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The oldest isorophid edrioasteroid [Echinodermata] and the evolution of attachment strategies in Cambrian edrioasteroids

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Zamora S., Smith A. B.

Acta Palaeontologica Polonica

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2010

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tom 55

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nr 3

487-494

Two new middle Cambrian edrioasteroid (Echinodermata), Protorophus hispanicus gen. et sp. nov., and Isorophida gen. et sp. indet., are described from the early middle Cambrian (Cambrian Series 3, Stage 5) of Spain. These are the oldest and probably the most primitive isorophids, a clade previously known from the upper Cambrian onwards. Specimens are attached to trilobite fragments indicating that edrioasteroids had by this time separated into two lineages each with different strategies for attachment, sediment attachers and hard substrate attachers. The single U−shaped ambulacral flooring plates of Protorophus are unique while Isorophida gen. et sp. indet. shares the presence of spines in common with some pyrgocystitid isorophids. The shift from facultative soft−bottom attachment to obligate hard−ground attachment in edrioasteroids involved the retention of a juvenile trait into adulthood and was already underway by the middle Cambrian.

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A new Middle Cambrian stem-group echinoderm from Spain: Palaeobiological implications of a highly asymmetric cinctan

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Zamora S., Smith A. B.

Acta Palaeontologica Polonica

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2008

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tom 53

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nr 2

A new exquisitely preserved stem group echinoderm (cinctan), Lignanicystis barriosensis gen. et sp. nov., is described from the Middle Cambrian of Los Barrios de Luna, North Spain. This displays a unique asymmetrical body plan with ventral projecting nodes that raised the lower surface above the substratum. There are four openings through the body wall: mouth, anus, atrium, and an aligned row of sutural pores of uncertain function. Unlike other cinctans, Lignanicystis has a strongly asymmetrical shape convergent with that of some cornute carpoids. Like cornutes, the test is also elevated above the substratum to allow water flow beneath the theca. In both cases this is probably an adaptation to life in higher water flow regimes.

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Morphology and ecological setting of the basal echinoid genus Rhenechinus from the early Devonian of Spain and Germany

80%

Smith A. B., Reich M., Zamora S.

Acta Palaeontologica Polonica

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2013

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tom 58

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nr 4

Based on new material from Germany and Spain, the echinoid “Lepidocentrus” ibericusfrom the Early Devonian (Emsian) of northern Spain is shown to be congeneric with Rhenechinusfrom the Hunsrück Slate of south−western Germany. New information on the lantern, pedicellariae and internal structure of the theca is provided, and confirms this genus as a member of the Echinocystitidae–Proterocidaridae clade and the most primitive of all Devonian echinoids. The two environmental settings in which Rhenechinus is found are very different: the Spanish specimens come from a relatively shallow−water bryozoan meadow setting while the German specimens are preserved in a deep−water setting. We deduce that the rare echinoid specimens from the Hunsrück Slate are all allochthonous, whereas the Spanish material is preserved in situ.

Ograniczanie wyników

3 Acta Palaeontologica Polonica

3 Smith A. B.

3 Zamora S.

1 Reich M.

1 2013

1 2010

1 2008

The oldest isorophid edrioasteroid [Echinodermata] and the evolution of attachment strategies in Cambrian edrioasteroids

A new Middle Cambrian stem-group echinoderm from Spain: Palaeobiological implications of a highly asymmetric cinctan

Morphology and ecological setting of the basal echinoid genus Rhenechinus from the early Devonian of Spain and Germany