Lab 8: Amniotes – Reptiles, Birds, and Mammals

What phylogenetic relationship do mammals, reptiles, birds, and their extinct relatives have

Monophyletic

What is the most notable characteristic in the amniotes taxon

Amniotic egg

What do the various structures associated with the amniotic egg allow the egg to do

Laid on dry land, protect and nourish embryo

The outermost layer of the egg of amniotes

Shell

What are the two textures that the amniote egg can have

Soft and leathery, hard and mineralized

What is the hard egg a synapomorphy of

Archosaurs (crocs and birds)

What reptiles possess the softer, leathery shell

Other reptiles

What was the texture of the eggs of early amniotes

Less mineralized

What does the shell protect the egg from

Desiccation, abrasion, friction

What are the four membranes in the egg that facilitate nutrition, water, and waste removal

Chorion, amnion, yolk sac, allantois

The outermost layer of membrane within the shell

Chorion

The membrane which helps to minimize water loss from the developing embryo

Chorion (def)

Second outermost membrane within the shell

Amnion, amniotic membrane

The membrane which originates from the ventral aspect of the embryo, encloses the embryo, and encloses the amniotic fluid

Amnion, amniotic membrane (def)

The second innermost membrane within the shell

Yolk sac

The membrane which contains the yolk, the nutritive substance that will provide the nutritional requirements of the developing embryo

Yolk sac (def)

The innermost membrane within the shell

Allantois

How does the allantois develop

Posterior to the ventral origin of yolk sac

First function of the allantois

Stores nitrogenous wastes from embryo as uric acid

Second function of the allantois

Gas exchange for embryo

What is the exchange of O2 and CO2 carried out by in the egg

Highly vascularized chorioallantoic membrane

Fused area of the chorion and the allantois

Chorioallantoic membrane

The three skull types found in Amniota

Synapsids, anapsid, diapsid

The group which diverged from the rest of the Amniota in the middle Pennsylvanian, including mammals and their extinct ancestors

Synapsids

The single opening behind the eye

Temporal fenestra

How many temporal fenestra do synapsids have

One

Which skull types are in the Saurapsids

Anapsid, diapsid

What animals does the Saurapsids include

Reptiles, birds, dinosaurs

Birds and most modern reptiles are…

Diapsids

How many temporal fenestrae do diapsids have

Two

The remaining reptiles are…

Anapsid

What is the only remaining anapsid reptile

Turtles

What group is sister to crocodilia

Testudines

Most non-mammalian vertebrates have what kind of dentition

Homodont

Dentition where tooth morphology does not differ

Homodont (def)

Dentition where teeth differ morphologically

Heterodont (def)

Dentition where animals retain their teeth throughout their lifetime

Monophyodonty

Examples of animals with monophyodonty

Toothed whales, dolphins

What are the two types of monophyodonty that can be experienced

Diphyodonty, polyphyodonty

Monophyodonty which have two successive sets of teeth

Diphyodonty (mammals)

Monophyodonty which teeth are continuously replaced throughout their lifetime

Polyphyodonty (reptiles)

The most basal group of extant amniotes are…

Mammals

Mammals are descendants to what ancestor

Cynodont

What plesiomorphic characteristics does Class Mammalia possess

Hair, sebaceous glands, synapsid skull, diphyodont teeth, endothermy

How did the endothermy in Class Mammalia evolve compared to the endothermy in dinosaurs and birds

Independently

How did hair evolve in Class Mammalia

New epidermal structure

Autapomorphies in Class Mammalia

Mammary glands, milk

Mode of reproduction in Class Mammalia

Viviparous

Exception to viviparity in Class Mammalia

Extant/extinct monotremes

Subclasses within Class Mammalia

Prototheria, theria

Subclasses Prototheria and Theria are in Class…

Class Mammalia

What is the relationship between Subclasses Prototheria and Theria

Sister groups

Order within Subclass Prototheria

Monotremata

Order Monotremata is in Subclass…

Subclass Prototheria

How do monotremes (Order Monotremata) have their babies

Egg laying

How do monotremes (Class Monotremata) feed their young if they have no nipples

Milk pooling on the skin

Common name of the extant species of monotremes (Order Monotremata)

Platypus, echidna

How many extant species of monotremes (Order Monotremata) are there

One platypus, four echidna

Infraclasses within Subclass Theria

Metatheria, eutheria

Infraclasses Metatheria and Eutheria are in Subclass…

Subclass Theria

Infraclass Metatheria comprises a single extant order, Order…

Order Marsupalia

Common name of Order Marsupalia

Kangaroos, opossums, koalas

Kangaroos, opossums, and koalas are in Order…

Order Marsupalia

Birth cycle in Order Marsupalia

Live birth > underdeveloped embryo > complete development in pouch

Is the placenta developed or underdeveloped in Order Marsupalia

Underdeveloped

What does the unfused female reproductive organ result in, in Order Marsupalia

Two vaginas, two uteri

What type of male reproductive organ does Order Marsupalia have

Bifurcated penis

Location of scrotum in group lagomorphs of Eutherians

Anterior to penis

Infraclass Eutheria is also referred to as…

“placental mammals”

How developed is the placenta in Infraclass Eutheria

Well developed

What does the placenta in Infraclass Eutheria provide

Exchange of gases, nutrients, nitrogenous wastes

How are gasses, nutrients, and nitrogenous wastes exchanged in the placenta in Infraclass Eutheria

Diffusion between maternal and embryonic capillary beds

What does the umbilical cord carry between the embryo and the placenta

Embryonic blood

Point of attachment for the umbilical cord

Bellybutton, umbilicus

What two lines is Amniota represented by

Synapsids, sauropsids

What are the five groups within the modern reptile group

Squamates, tuataras, turtles, crocodilians, birds

What is the relationship of the group that includes the traditional reptiles

Paraphyletic

Common characteristics that reptiles possess

Oviparity, dry/scaly skin, ectothermy

Origin of scales on reptiles

Epidermal

Purpose of scales on reptiles

Keratinized, barrier, protection, prevent water loss

When most reptiles do not produce enough metabolic heat to maintain a constant body temperature

Ectodermic (def)

What is the main nitrogenous waste excreted by reptiles

Uric acid

How did uric acid in reptiles evolve

Autapomorphy, cleidoic nature of amniotic egg

Why is uric acid the better choice for animals with cleidoic (amniotic) eggs

Low toxicity, reduced dilution

Infraclasses within Class Reptilia

Lepidosauromorpha, archosauromorpha

Infraclasses Lepidosauromorpha and Archosauromorpha are in Class…

Class Reptilia

Orders within Infraclass Lepidosauromorpha

Sphenodonta, squamata

Orders Sphenodonta and Squamata are in Infraclass…

Infraclass Lepidosauromorpha

What are the two sister groups in lepidosaurs

Rhynchocephalians, squamates

The rhynchocephalians include…

Two extant species of tuataras

Where are tuataras found

New Zealand

Tuataras possess a well developed…

Parapineal

Do tuataras have lower or higher body temperatures

Lower

Common names of Order Squamata

Lizards, snakes, amphisbaenians

Lizards, snakes, and amphisbaenians are in Order…

Order Squamata

Common name of amphisbaenians

Worm lizards

Most common characteristic of Order Squamata

Moveable lower jaw

What does the position of the quadrate bone in Order Squamata allow for…

Double hinge in jaw, forwards and backwards

Degree that snakes can open their jaws to

150

What type of dentition does Order Squamata possess

Homodont