Glossary of Animal Diversity Flashcards
akinetic
In anatomy, this refers to a low level of flexibility in a structure due to a lack of moveable joints.
anapsid
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.
apatite
Calcium phosphate: the crystalline component of bone.
appendicular skeleton
the endoskeletal element of the fins or limbs of a vertebrate, and their associated girdles (pectoral or pelvic).
Axial skeleton
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.
Basal
Of, relating to, located at, or forming a base.
bicuspid
A tooth bearing two cusps.
calcified cartilage
Cartilage strengthened with a scattering of apatite crystals (calcium phosphate), as seen in Chondrichthians.
cartilage
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.
clade
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.
cladistic and cladogram
cladistic
Relating to the branching sequences of phylogeny.
cladogram
A branching tree-like diagram representing the phylogenetic relationships (evolutionary history) of a lineage.
cloaca
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.
Cursorial
Adapted for running.
Cusp
Cusp
The biting point of a tooth.
Dentary
The anterior bone of the lower jaw which bears the teeth. It forms the whole of the lower jaw in mammals.
Dentine
A bone-like substance, lacking cell bodies and consisting mainly of calcium phosphate (apatite) in a fibrous matrix.
Dermal bone
A type of bone forming within the dermis - the deep layer of vertebrate skin cells below the surface layer, the epidermis.
diapsid
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.
Endopterygota
A clade of insects charachterised by their undergoing complete metamorphosis (i.e. holometabolous).
euryapsid
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.
extant
not extinct
fossorial
Specialised for burrowing.
furcula
the fused clavicle bones of a bird (wishbone)
Holometabolous
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.
ilium
In tetrapods, the dorsal section of the pelvis, which articulates with one or more sacral vertebrae.
kinetic
In anatomy, referring to a high level of flexibility afforded by numerous moveable joints.
Lymph heart
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.
monophyletic
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.
Myrmecophagy
Feeding behaviour categorised by an exclusive (or near exclusive) diet of ants ant termites.
Osteosclerosis
An increase in the density of bone.
paraphyletic
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.
Pectoral girdle
In vertebrates, the skeletal structure that provides support for the fore limbs or fins.
Pelvic girdle
In vertebrates, the skeletal structure that provides support for the hind limbs or fins, which also fuses with the sacral vertebrae.
phylogeny
The evolutionary history of organismal lineages as they develop through time.
plesiomorphy
plesiomorphy
An ancestral character.
polyphyletic
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.
protocone
In mammals, the protocone is the mesiolingual cusp of an upper molar tooth.
symplesiomorphy
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.
synapomorphy
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.
synapsid
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.
taxon
A group of organisms sharing a common ancestry.
difference between taxon and clade
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.
temporal fenestra
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.
amniote skull types
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
diapsid
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.
anapsid
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.
euryapsid
- 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.
synapsid
- 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.
cervical vertebrae
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.
caudal vertebrae
Caudal vertebrae: Small and less specialised, forming the tail.
sacral vertebrae
Sacral vertebrae: Fused to the pelvic girdle, allowing the transfer of force from the appendicular skeleton (limbs) during locomotion.
lumbar vertebrae
Lumbar vertebrae: Generally larger, with small ribs not attached to the sturnum, which support the posterior musculature.
thoracic vertebrae
Thoracic vertebrae: Articulate with the ribs that fuse with the sternum.
Vestigial
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.
Zygapophysis
Articular process of a vertebra that articulates with the corresponding process of an adjacent vertebra.
Plural = zygapophyses
