Cotyledion

{{Speciesbox

| image = {{multiple image|perrow=2|total_width=270

| image1 = Cotyledion tylodes fossil.jpg

| image2 = Reconstruction of Cotyledion tylodes.jpg

| footer = Fossils and life position reconstruction of Cotyledion tylodes{{harvnb|Zhang|Holmer|Skovsted|Brock|2013}}

| border = infobox

}}

| fossil_range = {{Fossil range|Cambrian Stage 3}}

| genus = Cotyledion

| parent_authority = Luo and Hu in Luo et al., 1999

| species = tylodes

| authority = Luo and Hu in Luo et al., 1999

| synonyms = * ? Cambrotentacus sanwuia
{{small|Zhang and Shu in Zhang et al., 2001}}

}}

Cotyledion tylodes is an extinct, stalked filter-feeder known from the Chengjiang lagerstatten. The living animal reached a couple of centimetres in height, and bore a loose scleritome of ovoid sclerites. Its interpretation has been controversial, but it is currently thought to be a member of the Entoprocta stem group.{{harvnb|Hou|Siveter|Siveter|Aldridge|2017}}

History of identification

C. tylodes was initially tentatively classified as a stem group echinoderm in 1996, and then a lophophorate in 2002. Lophphorate affinities were challenged as based on taphonomic artifacts in a 2010 paper that suggested a cnidarian affinity based on cylyndrical symmetry as an ancestral body plan for that group.{{harvnb|Clausen|Hou|Bergström|Franzén|2010|page=137}}

A more recent alternative proposal suggested a relationship with the Cambroernida, a group of early deuterostomes.{{harvnb|Yang|Kimmig|Lieberman|Peng|2020}} However, a later comprehensive paper on cambroernids did not include Cotyledion.{{harvnb|Li|Dunn|Murdock|Guo|2023}}

A comprehensive 2013 study of around 400 new specimens provided stronger support for a lophophorate affinity, specifically allied with the entoprocts. The clear presence of a U-shaped gut in the new specimens contradicts placement among the cnidarians, while the lack of bifurcation in the crown of tentacles makes affinity with the deuterostomes unlikely.{{harvnb|Zhang|Holmer|Skovsted|Brock|2013|pages=3–5}} A recent review of echinoderm origins again refuted the placement of Cotyledion with that group, agreeing with its identity as a stem entoproct.{{harvnb|Rahman|Zamora|2024|page=301}}

References

=Works cited=

{{cite journal|last1=Clausen |first1=S. B. |last2=Hou |first2=X. G. |last3=Bergström |first3=J. |last4=Franzén |first4=C. |title=The absence of echinoderms from the Lower Cambrian Chengjiang fauna of China: Palaeoecological and palaeogeographical implications |doi=10.1016/j.palaeo.2010.01.001 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=294 |issue=3–4 |pages=133–141 |year=2010 |bibcode=2010PPP...294..133C}}
{{cite book|last1=Hou |first1=Xian-guang |last2=Siveter |first2=David J. |last3=Siveter |first3=Derek J. |last4=Aldridge |first4=Richard J. |last5=Cong |first5=Pei-yun |last6=Gabbott |first6=Sarah |last7=Ma |first7=Xiao-ya |last8=Purnell |first8=Mark A. |last9=Williams |first9=Mark |chapter=Entoprocta |title=The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life |edition=2 |date=2017 |pages=82–83 |doi=10.1002/9781118896372.ch25}}
{{cite journal |last1=Li |first1=Yujing |last2=Dunn |first2=Frances S. |last3=Murdock |first3=Duncan J.E. |last4=Guo |first4=Jin |last5=Rahman |first5=Imran A. |last6=Cong |first6=Peiyun |title=Cambrian stem-group ambulacrarians and the nature of the ancestral deuterostome |journal=Current Biology |date=May 10, 2023 |doi=10.1016/j.cub.2023.04.048 |pmid=37167976 |s2cid=258592223 |url=https://ora.ox.ac.uk/objects/uuid:6ae9e294-8268-4af2-93c4-d9863e467457/files/sm613n0124 |access-date=11 May 2023|doi-access=free |hdl=10141/623055 |hdl-access=free }}
{{cite journal|last1=Rahman |first1=Imran A. |last2=Zamora |first2=Samuel |title=Origin and early evolution of echinoderms |journal=Annual Review of Earth and Planetary Sciences |volume=52 |pages=295–320 |date=July 2024 |doi=10.1146/annurev-earth-031621-113343|hdl=10141/623070 |hdl-access=free }}
{{cite journal|last1=Yang |first1=Xianfeng |last2=Kimmig |first2=Julie |last3=Lieberman |first3=Bruce S. |last4=Peng |first4=Shanchi |title=A new species of the deuterostome Herpetogaster from the early Cambrian Chengjiang biota of South China |journal=The Science of Nature |year=2020 |volume=107 |number=37 |doi=10.1007/s00114-020-01695-w|pmc=7544619 }}
{{cite journal|last1=Zhang |first1=Z. |last2=Holmer |first2=L. E. |last3= Skovsted |first3=C. B. |last4=Brock |first4=G. A. |last5=Budd |first5=G. E. |last6=Fu |first6=D. |last7=Zhang |first7=X. |last8=Shu |first8=D. |last9=Han |first9=J. |last10=Liu |first10=J. |last11=Wang |first11=H. |last12=Butler |first12=A. N. |last13=Li |first13=G. |title=A sclerite-bearing stem group entoproct from the early Cambrian and its implications |doi=10.1038/srep01066 |journal=Scientific Reports |volume=3 |pages=1066 |year=2013 |pmid= 23336066| pmc=3548229| bibcode=2013NatSR...3E1066Z}}

Category:Maotianshan shales fossils

Category:Monotypic prehistoric protostome genera

Category:Cambrian genus extinctions

Cotyledion

History of identification

See also

References

=Works cited=