Placentalia: 3 molars, submolariform last premolar, triangular cusp pattern with no stylar
Eomania: 125MYA, well preserved (pelt impression fossilized). Has 3 molars, primitive
placental dental formula (I5/4, C1/1, PM 5/5, M3/3), with a premolar th
Many characters found in Therapsids are not informative.
Each Therapsid lineage had different supporting characters (yet still a small number),
indicating that rapid diversification of the lineages occurred from a Biarmosuchus-grade
A single ma
Two major groups of amniotes, both originated in the upper Carboniferous:
o Early synapsids
Has a temporal opening at the back of the skull, behind the orbit (eye
opening) will never be lost in mammals.
o Protothyrididae (e.g. Hylonomu
Undergraduate Awards for Summer Research
Summer Research Awards
GPA 3.4 or higher
15 The Rise of Modern Orders of Placentals (Laurasiatheria III)
Onychonycteris (The most primitive known bat)
Claws on all five digits, fully evolved wing.
But small, non-echolocating cochlea.
o Molecular phyl
10 Interrelationships of Living Placentals and Modern Mammals
Interrelationships of living placentals
5080 species, 21 orders
Classification at the supra-ordinal level is historically unstable
o Phylogeny is based on morphology (molecular
11 Monotremata and Marsupialia: Living Mammals
o Low, broad skull; reduced dentition, edentulous as adults.
o Limbs modified for swimming or digging; secondary sprawling gait.
o Hindlimb with horny spur connected to poison gla
12 Modern Orders of Placentals: Xenarthra and Afrotheria
o Accessory articulations on the vertebrae in the lumbar region (articulation on side
of vertebrae makes entire structure more coherent and stronger).
o Incisors and canines ar
What are the monotremes, and what is their relationship to the therians?
The Greatest Mystery
Morganucodon-monotremes relationship: shared dichotomy
o 2-3 transverse ridges on monotreme molariform is thought to be derived from the
3 cusps of the Morganu
9 The Radiation of Placentals
The Dromiciops Problem
1. Radiation of Australidelphians, including microbiotheres, occurred in Australia.
2. You would want to look for evidence of this more recent migration in Antartica.
3. To prove this hypothesis, we wou
7 - The Diversity and Biology of Extinct Mesozoic Mammal Lineages
All living species of mammals are descended from 3 major evolutionary lineages:
o Eutherians (i.e. placentals)
o Metatherians (i.e. marsupials)
o Australosphenida (i.e. monotremes)
6 Mammalian Advantages of Endothermy
1. Elevated BMR
Basal metabolic rate is not directly related to body size.
It is 6-10x higher than in ectotherms.
2. Elevated body temperature
Does not have any direct function
Ectothermic reptiles can also raise t
Carnivora: found worldwide, primarily meat eaters (some omnivorous, piscivorous, frugivores,
myremecophages), with a wide variety of niches (arboreal, scansorial, cursorial, fossorial,
aquatic). Carnivorans is a term describing diet, not cladistics.
Hylobatidae (siamang and gibbons), hominidae (great apes). 8 genera, 21 species.
Characterized by large bodies, absence of a tail, short trunk, large brain (relatively speaking).
1st representative = Proconsul. Quadrupedal, mayb
Monotremata: 3 genera, all in Australasia
Skeletal features: epipubic bone present, primitive small lumbar ribs. Procoracoid,
coracoid, and interclavicle all present (lost in all other mammals). Primitive sprawling
posture (actually secondarily re-attaine
Adaptaive radiation in S. America - most primitive living placental group. ACcessory articulation on
lumbar vertebrae (strengthening) - sometimes thoracic too. No incisors or canines, cheek teeth
reduced or lost, open-rooted with little or no ena
Chiroptera. the 2nd most diverse group - 202 genera, 1116 species.
Originated in the early Eocene, found in North America, Europe, Australia, almost identical to
modern bats, except for a few primitive characteristics like the retention of claw on digit I
Glires = Rodentia + Lagomorpha
Large, ever-growing procumbent incisors. Enamel on anterior - the rest of the tooth gets worn down,
but hard enamel maintains a chisel shape. Diastema = no canines. Cheek teeth evolved for herbivory.
BIOL 463 - Mammalian Evolution with Virginie Millien
Term paper (25%), final lab exam (30%), final exam (40%), participation (5%)
Term paper: anything on mammalian evolution. Title + 2 relevant references due
Jan 17, final draft due March 12.
Brief history of mammals
300MYA: beginning of mammal-like reptiles radiation
210MYA: first true mammal, flourishing during Mesozoic
65MYA: explosion during the Tertiary after KT extinction
20,000YA: most large mammals went extinct
Gradual climate change increased aridity, increasing seed plant density. Therapsids
more suited to changes: they had greater mobility and agility, had a shift in metabolism they edged out the pelycosaurs by competitive exclusion.
Appeared in the late Permian, radiated in the Triassic worldwide, with 3 grades:
Typical skull characters: enlarged temporal fenestra, sagittal crest for temporalis muscle
attachment, quadrate and articulars are reduced. Dentary is much larger (
Eucynodontia: historically, believed that carnivorous mammals descended from cynodonts, and a
herbivorous group convergently evolved mammal-ness
There has been conflict over positions of Cynognathidae (basal to all, or sister t
Evolution of encephalization quotient in mammals - calculated via endocasts. Brain size increases
are probably a result of sensory needs. Evidenced by the fact that olfactory bulb enlargement
preceded neocortex enlargement.
Physiology and temperature
Stonesfield jaw: first evidence of mammals existing in the age of reptiles. Prevailing views:
mammals were dominated taxonomically and numerically. All descendents of 3 lineages: eutherians,
2 traditional views, based on