font-size:85%;line-height:85%

|size=17

|at1=0 |label1=Eocrinoids |bar1=brown

|at2=5 |label2=Glyptocystitoids (Rhombiferans) |bar2=darkgreen

|at3=12 |label3=Blastoids |bar3=darkblue

|at4=14 |label4=Eublastoids (Blastoids) |bar4=purple

|at5=15 |label5=Coronoids (Blastoids) |bar5=indigo

|at6=17 |label6=Hemicosmitoids (Rhombiferans) |bar6=green

|cladogram={{Clade

|1={{Clade

|1={{Clade

|1=Akadocrinus

|2=Cambrocrinus

}} |barbegin1=brown

|2=Ridersia |barend2=brown

|3=Sanducystis

|4={{Clade

|1={{Clade

|1=Cystobsastus

|2={{Clade

|1=Lepadocystis

|2={{Clade

|1=Echinoencrinites

|2={{Clade

|1=Cheirocystella

|2=Macrocystella

}}

}}

}}

}}

|barbegin1=darkgreen

|2={{Clade

|1={{Clade

|1=Rhombifera

|barend1=darkgreen

|2=Lysocystites |barbegin2=indigo

|3={{Clade

|1=Macurdablastus    |bar1=indigo

|2=Codaster |barbegin2=purple |barend2=purple

}}

|4=Stephanocrinus |barbegin4=darkblue |barend4=darkblue

}}

|barbegin2=green |barend2=green

|2={{Clade

|1=Thomacystis

|2={{Clade

|1=Caryocrinites

|2=Hemicosmites

}}

}}

}}

}}

}} }}

}}

|caption=This cladogram, after Paul et al. 2024, shows several eocrinoids in a polytomy with a clade containing several other blastozoan groups.{{harvnb|Paul|Lefebvre|Nohejlová|Zamora|2024|page=12–13}} {{small|(Note: The text groups Sanducystis with eocrinoids as the outgroup, but the paper cited classifies it as a glyptocystitoid; it is shown un-bracketed on this page. Similarly, the text classifies Macurdablastus as a eublastoid, but the cited paper has it as the sister of Eublastoidea; it is shown outside of Eublastoidea on this page.)}}

}}

{{col-end}}

References

{{reflist}}

Works cited

{{refbegin}}

  • {{cite book |last1=Barnes |first1=Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA|pages= 1007–1008|isbn= 978-0-03-056747-6}}
  • {{cite journal|last1=Nardin |first1=Elise |last2=Lefebvre |first2=Bertrand |last3=Fatka |first3=Oldřich |last4=Nohejlová |first4=Martina |last5=Kašička |first5=Libor |last6=Šinágl |first6=Miroslav |last7=Szabad |first7=Michal |title=Evolutionary implications of a new transitional blastozoan echinoderm from the middle Cambrian of the Czech Republic |journal=Journal of Paleontology |volume=91 |number=4 |year=2017 |pages=672–684|doi=10.1017/jpa.2016.157 |bibcode=2017JPal...91..672N }}
  • {{cite journal|last1=Parsley |first1=R. L. |title=Evolution, Functional Morphology and Paedomorphism in the Gogiid-Ascocystitid Lineage (Eocrinoidea; Cambrian-Ordovician) |journal=Paleontological Journal |volume=55 |number=9 |year=2021 |pages=966–976 |doi=10.1134/S0031030121090100|bibcode=2021PalJ...55..966P }}
  • {{cite journal|last1=Paul |first1=Christopher R. C. |last2=Lefebvre |first2=Bertrand |last3=Nohejlová |first3=Martina |last4=Zamora |first4=Samuel |title=Rhombifera Barrande, 1867, and the origin of the Blastoidea (Echinodermata, Blastozoa) |journal=Spanish Journal of Palaeontology |volume=39 |year=2024 |page=90 |doi=10.7203/sjp.28729}}
  • {{cite book|last1=Prothero |first1=D. R. |year=2004 |title=Bringing Fossils to Life; An Introduction to Paleobiology |edition=2 |location=New York |publisher=The McGraw-Hill companies}}
  • {{cite journal|last1=Smith |first1=Andrew B. |title=Classification of the Echinodermata |journal=Palaeontology |volume=27 |number=3 |year=1984 |pages=431–459 }}
  • {{Cite journal|last1=Zamora |first1=Samuel |last2=Smith |first2=A. B. |year=2011 |title=Cambrian stalked echinoderms show unexpected plasticity of arm construction |journal=Proceedings of the Royal Society B |volume=279|issue= 1727|pages= 293–298|doi=10.1098/rspb.2011.0777 |pmid=21653588 |pmc=3223674}}

{{refend}}

{{Taxonbar|from=Q149514}}

Category:Blastozoa

Category:Paleozoic echinoderms

Category:Cambrian echinoderms

Category:Silurian echinoderms

Category:Cambrian first appearances

Category:Silurian extinctions

Category:Paraphyletic groups

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