An early Cambrian agglutinated tubular lophophorate with brachiopod characters - PubMed (original) (raw)

G-X Li 2, L E Holmer 3, G A Brock 4, U Balthasar 5, C B Skovsted 6, D-J Fu 7, X-L Zhang 7, H-Z Wang 3, A Butler 3, Z-L Zhang 7, C-Q Cao 2, J Han 7, J-N Liu 7, D-G Shu 7

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An early Cambrian agglutinated tubular lophophorate with brachiopod characters

Z-F Zhang et al. Sci Rep. 2014.

Erratum in

Abstract

The morphological disparity of lophotrochozoan phyla makes it difficult to predict the morphology of the last common ancestor. Only fossils of stem groups can help discover the morphological transitions that occurred along the roots of these phyla. Here, we describe a tubular fossil Yuganotheca elegans gen. et sp. nov. from the Cambrian (Stage 3) Chengjiang Lagerstätte (Yunnan, China) that exhibits an unusual combination of phoronid, brachiopod and tommotiid (Cambrian problematica) characters, notably a pair of agglutinated valves, enclosing a horseshoe-shaped lophophore, supported by a lower bipartite tubular attachment structure with a long pedicle with coelomic space. The terminal bulb of the pedicle provided anchorage in soft sediment. The discovery has important implications for the early evolution of lophotrochozoans, suggesting rooting of brachiopods into the sessile lophotrochozoans and the origination of their bivalved bauplan preceding the biomineralization of shell valves in crown brachiopods.

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Figures

Figure 1

Figure 1. Yuganotheca elegans gen. et sp. nov. from the early Cambrian Chengjiang Lagerstätte, Yunnan, China.

Arrows point to the borders between the upper pair of valves (Avs), median collar (Mc), lower conical tube (Pc), and pedicle (Pe); M = mouth; Lo = lophophore; Va = visceral area; Dg = the terminal pedicle bulb with adhered grains; Se = setae; Ten = tentacles. (a), Holotype, ELI BLW-0091, compare to b. (c–d), ELI BLW-0016AB, part and counterpart; note the lophophore imprint in d. (e), compare to d. (f), ELI BLW-0141A, complete individual with well developed pedicle. (g), close-up view of the marginal setae in Fig. S4f. (h–i), enlarged view of the lophophoral tentacles in Fig. S6b and a. The sketch drawings were made and organized together using CorelDraw 9.0 and finally converted to TIF format. Z. Zhang created these images.

Figure 2

Figure 2. Yuganotheca elegans gen. et sp. nov. from the early Cambrian Chengjiang Lagerstätte, Yunnan, China.

Arrows point to the borders between the anterior pair of valves, median collar, lower conical tube, and (in 2a, b, d) pedicle; all scale bars are 5 mm. (a), ELI BLW-0065B. (b), ELI BLW-0101, showing the central lumen (Pc) and the terminal bulb (Dg) of the pedicle. (c–d), showing the oblique growth fila of the lower cone and gut remains. c, ELI BLW-0018A. (d), ELI BLW-0095; note U-shaped lineation interpreted as the digestive tract marked by left (Lg) and right (Rg) parts; note the putative location of mouth (M) and probable anus (?A). (e), ELI BLW-0475A, showing well-preserved ventral mantle canals. (f), ELI BLW-0483B, interior dorsal valve.

Figure 3

Figure 3. Artistic reconstruction of Yuganotheca elegans gen. et sp. nov. with inferred semi-infaunal life position.

The figure was drawn manually by D. Fu using pencil and scanned as TIF format. Z. Zhang created the image.

Figure 4

Figure 4. A splits network of 330 most parsimonious trees retrieved through a TNT new technologies search (10,000 replications; using all four search algorithms built into TNT), suggesting Yuganotheca may be the most ancestral brachiopod bearing a tripartite attachment structure that combines characteristics of rhynchonelliform and linguliform brachiopods and features of some tommotiids.

The internal phylogeny of the crown groups (calcareous and apatite) brachiopods depend on the assumed polarity of biomineralization of shell, but Yuganotheca is invariably basal to the brachiopod crown, and closely allied to phoronids. U. Balthasar created the image.

References

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