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Vannier et al. 2006 assume that Tuzoia and the also Cambrian genus Isoxys are possibly representatives of the class Thylacocephala. Emmended diagnosis for the genus Isoxys by Garcia-Bellido 2009, p. 1224: ”Arthropod with one pair of cephalic appendages and a uniform series of at least 13 pairs of biramous appendages. Long, narrow body covered almostentirely by a bivalved, very thin unmineralized carapace. Prominent, stalked, spherical to pear-shaped lateral eyes protrude beyond the anterior margin of the carapace. Each valve armed with prominent cardinal spines. Dorsal outline straight or slightly projecting to form a weak to well-developed cusp (small circular node may be present below this cusp) anterior of mid-length. Ventral outline semicircular, weakly preplete (valve is highest anterior to its mid-length) to postplete (highest posterior to its mid-length). Simple perimarginal features (very narrow to more inflated rim). No flattened ⁄ concave marginal features. Narrow to broad doublure may be present. Carapace folded along the dorsal line (valves conjoined by a narrow band of cuticle; absence of articulating hinge). Internally, midgut glands may be present. External ornament may be expressed as uniform micro-reticulation or longitudinal striae. (Modified from Vannier and Chen 2000, p. 311)." Hou et al. 2007, p. 118: “This is one of three Isoxys species recorded from the Chengjiang biota. It is relatively rare and, unlike its Chengjiang associates Isoxys auritus and Isoxys curvirostratus, is known only from carapaces. The thin, elongate, bivalved carapace has a straight spine at both the anterodorsal and posterodorsal corners. The posterior spine is longer than the bivalved part of the carapace. Including both spines, carapace length can exceed 100mm. I. paradoxus can easily be distinguished from I. auritus by the unequal and total length of its spines. I. curvirostratus is distinguished from other species of the genus by having a curved anterior spine (Vannier & Chen 2000). Isoxys is a component of the earliest arthropod faunas worldwide. The genus is known from the Lower Cambrian of Spain, Siberia, South Australia and Southwest China and also from the Lower to Middle Cambrian of Laurentian North America. The ecology of Isoxys is discussed under I. auritus. I. paradoxus is unknown outside the Chengjiang biota.” Line drawing from Garcia-Bellido et al., p. 1224: Identified by oilshale using Hou et al, 2007. References: Hou Xian-guang (1987c) Early Cambrian large bivalved arthropods from Chengjiang, eastern Yunnan. Ada Palaeontologica Sinica, 26, 286-298. [In Chinese, with English summary]. Williams, M., Siveter, D.J. and Peel, J. (1996) Isoxys (Arthropoda) from the early Cambrian Sirius Passet Lagerstatte, North Greenland. Journal of Paleontology, 70, 947-954. Chen Jun-yuan & Zhou Gui-qing. (1997) Biology of the Chengjiang fauna. Bulletin of the National Museum of Natural Science, 10,11-106 Hou Xian-guang, Bergstrom, J., Wang Hai-feng, Feng Xiang-hong & Chen Ai-lin. (1999) The Chengjiang Fauna. Exceptionally well-preserved animals from 530 million years ago. 170 pp. Yunnan Science and Technology Press, Kunming, Yunnan Province, China. [In Chinese, with English summary] Vannier, J. and Chen, J.Y. (2000) The Early Cambrian colonization of pelagic niches exemplified by Isoxys (arthropoda). Lethaia 33, 295–311. Vannier, J., Chen, J.-Y., Huang, D.-Y. and Wang, X.-Q. (2006). Thylacocephalan arthropods: Their early Cambrian origin and evolutionary significance. Acta Paleontologica Polonica, 51:201–214. Hou Xian-guang, Aldridge, R., Bergstrom, J., Siveter David J., Siveter Derek J. and Feng Xiang-Hong (2007) The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life, Wiley-Blackwell, ISBN 10: 1405106735. Garcia-Bellido, D.C., Paterson, J.R., Edgecombe, G.D., Jago, J.B., Gehling, J.G. and Lee, M.S.Y. (2009) The bivalved arthropods Isoxys and Tuzoia with soft-part preservation from the Lower Cambrian Emu Bay Shale Lagerstätte (Kangaroo Island, Australia). Palaeontology, 52: 1221-1241. https://doi.org/10.1111/j.1475-4983.2009.00914.x

Taxonomy according to Fossilworks.org. Quote from Zhang et al. 2003, p. 447:” The Chengjiang Lagerstätte yields several well-preserved Early Cambrian fossil assemblages (Zhang et al. 2001) from the Yu’anshan Member of the Qiongzhusi Formation in Yunnan Province, South China, consisting of a diverse suite of arthropods (Shu et al. 1995, 1999a; Hou and Bergström 1997; Zhang 1999; Zhang et al. 2000). One of them, small and relatively rare, was only briefly described based on a few specimens (Hou et al. 1991), and repeatedly considered to be a giant protaspis of a naraoiid by many authors (Fortey and Theron 1994; Chen et al. 1996; Hou and Bergström 1997; Hou et al. 1999; Luo et al.1999). Recently this animal was also recovered from the Middle Cambrian Kaili fauna of Guizhou Province, South China (Zhao et al. 1999). Diagnosis for Primicaris larvaformis according to Zhang et al. 2003, p. 450: “Small, protaspis-like arthropod; undivided dorsal shield with a pair of posterior spines and ten pairs of lateral marginal spines; on the ventral side, one pair of uniramous antennae followed by ten pairs of biramous limbs.” Camera lucida drawing of holotype (ELI12001012), from Zhang et al. 2003: Identified by oilshale using Zhang et al. 2003. References: Zhang, Xing-Liang; Han, Jian; Zhang, Zhi-Fei; Liu, Hu-Qin; Shu, De-Gan (2003): Reconsideration of the supposed naraoiid larva from the Early Cambrian Chengjiang Lagerstatte, South China. Palaeontology. 46 (3): 447–465. doi:10.1111/1475-4983.00307 Shu, De-Gan; Zhang, Xing-Liang and Geyer, G. (1995): Anatomy and systematic affinities of the Lower Cambrian bivalved arthropod Isoxys auritus. Alcheringa, 19, 333-342. Zhang, Xing-Liang; Shu, Degan; Li, Yong and Han, Jian (2001): New sites of Chengjiang fossils: crucial windows on the Cambrian explosion. Journal of the Geological Society, London, 158, 211-218. Shu, De-Gan; Vannier, J.; Luo, Hui-Lin; Chen, Lin; Zhang, Xing-Liang and Hu, Shi-Xue (1999a): Anatomy and life style of Kunmingella (Arthropoda, Bradoriida) from the Chengjiang fossil Lagerstätte (Lower Cambrian; southwest China). Lethaia, 32, 279-298. Hou, Xian-Guang and Bergström, J. (1997): Arthropods of the Lower Cambrian Chengjiang fauna, southwest China. Fossils and Strata, 45, 1-115. Zhang, Xing-Liang (1999): Cambrian explosion and some arthropods from the Early Cambrian Chengjiang Lagerstätte. Unpublished PhD thesis, Northwest University at Xian, China, 118 pp. [In Chinese, English summary]. Zhang, Xing-Liang; Han, Jian and Shu, Degan (2000): A new arthropod Pygmaclypeatus daziensis from the Early Cambrian Chengjiang Lagerstätte, South China. Journal of Paleontology, 74, 979-982. Hou, Xian-Guang; Ramsköld, L. and Bergström, J. (1991): Composition and preservation of the Chengjiang fauna - a Lower Cambrian soft-bodied biota. Zoologica Scripta, 20, 395-411. Fortey, R. A. and Theron, J. N. (1994): A new Ordovician arthropod, Soomaspis, and the agnostid problem. Palaeontology, 37, 841-861. Chen, Jun-Yuan; Edgecombe, G. G.; Zhu, Mao-Yan and Yeh Kui-Yu (1996): The Chengjiang biota - a unique window of the Cambrian explosion. The National Museum of Natural Science, Taichung, Taiwan, 222 pp. [In Chinese]. Hou, Xian-Guang; Bergström, J.; Wang, Hai-Feng, Feng, Xiang-Hong and Chen, Ai-Lin (1999): The Chengjiang fauna. Exceptionally well-preserved animals from 530 million years ago. Yunnan Science and Technology Press, Kunming, 170 pp. [In Chinese, English summary].

Leptomitus teretiusculus is a moderately common, thin-walled sponge species. Specimens range up to 11cm long and about 1,2cm wide. Literature: J. Y. Chen, X. G. Hou, and H. Z. Lu. 1989. Lower Cambrian leptomitids (Demospongea), Chengjiang, Yunnan. Acta Palaeontologica Sinica 28(1):17-30

From http://sciencythoughts.blogspot.com/2015/05/yuganotheca-elegans-early-cambrian.html: "An Early Cambrian Lophophorate Animal with affinities to Brachiopods and Phoronids. Lophophorates are animals which feed using a filter called a lophophore, which comprises a number of setae covered tentacles, to extract food from water. The group includes the shelled Brachiopods, the worm-like Phoronids, the minute Entoprocts, and colonial Bryozoans, and has been shown by molecular and embryonic evidence to be related to the Molluscs and Annelids. Within the Lophophorates the Phoronids and Brachiopods are thought to be closely related, with some studies suggesting that the Phoronids should be regarded as a shell-less subgroup of the Brachiopods." Zhang, Z.-F. et al. An early Cambrian agglutinated tubular lophophorate with brachiopod characters. Sci. Rep. 4, 4682; DOI:10.1038/srep04682 (2014).

Fuxianhuia protensa life restoration created and copyrighted by Nobu Tamura, licensed under the Creative Commons Attribution-Share Alike 4.0 International (Wikimedia Commons): References: Hou X.-G. (1987). Three new large arthropods from Lower Cambrian Chengjiang, eastern Yunnan. Acta Palaeontologica Sinica 26, 272–285. Bergström, J., Hou, X., Zhang, X., Liu, Y. & Clausen, S. (2008). A new view of the Cambrian arthropod Fuxianhuia. GFF, Vol. 130 (Pt. 4, December), pp. 189–201. Stockholm. ISSN 1103-5897.