A vanished history of skeletonization in Cambrian comb jellies
Open accessAbstract
Ctenophores are traditionally regarded as "lower" metazoans, sharing with cnidarians a diploblastic grade of organization. Unlike cnidarians, where skeletonization (biomineralization and sclerotization) evolved repeatedly among ecologically important taxa (for example, scleractinians and octocorals), living ctenophores are characteristically soft-bodied animals. We report six sclerotized and armored ctenophores from the early Cambrian period. They have diagnostic ctenophore features (for example, an octamerous symmetry, oral-aboral axis, aboral sense organ, and octaradially arranged ctene rows). Unlike most modern counterparts, however, they lack tentacles, have a sclerotized framework, and have eight pairs of ctene rows. They are resolved as a monophyletic group (Scleroctenophora new class) within the ctenophores. This clade reveals a cryptic history and sheds new light on the early evolution of this basal animal phylum. Skeletonization also occurs in some other Cambrian animal groups whose extant members are exclusively soft-bodied, suggesting the ecological importance of skeletonization in the Cambrian explosion.
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Ctenophores are unequivocally monophyletic and have a diverse Cambrian fossil record.
“Despite the fact that ctenophores are unequivocally monophyletic and have a diverse Cambrian fossil record”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
The Results describe six Cambrian ctenophore species, supporting the existence of multiple Cambrian fossils. But the Introduction calls the ctenophore fossil record generally poor, and the Discussion finds monophyly for the skeletonized Chengjiang ctenophores—not unequivocal monophyly of all ctenophores. No page numbers are available in our copy. (LLM, conf=0.87)
Experimental — accuracy not yet measuredGiven the mode of preservation and comparison with other sclerotized taxa, the 'dinomischid' skeleton was most likely organic in composition, although light mineralization cannot be excluded.
“Given the mode of preservation and comparison with other sclerotized taxa, it was most likely organic in composition, although we cannot exclude light mineralization”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
The Discussion (page not available in our copy) says the skeletons of Chengjiang ctenophores were likely cuticular or chitinous, while minerals cannot be ruled out. That supports the proposed composition and uncertainty for ctenophores, but it does not establish the composition of the dinomischid skeleton. (LLM, conf=0.82)
Experimental — accuracy not yet measuredCtenophores from the early Cambrian Chengjiang Konservat-Lagerstätte possess a unique organic skeleton and were united as the clade Scleroctenophora.
“Ctenophores from the early Cambrian Chengjiang Konservat-Lagerstätte possess a unique organic skeleton and were united as the clade Scleroctenophora by Ou et al.”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
The Introduction identifies the fossils as early Cambrian Chengjiang ctenophores, and the Discussion says their skeletonized forms constitute a clade described as the new class Scleroctenophora. The Discussion also calls their skeletons unique, but says they were only likely cuticular or chitinous and that a mineral component cannot be ruled out. Thus, describing the skeleton as definitively organic overstates the source. (LLM, conf=0.88)
Experimental — accuracy not yet measuredThe oldest unequivocal ctenophore fossils are found in the early Cambrian Chengjiang Konservat-Lagerstätte and the middle Cambrian Burgess Shale.
“The oldest unequivocal ctenophore fossils are found in the early Cambrian Chengjiang Konservat-Lagerstätte”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
The dark stain was identified as a statolith, but is at least an order of magnitude larger than those of extant ctenophores.
“which was identified as a statolith [2”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
The new matrix builds on previously available datasets through the incorporation of new morphological information and an expanded taxon sample.
“The new matrix builds on previously available datasets [2, 11, 13, 53”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
Several scleroctenophore species are known from Chengjiang in the genera Galeactena, Maotianoascus, Thaumactena, Batofasciculus and Trigoides.
“Several species are known from Chengjiang (in the genera Galeactena, Maotianoascus, Thaumactena, Batofasciculus and Trigoides) [2”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
Where the skeletal rod splits off into the counterpart, a dark line, consistent with a nerve, runs beneath it and connects to the lateral sets of ctenes.
“Where the skeletal rod (membranous fin, sensu Ou et al. [2”
From Cambrian Sessile, Suspension Feeding Stem-Group Ctenophores and Evolution of the Comb Jelly Body Plan (2019) · cites this paper as [2]
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- Authors
- Ou, Q., Xiao, S., Han, J., Sun, G., Zhang, F., Zhang, Z., & Shu, D.
- Affiliations
- China University of Geosciences (CN)
- Virginia Tech (US)
- Northwest University (CN)
- Tsinghua University (CN)
- Corresponding author
- Ou, Qiang
- Venue
- Science Advances
- Published
- 2015-07-03
- Volume
- 1
- Issue
- 6
- Pages
- e1500092-e1500092
- ISSN
- 2375-2548 (ISSN-L)
- PMC
- PMC4646772
- OpenAlex
- W2222825640
- Cited by
- 43
- References
- 49
- Citations by year
- 2026: 5 · 2025: 3 · 2024: 3 · 2023: 5 · 2021: 5 · 2020: 2 · 2019: 3 · 2018: 2 · 2017: 7 · 2016: 5 · 2015: 3
- FWCI
- 4.28
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Licence
- cc-by-nc
- Locations
- Science Advances (publishedVersion, cc-by-nc)
- PubMed Central (publishedVersion, cc-by-nc)
- PubMed (publishedVersion)
- VTechWorks (Virginia Tech) (submittedVersion, cc-by-nc)
- Funders
- Program for New Century Excellent Talents in University (ID0EX2BG1647, NCET-13-1008)
- National Natural Science Foundation of China (ID0EOAAI1648, 41102012, 41272011)
- Fundamental Research Funds for the Central Universities (ID0EEFAI1649, 2010ZY07, 2011YXL013, 2012097)
- U.S. National Science Foundation (ID0EYJAI1650, EAR-1124062)
- Topics
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Evolutionary Biology
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
- Keywords
- ctenophores, skeletonization, biomineralization, sclerotization, Cambrian fossils, Cambrian explosion, animal evolution, soft-bodied animals, new class, monophyly
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