Ediacaran Corumbella has a cataphract calcareous skeleton with controlled biomineralization

Gabriel Ladeira Osés; Rachel Wood; Guilherme Raffaeli Romero; Gustavo Marcondes Evangelista Martins Prado; Pidassa Bidola; Julia Herzen; Franz Pfeiffer; Sérgio Nascimento Stampar; Mírian Liza Alves Forancelli Pacheco

doi:10.1016/j.isci.2022.105676

. 2022 Nov 25;25(12):105676. doi: 10.1016/j.isci.2022.105676

Ediacaran Corumbella has a cataphract calcareous skeleton with controlled biomineralization

Gabriel Ladeira Osés ^1,^2,^3,⁴, Rachel Wood ², Guilherme Raffaeli Romero ⁵, Gustavo Marcondes Evangelista Martins Prado ⁶, Pidassa Bidola ⁷, Julia Herzen ^8,⁹, Franz Pfeiffer ^9,^10,¹¹, Sérgio Nascimento Stampar ¹², Mírian Liza Alves Forancelli Pacheco ^3,^4,^13,^∗

PMCID: PMC9763863 PMID: 36561886

Summary

Corumbella is a terminal Ediacaran tubular, benthic fossil of debated morphology, composition, and biological affinity. Here, we show that Corumbella had a biomineralized skeleton, with a bilayered construction of imbricated calcareous plates and rings (sclerites) yielding a cataphract organization, that enhanced flexibility. Each sclerite likely possessed a laminar microfabric with consistent crystallographic orientation, within an organic matrix. Original aragonitic mineralogy is supported by relict aragonite and elevated Sr (mean = ca. 11,800 ppm in central parts of sclerites). In sum, the presence of a polarisation axis, sclerites with a laminar microfabric, and a cataphract skeletal organization reminiscent of early Cambrian taxa, are all consistent with, but not necessarily indicative of, a bilaterian affinity. A cataphract skeleton with an inferred complex microstructure confirms the presence of controlled biomineralization in metazoans by the terminal Ediacaran, and offers insights into the evolution of development and ecology at the root of the ‘Cambrian radiation’.

Subject areas: Biological sciences, evolutionary biology, evolutionary processes

Graphical abstract

Highlights

•
Corumbella had a calcareous skeleton, with a cataphract organization of sclerites
•
An original aragonitic mineralogy is supported by relict aragonite and elevated Sr
•
Morphology and crystallographic orientation indicate controlled biomineralization
•
Morphology and laminar microfabric are reminiscent of early Cambrian taxa

Biological sciences; Evolutionary biology; Evolutionary processes

Introduction

Metazoans developed skeletal, calcareous, hard parts in the terminal Ediacaran ca. 550 million years ago, probably independently in unrelated clades,¹^,² representing a visible root of the ‘Cambrian radiation’. Much uncertainty remains, however, as to the affinity of the early biomineralizing taxa, the degree of biological control exerted over biomineralization, and their relationship to lower Cambrian taxa.

Corumbella is an extinct genus of terminal Ediacaran age represented by a single species, Corumbella werneri, known from siliciclastic and carbonate settings from Brazil, Paraguay, and the USA.³^,⁴^,⁵^,⁶ Corumbella has been described as a flexible, tubular form with oral-aboral axis and 4-fold symmetry constructed by rings, and midlines formed by the junction of alternate continuous rings⁵^,⁶^,⁷^,⁸ (Table S1; Figure S1). Rings have been assumed to have been formed by lamellae of either organic or weakly mineralized composition.⁶ Corumbella has been interpreted as epibenthic, with a point of substrate attachment and shows directional growth.⁵^,⁶ The taxon has been attributed to either scyphozoan cnidarians related to the extinct conulariids⁶^,⁷^,⁸^,⁹, or sinotubulitid or siboglinid annelids¹⁰ (Tables S2, S3, and S4).

Much uncertainty as to the morphology and biomineralization status of Corumbella is due to poor preservation of key features resulting from strong diagenetic overprinting. It has been suggested that Corumbella was biomineralized, but this is based only on the calcitic preservation of the rings.⁶^,¹⁰^,¹¹ It has not been established whether this calcite is a diagenetic replacement of an organic precursor skeleton, or of a different original, but unstable, carbonate polymorph.

Here we describe exceptionally preserved material from fine-grained marls and shales of the late Ediacaran Tamengo Formation, ca. 555-542 Ma¹² from Corumbá and Ladário, Brazil (Figure S2; Data S1). We apply light petrography coupled with cathodoluminescence (CL) imaging, micro-Raman spectroscopy, scanning electron microscopy (SEM), including backscattered electron imaging (BSE), energy-dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), and electron microprobe analysis (EPMA), and X-ray microtomographic (micro-CT) imaging, to resolve the morphology and composition of Corumbella. This multi-technique approach enables the formulation of a morphological reconstruction to be presented, reminiscent of early Cambrian taxa with cataphract skeletal organization, defined as articulating imbricated elements. Our data further demonstrate that biomineralization in Corumbella was biologically-controlled, therefore informing the evolution of controlled biomineralization and its ecological implications.

Results

Optical microscopy

Light photomicrographs of longitudinal sections of the Corumbella tube show crystalline areas of calcite surrounded by red staining (Figure 1A; see Figure S3A for original sample).

Photomicrographs of highly polished thin sections showing the skeletal structure of *Corumbella werneri*

(A–E) Sample CAP/1F 11. F and G: Sample CAP/1F 12. The cutting direction of original samples is available in Figures S3A and S3C.

(A) Plane polarised light (PPL) image of tube longitudinal section, showing calcitic plates outlined by Fe-(oxyhydr)oxides film (dashed yellow lines).

(B) Cathodoluminescence (CL) image of two layers of imbricated plates. Area shown in A highlighted.

(C–E) CL images of individual plates. F and G: Respectively, PPL and CL images of the cross-section of tube showing plates. Scale bars: A, C, F, and G = 0.1 mm; B, D, and E = 0.2 mm. The assembling of original figures resulting in A-G is shown in Figure S6. Original figures have been cropped to remove excess of empty space around the fossils and also to enable stitching.

Cathodoluminescence imaging

Cathodoluminescence (CL) and 3D micro-CT imaging, which has been used to investigate the 3D morphology of the skeleton, reveals the tubes of these organisms to be comprised of two layers of discontinuous plates and rings, together termed sclerites, that are imbricated in opposite directions in each layer (Figures 1B–1E, 2A–2F, S4, and S5). Each sclerite has rounded or pointed terminations and a sigmoidal shape (Figures 1B–1E, 2B, 2D, and 2E). The inner tube wall is not smooth due to the imbrication of the inner layer (Figure 1B). Plates and rings appear to have irregular surfaces (Figures 1B–1E and S4). A single thicker element lies close to the proximal region of the tube (Figures S4A and S4B). In plane view, each plate progressively tapers toward its terminations at the main axis of tube faces, along which plates are displaced on either side of the midline articulation axis⁵ (Figures 2A and S3A). Cathodoluminescence was used to further investigate the composition of the skeleton. Under CL, the skeleton shows a patchy but generally non-to-dull luminescence but with brightly luminescent margins (Figures 1B–1E, 1G, and S4B). The innermost margins of the skeleton may also show a more continuous brightly luminescent layer (Figure 1G). This layer may also be present within the central part of the skeleton, and some parts appear to be composed of vertically elongated, palisade-like sparry crystals at their margins (Figure S4F).

Morphological reconstruction, micro-CT, and disarticulation patterns of *Corumbella* skeleton microstructure

Sample GP/1E 574a in E and F.

(A) Hypothesis for the reconstruction of an individual. The lowermost gray plane marks the transition from the proximal to the distal parts, which are respectively build by rings and plates.

(B) Cataphract organization of regularly imbricated plates in two layers. “LO” and “TR”, respectively longitudinal and transverse sections of sclerites.

(C) Tube cross-section with the longitudinal section of plates.

(D) Plate (I), respectively in longitudinal (II) and in transverse section (III). “LO” and “TR”, respectively longitudinal section and transverse section.

(E) 3D rendering of a 3D specimen in slightly rotated plane view (left), with plate imbrication shown at the image bottom (arrowheads); and in the cross-section of the tube (right). Modified from Figure 6B of Pacheco et al.⁶ (https://doi.org/10.1371/journal.pone.0114219), originally published under a Creative Commons Attribution License.

(F) 3D rendering (showing cross-section of the tube) of the same specimen in E. The direction of sectioning is shown in Figure S7. Arrows indicate the gap between two stacked skeletal layers; arrowheads indicate the bilayered skeletal wall; 1-Lateral edge, 2-Midline in cross-section, and 3-Collapsed wall. Scale bar: 2 mm. F was modified from Figure 3D of Bidola et al.⁸⁹; permission for electronic reuse granted by “Cambridge University Press” via RightsLink. The full 3D rendering of sample GP/1E 574a is available in Video S1.

(G) Types of disarticulation shown in Figure S8. I-Articulated specimen; II-Disarticulation along midline and between plates and rings; III-‘Peeling’, that is disarticulation between layers of sclerites; and IV-Disarticulation of consecutive sclerites (plates) leaving molds and plates fragmented at the lateral edge. A and F original figures have been cropped to remove excess of empty space.

In the transverse section of the polyhedral tube, the plates become narrow at the continuous lateral edge (Figures 2C, 2E, and 2F; Video S1). In plane view, the midlines are convergence zones of two alternating individual plates (Figure S3A). We, therefore, interpret the gap close to the center of a face as the midline cross-section (Figure 2F). Some specimens apparently show more than two layers, but this is duplication due to fragmentation and folding after burial compression (Figures 1F, 1G, and 2F; Video S1).

Video S1. 3D rendering of micro-CT with synchrotron light source of Sample GP/1E 574a, related to Figure S7

Scale in Figure 2E.

Download video file^{(3.7MB, mp4)}

Raman spectroscopic, scanning electron microscopy, and energy-dispersive X-Ray spectroscopy

Raman spectroscopic mapping was employed to determine the composition of the skeleton. This analysis reveals that both calcite and amorphous carbon are abundant throughout the sclerites (Figures 3A and 3B; Table S5; see Figure S3 for original sample). The red staining surrounding the skeletal margin is revealed to be composed by Fe-(oxyhydr)oxide (Figures 1A, 3A, and 3B), particularly oxidized pyrite framboids, as shown by SEM imaging and EDS spectra, and localized areas of the skeleton are silicified (Figures 3C and S9).

Micrographs of microstructure of *Corumbella* skeleton, Raman mapping and scanning electron microscopy (SEM) images

Samples CAP/1F 14 (A) and CAP/1A 1022 (C). The cutting direction of the original samples that yielded sections in A and C is available in Figures S3B and S3D. The area shown in C is delimited in Figure S4B. (A) PPL image of tube longitudinal section, with inset showing region imaged with Raman maps (B) - carb-carbonate, G band of amorphous carbon and Fe-(oxyhydr)oxides. Arrowhead indicates Fe-(oxyhydr)oxides film in A. (C) Backscattered electron (BSE) image of tube longitudinal section showing partially silicified rings (arrowhead-dark gray areas) and pyrite pseudoframboids (inset) between ring layers. Scale bars: 20 μm. (A-C) original figures have been cropped to remove excess empty space.

Electron backscatter diffraction

EBSD was used to further investigate the morphology, composition, and crystallography of crystals forming the skeleton. This analysis shows that the skeleton is formed by subhedral prismatic, anhedral microspar, and sparry calcite crystals with mosaic, and subordinately, palisade textures at the sclerite margin (Figures 4B, 4C, 4G, 4I, 4J, S4B, and S4F). Diagenetic dissolution of the terminations of such crystals creates the apparently irregular surface of the sclerites, and alteration yields the brightly luminescent margins (Figure S4B). Intracrystalline dissolution is also noted within crystals (Figure 4B).

EBSD analysis shows that sparry calcite crystals have a dominant c-axis orientation, with a limited variability, at a low angle to the long axis of Corumbella, almost parallel to the sclerite surface at the measurement point (Figure 4L). The pole figure of <10-10 > axes has three pole maxima and the pole figure of <10-14 > axes has a repetition of each domain, both patterns associated with calcite symmetry (Figure 4L). The distribution of axes and corresponding crystallographic orientation map (Figures 4K and 4L) reveals a strong preferential crystallographic orientation of <10-14 > axes and the c-axis, as confirmed by a map of the inverse pole figure orientation (Figures 4M and 4O). Larger crystals belonging to other crystallographic domains occur away from this region (Figures 4J–4L).

Notably, EBSD analysis reveals relics of micritic aragonite enclosed within the sparry calcite crystals, forming a poikilotopic texture (Figures 4C and 4G). Aragonite micritic cement occurs between stacked layers (Figures 4C, 4D, S4B, and S4F). There is no preferred orientation of the aragonitic relics measured in either crystallographic orientation maps or pole orientation of the a, b, and c axes (Figures 4D and 4E).

Electron microprobe analysis

EPMA was employed to determine the concentration of targeted elements in different parts of the skeleton and in the carbonate from the host rock. Measurements at the central part of the plates and rings (Figures S10 and S11; Tables S6–S10; n = 41) reveal elevated Calcium (mean = ca. 39 wt %) and Strontium (mean = ca. 11,800 ppm or 1.18%) relative to the sclerite margins. Sr concentration is lower at the sclerite margins (mean = ca. 6,190 ppm) compared with the central portion of the sclerites. Mg, Mn, and Fe are notably concentrated at the skeleton margins relative to the inner region (means of ca. 160, 44, and 570 ppm, respectively). The carbonate from the host rock (n = 12) has the lowest Sr values (mean = ca. 2,590 ppm). Mn and Fe have means of ca. 830 and 3390 ppm, respectively. The concentration of Mn and Fe in the skeleton margins and in the host rock carbonate is consistent with the enhanced CL luminescence in these regions.

Discussion

A cataphract skeleton formed by controlled biomineralization

The sclerites are independent calcareous plates and rings regularly organised, usually imbricated and stacked in at least two layers (Figures 1B, 2A–2F, and S5; Video S1). Sclerites formed as repeated elements with a sigmoidal cross-section, and each layer has a regular and divergent manner of imbrication, to form a cataphract skeleton (Figures 1A, 1B, 2B, 2D, and 2E). Slight variations of sclerite shape can be explained by variability in the position/angle that sclerites created during compaction. Since sclerites articulate, closely-spaced sclerites are offset along their length and/or rotated with respect to each other to yield cross-sections with different shapes (Figure 2D-III). Plates alternate along the midline of each tube face, producing an articulating axis of plates, with imbricated rings grading into imbricated plates (Figure 2A).

Although the sclerites of Corumbella are now preserved as neomorphic low-Mg calcite, original aragonitic mineralogy is suggested by both elevated Sr content (relative to the host rock carbonate) and the presence of aragonitic relicts embedded in neomorphic calcite ‒ both widely accepted criteria for identifying the primary composition of carbonate skeletons.¹³^,¹⁴ Multiple regions of sclerites have been analyzed yielding a limited number of preserved, nano-scaled, aragonitic relicts (Figures 4F and 4G), so accounting for the limited data points measured in EBSD that create a scattered distribution (Figure 4E).¹⁵ The discovery of the material with very low alteration could yield a direct measurement of more relicts, preserving a wider area of the sclerites. In the Ediacaran, preserved aragonite had been only reported to date from the microfossil Protolagena,¹⁶ while a primary aragonitic composition for Namacalathus and Cloudina has been proposed based on isotopic proxies.¹⁷

Uncertainties remain as to whether some Ediacaran skeletal taxa were originally biomineralized. For example, Yang et al.¹⁸ questioned the biomineralization of cloudinids, while Shore and Wood¹⁹ showed that they had a mineralized and flexible skeleton. Aragonite can precipitate as cement after the death of organisms, preserving organic remains. For example, modern siboglinids (marine polychaete annelids) can be coated by aragonite crystals after death at hydrothermal seeps,²⁰ where the inorganic aragonite envelopes the organic tube replacing organic layers in the ‘rooted’, proximal part of the tubes within the sediment.²⁰ A similar origin for the aragonite in Corumbella is not supported, however. First, calcite crystals have a consistent c-axis alignment almost perpendicular to the tube main axis. Second, preservation is via a film of framboidal pyrite pseudomorphs coating the sclerites (that may indicate a decay-prone tissue in the external part of the sclerites – see discussion below), as would not be expected from aragonite replacement/embedding rather than original skeletal material.

An alternative explanation that the bilayered wall was created by dissolution is also highly unlikely. We show 3D specimens with consistently articulated sclerites forming bilayered walls with a rough inner surface (e.g., Figures 1B, 2E, 2F, S5B, and S8D–S8F; Video S1), supporting a primary biological feature rather than a diagenetic dissolution origin for the wall layering. We also recognise a consistent architectural pattern of skeletal microstructure that is noteworthy for its organizational complexity, namely repetitive articulating imbricated elements with constant shape, stacked in layers with consistent and inverse imbrication patterns. Moreover, the presence of sediment and aragonitic cement between skeletal layers (Figures 1, 3, and S4) would not be expected to have been formed during a stage of skeleton dissolution prior to sediment lithification. In such a scenario, the cavities would be filled with spar cement, which is absent here. Finally, alteration has impacted the margins of the sclerites more severely, as demonstrated by the distinct luminescence pattern (Figure 1) coupled with EPMA showing a decrease of Sr content and an increase of Mn content toward the edges of each sclerite (Table S10).

We note a preferential co-alignment of the c-axis of the calcite crystals within the sclerites almost perpendicular to the tube length (Figures 4K and 4L). The transitional change of crystallographic orientation of the c-axis (Figure 4L) from right to left in the crystallographic orientation map (Figure 4K) might reflect the variation in sample sectioning direction. Large crystals closer to the more altered sclerite margin possess more random crystallographic orientations (Figure 4K, upper left corner). Since diagenetic recrystallization commonly yields randomly orientated crystals,²¹ the large crystals may reflect stronger recrystallization. It is likely that the original crystallographic orientation has been preserved in less altered regions (see Data S1 for an appraisal of the orientation patterns of other taxa). Original textures can be finely preserved during neomorphism since organic material can be partially degraded, permitting percolating solutions to precipitate calcite within voids.²² Positive feedback of dissolution of aragonite readily followed by local supersaturation and precipitation of calcite produces pseudomorphs with inherited crystallography after epitaxial growth.²²^,²³ It has been proposed that acicular carbonates can be replaced by fibrous calcite that retains the original c-axis orientations.²⁴ When porosity is reduced, e.g., by locally preserved organic material,²⁵ the dissolution-reprecipitation front is inhibited,²³ and aragonite relicts are preserved. Poles are organized in subgroupings expressed in a slightly spread pattern (Figure 4L), thus indicating a subtle variability in orientation. This might have been created by the fact that sample sectioning is not always exactly transverse to the sclerite. We can rule out the effect of tectonic deformation since each subgrouping is comprised of plots of several crystals and the crystallographic pattern is not homogeneous across the analyzed area (compare left upper corner with center of Figure 4K), so there is no consistent orientation parallel to dominant stress fields. Conversely, we would expect that each deformed crystal would have its own subgrouping with a spreading pattern, but each crystal has a consistent orientation pattern (Figure 4K).

A composite calcareous-organic skeleton is suggested by the Raman data. Organic tissue embedded within the calcareous skeleton would be recalcitrant and yield amorphous carbon²⁶^,²⁷ (Figure 3B). An organic template²⁸ into which the sclerites were embedded can be inferred by the presence of oxidized pyrite framboids now present as Fe-(oxyhydr)oxides (Figure 3). Pyrite framboids are known to form preferentially and rapidly during very early diagenesis associated with decaying labile organic matter.²⁷ The presence of soft tissue attached to the skeletal plates might account for the integrity of the cataphract skeleton, the decay of which would account for commonly disarticulated specimens (Figures 2G and S8B). Compaction has yielded some fragmented specimens (Figures 1F and 1G).

The replacive, diagenetic calcite likely mimics an originally laminar organo-aragonitic microstructure of the Corumbella skeleton. Orientated crystals can form when several crystals nucleate, grow preferentially along the c-axis, and then coalesce,¹⁴ as might be expected for the original aragonitic microstructure of Corumbella. It is possible that organic envelopes and surfaces enable the growth of aragonite crystals with consistent c-axis alignments, given that organic material controls biomineralization by providing confined volumes, in which ionic conditions favor aragonite precipitation over calcite.²⁸^,²⁹^,³⁰^,³¹ In Corumbella, the crystallographic pattern is similar in different crystals both above and below a zone with voids (Figure 4K), and is laterally continuous in neighboring sclerites which may represent an organic-rich layer situated at the contact between two mineralized layers (Figure S4B). Continuity of crystallographic pattern across skeletal layers occurs in calcitic and aragonitic microfabrics.³² The co-alignment of <0001> and <10-14 > axes suggests a highly ordered sheet structuring.³³ We conclude that Corumbella skeleton is now formed by replacive sparry calcite crystals of a probably original laminar microstructure of aragonite. This type of layered skeletal carbonate microfabric has a stepped process of formation that is biologically controlled.²⁹^,³⁴ Mineralized layers are progressively stacked upon previously deposited layers. This process (the so-called ‘common strategy’ for carbonate layered skeletal microfabrics) is controlled by the mineralizing ectodermal epithelium, where organic material delimits the resulting layer and the shape of the organic envelope molds the crystal shape.²⁹ Even if it is assumed that the pyritic film along the sclerites margin represents an organic layer coating the sclerites (template for biomineralization) that are derived from the epidermis (as similarly proposed for chancelloriids³⁵), it is not possible to infer the position of sclerites relative to the epidermis itself.

The overall morphology of Corumbella shows a directional polarity,⁶ and this is also manifested by the consistent directional imbrication of the plates and rings (Figures 1A, 2A, 2B, 2E, and S8F) and the presence of a possible set of thick rings at the tube base (Figures S4A, S4B, and S8F). This polarity has been interpreted as oral-aboral,⁶ but is here changed to ‘proximal-distal’ as we question the affinity of Corumbella to Cnidaria (see below; Table S1). Two orthogonal planes across the midlines divide the skeleton into four quadrants, yielding 4-fold radial symmetry⁵^,⁶ (Figure 2C). The consistent shape and organization of the sclerites, as well as regular microfabric and consistent crystal orientation²⁸ shows that considerable biological control was exerted over crystal growth and skeletal formation in Corumbella.

Appraisal of Corumbella biological affinities

It has been proposed that Corumbella could be related to scyphozoan conulariids based on the 4-fold radial symmetry (related to polygonal cross-section) plus the presence of lateral edges (corners in conulariids), and midlines³^,⁴^,⁶^,⁸^,⁹ (see Table S2 for a summarized comparison). As for the alternation of plates at either sides of midline in Corumbella, conulariids have an alternation of skeletal features (transverse ribs) along either side of the midline (e.g., Climacoconus⁷). We consider the tube polygonal cross-section of Corumbella and the midlines as valid morphologies, contra Walde et al.¹⁰ (see Data S1).

However, while conulariid tubes have a polygonal cross-section, Corumbella tube grades from a uniseriate proximal region with an almost circular cross-section, formed by rings, to a distal region with polygonal cross-section and 4-fold symmetry, formed by plates. The Ordovician conulariid Metaconularia anomala has a variation of faces number along the periderm,³⁶ but neither a variation of structures occurs nor is there a change from a circular to a polygonal cross-section, as found in Corumbella. The polygonal cross-section (and, consequently, the associated squarish corner in conulariids or lateral edge of Corumbella) is not exclusive to either conulariids or cnidarians (e.g., Hydrozoa). For instance, polygonal tubes are also shared by some annelid serpulids³⁷ and by Sinotubulites.³⁸^,³⁹ Additionally, radial (4-fold) symmetry neither unequivocally relates Corumbella to conulariids, nor places this genus within the Cnidaria.

Bilateral symmetry could have evolved earlier than the bilaterian common ancestor⁴⁰ since polyps of anthozoan cnidarians, for instance, have biradial and/or bilateral symmetry.⁴¹^,⁴²^,⁴³ Moreover, some possible bilaterians are known to have radial symmetry (e.g., cycloneuralians and echinoderms), including the terminal Ediacaran Namacalathus.⁴⁴ The type of symmetry, either radial or bilateral, has been associated with sessile and vagile habits, respectively, and so might be only a weak trait for phylogenetic reconstitutions.⁴⁵ The radial symmetry of Corumbella is consistent with a sessile lifestyle.

Conulariids have a single-unit skeleton (periderm) and thus midlines are regions of continuous skeleton. The periderm was organic or organo-phosphatic and has a generally consistent internal layering (macro- and microlamellae) among transverse ribs and the wall is smooth internally.⁴⁶ The periderm has internal carinae formed by thickening. Cambrian phosphatic and soft-bodied conulariid-related taxa (Olivooides and carinachitids) are double-layered, with continuous walls that are smooth internally.⁴⁷^,⁴⁸ The lamellar nature of Corumbella skeleton was used to support a conulariid affinity,⁶ but these lamellae have not been ruled out as platy calcite that now builds the skeleton, or host rock aluminosilicate crystals parallel to the skeleton wall surface. Their scale is also different from the lamellae in conulariids.⁴⁶ Corumbella likely possessed a laminar microfabric, but this feature is not exclusive to conulariids since it is also found in possible cnidarians and bilaterians, for example.⁴⁴ It has been interpreted that plates with pores and papillae would form the skeleton of Corumbella, as in conulariids,⁹ but these features could be calcite dissolution artifacts.¹⁰ In contrast to previous work,⁵^,⁶ we think that a conulariid affinity to Corumbella is now unlikely, as we show that (1) Corumbella has an inferred original aragonitic skeletal composition, (2) the skeleton is multi-element, formed by independent articulating isolated or more commonly imbricated sclerites forming two layers (i.e., cataphract skeleton), with open midlines as being articulating axes (Figure 2; Table S1), (3) internal lamination is restricted to single sclerites, (4) the skeleton has a rough internal surface, (5) the skeleton is devoid of any internal thickening, and (6) there is a more gradual variation in the width of the Corumbella tube compared to the abrupt changes seen in conulariid periderm.⁴ While it has been suggested that articulated annular elements could form the Corumbella skeleton,⁴⁹ it is not clear whether the authors consider such rings as being independent elements; most likely these were interpreted as being continuous.⁴⁹

The cataphract organization of Corumbella is also not consistent with extant and fossil cnidarians (see Table S2). The morphological variation along the tube (uniseriate proximal region with rings grading to quadriseriate distal region with plates), a bilayered wall with regular and inverse imbrication mode of the sclerites in each layer, a multi-element articulated imbricated skeleton, and an alternation of independent, articulated plates along the midlines (articulation axes) is not consistent with a cnidarian affinity. Staurozoans, cubozoans, and living scyphozoans are unmineralized⁵⁰ (including Cambrian taxa⁵¹). Although Corumbella shares an aragonitic composition with hydrozoans,³⁴^,⁵² the latter have a massive skeleton,³⁴ in opposition to the multi-element skeleton of Corumbella. Corumbella composition and microstructure also differ from the Cambrian Sphenothallus.⁵³ Although several anthozoans have a multi-element skeleton of sclerites/spicules, some have a central axis in the skeleton.⁵⁴ Polyps of the subclass Ceriantharia,⁵⁵ probably one of the oldest extant lineages of Cnidaria,⁴³ form tubes that are constructed by independent, overlapping rings built by filaments of ptychocysts (with a protein matrix⁵⁶), but the absence of more detailed studies on the composition of the tube in Ceriantharia limits further discussion⁴²^,⁵⁵ (Table S2). The earliest probable octocorals are from the Cambrian.⁵⁷^,⁵⁸ For example, Echmatocrinus brachiatus⁵⁷ possessed sclerites, but their morphology, arrangement, and composition are different from Corumbella. Other Cambrian anthozoan candidates are unmineralized or possess internal thickenings.⁷ Ediacaran putative anthozoans possess internal cross-walls and are possibly unmineralized,⁷ thus differing from Corumbella. Neither the massive skeleton of both scleractinians and blue corals⁴ occurs in Corumbella. The platelets, scales, and shingles⁵⁶^,⁵⁹^,⁶⁰^,⁶¹ of some cnidarians are only surficial, and do not build an articulated bilayered skeleton as in Corumbella. Since the original habit of aragonite crystals from Corumbella skeleton is not currently known, any further comparison with skeletal microfabrics of cnidarians is not possible.

Alternatively, it has been proposed that Corumbella was a sinotubulitid or a sabelliditid polychaete¹⁰ (see Table S3). Sinotubulitids possessed external irregular, occasionally bifurcating ornamentations (‘ribs’) (Figures 9A–9E of Walde et al.¹⁰; Figure 3B of Chen et al.³⁸) and had a continuous wall with smooth interior (Figures 7C–7G of Walde et al.¹⁰). Some 3D specimens with likely circular cross-sections and more regular annulations shown by Walde et al.¹⁰ (e.g., their Figure 7A) could be proximal parts of Corumbella (e.g., Figures S1B, S3B, S4, S8C, and S8D) or, alternatively, a different taxon. Sabelliditids have a one-piece tube with continuous wrinkles in the longitudinal section.⁶² But by contrast, Corumbella possessed sclerites with a regular non-bifurcating external pattern (Table S3; Figures S1A and S3A), and non-continuous wall with rough inner surface (Figure 1B). A polychaete annelid affinity is unlikely since the cataphract skeletal architecture of Corumbella is not found in polychaetes, and siboglinids are unmineralized²⁰^,⁶³ (see Data S1 and Table S4 for further comparison).

Corumbella has also been compared to the problematic organic and flexible tubular Cambrian fossil Onuphionella, and to the putative annelid Eoalvinellodes annulatus¹⁰, but this is not supported by morphological and compositional evidence. Onuphionella skeleton purportedly agglutinated muscovite flakes,⁶⁴ and Eoalvinellodes annulatus ornamentation is irregular, sometimes bifurcating and there is no evidence for tube’s flexibility (Figures 18A–18C of Georgieva et al.⁶⁵), which are in marked contrast to the regularity and non-bifurcating morphology of Corumbella plates and rings (Figure S3), and to Corumbella tube inferred flexibility (Figure S8A).

Another tubular Ediacaran fossil made up of independent elements is Costatubus, that is a late Ediacaran tubular fossil found in the Wood Canyon and Deep Spring formations, USA.⁶⁶ However, this genus differs from Corumbella, as Costatubus has a single wall, with smooth lumen. The building elements of Costatubus only slightly overlap, are continuous, barrel-shaped, with a seemingly more constant thickness relative to Corumbella sclerites in tube longitudinal section (not a sigmoidal shape as in Corumbella). Additionally, the tube has circular cross-section.

A cataphract organization creating a scleritome is established for articulating small shelly fossils (SSFs), such as mineralized plates, shells, and spines of bilaterians and still enigmatic taxa, which appeared in the latest Ediacaran.⁶⁷^,⁶⁸^,⁶⁹ Small carbonaceous fossils (SCFs) (ecdysozoan-like organic sclerites⁷⁰) are also known from the terminal Ediacaran. The earliest complete cataphract skeletons (scleritomes) known have been derived from exceptional preservation in early Cambrian strata.⁷¹^,⁷² In the Ediacaran-Cambrian transition (including the Cambrian Stage 2), SSFs are dominantly assigned to lophotrochozoans,⁶⁸^,⁷³ such as the tommotiids,⁷² molluscan halkieriids,⁷¹ and putative lophotrochozoan cambroclavids,⁷³^,⁷⁴ as well as probably to Chaetognatha and other taxa with undetermined affinities⁷³ (see Table S11). It was only later in the Cambrian Stage 3 that biomineralized ecdysozoans and deuterostomes radiated.⁷³ Machaeridians (annelids that appeared in the early Ordovician) also possessed a cataphract skeleton.⁷⁵^,⁷⁶

Biomineralized skeletal elements are also found in taxa with more basal metazoan affinities. Cambrian chancelloriids, which have been long interpreted as poriferans, possessed a soft body with external sclerites, but these did not form a sensu strictu cataphract organization, that is imbricated, articulating elements. Recently, it has been shown that chancelloriids sclerites had an outer organic layer, that was interpreted as an organic template (derived from the epidermal integument) for biomineralization of the internal, aragonitic, fibrous layer.³⁵ This evidence points to a eumetazoan (and therefore epitheliozoan), rather than poriferan affinity.³⁵ Our interpretation that Corumbella sclerites also possessed an outer organic template would support the placement of this taxon within the Eumetazoa.

The possibly laminar aragonitic microfabric of Corumbella is reminiscent of carbonate laminar microfabrics of lophotrochozoan skeletons, such as in bryozoans and molluscs.²⁹^,³³^,⁷⁷ However, laminar microfabrics are also found in other metazoans, like cnidarians. Indeed, laminar aragonitic skeletal microfabric appears to be shared by cnidarians and bilaterians.⁴⁴

Corumbella is the oldest metazoan described to date with a complex cataphract skeleton with biologically-controlled biomineralization and may represent, along with potentially Namacalathus⁴⁴^,⁷⁸ and possibly Cloudina,⁷⁹ the earliest fauna of biomineralized bilaterians.

Although the cataphract organization is reminiscent of Cambrian bilaterians, unequivocal evidence for a bilaterian affinity has not been found to date in Corumbella. Although we provide a detailed morphological reconstruction for Corumbella, it is crucial at least to infer hypothetical ancestors through a phylogenetic study before any evolutionary interpretations of body plans can be considered.⁸⁰ Morphological analyses of Ediacaran metazoans often fail to accommodate them within modern phyla owing to their basal characters, which can often be similar or shared with basal groups of other phyla, as well as to the lack of soft-tissue preservation.⁸¹^,⁸² Thus, most Ediacaran and Cambrian eumetazoans can often only be assigned to total groups.⁸² For example, basal bilaterians would have had features conserved from Eumetazoa, unique characters, as well as some characters shared by the extant members of the phyla.⁸²^,⁸³ The morphogenetic diversification of bilaterian phyla body plans might occur only in the Phanerozoic, with the evolution of crown groups.⁸² Corumbella features conform to this rationale for basal eumetazoans, as it possessed features usually attributed to cnidarians (polygonal cross-section and radial symmetry), as well as a cataphract skeleton, as found in some bilaterian and problematic, Cambrian taxa.

Biologically controlled biomineralization and cataphract skeletons: Ecological implications

Corumbella possessed strongly biologically controlled calcareous biomineralization that would require a genetic control for the development of: (1) repeating sclerites, formed possibly by vertical accretion of orientated organic-rich aragonite crystals embedded within an organic-matrix, (2) changing of morphology from an uniseriate region formed by continuous rings to a region with repeated increments of four articulating plates each, (3) controlled sclerite shape, (4) sclerite growth cessation allowing articulation and alternation at the midlines, (5) sclerite imbrication consistently inverse in different layers, and (6) a fixed number of skeletal layers (Figures 2A–2F). This level of skeletal organization, and thus biological control, is not seen in either extinct (including Ediacaran and Cambrian cnidariomorphs summarized by Van Iten et al.⁷ and Kouchinsky et al.⁷³) or living cnidarians (Table S2), nor other known Ediacaran skeletal metazoans³⁸^,⁸⁴^,⁸⁵^,⁸⁶ (Table S3).

It has been considered that biomineralizers expanded to potentially low carbonate-saturation clastic settings only in the Cambrian, with the development of evolutionary constraints for biomineralization.⁸⁷ We hypothesize that the occurrence of Corumbella in mixed siliciclastic-carbonate settings, and in predominantly clastic beds thus also supports a strong control of biomineralization that enabled the colonization of siliciclastic settings in the latest Ediacaran. This proposal is consistent with the proposal that the ‘Cambrian radiation’ was a transitional event with roots in the Ediacaran.⁶⁸^,⁸⁸

Corumbella had a complex skeleton, relative to other Ediacaran biomineralizers, that implies a strong biological control over biomineralization. Corumbella serves a datum (in a growing line of evidence) that implies the Cambrian radiation of bilaterians may have had deep roots.⁷⁸^,⁷⁹ If true, we might also expect that flexibility (Figure S8A), efficient support, protection against predation, feeding efficiency, and motility in biomineralizing taxa (behaviors that are correlated with biomineralization and biomechanics, particularly of multi-element skeletons) to have emerged by the end of the Ediacaran Period. Future work, in the form of new fossil discoveries or computational analyses, may test these hypotheses.

Limitations of the study

Previous work has helped to elucidate the morphology of Corumbella,⁶ and here we develop this further with the finding of a cataphract skeleton reminiscent of early Cambrian SSFs, which comprise both bilaterians and problematic taxa. But establishing the affinity of Corumbella is still challenging. This limitation is common for late Ediacaran mineralized taxa and is best resolved when soft tissues are found in association with skeletal remains.⁷⁸^,⁷⁹ Our detailed morphological reconstruction with potential new findings of soft tissues could yield new insights into the affinities of Corumbella.

STAR★Methods

Key resources table

REAGENT or RESOURCE	SOURCE	IDENTIFIER
Deposited data

RAW micro-CT data	This study	Mendeley Data (https://doi.org/10.17632/y2rb6sfvcz.1)
RAW micro-Raman spectroscopy data	This study	Mendeley Data (https://doi.org/10.17632/y2rb6sfvcz.1)
RAW EBSD data	This study	Mendeley Data (https://doi.org/10.17632/y2rb6sfvcz.1)

Software and algorithms

Renishaw WiRE™ 4.1	Renishaw	https://www.renishaw.com/en/raman-software--9450
Oxford Instruments AZtecSynergy	Oxford Instruments	https://nano.oxinst.com/products/aztec/aztecsynergy
Oxford Instruments HKL Channel5	Oxford Instruments	https://nano.oxinst.com/products/aztec/aztechkl
VGstudio Max 2.1	Volume Graphics	https://www.volumegraphics.com/en/products/vgsm.html
ImageJ 1.46r	National Institutes of Health, USA	https://imagej.nih.gov/ij/
Microsoft Excel	Microsoft Corporation	https://www.microsoft.com/en-us/microsoft-365/microsoft-office

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Resource availability

Lead contact

Further information and requests for additional data should be directed to and will be fulfilled by the lead contact, Mírian Pacheco (forancelli@ufscar.br).

Materials availability

This study did not generate new unique reagents.

Experimental model and subject details

Samples are housed in the Palaeontological Collections of the Laboratório de Paleobiologia e Astrobiologia, Universidade Federal de São Carlos, Sorocaba, Brazil (Samples: CAP/1A 1020, which corresponds to CAP/1F 11; CAP/1F 12; CAP/1A 1022; CAP/1A 1023; CAP/1A 1024; CAP/1A 1025; CAP/1A 1026; CAP/1A 1071; CAP/1F 14), of the Instituto de Geociências, Universidade de São Paulo, São Paulo, Brazil (Samples: GP/1E 4182, GP/1E 574a, GP/1E 4210, GP/1E 5186 and GP/1E 5819), and of the Departamento Nacional de Produção Mineral (DNPM), currently Agência Nacional de Mineração (ANM), Rio de Janeiro, Brazil (Sample DGM-5601-I).

Method details

Cathodoluminescence

Luminescence was imaged using highly polished thin sections and embedded blocks in resin using a Cathodoluminescence Cold Cathode CITL 8200 MK3A coupled with a Nikon microscope in the School of GeoSciences, University of Edinburgh. We used a x10 objective lens, current of 900-1000 A and voltage of 25-30 V.

Raman spectroscopy

Thin sections were imaged using Raman micro-spectroscopy at the Bioimaging Facilities, School of Engineering, University of Edinburgh. We used a Renishaw micro-Raman system mounted on optical microscope and laser source of 785 nm excitation line. For map acquisition, equipment was calibrated by the Si band (520.7 cm^-1), then measurements were performed with a x20 magnification objective lens, with an exposure time of 10 s, and laser power of 10%, between 300-1700 Raman shift/cm⁻¹. We processed data in the software Renishaw WiRE^TM 4.1.

Electron microscopy

Backscattered electron (BSE) imaging and energy-dispersive X-ray spectroscopy (EDS) analyses were made using a carbon coated highly polished embedded block (20 kV voltage and 6.8 and 6.9 mm working distances). Later, this sample was further polished and recoated for electron backscatter diffraction (EBSD). We used 15 kV voltage, 3.0-3.5 nA current, a 70° pre-tilted holder and a Hough Resolution of 100, 9 bands (edges) and indexing for both calcite and aragonite phases. We acquired data with Oxford Instruments AZtecSynergy software, and later processed data in the Oxford Instruments HKL Channel5 software with Tango and Mambo modules. BSE, EDS and EBSD analyses were performed in a Carl Zeiss SIGMA HD VP Field Emission SEM, an Oxford AZtec ED X-ray analysis, and an Oxford AztecHKL EBSD system at the School of GeoSciences, University of Edinburgh.

Electron probe micro-analysis

A highly polished thin section and an embedded block, both carbon coated, were analysed using electron probe micro-analysis (EPMA) in a Cameca SX100 instrument at the School of GeoSciences, University of Edinburgh. We used a beam size of 3 μm, voltage of 5 kV, and currents of 2 nA and 60 nA. A highly polished thin section was carbon coated and analysed using EPMA in a JEOL JXA-8530F instrument at the Institute of Geosciences, University of São Paulo. We used beam sizes of 2 μm, 2.5 μm, 3 μm and 5 μm, voltage of 15 kV, and current of ca. 2E-008 A.

Micro-computed tomography (micro-CT)

Micro-Computed Tomography (micro-CT) measurements were carried out by means of synchrotron radiation at the former beamline W2 for materials science at the storage ring DORIS (DESY, Hamburg, Germany). The micro-CT data of the specimen were collected using a beam-energy of 35 keV and a lens coupled CCD camera built of 3056x3056 pixels with a physical pixel size of 12 μm. An optical magnification was given by modifying the position of the lens (Nikkor; Nikon GmbH, Nikon Professional Services, Tiefenbroicher Weg, Düsseldorf) between the scintillator (CdWO4, with a 450 μm thickness) and the CCD camera. An effective pixel size of 3.25 μm was achieved in the recorded images for the specimen to fit in the field of view. Data processing has been made using the softwares VGstudio Max and ImageJ.

Quantification and statistical analysis

Statistical analyses of electron probe micro-analysis were made in the software Microsoft Excel by determining minimum, maximum, mean and standard deviation values. Statistical details of experiments can be found in the results section of the main text and in Table S10 of the supplemental information.

Acknowledgments

G.L.O. and M.L.A.F.P. acknowledge funding from the “Fundação de Amparo à Pesquisa do Estado de São Paulo” (FAPESP) PhD scholarship, grant #2017/21584-1, the FAPESP BEPE scholarship, grant #2019/10929-3, which supported a visiting scholarship to the University of Edinburgh, and the “Conselho Nacional de Desenvolvimento Científico e Tecnológico” (CNPq) PhD scholarship, grant #141115/2017-3. G.L.O. acknowledges funding from the “Fundação de Amparo à Pesquisa do Estado de São Paulo” (FAPESP) Post-doctoral scholarship, grant # 2021/07007-7, under the supervision of Prof. Marcia Rizzutto. M.L.A.F.P acknowledges the FAPESP Regular Project, grant #2022/10829-1, and the FAPESP grant #2021/05083-8, for allowing the dissemination of the research area of this manuscript. G.L.O., R.W., G.R.R., and M.L.A.F.P. thank funding from the FAPESP Thematic Project #2016/06114-6. R.W. acknowledgsles support from NERC-NSFC grant NE/P013651 and from NERC NE/T008458/1. S.N.S acknowledges funding from the FAPESP Regular Project #2019/03552-0. G.R.R. acknowledges the Human Resource Program of The Brazilian National Agency for Petroleum, Natural Gas, and Biofuels – PRH 43.1-ANP, supported with resources from oil companies considering the contract clause nº 50/2015 of R, DandI of the ANP. G.M.E.M.P. acknowledges CNPq PhD scholarship #142246/2019-0. We acknowledge FAPESP (grant #2009/02312-4) and NAP/Astrobio (PRP-USP) for financial support to the micro-CT experiment. This work was carried out with the support of the Coordination for the Improvement of Higher Education Personnel – Brazil (CAPES) – Financing Code 001. We are grateful to the PROAP/CAPES from the PPGERN (Programa de Pós-Graduação em Ecologia e Recursos Naturais-UFSCar) for financial support to pay the publication fee, and we thank the financial support from the Programa de Pós-Graduação em Ciências Biológicas (Zoologia), Instituto de Biociências, Botucatu, UNESP. We thank the Programa de Pós-Graduação em Ecologia e Recursos Naturais (UFSCar), the Programa de Pós-graduação em Geoquímica e Geotectônica (USP), and the Programa de Pós-Doutorado of the Institute of Physics, University of São Paulo. We are grateful to the Departamento Nacional de Produção Mineral (DNPM), currently Agência Nacional de Mineração (ANM), Rio de Janeiro, for making its Palaeontological Collection available for fossil observation. We thank Irma Tie Yamamoto and Ana Lucia Desenzi Gesicki (ANM) and the Receita Federal for the authorization for the transportation of samples. We acknowledge the synchrotron light source Doris III (DESY, Hamburg, Germany), a member of the Helmholtz Association (HGF), and the Local Contact for assistance in measurements in beamline W2. We thank the ID19 beamline at the European Synchrotron Radiation Facility (ESRF), Grenoble, France, for the analyses. We are grateful to Local Contact at ESRF for providing assistance in using beamline ID19. We acknowledge the Laboratório de Microssonda Eletrônica (IGc-USP) and staff (Prof. Gaston Rojas, Prof. Renato de Moraes, Prof. Rogério Azzone, and Marcos Mansueto) for technical support during EPMA analysis. We thank Bruno Becker-Kerber, Esthella Ferreira Silva, Kamilla Borges Amorim, Jhon Willy Lopes Afonso, Thibault Martin Le Guelvout, and Alessandro Marques de Oliveira for fieldwork support. We thank Mike Hall, Renato Carvalho, Amy Shore, Nicola Cayzer, John Craven, Allison McDonald, Chris Hayward, Marco Stockmar, Douglas Galante, Fabio Rodrigues, Paulo Sergio Gomes Paim, Marinez Oliveira dos Santos, Lauro Moreira Rosa, Luiz Eduardo Anelli, Martin Dierolf, and Bruno Becker-Kerber for technical support; the latter, Nicola Cayzer, Andrey Yu. Zhuravlev, and Fernando Rodrigues da Silva for invaluable discussion; Júlia Soares d’Oliveira for the palaeoart/illustrations; and Juliana de Moraes Leme Basso and Ivone Cardoso Gonzales for the access to fossil collection and research facilities of the Institute of Geosciences, University of São Paulo. We acknowledge Pidassa Bidola, Marco Stockmar, Klaus Achterhold, Franz Pfeiffer, Mírian L.A.F. Pacheco, Carmen Soriano, Felix Beckmann, and Julia Herzen, authors of the paper “Absorption and Phase Contrast X-Ray Imaging in Paleontology Using Laboratory and Synchrotron Sources”, published in the journal “Microscopy and Micro-analysis”, v. 21, issue 5, pp. 1288-1295, for having permitted reproduction of Figure 3D via “Cambridge University Press”/RightsLink license. Finally, we are also grateful to Dr. Alessio Bolognesi, iScience Editor, and to Dr. James Schiffbauer and other anonymous reviewers for their contribution to the manuscript.

Authors contributions

G.L.O., R.W., G.R.R., and M.L.A.F.P. designed the research. G.L.O., R.W., M.L.A.F.P., P.B., F.P., and J.H. performed the experiments. G.L.O., G.M.E.M.P., P.B., and J.H. processed data. G.L.O., R.W., S.N.S., and M.L.A.F.P. interpreted the results. G.L.O., R.W., and M.L.A.F.P. wrote the paper. G.L.O., R.W., M.L.A.F.P., G.R.R., G.M.E.M.P., S.N.S., P.B., F.P., and J.H. worked in redrafting and reviewing the paper.

Declaration of interests

The authors declare no competing interests.

Inclusion and diversity

We support inclusive, diverse, and equitable conduct of research.

Published: December 22, 2022

Footnotes

Supplemental information can be found online at https://doi.org/10.1016/j.isci.2022.105676.

Supplemental information

Document S1. Figures S1–S11 and Tables S3–S10

mmc1.pdf^{(3.5MB, pdf)}

Table S1. Comparison of morphological features and terminology published for Corumbella and proposed for this study. Table based on Table 1 from Pacheco et al.¹, related to Figures 1, 2, 3, and 4

mmc2.xlsx^{(11.5KB, xlsx)}

Table S2. Comparison of Corumbella and cnidarian features, related to Figures 1, 2, 3, and 4

mmc3.xlsx^{(14.8KB, xlsx)}

Table S11. Comparison of features of Corumbella and of living and extinct bilaterians and extinct possible bilaterians, related to Figures 1, 2, 3, and 4

mmc4.xlsx^{(16.9KB, xlsx)}

Data S1. Supplemental text

mmc5.pdf^{(115.1KB, pdf)}

Data and code availability

•
RAW data from micro-CT, Raman spectroscopy and EBSD analyses have been deposited at Mendeley Data (https://doi.org/10.17632/y2rb6sfvcz.1) and are publicly available as of the date of publication. Accession numbers (DOI) are listed in the key resources table.
•
This paper does not report original code.
•
Any additional information required to reanalyse the data reported in this paper is available from the lead contact upon request.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Video S1. 3D rendering of micro-CT with synchrotron light source of Sample GP/1E 574a, related to Figure S7

Scale in Figure 2E.

Download video file^{(3.7MB, mp4)}

Document S1. Figures S1–S11 and Tables S3–S10

mmc1.pdf^{(3.5MB, pdf)}

Table S1. Comparison of morphological features and terminology published for Corumbella and proposed for this study. Table based on Table 1 from Pacheco et al.¹, related to Figures 1, 2, 3, and 4

mmc2.xlsx^{(11.5KB, xlsx)}

Table S2. Comparison of Corumbella and cnidarian features, related to Figures 1, 2, 3, and 4

mmc3.xlsx^{(14.8KB, xlsx)}

Table S11. Comparison of features of Corumbella and of living and extinct bilaterians and extinct possible bilaterians, related to Figures 1, 2, 3, and 4

mmc4.xlsx^{(16.9KB, xlsx)}

Data S1. Supplemental text

mmc5.pdf^{(115.1KB, pdf)}

Data Availability Statement

•
RAW data from micro-CT, Raman spectroscopy and EBSD analyses have been deposited at Mendeley Data (https://doi.org/10.17632/y2rb6sfvcz.1) and are publicly available as of the date of publication. Accession numbers (DOI) are listed in the key resources table.
•
This paper does not report original code.
•
Any additional information required to reanalyse the data reported in this paper is available from the lead contact upon request.

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PERMALINK

Ediacaran Corumbella has a cataphract calcareous skeleton with controlled biomineralization

Gabriel Ladeira Osés

Rachel Wood

Guilherme Raffaeli Romero

Gustavo Marcondes Evangelista Martins Prado

Pidassa Bidola

Julia Herzen

Franz Pfeiffer

Sérgio Nascimento Stampar

Mírian Liza Alves Forancelli Pacheco

Summary

Graphical abstract

Highlights

Introduction

Results

Optical microscopy

Figure 1.

Cathodoluminescence imaging

Figure 2.

Raman spectroscopic, scanning electron microscopy, and energy-dispersive X-Ray spectroscopy

Figure 3.

Electron backscatter diffraction

Figure 4.

Electron microprobe analysis

Discussion

A cataphract skeleton formed by controlled biomineralization

Appraisal of Corumbella biological affinities

Biologically controlled biomineralization and cataphract skeletons: Ecological implications

Limitations of the study

STAR★Methods

Key resources table

Resource availability

Lead contact

Materials availability

Experimental model and subject details

Method details

Cathodoluminescence

Raman spectroscopy

Electron microscopy

Electron probe micro-analysis

Micro-computed tomography (micro-CT)

Quantification and statistical analysis

Acknowledgments

Authors contributions

Declaration of interests

Inclusion and diversity

Footnotes

Supplemental information

Data and code availability

References

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

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