Fig. 4: Camenellan juveniles from the Cambrian Salanygol Formation of Mongolia.
From: Exceptionally preserved early Cambrian bilaterian developmental stages from Mongolia
a Dorsal view of an early juvenile with six central ridges preserving cellular pattern. b Dorsal view of the juvenile stage with six arc-shaped central ridges and one differently shaped anterior spinose structure. c Dorsal view of a juvenile with six shallow central ridges and an anterior field with a different morphology. d Ventral view of juvenile stage illustrated in a; 12 distinct fields form a band-like array in this ontogenetic stage, which later develop into the peripheral zone; note the circular plate-like anterior nascent sclerite with a small projection is outside the ventral band of fields; a posterior nascent sclerite is not yet developed or detectable. e Lateral view of an individual shown in b with shallow central ridges and the anterior nascent sclerite visible as an erect broad spine, lateral nascent sclerites are still not yet well developed, forming small fields at the bases of central ridges. f Slightly distorted and incomplete early juvenile with well-preserved cellular pattern. g Lateral view of incomplete early juvenile illustrated in f, where lateral protuberances begin to develop as asymmetric cones. h Larger juvenile with central ridges beginning to develop more erect structures. i, j Half volumes at different dorsoventral cutting planes of syncCT-models of individual shown in h, note single epithelial cell layer in sectioning plane. k Half volume of syncCT-model of h with cutting plan in anterior–posterior direction, revealing similar cellular pattern on the ventral side as visible dorsally. C1–6 central nascent sclerite 1–6 of medial zone, P posterior nascent sclerite, A anterior nascent sclerite, ll1–6 left lateral sclerites 1–6 of peripheral zone, rl1–6 right lateral nascent sclerites 1–6 of peripheral zone. All images are secondary electron micrographs of an electron microscope, except for b, which is a backscatter electron micrograph and i–k, which are volume models of X-ray syncCT. Specimen identifiers: a, d Sal 133-040; b, e Sal 133-43, c Sal 139-012; g, f Sal 133-042; h–k Sal 133-044.
