PMC

Polyplacophora1–3: 1Polyplacophora sp. 1, dorsal view, scale bar 0.5 mm 2Polyplacophora sp. 2, dorsal view, scale bar 1 mm 3Ischnochiton sp., dorsal view, scale bar 0.5 mm. Bivalvia4–15: 4Arcidae sp., dorsal view, scale bar 0.5 mm 5Arcaimbricata5a ventral view 5b dorsal view, scale bar 1 mm 6Barbatiadomingensis6a ventral view 6b dorsal view, scale bar 1 mm 7Barbatia sp. 7a ventral view 7b dorsal view, scale bar 1 mm 8Bentharca sp. 8a ventral view 8b dorsal view, scale bar 1 mm 9Anomia sp. 9a ventral view 9b dorsal view, scale bar 1 mm 10Carditopsissmithii10a ventral view 10b dorsal view, scale bar 1 mm, 11Lucinidae sp., ventral view, scale bar 0.5 mm 12Chamasinuosa12a ventral view 12b dorsal view, scale bar 0.5 mm 13Chamidae sp. 13a ventral view 13b dorsal view, scale bar 1 mm, 14Crassinellalunulata14a ventral view 14b dorsal view, scale bar 1 mm 15Semelebellastriata15a dorsal view 15b lateral view, scale bar 1 mm. Gastropoda16–23: 16Gastropoda sp., ventral view, scale bar 0.5 mm, 17Diodoraminuta, ventral view, scale bar 0.25, 18Diodoralisteri18a ventral view 18b dorsal view, scale bar 1 mm, 19Scissurellaredferni19a ventral view 19b dorsal view, scale bar 1 mm 20Synaptocohleapicta20a ventral view 20b dorsal view, scale bar 1 mm 21Lodderenaornata21a ventral view 21b Apical view, scale bar 0.5 mm 22Cerithium sp. 1 22a ventral view 22b dorsal view, 1 scale bar 1 mm 23Cerithium sp. 2 23a ventral view 23b dorsal view, scale bar 1 mm.

Gastropoda1–26: 1Cerithiumatratum1a ventral view 1b dorsal view, scale bar 1 mm 2Alabaincerta2a ventral view 2b dorsal view, scale bar 0.25 mm 3Finella sp. 3a ventral view 3b dorsal view, scale bar 1 mm 4Sansoniatuberculata4a ventral view 4b dorsal view, scale bar 1 mm 5Hipponix sp. 5a ventral view 5b dorsal view, scale bar 0.1 mm 6Iniforisturristhomae6a ventral view 6b dorsal view, scale bar 1 mm 7Metaxiarugulosa7a ventral view 7b dorsal view, scale bar 0.5 mm 8Cerithiopsis sp. 8a ventral view 8b dorsal view, scale bar 1 mm 9Cerithiopsiscf.iuxtafuniculata9a ventral view 9b dorsal view, scale bar 1 mm 10Vermetidaeincertae sedis irregularis scale bar 1 mm 11Dendropomacorrodens scale bar 1 mm 12 Vermetid sp. C, ventral view, scale bar 0.25 mm 13Petaloconchusmcgintyi, ventral view, scale bar 0.25 mm 14Thylacodes sp. scale bar 1 mm 15Simulamerelinacaribaea15a ventral view 15b dorsal view, scale bar 1 mm 16Schwartziellafischeri16a ventral view 16b dorsal view, scale bar 1 mm 17Zebina sp. 2 17a ventral view 17b dorsal view, scale bar 1 mm 18Zebina sp. 2 18a ventral view 18b dorsal view, scale bar 0.5 mm 19Truncatella sp. 19a ventral view 19b dorsal view, scale bar 0.5 mm 20Caecumcircumvolutum, lateral view, scale bar 0.2 mm 21Caecumdonmoorei21a stage 1, lateral view, scale bar 0.2 mm 21b adult, lateral view, scale bar 0.2 mm 22Caecumjohnsoni, lateral view, scale bar 0.2 mm 23Caecumpulchellum, lateral view, scale bar 0.2 mm 24Caecumtextile, lateral view, scale bar 0.2 mm 25Caecum sp. B, lateral view, scale bar 0.2 mm 26Meiocerasnitidum, lateral view, scale bar 0.2 mm.

Gastropoda1–18: 1Parviturboides sp. 1a ventral view 1b dorsal view, scale bar 1 mm 2Vitrinella sp. 2a ventral view 2b dorsal view, scale bar 0.5 mm 3Gibberulalavalleeana3a ventral view 3b dorsal view, scale bar 1 mm 4Volvarina sp. 1 4a ventral view 4b dorsal view, scale bar 1 mm 5Volvarina sp. 2 5a ventral view 5b dorsal view, scale bar 1 mm 6Columbellidae sp. 1 6a ventral view 6b dorsal view, scale bar 0.5 mm 7Columbellidae sp. 2 7a ventral view 7b dorsal view, scale bar 0.5 mm 8Steironepionmoniferum8a ventral view 8b dorsal view, scale bar 1 mm 9Phrontis sp. 9a ventral view 9b dorsal view, scale bar 0.5 mm 10Trachypollia sp. 10a ventral view 10b dorsal view, scale bar 1 mm 11Turridae sp. 1 11a ventral view 11b dorsal view, scale bar 1 mm 12Ammoniceralineofuscata, Apical view, scale bar 0.25 mm 13Ammoniceraminortalis13a Apical view 13b ventral view, scale bar 0.1 mm 14Rissoellagalba14a ventral view 14b dorsal view, scale bar 0.1 mm 15Pseudoscillaaff.babylonia15a ventral view 15b dorsal view, scale bar 1 mm.

(A) Ventral scales in ventral view. (B) Virtual axial section of the ventral scutes at the level indicated by the white dotted line in (A). (C) Ventral scutes in anterior view. (D) Ventral scales in dorsal view. (E) A series of ventral scutes in posterior view. (F) The first right ventral scute in posterior view. (G) Virtual axial section of the scale in (F). (H–I) Anterior ventral scutes in (H) first and (I) second rows in ventral views. (J–K) Reconstruction and interpretative reconstructions of the posterior ventral scutes in the fourth and fifth rows in ventral view, respectively. (L) Virtual sagittal section of the additional scale and its surrounding scales. (M) Schematic diagram of the articulated way between ventral scutes in the front and back rows. (N) Ventrolateral scale and its surrounding flank scales. The black and red arrows indicate the anterior and dorsal directions, respectively. Scale bar equal to 2 mm.