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1

Amniote synapomorphy

amniotic egg (clade-defining)

2

Amniote monophyletic or paraphyletic?

monophyletic clade

3

Amniotic egg "synapomorphies" (3)

(3 new membranes)
- Amnion
- Allantois
- Chorion

4

Amnion

surrounds developing embryo & holds it in amniotic fluid ("enclosing the pond")

5

Allantois

repository for nitrogenous waste

6

Chorion

gas exchange (together with Allantois)

7

Other derived characteristics of Amniotes (8)

- keratinized skin (resistant to water loss)
- keratinized epidermal scales in reptiles (dermal in bony fishes) (epidermal + dermal in cartilaginous fishes)
- hardened nails or claws
- ventilation/respiration via lungs filled by thoracic expansion (expansion of rib cage produces (-) pressure)
- no larvae or metamorphosis
- no gills
- loss of lateral line system
- internal fertilization (most w/ intermittent organ)

8

Amniotes originated in

early carboniferous

9

3 major groups of amniotes by

later carboniferous (based on skull morphology)
- Anapsida
- Diapsida
- Synapsida

10

Anapsida =

first amniotes! (extinct?)

11

Anapsida have no

no temporal skull opening behind orbits (completely roofed by dermal skull bones)

12

Turtles historically considered

Anapsids

13

Turtles now considered

derived Diapsids based on new data
- t.f. no extant anapsids

14

Diapsids have

2 temporal skull openings behind orbits (separated by bony arch)

15

Diapsids represented today by

all living reptiles & birds

16

Diapsida =

Testudines, Lepidosauria, Archosauria

17

Testudines (turtles) monophyletic or paraphyletic?

monophyletic clade

18

Lepidosauria monophyletic or paraphyletic?

monophyletic clade

19

Archosauria monophyletic or paraphyletic?

monophyletic clade

20

Testudines girdle located

w/in rib cage

21

Testudines lack

teeth (jaws w/ keratinized plates)

22

Testudines reproduction

oviparous & bury eggs in nests

23

Testudines sex det

Incubation Temperature Dependent Sex Determination

24

What groups exhibit Temperature Dependent Sex Determination?

all turtles, crocodilians, some snakes & lizards

25

Temperature Dependent Sex Determination:

high temp = female
low temp = male
~29 degree switch threshold

26

Current phylogenetic position of Turtles?

- closer to derived diapsids:
DNA evidence says closer to Archosaurs (crocs & birds)
Morphological evidence says closer to Lepidosaurs (snakes & lizards)

27

Transitional turtle

Odontochelys semitestacea ("toothed turtle with half shell")
- most basal turtle
- teeth!
- only bottom half of shell present

28

Lepidosauria is w/in

Diapsida

29

Testudines is w/in

Diapsida (current)

30

Rhynchocephalia is w/in

Lepidosauria t.f. Diapsida