Liu et al.—Upper Cambrian cycloneuralians from South China


only by postembryonic stages whereas Markuelia is only known as embryonic stages. On the other hand, because palaeoscolecids and Markuelia are the only preserved cycloneuralians at the key horizon ofWangcun section (Fig. 1), there is an intriguing possi- bility that Markuelia might represent the embryonic stage of palaeoscolecids. This possibility assumes that there were no other cycloneuralians that cohabitated with Markuelia and palaeo- scolecids, or they left no fossil records. This proposition can be confirmed only if the morphological gap between Markuelia and palaeoscolecids is filled with transitional forms to establish an ontogenetic linkage between the two taxa. Additional and more complete fossils are needed to test this hypothesis, and particularly useful and critical fossils are those with proboscis preservation, which would provide key insights into the possible ontogenetic relationship between palaeoscolecids and Markuelia. The new fossils also provide new information about


the upper size limit of Orsten-type fossils. Traditionally, Orsten- type preservation is thought to favor microscopic arthropods, generally between 100 μm and 2mm, and larger organisms are only preserved as fragments<2mm (Maas et al., 2006). How- ever, it seems that specimens larger than 2mm, either as com- plete individuals or as fragments, are not uncommon among cycloneuralians in Orsten-type Lagerstätten. For example, one of the paratypes of Eokinorhynchus rarus from the early Cambrian Xinli Member, Dengying Formation in northern Sichuan Province, South China (Zhang et al., 2015, fig. 2) has a length of 2.08mm. Among the palaeoscolecid fossils descri- bed here, NIGP160453 (Fig. 4.1) has a length of 2.24mm, NIGP160495 (Fig. 8.1) has a length of 2.8mm, and NIGP160456 (Fig. 7.2) has a length of 3.12mm. Still larger specimens have been recovered recently from Orsten-type Lagerstätten. For example, a new fragment of cycloneuralian about 3.8mm in length has been recovered from the early Cambrian Kuanchuanpu Formation in southern Shaanxi Province, South China (personal observation, Y.H. Liu, 2017). This new worm is folded; if unfolded it would have a length of about 6mm. More important, this new worm is represented by fragmented preservation, and the complete organism is estimated to have exceeded one centimeter in length. These new fossils raise a very important question: whether there is a taxonomic control on the size bias of Orsten-type preservation. In other words, is it possible that, unlike arthropod fossils, which are typically <2mm in size, larger cycloneuralians can be preserved in Orsten-type Lagerstätten? The underlying mechanism of such a preservational and taxonomic bias is difficult to interpret, but the discovery of large cycloneuralian fragments shows that: (1) specimens larger than 2mm can indeed be preserved in Orsten-type preservation, and (2) some of the Cambrian meiofaunal animals (<1mm) can finally reach several millimeters or even a centimeter in size.


Conclusions


Wedescribed new material of three-dimensionally phosphatized and microscopic cycloneuralians from the Furongian (tradi- tional upper Cambrian) Bitiao Formation, Wangcun Lagerstätte, western Hunan, South China. The new material includes fossil embryos Markuelia sp., two other types of fossil embryos that might be correlated with Markuelia, and three species of


97


palaeoscolecids including Dispinoscolex decorus Duan et al., 2012, Schistoscolex hunanensis Duan et al., 2012, and Austroscolex sinensis n. sp. The microscopic palaeoscolecids together with Eopriapulites, Eokinorhynchus, and Markuelia represent the microscopic cycloneuralians from the Cambrian oceans of South China. It is proposed here that the cycloneur- alians and ecdysozoans should have originated in the Cambrian Fortunian small shelly faunas, or even earlier, and Eopriapulites might be a candidate ancestral type of cycloneuralian. The last common ancestor of Cycloneuralia might be microscopic and similar to Eopriapulites, with internally hollow scalids.


Acknowledgments


This work was supported by the Chinese Ministry of Science and Technology 973 Project (2013CB837100), the National Natural Science Foundation of China (41572007, 41572009), the Youth Innovation Promotion Association, Chinese Academy of Sciences (2016283), College Students’ EntrepreneurialTraining Program (201610710043, 201610710044, 201610710045, 201610710047), and the Tenth “Challenge Cup” Competition of Chang’an University (C-P-B-2, C-P-B-6, C-P-B-8). Correspondence should be addressed to HZ (hqzhang@nigpas.ac.cn).


References


Ahlrichs, W.H., 1995, Ultrastruktur und Phylogenie von Seison nebaliae (Gruber 1859) und Seison annulatus (Claus 1876): Hypothesen zu phylogenetischen Verwandtschaftsverhältnissen innerhalb der Bilateria: Göttingen, Cuvillier, 310 p.


Bengtson, S., 1977, Early Cambrian button-shaped phosphatic microfossils from the Siberian Platform: Palaeontology, v. 20, p. 751–762.


Budd, G.E., 2001, Tardigrades as “stem-group arthropods”: The evidence from the Cambrian fauna: Zoologischer Anzeiger, v. 240, p. 265–279.


Chen, J., 2004, The Dawn of Animal World: Nanjing, Jiangsu Science and Technology Press, 366 p.


Conway Morris, S., 1977, Fossil priapulid worms: Special Papers in Palaeon- tology, v. 20, p. 1–95.


Conway Morris, S., and Robison, R.A., 1986, Middle Cambrian priapulids and other soft-bodied fossils from Utah and Spain: University of Kansas Paleontological Contributions, v. 117, p. 1–22.


Dong, X.-P., and Zhang, H.Q., 2017, Middle Cambrian through lowermost Ordovician conodonts from Hunan, South China: Journal of Paleontology, v. 91, 1–89. (=Memoirs, v. 73, 1–89.).


Dong, X.-P., Donoghue, P.C.J., Cheng, H., and Liu, J.B., 2004, Fossil embryos from the middle and late Cambrian period of Hunan, South China: Nature, v. 427, p. 237–240.


Dong, X.-P., Bengtson, S., Gostling, N.J., Cunningham, J.A., Harvey, T.H.P., Kouchinsky, A., Val’kov, A.K., Repetski, J.E., Stampanoni,M., Marone, E., and Donoghue, P.C.J., 2010, The anatomy, taphonomy, taxonomy and systematic affinity of Markuelia: Early Cambrian to Early Ordovician scalidophorans: Palaeontology, v. 53, p. 1291–1314.


Duan, B., and Dong, X.-P., 2013, Furongian (late Cambrian) palaeoscolecid cuticles from Hunan Province, South China: The growth impact on the worm cuticle: Acta Scientiarum Naturalium Universitatis Pekinensis, v. 49, p. 591–601.


Duan, B., Dong, X.-P., and Donoghue, P.C.J., 2012, New palaeoscolecid worms from the Furongian (upper Cambrian) of Hunan, South China: Is Markuelia an embryonic palaeoscolecid?: Palaeontology, v. 55, p. 613–622.


Harvey, T.H.P., Dong, X.-P., and Donoghue, P.C.J., 2010, Are palaeoscolecids ancestral ecdysozoans?: Evolution & Development, v. 12, p. 177–200.


Haug, J.T., Maas, A., Waloszek, D., Donoghue, P.C.J., and Bengtson, S., 2009, A new species of Markuelia from the middle Cambrian of Australia: Memoirs of the Association of Australasian Palaeontologists, v. 37, p. 303–313.


Harvey, T.H.P., and Butterfield, N. J., 2016, Exceptionally preserved Cambrian loriciferans and the early animal invasions of the meiobenthos: Nature Ecology & Evolution, v. 1, 0022.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124