Cambrian Tentaculate Worms and the Origin of the Hemichordate Body Plan

Nanglu, Karma; Caron, Jean‐Bernard; Cameron, Christopher B.

doi:10.1016/j.cub.2020.07.078

Cited by 14 publications

(12 citation statements)

References 38 publications

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“…The recently described Gyaltsenglossus senis (Fig. 2J) provides an interesting counterpoint to the three preceding taxa (Nanglu, Caron & Cameron, 2020a). Like them, it has the vermiform, trimeric body plan of an enteropneust, with an elongate proboscis similar to the genus Saccoglossus.…”

Section: Deuterostome Originsmentioning

confidence: 90%

“…Despite lacking direct evidence of the zooids, the rhabdopleurid affinities of the Cambrian graptolite tubes suggest that they were tentaculate suspension feeders (Maletz, 2017; Ramírez‐Guerrero & Cameron, 2021). Gyaltsenglossus appears to have been able to employ a combination of both tentaculate filter feeding and deposit feeding moderated by its long, Saccoglossus ‐like proboscis (Nanglu et al ., 2020 a ). Moreover, the Cambrian hemichordates with soft‐tissue preservation thus far appear to share a ubiquitous and morphologically distinct posterior structure, which may have been used for facultative attachment.…”

Section: Phylum Hemichordatamentioning

confidence: 99%

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Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development

et al. 2022

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Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and humans, among a wide variety of ecologically and morphologically disparate taxa. However, their early evolution is poorly understood, due in part to their disparity, which makes identifying commonalities difficult, as well as their relatively poor early fossil record. Here, we review the available morphological, palaeontological, developmental, and molecular data to establish a framework for exploring the origins of this important and enigmatic group. Recent fossil discoveries strongly support a vermiform ancestor to the group Hemichordata, and a fusiform active swimmer as ancestor to Chordata. The diverse and anatomically bewildering variety of forms among the early echinoderms show evidence of both bilateral and radial symmetry. We consider four characteristics most critical for understanding the form and function of the last common ancestor to Deuterostomia: Hox gene expression patterns, larval morphology, the capacity for biomineralization, and the morphology of the pharyngeal region. We posit a deuterostome last common ancestor with a similar antero‐posterior gene regulatory system to that found in modern acorn worms and cephalochordates, a simple planktonic larval form, which was later elaborated in the ambulacrarian lineage, the ability to secrete calcium minerals in a limited fashion, and a pharyngeal respiratory region composed of simple pores. This animal was likely to be motile in adult form, as opposed to the sessile origins that have been historically suggested. Recent debates regarding deuterostome monophyly as well as the wide array of deuterostome‐affiliated problematica further suggest the possibility that those features were not only present in the last common ancestor of Deuterostomia, but potentially in the ur‐bilaterian. The morphology and development of the early deuterostomes, therefore, underpin some of the most significant questions in the study of metazoan evolution.

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Section: Deuterostome Originsmentioning

confidence: 90%

Section: Phylum Hemichordatamentioning

confidence: 99%

Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development

et al. 2022

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“…Early echinoderms displayed great plasticity in terms of their body plan construction, with bilateral, asymmetrical, triradial and pentaradial forms described from the Cambrian [22,52]. Recent phylogenetic analyses [18,20,17,19] place bilateral and asymmetrical forms as stem-group echinoderms, indicating that some of the synapomorphies of crown-group echinoderms, such as pentaradial symmetry and ambulacra with flooring and cover plates, are not plesiomorphic for the phylum [16,22]. Our phylogenetic analyses recover Yorkicystis as a derived pentaradial form, most closely related to Cambrian edrioasteroids such as Kailidiscus, with the absence of skeleton in the extraxial part of the body owing to secondary loss.…”

Section: Discussionmentioning

confidence: 99%

“…To establish the relationships between Yorkicystis and other early echinoderms, parsimony and Bayesian phylogenetic analyses were performed. We chose to focus exclusively on pentaradial forms because all recent phylogenetic analyses [16][17][18][19][20][21] have recovered these as derived in echinoderm phylogeny. We selected all the major pentaradial morphotypes present in the Cambrian and early Ordovician for which fossil material is sufficiently well known, including a spiral form (Helicocystis), early edrioasteroids (Kailidiscus and Stromatocystites), isorophid edrioasteroids (Isorophus and Argodiscus), plesiomorphic blastozoans (Lepidocystis, Gogia and Vyscystis), an early glyptocystitid (Ridersia) and the earliest crinoids (Titanocrinus and Apektocrinus).…”

Section: Methodsmentioning

confidence: 99%

Cambrian edrioasteroid reveals new mechanism for secondary reduction of the skeleton in echinoderms

et al. 2022

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Echinoderms are characterized by a distinctive high-magnesium calcite endoskeleton as adults, but elements of this have been drastically reduced in some groups. Herein, we describe a new pentaradial echinoderm, Yorkicystis haefneri n. gen. n. sp., which provides, to our knowledge, the oldest evidence of secondary non-mineralization of the echinoderm skeleton. This material was collected from the Cambrian Kinzers Formation in York (Pennsylvania, USA) and is dated as ca 510 Ma. Detailed morphological observations demonstrate that the ambulacra (i.e. axial region) are composed of flooring and cover plates, but the rest of the body (i.e. extraxial region) is preserved as a dark film and lacks any evidence of skeletal plating. Moreover, X-ray fluorescence analysis reveals that the axial region is elevated in iron. Based on our morphological and chemical data and on taphonomic comparisons with other fossils from the Kinzers Formation, we infer that the axial region was originally calcified, while the extraxial region was non-mineralized. Phylogenetic analyses recover Yorkicystis as an edrioasteroid, indicating that this partial absence of skeleton resulted from a secondary reduction. We hypothesize that skeletal reduction resulted from lack of expression of the skeletogenic gene regulatory network in the extraxial body wall during development. Secondary reduction of the skeleton in Yorkicystis might have allowed for greater flexibility of the body wall.

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“…R. Soc. B 288: 20210061 simple posterior structures, possibly allowing them to remain attached to either their tubes or directly to the substrate [20,26,44]. In Oesia, it is bi-lobed and wrench-shaped [26].…”

Section: (B) Pseudo-colonial Structure Hypothesismentioning

confidence: 99%

Symbiosis in the Cambrian: enteropneust tubes from the Burgess Shale co-inhabited by commensal polychaetes

Nanglu

Caron

2021

Proc. R. Soc. B.

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The in situ preservation of animal behaviour in the fossil record is exceedingly rare, but can lead to unique macroecological and macroevolutionary insights, especially regarding early representatives of major animal clades. We describe a new complex ecological relationship from the middle Cambrian Burgess Shale (Raymond Quarry, Canada). More than 30 organic tubes were recorded with multiple enteropneust and polychaete worms preserved within them. Based on the tubicolous nature of fossil enteropneusts, we suggest that they were the tube builders while the co-preserved polychaetes were commensals. These findings mark, to our knowledge, the first record of commensalism within Annelida and Hemichordata in the entire fossil record. The finding of multiple enteropneusts sharing common tubes suggests that either the tubes represent reproductive structures built by larger adults, and the enteropneusts commonly preserved within are juveniles, or these enteropneusts were living as a pseudo-colony without obligate attachment to each other, and the tube was built collaboratively. While neither hypothesis can be ruled out, gregarious behaviour was clearly an early trait of both hemichordates and annelids. Further, commensal symbioses in the Cambrian may be more common than currently recognized.

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Cambrian Tentaculate Worms and the Origin of the Hemichordate Body Plan

Cited by 14 publications

References 38 publications

Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development

Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development

Cambrian edrioasteroid reveals new mechanism for secondary reduction of the skeleton in echinoderms

Symbiosis in the Cambrian: enteropneust tubes from the Burgess Shale co-inhabited by commensal polychaetes

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