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Figure 1. Universal elemental homology.Camera lucida drawing of the oral surface of the glyptocystitoid rhombiferan Lepadocystis moorei (Meek, 1871) [72] (CMCIP 57349) with plates colored according to Universal Elemental Homology. Red plates (O1–O7) are oral plates that form the border of the peristome. Blue plates (1–5) are primary peristomial cover plates (PPCP). Green plates are ambulacral floor plates (AFP), tan plates are ambulacral cover plates (ACP). A–E are the ambulacral designations based on the Carpenter [5] system. The mouth or peristome is located beneath PPCP1, 3, and 4. The gonopore and hydropore are gp and hp, respectively. S are shared cover plates of the shared ambulacra. (After [57]).
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Figure 2. Homologous oral-region plates in more-derived blastozoans.Colored and uncolored views for plate comparison; color key as in Figure 1; geologic ages in Table 1. A,B, D, E. the eocrinoid Rhopalocystis destombesi Ubaghs, 1963 [73], A, B, latex cast of paratype PMO A29122 with only orals and floor plates preserved, D, E, latex cast of paratype PMO A29124 with all oral surface plates preserved; C, F. the glyptocystitoid Quadrocystis graffhami Sprinkle, 1982 [74], holotype OU 8972; G, H. the diploporan Eumorphocystis multiporata Branson and Peck, 1940 [75], SUI 97598; I, L. the coronoid Stephanocrinus gemmiformis Conrad, 1842 [76], SUI 134869; J, K. the paracrinoid Columbocystis typica Bassler, 1950 [77], SUI 134870. Scale bars: 5 mm (A–L).
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Figure 3. Homologous oral-region plates in crinoids.Colored and uncolored views for plate comparison; color key as in Figure 1; geologic ages in Table 1. A, G. the plesiomorphic cladid Carabocrinus treadwelli Sinclair, 1945 [78], OU 9127, note the lack of floor plates where the ambulacral cover plates are missing on the B-ray, and the hydropore in Oral 1; B, C. the plesiomorphic cladid Nuxocrinus crassus Whiteaves, 1887 [79], plesiotype, USNM 305473, note the madreporite in Oral 1; D, J. the camerate Collicrinus yandelli Owen and Shumard, 1850 [80], plesiotype, USNM S1337, note the absence of orals and the fixed PPCP and ACP that form the tegmen, along with interambulacral plates; E, F. a juvenile of the camerate Elegantocrinus symmetricus Wachsmuth and Springer, 1897 [81], plesiotype, USNM S1310, note the absence of orals and the fixed PPCP and ACP that form the tegmen, along with interambulacral plates; H, I. the plesiomorphic hybocrinid Hybocrinus nitidus Sinclair, 1945 [78], OU 9179, note the tiny PPCP plates homologous with those in Figure 2C, D,G and Figure 3A,B, also note the coelomic canals through the radial plates at the arm bases; K, L. the cladid Illemocrinus amphiatus Eckert, 1987 [82], paratype, ROM 45102, note that there are two PPCP at each interradial position, also note the coelomic canals through the radial plates at the arm bases; M, N. the neotenic camerate Neoplatycrinus dilatatus Wanner, 1916 [83], SUI 134856, note that the tegmen is composed exclusively of the five PPCP plus a single ACP in each ray; O, P. the camerate Marsupiocrinus stellatus (Troost in Wood, 1909 [84]), plesiotype, USNM S1296, note the absence of orals and the fixed PPCP and ACP that form the tegmen, along with interambulacral plates, distal ambulacra with moveable cover plates; Q, R. the camerate Cyttarocrinus jewetti Goldring, 1923 [85], BMS E21032, which is plesiomorphic in having visible orals, note that the PPCP and ACP are not preserved having fallen away as based on other specimens, but the orals have small prong-like extensions over the peristome. Scale bars: 5 mm (A–R).
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Figure 4. Homologous oral-region plates in edrioasteroids and less-derived blastozoans.Colored and uncolored views for plate comparison; color key as in Figure 1, except that purple plates are oral frame plates; geologic ages in Table 1. A, E,B, F. the plesiomorphic edrioasteroid Kailidiscus chinensis Zhao et al., 2010 [48], latex casts of paratype GM 2103, note the integrated interradial (IIP) plates, in red, judged to be oral plate homologues, A, E, exterior view, B,F, interior view; C, D. the gogiid blastozoan Sinoeocrinus lui Zhao et al., 1994 [86], latex cast of GTBM 95265, oral view with the radially positioned oral frame plates that give rise to brachioles; G, H, I, J. the edrioasterid edrioasteroid Edriophus levis Bather, 1914 [87], G, H, exterior view, note the oral plates, in red, CMCIP 40480, I, J, interior view, CMCIP 40478, note the orals in red and oral frame plates in purple form the peristomial border; K, L. the isorophid edrioasteroid Anedriophus moroccoensis Sumrall and Zamora, 2011 [53], FSTG/AA-BCBb-OI-25, interior view showing the radially positioned oral frame plates; M, N. the imbricate blastozoan Lepidocystis cf. L. wanneri Foerste, 1938 [88], latex cast of MCZ 628, interior view with the radially positioned oral frame plates that lead to floor plates. Scale bars: 5 mm (A, B, C, D, E–K, M, N), 2.5 mm (K, L).
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Figure 5. Examples of peristomial border systems (PBS) with cover plates removed to expose the mouth frame.A. PBS A1, interior view of Kailidiscus showing the mouth frame constructed by integrated interradial plates (IIP), or orals, and unfused biserial floor plates, black areas are the elongated peristome in the center and podial pores between plates, modified from [48]; B. PBS A2, the diploporan Protocrinites
[4], note that orals 2 and 5 do not contact the peristome (black); C. PBS A3, the crinoid Palaeocrinus, note the oval peristome that had shared peristomial cover plates, modified from [89]; D. PBS A4, the coronoid Stephanocrinus, note the round peristome that was covered by only five primary peristomial cover plates, modified from [90]; E. PBS B1, the edrioasterid Edriophus with both oral plates (O1–O6) and oral frame plates (A–E), an interpretation based on Figures 4G, I; F. PBS B2, interior view of the isorophid Hypsiclavus showing oral frame plates (A–E) in line with uniserial floor plates, modified from [51].
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Figure 6. Homologous oral-region plates in the Middle Ordovician edrioblastoid Astrocystites.Colored and uncolored views for plate comparison; color key as in Figure 1. A, D. the edrioblastoid Astrocystites ottawaensis Whiteaves, 1897 [91], GSC 752, note the small orals encompassed within the larger “deltoid” plates formed by fused floor plates, and the suturing of the proximal ACP to the PPCP; B, C, E, F. isolated “deltoid” plates of Astrocystites sp. consisting of a small oral and floor plates fused together, B, E, oral view with peristome down, SUI 134871; C, F, lateral view with peristome upper left, SUI 134872. Scale bars: 5 mm (A, D), 2.5 mm (B, C, E, F).
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