Mammals Flashcards
Synapsids
When did mammals originate?
Palaeozoic
Permian
(Pelycosaurs and therapsids)
When did mammals radiate
Triassic
When was the tertiary radiation of mammals?
Cenozoic
Tertiary
When was the megafaunal extinction?
Cenozoic
Quaternary
What was the megafaunal extinction?
The end of the Pleistocene which was distinguished by extinction of many large mammals such as mammoths, mastodons and ground sloths
Pelycosaurs
Late Paleozoic synapsids, excluding the therapsids and their descendants.
What is the earliest non mammalian synapsid (Pelycosaur)
Archeothryis
Non mammalian synapsid
Pelycosaur, therapsids, cynodont therapsids
Mammals
Monotremes
Marsupials
Eutherians
What is the defining feature of the synapsids
The temporal fenestra
Therapsids
Increased metabolic rate
Flexible neck
Teeth differentiation
Found mainly in Gondwana
ORIGINS
Therapsids
Pelycosaurs
Pelycosaurs
No evidence of metabolic rate or high locomotor capacity
Generalised amniotes
Found mainly in Laurasia
Pelycosaurs are more primitive than
Therapsids
When did therapsids appear in the fossil record?
Late Permian
250-290mya
What is the temporal fenestra
Allows the expansion of jaw musculature beyond the adductor chamber
Accommodâtes a larger bite
Features of the earliest Mesozoic mammals
Tiny Lactation and suckling evolution Hair Special Harderian gland - insulates fur Derived features of the skull reflecting larger brain and inner ear
When did mammals diversify into larger, more specialised forms?
After the extinction of dinosaurs - Cenozoic tertiary period
LSRLHBE
Mammalian characteristics
Locomotion (improved) Sensory systems (improved) Reproduction Lactation Hair High blood pressure, o2 uptake, metabolic rate, water regulation (loop of Henle) Endothermic
What does lactation allow?
Reproduction at any time of the year
How has lactation increased mammalian diversity?
It gave rise to differentiation of teeth. Mammals diversified to exploit a greater range of food and feeding strategies.
Diphyodonty
Mammals with two successive sets of teeth: deciduous set and then the permanent set
What does lactation mean for newborn mammals
They do not need teeth