Ordovician–Silurian Chileida—First Post-Cambrian Records of an Enigmatic Group of Brachiopoda

Holmer, Lars E.; Popov, Leonid E.; Bassett, Michael G.

doi:10.1666/13-104

Cited by 6 publications

(6 citation statements)

References 15 publications

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“…M, Trifissura transversa (Salter in Davidson, ), Class Chileata, Superfamily Matutelloidea, Silurian, Wenlock, Homerian, Coalbrookdale Formation, Dudley, England; NHMUK B820a, ventral view of internal mould of conjoined valves (Holmer et al . ). N, Matutella grata Andreeva, , Cambrian Stage 5, Rassokha River, Siberia; Class Chileata, Superfamily Matutelloidea; CNIGR 8202, ventral valve exterior.…”

Section: Early Palaeozoic Radiation Of the Brachiopodamentioning

confidence: 99%

Brachiopods: origin and early history

2017

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Despite many major advances in recent years, three key challenges remain in bringing clarity to the early history of the phylum: (1) identifying the origin, morphology and life modes of the first brachiopods; (2) understanding the relationships of the major groups to each other and higher sister taxa; and (3) unravelling the roles of the Cambrian and Ordovician radiations that set the agenda for much of subsequent brachiopod evolution. Since some 95% of all brachiopod taxa are extinct, the fossil record is the primary source of data to frame and test models for the evolution of the phylum. The acquisition of new, and the redescription of existing faunas, in precise spatial and temporal frameworks, using new and well-established analytical and investigative techniques, are as important as ever.

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Section: Early Palaeozoic Radiation Of the Brachiopodamentioning

confidence: 99%

Brachiopods: origin and early history

2017

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“…Moreover, exceptionally preserved similar pedicles are also known to emerge apically from the Silurian chileate dictyonellid Eichwaldia subtrigonalis (Fig. 3.1–3.3; briefly described in the preceding) as well as from the recently described Silurian chileate Trifissura rigida , where the pedicle is preserved as a short series of phosphatized pads (Holmer et al, 2014, fig. 1).…”

Section: Discussionmentioning

confidence: 95%

“…Wright (1981) made the most recent detailed study of the unique attachment structures of the problematic rhynchonelliform Ordovician–Permian brachiopods belonging to the Dictyonellida, which are now classified as the Chileata together with the equally problematic Cambrian–Silurian Chileida (Holmer et al, 2014). The chileates most likely had posteriorly fused mantle lobes, and there is no delthyrium through which a posterior pedicle could pass in any of the known chileates (Popov and Holmer, 2007).…”

Section: Diversity Of Exceptionally Preserved Attachment Structures Imentioning

confidence: 99%

“…This new information has important phylogenetic connotations for our understanding of brachiopod evolution. The known record of early Paleozoic rhynchonelliform brachiopods with exceptionally preserved attachment structures (variously termed) emerging from apical perforations have increased recently, mainly recorded from the enigmatic chileates, but also from the obolellates (Zhang et al, 2011a, 2011b; Holmer et al, 2014). This type of attachment may have been widespread in early rhynchonelliforms, representing a potential plesiomorphic feature that possibly was lost repeatedly.…”

Section: Introductionmentioning

confidence: 99%

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The attachment strategies of Cambrian kutorginate brachiopods: the curious case of two pedicle openings and their phylogenetic significance

Holmer¹,

Zhang²,

Topper³

et al. 2017

J. Paleontol.

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The kutorginates are commonly the most abundant rhynchonelliform brachiopod found in the early Cambrian; they are also some of the oldest known rhynchonelliforms, first appearing in the Unnamed Series 2 (Atdabanian equivalent) and becoming extinct sometime in Cambrian Series 3 (Amgaian equivalent). Moreover, kutorginates are the first known member of the rhynchonelliforms for which we have a detailed knowledge of their soft-part anatomy, including the lophophore, digestive tract, and pedicle—all exceptionally preserved inKutorgina chengjiangensisZhang et al., 2007 from the early Cambrian Chengjiang Lagerstätte of southern China. The stout and annulated pedicle in the original report was described as protruding between the valves; however, newly collected better-preserved material now clearly shows that the pedicle actually protrudes from the apical perforation ofKutorgina chengjiangensis.This type of apical pedicle has also been described from other early Cambrian rhynchonelliforms, including the problematic chileateLongtancunella chengjiangensis(Zhang et al., 2011a). Exceptionally preserved similar pedicles are also known to emerge apically from the Silurian chileate dictyonellidEichwaldia subtrigonalisBillings, 1858, as well as from the recently described Silurian chileateTrifissura rigidaHolmer, Popov, and Bassett, 2014. However, it is clear that the only other exceptionally preserved kutorginate—a silicifiedNisusia—was provided with an adult pedicle emerging between the valves from a posterior gap; thus,Nisusiahas two pedicle openings. However, the apical foramen may represent the earliest attachment of the larvae, which subsequently became nonfunctional through ontogeny. It is suggested that both types of attachment strategies may have appeared early in the stem lineage of the Rhynchonelliformea.

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“…; Holmer et al . ) their microstructures remain unknown apart from probably having been lamellar (Hanken & Harper ; Balthasar et al . ).…”

Section: Discussionmentioning

confidence: 97%

Plywood‐like shell microstructures in hyoliths from the middle Cambrian (Drumian) Gowers Formation, Georgina Basin, Australia

Moore

Porter

2018

Palaeontology

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Hyoliths are a group of Palaeozoic fossils with calcareous shells whose affinities remain controversial. As their shells were originally aragonitic, their fossils are usually coarsely recrystallized, and few data on their microstructure are available. We report hyoliths from the middle Cambrian (Drumian, Floran) Gowers Formation of the eastern Georgina Basin, Queensland. These are preserved as phosphatic internal moulds, often with the inner layers of the shell also partly replaced by phosphate. Microstructural details preserved by this early diagenetic phosphatization show that these hyolith conchs were originally composed of fibrous crystallites, c. 0.5 μm wide, parallel to one another and to the inner surface of the shell. In several species, the fibres are arranged in a plywood‐like structure composed of multiple lamellae with a different fibre orientation in each lamella: often they are transversely oriented (relative to the long axis of the conch) in the inner part of the wall and longitudinally oriented in the outer part. Opercula also show a microstructure of parallel fibres. The lamello‐fibrillar microstructure we report from hyoliths is reminiscent of microstructures of many Cambrian molluscs; that this microstructure is found in both conchs and opercula suggests that these structures are serial homologues of one another, and in this respect they resemble brachiopod valves. As with many other biological plywoods, the hyolith shell probably records self‐organization in a liquid‐crystal‐like organic matrix. This provided a straightforward way to construct a material that could resist stresses from different directions, offering an effective defence against predators.

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Ordovician–Silurian Chileida—First Post-Cambrian Records of an Enigmatic Group of Brachiopoda

Cited by 6 publications

References 15 publications

Brachiopods: origin and early history

Brachiopods: origin and early history

The attachment strategies of Cambrian kutorginate brachiopods: the curious case of two pedicle openings and their phylogenetic significance

Plywood‐like shell microstructures in hyoliths from the middle Cambrian (Drumian) Gowers Formation, Georgina Basin, Australia

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