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Fig. 14 in New insights into the origin and relationships of blastoid echinoderms

Fig. 14. Subterminal branching in the ambulacra of the callocystitid Callocystites fresti Paul, 2015a (SM A.85652), Wenlock (Silurian), Indiana, USA. Open arrow points to the place where the next lateral branch of the radial water vessel would have taken place, but the tip of the radial water vessel was at the top of the brachiole (Br) that arose from the final facet (solid arrow). Thus, branching of the radial water vessel in brachiole-bearing echinoderms was always subterminal. Modified from Paul and Hotchkiss 2020: fig. 7.

Fig. 10 in New insights into the origin and relationships of blastoid echinoderms

Fig. 10. Standard thecal plate diagram for the hemicosmitoid Hemicosmites spp. The theca consists of four circlets, basals (B, BB), infra-laterals (ILL), laterals (LL), and radials (RR). In Hemicosmites spp. there are four BB, six ILL, nine LL and nine RR. Hemicosmites spp. have only three erect ambulacra (A, shared BC, and shared DE) on facets developed on plates R4:R5, R7:R8, and R1:R2, respectively. P, periproct (surrounding anus). Compare with Figs. 6G2 and 9. For plate homologies see Table 2. Redrawn and relabelled from Bockelie 1979: 371, fig. 4a.

Fig. 7 in New insights into the origin and relationships of blastoid echinoderms

Fig. 7. Structure of the erect ambulacra of the coronate Stephanocrinus angulatus Conrad, 1842, Wenlock (Silurian), New York, USA. Biserial brachioles (1–7) are numbered in order of formation and the first two plates (1a, 1b, and so on) are modified to form the main ambulacral trunk. Note that because this is an aboral view, brachiole 1 is anatomically left but on the right of the figure. Redrawn from Brett et al. 1983: 640, fig. 8.

Fig. 9 in New insights into the origin and relationships of blastoid echinoderms

Fig. 9. Thecal plating in the callocystitid Lepadocystis moorei (Meek, 1871), Late Ordovician, Ohio, USA, illustrating typical extraxial plate arrangement in callocystitid and glyptocystitoid rhombiferans. Plates are arranged in four circlets, basals (B, BB), infra-laterals (IL, ILL), laterals (L, LL), and radials (R, RR), plus the orals which are largely axial in origin (see Fig. 5). All glyptocystitoids have four BB, five ILL and LL, and originally six RR. In all callocystitids R5 is absent. In Lepadocystis L5 interrupts the radial circlet and the periproct (P) is surrounded by four plates, IL4, IL5, L4, and L5. Lepadocystis has five, short ambulacra (dashed outlines below letters A–E) on the thecal plates and five pectinirhombs (Rh) across plate sutures B2:IL2, R1:L2, R3:L3, R3:L4, and R6:L1. Currents entered slits in the first mentioned plate and exited from the other plate. For plate homologies see Table 2. Redrawn and relabelled from Kesling 1967: S207, fig. 106.2c.

Fig. 5 in New insights into the origin and relationships of blastoid echinoderms

Fig. 5. Plating in the oral area and in ambulacrum A of the glyptocystitoid Lepadocystis moorei (Meek, 1871), Late Ordovician, Ohio, USA, showing interpretation of ambulacral growth and plate homologies. A–E, Carpenter ( 1884, 1891) ambulacra. Brachiole facets (F) are numbered (A1–A9) in ambulacrum A in the order in which they formed during growth, which cannot be changed after initial development. Each brachiole facet is developed on a pair of floor plates, the adoral of which is shaded pale grey. These are the first brachiolar plates to form during growth and become modified as floor plates. O1–O5, first and 1–5, second oral plates sharing the very first brachiole facet in each ambulacrum. Thus, these are also first brachiolar plates modified as orals. The first facets in each ambulacrum branch to the left as viewed in the growth direction (away from the mouth), but the second (black, F) obey Lovén's Law as restated by Paul and Hotchkiss (2020), AR, BL, CR, DL, ER, where A–E represent Carpenter's ambulacra and L and R represent left and right of the ambulacrum. This is because the ambulacra exhibit the " BD different" pattern of primary brachioles in which ambulacra B and D have the first two brachioles on the left, whereas ambulacra A, C and E have only the first brachiole left. Six primary oral cover plates (dark grey) and the two additional orals, O6 and O7, are identified. O1 and O7 always share the gonopore (G) and hydropore (H) in glyptocystitoid rhombiferans. Redrawn from Paul and Hotchkiss 2020: fig. 6.1 and Kesling and Mintz 1961: fig. 1.

Fig. 6 in New insights into the origin and relationships of blastoid echinoderms

Fig. 6. Examples of pan-dichoporite blastozoans. A. The callocystitid Pseudocrinites bifasciatus Pearce, 1843 (BMNH 40189), Wenlock (Silurian), West Midlands, UK, showing the lenticular theca (above) with peripheral ambulacra, the rapidly tapering proximal stem and more cylindrical distal stem (below) terminating in a root structure. B. The rhombiferid Rhombifera sp. (MPZ 2020/590), Late Ordovician, Zaragoza, Spain, showing the stem attached to the theca, which includes the basal, infralateral and base of the lateral plates (above) and one extensive pectinirhomb. C, D. The fissiculate blastoid Codaster acutus McCoy, 1849, early Carboniferous, Yorkshire, UK. C. Oral view of SM E5400 showing the central mouth, five radiating ambulacra, pectinirhomb-like hydrospires, and circular anus (below). D. Polished lateral view of SM E5398 showing basal and radial plates, anus (A) and very thin hydrospire folds (H). E. One branched ambulacrum of the callocystitid Callocystites jewetti Hall, 1852 (ROM 991N), Wenlock (Silurian), Ontario, Canada, showing the ambulacral structure. The mouth is to the left. Brachiole facets (lower branch) are each on a smaller adoral and larger aboral floor plate. Biserial brachioles alternate along the ambulacrum (Br), so main ambulacral axis has double biserial floor plates. F. Stereo images of the coronate Cupulocorona rugosa Donovan and Paul, 1985 (NMW 2013.8G.65i), Late Ordovician, Carmarthen, Wales, showing theca shape and extensive coronal processes (arrow). Top of the small basal plate is displaced. The rest of the theca up to the tip of the coronal process is formed by the "radial" plates. Erect ambulacra arose within the valleys between the coronal processes. G. The hemicosmitoid Hemicosmites extraneus Eichwald, 1840 (GIT 398–898), Late Ordovician, Madise, Estonia. Lateral view (G1) showing, from below, basal, infralateral, lateral, and radial plate circlets. Cryptorhomb pores can be seen in the infralateral and lateral plates. Oral view (G2) showing three large facets for erect ambulacra.

Fig. 8 in New insights into the origin and relationships of blastoid echinoderms

Fig. 8. Structure of the ambulacra and brachioles in the callocystitid Pseudocrinites bifasciatus Pearce, 1843 (SM A.10192), Wenlock (Silurian), Dudley, UK. First plate (1st) in a brachiole lies directly above the adoral floor plates (grey). This suggests floor plates are the first pair of brachiolar plates modified to form the ambulacral axis. Second and subsequent brachiolar plates white. In callocystitids, floor plates are developed on the thecal surface. A. Side view showing the high profile of the ambulacral axis and rapidly tapering brachiole. B. Impressions of ambulacral floor plates on the thecal plates. Arrows point to the mouth. Redrawn and relabelled from Paul 1967a: 326, figs. 17, 18.

Fig. 4 in New insights into the origin and relationships of blastoid echinoderms

Fig. 4. Origin of Lovén's Law in echinoderms illustrated by the oral plating in edrioasteroid Walcottidiscus Bassler, 1935 (USNM 376690), early Cambrian, locality unknown. A–E, five ambulacra arranged in a 2-1-2 pattern so that three radiate from the mouth, shared DE, A, and shared BC. A1, BC1, and DE1 represent the first ambulacral plates in the three primary ambulacra. A2, BC2, and DE2 represent the second ambulacral plates. When the shared ambulacra bifurcated to give five there was no other position in which the new ambulacral plates could be added than in the acute angle between the dividing primary rays. Thus, the new plates were B2, C2, D2, and E2. Once all five ambulacra reached the stage of having two floor plates, the positions of the first plates obey Lovén's Law as restated by Paul and Hotchkiss (2020), i.e., AR, BL, CR, DL, ER, that is the plates labelled A1, BC1, BC2, DE1, and DE2. Redrawn and modified from Paul and Smith 1984: 454, fig. 7A.

Fig. 3 in New insights into the origin and relationships of blastoid echinoderms

Fig. 3. Subterminal branching of the radial water vessel in a Recent cidarid echinoid Eucidaris metularia (Lamarck, 1816). Black arrow indicates the point where the next branch of the radial water vessel would arise, whereas the tip of the radial water vessel emerges through the ocular pore. Thus, although ambulacral and interambulacral plates are added to the corona terminally, branches of the radial water vessel to the tube feet are subterminal. G, genital plate; GP, genital pore; IA, interambulacral plate; O, ocular plate; OP, ocular pore; RWV, radial water vessel (internal).

Fig. 2 in New insights into the origin and relationships of blastoid echinoderms

Fig. 2. Growth zone as seen in a brachiole of the early Cambrian blastozoan, Kinzercystis durhami Sprinkle, 1973, early Cambrian, Pennsylvania, USA. The brachiole consists of a central alternating pair of columns of floor (brachiolar) plates, with a single series of cover plates along each lateral margin. Plates are added at the distal tip according to the ocular plate rule. Ventral (A1), right lateral (A2), and dorsal (A3) views; cross section (A4). Arrow indicates growth direction. Redrawn and simplified from Sprinkle 1973: 16, fig. 5A.

Fig. 1 in New insights into the origin and relationships of blastoid echinoderms

Fig. 1. Growth zone of ambulacrum B in the irregular echinoid Echinocyamus bisexus Kier, 1968, Eocene, Georgia, USA. An echinoid growth zone consists of four columns of plates, two central ambulacral columns the plates of which alternate, flanked by single columns of interambulacral plates (light grey shading). All the plates of a growth zone are added adjacent to the ocular plate at the aboral tip of each ambulacrum (on the opposite surface of the echinoid). The first two ambulacral plates to form during growth, the basicoronal plates adjacent to the mouth (M), express Lovén's Law. A, B, C, D, E, Carpenter's (1884, 1891) ambulacra; An, anus; H, hydropore (madreporite) on the opposite surface of the echinoid; L, left; R, right, designate ambulacral columns; M, mouth. Modified from Paul and Hotchkiss 2020: fig. 3.

Fig. 3 in A revaluation of rhipidocystid echinoderms based on a new flattened blastozoan from the Upper Ordovician of Maryland, USA

Fig. 3. Rhipidocystid echinoderm Durhamicystis americana gen. et sp. nov. from the Upper Ordovician Chambersburg Formation, Maryland, USA. A. USNM 642510. B. USNM 642511a, b. Photographs of specimens submerged in water to increase contrast of plates and plate boundaries (A1, B1). Camera lucida drawings indicating plate arrangements (A2, B2). Abbreviations: FP, flooring plate (green); G, gonopore; H, hydropore; M1–M9, marginal plates (yellow); O1–O7, oral plates (red); Pe, periproct. Central plates colored in blue, stem in purple, and brachioles in brown.

Fig. 6 in A revaluation of rhipidocystid echinoderms based on a new flattened blastozoan from the Upper Ordovician of Maryland, USA

Fig. 6. Comparisson between the rhipidocystids Mandalacystis dockery Lewis, Sprinkle, Bailey, Moffit, and Parsley, 1987 (A), Petalocystites ikecanensis (Sprinkle, 1973) (B), Neorhipidocystis norvegica (Bockelie, 1981) (C), and Durhamicystis americana gen. et sp. nov. (D). Abbreviations: FP, flooring plate (green); M1–M9, marginal plates (yellow); O1–O7, oral plates (red); central plates (blue); stem (purple), brachioles (brown); Pe, periproct. Based on Lewis et al. 1987 (A), Sprinkle 1973 (B), and Bockelie 1981 (C).

Fig. 1 in A revaluation of rhipidocystid echinoderms based on a new flattened blastozoan from the Upper Ordovician of Maryland, USA

Fig. 1. Rhipidocystid echinoderm Durhamicystis americana gen. et sp. nov. from the Upper Ordovician Chambersburg Formation, Maryland, USA. A. Holotype USNM 642510 showing the theca, proximal stem, and brachioles; general view of the complete specimen in ventral view (A1), detail of oral area and proximal part of the brachioles (A2), specimen in lateral view showing the periproct surrounded by three plates (A3). B. Paratype USNM 642513; general view of the complete specimen in ventral view (B1), note central plates in thecal interior, and single columnal attached to basals; detail of the anal pyramid on left edge (B2). Specimens whitened with ammonium chloride sublimate.

Fig. 4 in A revaluation of rhipidocystid echinoderms based on a new flattened blastozoan from the Upper Ordovician of Maryland, USA

Fig. 4. Rhipidocystid echinoderm Neorhipidocystis norvegica (Bockelie, 1981) from the Late Ordovician of the Oslo Region, Norway. A. PMO 101.143, half complete specimen; detail of the oral area (A2). B. PMO 101.144 (holotype), almost complete specimen lacking the lower portion; detail of the oral area (B2), note V-shaped notches and cover plates on uniserial brachioles. Specimens are latex casts whitened with ammonium chloride sublimate. Scale bars 5 mm.

Fig. 5 in A revaluation of rhipidocystid echinoderms based on a new flattened blastozoan from the Upper Ordovician of Maryland, USA

Fig. 5. Camera lucida drawings and plate interpretations of the oral area in Neorhipidocystis norvegica (Bockelie, 1981). A. PMO 101.143. B. PMO 101.144, holotype. Abbreviations: CP, cover plates over ambulacra and brachioles; FP, flooring plates; G, gonopore; H, hydropore; M, marginal plates; O1–O6, oral plates.

Fig. 2 in A revaluation of rhipidocystid echinoderms based on a new flattened blastozoan from the Upper Ordovician of Maryland, USA

Fig. 2. Rhipidocystid echinoderm Durhamicystis americana gen. et sp. nov. from the Upper Ordovician Chambersburg Formation, Maryland, USA. A. Paratype USNM 642511a, b; general view showing two nearly complete superimposed specimens (A1); detail of the oral area, proximal brachioles attached to marginal, oral, and floor plates, and three apertures (periproct, hydropore slit, and tiny gonopore) (A2); specimen in left lateral view showing the thin central plates from both integuments (A3); specimen in right lateral view showing the position of the periproct (A4); detail of facets between brachiolar plates and cryptic vertical sutures indicated by arrows (A5); detail showing thin internal projections of weathered, U-shaped, marginal plates (A6). Specimens whitened with ammonium chloride sublimate.

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Fig. 4 in Two newly recorded echinoderms from the mesophotic zone in Korea

Fig. 4. Distribution of Parastichopus nigripunctatus (Augustin, 1908) based on the present and previous study.

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Fig. 3. Henricia irregularis Hayashi, 1940 in Two newly recorded echinoderms from the mesophotic zone in Korea

Fig. 3. Henricia irregularis Hayashi, 1940 in this study. (A) abactinal paxillae; (B) abactinal skeleton; (C) papulae (arrows); (D) madreporite; (E) actinal skeleton; (F), (I) adambulacral spines; (G) oral part and interradii of actinal side; (H) abactinal spines. Scale bars: A-E = 1 mm, F = 5 mm, G = 3 mm, H = 100 μm, I = 200 μm (H, I, SEM images). Abbreviations: a, adambulacral plates; i, inferomarginal plates; in, intermarginal plates; s, superomarginal plates; v, ventrolateral plates.