1A Collections

TF0110 Lithophaga inclusa

Thu, 20 Jun 2019 11:43:12 +0100

Title

TF0110

Lithophaga inclusa

Subject

Age

Jurassic

Location

Coral Rag, Upware

Description

Species

Lithophaga inclusa

Stratigraphic Range

Jurassic

Lithophaga: Triassic to recent

Taxonomy

Phylum: Mollusca
Class: Bivalvia
Order: Mytilida
Family: Mytilidae

Distinctive Features

Dorsoventral symmetry
Two valves
Growth lines
Umbo

Preservation

Set 1:
Original shell material
Set 2:
Mould of boring in which the shell lived (can see the structure of the Coral Rag)

Advanced notes

Lithophaga bore into hard substrates, and often preserve as the specimen from Set 2 has, as moulds of the borings they make. They lived as suspension feeders.

Lithophaga bore into rocks by secreting a weak acid. This dissolves calcareous substances, sometimes including other bivalve shells, into which the animal bores.

TF0108 Inoceramus

Thu, 20 Jun 2019 11:37:38 +0100

Title

TF0108

Inoceramus

Subject

Age

Cretaceous

Description

Stratigraphic Range

Jurassic to Cretaceous

Taxonomy

Phylum: Mollusca
Class: Bivalvia
Order: Praecardioida
Family: Inoceramidae
Genus: Inoceramus

Distinctive Features

Ribs
Umbo
Two valves
Near dorso-ventral symmetry

Preservation

Internal mould

TF0102 Liostrea

Thu, 20 Jun 2019 11:10:10 +0100

Title

TF0102

Liostrea

Subject

Age

Jurassic

Description

Species

Liostrea

Stratigraphic Range

Triassic to Eocene

Taxonomy

Phylum: Mollusca
Class: Bivalvia
Order: Gryphaeidae

Distinctive Features

Growth lines
Two articulating valves
Adductor muscle scar

Preservation

Original shell material

Advanced notes

Much like modern oysters Liostrea lived as a stationary epifaunal suspension feeder, encrusting hard substrates, after an initially planktonic larval stage.

TF0101 Dunbarella

Thu, 20 Jun 2019 11:08:07 +0100

Title

TF0101

Dunbarella

Subject

Age

Carboniferous

Description

Stratigraphic Range

Permian to Carboniferous

Taxonomy

Phylum: Mollusca
Class: Bivalvia
Order: Pectinida
Family: Pterinopectinidae

Distinctive Features

Ribs
Umbo
Growth lines

Preservation

Compression between mud layers
Potentially carbonization, though could be simply an external mould

Advanced notes

Because of the bilateral symmetry and preservation at first glance this could be mistakenly identified as a brachiopod. Other specimens, with different preservation, show that this is in fact a bivalve, and once you have seen enough of these you will know that Dunbarella is a bivalve not a brachiopod.

Bivalve

Thu, 20 Jun 2019 11:05:06 +0100

Title

Bivalve

Description

Taxonomy

Phylum: Mollusca

Class: Bivalvia

Diagnostic features

Palial line/palial sinus

Adductor muscle scars

Growth lines

Dorsoventral symmetry (some exceptions, for example Gryphaea)

Two hinged valves

Umbo

Hinge

Gills (rarely preserved)

Stratigraphic range

Cambrian to present

Way of life

Bivalves have occupied many environmental niches, living in a variety of ways:

Epifaunal, infaunal, nektonic

Marine, freshwater, brackish

Filter feeders through gills

Majority of bivalves begin life in a planktonic larval stage

By looking at the shell shape and palial sinus of fossil bivalves it is possible to say something about its mode of life.

Advanced notes

Apparent increase in bivalve diversity over time (or is this just a preservational bias?)

Bivalves makes their shells out of calite, aragonites, or both

The adductor muscles are used to keep the shell of the bivalve closed. This means that when they are relaxed, the ligament between the valves pulls them apart, so the 'relaxed state' for bivalves is 'open'.

The depth at which infaunal bivalves burrowed can be inferred from the palial sinus. The more prominent the palial sinus, the deeper the bivalve burrowed. This is because the size of the palial sinus is indicative of the size of siphon needed, which in turn depends on the depth of the burrow (deeper burrow, larger siphon).

Specimens

Browse bivalves

Links

youtube: scallops swimming

Cambridge University Museum of Zoology: Lifestyles of bivalves

Yale Peabody Museum of Natural History: differences between bivalves and brachiopods

Learn about types of preservation

Also

Go to the front of the 1A Lab. A display on the right hand side (by the window) shows a number of bivalves in life position. Have a look at how they have adapted their shape and other features to their way of life.