16-20: Amniota: Reptilia, Aves, Mammalia Flashcards
1
Q
Describe the differences and relationships between Synapsids, Anapsids and Diapsids
A
Synapsids = One Skull Opening/Fenestration behind eye (includes Therapsids, Extinct Mammalian Ancestors, and all modern mammals)
Anapsids = No Skull Opening behind eye - might include turtles (based on skull anatomy) but this is debated
Diapsids = TWO Skull Openings behind eye - includes Lepidosaura (Lizards, Snakes and Tuataras) and Archosauromorpha (Crocodilians, Dinosaurs, Birds and possibly turtles)
2
Q
Summarise the appearance and evolution of Reptilia
A
Possibly emerged around 350 mya - first unquestionable reptile is Hylonomus, around 312 mya
Major radiation in Permian gave rise to Synapsida, Anapsida and Diapsida
Numerous and diverse in Mesozoic era (e.g., Turtles appeared)
Second great radiation in late Triassic (200 mya) gave rise to dinosaurs and pterosaurs
Birds evolve around 150 mya
All non-avian Dinosaurs extinct by 65 mya -> mammals diversify and increase in size
3
Q
Describe what was mentioned about the Icthyosaurs
A
They were extinct aquatic reptiles that thrived during much of the Mesozoic (until around 90 mya)
They evolved from unknown land reptiles, and were viviparous (egg was laid and hatched inside body)
4
Q
What does “Sauropsida” refer to?
A
“Sauropsida” largely overlaps with Reptilia, but is broader as it includes all extinct stem-group relatives of reptiles and birds
5
Q
Summarise the debate surrounding the position of Turtles within the Reptilian Phylogenetic Tree
A
They were traditionally placed as sister taxon to other reptiles, because their skull anatomy appeared to place them within the subclass Anapsida
However, molecular data has increasingly supported their position within the Diapsida (Hedges and Poling, 1999) - possibly even within the Archosauria along side Crocodilians (2012)
6
Q
Describe the structure of the amniote egg, and explain the advantages it brings as an innovation
A
- The amniote egg has a leathery outer shell, which provides external protection and interaction with environment
- Chorion - allows nutrients to pass through and provides protection
- Allantois - forms a sac that facilitates respiration and stores waste (fills up as yolk sac dwindles); eventually fuses with chorion
- Amnion - covers embryo and fills with amniotic fluid for protection
- Air space - for pipping (embryo pierces the inner membrane and starts lung ventilation in air space)
It allows expansion into new niches, as amniotes are no longer bound by the need to reproduce aquatically - the embryo is protected and nourished on land
Also, it lessens the size restriction of single-membrane fish eggs AND better protects the embryo
7
Q
Describe some key differences reproduction in amphibians and reptiles
A
- Reptiles show no metamorphosis
- Reptiles show internal fertilisation
- Reptiles lay eggs on land (and they have a shell)
- Extra-embryonic membranes in reptiles
8
Q
Brieflydescribe Palaeoythris (an early amniote from around the C-P boundary) and the key distinguishing features compared to amphibians
A
Palaeoythris had a much less sprawling gait and more robust bones - no need to swim anymore
(It was an agile insectivore that appeared similar to modern lizards)
9
Q
Describe the further anatomical developments seen in Procolophon (reptile from Late Permian to Late Triassic) compared to earlier reptiles like Palaeoythris
A
- Larger fore- and hind-limbs
- More massive hip- and shoulder girdles
- Stronger vertebral column
-> Much better adapted for fast locomotion
10
Q
State some key characteristics of the class Reptilia
A
- Tough, dry skin with keratinous scales
- Ossified skeleton
- Amniotic eggs - no larval stage
- More complex nervous system than ancestors
- More efficient and flexible circulatory system (septated heart)
- Larger lungs with thinner membranes -> more SA and more efficient movement of air
11
Q
Describe the Anapsid groups mentioned in the lecture
A
Procolophodon - lived from late Permian to end of Triassic (250-200 mya), broad skull, peg-toothed plant eaters -> fairly similar(ish) to other reptiles
Scutosaurus - lived from Lower to Upper Permian (260 mya) in Africa and Eurasia -> massively built, armoured reptile with complex teeth
Lecture mentions turtles (order Testudines) - but it seems to be controversial if they actually are Anapsids
12
Q
Describe the key features of Turtles (Testudines)
A
First appeared in the late Triassic (around 200 mya)
Enclosed within a shell (carapace) with fused vertebrae and lost intercostals
Oviparous and carnivorous
Since the ribs are immobile, with the lungs attached dorsally, breathing must be aided by the Post-Pulmonary Septum, and contraction of a range of different muscles for expiration and inspiration to drive the necessary pressure changes
13
Q
Describe the process of turtle evolution proposed by Lyson (2013)
A
Note: Morphological divergence aligns with phylogenetic divergence, and remains plausible whether turtles are considered as crown-Diapsida or not!
- Milleretta showed broad, L-shaped ribs and paired gastralia
- Eunotosaurus showed further broadening of ribs (T-shaped), and shortening of the drunk to 9 dorsal vertebrae
- Odontochelys showed broadening of dorsal neural spines, just 5 pairs of gastralia
- Proganochelys showed complete encapsulation of the scapula within the shell (appears very turtle-like) and ossification of carapace, also just 4 pairs of gastralia
14
Q
Describe the relationships between the main sub-groups within Diapsida
A
Lepidosauria:
- Tuataras
- Snakes (+ Amphisbaenians)
- Lizards
[The latter two/three comprise Squamata, the largest reptilian order]
Archosauria:
- Crocodilians
- Dinosaurs incl. Birds (via Theropods)
15
Q
When did the first Diapsids appear, when did they radiate and what were the distinctive features of the earliest Diapsids?
A
First appeared in Upper Carboniferous (300 mya)
-> These were athletic, with small, sharp teeth and large neck orbits
Radiated in Late Permian
16
Q
What is notable about the evolution of the Tuatara?
A
Share many features with their Mesozoic ancestors (one of the slowest rates of morphological evolution among the vertebrates)
17
Q
Describe the key features of lizards
A
Lizards are a diverse group of terrestrial burrowers and climbers
Most live in hot and arid climates - all are ectothermic
Moveable eyelids, keen vision, limited hearing
Semi-solid urine and diverse feeding mechanisms
They are technically paraphyletic, as some lizards are more closely related to snakes than they are to other lizards
18
Q
Describe the key features of the Amphisbaenia
A
“Worm-like Squamates”
- Most lack limbs, although a few have front limbs
- Robust skull for burrowing
- Absence of visible eyes and ears - hidden under skin
- Can walk backwards as well as forwards
Interesting biogeography - several major dispersals in Cenozoic, after breakup of Pangaea, implying continental drift may play less of a role in dispersal than previously thought
19
Q
Describe the key features of the Suborder Serpentes
A
Limbless Squamates, lacking pectoral AND pelvic girdles (though vestiges thereof in boas and pythons)
Ribs along length of body increase rigidity
Highly kinetic skull (4 bar system -> gape can be very large) allows diverse feeding options
Jacobson Organ - a richly innervated chemosensory epithelium (forked tongue places food particles onto organ, can detect heat from prey)
20
Q
Describe the features of the Crocodilians
A
Largest living reptiles (5-7m) with 64-68 teeth
Found in fresh AND saline water (salt glands can remove excess salt)
Closest living relatives to birds (and dinosaurs)
21
Q
Describe the locomotion of the Dinosauria common ancestor, and the kind of adaptations this may have required
A
BIPEDAL with fully erect posture (like all dinosaurs except Cerotopsians)
Needed hind limbs much longer and more robust than forelimbs (and specific adaptations in bones such as the cervical vertebrae, fibia, tibula, etc. to support this)
22
Q
Name some of the bones whose features (e.g., size, connection to other bones or muscles) are synapomorphies of Dinosauria
A
Ischium, Ilium + Pubis (Upper leg/Hip)
Tibia + Fibula (Lower leg)
Radius and Humerus (Upper limb)
Several bones in skull
23
Q
What are the two main groups of dinosaurs, what are some key sub-groups within these, and what key feature distinguishes them?
A
Saurischia (“Lizard-Hipped”) and Ornithischia (“Bird-Hipped”)
Saurischia includes Sauropodomorpha and Theropoda, while Ornithischia includes Thyreophora, Margniocephalia and Ornithopoda
The structure of the hip joints is distinctly different between these two groups
Note: birds actually evolved from Saurischia, not from “Bird-Hipped” Ornithischia
24
Q
When were the earliest known dinosaurs (and what were two examples)?
A
Earliest part of the Late Triassic (231 mya)
Eoraptor and Herrasaurus were two examples
24
Explain why some dinosaurs were quadrupedal, despite their common ancestor being bipedal?
This is a very rare transition in evolutionary history, but happened in three Ornithischian lineages
The most popular explanation is the expansion of head size and armouring of the skull - which may partially explain it, but the selection pressures in each of the three cases were different
-> Maybe more BR? ;)
25
Name the (mentioned) characteristics which can be reconstructed from fossil evidence using biological understanding?
Weight, Speed, Strength, Some Behaviour, Blood Temperature and Colour
26
Explain how weight of an extinct organism (e.g., a Dinosaur) can be reconstructed, how reliable the methods are, and the significance of working this out
Significance: Body Mass is actually the MOST important biological measure, as it impacts MANY key biological processes
The traditional method was to create a sculpture, based on the fossil evidence, then weigh the sculpture and scale up to full size - this was obviously unreliable and controversial
Another approach has been to find a skeletal measurement that seems to correlate well with body size among living species, and extrapolate [HOWEVER, large error bars when extrapolating outside calibration range - e.g., dinosaurs - resulting in a wide range of estimates]
You can also scan and digitalise physical skeletons, then estimate total body volume using software and calculate mass using known vertebrate tissue density [This is more reliable BUT does require a complete skeleton]
-> MORE POSSIBLE BR ;)
27
Explain how Sellers and Manning estimated the top speed of dinosaur species, and the advantage of this method over the more traditional methods of doing so
They created a musculoskeletal computer model of various species based on fossil evidence, then ran a simulation of their speeds
This allowed them to directly address assumptions about the animal's morphology, whereas traditional methods, such as anatomical comparisons, bone scaling and ground reaction force analyses hide these assumptions
28
Describe the significance of bones in reconstructing dinosaur biology and physiology
Bones are the main things that actually fossilise, meaning they are often the most significant preserved part of an organism and offer the most evidence
Their shape and size is important for estimating strength, AND modelling them helps to estimate top speed
29
Explain the debates surrounding the long necks of certain dinosaurs
It was previously argued that the largest dinosaurs were TOO large to be terrestrial, and thus must have been aquatic
However, there are trackways of these dinosaurs on land, and their lungs would not have been able to expand sufficiently if they were 8m deep in water, due to the pressure
There are, admittedly, other challenges to having a long neck, e.g., the heart has to work harder to pump blood up to the head, but giraffes prove this is possible to overcome
30
What was the debate surrounding a potential dinosaur heart first described in 2000?
Fischer et al claimed the fossil had a four-chambered heart and implied a high metabolic rate in the dinosaur
However, researchers in Chicago criticised this paper in 2003 for interpreting too much from an incomplete fossil, and also stated that the presence of a four-chambered heart in dinosaurs is to be expected due to its presence in birds and crocodiles, making this a less diagnostic feature than initially claimed
31
Describe what is meant by "neck springs?"
Neck Springs are a proposed explanation for how a dinosaur with a long neck (for example Diplodocus) may have solved the problem of raising its heavy neck again after lowering it to feed
Drawing comparison with the modern turkey, it was suggested that dorsal ligament tension would have extended the neck back up
32
Give some examples of how some behaviours/ecology can be inferred/reconstructed from dinosaur fossils
- The thick skulls of Stegaceras have been interpreted as evidence that they engaged in ramming behaviour when competing for mates, like sheep
- The modified (fused) caudal vertebrae of Ankylosaurus formed a club -> could have been used as a weapon for fighting
- Footprints can provide evidence for prey/predator ecology - though have to be careful to not assume too much because could just be two unconnected individuals walking through a similar area
33
What are the main theories for the function of the frills of Triceratops?
Most popular theory in recent years has been sexual selection (i.e. ornamental function)
However, some have argued that the damage commonly seen on these structures aligns well with a deer-style intraspecific pushing combat - Farke (2004) showed that this was possible, but there is currently insufficient evidence to infer that it DID happen
Some have also argued that the frills were for defence against predators, e.g., T rex, which was around at the same time
Note: horn mass:reach ratio suggests Triceratops would be an unusual example if their horns were for fighting
34
Are dinosaurs thought to be warm or cold blooded - and what is the evidence for this?
WARM-BLOODED (Homoiothermic)
They had nests similar in structure to modern bird nests, which only makes functional sense if warm-blooded parents were warm blooded
The low SA:Vol ratio of dinosaurs also makes cold-bloodedness unlikely
35
How can the colour of extinct species be interpreted?
The DNA that would have encoded pigment proteins cannot be preserved long enough to offer any evidence
However, other things that contribute to pigmentation (such as metals!) can survive, and thus offer SOME clues about the colour of dinosaurs
Also bear in mind that dinosaur vision was different to our own, so colour would have been selected differently as well
36
State some key similarities and differences between birds and reptiles
- Egg-laying
- Scales on legs
- Pneumatised bones
- Several skeletal similarities (e.g., Columella - single middle ear bone; lower jaw consists of several bones; intertarsal ankle joint)
-> Birds are ENDOTHERMIC, have 4-CHAMBERED HEARTS, and have FEATHERS
37
Describe the current view of the evolutionary origin of birds, how this has changed over time, and the importance of this example in terms of research more generally
Aves are understood to arise from theropod dinosaurs, with their lineage possibly diverging from other theropods tens of millions of years before the K-Pg extinction
Previously, they have been placed within the Archosauria (1920s), Avesuchia (1970s) and as a potential sister-taxon of dinosaurs
Botelho et al (2014) used developmental method to support the fusion of the radiale and intermedium (found as separate bones in dinosaurs) into a single bone in birds, as well as the fusion of distal carpals 1 and 2 to form the semilunate
This explains why birds have only 4 wrist bones (a fact which promotes a much more flexible wrist), and also highlights the importance of intersection between palaeontology and developmental biology
-> If arrive at the same conclusion, bolsters evidence for a hypothesis. If different, either one needs updating, or the existing model may be wrong, in which case, new discoveries can arise
38
Name and briefly describe the key non-Avialan dinosaurs that showed some bird-like features
Sinosauropteryx prima - the first FEATHERED non-Avialan dinosaur
- A small theropod (124-122 mya)
- Filamentous, downy-like feathers FOR INSULATION (this demonstrates how evolution often co-opts existing features)
Coudipteryx zoui (and Coudipteryx dongi)
- Small theropods, also 124-122 mya
- Now, symmetrical vaned and barbed primary feathers on the forelimbs (but still no secondary wing feathers)
Protoarchaeopteryx
- Another small theropod from 124 mya
- Probably had hollow, bird-like bones and a furcula (wishbone)
- Feathers with symmetrical vanes
All discovered in 1998 (first by Chen et al, others by Ji et al)
39
Name the three synapomorphies of Avialae
Flight
25 or fewer vertebrae
Pedal digit 1 is reversed and is at the bottom of the metatarsus
40
Describe the features of Archaeopteryx, and what
Archaeopteryx (150-145 mya) shows some bird-like features (for example, its asymmetrical feather vanes and pneumatised bones), but also some reptilian features (for example, its teeth and pubis)
It had a much smaller brain than modern birds, and its skull morphology is quite different
41
Summarise the interpretation of Foth et al (2014) regarding the origin of pennaceous feathers?
There is evidence that the common ancestor of Pennaraptora had pennaceous feathers, but the diversity of feather morphology among the clade suggests that feathers were initially evolved for display purposes, and may have been co-opted for aerodynamic functions multiple times, possibly convergently
42
Describe some of the early birds and their notable features
Confuciusornithidae
- Four genera from early Cretaceous (131-120 mya)
- Short tail with pygostyle (Pygostilians)
- Toothless beak
- Sternum NOT keeled (difference)
Enantiornithines
- 129-66 mys
- Toothed jaws (most lacked beaks)
- Pygostyle AND ALULA (-> flight?)
- Sternum NOT keeled
Hesperornithines
- 83-78 mya
- Diving birds with vestigial wings
- Modern birds may have evolved from a "transitional shorebird" following K-Pg bottleneck
-> Maybe BR on this ;)
43
Briefly describe the two major Super-orders of Modern Aves
1. Palaeognathae - Ratites (e.g., ostrich, emu, kiwi) and Tinamou
- Mostly flightless
- Skeletal anatomy of palate resembles reptilian more than Neognathan - vomer fused with palatine
2. Neognathae - most modern bird diversity
- Includes Galloanserae e.g., ducks; Water birds, soarers and forest birds
44
Describe some key aspects of Bird Vision
- Ascuity is SUPERIOR to that of other vertebrate groups
- Most have 3 eyelids and LARGE eyes relative to skull
- Many have an indented fovea, which magnifies the central part of the visual field (some, e.g., hummingbirds, even have 2 fovea in each eye)
- Birds can also see the UV part of the spectrum and have FOUR types of cone cells
45
Describe the beaks of modern birds, and the main hypotheses that may explain their evolution
Beaks are a toothless, keratin-sheathed structure homologous with the maxilla (upper jaw) and mandible (lower jaw) of dinosaurs
They are adapted based on ecology in different groups of birds, and show extreme diversity between generalists, insect catchers, fishers, filter feeders, and many more
Yang and Sander (2018):
- Some have proposed that birds had to lose their teeth to make flight possible -> but many Mesozoic birds flew with teeth
- Traditionally, explained through ecological factors - many recent studies support this, but does not fully explain why many Mesozoic birds with beaks were wiped out by K-Pg extinction, and only lineage of Aves survived (?)
- Some have claimed it strengthens the skull
- Yang and Sander (2018) propose reproductive + developmental factors
Also side note: adult toucans can use their bills as vascular controlled thermal radiators
46
Briefly describe how song is produced by birds (and name an example of a bird that uses a different mechanism)
The SYRINX is the organ that produces birdsong, located at the junction of the primary bronchi and trachea
When air is forced out through the trachea, propelled by the air sacs, it causes the labia (free moveable connective tissue membranes) to vibrate and generate song
The BITTERN, among others, produces song via a different mechanism, in that it does not use the syrinx, but rather uses its gullet like an echo chamber
47
Describe the respiratory system of birds, and its efficiency compared to mammals
They have NO diaphragm, but rather move air in and out of the lungs by using the AIR SACS to generate negative pressure
Air moves unidirectionally, first into the posterior air sacs and lungs, then into the anterior air sacs; in expiration, air moves out of the posterior air sacs via the parabronchi, and out of the anterior air sacs via the trachea
This system is MORE efficient than the bidirectional system of mammals
48
Describe the digestive tract of birds, and the functions of each section
1. CROP
-> Softens and regulates flow of food through the system by storing it temporarily
-> In SOME, produces milk-like fluid to feed young, e.g., flamingos, penguins, pigeons
2. STOMACH
2A - Proventriculus (glandular) produces mucus, pepsin and HCl for digestion
2B - Gizzard (muscular) tough and muscular, fills role of chewing teeth, also safety valve in owls [SOME contain stones or grit]
3. CAECA
-> contains bacteria that break down cellulose (large in pheasants and grouse)
4. CLOACA
-> opening for intestinal, urinary and reproductive tracts
-> uric acid leaves kidneys via ureters which empty directly into cloaca
49
Describe how the axial skeleton and musculature of birds is adapted to their ecology
Mainly adapted for flight:
- Lightweight, with many pneumatised bones
- Some bones fused into single ossifications, e.g., pygostyle (fused caudal vertebrae), furcula (fusion of clavicles), digits, synsacrum
- Keel of sternum important for attaching flight muscles (palaeognatha lack this)
- Strong, massive pectoralis muscles
- Supracoracoideus elevates wings in flight
Note: wing, leg and foot morphology ALSO correlates with ecology - maybe BR ;)
50
Describe the nature of Bird Skin
The epidermis and dermis are only a few cell layers thick, and lack sweat glands
Feathers are preened by applying waxy secretions
Also, birds moult and lose their feathers each year
51
Summarise the anatomy and types of feathers
They are considered the most complex integumentary structures found in vertebrates, and evolved from reptilian scales
Feathers are made of ß-keratin; the rachis is the central shaft, to which barbs are attached; the interlocking barbs form the vane of the feather
Down feathers (e.g., semiplume, filoplume, downy) are NOT vaned, while Tail and Flight feathers are
52
Name the three main biochrome pigments found in birds, the types of colours they each contribute to, and the advantages (if any) that they confer to the feather
1. MELANINS
-> earthy tones e.g., black, brown, grey
-> wear resistant, bacterial resistant and energy absorbing!
2. CAROTENOIDS
-> vibrant colours e.g., yellow, orange and red
3. PORPHYRINS
-> vibrant colours e.g., green pink and bright brown
53
Describe the two types of structural colours in bird feathers
Iridescent - refraction of light by microstructure of the barbules
NON-iridescent - small air pockets in the barbs scatter incoming light to produce blues
54
Describe the nature of reproduction in birds, and the two types of breeding systems in birds
Birds show internal fertilisation and extensive paternal care
They are amniotes, and produce eggs with a calcium carbonate shell (shell is covered with tiny surface pores, allowing embryo gas exchange via diffusion)
PRECOCIAL (e.g., Mallard) - Young are relatively mature and mobile
ALTRICIAL (e.g., American Robin) - Young are incapable of moving around on their own
55
Approximately when did the first synapsids appear?
During the mid-late Carboniferous (330-300 mya)
56
Name the three early Synapsid groups that went present during the Triassic and Jurassic
Pelycosaurs (died out at start of Triassic), Cynodonts (died out in late Jurassic) and "other early Therapsid Groups"
56
State the three distinguishing features of Synapsids mentioned at the start of the lecture
- ONE Lateral Skull Opening (located ventrally between skull roof and cheek)
- Enlarged canine-like teeth
- Stronger, arched palate
56
When did the early Therapsids first appear, and what were their distinguishing features?
Probably Mid-Permian (approx 260 mya) -> diversified between mid-Permian and Triassic
- Expansion of jaw musculature
- Erect gait
- Expansion of cerebellum
56
Describe the group Cynodonta in terms of their first appearance, features, and relationship to other Synapsids
They are a group of Therapsids that includes Mammalia and close relatives of mammalia, and the earliest known cynodont fossil is from 257 mya (2007) but they were especially diverse between the Triassic and mid-Jurassic
- Enlarged dentary bone and reduced post-dentary bone
- Well developed post-canine teeth
- Complete secondary palate
- Turbinate bones
- Loss of lumbar ribs
56
What are the Eutherians, when did they diverge and what features distinguish them from [other groups]?
Eutherians are PLACENTAL mammals (as opposed to Metatheria (Marsupials) or Prototheria (Monotremes)
Monotremes, then Marsupials both diverged in Cretaceous (around 120 mya)
- Modifications of Braincase
- Vertical tympanic membrane (between outer and inner ear)
- Penis/Ovaries but NO CLOACA
57
When did the first Mammals appear and what are their distinguishing characteristics?
Possibly Late Triassic (around 210 mya) -> first DEFINITE mammals were around 178 mya (early Jurassic) according to a Nature article from 2019, but some transitional Cynodont-Mammal fossils from Triassic
- Hair
- Mammary and Skin Glands
- Jaw Articulation
-> Three Ear Ossicles
-> Enlarged Neopallium
-> Modified vertebrae and Long Bones
58
Describe how the jaw of mammals differs from pelycosaurs and other earlier Synapsids
In Pelycosaurs (early Synapsids), the jaw joint was found between the articular and quadrate bones
In Cynodonts, a second jaw joint eventually evolved between the Dentiary and Squamosal bones
In Mammals, the Dentiary-Squamosal joint is the ONLY functioning jaw joint, while the articular and quadrate bones have a new role in sounds transmission to the inner ear
Also, in mammals, the Dentiary is the ONLY jaw bone
59
Describe the evolution of the palate in Synapsids
In Amphibians and many reptiles, there is only a primary palate
In some Therapsid reptiles, palatal processes extended the back of the palate
In mammals (and also in crocodiles and some turtles), there is a complete secondary palate, consisting of both hard bone and fleshy tissue (soft palate)
This change separates the food chamber and respiratory passage, allowing simultaneous breathing and mastication
It also increases skull strength and aids breathing while suckling
60
Describe the difference in locomotion systems between reptiles and early mammals and resulting changes in bone structure
Reduction of the reptilian pectoral girdle to rod-shaped clavicle (less need for large ventral muscles and ribs due to semi-erect gait)
Enlarged scapula allows attachment of new muscle groups and strengthening of shoulder joint; elbow, hip and ankle joints also lengthened
61
Describe the nature of hair in mammals
Made of keratin, forms either dense, soft underhair, or coarse guard hair
Pelage (hair, fur OR wool) can have colour
Can also form quills (e.g., in porcupines) as defense mechanism
62
Describe the different types of glands seen in mammals
1. SWEAT GLANDS (can be eccrine for cooling + grip, or apocrine for reproductive)
2. SCENT GLANDS (for marking and communication)
3. SEBACEOUS GLANDS (secrete sebum)
4. MAMMARY GLANDS (produce milk)
63
State the four main types of diets seen in mammals
Insectivores (hedgehogs, shrews, etc.)
Ruminant Herbivores (e.g., cows)
Non-ruminant Herbivores (e.g., rabbits)
Carnivores (e.g., foxes)
64
What is meant by the "Mouse to Elephant" curve?
It is a graph plotting mammals by metabolic rate against body weight, which shows a 1/x^2 type curve (i.e. metabolic rate is intense for small mammals, but declines sharply for larger mammals)
65
Can mammals fly?
Yes - bats have evolved powered flight (other groups do not have powered flight but can glide, e.g., flying squirrel)
66
Describe the different forms of reproduction seen in mammals
Oviparity in Monotremes
Viviparity with POUCHES in Marsupials
Viviparity (but less Altricial) in Eutherians/Placentals
67
What features distinguish primates from other mammals?
- "Primitive" limb anatomy (i.e. fairly similar to ancestral forms, whereas many other mammals are far more derived, e.g., whales, bats)
- Nails rather than claws (a few exceptions)
- GRASPING HANDS AND FEET
- UPRIGHT POSTURE IN MANY (some facultative, some obligate)
68
Describe the dentition of primates, and what this reveals about evolution of teeth when compared to other mammals
Most primates have fairly generalised dental anatomy (with a few exceptions, for example the tooth comb of the lemur, or the rodent-like teeth of the aye-aye)
Dentition reflects ecology and diet - many mammals are specialised for a particular diet (e.g., buffaloes are chewing specialists, which is reflected in their teeth), while primates are generalists in their diet, and thus generalists in their teeth
69
What are some common features of primates in terms of senses, brain and behaviour?
- Big brains
- Flexible behaviour
- Extended infant care
- Large social groups
- Short snouts and Large Eyes (i.e. favour vision over olfaction) -> EXCEPTION: Proboscis monkey has large nose, but this is assumed to be due to sexual selection, not olfaction
70
Describe the modern taxonomic groups within primates (and how they have changed from the previous ones)
Two Suborders, each with Infraorders and Superfamilies:
Order Strepsirhini:
--> Infraorder Lemuriformes
------> Superfamily Lorisoidea
------> Superfamily Lemuroidea
Order Haplorhini:
--> Infraorder Tarsiiformes
------> Superfamily Tarsioidea
--> Infraorder Platyrhini
------> Superfamily Ceboidea
--> Infraorder Catarrhini
------> Superfamily Cercopithecoidea
------> Superfamily Hominoidea
(Previously, suborders Prosimii and Anthropoidea broadly overlapped with Strepsirhini and Haplorhini respectively, but Tarsiiformes was grouped together with Lemuriformes under Prosimii
Now, Tarsiiformes grouped together with Platyrrhini and Catarrhini)
71
Describe where each major group of Primates can be found
Lemuriformes:
- Lemuroidea (Lemurs) on Madagascar
- Lorisoidea (galagos and lorisids) in Africa and Asia
Platyrrhini:
- Ceboidea (New World Monkeys) only in Central and South America
Catarrhini:
- Cercopithecoidea (Old World Monkeys) throughout Africa, Europe and Asia
- Hominoidea (Humans and Great Apes) in Africa and Asia -> only humans spread outside these continents
Side note I just discovered: Apes lack tails due to a mutation in the TBXT gene
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Place some well-know groups of Catarrhini in order, by how closely related to humans they are
- Old World Monkeys (Cercopithecoidea)
- Gibbons (and Siamang)
- Orang
- Gorilla
- Chimpanzee
Note: Gorilla and Chimpanzee are FAR more closely related to us than any other apes are
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Approximately when are Large Brains and Habitual Bipedalism thought to have first evolved
Facultative Bipedalism - at least 4 mya
Large Brains - much later, around 2 mya
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When are the earliest Hominins thought to have evolved?
- There is definite fossil evidence for an origin at least 4 mya (some recent finds have suggested more than 6 mya)
- These fossils share some anatomical traits (e.g., skull, teeth and body size) with humans, some with apes, and some are unique
- Several different taxa have been proposed as the earliest Hominin groups
- It is often difficult to be certain due to incomplete fossils
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What are the key features of Hominins?
- Habiutally Bipedal: can be seen by changes in pelvis and limb bones, and Foramen magnum (Hole for the spinal cord) being UNDERNEATH the skull instead of at the back of it
- Trends towards Small Canines, Parabolic Dental Arcade (i.e. NOT U-Shaped), Thick Enamel and Vertical Face
- DOUBLE-Curvature in spine allows better shock absorption
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Describe the species that some have argued are Hominins from the Miocene epoch (i.e. older than 5 mya)
- One from 6.5 mya (Sehelanthropus) is fairly gorilla-like but looks very human-like from the front
- One from 6 mya (Orrorin) - jaw and post-crania may suggest bipedalism
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Describe the Hominins from the early Pliocene epoch (i.e. 5-3 mya)
One from 4.5 mya (Ardipithecus) - previously thought to be a chimpanzee ancestor, but recent research suggests human ancestor; not enough evidence to confirm bipedality
One from 3.5 mya (Kenyanthropus) - probably not a human ancestor, might be an offshoot from the human lineage
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Describe the two main groups of Australopithecines
"Gracile Australopithecines" - Genus Australopithecus (4-2.5 mya)
"Robust Australopithecines" - Genus Paranthropus (3-1.5 mya)
The "robust" Australopithecines may have been adapted to tougher food, requiring more dental force and a robust skull
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Where are the two main regions of Africa where Australopithecine fossils have been found?
A Volcanic region in East Africa (allows more accurate dating) and the caves of South Africa (best-preserved fossils)
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What significant development in Hominin evolution occurred around 2 million years ago?
The first LARGE BRAINS appeared, opening avenues for more complex behaviour
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What was the earliest known Homo species, and what are some interesting features?
Homo Habilis (2.2-1.8 mya) - specimens found in South and East Africa
Larger Brain and Smaller Teeth than Australopithecus
One of the earliest stone tools - Oldowan technology
Relatively small body size (30kg female, 50kg male), but these estimates may be unreliable due to incomplete skeletons
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Describe the key information given about Homo erectus
Lived from 1.8 mya to around 200,000 years ago - may have existed at the same time as modern humans? (There may even have been some gene mixing between Asian Homo erectus and modern humans)
One "exellent" skeleton of an adolescent was discovered: 5' 6", heavily built
- Long, low skull with broad base
- Prominent brow ridges
- Similar body to modern humans from neck down
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What is meant by "Archaic" Homo sapiens
"Archaic Homo sapiens" refers to many early regional groups of Homo species that resemble modern humans but have some clearly regional traits
Exact speciation is made difficult by gene mixing between Homo groups
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What were the Neanderthals?
Homo neanderthalensis (or possibly Homo sapiens neanderthalensis, as they may be a sub-species) were a very closely related group to modern humans, that lived in Europe and Asia (130,000 - 40,000 years ago)
We know there was significant gene mixing between Neanderthals and modern Humans
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When did the first clearly anatomically modern humans appear, and what are the defining features?
Around 200,000 years ago in Africa - clearly distinct skulls:
- Domed and Rounded Cranial Vault
- Less robust skull than Neanderthals
Some have proposed behavioural differences/advantages between Neanderthals and Homo sapiens (e.g., throwing, long distance running), but these are difficult to infer from anatomy
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What are Homo floresiensis?
A unique Homo species found on the island of Flores in Indonesia, based on one specimen thought to be around 50,000 years old, associated with stone tools
Small brain and body size compared to other Homo species (1m tall, 400 ml brain)
Much debate surrounding their origin, but the leading hypothesis is that they descended from Homo erectus, and showed regression in brain size due to their particular environment not requiring large brains
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What are Homo naledi?
A very newly discovered complete skeleton from the Dinaledi Chamber in South Africa
The skeleton has not yet been dated, and could be anywhere from 10,000 to 3,000,000 years old
Once its age is known, Homo naledi could be very informative, as its anatomy is quite "primitive"/ancestral
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