Glossary of Animal Diversity

Question 1

akinetic

Answer 1

In anatomy, this refers to a low level of flexibility in a structure due to a lack of moveable joints.

Question 2

anapsid

Answer 2

Skull possessing no temporal fenestrae (NB. an- = without).

Amniotes with this skull condition form a paraphyletic group including the Parareptilia (turtles and their extinct relatives), the extinct common ancestor of all amniotes, and basal eureptiles (the extinct precursors of diapsids).

Note that the Testudines (turtles and relatives) have modified the anapsid condition through a reduction (emargination) of the posterior region of the skull.

Question 3

apatite

Answer 3

Calcium phosphate: the crystalline component of bone.

Question 4

appendicular skeleton

Answer 4

the endoskeletal element of the fins or limbs of a vertebrate, and their associated girdles (pectoral or pelvic).

Question 5

Axial skeleton

Answer 5

all parts of the vertebrate endoskeleton except the limbs or fins and their associated girdles. That is, the cranium, visceral skeleton, notochord, vertebrae, and ribs.

Question 6

Basal

Answer 6

Of, relating to, located at, or forming a base.

Question 7

bicuspid

Answer 7

A tooth bearing two cusps.

Question 8

calcified cartilage

Answer 8

Cartilage strengthened with a scattering of apatite crystals (calcium phosphate), as seen in Chondrichthians.

Question 9

cartilage

Answer 9

A tough, elastic, fibrous connective tissue composed of collagen fibres. Used as skeletal tissue in vertebrates, it is non-mineralised and is often the developmental precursor of bone.

Question 10

clade

Answer 10

a phylogentic lineage comprising a common ancestor and all its descendant species.

*Note that the difference between a taxon and a clade is that a clade must include all descendant species from a common ancestor, whereas a taxon need not.

Question 11

cladistic and cladogram

Answer 11

cladistic
Relating to the branching sequences of phylogeny.

cladogram
A branching tree-like diagram representing the phylogenetic relationships (evolutionary history) of a lineage.

Question 12

cloaca

Answer 12

The common opening for the reproductive, urinary, and digestive tracts, seen in all vertebrates except therian mammals (marsupials and placental mammals).

The term comes from the Latin for sewer.

Question 13

Cursorial

Answer 13

Adapted for running.

Question 14

Cusp

Answer 14

Cusp

The biting point of a tooth.

Question 15

Dentary

Answer 15

The anterior bone of the lower jaw which bears the teeth. It forms the whole of the lower jaw in mammals.

Question 16

Dentine

Answer 16

A bone-like substance, lacking cell bodies and consisting mainly of calcium phosphate (apatite) in a fibrous matrix.

Question 17

Dermal bone

Answer 17

A type of bone forming within the dermis - the deep layer of vertebrate skin cells below the surface layer, the epidermis.

Question 18

diapsid

Answer 18

Skull possessing both an upper and a lower temporal fenestra (NB. di- = two).

(two holes)

Amniotes with this skull condition form the monophyletic clade Diapsida, which includes the lepidosaurs (lizards, snakes, and tuatara), archosaurs (crocodilians, dinosaurs, and birds), and their other extinct relatives.

Note that some diapsids, such as lizards, have lost the temporal bar separating the fenestrae to form one large window. Others, such as the Aves (birds), have merged both fenestrae with the orbit.

Question 19

Endopterygota

Answer 19

A clade of insects charachterised by their undergoing complete metamorphosis (i.e. holometabolous).

Question 20

euryapsid

Answer 20

Skull possessing an upper temporal fenestra only.

*However, animals with this skull condition do not represent an important amniote lineage, as they are likely to be a polyphyletic group, originating a least twice within the Diapsida. Euryapsids include the plesiosaurs and ichthyosaurs - Mesozoic marine reptiles.

Question 21

extant

Answer 21

not extinct

Question 22

fossorial

Answer 22

Specialised for burrowing.

Question 23

furcula

Answer 23

the fused clavicle bones of a bird (wishbone)

Question 24

Holometabolous

Answer 24

Refers to a type of insect development that is categorised by four distinct, progressive life stages: embryo, larva, pupa, imago (adult).

Seen exlusively in the Endopterygota, which includes beetles, butterflies, wasps, bees, ants, and others.

Question 25

ilium

Answer 25

In tetrapods, the dorsal section of the pelvis, which articulates with one or more sacral vertebrae.

Question 26

kinetic

Answer 26

In anatomy, referring to a high level of flexibility afforded by numerous moveable joints.

Question 27

Lymph heart

Answer 27

Muscular dilation in a lymph vessel, which pumps lymph (fluid containing white blood cells called lymphocytes important in immune response) around the body of some lungfishes, amphibians and reptiles.

Question 28

monophyletic

Answer 28

Having a single evolutionary origin. A taxon is monophyletic if it contains all the descendants of a common ancestor.

For example, mammals are a monophyletic group, as all species descended from the first known mammal are considered mammals.

Question 29

Myrmecophagy

Answer 29

Feeding behaviour categorised by an exclusive (or near exclusive) diet of ants ant termites.

Question 30

Osteosclerosis

Answer 30

An increase in the density of bone.

Question 31

paraphyletic

Answer 31

A taxon including a common ancestor and some but not all of its descendants.

For example, the class Reptilia is paraphyletic, as it does not include birds, who are considered a separate class: Aves. However, birds evolved from theropod dinosaurs, and are therefore reptiles themselves. Similarly, all tetrapods are, evolutionarily speaking, lobe-finned fish.

Importantly, reptiles can be made monophyletic through the addition of birds to the taxon.

Question 32

Pectoral girdle

Answer 32

In vertebrates, the skeletal structure that provides support for the fore limbs or fins.

Question 33

Pelvic girdle

Answer 33

In vertebrates, the skeletal structure that provides support for the hind limbs or fins, which also fuses with the sacral vertebrae.

Question 34

phylogeny

Answer 34

The evolutionary history of organismal lineages as they develop through time.

Question 35

plesiomorphy

Answer 35

plesiomorphy

An ancestral character.

Question 36

polyphyletic

Answer 36

Referring to a group that does not contain the common ancestor of all the taxa within. Therefore, this is not a true taxonomic group, but is often a term used to categorise organisms with a similar ecology, such as insectivorious mammals, or marine mammals.

It is also used when the evolutionary origin of a group, such as snakes, is unsure, and characteristic species within may have originated separately.

Question 37

protocone

Answer 37

In mammals, the protocone is the mesiolingual cusp of an upper molar tooth.

Question 38

symplesiomorphy

Answer 38

A character that is shared between groups but was inherited from an ancestor prior to the last common ancestor.

These are characters that - at the level at which they are referred to as symplesiomorphies - are not used to form cladistic groupings, or clades.

Question 39

synapomorphy

Answer 39

A derived or specialised character that is shared between two or more groups, and was inherited from the common ancestor in which it originated.

These are the characters that morphological systematists use to support the existence of particular clades, forming the basis of the field of cladistics.

Question 40

synapsid

Answer 40

Skull possessing a lower temporal fenestra only.
(one hole)

Amniotes with this skull condition form the monophyletic clade Synapsida, which includes the mammals and their extinct ancestors, the non-mammalian reptile-like synapsids.

Note that in the Mammalia, the lower temporal fenestra has merged with the orbit.

Question 41

taxon

Answer 41

A group of organisms sharing a common ancestry.

Question 42

difference between taxon and clade

Answer 42

the difference between a taxon and a clade is that a clade must include all descendant species from a common ancestor, whereas a taxon need not.

Question 43

temporal fenestra

Answer 43

An opening in the temporal region of the skull seen in amniotes, providing a flat edge for the attachment of strong lower jaw closing muscles to the skull.

Question 44

amniote skull types

Answer 44

Amniotes show four skull types, based on the position and number of these temporal fenestrae, two of which define two major lineages of the amniotes. The skull types and associated groups are as follows:

1) Synapsid
2) Diapsid -
3) Anapsid
4) Euryapsid

Question 45

diapsid

Answer 45

Skull possessing both an upper and a lower temporal fenestra (NB. di- = two). Amniotes with this skull condition form the monophyletic clade Diapsida, which includes the lepidosaurs (lizards, snakes, and tuatara), archosaurs (crocodilians, dinosaurs, and birds), and their other extinct relatives. Note that some groups within the Diapsida, such as lizards, have lost the temporal bar separating the fenestrae to form one large window. Others, such as the Aves (birds), have merged both fenestrae with the orbit.

Question 46

anapsid

Answer 46

Skull possessing no temporal fenestrae (NB. an- = without). Amniotes with this skull condition form a paraphyletic group including the Parareptilia (turtles and their extinct relatives), the extinct common ancestor of all amniotes, and basal eureptiles (the extinct precursors of diapsids). Note that the Testudines (turtles and relatives) have modified the anapsid condition through a reduction (emargination) of the posterior region of the skull.

Question 47

euryapsid

Answer 47

• Skull possessing an upper temporal fenestra only. However, animals with this skull condition do not represent an important amniote lineage, as they are likely to be a polyphyletic group, originating a least twice within the Diapsida. Euryapsids include the plesiosaurs and ichthyosaurs - Mesozoic marine reptiles.

Question 48

synapsid

Answer 48

• Skull possessing a lower temporal fenestra only. Amniotes with this skull condition form the monophyletic clade Synapsida, which includes the mammals and their extinct ancestors, the mammal-like reptiles. Note that in the Mammalia, the lower temporal fenestra has merged with the orbit.

Question 49

cervical vertebrae

Answer 49

Cervical vertebrae: Facilitate the mobility of the head. The first two, the atlas and the axis are highly specialised, the former articulating with the occipital region of the skull.

Question 50

caudal vertebrae

Answer 50

Caudal vertebrae: Small and less specialised, forming the tail.

Question 51

sacral vertebrae

Answer 51

Sacral vertebrae: Fused to the pelvic girdle, allowing the transfer of force from the appendicular skeleton (limbs) during locomotion.

Question 52

lumbar vertebrae

Answer 52

Lumbar vertebrae: Generally larger, with small ribs not attached to the sturnum, which support the posterior musculature.

Question 53

thoracic vertebrae

Answer 53

Thoracic vertebrae: Articulate with the ribs that fuse with the sternum.

Question 54

Vestigial

Answer 54

Occurring as a structure that, once functional (whether during development or in earlier evolutionary forms), is now reduced or degenerate. An example is the vestigial pelvic girdle seen in many snakes, including the boas and pythons, which bears no function.

Question 55

Zygapophysis

Answer 55

Articular process of a vertebra that articulates with the corresponding process of an adjacent vertebra.

Plural = zygapophyses