An early Cambrian agglutinated tubular lophophorate with brachiopod characters

Zhang, Zhifei; Li, Guoxiang; Holmer, Lars E.; Brock, Glenn A.; Balthasar, Uwe; Skovsted, Christian B.; Fu, Dongjing; Zhang, X.L.; Wang, Haizhou; Butler, Aodhán D.; Zhang, Z.L.; Cao, Chang qun; Han, Jian; Liu, J.N.; Shu, Degan

doi:10.1038/srep04682

Cited by 51 publications

(75 citation statements)

References 34 publications

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“…This observation, and recently presented evidence that not all tommotiids may have had tubular scleritomes (Skovsted et al 2015a), strengthens suggestions that the evolution of the lophophorate stem group was more complex than previously imagined (Murdock et al 2014, Zhang et al 2014. The new material also opens up new avenues for future research into the distribution, structure and affinity of Small Shelly Fossils.…”

supporting

confidence: 53%

A silicified tommotiid from the lower Cambrian of Greenland

Skovsted¹

2016

Bull. Geosci.

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supporting

confidence: 53%

A silicified tommotiid from the lower Cambrian of Greenland

Skovsted¹

2016

Bull. Geosci.

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“…This said, tommotiids and early brachiopods deploy a wide variety of biominerals (Fig. 4): examples exist of non-mineralized, agglutinated, aragonitic, calcitic, phosphatic, and mixed calcite-phosphate shells 54,57,58 .…”

Section: Discussionmentioning

confidence: 99%

Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution

Zhao

Smith

Yin

et al. 2017

Sci Rep

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Orthrozanclus is a shell-bearing, sclerite covered Cambrian organism of uncertain taxonomic affinity, seemingly representing an intermediate between its fellow problematica Wiwaxia and Halkieria. Attempts to group these slug-like taxa into a single ‘halwaxiid’ clade nevertheless present structural and evolutionary difficulties. Here we report a new species of Orthrozanclus from the early Cambrian Chengjiang Lagerstätte. The scleritome arrangement and constitution in this material corroborates the link between Orthrozanclus and Halkieria, but not with Wiwaxia — and calls into question its purported relationship with molluscs. Instead, the tripartite construction of the halkieriid scleritome finds a more compelling parallel in the camenellan tommotiids, relatives of the brachiopods and phoronids. Such a phylogenetic position would indicate the presence of a scleritome in the common ancestor of the three major trochozoan lineages, Mollusca, Annelida and Brachiozoa. On this view, the absence of fossil Ediacaran sclerites is evidence against any ‘Precambrian prelude’ to the explosive diversification of these phyla in the Cambrian, c. 540–530 million years ago.

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“…Given that Scr and Antp are expressed in the shell-forming epithelium in brachiopods 32 , possible gene loss of Scr and Antp in the phoronid lineage may contribute to their shell-less morphology. This may also imply that common lophophorate ancestors had either unmineralized (agglutinated) or mineralized shells that were lost secondarily in crown phoronids 33,34 . With improved scaffolding, we discovered Lox4 in Lingula, which is linked between Post2 and Antp.…”

Section: Nature Ecology and Evolutionmentioning

confidence: 99%

Nemertean and phoronid genomes reveal lophotrochozoan evolution and the origin of bilaterian heads

et al. 2017

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*Nemerteans (ribbon worms) and phoronids (horseshoe worms) are closely related lophotrochozoans-a group of animals including leeches, snails and other invertebrates. Lophotrochozoans represent a superphylum that is crucial to our understanding of bilaterian evolution. However, given the inconsistency of molecular and morphological data for these groups, their origins have been unclear. Here, we present draft genomes of the nemertean Notospermus geniculatus and the phoronid Phoronis australis, together with transcriptomes along the adult bodies. Our genome-based phylogenetic analyses place Nemertea sister to the group containing Phoronida and Brachiopoda. We show that lophotrochozoans share many gene families with deuterostomes, suggesting that these two groups retain a core bilaterian gene repertoire that ecdysozoans (for example, flies and nematodes) and platyzoans (for example, flatworms and rotifers) do not. Comparative transcriptomics demonstrates that lophophores of phoronids and brachiopods are similar not only morphologically, but also at the molecular level. Despite dissimilar head structures, lophophores express vertebrate head and neuronal marker genes. This finding suggests a common origin of bilaterian head patterning, although different heads evolved independently in each lineage. Furthermore, we observe lineagespecific expansions of innate immunity and toxin-related genes. Together, our study reveals a dual nature of lophotrochozoans, where conserved and lineage-specific features shape their evolution. Articles NaTure eCOLOgy & evOLuTiONphoronids, ectoprocts and brachiopods, although the position of ectoprocts is questionable under a sensitivity analysis. Our results clearly show that lophotrochozoans have a different evolutionary history than other spiralians (or platyzoans), such as flatworms and rotifers. In particular, lophotrochozoans retain a basic bilaterian gene repertoire, which is probably lost in ecdysozoans and other spiralian lineages. Unexpectedly, genes specifically expressed in lophophores of phoronids and brachiopods are strikingly similar to those employed in vertebrate head formation, although novel genes, expanded gene families and redeployment of developmental genes also contribute to the unique molecular identity of lophophores. Furthermore, we provide examples of lineage-specific genomic features in lophotrochozoans, such as the expansion of innate immunity and toxin-related genes. Taken together, our study reveals the dual nature of lophotrochozoan genomes, showing both conservative and innovative characteristics during their evolution.

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An early Cambrian agglutinated tubular lophophorate with brachiopod characters

Cited by 51 publications

References 34 publications

A silicified tommotiid from the lower Cambrian of Greenland

A silicified tommotiid from the lower Cambrian of Greenland

Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution

Nemertean and phoronid genomes reveal lophotrochozoan evolution and the origin of bilaterian heads

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