Class Reptilia

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Class Reptilia
Subclass Testudines Order Chelonia (modern
turtles) Subclass Synapsida (extinct) Subclass
Sauria Order Eosuchia (extinct) Infraclass
Lepidosauria Order Ichthyosauria (extinct) Order
Plesiomorpha (extinct) Order Sphenodontia
(tuatara) Order Squamata (snakes and
lizards) Infraclass Archosauroia Order Rauisuchia
(extinct) Order Pterosauria (extinct) Order
Crocodilia (alligators, crocodiles, gavial) Order
Saurischia (extinct) Suborder Therapoda
(extinct) Order Ornithischia (extinct)
From Conant and Collins 1991
From Linzey 2001
From Conant and Collins 1991
From Conant and Collins 1991
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Class Reptilia
A somewhat enigmatic group -many authors disagree
with what organisms should be included in this
group or whether the group reptilia should be
recognized at all -much discussion involves the
placement of birds and crocodilians
Turtles Tuatara Snakes/Lizards
Crocodiles Birds

• -traditional taxonomists consider Birds to be a
  separate Class
• but this would make the Class Reptilia
  paraphyletic because crocodilians are more
  closely related to birds than to any other
  reptiles.
• Many contemporary authors lump birds and reptiles
  into a single class
• Sauropsida

Stem Reptiles
Paraphyletic a taxonomic grouping that does not
include all the taxa derived from a common
ancestor. As a rule taxonomists try to avoid
paraphyletic classifications
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Class Reptilia
Reptiles include two extant subclasses and one
extinct subclass Subclass Testudines
(Anapsids) Subclass Sauria (Diapsids) Subclass
Synapsida (extinct) These groups are
traditionally classified according to the number
of temporal fenestrae present
Temporal fenestrae are labeled A on this
picture of a Diapsid skull
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Class Reptilia

• -Anapsid (Testudines) skulls have no temporal
  fenestrae
• characteristic of oldest known reptiles and
  modern turtles
• Diapsid (Sauria) skulls, at least primitively,
  have two fenestrae
• Group includes all living reptiles other than
  turtles.

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Class Reptilia

• Synapsid skulls had one temporal fenstra
• This lineage eventually leads to the mammals

Dimetredon (a synapsid reptile)
Horse (Equus caballus)
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From Linzey 2001
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Reptilian Origins
Reptiles and all higher vertebrates are
Amniotes The evolution of the Amniote Egg
represents the 4th major milestone in vertebrate
evolution The amniote egg contains extraembryonic
membranes that serve to contain the embryo in a
fluid-fill environment. -the egg shells
themselves are typically thick and leathery, thus
minimizing water loss.
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Reptilian Origins
Amniote eggs are, therefore, not as constrained
by the need for a wet external environment. It is
suggested that the amniote egg arose as an
adaptation to avoid predators -eggs laid in the
terrestrial environment would be less vulnerable
than eggs laid in the predator-rich aquatic
environment
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Reptilian Origins
This, in turn, has allowed reptiles to adapt to a
much wider variety of terrestrial habitats that
did amphibians.
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Reptilian Origins
The fossil record contain numerous examples of
fossils that bear both reptilian and amphibian
characteristics A typical example is Seymouria
from the lower Permian Deposits of
Texas -amphibian type of skull, reptilian
vertebrae, reptilian dentition (teeth set into
deep sockets)
From Linzey 2001
Seymouria was capable of terrestrial life, could
raise its body well off the ground -but was it an
early reptile?
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Reptilian Origins

• Seymouria was too recent to be a reptilian
  ancestor
• Also, closely related forms had aquatic young,
  suggesting that these forms were not amniotes.
• thus, current thinking puts Seymouria in with the
  Labyrinthodont amphibians

I am not a reptile!
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Reptilian Origins

• Earliest known reptiles have an Anapsid skull
  type and belong to the informal Order
  Captorhinida
• also known as Stem Reptiles, because these forms
  were ancestral to all other reptiles

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Reptilian Origins
Captorhinida arose in the early Carboniferous and
survived to the mid Triassic Two important groups
initially divered from these forms
-by the end of the Carboniferous the Synapsids
diverge from this group -eventually become mammals
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Reptilian Origins
-one other group, the Testudines, also diverged
from the Captorhinida -during early Permian or
late Carboniferous. -this group becomes the
modern Turtles (Order Chelonia)
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Reptilian Origins
Turtle-like Testudines appear in the
mid-Permian First true turtles show up in the
Triassic about 210 mya in freshwater Oldest
marine forms early Cretaceous Largest recorded
Archelon 3.3 m. X 3.6 m.
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Reptilians

• Modern Turtles
• 12 families, only two are marine
• Others predominantly freshwater
• A few mainly terrestrial

Wood Turtle
Eastern Box Turtle
Gopher Tortoise
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Reptilians

• Largest living species is the Leatherback turtle
• marine species that grows to 916 kg and 1.9 m long

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Reptilians
Largest non-marine turtle is the Galapagos
Tortoise -grows to 310 kg, lives over 200 yrs
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Reptilians
Largest freshwater species Alligator snapping
turtle (80 cm, 143.3 kg)
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Reptilian Origins
Modern turtles are variously herbivores,
omnivores, and carnivores -none have teeth, have
a horny beak instead All have internal
fertilization, but females are oviparous Eggs are
typically deposited in a nest in sand or loose
soil -for many species there is temperature
dependant sex determination
From Conant and Collins 1991
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Class Reptilia, Subclass Diapsida
Infraclass Lepidosauria
Infraclass Archosauria
Subclass Sauria (Diapsids)
Subclass Synapsida
Testudines (Anapsida)
Mammals
Captorhinida (Anapsida)

• Diapsids first appear in late Carboniferous, very
  soon after first Captorhinida
• almost immediately diverge into two lineages
  (Suborders)
• Lepidosauria Archosauria

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Subclass Sauria, Infraclass Lepidosauria

• Earliest members of the Lepidosauria appear in
  late Carboniferous
• belong to the Order Araeoscelida
• All early forms with diapsid skull type, most
  were lizard-like

Petrolacosaurus kansensis
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Subclass Sauria, Infraclass Lepidosauria

• Lepidosaurs underwent an extensive adaptive
  radiation in Triassic
• This resulted in 4 new orders. Two of these went
  extinct in the Cretaceous.

Extinct before end of Cretaceous Extinct at end
of Cretaceous Dont let this happen to you!
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Subclass Sauria, Infraclass Lepidosauria

• The two surviving orders are Sphenodontia and
  Squamata

The tuatara is a Sphenodontid.
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Infraclass Lepidosauria, Order Sphenodontia

• About two species of lizard-like reptiles that
  occupy some 20 islands north of New Zealand.
  Relics from the Triassic.
• unlike other diapsids
• Lost teeth are not replaced, palate has an extra
  row of teeth, have a parietal foramen on top of
  skull to accommodate the pineal (3rd) eye.
• Nocturnal, primarily insectivorous, grow to 0.6
  m, takes 10-20 years to mature.

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Infraclass Lepidosauria, Order Squamata

• Squamates first appear in Triassic
• Modern forms include lizards, snakes, and
  amphisbaenans

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Infraclass Lepidosauria, Order Squamata

• lizards are typical tetrapods
• There are about 3800 species
• Moveable eyelids, external ear openings
• Most are terrestrial or arboreal (live in trees),
  very few aquatic lizards (eg. Marine Iguana)

Green Anole
Marine Iguana
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Infraclass Lepidosauria, Order Squamata

• Most have four limbs.
• Some exceptions glass lizards

Western Slender Glass Lizard
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Infraclass Lepidosauria, Order Squamata

• Lizards invariably lay eggs usually buried in
  sand or loose soil.
• Mostly carnivores (insectivores), some frugivores
  and omnivores

Basilisk lizard running on water link
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Infraclass Lepidosauria, Order Squamata

• Snakes arose from lizards just before the end of
  the Jurassic
• highly modified legless lizards, the most recent
  group of reptiles
• lack moveable eyelids and external ear openings
• there are 2900 species worldwide.

Gopher Snake
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Infraclass Lepidosauria, Order Squamata
In a few species (Pythons) males have vestigial
hindlimbs that are used during courtship.
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Infraclass Lepidosauria, Order Squamata
Snakes are aquatic, terrestrial, and arboreal
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Infraclass Lepidosauria, Order Squamata
Snakes may be oviparous or viviparous They are
invariably carnivores, eating insects, mammals,
birds, and other reptiles
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Infraclass Lepidosauria, Order Squamata

• Amphisbaenians represent over 130 species of
  vermiform squamates mostly found in South America
  and Africa, one species in Florida
• Poorly studies, fossorial, most less than 6 as
  adults
• Also known as worm lizards

Mexican Worm Lizard Bipes biporus
Florida Worm Lizard Rhineura floridana
Link
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Subclass Diapsida, Superorder Archosauria
The earliest archosaurs belong to the order
Rauisuchians
Rauisuchians are all early diapsids, but vary
considerably First fossils come from late Permian
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Subclass Diapsida, Superorder Archosauria
Radiated in Triassic and are considered to be the
stem group for all archosaurs Ranged in size from
20 kg to 80,000 kg Many had limbs oriented
beneath the body
Body
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Subclass Diapsida, Superorder Archosauria
The Archosaur radiation resulted in four new
orders. Of these only the Crocodilians remain
today classified as reptiles
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Subclass Diapsida, Superorder Archosauria
The extinct orders of Archosaurs include some of
the most fantastic and interesting reptiles that
ever existed these are the dinosaurs (ruling
reptiles) and the Pterosaurs
Pterosaurs were flying reptiles that are
unrelated to birds Went extinct at end of
Cretaceous
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Subclass Diapsida, Superorder Archosauria
Dinosaurs represent two orders of extinct
archosaurs. Over 359 species have been
identified Dinosaurs went extinct at end of
Cretaceous
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Superorder Archosauria, Order Crocodilia

• Crocodilians first appear in the late Triassic as
  aquatic reptiles
• descended from bipedal Rauisuchians
• Still evident from the fact that in all living
  crocodilians, the forelimbs are considerably
  smaller than the hindlimbs

Link
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Superorder Archosauria, Order Crocodilia

• Living crocodilians are all carnivores
• One fossil form may have been a herbivore

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Superorder Archosauria, Order Crocodilia

• Living crocodilians are found in freshwater or
  brackish water
• One fossil marine form
• Living forms include

Alligators (2 species, 1 in US and 1 in China
that is critically endangered)
American Alligator (Alligator mississippiensis)
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Superorder Archosauria, Order Crocodilia
Caimans - 6 species, all neotropical
Yacare Caiman (Caiman yacare)
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Superorder Archosauria, Order Crocodilia
Crocodiles. 13 species found worldwide in
tropical latitudes
Ameican Crocodile (Crocodylus acutus)
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Superorder Archosauria, Order Crocodilia
Gharial (1 species found in India - Gavialis
gangeticus)
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Superorder Archosauria, Order Crocodilia

• Crocodilians are unique in exhibiting extensive
  parental care
• by female who builds and tends a nest

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SphenodontiaSquamataTwo extinct
ordersAraeoscelida (extinct stem group)
Summary of Reptilian Affinities
CrocodiliaThree extinct ordersRauisuchia
(extinct stem group)
Superorder Archosauria
Superorder Lepidosauria
Subclass Sauria (Diapsida)
Subclass Synapsida
Mammals
Testudines (Anapsida)
Captorhinida (Anapsida)