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Flashcards in Vertebrae taxonomy sheet Deck (46):
1

Jawless Fishes

vertebrata; agnatha

2

what species is an agnathan

jawless fish

3

living groups of agnatha

Two extant (living) groups: Hagfish (Myxiniformes) and Lampreys (Petromyzontiformes)

4

characteristics of agthana

 Lack bone and jaws (bone may have been lost in these groups).

 No paired fins (pectoral, pelvic), but do have unpaired fins: dorsal (lampreys only)
and caudal fin.

 Feed by sucking on to prey and piercing flesh with horned tongue.

 Rows of paired gill openings; water flows in and out of the gills (they cannot use their
mouths in ventilation as they are attached to prey).

5

why is agnatha not a natural grouping

 Some studies place hagfish outside the vertebrates, making lampreys more closely
related to jawed fishes than to hagfish. Hagfish plus Vertebrata then forms the clade
Craniata. In these cases, Agnatha is not a natural grouping.

6

what specimen are chondrichthyan

Cartilaginous Fishes - Vertebrata; Gnathostomata;

Chondrichthyes
~ 700 extant species of sharks, rays and chimeras

7

chondrichthyan features


 Skeletons are formed from prismatic cartilage – no bone.
 Covered in placoid scales (structure like teeth; with a dentine crown, a pulp cavity and
a bony base).
 True teeth, which are shed and replaced regularly in modern species.
 All but the oldest fossil species have a pelvic clasper (in males) used in mating and
formed from the pelvic metapteygium (basal axis of the fin).

8

what species is an actinoptergii

Ray-finned Fishes – Vertebrata; Gnathostomata; Osteichthyes; Actinopterygii
Ray-fins/actinopterygians form one of the two subgroups of bony fish (Osteichthyes), the other
being lobe-finned fish, or Sarcopterygii, from which all tetrapods evolved. The only extant fishlike
sarcopterygians are the coelacanths and lungfish.

9

Actinopterygii features

 Actinopterygians have modified the general osteichthyan character of a lung into a swim
bladder, which aids in regulating buoyancy.
 Single dorsal fin.
 The skeleton of the paired fins is formed from many small bones (radials) in a fan-like
arrangement.
 Covered in ganoid scales (vascular bony tissue at the base, covered in a layer of dentine
followed by enamel-like ganoine). These have been modified in some groups into cycloid or
ctenoid scales, wwhich improve locomotor efficiency through a reduction in weight and increase
in flexibility.

10

tetrapods

Tetrapods evolved from lobe-finned fish and include all extant terrestrial vertebrates (and their
relatives that returned to the water): amphibians, mammals, and reptiles (including birds).

11

tetrapod characteristics

Theyhave a characteristic appendicular (limb) skeleton – the scapula, humerus, radius and ulna form the
forelimb, while the pelvis, femur, tibia and fibula form the hind limb.

Note that tetrapod groups in
which one or both of the limbs is not present - such as snakes, caecilians, and cetaceans - have lost
their appendicular skeleton secondarily

12

what specimen is an anuran

Frogs and Toads – Lissamphibia; Anura

13

anuran features

 The skeleton is highly modified for jumping:
 Elongate bones of the hind-limbs, including ankle bones.
 A urostyle: the ilia (one of the bones of the pelvis) run forwards and neighbouring
vertebrae are fused into a rod, forming a strong pelvic basket.
 Short stiff vertebral column (9 or less vertebrae) and no ribs.
 Short and flat head.
 No teeth on the dentary.
 Compound (fused together) radio-ulna.

14

what species is an urodela

Salamanders – Lissamphibia; Caudata or Urodela

15

urodela characteristics

Salamanders – Lissamphibia; Caudata or Urodela
 Elongate body, generally with four short limbs and a flattened swimming tail.
 Broad, flattened skull, large orbits, and bicuspid teeth on both mandibles.
 Bicipital rib-bearers on vertebrae (the elements that articulate with the ribs have two prongs).

16

what species is a gymnophionan

Caecilians – Lissamphibia; Gymnophiona

17

gymnophionan characteristics

Caecilians – Lissamphibia; Gymnophiona
 No appendicular skeleton (no limbs, no shoulder and pelvic girdles).
 95-285 presacral vertebrae (vertebrae anterior to the sacrum – where the pelvic girdle would
meet the spine).
 Skull composed of several compound ossifications (it is compact and solid for burrowing).
 200+ lymphatic hearts situated intersegmentally under the skin.

18

what are amniotes

Amniotes are tetrapods that develop from an amniotic egg – an egg with an amnion (a particular
membrane) - and includes reptiles (turtles, lizards, snakes, amphisbaenians, crocodiles, dinosaurs,
birds, pterosaurs etc) and mammals.

The former are members of the major lineage Sauropsida,
while the latter are members of Synapsida.

19

testudines?

Turtles – Amniota; Sauropsida; Parareptilia (formerly Anapsida); Testudines

20

testudines? features

 The skull has no temporal fenestrae (openings in the skull near the temples) – the anapsid
condition - unlike all other amniotes – mammals have one (synapsid) and other extant reptiles
have two (diapsid).
 The trunk is surrounded by a two-layered shell - carapace (dorsal) and plastron (ventral). These
have a skeletal component (the carapace fuses with ribs and vertebrae) and an epidermal horny
component. The latter forms surface scales called scutes.
 They have a horny beak instead of teeth.

21

lizards?

Lizards - Amniota; Sauropsida; Diapsida; Lepidosauria; Squamata

22

lizard characteristics?

 Sprawling gait (body twists from side to side when they walk), though some have lost their legs.
 Moveable eyelids (unlike snakes).
 Relatively kinetic skull (well-jointed, with many moveable joints). The two sides of the
mandible are fused together (mandibular symphysis), unlike in snakes.

23

snakes

Snakes - Amniota; Sauropsida; Diapsida; Lepidosauria; Squamata; Serpentes

24

snake characteristics

Snakes mostly likely evolved from a group of burrowing lizards, making them members of the
lizard clade, Squamata.
 Limbless, but some (e.g., boas and pythons) retain traces of a pelvic girdle.
 Well-developed chemosensation, with forked tongue.
 Highly kinetic skull with eight points of rotation, allowing large prey to be swallowed whole.
Each side of the skull can move independently.
 Many elements of the skull reduced or lost.
 Two sides of the mandible are loosely connected with cartilage

25

Rhynchocephalia

Tuataras - Amniota; Sauropsida; Diapsida; Lepidosauria; Rhynchocephalia

26

Rhynchocephalia characteristics

A once-diverse order of lizard-like reptiles, now represented by a single genus (Sphenodon) -
containing two species of tuatara.
 Enlarged palatine tooth row – allowing the application of three-point bending to food items.
This is a feature unique among amniotes.
 Acrodont dentition - teeth fused to the crest of the jawbone, with no sockets.
 Posterior extension of the dentary.
 Sprawling gait (body twists from side to side when they walk).
 Well-developed parietal eye, with its own functional lens and retina. This is a photoreceptive
organ associated with the pineal gland, and may function to determine light/dark cycles
(circadian rhy

27

crocodiles

Crocodiles & Alligators – Amniota; Sauropsida; Diapsida; Archosauria; Crocodylia

28

crocodile characteristics


This group of archosaurs have many characteristics that suggest their fossil ancestors were warmblooded;
however, extant species are ectotherms. These characteristics are consistent with the
endothermy observed in birds - the closest living relative to crocodilians - as well as the extinct
ancestors of birds (non-avian dinosaurs).
 Nostrils at the tip of a long snout, connected to the internal nares via a long secondary palate,
separating the nasal passage from the mouth. This allows the animals to eat and breathe
simultaneously, like an endotherm.
 Semi-erect gait: they can pull their bodies upwards, straightening their legs slightly, giving them
a stance in-between that of a horse and a lizard.

29

how do crocodiles and alligators differe

CROCODILES AND ALLIGATORS DIFFER IN THE SHAPE OF THEIR MANDIBLES. THE
FOURTH TOOTH ON THE LOWER JAW IS OUTSIDE THE UPPER JAW IN CROCODILES,
WHILST ALL THE TEETH OF AN ALLIGATOR’S UPPER JAW BITE OUTSIDE OF THOSE
OF THE LOWER JAW.

30

birds

Birds - Amniota; Sauropsida; Diapsida; Archosauria; Dinosauria; Saurischia; Therapoda;
Aves

31

bird characteristics

Birds evolved from a group of small theropod dinosaurs in the Middle-Late Jursassic. Most avian
characteristics are flight-related, including many to reduce weight.
 Feathers (modified scales) for insulation, display, camouflage and flight.
 Wings formed of the humerus, radius, ulna, wrist and three digits (of these, the second and third
are greatly reduced).
 Fused clavicles forming the furcula (wishbone), and a sternum with a large keel for flightmuscle
attachment.
 Horny beak and no teeth

32

mammals

Mammals are members of one of the two major amniote radiations – the synapsids (the other being
the sauropsids). Synapsids are characterised by the presence of a single (lower) temporal fenestra -
still present, although modified, in living mammals. More specifically, mammals evolved from a
group of reptile-like synapsid ancestors called therapsids, and are characterised by producing milk
for their young (“mammal” is a derivative of “mammary”), as well as having a single bone in the
lower jaw – the dentary – associated with a distinct middle ear composed of three bony elements
(incus, malleus, and stapes). Most also have fur but this is largely lost in cetaceans (whales and
dolphins).

33

monotremes

Monotremes – Mammalia; Monotremata
Five extant species of egg-laying mammal: the platypus and four species of echidna. All are
restricted to Australia or Papua New Guinea.

34

monotreme characteristics


 Retain some ancestral (plesiomorphic) reptile-like characters: egg laying (oviparity); sprawling,
lizard-like gait; not entirely homeothermic.
 Produce milk from mammary glands but have no nipples.
 Males have a spur on their ankles (which produces poison in the platypus).
 Have no teeth (these have been lost) – the platypus has a leathery electrosensory bill with
crushing horny plates; echidnas have a horny rostrum with a long, sticky tongue for collecting
insects.

35

marsupials

Marsupials – Mammalia; Marsupialia
Five extant orders of pouched mammals from Australasia and the Americas. They evolved in North
America in the Early Cretaceous.

36

marsupial characteristics

 After a brief gestation in the womb with no placenta (except bandicoots), they give birth to
extremely immature young, which then develop to maturity through suckling in the mother’s
pouch.
 Three premolars and four molars.
 In-turned process on the dentary.
 Marsupial bones (two thin prongs of forward-facing bones) articulating with the pubes.

37

placental/eutherian

– a group with a worldwide distribution.
This means that the young develop in the womb with a complex chorio-allantoic membrane.
Marsupials and placentals split in the Early Cretaceous.

Eutheria is split into four groups, or
superorders: Xenarthra, Afrotheria, Laurasiatheria and Euarchontoglires.

38

example of xenartha

anteater, sloth, armadillo,

39

anteaters

Anteaters are restricted to South America, and are highly specialised for a diet of ants and termites.
 Long toothless skull with thin dentary and tubular snout.
 Very long sticky tongue.
 Small orbits.

40

arfotheria example

elephants sea cows aadvards elephant shrews golden moles tenrecs

41

sea cows

Sea cows - Eutheria; Afrotheria; Paenungulata; Sirenia
Four extant species of fully aquatic mammal, including the manatees (3x species) and the dugong.
Sirenians are the only living aquatic mammals that are herbivorous, and are large (adults usually 3-4
m head-tail) with stout bodies.
 Broad, paddle-like forelimbs and a horizontal tail fluke.
 Pelvic skeleton and hind limbs highly reduced, present as vestiges embedded within the trunk
musculature.
 Muscular lip-like projections flanking the mouth, equipped with stiff, sensory bristles – used to
locate and crop plant matter underwater.
 Small eyes.
 Dugongs are obligate feeders, having a strongly down turned snout. Their first pair of upper
incisors are also modified into tusks in adults. These features are not present in manatees.

42

euarchontogliares examples

primates tree shrews flying lemurs rodents rabbits

43

primates

Primates – Eutheria; Euarchontoglires; Euarchonta; Primates
 Large brain relative to body size, in which the cerebral cortex is especially enlarged.
 Relatively large eyes, and the orbits are protected either by a postorbital bar (typical of lemurs
and lorises) or by a complete bony cup referred to as postorbital closure (typical of monkeys
and apes).
 Retention of the clavicle (which is reduced or lost in many mammalian lineages).
 The general retention of five functional digits on the fore and hind limbs.
 Thumb (pollex) and big toe (hallux) usually opposable.
 Long gestation periods relative to maternal body size, and both fetal and postnatal growth are
characteristically slow in relation to maternal body size.

44

laurasiatheria

Eulipotyphlans (Insectivorans) – Eutheria; Laurasiatheria; Eulipotyphla
Four groups of small, insectivorous mammals: shrews, moles, hedgehogs, and solenodons. In the
past, Eulipotyphla was called Insectivora, and included many other groups, such as golden moles
and tenrecs, which have now been removed based on molecular phylogenetic evidence. Shrews and
hedgehogs are ecologically and anatomically quite similar to some of the earliest extinct placental
mammals.
 W-shaped cusps on the upper molars.
 No post-orbital process: a bar or projection of bone behind the orbit (present in most mammals).

45

examples of laurasiatheria

bats pangolins carnivores (bears, wolves, lions), odd hoofed animals, even hoofed animals, whales and dolphins

46

pangolin

pangolins – Eutheria; Laurasiatheria; Pholidota
Eight African and Asian species of insectivorous armoured mammals.
 Body covered in solid overlapping scales formed from keratin.
 Lack teeth – have an extremely long, sticky tongue for collecting insects.
 Long and strong claws.