Geological features of the Montagne Noire.

<p>A, Location of the Massif Central and the Montagne Noire in France. B, Structural sketch of the Montagne Noire, after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Devaere1" target="_blank">[41]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Demange1" target="_blank">[46]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Clausen1" target="_blank">[49]</a>. C, Geological sketch of the Avène-Mendic parautochthon with location of the sections yielding hyolith with three-dimensionally preserved digestive tracts, after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Devaere1" target="_blank">[41]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-lvaro1" target="_blank">[48]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Clausen1" target="_blank">[49]</a>. D- Litho- and chronostratigraphic setting of the Avène-Mendic parautochthon, after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Devaere1" target="_blank">[41]</a>.</p

Hyolith digestive tracts.

<p>A, Hyolithid specimen with three-dimensionally preserved digestive tract from Cambrian Stage 4 of northern Canada, reprinted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Butterfield2" target="_blank">[30]</a> under a CC BY license, with permission from Oxford University Press, original copyright 2003, and reconstruction of the simple U-shaped hyolithid digestive system. B, Specimen of the orthothecid <i>Girvanolithes thraivensis </i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-CowperReed1" target="_blank">[75]</a> with three-dimensionally preserved digestive tract from the upper Ashgill of the Girvan district, Scotland, reprinted from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Malinky3" target="_blank">[33]</a> under a CC BY license, with permission from Paleontological Society original copyright 2003, and reconstruction of the partially folded U-shaped orthothecid digestive system.</p

Hyolith terminology.

<p>A, Reconstruction of the hyolithid conch <i>Joachimilites novaki </i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Marek5" target="_blank">[23]</a> with proturding helens and <i>in situ</i> operculum. External (left) and internal (right) surfaces of operculum are detailed. l: ligula; h: helens; CaS: cardinal shield; r: rooflet; CoS: conical shield; cp: cardinal process; cl: clavicle; modified after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Malinky1" target="_blank">[8]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Malinky4" target="_blank">[56]</a>. B, Reconstruction of the orthothecid conch <i>Nephrotheca housina </i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Marek5" target="_blank">[23]</a> with <i>in situ</i> operculum and detail of external (left) and internal (right) surfaces of operculum. p: process; lc: clavicle-like structure; modified after <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Marek5" target="_blank">[23]</a>.</p

Digestive tract type versus average apertural diameter (µm) based on 27 specimens of <i>C. subcurvata</i>.

<p>Correlation coefficient: r  =  0,62, coefficient of determination: r²  =  0,38 and <i>p</i>-value  =  0,00057.</p

Illustration of hypothetised heterochronic processes of intestine evolution in hyoliths.

<p>a-c, based on the new data from the digestive tracts of <i>C. subcurvata</i>; d, from digestive tracts of <i>Guduguwan</i> from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Kruse1" target="_blank">[9]</a>; e, <i>Orthotheca</i> from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Thoral1" target="_blank">[31]</a>; f, <i>Haplophrentis</i> from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Babcock1" target="_blank">[29]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Butterfield2" target="_blank">[30]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Mao1" target="_blank">[35]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088583#pone.0088583-Butterfield3" target="_blank">[36]</a>.</p

<i>Conotheca subcurvata</i>[38].

<p>A, USTL2782/11; Lateral view showing incompletely preserved guts and external coating of withdrawn operculum. B, USTL2782/3; Lateral view of specimen with different microbial pseudomorphs in the internal and external compartments and overgrowth. C-D, USTL2782/2; C, Lateral view, squared area magnified in D; D, Detail of the preservation of the digestive tract and filamentary junction with mould (arrow), the filaments seem to cover or invade the pre-existing mould. E-F, USTL2788/7; E, Lateral view, squared area magnified in F; F. Detail of Large coccoids covering the intestine cast and preserved withdrawn operculum. G, USTL2788/8; Lateral view of conch, exogenous material (tube) in the exterior compartment arrowed. H, USTL2784/2; Detail of exogenous material (halkierid) within the conch. I-K, USTL2781/6; I, Lateral view, squared area magnified in K; J, Possible fungal hyphae (arrowed) in connection with intestine, in this case communication with exterior compartment; K, Detail of possible hyphae. L-M, USTL2789/2; L, Lateral view, squared area magnified in M; M, Intestine phosphatic meshwork denser than exterior compartment. N, USTL2789/3; Detail of relations between exterior and interior compartments and operculum. O-P, USTL2781/9; O, Lateral view, squared area magnified in P; P, Detail of diagenetic overgrowth of the intestine phosphatic cast. Scale bars are: P, 50 µm; F, H, K, N, 100 µm; D, J, M, 200 µm; A-C, E, G, I, L, O, 500 µm.</p

Chapter 13 Cambrian echinoderm diversity and palaeobiogeography

<p>The distribution of all known Cambrian echinoderm taxa, encompassing both articulated specimens and taxonomically diagnostic isolated ossicles, is documented for the first time. The database described by 2011 comprises 188 species recorded from 65 formations from around the world. Formations that have yielded articulated echinoderms are unequally distributed in space and time. Only Laurentia and West Gondwana provide reasonably complete records at the resolution of Stage. The review of the biogeographical distributions of the eight major echinoderm clades shows that faunas from Laurentia and Northeast Gondwana (China and Korea) are distinct from those of West Gondwana and Southeast Gondwana (Australia); other regions are too poorly sampled to make firm palaeobiogeographical statements. Analysis of alpha diversity (species per formation) shows that diversity rose initially to Cambrian Stage 5, declined into Guzhangian and Paibian before returning to Stage 5 levels by the end of the Cambrian. This pattern is replicated in Laurentia and West Gondwana. We show that taxonomically diagnostic ossicles found in isolation typically occur significantly earlier than the first articulated specimens of the same taxa and provide important information on the first occurrence and palaeobiogeographical distribution of key taxa, and of the phylum as a whole. </p