Guzhangian (mid Cambrian) trilobites from siliceous concretions of the Valtorres Formation, Iberian Chains, NE Spain

Álvaro, J. Javier; Zamora, Samuel; Vizcaı̈no, Daniel; Ahlberg, Per

doi:10.1017/s0016756812000416

Cited by 14 publications

(3 citation statements)

References 55 publications

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“…glabrata (Angelin, ) (MPZ 2012/57, MPZ 2017/310–312), which are three‐dimensionally preserved as external and internal moulds in siliceous concretions and came originally from rocks belonging to the Valtorres Formation (Cambrian Series 3, Guzhangian Stage) at Purujosa, northeast Spain (see Álvaro et al . for details of the locality). Parabailella was represented by an internal mould of an enrolled specimen of Parabailella languedocensis Thoral, (C‐12), which is three‐dimensionally preserved and came from the lowermost part of the Jince Formation (Cambrian Series 3, Drumian Stage) at the hill slope of Vinice near Jince in the Barrandian area, Czech Republic (see Fatka & Szabad for details of the locality) as well as five external moulds of the same species (MPZ 2017/314–318) also enrolled or semi‐enrolled and three‐dimensionally preserved, which are from the lowermost part of the Murero Formation (Cambrian Series 3, Drumian Stage) at Purujosa (see Zamora et al .…”

Section: Methodsmentioning

confidence: 99%

Modelling enrolment in Cambrian trilobites

Esteve¹,

Rubio²,

Zamora

et al. 2017

Palaeontology

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Trilobites were capable of enroling in different ways based on the flexible articulation of thoracic segments and associated interlocking devices; the type of enrolment (spiral or sphaeroidal) is thought to have largely depended on the coaptative devices that each trilobite used to enclose the body. Based on X-ray microtomography scans of complete enrolled specimens from the Cambrian, we created three-dimensional (3D) computer models to assess the kinematics needed to achieve both enrolment types. We demonstrate that closely related trilobites with little morphological variation (Bailiaspis?, Conocoryphe and Parabailiella) developed different enrolment types as a result of small variations in the number of thoracic segments and the angle between adjacent segments. Moreover, our models indicate that sphaeroidal enrolment, which is associated with a smaller number of thoracic segments, enabled faster encapsulation. This supports the hypothesis that there was a trend in the evolution of trilobites towards reduction in the number of thoracic segments in phylogenetically derived taxa in order to enhance the efficiency of enrolment.

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Section: Methodsmentioning

confidence: 99%

Modelling enrolment in Cambrian trilobites

Esteve¹,

Rubio²,

Zamora

et al. 2017

Palaeontology

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“…The material from Spain comes from a single stratigraphic level in the northern part of the Iberian Chains, northeast Spain, at the locality of Purujosa. In this area a well-developed section at the Borraca Creek displays the middle Cambrian Mesones Group (Liñán et al, 1992), which is divided into the Valdemiedes, Mansilla and Murero Formations (see Zamora et al, 2009;Álvaro et al, 2013 for more detailed geological information). Specimens of echinoderms have been collected from the Mansilla Formation where they occur as calcite skeletons associated with very common trilobites and brachiopods.…”

Section: Methodsmentioning

confidence: 99%

Stereom microstructures of Cambrian echinoderms revealed by cathodoluminescen

Gorzelak

Zamora

2013

Palaeontologia Electronica

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Echinoderms possess a skeleton with a unique and distinctive meshlike microstructure called stereom that is underpinned by a specific family of genes. Stereom is thus considered the major echinoderm synapomorphy and is recognized already in some Cambrian echinoderm clades. However, data on the skeletal microstructures of early echinoderms are still sparse and come only from isolated ossicles of limited taxonomic value in which the primary calcium carbonate has been replaced or thinly coated by phosphates, silica or iron oxides. Here, we applied cathodoluminescence (CL) to reveal stereom microstructures of the diagenetically altered calcitic skeletons of some Cambrian echinoderms (in particular Protocinctus, Stromatocystites and Dibrachicystidae). CL not only provides insights into the diagenesis of their skeletons but also reveals primary microstructural details that are not visible under transmitted light or SEM. Different stereom types (resembling labyrinthic, fascicular, galleried, microperforate and imperforate microfabrics) comparable to those observed in extant echinoderms have been recognized for the first time in these Cambrian taxa. Our results show that the stereom microstructures widely occur in various Cambrian echinoderm clades which suggest that they likely evolved the same genetically controlled biomineralization mechanisms as those observed in modern echinoderms. These results underline that the CL technique can be a powerful tool in the detection of the microstructural organization in even severely recrystallized echinoderm specimens. Given the close association between the skeletal microstructure and the investing soft tissues, the method presented here opens new possibilites for revealing skeletal growth and soft tissue palaeoanatomy of fossil echinoderms.

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“…The middle Cambrian genus Proampyx Frech, 1897, to which Ahlberg & Bergström (1978) tentatively referred the species, is morphologically distinctly different from E. linnarssoni. Proampyx is assigned to the family Agrau lidae (Geyer & Landing, 2001;Fletcher et al, 2005;Álvaro et al, 2012;Weidner & Nielsen, 2015). The type species, Proampyx acuminatus (Angelin, 1851) from Andrarum, southern Sweden, and the associated congeneric species Emended diagnosis: An Ellipsocephalus species with ante rior cranidial margin widely parabolic.…”

Section: Remarksmentioning

confidence: 99%

The shelly fauna and biostratigraphy of the lower Cambrian (provisional series 2, stage 4) Evjevik Member, Ringstrand Formation in the Mjøsa area, Norway

Høyberget¹,

Ebbestad²,

Funke³

et al. 2015

NJG

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New, extensive fossil material collected in situ from the lower Cambrian Evjevik Member in the Mjøsa type area, southern Norway, allows a re evaluation of the faunal distribution and diversity of the 'Ornamentaspis' linnarssoni Zone. Described taxa include three holmiid, six ellipsocephalid and one eodiscoid trilobite in addition to five helcionelloid molluscs. A Holmia species with affinities to the Swedish H. lapponica is common in the Evjevik Member. Librigenae, thoracic segments and pygidia from the poorly known, but biostratigraphically important trilobite 'Ornamentaspis' linnarssoni (Kiaer, 1917) are documented for the first time. The species is redescribed and transferred to Ellipsocephalus. Helcionelloid molluscs are represented by Helcionella antiqua (Kiaer, 1917), Stenotheca norvegica (Resser, 1938), Mackinnonia puppis n. sp., Mackinnonia? sp. and Latouchella sp. These are similar to taxa reported from coeval strata at Gislövshammar in southern Sweden and may prove to have biostratigraphical potential. The Holmia kjerulfi Zone, the Ellipsocephalus linnarssoni Zone and the Comluella? scanica-Ellipsocephalus lunatus Zone are readily recognised in the Lower Allochthon of the Mjøsa area and are in this report treated as distinctive, successive zones. New illustrations are provided of the brachiopod Magnicanalis rotundata (Kiaer, 1917), together with the enigmatic fossil Mongolitubulus Missarzhevsky, 1977, recorded for the first time in Norway.

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Guzhangian (mid Cambrian) trilobites from siliceous concretions of the Valtorres Formation, Iberian Chains, NE Spain

Cited by 14 publications

References 55 publications

Modelling enrolment in Cambrian trilobites

Modelling enrolment in Cambrian trilobites

Stereom microstructures of Cambrian echinoderms revealed by cathodoluminescen

The shelly fauna and biostratigraphy of the lower Cambrian (provisional series 2, stage 4) Evjevik Member, Ringstrand Formation in the Mjøsa area, Norway

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