The anapsids, as the name
implies, have no temporal fenestrae. Furthermore,
they have (had) no caniniform maxillary teeth, and the shaft of the femur is
(was) long and slender ( Benton, 2005). In this system, the
anapsids have two orders. The Basal
Anapsid Families are placed into an unnamed order that almost certainly is
paraphyletic. They include animals
that were fully aquatic carnivores to large, terrestrial herbivores.
The second order, Testudines, is monophyletic and includes the turtles
and their relatives. The
anapsids are a sister group to the diapsids, and the synapsids are the outgroup.
PARAREPTILIA (BASAL ANAPSID FAMILIES)+
animals were aquatic and relatively small (1m and smaller).
They had a relatively long neck and a long, flattened tail.
The long, narrow jaws are lined with needle-like teeth that interlock as
the jaws close. They may have used
them to trap small fish or to strain out aquatic invertebrates.
The skulls of these animals resembled lizards.
They have a temporal fenestra, but the bar is incomplete.
animals in this group had achieved bipedal locomotion.
Hind legs were longer than the front legs.
Also, its feet were long, and it must have run on its toes.
Bulbous occluding teeth (likely a herbivore that specialized on tough
animals had horn-like projections on the sides of the skull (defensive?).
Cheek teeth blunt and occluding. Also,
herbivores of tough plants. Broad
feet suggest that they were burrowers.
Permian to Upper Triassic
were relatively large stocky herbivores. They
had a bony frill extending from the sides of the skull and projections from the
lower jaw. Legs and feet were
elephant-like. They had a very
muscular neck. This has been
suggested as the sister-group to the turtles.
TESTUDINES (CHELONIA) The Turtles
These are anapsids that are
toothless with a horny beak. The
body is flattened and a shell formed by modified ribs (above) and a bony
plastron below. The bone is overlain
by overlapping plates of keratin.
typical of turtles except it has a palate with teeth and a large embayment in
the skull for the eardrum. The palate is loosely connected to the braincase.
palate is fused to the braincase and the eardrum is partially encased in bone.
Turtles that can retract their heads into the carapace (some extinct forms
could not do this).
These turtles retract their heads
sideways. The jaw muscles pass over the trochlea, a knob formed by the ptergoid.
Upper Triassic to present
Side-Necked Turtles (also called Snake-Necked Turtles).
Generally animals of slow-moving streams and swamps of Australia, New Guinea, and
South America. The neck is very long and retracts
by an s-shaped lateral motion thus causing distinctive structural changes in the
neck. They are carnivores with a
broad range of aquatic prey.
Chelodina, Chelus, Elseya, Elusor, Emydura, Hydromedusa, Phrynops, Platemys,
Side-Necked Turtles. These are
animals of swamps, rivers, ponds, and temporary waters of
. Pelomedusids have no cervical
scute, and distinctive nasal bone, splenial bone, and cervical vertebrae.
These can be omnivores.
Pelomedusa, Peltocephalus, Pelusios, Podocnemis, Stupendemys+.
These turtles retract their heads
straight back by making a vertical bend in the neck. The trochlea is formed the
otic capsule, further back that in the pleurodires.
Lower Jurassic to present
basal cryptodires are characterized by retaining ptergoid teeth.
Polythorax, Probaena, Trinitichelys, Hayemys, Eubaena, Plesiobaena, Palatobaena,
Compsemys, Naomechelys, Neurankylus, Thescelus.
Modesto 1999). Mesosaurids were used by Wegener (1915
had broad skulls (up to 50 cm wide) with horns.
Niolamia, Ninjemys, Warkalania, Meiolania.
These marine turtles show an elongation of digits 3 and 4; the carpals
and tarsals are flattened; and share a particular articulation between the 8th
cervical vertebra and the nuchal bone. The
limbs are flippers; the forelimbs are larger than the hind limbs.
Hylaeochelys, Neusticemys, Plesiochelys, Portlandemys, Tienfuchelys, Desmemys.
Marine animals of all tropical seas.
These animals are large; the carapace can be up to 2.1m long.
The unifying synapomorphy is a platycoelous articulation between the 6th
and 7th cervical vertebrae. They
nest on particular sandy beaches. Omnivores.
Cretaceous to present
Chelonia, Eretmochelys, Lepidochelys, Natator.
Turtles. Marine with distributions
from the tropical seas toward the poles. This
is the largest of all the extant turtles (a carapace almost 2.5m long).
The carapace is leathery with embedded osteoderms; and it has 7 elongate
ridges (keels). These feed almost
entirely on jellyfish. The head
cannot be retracted and the 4th cervical vertebra is biconvex.
They nest on sandy beaches.
Turtles. Freshwater (rarely brackish
water) of eastern
, Asia, and
. Softshells are very flattened and
heads have elongate rostra. Most of
the carapace skeleton is lost. They
have the following synapomorphies: fleshy lips over the keratin beak, no
articulation between the centra of the last cervical and first thoracic
vertebrae, and claws only on the middle three digits.
Jurassic to the present
Apalone, Aspiderestes, Chitra, Cyclanorbis, Cycloderma, Dogania, Lissemys,
Nilssonia, Palea, Pelochlys, Pelodiscus, Rafetus, Trionyx.
Turtles. Freshwater (and brackish
water) of rivers and lagoons in
. The carapace is leathery; and they
have an elongate, pig-like snout. Synapomorphies
include: paired articulation between 8th vertebra and the nuchal
bone, limbs terminate in paddles.
River Turtles. Large rivers and lakes of
. It is almost completely aquatic
and performs a significant amount of gas exchange between the lining of the
nasal passage and water.
They have an
extensive fossil history Cretaceous to the Miocene and represented today by a
and Musk Turtles. Freshwater (slow
streams and lakes) of the
. The carapace may have a keel.
The plastron is cross-shaped and may be hinged.
Synapomorphies include: 10 pairs of peripheral bones, an acetabulum with
an illio-ischial notch, frontal bone does not touch the orbit.
All are carnivores.
Kinosternon, Staurotypus, Sternotherus.
Terrestrial in warm climates (deserts to rainforests) of the
, the Galapagos, and the Aldabra atoll. The
carapace has a high dome and the plastron is almost complete and usually lacks a
hinge. They have pillar-like legs
and have 4 digits on the hind legs. Mainly
herbivores. Good fossil history.
Dipsochelys, Furculachelys, Geochelone, Gopherus, Homopus, Indotestudo, Kinixys,
Malocochersus, Manouria, Platysternon, Psammobates, Pyxis, Testudo.
and Pond Turtles. Freshwater and
brackish water species of
. Structural synapomorphies are very
few: no contact between the squamosal and parietal bones; and the frontal bone
forms part of the orbit. They range
from carnivory to herbivory.
Cretaceous to the present
Callagur, Chinemys, Chrysemys, Clemmys, Cuora, Cyclemys, Deirochelys, Emydoidea,
Emys, Geoclemys, Geomyda, Graptemys, Hardella, Heosemys, Hieremys, Kachuga,
Malaclemys, Malayemys, Mauremys, Melanochelys, Morenia, Notochelys, Ocadia,
Orlitia, Pseudemys, Pyxidea, Rhinoclemmys, Sacalia, Siebenrockiella, Terrapene,
small animals with a skull that was much broader at the back.
The dentition was heterodont. The
cheek teeth grew in multiple parallel rows (parallel to the axis of the dentary).
The multiple teeth suggest that they were herbivores specializing in very
tough plants or hard-shelled invertebrates.
These animals, although anapsid, likely were
in the line leading to the diapsids (Eodiapsida + Leptosauromorpha +
is family likely was the basal anapsids. Lizard-like
insectivores. Their position is
unclear; they may be basal to the synapsids, diapsids, and anapsids.
Carboniferous (Pennsylvanian) to lower Permian.