Three-dimensionally preserved digestive systems of two Cambrian hyolithides (Hyolitha)

Sun, Haijing; Babcock, L E; Peng, J.; Zhao, Yuanlong

doi:10.3140/bull.geosci.1590

Cited by 22 publications

(10 citation statements)

References 7 publications

(12 reference statements)

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“…Sun et al (2016) mentioned the phylogenetic relationships of molluscs, sipunculans, hyolithids and orthothecids based mainly on the first appearance of group and development of the gut and intestine and orthothecids are treated here as a more primitive/ancestral group of hyoliths. Based on excellent material with preserved soft tissues of the hyolithid Haplophrentis Babcock & Robison 1988 …”

Section: Discussionmentioning

confidence: 99%

An orthothecid hyolith with a digestive tract from the early Cambrian of Bornholm, Denmark

Berg‐Madsen

Valent

Ebbestad

2018

GFF

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The hyolith assemblage from the early Cambrian of Bornholm, Denmark, shows a higher diversity than contemporary assemblages in Baltoscandia. The most common species in the Green Shales (Laeså Formation, Norretorp Member, Cambrian Stage 3), is Hyolithes [=Hyolithus] (Orthotheca) johnstrupi Holm, 1893. A specimen of this species shows a well-preserved and almost complete digestive tract, folded into an approximately 22 mm long chevron-like structure comprised of at least 20 arcuate loops on the ventral side and a flattened, gently sinuous to straight anal tube on the dorsal side. The thin, phosphatic outer shell layer of the conch is crushed under the digestive tract due to compaction while the digestive tract is preserved in three dimensions and appears undisturbed. The shape of the digestive tract is similar to that of the middle Cambrian Guduguwan hardmani (Etheridge) from Australia and the lower Cambrian specimens from Russia described by Meškova & Sysoev. The Danish specimen is probably an adult, lending support to the idea that the orthothecid digestive tract becomes more complex during ontogeny. Hyolithus (Orthotheca) johnstrupi is revised and here referred to Circotheca Sysoev, 1958.

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Section: Discussionmentioning

confidence: 99%

An orthothecid hyolith with a digestive tract from the early Cambrian of Bornholm, Denmark

Berg‐Madsen

Valent

Ebbestad

2018

GFF

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“…Hyoliths represent a unique opportunity to investigate the evolution of Cambrian taxa as they are common constituents of both exceptionally preserved faunas (such as the Burgess Shale and the older Chengjiang Fauna) and the so called Small Shelly Fossil (SSF) faunas. However the biology and phylogeny of hyoliths is still unclear (Marek and Yochelson, 1964;Runnegar, 1980;Valent, 2004, Sun et al, 2016, despite their abundant and global fossil record.…”

Section: Introductionmentioning

confidence: 99%

A hyolithid without helens preserving the oldest hyolith muscle scars; palaeobiology of Paramicrocornus from the Shujingtuo Formation (Cambrian Series 2) of South China

Zhang

Skovsted

2018

Palaeogeography, Palaeoclimatology, Palaeoecology

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The hyolithid Paramicrocornus zhenbaensis from the lower Cambrian (Cambrian Series 2) Shuijingtuo Formation of southern Shaanxi and western Hubei provinces of the Yangtze Platform is well-preserved in three dimensions. The morphology of the conch and operculum of P. zhenbaensis shows that this species lacked helens, which are considered to be characteristic of hyolithids and hence Paramicrocornus may belong to a sister group of other hyolithids. The shell structure of P. zhenbaensis reveals close similarities to the shell structure of other hyolithids. Furthermore, the smaller size and non-radial orientation of tubules in the shell structure of the operculum also differ from that in orthothecid hyoliths, suggesting that this characteristic may be used to differentiate hyolithids and orthothecids. The phosphatized opercula of P. zhenbaensis exhibit a pair of muscle scars located close to the apex of the internal surface. These muscle scars, as well as similar structures in other hyolithids, probably served as attachment sites of muscles controlling the retraction of the tentaculate feeding organ recently discovered in hyolithids. Without helens, P. zhenbaensis may have been sessile with the conch partly buried in the sea floor.

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“…Alternatively, they have been assigned to sipunculan worms (Sun et al . ) or to constitute their own phylum (Runnegar et al . ; Runnegar ).…”

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confidence: 99%

Homologous shell microstructures in Cambrian hyoliths and molluscs

Zhang

Skovsted

et al. 2018

Palaeontology

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Hyoliths were among the earliest biomineralizing metazoans in Palaeozoic marine environments. They have been known for two centuries and widely assigned to lophotrochozoans. However, their origin and relationships with modern lophotrochozoan clades have been a longstanding palaeontological controversy. Here, we provide broad microstructural data from hyolith conchs and opercula from the lower Cambrian Xinji Formation of North China, including two hyolithid genera and four orthothecid genera as well as unidentified opercula. Results show that most hyolith conchs contain a distinct aragonitic lamellar layer that is composed of foliated aragonite, except in the orthothecid New taxon 1 that has a crossed foliated lamellar microstructure. Opercula are mostly composed of foliated aragonite and occasionally foliated calcite. These blade or lath-like microstructural fabrics coincide well with biomineralization of Cambrian molluscs rather than lophophorates, as exemplified by the Cambrian members of the tommotiid-brachiopod linage. Accordingly, we propose that hyoliths and molluscs might have inherited their biomineralized skeletons from a non-mineralized or weakly mineralized common ancestor rather than as a result of convergence. Consequently, from the view of biomineralization, the homologous shell microstructures in Cambrian hyoliths and molluscs strongly strengthen the phylogenetic links between the two groups.

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Three-dimensionally preserved digestive systems of two Cambrian hyolithides (Hyolitha)

Cited by 22 publications

References 7 publications

An orthothecid hyolith with a digestive tract from the early Cambrian of Bornholm, Denmark

An orthothecid hyolith with a digestive tract from the early Cambrian of Bornholm, Denmark

A hyolithid without helens preserving the oldest hyolith muscle scars; palaeobiology of Paramicrocornus from the Shujingtuo Formation (Cambrian Series 2) of South China

Homologous shell microstructures in Cambrian hyoliths and molluscs

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