Mammalian Origins And Characteristics Flashcards
How many mammal and bird species are there?
Mammal: around 4,500
Birds: 10,000
What are the characteristics that define mammals?
They give birth to live young
They produce milk from mammary glands
They have hair of some description
What is an amniote?
A tetrapod vertebrate with a membrane, water-proof, shelled egg
What is anapsid, synapsid and diapsid?
Anapsid: no temporal fenestra/no hole in the skull
Synapsid: single fenestra/ one hole (humans)
Diapsid: double fenestra/two holes in the skull
What is a cladogram?
A branching diagram showing the cladistic relationship between a number of species
What do the nodes in a cladogram define?
The synapomorphies= the shared derived character states
What was the first grouping of mammal-like reptiles called?
Pelycosaurs
When were Pelycosaurs abundant?
The Late Carboniferous/early Permian (320-265mya)
What were the characteristics of Pelycosaurs?
Parasagittal gait compared to other reptiles- different walking style
Primitive heterodonty (different teeth)
Relatively long limbed
Elongated neural spines on the vertebrae to help with weight bearing
Give an example of a dinosaur with neural spines?
Dimetrodon limbatus
Larger of the species and were top predators
Carnivores
How did the neural spines act as thermoregulation?
Allowed the organism to warm up quickly in the morning
Large SA to allow heat to dissipate easily
May have an angled sail away from the sun to cool down or alter blood flow to keep warm at night
When did therapsids occur and what characteristics did they have?
Late Permian before break up of Pangea
Longer lumber, more upright stance, rib reduction and perhaps had a diaphragm
What are the characteristics of Cynognathus crateronotus?
Very large and powerful head
Incisors, canines and cheek teeth for a carnivorous diet
Likely to be warm blooded
Consumed herbivorous reptile therapsids
What are the characteristics of cynodonts?
Reduced rib structure (loss of lumbar ribs)
Secondary palate- allows animal to breathe while eating and could be a heat exchanger
Greater heterodonty
Zygomatic arch to give more force to their bite
What are some defining nodes (synapomorphies) in the cladogram for mammals?
Enlarged dentary- bigger lower jaw
Prismatic enamel tooth surface- longer wearing teeth
Dentary squamosal jaw articulation
Tribosphenic cheek teeth
Placenta
