Identification and Current Palaeobiological Understanding of “Keratosa”-Type Nonspicular Demosponge Fossils in Carbonates: With a New Example from the Lowermost Triassic, Armenia

Luo, Cui; Pei, Yu; Richoz, Sylvain; Li, Qijian; Reitner, Joachim

doi:10.3390/life12091348

Cited by 5 publications

(12 citation statements)

References 70 publications

(123 reference statements)

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“…Many other examples occur within earlyformed cavities in early-lithified limestone (Lee et al, 2014). In addition to published twodimensional thin section studies is work by Luo & Reitner (2014) and Luo et al (2022) that provides preliminary three-dimensional reconstructions at microscopic scale. These limited studies are an important step forward and future work (3D at mesoscopic scale) may help to resolve the nature of the five categories considered here.…”

Section: Resultsmentioning

confidence: 99%

“…The issue of canals in possible keratose sponges was addressed by Luo et al . (2022, fig. 5), with potential canals revealed through serial grinding, but more complete investigation is needed to prove that these structures are canals (see Table 1).…”

Section: Discussionmentioning

confidence: 99%

“…Key examples are by Reitner et al (2001), Luo & Reitner (2014, Lee & Hong (2019), Lee & Riding (2021a,b, 2022, 2023, Baud et al (2021), Pei et al (2021a,b), Pham et al (2021), Gischler et al (2021), Turner (2021) and Reitner et al (2021). Luo et al (2022) presented criteria for recognition of fossil keratose sponges, which are discussed later. No published cases of vermiform structure interpreted as sponges in rocks younger than Jurassic were found during this study, although Luo (2015, p. 100-103) argued that possible keratosan sponges occur in Cretaceous and Eocene strata.…”

Section: Introductionmentioning

confidence: 99%

“…Luo et al . (2022) presented criteria for recognition of fossil keratose sponges, which are discussed later. No published cases of vermiform structure interpreted as sponges in rocks younger than Jurassic were found during this study, although Luo (2015, p. 100–103) argued that possible keratosan sponges occur in Cretaceous and Eocene strata.…”

Section: Introductionmentioning

confidence: 99%

“…Tabulation of the six criteria for recognition of keratose sponges byLuo et al (2022), with comments on their applicability. Source:Luo et al (2022).…”

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confidence: 99%

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Keratose sponges in ancient carbonates – A problem of interpretation

et al. 2022

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Reports of diverse vermiform and peloidal structures in Neoproterozoic to Mesozoic open marine to peritidal carbonates include cases interpreted to be keratose sponges. However, living keratose sponges have elaborate, highly elastic skeletons of spongin (a mesoscopic end‐member of a hierarchical assemblage of collagenous structures) lacking spicules, thus have poor preservation potential in contrast to the more easily fossilized spicule‐bearing sponges. Such interpreted fossil keratose sponges comprise diverse layered, network, amalgamated, granular and variegated microfabrics of narrow curved, branching, vesicular–cellular to irregular areas of calcite cement, thought to represent former spongin, embedded in microcrystalline to peloidal carbonate. Interpreted keratose sponges are presented in publications almost entirely in two‐dimensional (thin section) studies, usually displayed normal to bedding, lacking mesoscopic three‐dimensional views in support of a sponge body fossil. For these structures to be keratose sponges critically requires conversion of the spongin skeleton into the calcite cement component, under shallow‐burial conditions and this must have occurred prior to compaction. However, there is no robust petrographic–geochemical evidence that the fine‐grained carbonate component originated from sponge mummification (automicritic body fossils via calcification of structural tissue components) because in the majority of cases the fine‐grained component is homogenous and thus likely to be deposited sediment. Thus, despite numerous studies, verification of fossil keratose sponges is lacking. Although some may be sponges, all can be otherwise explained. Alternatives include: (i) meiofaunal activity; (ii) layered microbial (spongiostromate) accretion; (iii) sedimentary peloidal to clotted micrites; (iv) fluid escape and capture resulting in bird's eye to vuggy porosities; and (v) moulds of siliceous sponge spicules. Uncertainty of keratose sponge identification is fundamental and far‐reaching for understanding: (i) microfacies and diagenesis where they occur; (ii) fossil assemblages; and (iii) wider aspects of origins of animal clades, sponge ecology, evolution and the systemic recovery from mass extinctions. Thus, alternative explanations must be considered.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Tabulation of the six criteria for recognition of keratose sponges byLuo et al (2022), with comments on their applicability. Source:Luo et al (2022).…”

mentioning

confidence: 99%

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