FIGURE 1. Adult specimens of Cambrobranchus pelagobenthos from the Haiyan Lagerstätte of China. A, Part of the holotype, YKLP14443. B, X-ray tomographic image of YKLP14443. C, Interpretative drawing of the anterior part of A. D, A well-preserved individual attached to an uncertain sclerite, YKLP14529. E, Fluorescent microscopy image of the white dashed area in C. F, Interpretative drawing of C. Scale bars, 2 mm (A–C, G), 1 mm (D–F). CO, collar; EBR, epibranchial ridge; GB+TB, gill and tongue bars; GP, gill pore; KHS, kidney–heart–stomochord complex; M, mouth; NS, nuchal skeleton; P, proboscis; PR, parabranchial ridges; T, trunk.
FIGURE 2. Adult specimens of Cambrobranchus pelagobenthos from the Haiyan Lagerstätte of China. A, U-shaped individual with preserved post-anal organ, YKLP14530. B, Interpretative drawing of A. C, Nearly complete curved specimen, co-occurring with some incomplete specimens, YKLP14531. D, Interpretative drawing of C. Scale bars, 1 mm. A, anus; CO, collar; EBR, epibranchial ridge; GB+TB, gill and tongue bars; In, intestine; KHS, kidney–heart–stomochord complex; P, proboscis; PAO, post-anal organ; PR, parabranchial ridges; T, trunk.
FIGURE 3. Larvae and juvenile specimens of Cambrobranchus pelagobenthos from the Haiyan Lagerstätte of China, and comparison to extant hemichordate and echinoderm larvae. A, Post-hatched early stage tornaria larva, YKLP 14532. B, Interpretive drawing of A. C, Early to middle stage larva, YKLP14540. D, Interpretive drawing of C. E, Juvenile specimen, YKLP14533. F, Juvenile specimen, YKLP14536. G, Juvenile specimen, YKLP14548. H, Juvenile specimen with at least two pairs of preserved oval-shaped gill pores, YKLP14549. I, Interpretive drawing of E. J, Interpretive drawing of F. K, Interpretive drawing of G. L, Interpretive drawing of H. M, Juvenile specimen, YKLP14551. N, SEM micrograph of an extant tornaria larva of Schizocardium sp. from the coast of Texas. O, SEM micrograph of an extant early stage juvenile of Schizocardium sp. from the coast of Texas. P-S, Interpretive drawings of the developing stages of an indirect developing modern enteropneust (modified from Gonzalez et al., 2017). P, Early stage tornaria larva. Q, Middle stage tornaria larva. R, Late stage tornaria larva. S, Post metamorphic juvenile. T, Interpretive drawing of an echinoderm (Holothuroidea) larva (modified from Dyachuk and Odintsova, 2013). Scale bars, 500 μm (A–L, N, O), 1 mm (M). AO, apical organ. CB, ciliary band; CO, collar; D, digestive tract; ES, esophagus; GP, gill pore; In, intestine; KHS, kidney–heart–stomochord complex; M, mouth; P, proboscis; PAO, post-anal organ; PFB, perioral feeding band; PT, post telotroch; T, trunk.; TL, telotroch.
FIGURE 4. SEM and SEM-EDX analyses of Cambrobranchus pelagobenthos from the Haiyan Lagerstätte of China. A-H, Soft-bodied tissue preservation of YKLP14532. A, A SEM micrograph showing the larva. B-H, Individual elemental maps. B, Iron. C, Sulfur. D, Carbon. E, Oxygen. F, Aluminum. G, Silicon. H, Potassium. I-P, Soft-bodied tissue preservation of YKLP14540. I, A SEM micrograph showing the larva. J-P, Individual elemental maps. J, Iron. K, Sulfur. L, Carbon. M, Oxygen. N, Aluminum. O, Silicon. P, Potassium. Scale bars equal 200 μm.
FIGURE 5. Reconstruction of Cambrobranchus pelagobenthos from the Haiyan Lagerstätte of China: Artistic reconstruction of larvae, juveniles, and an adult specimen by C. McCall.
FIGURE 6. Inferred phylogenetic relationships: Phylogenetic position of Cambrobranchus pelagobenthos and other Cambrian ambulacrarians using majority-rules Bayesian analysis of 113 characters and 27 taxa. Numbers at nodes represent posterior probabilities. Pie charts indicate the results of an ancestral state reconstruction.
