Week 1: Evolution & Origin of Mammals

Members of Phylum Chordata all have a ____________.

notochord

skulls without holes (solid sheet of bone)

anapsid

Avocado analogy for a turtle (anapsid skull)

• _________ = avocado seed

• _____ ______ = avocado skin

• braincase

• temporal shield

Anapsid skulls lack room for ________ flexion

* this puts a constraint on how hard you can ____

muscular

* chew

Mammals don’t have a _____ shield.

temporal

Natural selection favored ________ of the skull,

followed by development of holes/fenestrae in the _______ _______

* this favors the ability to get ______ faster

thinning, temporal shield

* food

\

Natural selection _____ __the bone where__ _____ __attachment was not needed and allowed for__ _________ flexion.

lightened, muscle, muscle

skulls with 2 holes which includes all reptiles other than parareptilia

diapsid

A diapsid skull is one way of dealing with the need for stronger _________ muscles.

chewing

skull that independently created a single hole in the temporal shield

synapsid

2 main groups of Synapsida

Pelycosaurs & Order Therapsida

Pelycosaurs

• not _____________

• 1st group to be completely adapted to an ____ environment

• once called mammal-like ______

• monophyletic

• arid

• reptiles

Order Therapsida

• very _______

• derived from advanced ________

• most fairly _____

• included _ suborders

• diverse

• Pelycosaurs

• small

• 5

Early synapsids had a ______ hole/fenestra in the temporal shield

small

less advanced

pleisiomorphic

more advanced

apomorphic

Major changes in the transition from amniotes to synapsida to mammals

• secondary palate has _ bones for separation between oral & nasal cavity

• simplified ________ from expansion of the dentary

• strongly ____________ dentition

• ___________ bone to articulate the jaw onto the skull

• major changes in __________ ear

• 3

• mandible

• heterodont

• articular bone

• middle

How did the angular middle ear bone change from fish to reptiles to mammals?

angular in fish

angular in reptiles

tympanic ring in mammals

How did the articular middle ear bone change from fish to reptiles to mammals?

articular in fish

articular in reptiles

malleus in mammals

How did the quadrate middle ear bone change from fish to reptiles to mammals?

quadrate in fish

quadrate in reptiles

incus in mammals

How did the hyomandibular middle ear bone change from fish to reptiles to mammals?

hyomadibular in fish

stapes in reptiles

stapes in mammals

What is the articulation between the jaw & the skull called?

articular-quadrate articulation

The ear is connected to the ___ which helps increase hearing.

jaw

What articulation is present in true mammals?

dentary-squamosal articulation

How many middle ear bones do mammals have?

3

What bone was the incus before it became the incus?

quadrate

Which is the innermost middle ear bone?

stapes

Which is the middle middle ear bone?

incus

Which is the outermost inner ear bone

malleus

How many stages are there in the evolution of modern mammalian middle ears?

3

The first stage of the evolution of modern mammalian middle ears involved the mandibular middle ear of _____________.

cynodonts

In the MMEC, the middle ear bones remain attached to the ____________.

mandible

The second stage in the evolution of the modern mammalian middle ear is the ___________ mammalian middle ear.

partial

The third and final stage in the evolution of the modern mammalian middle ear is the ___________ mammalian middle ear.

definitive

The DMME has

• a single __________

• all middle ear bones __________ in size

• highly ________

• no contact with _________

• dentary

• reduced

• sensitive

• mandible

Did the definitive mammalian middle ear evolve once, or was there convergence?

convergence

temporal shield with braincase inside and mandibles connected by temporal muscle, pleisiomorphic skull condition

anapsid skull

What was the main issue with the anapsid skull?

the need for more room to flex

The synapsid skull allows greater flexion of which muscle?

temporal

Which 2 muscles does the synapsid skull lead to the temporal cleaving into?

upper temporal muscle & lower masseter muscle

The cleavage of the temporal muscle into 2 separate muscles allows more flexible ________ because the jaw can move in different directions.

chewing

In a true mammal,

• the temporal shield is ____

• the temporal muscle is only on the _________

• the masseter muscle is attached to the remains of the ______ ________

• gone

• braincase

  • temporal shield

Mammals have lost ribs on which 2 types of vertebrae?

cervical & lumbar

Mammals rely more on ______ than muscle to stand up.

bone

________ spines developed on mammals.

Neural/dorsal

Modified limb girdles in mammals

• ______ of elements to reduce weak spots

• ilium directed __________

  • allows it to latch onto the spine & increase the _______ of the spine connecting to the hind limb system

• fusion

• anteriorly

  • stability

________ spine developed in mammals to increase the bone area for more muscular attachment.

scapular

What is the primitive phalangeal formula for mammals?

2-3-3-3-3

______ bones, don’t fossilize easily because they are very fragile, but they attach onto the ridge on the maxillary bone that fossilizes.

Turbinal

If you can see where the _______________ bones would have attached, you know that the animal is an endotherm.

maxilloturbinal

Maxilloturbinal bones are only in ________ animals

endothermic

__________ bones are right under nasal bones in reptiles, birds, & mammals.

Nasoturbinal

1st presence of maxilloturbinal ridges can be traced back to the Late ______________ and early synapsids.

Permian

Which occurred first: mammals or maxilloturbinal ridges?

maxilloturbinal ridges

When did full endothermy originate?

early Triassic

Primary function of hair

to retain heat

2 requirements of lactation

• secondary ____________

• ___________ dentition

• palate

• deciduous

Lactation infers a close….

mother-offspring bond

Lactation likely developed by the end of the ____________.

Triassic

Is mammary tissue the same or different across mammals?

essentially identical across ALL mammals

Synapsids became ________ which became mammals

cynodonts

Triassic

• _____ vertebrates were ecologically replaced by precursors of dinos & true mammals

• big inland _____

• humid or arid?

• lots of _______ across the land of the planet

• synapsid

• seas

• humid

• connection

Jurassic

• __________ splits into N & S supercontinents

• Sierra Nevada _________ begins

• climate is warm or cold, moist or arid?

• great diversification of mammals due to ____________ _____________

• Pangaea

• uplift

• warm & moist

• geographic isolation

Cretaceous

• both supercontinents start to ____________ __ → lots of continental drift

• climatic ______

• _________ & _____ create food for mammals

• lots of __________ activity

• ______________ _________ Revolution in which multiple groups are diversified

• break-up

• cooling

• angiosperms & insects

• volcanic

• Cretaceous Terrrestrial Revolution (KTR)

Evolution is ____________. There will always be intermediates that are hard to define as one group or another.

gradual

crown group of mammals which refers to the most common ancestors of living Monotremata & Eutheria + Theria, and all of their descendants

Mammalia

word that refers to lineages possessing many but not all mammal characteristics

includes all true Mammalia plus stem groups

“Mammaliforms”

Almost all mesozoic mammaliaform clades were

• relatively ______ lived

• clustered in several episodes of accelerated ________________

• Most orders are ____

• short

• diversification

• gone

Monotremata

• _______ Mesozoic record

• many ____ features

  • ______ ribs (no other mammals have these)

  • _______-like shoulder girdle

  • _______ forelimb posture

  • skull retains _________ bone

  • scapula lacks _______ (all other mammals have this)

  • cochlea is ____,not coiled

• spotty

• primitive

  • cervical

  • Therapsid

  • sprawling

  • septomaxilla

  • spine

  • bent

__________ seems to be a separate radiation from all “Therian” mammals.

Monotremata

Eutriconodonta

• _ cusps arranged linearly on teeth

• among the best or worst represented in the fossil record?

• _______ → cusps were good at chopping meat

• 3

• best

• predatory

Multituberculata

• _______ -like in appearance

• 1st mammalian ___________

  • teeth for _______ things

• survived ___ extinction

• last premolar with characteristic ______ edge

• first appear in late _______

• went extinct in _______ possibly thru competition with Therian mammals

• rodent

• herbivores

  • grinding

• KPG

• shearing

• Triassic

• Oligocene

Dryolestoidea

• advanced ______ with an array of types

• development of ______ process on lower jaw

  • more _________ muscle attachment

• _________________ arrangement of cusps which was more elaborate than in earlier groups

• lower molar has the ___________

• fancy teeth allow for a __________ diet

  • led to the __________ molar that characterizes many primitive mammal groups

• teeth

• angular

  • masseter

• triangular

• talonid

• diverse

  • tribosphenic