Lecture Exam 1 Material Flashcards
What group evolved from the pelycosaurs?
Therapsids
What group evolved from the therapsids?
Cynodonts
Following the evolution of endothermic, selection favored what characteristics?
Hair, specialized dentition, evolution of masseter
True or false? An issue with grade-based definitions of mammalian characteristics is that traits may evolve at multiple locations in a phylogeny.
True
The mammaliaformes, or the clade that contains crown group mammals, begin with what group? What is the full order?
Marganucodon -> Docodonts -> Haramiyidans -> Triconodonts -> Multituberculates
How long did Haramiyidans persist?
80 million years
Australosphenids coexisted with modern mammals true or false?
False, multituberculates did.
The diversification of which mammal group coincided with the diversification of angiosperms?
Multituberculates
True or false? The pectoral glide of extant mammals have an inter clavicle
False
What type of posture do mammals exhibit?
Sprawling posture
Which animal group evolved first?
Pelycosaurs
What is the list of “suite of characteristics” defining a mammal
- D-S jaw joint
- Strongly heterodont dentition
- Molar surfaces complex
- Alternate side chewing
- We’ll-developed ear region
- Small
- Axial skeletal characteristics
True or false: early therapsids were endothermic
False
How did the evolution of endothermy begin?
Competition with dinosaurs
Anteaters are considered to be what type of species?
Myrmecophagous
What is viviparity?
Develop of the embryo inside the body of the parent
How many ear ossicles do mammals have?
3
True or false: the dentary of living mammals is the only bone in the mandible
True
What type of teeth do mammals primarily possess?
Diphyodont
True or false: most mammals teeth are homodont
False
The earliest fossils of monotremes can be found in which time period?
Cretaceous
What does the term “syndactyly” refer to?
One sheath of skin for >1 digit
Define gliding, salatorial, fossorial, arboreal, and myrmecophagous species
Gliding: mammals that can glide without energy (sugar glider)
Salatorial: mammal species that move around by leaping or hopping (kangaroo)
Fossorial: mammals that burrow underground (pocket gopher)
Arboreal: mammals that live in trees (koala)
Myrmecophagous: mammals that feed on ants (aardvark)
11 soft anatomy characters
- 4 chamber heart
- Lactation
- Viviparity
- Hair
- Sebaceous sweat glands
- Endothermy
- Annucleate RBC
- Renal artery
- Muscular diaphragm
- Facial muscles
- Dorsal pallium
Function of 4 chamber heart? (Soft anatomy character)
Evolved to completely separate the pulmonary and systematic circulation, more efficient delivery of oxygen
What is lactation?
Nursing young with nilk
What is the importance of hair as a soft anatomy characteristic
Hair evolved to stand up when frightened to appear bigger to predators
What do sebaceous sweat glands do? (Soft anatomy characteristic)
Sebaceous sweat glands move the hair up and keeps mammals cool
What is the importance of endothermy? (Soft anatomy characteristic)
Mammals are able to produce their own heat and regulate body temperature through energy and food
What is the benefit of annucleate RBC’s? (Soft anatomy characteristic)
No nucleus in RBC’s, leaving more room in cells for hemoglobin and oxygen.
What is the importance of the renal artery? (Soft anatomy characteristic)
Materials delivered directly to and from the kidney, direct route to remove waste from body
What is the importance of the muscular diaphragm? (Soft anatomy characteristic)
Muscularized diaphragm allows mammals to run and breath at the same time
What is the importance of facial muscles? (Soft anatomy characteristic)
Good for social interactions, certain expressions are used to communicate
What is the importance of the dorsal pallium? (Soft anatomy characteristic)
Allows for more thoughts and evolutionary opportunities
What are the 8 cranial characters of mammals?
- Double occipital condyle
- Atlas/axis complex
- Tympanic bone
- Three ear ossicles
- Dentary only bone in mandible
- Single external naris
- Secondary palate
- Respiratory turbinates
What is the importance of the double occipital condyle? (Cranial character)
Allows the skull and vertebral column to articulate, permits flexion and extension of head
What is the importance of the atlas/axis complex? (Cranial character)
The atlas can rotate on the axis, allowing mammals to rotate their head
Importance of the tympanic bone? (Cranial character)
Supports ear drum and allows mammals to hear
Importance of three ear ossicles? (Cranial character)
Malleus, incus, and stapes all vibrate against each other to transmit sound
Importance of dentary the only bone in mandible? (Cranial character)
Dentary makes up entire jaw
Importance of single external naris? (Cranial character)
Two nostrils join into one single naris
Importance of secondary palate? (Cranial character)
Separates oral and nasal cavities and allows mammals to eat and breath at same time
Importance of respiratory turbinates? (Cranial character)
Retains water loss while breathing and helps maintain body temperature
What are the 5 dental characters of mammals?
- Diphyodont
- Lack palatial teeth
- Thecodont
- Heterodont
- Multicuspate
What does Diphyodont mean? (Dental character)
Mammal has at most two generations of teeth
What does lacking palatal teeth mean? (Dental character)
Teeth in mammals restricted to margins of the jaw
What does thecodont mean? (Dental character)
Mammals have a tooth socket where they are rooted in mouth
What does heterodont mean? (Dental character)
Each mammal has different types of teeth with different functions
What does multicuspate mean? (Dental character)
The shape of teeth in mammals allows better for grinding food and efficient eating
What are the 4 appendicular skeleton characters?
- Epiphyses
- Calcaneum
- Reduction of elements in limb girdles
- Parasagittal limb posture
What are epiphyses? (Skeleton character)
Bony caps at either end of bone separated from shaft by cartilage
What is the calcaneum? (Skeleton character)
Heel bone that provides mammals leverage for the foot when walking
Importance of reduction of elements in limb girdles? (Skeleton character)
Mammals have better locomotive functions because they lack some shoulder bones that other animals have
Importance of parasagittal limb posture? (Skeleton character)
Limbs rotate under body, leading to parasagittal posture
What is a tetrapod?
A four-legged vertebrate, termed to all land living vertebrates.
What are the three living groups of mammals and which evolved first
Monotremes -> Marsupials (Metatherias) -> Placentals (eutherians)
Difference between anapsid and synapsid?
Anapsids have no temporal fenestra while synapsids have a temporal fenestra behind the orbit
Characteristics and time period of pelycosaurs?
•Large dorsal sail assumed to be thermoregulatory/mate choice
• large animals reaching 3 meters in length
• small temporal fenestra
• no secondary palate
• weakly heterodont teeth
•existed in Carboniferous period and persisted through Permian period
Characteristics and time period of therapsids?
• active and diverse group
• dominant terrestrial life form
• temporal fenestra enlarged
• deeply thecodont teeth
• secondary palate gradually evolving
• lived during middle Permian, most went extinct during Permo-Triassic extinction event
Characteristics and time period of cynodonts?
•advanced therapsids with many transitional fossils
• complete secondary palate
• dentition strongly heterodont
• vast expansion of temporal fenestra
• lived in late Permian and survived extinction event
•radiated after extinction of dinosaurs
What is the key-character approach? What is one defining feature to classify mammals
Dentary and squamosal bones in the jaw joint signifies a mammal while quadrate and articular bones in the jaw joint is non-mammalian.
D-S 👍🏻
Q-A 👎🏻
What is the suite of characters approach? What are the suite of characters for mammals?
A must if characteristics that must be seen to classify as mammal
- D-S jaw joint
- Strongly heterodont dentition
- Molar surfaces complex
- Alternate side chewing
- Well developed ear region
- Small
- Axial skeletal characters
What is grade-based definitions?
Key characters and suite of characters are considered grade-based.
What is the size-Refugium hypothesis?
Early therapsids we’re large ectotherms with high thermal intertia. They were favored and selected for until dinosaurs started to prey on the cydodonts. Selective pressures changed and smaller cynodonts were able to escape predation easier. Cynodonts lost their thermal inertia characteristics leading to selection of groups that could produce their own heat. This led to evolution of endothermy in mammals.
Implications of evolution of endothermy
- Energy requirements: endothermy required 10x energy as similar sized extitherm, led to selection favoring efficiency in food processing
- Behavioral implication: since endothermy can generate own heat, they were active at cold temperatures, permitting nocturnality and selecting upon species with hair for insulation
True or false: stable clade-based definition includes the morganucodontids as mammal, whereas others consider them mammaliaformes
True
Characteristics of morganucodontids and time period?
• small species
• skull had large nasal cavity
• well-developed ear region
• insectivorous
• dentary greatly expanded
Characteristics of docodonts and time period they lived?
• lived in middle Jurassic
• hyoid apparatus
Characteristics of haramiyidans and time period they lived?
• first appeared 220 mya and persisted for 80
• chisel-like incisors and gap between that and cheek teeth
• herbivorous
• single ear ossicle
• diverse, arboreal, squirrel like
Characteristics of triconodonts and time period?
• teeth similar to morganucodontids
• mammalian pectoral girdle
• sprawling posture
• mosaic evolution
• lived between Triassic and Cretaceous period
Characteristics of multituberculates and time period?
• rodents of Mesozoic
• diverse and persistent group
• coexisted with some modern mammals
• dentition included chisel like incisors and complex grinding molars
• upper Jurassic and Cretaceous-tertiary
Characteristics of montremes?
Reproductive:
• oviparous
• eggs have huge amount of yolk
• shelled eggs
• mammary glands have separate openings
• no nipples
Derived characteristics:
• leathery bill/beak
• venom ducts
• raspy pads instead of teeth
What is the single dispersal hypothesis
Marsupials dispersed only once, after which Pangea separated, as opposed to dispersing to different areas multiple times
