Sedimentology and Palaeontology Lecture 3: Taxonomy, Bivalves and Brachiopods

Question 1

Define Taxonomy

Answer 1

The science of classifying and naming items into groups based on their similarities and differences

Question 2

Define Species

Answer 2

Generally the smallest taxonomic unit in use by biologists

Question 3

Define Genus

Answer 3

The taxonomical rank above species.

Genera (singular: genus) can hold one or more species.
- Homo sapiens (Genus being Homo)
- Tyrannosaurus rex (Genus being Tyrannosaurus)

Question 4

What are the many ‘species concepts’ Neontologists use when classifying organisms

Answer 4

-Interbreeding and reproductive viability of distinct
populations
- Genetic makeup
- Colour
- Adult size
- Vocalisations
- Behaviour
- Skeletal anatomy
- Soft-tissue anatomy
- Geography

Question 5

What do Palaeontologists use to classify organisms

Answer 5

-Skeletal anatomy
-Geography
-Stratigraphic distribution

Question 6

Define Morphospecies

Answer 6

Species defined on characters
of anatomical form. Characterizing a species on their structural and physical features/attributes

Question 7

What are the complications with morphospecies characterization

Answer 7

Ontogeny: growth of an
organism, which often
does not occur at
constant rates across the
body

Sexual dimorphism:
gender differences

Intraspecific variation:
the range of
morphologies within a
single species

Question 8

List the Linnaean classification

Answer 8

Kingdom > Phylum > Class > Order >
Family > Genus > Species

E.g.
Animalia > Chordata > Mammalia > Primates > Hominidae >
Homo > sapiens

Question 9

Define Bavalvia/Bivalves

Answer 9

Phylum Mollusca (chitons,
bivalves, gastropods,
cephalopods and others)

Lower Cambrian to Recent

Extremely abundant and
speciose in modern times

Marine and freshwater
species

Question 10

What is the Hypothetical ancestral mollusk(HAM) and what are its features?

Answer 10

The HAM is a theoretical mollusk illustration used to describe the anatomy of mollusks.

Anatomical features:
-CaCO3
shell
- Head with radula
- Visceral mass
- Foot
- Gills
- Mantle/mantle cavity

Question 11

Describe the bivalves shell anatomy

Answer 11

Usually aragonitic shells,
but calcitic or mixed
mineralogies are known

Periostracum present (=outermost organic layer)

Mantle attachment
indicated by pallial line

Pallial sinus allows for
inhalent/exhalent siphons
to be pulled in

Ligament holds shell together and open passively

Muscular effort required to hold the shell closed

Question 12

List the various lifestyles which bivalves may take up:

Answer 12

Floating along the seabed, propelling water to escape predators.

Burrowing into substrate, varying in hardness - depending on species.

Some species burrow directly into rocks.

Question 13

Describe the evolutionary history of the bivalve

Answer 13

First appeared c. 500 Ma

Most major groups developed by the Middle Ordovician

Mesozoic radiation of burrowing forms: response to the
Mesozoic Marine Revolution?

Question 14

What are rudists/rudist bivalves

Answer 14

Rudists are bivalves which have very strange morphologies, often looking tube, box or ring like. Rudists often resemble coral.

Ranged from Late Jurassic to Late
Cretaceous.

Question 15

Describe the phylum Brachiopoda

Answer 15

Early Cambrian to Recent

Exclusively marine
Over 4500 fossil genera, 120 modern

Calcite shell

Bilaterally symmetrical:
line of symmetry bisects shell

Question 16

Describe the anatomy of Brachiopods

Answer 16

Brachiopod is made up of two valves/shells; The pedicle valve(longer looking one) and the Brachial valve(Shorter looking).

A continuation of the mantle
epithelium and is linked directly
to the gut
- Supported by the brachidium

• Outer shell covered with a thin periostracum

Brachiopods use muscular
effort to hold their valves
open and closed

Only in marine environments, no freshwater

Question 17

What does articulate and inarticulate mean in relation to brachiopods

Answer 17

Articulate brachiopods are ones that possess ‘teeth’ which assist it in hinging their shells together.

Inarticulate brachiopods do not possess teeth and hinge their shells together using soft tissue alone.

Question 18

What is lingula?

Answer 18

Lingula: a living fossil?
- Oldest genus known
(perhaps of any
organism)
- c. 500 My range

Question 19

What are the differences between bivalves and brachiopods?

Answer 19

MORPHOLOGICAL
- Symmetry
- Shell mineralogy and microstructure
- Muscle scar placement
- Soft-tissue anatomy
- Feeding apparatus
- Hinge mechanism
- PLUS:
- Evolutionary history
- Habitats

Bivalves are freshwater and marine

Brachiopods are just marine