Limits...
Plated Cambrian bilaterians reveal the earliest stages of echinoderm evolution.

Zamora S, Rahman IA, Smith AB - PLoS ONE (2012)

Bottom Line: Many fossil echinoderms are radial and a few are asymmetric, but until now none have been described that show the original bilaterian stage in echinoderm evolution.Morphologically they are intermediate between two of the most basal classes, the Ctenocystoidea and Cincta.This provides a root for all echinoderms and confirms that the earliest members were deposit feeders not suspension feeders.

View Article: PubMed Central - PubMed

Affiliation: Department of Palaeontology, The Natural History Museum, London, United Kingdom.

ABSTRACT
Echinoderms are unique in being pentaradiate, having diverged from the ancestral bilaterian body plan more radically than any other animal phylum. This transformation arises during ontogeny, as echinoderm larvae are initially bilateral, then pass through an asymmetric phase, before giving rise to the pentaradiate adult. Many fossil echinoderms are radial and a few are asymmetric, but until now none have been described that show the original bilaterian stage in echinoderm evolution. Here we report new fossils from the early middle Cambrian of southern Europe that are the first echinoderms with a fully bilaterian body plan as adults. Morphologically they are intermediate between two of the most basal classes, the Ctenocystoidea and Cincta. This provides a root for all echinoderms and confirms that the earliest members were deposit feeders not suspension feeders.

Show MeSH

Related in: MedlinePlus

Fossil locality and geological setting.A, Map of Spain showing the location of the Iberian Chains (IC). B, Map showing the Purujosa locality in the northern part of the Iberian Chains. C, Geological map of Purujosa with indication of the studied section (marked with a star). D, Composite stratigraphic section indicating the level from where Ctenoimbricata spinosa was collected.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3368939&req=5

pone-0038296-g002: Fossil locality and geological setting.A, Map of Spain showing the location of the Iberian Chains (IC). B, Map showing the Purujosa locality in the northern part of the Iberian Chains. C, Geological map of Purujosa with indication of the studied section (marked with a star). D, Composite stratigraphic section indicating the level from where Ctenoimbricata spinosa was collected.

Mentions: Ctenoimbricata spinosa gen. et sp. nov. comes from the lowermost part of the Murero Formation at Purujosa, 2 km south of Purujosa village, Moncayo Natural Park, in the northern part of the Iberian Chains, NE Spain (Figure 2). Specimens come from the basal part of section Purujosa 6, which is middle Caesaraugustan in age, and were excavated under permit by the Gobierno de Aragon. The Murero Formation comprises a siliciclastic succession with some interbedded carbonate nodules, and is interpreted as having been deposited during transgressive conditions in an offshore environment. The position of Purujosa in the most distal part of the Iberian Chains favoured the preservation of multiple obrution events in which articulated echinoderms and complete trilobites are common [14], [24]. In addition, a new specimen of the ctenocystoid Courtessolea moncereti was collected by Mr. Daniel Vizcaïno from the classic section of Ferrals-les-Montagnes in the Montagne Noire, southern France and comes from the Coulouma Formation, which is Lower Languedocian in age. Both fossil levels fall within Cambrian Series 3, Stage 5 based on chemostratigraphic data from Álvaro et al. [25] in the latest Global Stratigraphic System (ca. 510 Ma).


Plated Cambrian bilaterians reveal the earliest stages of echinoderm evolution.

Zamora S, Rahman IA, Smith AB - PLoS ONE (2012)

Fossil locality and geological setting.A, Map of Spain showing the location of the Iberian Chains (IC). B, Map showing the Purujosa locality in the northern part of the Iberian Chains. C, Geological map of Purujosa with indication of the studied section (marked with a star). D, Composite stratigraphic section indicating the level from where Ctenoimbricata spinosa was collected.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368939&req=5

pone-0038296-g002: Fossil locality and geological setting.A, Map of Spain showing the location of the Iberian Chains (IC). B, Map showing the Purujosa locality in the northern part of the Iberian Chains. C, Geological map of Purujosa with indication of the studied section (marked with a star). D, Composite stratigraphic section indicating the level from where Ctenoimbricata spinosa was collected.
Mentions: Ctenoimbricata spinosa gen. et sp. nov. comes from the lowermost part of the Murero Formation at Purujosa, 2 km south of Purujosa village, Moncayo Natural Park, in the northern part of the Iberian Chains, NE Spain (Figure 2). Specimens come from the basal part of section Purujosa 6, which is middle Caesaraugustan in age, and were excavated under permit by the Gobierno de Aragon. The Murero Formation comprises a siliciclastic succession with some interbedded carbonate nodules, and is interpreted as having been deposited during transgressive conditions in an offshore environment. The position of Purujosa in the most distal part of the Iberian Chains favoured the preservation of multiple obrution events in which articulated echinoderms and complete trilobites are common [14], [24]. In addition, a new specimen of the ctenocystoid Courtessolea moncereti was collected by Mr. Daniel Vizcaïno from the classic section of Ferrals-les-Montagnes in the Montagne Noire, southern France and comes from the Coulouma Formation, which is Lower Languedocian in age. Both fossil levels fall within Cambrian Series 3, Stage 5 based on chemostratigraphic data from Álvaro et al. [25] in the latest Global Stratigraphic System (ca. 510 Ma).

Bottom Line: Many fossil echinoderms are radial and a few are asymmetric, but until now none have been described that show the original bilaterian stage in echinoderm evolution.Morphologically they are intermediate between two of the most basal classes, the Ctenocystoidea and Cincta.This provides a root for all echinoderms and confirms that the earliest members were deposit feeders not suspension feeders.

View Article: PubMed Central - PubMed

Affiliation: Department of Palaeontology, The Natural History Museum, London, United Kingdom.

ABSTRACT
Echinoderms are unique in being pentaradiate, having diverged from the ancestral bilaterian body plan more radically than any other animal phylum. This transformation arises during ontogeny, as echinoderm larvae are initially bilateral, then pass through an asymmetric phase, before giving rise to the pentaradiate adult. Many fossil echinoderms are radial and a few are asymmetric, but until now none have been described that show the original bilaterian stage in echinoderm evolution. Here we report new fossils from the early middle Cambrian of southern Europe that are the first echinoderms with a fully bilaterian body plan as adults. Morphologically they are intermediate between two of the most basal classes, the Ctenocystoidea and Cincta. This provides a root for all echinoderms and confirms that the earliest members were deposit feeders not suspension feeders.

Show MeSH
Related in: MedlinePlus