Periodic shell decollation as an ecology‐driven strategy in the early Cambrian <i>Cupitheca</i>

Sun, Haijing; Yin, Zongjun; Li, Guoxiang; Zhao, Fangchen; Zeng, Han; Zhu, Maoyan

doi:10.1111/pala.12463

Cited by 8 publications

(8 citation statements)

References 26 publications

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“…Except for the decollated Cupitheca (Sun et al . 2020) I can find no convincing example of resorption in any Cambrian skeletons. In gnathostomes (derived, post‐Ordovician jaw‐bearing vertebrates) the skeleton is to varying degrees subject to remodelling as calcium phosphate is precipitated and recycled (Buffrénil et al .…”

Section: The Evolution Of Dynamic Skeletonsmentioning

confidence: 93%

“…Finally in the probable hyolith Cupitheca from the early Cambrian, periodic decollation and septal formation accompanied by shell resorption represents by far the oldest example of decollation (Sun et al . 2020). In gastropods, evolved decollation is always associated with the formation of an apical septum, which closes off the opening formed when the apical whorls break off; but apical septa are also common in gastropods that do not undergo decollation.…”

Section: Taxonomic Surveymentioning

confidence: 99%

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Overcoming the constraints of spiral growth: the case of shell remodelling

Vermeij

2020

Palaeontology

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As animals grow in size, their relationship to the physical environment necessarily changes, but molluscs and brachiopods whose accretionary skeletons expand at one end of a hollow cone conform to logarithmic‐spiral growth and retain a constant shape. Dissolution and remodelling of previously formed parts of the skeleton can alleviate the constraints of strict logarithmic‐spiral growth. How, when, where and in which clades mineral skeletal resorption has evolved are important questions because they relate to the conditions and history of skeletal formation and to the way in which ocean acidification in the past influenced that history. A synthesis of data on mineral dissolution in shells shows that resorption from the inner surface of bivalve shells occurs under temporarily anaerobic conditions within the closed shell, but functional remodelling is unknown in bivalves. Resorption and functional remodelling occur in brachiopods, gastropods and terrestrial hermit crabs, and to a lesser extent in scaphopods and cephalopods. Internal whorl resorption leading to a more compact visceral mass has evolved at least ten times in gastropods. Contrary to expectations stemming from patterns in the availability of calcium, gastropod remodelling is a phenomenon of warm, calcium‐rich environments and not of cold acidified conditions. There is therefore no evidence that internal whorl resorption increases calcium‐use efficiency. Resorption is one of several mechanisms that have enabled animal skeletons to become more dynamic and adaptable during ontogeny.

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Section: The Evolution Of Dynamic Skeletonsmentioning

confidence: 93%

Section: Taxonomic Surveymentioning

confidence: 99%

Overcoming the constraints of spiral growth: the case of shell remodelling

Vermeij

2020

Palaeontology

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“…The initial parts of the conch of Cupitheca could be successively aborted during ontogeny due to the formation of secondary transverse septa (Sun et al . 2020).…”

Section: Methodsmentioning

confidence: 99%

Deep origin of the crossed‐lamellar microstructure in early Cambrian molluscs

Skovsted

Topper

2022

Palaeontology

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Aragonitic crossed‐lamellar (CL) is one of the most commonly formed and extensively studied molluscan shell microstructures, yet its origin and early evolution within the Mollusca remains poorly understood. Here, a primitive CL microstructure from one of the oldest gastropods, Pelagiella madianensis, and the problematic hyolith Cupitheca sp. of the Cambrian Series 2 Xinji Formation on the North China Platform, was investigated. In P. madianensis, detailed characterization has revealed a typical four‐ordered hierarchical organization of aragonitic crystallites, and a thick layer of organic membranes surrounding its first‐order lamellae. A transitional fibrous microstructure was observed between the outer CL and inner foliated aragonite structural layers. In Cupitheca sp., only the first and second‐order lamellae were visible due to preservation limitations, and the first‐order lamellae were extremely irregular in shape and size, which is consistent with modern representatives. This study demonstrates that the capability to construct highly‐mineralized intricate shells was acquired in early Cambrian stem‐group gastropods. The CL microstructure first emerged in the early Cambrian and as a basal synapomorphic trait in total‐group molluscs. Moreover, presence of the CL microstructure in problematic lophotrochozoans (i.e. hyoliths) is confirmed. This study contributes to a more complete picture of the evolutionary origin and architectural diversity of biomineralized mollusc shells during the Cambrian explosion, and strengthens the phylogenetic links between hyoliths and molluscs.

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“…Moreover, the conch of Longxiantheca is also reminiscent of Cupitheca in terms of its blunt apical termination with characteristic dense tubules [35]. However, the older parts of Cupitheca conchs are decollated successively during the life of the organism by a specialized dissolution process [36], which is unknown in the septate initial parts of Longxiantheca conchs.…”

Section: Introductionmentioning

confidence: 99%

New insight into the soft anatomy and shell microstructures of early Cambrian orthothecids (Hyolitha)

Skovsted

Yun

et al. 2020

Proc. R. Soc. B.

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Hyoliths (hyolithids and orthothecids) were one of the most successful early biomineralizing lophotrochozoans and were a key component of the Cambrian evolutionary fauna. However, the morphology, skeletogenesis and anatomy of earliest members of this enigmatic clade, as well as its relationship with other lophotrochozoan phyla remain contentious. Here, we present a new orthothecid, Longxiantheca mira gen. et sp. nov. preserved as part of secondarily phosphatized small shelly fossil assemblage from the lower Cambrian Xinji Formation of North China. Longxiantheca mira retains some ancestral traits of the clade with an undifferentiated disc-shaped operculum, a simple conical conch with apical septa and a two-layered microstructure of aragonitic fibrous bundles. The operculum interior exhibits impressions of soft tissues, including muscle attachment scars, mantle epithelial cells and a central kidney-shaped platform interpreted as a support structure in association with its presumptive feeding apparatus. The muscular system in orthothecids appears to be similar to that in hyolithids, suggesting a consistent anatomical configuration among the total group of hyoliths. The new finding of shell secreting cells demonstrates a mantle regulating the mode of growth for the operculum. Investigations of shell microstructures support the placement of hyoliths as total group molluscs with an unsettled position within the phylum Mollusca.

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Periodic shell decollation as an ecology‐driven strategy in the early Cambrian Cupitheca

Cited by 8 publications

References 26 publications

Overcoming the constraints of spiral growth: the case of shell remodelling

Overcoming the constraints of spiral growth: the case of shell remodelling

Deep origin of the crossed‐lamellar microstructure in early Cambrian molluscs

New insight into the soft anatomy and shell microstructures of early Cambrian orthothecids (Hyolitha)

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