Week 1: Evolution & Origin of Mammals

Members of Phylum Chordata all have a ____________.

skulls without holes (solid sheet of bone)

Avocado analogy for a turtle (anapsid skull)

• _________ = avocado seed

• _____ ______ = avocado skin

Anapsid skulls lack room for ________ flexion

• this puts a constraint on how hard you can ____

Mammals don’t have a _____ shield.

Natural selection favored ________ of the skull,

followed by development of holes/fenestrae in the _______ _______

• this favors the ability to get ______ faster

Natural selection _____ the bone where _____ attachment was not needed and allowed for _________ flexion.

skulls with 2 holes which includes all reptiles other than parareptilia

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

skull that independently created a single hole in the temporal shield

2 main groups of Synapsida

Pelycosaurs

• not _____________

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

• once called mammal-like ______

Order Therapsida

• very _______

• derived from advanced ________

• most fairly _____

• included _ suborders

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

less advanced

more advanced

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

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

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

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

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

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

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

What articulation is present in true mammals?

How many middle ear bones do mammals have?

What bone was the incus before it became the incus?

Which is the innermost middle ear bone?

Which is the middle middle ear bone?

Which is the outermost inner ear bone

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

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

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

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

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

The DMME has

• a single __________

• all middle ear bones __________ in size

• highly ________

• no contact with _________

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

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

What was the main issue with the anapsid skull?

The synapsid skull allows greater flexion of which muscle?

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

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

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 ______ ________

Mammals have lost ribs on which 2 types of vertebrae?

Mammals rely more on ______ than muscle to stand up.

________ spines developed on mammals.

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

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

What is the primitive phalangeal formula for mammals?

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

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

Maxilloturbinal bones are only in ________ animals

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

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

Which occurred first: mammals or maxilloturbinal ridges?

When did full endothermy originate?

Primary function of hair

2 requirements of lactation

• secondary ____________

• ___________ dentition

Lactation infers a close….

Lactation likely developed by the end of the ____________.

Is mammary tissue the same or different across mammals?

Synapsids became ________ which became mammals

Triassic

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

• big inland _____

• humid or arid?

• lots of _______ across the land of the planet

Jurassic

• __________ splits into N & S supercontinents

• Sierra Nevada _________ begins

• climate is warm or cold, moist or arid?

• great diversification of mammals due to ____________ _____________

Cretaceous

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

• climatic ______

• _________ & _____ create food for mammals

• lots of __________ activity

• ______________ _________ Revolution in which multiple groups are diversified

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

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

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

includes all true Mammalia plus stem groups

Almost all mesozoic mammaliaform clades were

• relatively ______ lived

• clustered in several episodes of accelerated ________________

• Most orders are ____

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

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

Eutriconodonta

• _ cusps arranged linearly on teeth

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

• _______ → cusps were good at chopping meat

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

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