MAMMALS!
MAMMALIA:
5,500 living species. Occur on all continents and in all oceans.
Size: range from 1.3g (shrew) to 180 metric tons and 108 feet (blue whale)
Ecology: mammals play a dominant role in terrestrial ecosystem as herbivores and predators.
Mammals dominate in almost all terrestrial ecosystems, except distant islands (e.g. Galapagos)
that they have been unable to reach.
Marine: mammals are also ecologically important in marine ecosystems – toothed whales and
baleen whales are major predators in marine food webs.
Elaborate parental care systems: all mammals care for and provide nourishment for their
offspring.
Social lives: mammals have elaborate social systems – herds in animals such as elephants,
horses, wildebeest. Cooperative hunting and foraging groups in carnivores and primates.
Intelligence: mammals are the most intelligent of all animals. High intelligence makes them
adaptable – and sometimes allows them to work cooperatively, communicate and use tools.
DERIVED FEATURES (SYNAPOMORPHIES) OF MAMMALS:
, Dentition: Primitive tetrapods (frogs, lizards, alligators, etc.) have unspecialized dentition
• teeth are pointy cones, to spear prey, not to chew it, with a single cusp and single root
• lots of teeth
• little difference between front and back teeth
• no tight interlocking (occlusion) between uppers and lowers
• endless supply of teeth- worn out, shed, replaced. Like shoes, continuously replaced by larger
ones as animal grows in size
Mammals have advanced dentition
• multiple cusps, multiple roots
• few teeth
• differentiation into incisors, canines, premolars, molars
• upper and lower teeth interlock (occlude) with upper molar cusp (trigonid) fitting into a
depression (talonid basin) in a mortar-and-pestle action
• front teeth are replaced once (milk teeth are replaced by adult dentition), molars are never
replaced
Nocturnality:
• Ancestral amniotes are lizard-like: large, well-developed eyes with color vision, weak senses of
smell and hearing (e.g., lizards, birds). Visually oriented, diurnal predators
• Mammals visual system is modified. Most mammals have lost color-sensitive cone cells from
the retina and have only rod cells, which are highly sensitive to all wavelengths of light, at the
expense of being able to discriminate color (bulls cannot see red, e.g.)
• Other systems are elaborated:
A) Vibrissae. Enlarged hairs on snout and face to detect objects/prey using tactile cues, air
movements (in therians, but not monotremes)
B) Ears. Extremely sensitive hearing, made possible by sophisticated middle ear consisting
of malleus/incus/stapes bones, and a fleshy outer ear in therian mammals. Elaborated
into sonar by bats/whales.
C) Nose. Elaborate olfactory system to detect prey- and other members of the species
Mammals are adapted for operating in low light conditions
Advanced primates, including humans, are unusual in having large eyes, color vision, poorer
sense of smell/hearing)
Warm Blood: Primitive amniotes were cold-blooded.
MAMMALIA:
5,500 living species. Occur on all continents and in all oceans.
Size: range from 1.3g (shrew) to 180 metric tons and 108 feet (blue whale)
Ecology: mammals play a dominant role in terrestrial ecosystem as herbivores and predators.
Mammals dominate in almost all terrestrial ecosystems, except distant islands (e.g. Galapagos)
that they have been unable to reach.
Marine: mammals are also ecologically important in marine ecosystems – toothed whales and
baleen whales are major predators in marine food webs.
Elaborate parental care systems: all mammals care for and provide nourishment for their
offspring.
Social lives: mammals have elaborate social systems – herds in animals such as elephants,
horses, wildebeest. Cooperative hunting and foraging groups in carnivores and primates.
Intelligence: mammals are the most intelligent of all animals. High intelligence makes them
adaptable – and sometimes allows them to work cooperatively, communicate and use tools.
DERIVED FEATURES (SYNAPOMORPHIES) OF MAMMALS:
, Dentition: Primitive tetrapods (frogs, lizards, alligators, etc.) have unspecialized dentition
• teeth are pointy cones, to spear prey, not to chew it, with a single cusp and single root
• lots of teeth
• little difference between front and back teeth
• no tight interlocking (occlusion) between uppers and lowers
• endless supply of teeth- worn out, shed, replaced. Like shoes, continuously replaced by larger
ones as animal grows in size
Mammals have advanced dentition
• multiple cusps, multiple roots
• few teeth
• differentiation into incisors, canines, premolars, molars
• upper and lower teeth interlock (occlude) with upper molar cusp (trigonid) fitting into a
depression (talonid basin) in a mortar-and-pestle action
• front teeth are replaced once (milk teeth are replaced by adult dentition), molars are never
replaced
Nocturnality:
• Ancestral amniotes are lizard-like: large, well-developed eyes with color vision, weak senses of
smell and hearing (e.g., lizards, birds). Visually oriented, diurnal predators
• Mammals visual system is modified. Most mammals have lost color-sensitive cone cells from
the retina and have only rod cells, which are highly sensitive to all wavelengths of light, at the
expense of being able to discriminate color (bulls cannot see red, e.g.)
• Other systems are elaborated:
A) Vibrissae. Enlarged hairs on snout and face to detect objects/prey using tactile cues, air
movements (in therians, but not monotremes)
B) Ears. Extremely sensitive hearing, made possible by sophisticated middle ear consisting
of malleus/incus/stapes bones, and a fleshy outer ear in therian mammals. Elaborated
into sonar by bats/whales.
C) Nose. Elaborate olfactory system to detect prey- and other members of the species
Mammals are adapted for operating in low light conditions
Advanced primates, including humans, are unusual in having large eyes, color vision, poorer
sense of smell/hearing)
Warm Blood: Primitive amniotes were cold-blooded.
