Crocodilia (or
Crocodylia) is an order of large
reptileReptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes that generally have skin covered in scales or scutes. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane...
s that appeared about 84 million years ago in the late
CretaceousThe Cretaceous , Latin language for "chalky", usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period of the...
Period (
CampanianThe Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
stage). They are the closest living relatives of birds, as the two groups are the only known survivors of the
ArchosaurArchosaurs are a group of diapsid amniotes represented by modern birds and crocodilians. This group also includes extinct non-avian dinosaurs, pterosaurs and relatives of crocodiles....
ia. Members of the crocodilian
stem groupA crown group is the smallest monophyletic group, or "clade", to contain the last common ancestor of all members, and all of that ancestor's descendants...
, the
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
CrurotarsiThe Crurotarsi are a group of archosaurs, whose name was erected as a node-based clade by Paul Sereno in 1991 to supplant the old term Pseudosuchia. Crurotarsi are by definition the sister group of the Avemetatarsalia .- Description :Crurotarsi is one of the two primary daughter clades of the...
, appeared about 220 million years ago in the
TriassicThe Triassic is a geologic period and system that extends from about 251 to 199 Ma . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
Period and exhibited a wide diversity of forms during the
MesozoicThe Mesozoic Era is one of three geologic eras of the Phanerozoic eon. The division of time into eras dates back to Giovanni Arduino, in the 18th century, although his original name for the era now called the "Mesozoic" was "Secondary" The Mesozoic Era is one of three geologic eras of the...
Era.
The correct vernacular term for this group is "
crocodilians" and it includes the
alligatorAn Alligator is a crocodilian in the genus Alligator of the family Alligatoridae. The name alligator is an anglicized form of el lagarto the Spanish term for "lizard", the name by which early Spanish explorers and settlers in Florida called the alligator...
,
crocodileA crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
,
gharialGavialidae is a family of reptiles within the order Crocodilia. Gavialidae consists of only two surviving species, the gharial and the false gharial , which are each the sole living representatives of their genera...
and
caimanCaimaninae are one of two subfamilies of the family Alligatoridae.The list of species:* Subfamily Caimaninae** Genus Necrosuchus ** Genus Eocaiman ** Genus Paleosuchus...
families. The term 'crocodiles' is sometimes incorrectly used to refer to alligators and caiman, or even their distant prehistoric relatives, "
marine crocodilesThalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are sometimes colloquially referred to as marine crocodiles or sea crocodiles, though they are not actually members of Crocodilia.The term...
".
Spelling
The group is often spelled 'Crocodylia' for consistency with the genus
CrocodylusCrocodylus is one of three genera from the Crocodylinae subfamily extending from the Crocodylidae family. Within this genus, there are twelve species:* American Crocodile, Crocodylus acutus ...
(
LaurentiJosephus Nicolaus Laurenti was an Austrian naturalist of Italian origin .Laurenti is considered the auctor of the class Reptilia through his authorship of Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena on the poisonous function of reptiles and amphibians...
, 1768). However,
Richard OwenSir Richard Owen KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
used the -i- spelling when he published the name in 1842, so it is generally preferred in the scientific literature. The -i- spelling is also a more accurate
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
ization of the
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
κροκόδειλος (
crocodeilos, literally "pebble-worm", referring to the texture and shape of the animal). However, the y-spelling is increasingly common, especially in the context of phylogeny-based names in which Crocodylia is limited to the crown group.
Description
The smallest species of crocodilian is the
Cuvier's Dwarf CaimanThe Cuvier's Dwarf Caiman or Musky Caiman, Paleosuchus palpebrosus, is a relatively small crocodilian reptile from northern and central South America. It is found in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Surinam and Venezuela...
and the largest is the
Saltwater CrocodileSaltwater or estuarine crocodile is the largest of all living reptiles. It is found in suitable habitats throughout Southeast Asia, Northern Australia, and the surrounding waters...
. The basic crocodilian
body planA body plan is essentially the blueprint for the way the body of an organism is laid out. An organism's symmetry,
is a very successful one; modern species closely resemble their
CretaceousThe Cretaceous , Latin language for "chalky", usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period of the...
ancestors of 84 million years ago. Mammals, too, have adapted to this body plan at least once in history. One ancestral whale family, the
AmbulocetidaeAmbulocetidae is a family of early cetaceans that still were able to walk on land. The genus Ambulocetus, after which the family is named, is by far the most complete and well-known ambulocetid genus due to the discovery by Thewissen et al. of a partially complete specimen of Ambulocetus natans...
, were aquatic predators living in rivers and lakes, and they filled an ecological niche similar to the crocodilians.
Crocodilians have a flexible semi-erect (semi-sprawled) posture. They can walk in low, sprawled "belly walk," or hold their legs more directly underneath them to perform the "high walk." Most other reptiles can only walk in a sprawled position, and
chameleonThe family Chamaeleonidae are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, and the...
s are the only modern reptiles with a more erect posture than crocodilians. The semi-erect posture makes it possible for some species to gallop on land if necessary. An Australian species can reach a speed of over 16 km/h while galloping on an irregular forest floor. Crocodilian ancestors, fast-moving terrestrial predators like the
rauisuchiaRauisuchia are a poorly known assemblage of predatory and mostly large Triassic archosaurs. Originally it was believed that they were related to erythrosuchids, but it is now known that they are crurotarsans. Three families are generally recognised: Prestosuchidae, Rauisuchidae, and...
ns, actually had a fully erect posture, indicating that the sprawling and semi-erect posture of crocodilians evolved after they adapted to as semi-aquatic ambush predators. Their ankle bones, or
tarsiIn tetrapods, the tarsus are the cluster of bones in the foot between the tibia and fibula and the metatarsus. The bones of the tarsus do not belong to individual toes, whereas those of the metatarsus do...
are highly modified. Modern crocodilian locomotion is not a primitive trait, but a specialization for their semi-aquatic lifestyle.
Teeth and jaws
All crocodilians have, like
Homo sapiens (humans), thecodont dentition (teeth set in bony sockets) but unlike mammals, they replace their teeth throughout life (though not in 'extreme' old-age). Juvenile crocodilians replace teeth with larger ones at a rate as high as 1 new tooth per socket every month. After reaching adult size in a few years, however, tooth replacement rates can slow to two years and even longer. Very old members of some species have been seen in an almost "edentulous" (toothless) state, after teeth have been broken and replacement slowed or ceased. The result of this is that a single crocodile can go through at least 3,000 teeth in its lifetime. Each tooth is hollow, and the new one is growing inside the old. In this way, a new tooth is ready once the old is lost.
Crocodilians have a secondary bony palate that enables them to breathe when partially submerged, even if the mouth is full of water. Their internal nostrils open in the back of their throat, where a special part of the tongue called the "palatal valve" closes off their respiratory system when they are underwater. This way they can open their mouths underwater without choking. Most reptiles lack a
secondary palateThe secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates.In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medially and their mutual fusion in the midline...
, but some
skinkSkinks are the most diverse group of lizards. They make up the family Scincidae which shares the superfamily or infraorder Scincomorpha with several other lizard families, including Lacertidae...
s (family Scincidae) have evolved a bony secondary palate too, to varying degrees.
CrocodileA crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
s and
gharialThe gharial , sometimes called the Indian gavial or gavial, is one of two surviving members of the family Gavialidae, a long-established group of crocodile-like reptiles with long, narrow jaws. It is a critically endangered species...
s have modified salivary glands on their tongue (
salt glandThe salt gland is an organ for excreting excess salts. It is found in elasmobranchs, seabirds, and some reptiles. In sharks, salt glands are found in the rectum, but in birds and reptiles, they are found in or on the skull, in the area of the eyes, nostrils or mouth. In crocodiles, the salt is...
s), which are used for excreting excess salt
ionAn ion is an atom or molecule where the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge...
s from their body.
AlligatorAn Alligator is a crocodilian in the genus Alligator of the family Alligatoridae. The name alligator is an anglicized form of el lagarto the Spanish term for "lizard", the name by which early Spanish explorers and settlers in Florida called the alligator...
s and
caimanCaimaninae are one of two subfamilies of the family Alligatoridae.The list of species:* Subfamily Caimaninae** Genus Necrosuchus ** Genus Eocaiman ** Genus Paleosuchus...
s have them too, but here they are non-functioning. This indicates that at some point the common origin of the Crocodylia were adapted to saline/marine environments. This also explains their wide distribution across the continents (i.e. marine dispersal). Species like the
saltwater crocodileSaltwater or estuarine crocodile is the largest of all living reptiles. It is found in suitable habitats throughout Southeast Asia, Northern Australia, and the surrounding waters...
(
C. porosus) can survive protracted periods of time in the sea, and can hunt prey within this environment.
Crocodilians are often seen lying with their mouths open, a behavior called gaping. One of its functions is probably to cool them down, but since they also do this at night and when it is raining, it is possible that gaping has a social function as well.
Internal organs
Crocodilians lack a
vomeronasal organThe vomeronasal organ , or Jacobson's organ, is an auxiliary olfactory sense organ that is found in many animals. It was discovered by Ludwig Jacobson in 1813....
(except in the embryonic stage) and a urinary bladder.
Like mammals and birds and unlike other reptiles, crocodiles have a four-chambered heart; however, unlike mammals,
oxygenatedOxygenation may refer too:* Oxygenation , the process by which concentrations of oxygen increase within a tissue* Water oxygenation, the process of increasing the oxygen saturation of the water...
and deoxygenated blood can be mixed because of the presence of the left
aortic archThe arch of the aorta begins at the level of the upper border of the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left side of the trachea and finally passes downward on the left...
. The
right ventricleThe right ventricle is one of four chambers in the human heart. It receives deoxygenated blood from the right atrium via the tricuspid valve, and pumps it into the pulmonary artery via the pulmonary valve and pulmonary trunk....
has two
arteriesArteries are blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.The circulatory system is extremely important for sustaining life...
leaving it; a pulmonary artery, which goes to the lungs, and the left aortic arch, which goes to the body, or systemic circulation. There is also a hole, the
foramen of PanizzaThe Foramen of Panizza is a hole with that connects the left and right aorta as they leave the heart of all animals of the order Crocodilia.Crocodilians have a completely separated ventricle with deoxygenated blood from the body, or systemic circulation, in the right ventricle and oxygenated blood...
, between the left and right aortic arches. Because the left aortic arch goes directly to the gut, the shunting of oxygen depleted blood which is high in CO
2 may serve to aid in creating stomach acid to assist in digesting bones from its prey. Their blood has been shown to have strong antibacterial properties.
Crocodilians have lungs with
alveoliAn alveolus is an anatomical structure that has the form of a hollow cavity. Found in the lung, the pulmonary alveoli are spherical outcroppings of the respiratory bronchioles and are the primary sites of gas exchange with the blood. Alveoli are particular to mammalian lungs...
. They have a unique muscle called the diaphragmaticus that attaches to the
liverThe liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and
visceraIn anatomy, a viscus is an internal organ of an animal , in particular an internal organ of the thorax or abdomen. The viscera, when removed from a butchered animal, are known collectively as offal...
and acts as a piston to assist in breathing. The diaphragmaticus is not
homologousIn evolutionary biology, homology refers to any similarity between characteristics of organisms that is due to their shared ancestry. The word homologous derives from the ancient Greek ομολογειν, 'to agree'. There are examples in different branches of biology...
to the
diaphragmIn the anatomy of mammals, the thoracic diaphragm is a sheet of muscle extending across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
of mammals and the proto-diaphragm of tegu lizards. Like other
amnioteThe amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They include mammals, birds and reptiles, as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes. In humans,...
s, crocodilian breathing uses muscles between the ribs to both increase and decrease thoracic volume. In addition,
expirationExhalation is the movement of air out of the bronchial tubes, through the airways, to the external environment during breathing....
is accomplished by contracting muscles to move the liver towards the head to rotate the pubic bones to decrease abdominal volume.
InspirationInhalation is the movement of air from the external environment, through the air ways, and into the alveoli.Inhalation begins with the onset of contraction of the diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure according to Boyle's Law...
involves contraction of the diaphragmaticus muscle to push organs to the back of the body and other muscles to make space for these organs. In crocodilians, expiration is mostly passive (involves little muscle contraction) during rest while inspiration always involves muscle contraction. Because many of these ventilatory muscles are used for maneuverability in water, and because the muscles were originally used for locomotion, it is possible that these muscles became ventilatory muscles after they evolved to move air around in the lungs for maneuverability.
Crocodylians are known to swallow stones, gastroliths ("stomach-stones"), which act as a ballast in addition to aiding post-digestion processing of their prey. The crocodiylian stomach is divided into two chambers; the first one is described as being powerful and muscular, like a bird gizzard. This is where the gastroliths are found. The other stomach has the most acidic digestive system of any animal, and it can digest mostly everything from their prey; bones, feathers, and horns.
The sex of developing crocodilians is determined by the incubation temperature of the eggsTemperature-dependent sex determination is a system in which the temperature of neighboring eggs determines the sex of the organism that hatches. It is most prevalent and common among amniote vertebrates that are classified under the reptile class, but is also used among some birds, such as the...
. This means crocodilians do not have
geneticGenetics, , a discipline of biology, is the science of heredity and variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding...
sex determinationA sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual...
, but instead have a form of environmental sex determination which is based upon the temperature embryos are subjected to early in their development.
Sensory organs
Like all reptiles, crocodilians have a relatively small brain, but it is more advanced than in other reptiles. Among other things they have true
cerebral cortexThe cerebral cortex is a structure within the brain that plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It constitutes the outermost layer of the cerebrum. In preserved brains, it has a grey color, hence the name "grey matter"...
es.
As in many other aquatic or amphibious tetrapods, the eyes, ears, and nostrils are all located on the same plane. They see well during the day and may even have color vision, plus the eyes have a vertical, cat-like pupil which also gives them excellent night vision. The iris is silvery and a light reflecting layer of tapetum behind the retina greatly increases their ability to see in weak light and also makes their eyes glow in the dark. A third transparent eyelid, the
nictitating membraneThe nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten the eye while also keeping visibility...
, protects their eyes underwater. However, they cannot focus under water, meaning other senses are more important when submerged.
While birds and most reptiles have a ring of bones around each eye which supports the eyeball (the
sclerotic ringSclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...
), the crocodiles lack these bones, just like mammals and snakes. The eardrums are located behind the eyes and are covered by a movable flap of skin. This flap closes, along with the nostrils and eyes, when they dive, preventing water from entering their external head openings. The middle ear cavity has a complex of bony air-filled passages and a branching
eustachian tubeThe Eustachian tube is a tube that links the pharynx to the middle ear. In adults the Eustachian tube is approximately 35 mm long. It is named after the sixteenth century anatomist Eustachius...
. There is also a small muscle (which is also seen in
geckosGeckos are small to average sized lizards belonging to the family Gekkonidae, found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. An estimated 2,000 different species of geckos exist...
) next to or upon the stapes, the stapedius, which probably functions in the same way as the mammalian stapedius muscle does, damping strong vibrations.
The upper and lower jaws are covered with sensory pits, visible as small, black speckles on the skin, the crocodilian version of the lateral organ seen in fish and many amphibians, though arising from a completely different origin. These pigmented nodules encase bundles of nerve fibers that respond to the slightest disturbance in surface water, detecting vibrations and small pressure changes in water, making it possible for them to detect prey, danger, and intruders even in total darkness. These sense organs are known as DPRs (Dermal Pressure Receptors). While
alligatorAn Alligator is a crocodilian in the genus Alligator of the family Alligatoridae. The name alligator is an anglicized form of el lagarto the Spanish term for "lizard", the name by which early Spanish explorers and settlers in Florida called the alligator...
s and
caimanCaimaninae are one of two subfamilies of the family Alligatoridae.The list of species:* Subfamily Caimaninae** Genus Necrosuchus ** Genus Eocaiman ** Genus Paleosuchus...
s only have them on their jaws,
crocodileA crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
s have similar organs on almost every scale on their body. The function of the DPRs on the jaws are clear, but it is still not quite clear what the organs on the rest of the body in crocodiles actually do. They are probably doing the same as the organs on their jaws, but it seems like they can do more than that, like assisting in chemical reception or even salinity detection.
Skin and skeleton
The skin is covered with non-overlapping scales composed of the protein
keratinKeratins are a family of fibrous structural proteins; tough and insoluble, they form the hard but un-mineralized structures found in reptiles, birds, amphibians, and mammals...
(the same protein that forms hooves, skin, horns, feathers, hair, claws, and nails in other tetrapods), which are shed individually. On the head the skin is actually fused to the bones of the skull. There are small plates of bone, called
osteodermOsteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and Nanchangosaurus...
s or scutes, (mainly referred to as osteoderms) under the scales. Like the scales comprising the shell of a turtle, or the cross-section of a tree trunk, crocodile osteoderms have annual growth rings, and by counting them it is possible to tell their age. Osteoderms are found especially on the back, and in some species also on the belly. The rows of scutes cover the crocodile's body from head to tail, forming a tough protective armor. Beneath the scales and osteoderms is another layer of armor, both strong and flexible and built of rows of bony overlapping shingles called osteoscutes, which are embedded in the animal's back tissue. The blood-rich bumpy scales seen on their backs act as solar panels.
Their spool-shaped vertebrae in their ancestors went from being biconcave to having a concave front and a convex back in the modern forms. This made the vertebral column more flexible and strong.
They possess ribs of dermal origin restricted to the sides of the ventral body wall. The collar bone (clavicle) is absent.
Differences between alligators and crocodiles
While alligators are often confused with crocodiles, they belong to two quite separate taxonomic families.
The most obvious external differences are visible in the head—alligators have wider and shorter heads, and a more U-shaped than V-shaped snout. The alligator's upper jaw is wider than its lower jaw, and the teeth in the lower jaw fit into small depressions in the upper jaw. The upper and lower jaws of the crocodiles and caimans are the same width, and teeth in the lower jaw fall along the edge or outside the upper jaw when the mouth is closed. When the crocodile's mouth is closed, the large fourth tooth in the lower jaw fits into a constriction in the upper jaw. For hard-to-distinguish specimens, the protruding tooth is the most reliable feature to define a species.
Alligators lack the jagged fringe which appears on the hind legs and feet of the crocodile and have the toes of the hind feet webbed, not more than halfway to the tips. Alligators strongly prefer
freshwaterFreshwater is naturally occurring water on the surface such as bogs, ponds, lakes, rivers and streams, and underground in aquifers and underground rivers. Freshwater is characterized by having low concentrations of dissolved salts...
, while crocodiles can better tolerate
seawaterSeawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every of seawater has approximately of dissolved salts...
due to specialized glands for filtering out salt. However, both taxa can survive in either.
Both species of alligator also tend to be darker in color than crocodiles—often nearly black (but color is very dependent on water quality). Algae-laden waters produce greener skin, while
tannic acidTannic acid, a specific commercial form of tannin, is a polyphenol. Its weak acidity is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, but in fact it contains a mixture of related...
from overhanging trees can produce often darker skin.
When cleaning alligator pools, some zookeepers can tread on alligators without eliciting a response, though crocodiles almost invariably react aggressively and are for the most part more aggressive in their natural habitat.
Evolution and classification
EusuchiaEusuchia is a clade of crocodylomorphs that first appears in the Early Cretaceous with Hylaeochampsa. All living crocodilian species are eusuchians, as are many extinct forms.-Description:...
, a modern
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
which includes the
crown groupA crown group is the smallest monophyletic group, or "clade", to contain the last common ancestor of all members, and all of that ancestor's descendants...
Crocodilia, first appeared in the Lower Cretaceous of Europe.
IsisfordiaIsisfordia is an extinct genus of crocodilian that lived during the Middle Cretaceous . Its fossils were discovered in the Winton Formation in Isisford, Queensland, Australia in the mid 1990s...
duncani lived approximately 95 to 98 million years ago, during the
CenomanianThe Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
epoch of the Upper Cretaceous.
Isisfordia is the second oldest known eusuchian, and the earliest
crocodylomorphThe Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
yet found in Australia. Eusuchians underwent a mass radiation during the Late Cretaceous and the Paleogene, in which they evolved into numerous forms, such as semi-aquatic dinosaur-eating species (
DeinosuchusDeinosuchus is an extinct relative of the alligator that lived 80 to 73 Ma , during the Late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek δεινός/deinos and σουχος/soukhos...
); hooved, terrestrial carnivores (
PristichampsusPristichampsus is an extinct genus of crocodylian that grew to approximately three metres in length.Several remains of Pristichampsus have been found around the world, including P. rollinatii, the type species from the Lutetian of France; and P. vorax from the Middle Eocene of Wyoming and West...
), and 'hatchet'-shaped skulled forms (
BaruBaru was an extinct genus of Australian mekosuchine crocodilian. It was semi-aquatic, around 4 m in length. Being semi-aquatic its habitat was around fresh pools of water in wet forests, ambushing their prey, much like modern species...
).
Taxonomy
- Superorder Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
- Order Crocodilia
- Superfamily Gavialoidea
- Family Gavialidae
Gavialidae is a family of reptiles within the order Crocodilia. Gavialidae consists of only two surviving species, the gharial and the false gharial , which are each the sole living representatives of their genera...
: gharials & false gharials
- Superfamily Alligatoroidea
Alligatoroidea is a superfamily of crocodilians that evolved in the Late Cretaceous period. Cladistically, it is defined as Alligator mississippiensis and all crocodylians more closely related to A. mississippiensis than to either Crocodylus niloticus or Gavialis gangeticus ....
- Family †Diplocynodontidae
- Family Alligatoridae
Alligators and caimans are archosaurs, species of crocodilians and form the family Alligatoridae .- True alligators :...
- Subfamily Alligatorinae
Alligatorinae are one of two subfamilies of the family Alligatoridae.-Taxonomy:* Subfamily Alligatorinae** Genus Albertochampsa ** Genus Chrysochampsa ** Genus Hassiacosuchus...
: alligators
- Subfamily Caimaninae
Caimaninae are one of two subfamilies of the family Alligatoridae.The list of species:* Subfamily Caimaninae** Genus Necrosuchus ** Genus Eocaiman ** Genus Paleosuchus...
: caimans
- Superfamily Crocodyloidea
- Family Crocodylidae
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
- Subfamily †Mekosuchinae
Mekosuchinae was a subfamily of crocodiles from Australia and the South Pacific that have now become extinct. They first appear in the fossil record in the Eocene in Australia, and survived until the Pleistocene in Australia and until the arrival of humans in the Pacific islands of Fiji, New...
- Subfamily Crocodylinae
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
: crocodiles
Phylogeny
CladogramCladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry...
after Brochu (1997).
In popular culture
- Several science fiction movies have giant crocodilians as their stars, such as Alligator
Alligator is a 1980 monster movie, directed by Lewis Teague with a screenplay by John Sayles. It stars Robert Forster, Robin Riker, and Michael V. Gazzo...
, Lake PlacidLake Placid is a 1999 American/Canadian monster movie with elements of comedy, horror, romance and the buddy genre. It was written and produced by David E. Kelley, directed by Steve Miner, and stars Bill Pullman, Bridget Fonda, Brendan Gleeson, Oliver Platt, and Betty White...
, Primeval, DinoCrocDinocroc is a 2004 horror film, starring Charles Napier and Joanna Pacula about a prehistoric carnivore, Sarcosuchus imperator.- Plot :...
, and RogueWar is a 2007 action/thriller film, directed by Phillip G. Atwell who makes his film debut, with fight choreography by Corey Yuen. The film was released in North America on August 24, 2007, and was rated R by the MPAA for "sequences of strong bloody violence, sexuality/nudity and language"...
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