| SYSTEMATIC BIOLOGY |
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| CLASS ANAPSIDA |
Anapsida (an-AP-si-da) is derived from two Greek roots which mean the absence [an (άν)] of an arch [apsis (ayiV)]. This refers to the absence of temporal fenestrae in the skulls of these animals.
They ranged from large terrestrial herbivores to carnivores that occupied both aquatic and terrestrial environments. Some even evolved a bipedal gait independently of the Archosauromorpha. They have a very long fossil history (upper Pennsylvanian to the present) with much diversity of form; however, only the turtles survive to the present. They seem to have evolved from a line of pariesaurs which became dorsoventrally flattened, evolved a protective shell or carapace made of flattened ribs, lost their teeth, and developed a horny beak. The turtles today are divided into two major groups, each defined by how it retracts its head into the carapace. The pleurodires are called the side-necked turtles because they retract their heads sideways in a s-shape as seen from above. Mostly, the pleurodires have a southern continental distribution and inhabit freshater habitats.
Cryptodires retract their heads straight back so that the neck forms an s-shape as seen from the side. They include three major groups: the sea turtles and leatherbacks, the soft-shell turtles, and the tortoises and pond/box turtles. The sea turtles and leatherbacks can grow to be more than 2 meters long. Although they are obligate marine animals with their limbs modified as flippers, they do come ashore on certain sandy beaches to lay eggs. The leatherbacks range throughout the oceans and feed almost exclusively on jellyfish.
Softshell turtles occupy temperate and tropical freshwater environments throughout much of the world. They have a reduced carapace skeleton, thus the name softshell and the covering is leathery. They are mainly carnivores.
The tortoises and pond turtles form the third great group of living cryptodires. Tortoises usually are large terrestrial herbivores of warm, dry environments. These may be among the longest-lived vertebrates on earth. For example, a Madagascar Radiated Tortoise presented to the royal family of Tongo in 1777 by Captain Cook lived to be more than 188 years old.
Pond turtles and box turtles range from mostly aquatic to terrestrial animals of the tropics and temperate areas of the Americas, Eurasia, and Africa. By and large, the box turtles tend to be herbivores or omnivores while the pond turtles tend to be carnivores. The alligator snapping turtle is the largest freshwater chelonian in North America. It feeds by opening its mouth and wiggling an extension of its tongue as a lure. When a fish enters the mouth to investigate the movement, the turtle slams its jaws shut, instantly killing or disabling it victim.
| HIERARCHICAL TAXONOMY OF THE CLASS ANAPSIDA. The following descriptions come from Benton (2005) and the Animal Diversity Web from the University of Michigan Museum of Zoology. The structure of the following system is also based, in part, on the phylogenetic treatment by Mikko's Phylogeny Web (from the Finnish Museum of Natural History). Taxa in red are extinct. |
 
Image of Mesosaurus, an extinct basal anapsid that was aquatic (left) and a sea turtle, a modern chelonian. |
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Image of Mesosaurus from: http://www-geology.ucdavis.edu/~cowen/HistoryofLife/mesosaurus.gif Image of sea turtle from the Systematic Biology Biodiversity Archive. CLASS ANAPSIDA 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. ORDER UNNAMED (BASAL ANAPSID FAMILIES)+ FAMILY MESOSAURIDAE These 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. Lower Permian Mesosaurus FAMILY MILLERETTIDAE Insectivores. The skulls of these animals resembled lizards. They have a temporal fenestra, but the bar is incomplete. Upper Permian Millerosaurus FAMILY
BOLOSAURIDAE The
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
plants). FAMILY
PROCOLOPHONIDAE These
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. Upper
Permian to Upper Triassic Procolophon FAMILY
PAREIASAURIDAE These 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. Upper Permian Pareiasaurus,
Elginia, Scutosaurus. ORDER 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. FAMILY
PROGANOCHELIDAE Characters
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.
Upper
Triassic Proganochelys,
Proterocheris FAMILY
ASTRALOCHELIDAE The
palate is fused to the braincase and the eardrum is partially encased in bone. Lower
Jurassic Astralochelys CASICHELYDIA:
Turtles that can retract their heads into the carapace (some extinct forms
could not do this). SUBORDER PLEURODIRA These turtles retract their heads sideways. The jaw muscles pass over the trochlea, a knob formed by the ptergoid. Upper Triassic to present Proterochersis+, FAMILY CHELIDAE Austro-American 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. Miocene to present. Acanthochelys,
Chelodina, Chelus, Elseya, Elusor, Emydura, Hydromedusa, Phrynops, Platemys,
Pseudemydura, Rheodytes. FAMILY PELOMEDUSIDAE Afro-American
Side-Necked Turtles. These are
animals of swamps, rivers, ponds, and temporary waters of Erymnochelys,
Pelomedusa, Peltocephalus, Pelusios, Podocnemis, Stupendemys+. SUBORDER CRYPTODIRA 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 SUPERFAMILY
UNNAMED The
basal cryptodires are characterized by retaining ptergoid teeth. Lower
Jurassic Kayentachelys SUPERFAMILY
BAENOIDEA+ Characteristic
narrow snout. FAMILY
BAENIDAE Baena,
Polythorax, Probaena, Trinitichelys, Hayemys, Eubaena, Plesiobaena, Palatobaena,
Dorsetochelys, Uluops. FAMILY
CHENGYUCHELYIDAE Chengyuchelys,
Sichuanchelys. FAMILY
NEURANKYLIDAE Boremys,
Compsemys, Naomechelys, Neurankylus, Thescelus. SUPERFAMILY
UNNAMED FAMILY
MEIOLANIIDAE These
had broad skulls (up to 50 cm wide) with horns. Pleistocene Crossochelys,
Niolamia, Ninjemys, Warkalania, Meiolania. SUPERFAMILY CHELONIOIDEA Sea turtles. 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. FAMILY
PLESIOCHELYIDAE+ Craspedochelys,
Hylaeochelys, Neusticemys, Plesiochelys, Portlandemys, Tienfuchelys, Desmemys. FAMILY CHELONIIDAE Sea Turtles. 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. Upper Cretaceous to present Caretta,
Chelonia, Eretmochelys, Lepidochelys, Natator. FAMILY DERMOCHELYIDAE Leatherback 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. Dermochelys. SUPERFAMILY TRINYCHOIDEA Softshell Turtles FAMILY TRIONYCHIDAE Softshell
Turtles. Freshwater (rarely brackish
water) of eastern Late Jurassic to the present Amyda,
Apalone, Aspiderestes, Chitra, Cyclanorbis, Cycloderma, Dogania, Lissemys,
Nilssonia, Palea, Pelochlys, Pelodiscus, Rafetus, Trionyx. FAMILY CARETTOCHELYIDAE Pignose
Turtles. Freshwater (and brackish
water) of rivers and lagoons in Eocene to the present Carettochelys. FAMILY DERMATEMYDIDAE Mesoamerican
River Turtles. Large rivers and lakes of They have an extensive fossil history Cretaceous to the Miocene and represented today by a single species. Dermatemys. FAMILY KINOSTERNIDAE Mud Turtles
and Musk Turtles. Freshwater (slow
streams and lakes) of the Oligocene to present Claudius,
Kinosternon, Staurotypus, Sternotherus. SUPERFAMILY TESTUDINOIDEA Tortoises FAMILY TESTUDINIDAE Tortoises.
Terrestrial in warm climates (deserts to rainforests) of the Lower Eocene to present Agrionemys,
Dipsochelys, Furculachelys, Geochelone, Gopherus, Homopus, Indotestudo, Kinixys,
Malocochersus, Manouria, Platysternon, Psammobates, Pyxis, Testudo. FAMILY EMYDIDAE Box Turtles
and Pond Turtles. Freshwater and
brackish water species of Upper Cretaceous to the present Batagur,
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,
Trachemys, Gyremys+. INCERTAE SEDIS FAMILY
CAPTORHINIDAE Relatively
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.
Permian Captorhinus FAMILY
PROTOROTHYRINIDAE+ This
is a family of basal anapsids. Lizard-like
insectivores. Their position is
unclear; they may be basal to the synapsids, diapsids, and anapsids. Upper
Carboniferous (Pennsylvanian) to lower Permian. Hylonomus, Paleothrys. |
