First reptiles {stem reptile} were anapsids. Cut-lizard cotylosaur was low, stocky, and 20 centimeters to two meters long. Reptilia {reptile} include gecko, snake, iguana, turtle, crocodile, alligator, and lizard.
classes
The six reptile subclasses have different skulls: anapsid, diapsid, euryapsid, parapsid, synapsid, and therapsid.
evolution
Evolution was anapsid to diapsid to synapsid to therapsid. Euryapsids and parapsids evolved from diapsids.
land
Reptiles can live whole life cycle on land.
development
Reptiles have no larval stage in water. They develop continuously from egg to adult, requiring mechanisms for replacement and renewal.
skin
Thick dry leathery skin, with horny scales, allows continuous dry land existence, because it conserves water.
respiration
Reptiles have lungs.
skeleton: bone
Bones have growth rings in seasonal climates, with few blood vessels and haversian canals.
skeleton: pelvis
Reptiles have a strong pelvis, allowing running and/or standing on hind legs.
skeleton: jaw
Reptiles have muscles and jaws for chewing, not just grasping and tearing.
reproduction
Reptiles reproduce by intercourse and have internal fertilization. They lay eggs with leathery shells on land. An egg sac {amnion} holds water, so egg does not need to get water from sea, lake, or stream. Reptiles have egg-laying rituals, courtship rituals, territoriality, and sexual intercourse behaviors.
cloaca
The same body opening is for anus and reproductive tract.
muscle
Reptiles have only involuntary muscles controlled by automatic neuron circuits in ganglia and paleocortex.
nervous system
Cerebellum outer-layer basket cells process sensorimotor information and allow walking, running, and chewing. Brains have two-layered cortex and several ganglia. Paleocortex controls involuntary muscles and glands. Cortical neurons send axons to other cell layers and regions and receive signals from other paleocortex layers and regions. Paleocortex areas analyze information.
senses
Sense organs with more than one cell layer preprocess signals before sending them to brain. Median eye detects infrared light and later became pineal gland.
Early reptiles were, and most reptiles are, cold-blooded animals {poikilotherm}|.
Therapsid warm-blooded animals {endotherm}| had basal metabolism four times higher than poikilotherms and needed 10 to 30 times more food than poikilotherms.
The same body opening {cloaca}| can be for anus and reproductive tract.
Reptiles have two-layered nerve sheets {paleocortex}| connected to several ganglia, allowing more complex information processing and distribution. Paleocortex cerebrum covers forebrain and has distinct input layer and output layer.
Geckoes tilt toe hairs 30 degrees to let go while walking {toe peeling, hair}|.
Reptiles have one eye {median eye}| to detect infrared light. Later, median eye evolved to become pineal gland.
In reptiles, skull front-middle eye {parietal eye}| {third eye} detects sunlight level, regulates daily activities, and regulates seasonal responses to light and temperature. Parietal-eye light level affects puberty, sexual activity, hibernation, and aestivation.
Reptiles {reptile types} are anapsids, diapsids, synapsids, and therapsids.
Anapsids {anapsid} (Anapsida) were the first reptiles and are mostly extinct, except for turtles and tortoises (Chelonia), which have hard shells. Cut-lizards {cotylosaur} {cut-lizard} were low, stocky, two meters long, and the most-primitive reptiles. Other reptiles evolved from cut-lizard anapsids.
Chelonia {chelonian} are turtles and tortoises.
Sea turtles {sea turtle} have flipper legs and bony shells and lay eggs on shore.
Freshwater turtles {snapping turtle} (Chelydridae) can have rough shells and hooked beaks.
Aquatic turtles {soft-shelled turtle} can have flat flexible shells with leathery skin.
fresh water, North American, web-footed, tortoise {terrapin}.
plant eater, land, claws {tortoise, reptile} (Testudinidae).
beak, bony or leathery shell {turtle}.
Extinct aquatic reptiles {euryapsid} (Euryapsida) had long necks, small heads, long tails, and bloated bodies. They paddled, swam, and were up to 17 meters long, such as elasmosaurus. Euryapsids evolved from anapsids.
Diapsids {diapsid} (Diapsida) include tuatara, rhynchocephalia, extinct sphenodon, extinct ichthyosaur, and lepidosaurs. Lepidosaurs became squamata snakes and lizards.
evolution
Diapsids came from anapsids. Diapsids evolved to parasids and synapsids.
parietal eye
Parietal eye detected sunlight level and helped regulate daily activities and responses to light and temperature.
neck joint
New neck joint type, between head and trunk, put head at angle to vertebrae. Head turns around different axis than trunk, allowing freer head movement and improved ability to catch and eat prey. The new turning axis required triangulation to locate objects in space.
teeth
New teeth types were for cutting and chewing, to match new jaw types.
Diapsids include scaled lizards {lepidosaur} {scaled lizard}. Lepidosaurs became squamata, which became snakes and lizards.
snakes and lizards {squamata}.
Squamata {lizard} can have four legs, scales, and tails.
American Basiliscus lizards {basilisk} have crests and can run on hind legs.
Lizards {chameleon} can change color.
Lizards {gecko} can have 500,000 hairs {setae} on each foot. Hairs split into hundreds of ends. If ends are perpendicular to surface, they stick by van der Waals forces. Geckos tilt toe hairs 30 degrees to let go while walking {toe peeling, gecko}.
large {Gila monster}.
Lizards {horned toad} can have head horns and body spines.
horned {iguana}.
large {monitor lizard}.
Squamata {snake, animal} can have scales and no legs.
long thin ocean snake {sea snake}.
swimming snake {water snake}.
constrictor {anaconda}.
constrictor {boa constrictor}.
constrictor, jungle {python}.
poison {adder}.
poison {asp}.
poison {black adder}.
poison, forest {bushmaster}.
poison {cobra}.
poison {copperhead}.
poison {coral snake}.
poison, woods {cottonmouth}.
poison {pit viper}.
poison, desert {rattlesnake}.
poison, desert {sidewinder}.
poison {viper}.
poison, swimming {water mocassin}.
Diapsids {sphenodon} were one meter long, had large beak-like snouts, and had spines down back. They are extinct. Sphenodons had third eyes. They had nictating membranes. Sphenodons were archosaur ancestors.
Diapsids {rhynchocephalia} {rhynchosaur} were small, had beaks, and included sphenodon.
Diapsids {archosaur} had two large back limbs, two small front limbs, long tails, and teeth in sockets. They are extinct. Archosaurs evolved from sphenodons. Archosaurs include thecodonts.
Diapsids {thecodont} had insulation, had reptilian teeth, and included Troödon, Pterodactyl, and Pteranodon [-220000000]. They are extinct. Thecodonts came from archosaurs. They are bird, crocodile, sauropod, thecopod, pterosaur, Ornithischia, and Saurischia ancestors.
Thecodonts {pterosaur} (Pterosaura) had webbed wings on little fingers. Perhaps, pterosaurs had hair. They had light and long heads. Early pterosaurs had teeth and long tails, but later ones had neither. They are extinct. Pteranodon had seven-meter wingspan. Pterodactyl flew. Birds evolved from pterosaurs.
extinct flying reptile {pterodactyl}.
Thecodonts (Ornithischia) {bird hip} were herbivores. Ornithischia evolved from thecodonts. Anatosaurus had duckbill with flat wide jaw. Ankylosaurus had large bony plates on back, spikes on sides, and bony ball at tail tip. Triceratops had three horns on head and broad bone on neck.
Ornithischians {stegosaur} can eat plants, have back bony plates, and have spiked tails.
Crocodiles and alligators (Crocodilia) {crocodile, animal} evolved from thecodonts.
broad short snout {alligator}.
American, related to alligators {caiman}.
Extinct thecodonts {crurotarsan}| were like large crocodiles. Crurotarsans included phytosaurs, rauisuchians, and aetosaurs. Phytosaurs lived in water and were up to 13 meters long. Rauisuchians lived on land and were up to 10 meters long. Aetosaurs had armor. They flourished from 230 million years ago to 201 million years ago, until Late Triassic catastrophe, which dinosaurs survived. Crurotarsans are crocodile and alligator ancestors.
Thecodonts (Saurischia) {lizard hip} were bipeds with feet like thecopods or quadrupeds with feet like sauropods. They are extinct.
Saurischia quadrupeds {sauropod} had feet like lizards. Sauropods were large plant eaters. They had long necks and tails. They included Brontosaurus, Brachiosaurus, Diplodocus, and Apatosaurus. They are extinct. Prosauropods hatched with no teeth, four legs, and short tail. Perhaps, parents fed them. After they hatched, neck grew, tail lengthened, and forelimbs did not grow. Later sauropods had four legs and derived from juvenile stage.
vegetarian {brontosaur}.
Extinct Saurischia bipeds {thecopod} had feet like mammals.
Extinct Saurischia {theropod} had feet like mammals, were coelurosaurs or carnosaurs, were cold-blooded, had large range, and had few competitors.
Extinct theropods {carnosaur} were large meat eaters, such as Tyrannosaurus, Carcharodontosaurus, and Spinosaurus.
Extinct theropods {tyrannosaurus} were carnivores, had two legs, and had short arms.
Extinct theropods {coelurosaur} were fast meat eaters with tails and long necks.
Extinct theropods {gigantosaur} (Mapusaurus roseae) were carnivores.
Parasids {parasid} (Parasida) include extinct fish-lizard ichthyosaurs. Parasids lived in ocean, were one to twenty meters long, and had long noses. Parasids evolved from diapsids.
Extinct parasids {ichthyosaur} lived in ocean 245 million to 90 million years ago. At first, they were lizard-like and undulated like eels and then were fish-like and flipped tails like fish. They were one to twenty meters long, had long noses, were carnivores, and ate mostly animals like squid. Like all non-mammals, they had very large eyes with sclerotic rings.
Synapsids {synapsid} (Synapsida) had new joint type between head and trunk, so head was at angle to vertebrae and turned around different axis than trunk, which later led to free head movement. They had new teeth types for cutting and chewing. They are extinct. Synapsids came from diapsids. They are therapsid and mammal ancestors.
Extinct finback mammal-like synapsids {pelycosaur} were 60 centimeters long, had canine teeth, and chewed using jaw and jaw muscles different than anapsids and diapsids. Two-meter-long Dimetrodon had dorsal fin for warming and cooling blood [-260000000]. Pelycosaur species became Pristerognathids.
Extinct synapsids {pristerognathid} weighed 50 kilograms, were fast trotters, were endotherms, and included antesaurus, gorgon, and moschorhinids. They evolved from pelycosaurs. They gave rise to therapsids.
Extinct synapsids {therapsid} lived in south Gondwana.
endotherm
As endotherm warm-blooded animals, with basal metabolism four times higher than poikilotherm cold-blooded animals, they needed 10 to 30 times more food. Optimum temperature for metabolism uses heating and cooling mechanisms {thermoregulation, endotherm}, resulting in much higher available energy all day and allowing more activity throughout day, rather than just at midday.
hair
Hair or feathers helps temperature regulation.
hearing
Warm-bloodedness requires better hearing, because daily activity requires more warning signals and other communications. Therapsids had ear pinnae to gather sound better.
larynx
Therapsids had larynx, allowing sound production, accompanied by ability to hear and find meaning in sounds.
evolution
Therapsids evolved from Pristerognathids. Therapsids are mammal ancestors.
Therapsids had outer ear structures {ear pinna}, to gather sound better.
Therapsids had optimum temperature for metabolism, maintained by heating and cooling mechanisms {thermoregulation, therapsid}|.
Extinct therapsids {cynodontia} {cynodont} were dog-sized, were nocturnal, and slept curled up.
rib
They do not have lumbar-vertebrae ribs.
jaw
Lower jaw had dentary bone and had big canine teeth, incisors, and molars with multiple cusps. Snout and lips had muscles, possibly to suckle, and possibly whiskers.
palate
Hard palate enabled simultaneous breathing and chewing.
smell
Turbinals held olfactory receptors and warmed and humidified air. Number of olfactory genes became thousand, by gene duplication.
eye
Being nocturnal, they had large eyes and post-orbital bar.
They also had parietal eye.
evolution
They evolved from therapsids. They were mammal ancestors.
types
Cynodonts included Thrinaxadons and Procynosuchus.
Cynodont lower jaw had one main bone {dentary} and had big canine teeth, incisors, and molars with multiple cusps.
Extinct separate therapsids {dicynodont} were herbivores and included Lystrosaurus.
Cynodonts {Chiniquodontid} had teeth for meat eating.
Leopard-sized cynodont plant-eaters {traversodontid} had incisors and cheek teeth.
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Date Modified: 2022.0225