Research ArticlePALEONTOLOGY

A vanished history of skeletonization in Cambrian comb jellies

See allHide authors and affiliations

Science Advances  10 Jul 2015:
Vol. 1, no. 6, e1500092
DOI: 10.1126/sciadv.1500092
  • Fig. 1

    Gemmactena actinala gen. et sp. nov. (A) Holotype (ELEL-SJ100756A) showing radiating flap-like structures outlined by spokes, comb rows, and oral lappets. Apical organ not preserved. (B) Close-up of small focus area in (A) showing fine striae on spoke surface. (C) Close-up of large focus area in (A) showing remains of comb rows, as well as upper and lower spokes that frame a flap. (D) Paratype (ELEL-SJ081292A). (E) Close-up of focus area in (D) showing rigidity of a spoke with a medial groove (internal view). (F) Close-up of aboral region in (D) showing an ellipsoidal statolith preserved as dark remains surrounded by apical plates. (G) Counterpart of (F) showing complete apical plates detached from each other; remains of organic carbon are partially preserved as a dark band on the statolith. (H) Paratype (ELEL-SJ081366A) showing pointed dome-like apical organ walled by rigid plates (each with a medial groove continuous with a spoke). (I) Aborally compacted specimen ELEL-SJ120375A showing an apical organ and partially dislocated upper spokes (arrows). The apex of the apical organ was truncated and retained in counterpart during splitting. (J) Close-up of focus area in (I) showing distal end of upper spoke, with the kink marked by arrow. (K) Close-up of apical organ in (I); dark, equally spaced bands (arrowheads) radiating from the base of apical organ may represent remains of underlying meridional canals. (L) Close-up of apical organ showing considerable positive relief, presumably due to its rigidity imparted by apical plates (numbered). ao, apical organ; cr, comb row; fp, flap-like structure; ls, lower spoke; ol, oral lappet; os, oral skirt; pl, apical plate; sl, statolith; us, upper spoke. Scale bars, 5 mm (A, D, H, and I); 2 mm (C, F, and G); 1 mm (B, E, and J to L).

  • Fig. 2

    Thaumactena ensis gen. et sp. nov. (A to D), Galeactena hemispherica gen. et sp. nov. (E to I), and Batofasciculus ramificans (J to N). (A) Holotype (ELEL-SJ081427A) showing apical organ, body with rigid spokes (arrows), and oral skirt. (B) Close-up of aboral region in (A) showing arcuate spokes (arrows) and remains of ctenes (arrowheads); dark residues may represent gastric system. (C) Oral region in (A) (counterpart) showing flared oral skirt and membranous tissue supported by spokes (arrows). (D) Paratype (ELEL-SJ081563), a juvenile, showing spokes (arrows) and remains of ctene rows. (E) Holotype (ELI-JSCT0001). (F) Close-up of apical organ in (E) showing internal aboral canal and statolith remains. (G) Close-up of focus area in (E) showing remains of ctenes. (H) Paratype (ELI-JSCT0002). (I) Close-up of apical organ in (H). (J) Paratype (ELEL-SJ101932A) showing apical organ, body with spinose spokes, and oral region. (K) Close-up of oral region in (J) showing lappet-like structures. (L) Close-up of a spine (arrowed in J). (M) Close-up of aboral part in (J) showing apical plates, statolith, and radiating spokes (arrowheads). (N) Close-up of focus area in (M) showing a spine sheathed by membrane (arrows). ac, aboral canal; ao, apical organ; cr, ctene row; lp, lappet; or, oral region; os, oral skirt; pl, apical plates; sl, statolith. Arrowheads in (E), (G), and (H) indicate medial ridges of radiating lobes mantled by membranous fins. Scale bars, 5 mm (A to E, H, J, and M); 1 mm (F, G, I, K, L, and N).

  • Fig. 3

    Idealized three-dimensional models of Cambrian skeletonized ctenophores. (A to C) Side views of Gemmactena actinala gen. et sp. nov, Batofasciculus ramificans, and Thaumactena ensis gen. et sp. nov., respectively. (A′ to C′) Oblique aboral views corresponding to (A) to (C).

  • Fig. 4

    Phylogenetic relationship of fossil and extant ctenophores based on a comprehensive cladistic analysis (tables S2 and S3). The skeletonized ctenophores from the Chengjiang biota form a clade here described as the new class Scleroctenophora. The cladogram is a strict consensus of the three most parsimonious trees. Apomorphies (character number and state above and below nodes, respectively) are mapped on the cladogram. Tree length = 53; consistency index = 0.9231; retention index = 0.9394; rescaled consistency index = 0.8671. Illustrated taxa are marked in bold.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/1/6/e1500092/DC1

    Systematic Paleontology

    Taphonomy and Preservation

    Cladistic Analysis

    Table S1. Preservation of ctenophore specimens from the early Cambrian Chengjiang biota.

    Table S2. List of characters and coding comments on ctenophore features used in cladistic analysis.

    Table S3. Data matrix used in cladistic analysis of ctenophores.

    Fig. S1. BSE and EDS analyses of Gemmactena actinala gen. et sp. nov.

    Fig. S2. Additional material of Thaumactena ensis gen. et sp. nov.

    Fig. S3. Additional material of Galeactena hemispherica gen. et sp. nov. and type specimen of Maotianoascus octonarius Chen et Zhou, 1997.

    Fig. S4. BSE and EDS analyses of Batofasciculus ramificans Hou et al., 1999.

    Fig. S5. Additional material of Batofasciculus ramificans Hou et al., 1999.

    Fig. S6. New material of Batofasciculus ramificans Hou et al., 1999.

    Fig. S7. New material of Trigoides aclis Luo et Hu, 1999.

    Fig. S8. New material of Trigoides aclis Luo et Hu, 1999.

    Fig. S9. A diminutive, unnamed ctenophore from the Chengjiang Biota.

    References (3457)

  • Supplementary Materials

    This PDF file includes:

    • Systematic Paleontology
    • Taphonomy and Preservation
    • Cladistic Analysis
    • Table S1. Preservation of ctenophore specimens from the early Cambrian Chengjiang biota.
    • Table S2. List of characters and coding comments on ctenophore features used in cladistic analysis.
    • Table S3. Data matrix used in cladistic analysis of ctenophores.
    • Fig. S1. BSE and EDS analyses of Gemmactena actinala gen. et sp. nov.
    • Fig. S2. Additional material of Thaumactena ensis gen. et sp. nov.
    • Fig. S3. Additional material of Galeactena hemispherica gen. et sp. nov. and type specimen of Maotianoascus octonarius Chen et Zhou, 1997.
    • Fig. S4. BSE and EDS analyses of Batofasciculus ramificans Hou et al., 1999.
    • Fig. S5. Additional material of Batofasciculus ramificans Hou et al., 1999.
    • Fig. S6. New material of Batofasciculus ramificans Hou et al., 1999.
    • Fig. S7. New material of Trigoides aclis Luo et Hu, 1999.
    • Fig. S8. New material of Trigoides aclis Luo et Hu, 1999.
    • Fig. S9. A diminutive, unnamed ctenophore from the Chengjiang Biota.
    • References (34–57)

    Download PDF

    Files in this Data Supplement:

Navigate This Article