https://wserv3.esc.cam.ac.uk/p1acollections/items/browse?tags=bilateral&output=atom <![CDATA[1A Collections]]> 2024-04-09T21:15:57+01:00 Omeka https://wserv3.esc.cam.ac.uk/p1acollections/items/show/135 <![CDATA[<h2><strong>TF0905<br /></strong></h2> <h2>Irregular echinoid</h2>]]>

Stratigraphic Range

Upper Cretaceous

Taxonomy

Phylum: Echinodermata
Class: Echinodea
Subclass: Irregularia
Order: Holasteroida

Distinctive Features

Bilateral symmetry
Mouth and anus out of line
Five radial ambulacra
Interambulacra with plates

Preservation

Sediment infill
Mineral replacement of shell

Advanced notes

Set 1: Anus and mouth appear to have been drilled to emphasise their positions.
Set 2: Fracturing of shell around the anus which obscures it. This would be a weak part of the shell which diagenetic processes have crushed.
]]> 2019-07-04T09:52:47+01:00

Title

TF0905

Irregular echinoid

Description

Stratigraphic Range

Upper Cretaceous

Taxonomy

Phylum: Echinodermata
Class: Echinodea
Subclass: Irregularia
Order: Holasteroida

Distinctive Features

Bilateral symmetry
Mouth and anus out of line
Five radial ambulacra
Interambulacra with plates

Preservation

Sediment infill
Mineral replacement of shell

Advanced notes

Set 1: Anus and mouth appear to have been drilled to emphasise their positions.
Set 2: Fracturing of shell around the anus which obscures it. This would be a weak part of the shell which diagenetic processes have crushed.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/134 <![CDATA[<h2><strong>TF0904<br /></strong></h2> <h2>Irregular echinoid</h2>]]>

Stratigraphic Range

Cretaceous

Taxonomy

Phylum: Echinodermata
Class: Echinoidea
Subclass: Irregularia
Order: Echinoneoida
Genus: Conulus

Distinctive Features

Bilateral symmetry
Five radial ambulacra
Interambulacra
Migrated periproct (opening for anus)
Peristome (opening for mouth)

Preservation

This fossil was collected in Quaternary river gravel. Originally it was preserved in the Upper Chalk (Cretaceous). This was broken up into clasts by erosive processes, one of which was this irregular echinoid. The echinoid clast was carried by a river downstream and deposited in the river gravel unit during the Quaternary.

Advanced notes

Note how the anus has migrated, but the peristome is still in the position you would expect from a regular echinoid (not migrated). Notice also how the ambulacra bearing the tube feet continue onto the underside, a feature not seen in more streamlined and derived irregular echinoids.
]]> 2019-07-04T09:52:47+01:00

Title

TF0904

Irregular echinoid

Subject

Source

Quaternary River Gravel, derived from Cretaceous chalk

Description

Stratigraphic Range

Cretaceous

Taxonomy

Phylum: Echinodermata
Class: Echinoidea
Subclass: Irregularia
Order: Echinoneoida
Genus: Conulus

Distinctive Features

Bilateral symmetry
Five radial ambulacra
Interambulacra
Migrated periproct (opening for anus)
Peristome (opening for mouth)

Preservation

This fossil was collected in Quaternary river gravel. Originally it was preserved in the Upper Chalk (Cretaceous). This was broken up into clasts by erosive processes, one of which was this irregular echinoid. The echinoid clast was carried by a river downstream and deposited in the river gravel unit during the Quaternary.

Advanced notes

Note how the anus has migrated, but the peristome is still in the position you would expect from a regular echinoid (not migrated). Notice also how the ambulacra bearing the tube feet continue onto the underside, a feature not seen in more streamlined and derived irregular echinoids.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/133 <![CDATA[<h2><strong>TF0903<br /></strong></h2> <h2>Irregular echinoid</h2>]]>

Species

Praecursor

Stratigraphic Range

Cretaceous

Taxonomy

Phylum: Echinodermata
Class: Echinoidea
Subclass: Irregularia
Order: Spatangoida
Genus: Micraster

Distinctive Features

Bilateral symmetry
Five radial ambulacra
Peristome (opening for mouth) and periproct (opening for anus) migrated
Spine attachment scars

Preservation

Sediment infil
Shell mineral replacement
Disarticulation of spines

Advanced notes

Note the streamlined shape for burrowing through the sediment, and how the ambulacra, which bear the tube feet, do not continue onto the underside of the animal where the mouth is.
This is because the tube feet are used for respiration but not for movement, for which small spines are used.
]]> 2019-07-04T09:52:46+01:00

Title

TF0903

Irregular echinoid

Subject

Location

Upper Chalk, Weston Colville, Cambridgeshire

Description

Species

Praecursor

Stratigraphic Range

Cretaceous

Taxonomy

Phylum: Echinodermata
Class: Echinoidea
Subclass: Irregularia
Order: Spatangoida
Genus: Micraster

Distinctive Features

Bilateral symmetry
Five radial ambulacra
Peristome (opening for mouth) and periproct (opening for anus) migrated
Spine attachment scars

Preservation

Sediment infil
Shell mineral replacement
Disarticulation of spines

Advanced notes

Note the streamlined shape for burrowing through the sediment, and how the ambulacra, which bear the tube feet, do not continue onto the underside of the animal where the mouth is.
This is because the tube feet are used for respiration but not for movement, for which small spines are used.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/132 <![CDATA[<h2><strong>TF0902<br /></strong></h2> <h2>Irregular echinoid</h2>]]>

Species

depressus Lestre

Stratigraphic Range

Jurassic

Taxonomy

Phylum: Echinodermata
Class: Echinoidea
Subclass: Irregularia
Order: Holectypoida
Genus: Holectypus

Distinctive Features

Bilateral symmetry
Five radial ambulacra
Spine attachment scars (very small)
Peristome and anus out of line

Preservation

Shell mineral replacement
Sediment infil
Disarticulation of spines

Advanced notes

This is a primitive irregular echinoid which would have had a functional jaw apparatus (not preserved) held within the peristome. The anus has migrated and the symmetry is bilateral, so this echinoid is clearly identifiable as irregular.
]]> 2019-07-04T09:52:46+01:00

Title

TF0902

Irregular echinoid

Subject

Location

Coralline Oolite, Upware, Cambridgeshire

Description

Species

depressus Lestre

Stratigraphic Range

Jurassic

Taxonomy

Phylum: Echinodermata
Class: Echinoidea
Subclass: Irregularia
Order: Holectypoida
Genus: Holectypus

Distinctive Features

Bilateral symmetry
Five radial ambulacra
Spine attachment scars (very small)
Peristome and anus out of line

Preservation

Shell mineral replacement
Sediment infil
Disarticulation of spines

Advanced notes

This is a primitive irregular echinoid which would have had a functional jaw apparatus (not preserved) held within the peristome. The anus has migrated and the symmetry is bilateral, so this echinoid is clearly identifiable as irregular.
]]> https://wserv3.esc.cam.ac.uk/p1acollections/items/show/118 <![CDATA[<h2>Echinoid</h2>]]> Taxonomy

Phylum: Echinodermata

Class: Echinoidea

Diagnostic features

Ambulacra (tube feet)

Periproct (opening for anus)

Peristome (opening for mouth)

Pentaradial symmetry (regular echinoids)

Bilateral symmetry imposed upon pentaradial symmetry (irregular echinoids)

Stratigraphic range

Ordovician to Present (Irregular Echinoids from Jurassic to Present)

Way of life

Regular echinoids:

Grazers with functional jaw apparatus

Long spines for protection and movement

Epifaunal at a wide range of depths

Use tube feet for respiration and movement

Irregular echinoids:

Feed on organic matter in sediment, front shaped to funnel sediment into mouth

Use fine spines to move

Infaunal burrowers

Use tube feet for respiration

Advanced notes

Grazing echinoids leave a distinctive pentagonal feeding trace Gnathicnus pentax.

Learn about types of preservation

Specimens

Browse echinoids

]]> 2019-08-06T10:58:24+01:00

Title

Echinoid

Description

Taxonomy

Phylum: Echinodermata

Class: Echinoidea

Diagnostic features

Ambulacra (tube feet)

Periproct (opening for anus)

Peristome (opening for mouth)

Pentaradial symmetry (regular echinoids)

Bilateral symmetry imposed upon pentaradial symmetry (irregular echinoids)

Stratigraphic range

Ordovician to Present (Irregular Echinoids from Jurassic to Present)

Way of life

Regular echinoids:

Grazers with functional jaw apparatus

Long spines for protection and movement

Epifaunal at a wide range of depths

Use tube feet for respiration and movement

Irregular echinoids:

Feed on organic matter in sediment, front shaped to funnel sediment into mouth

Use fine spines to move

Infaunal burrowers

Use tube feet for respiration

Advanced notes

Grazing echinoids leave a distinctive pentagonal feeding trace Gnathicnus pentax.

Learn about types of preservation

Specimens

Browse echinoids

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