DESCRIPTION OF THE CLASS ARCHOSAUROMORPHA (HUENE 1946)

EUKARYA> UNIKONTA> OPISTHOKONTA> ANIMALIA> BILATERIA> DEUTEROSTOMATA> VERTEBRATA> GNATHOSTOMATA> TETRAPODA> AMNIOTA> ARCHOSAUROMORPHA

Archosauromorpha (ar-ko-SOR-o-MOR-fa) is made up of three Greek roots that mean “ancient lizard forms” [ancient- archaios (αρχαίος), lizard- savra (σαύρα), and form- morphi (μορφή)]. The reference is to the ancient lizards (i.e. dinosaurs) that make up most of the members of this class. Originally, the name was created by von Huene (1946) to define this group of diapsid reptiles.

INTRODUCTION TO THE ARCHOSAUROMORPHA This group of vertebrates is remarkably diverse and has exploited environments on the land, water, and air since its appearance in the upper Permian (251-299). This monophyletic group of diapsids is sister to the Lepidosauromorpha and includes crocodilians, pterosaurs, rhynchosaurs, dinosaurs, and birds (see Figures 1-A and 1-B). Although the basal archosaurs were somewhat sprawling and lizard-like, many evolved a more upright and bipedal stance. The synapomorphies that unite this class are a posterodorsal process on the premaxilla, a sagittal crest, slender cervical ribs that taper, a notch on the anterior margin of the interclavicle, and an iliac blade with a small anterior process and larger posterior process (Benton 2005). In addition, they had a distinctive concave-convex articulation between the ankle bones (astragalus and calcaneum) and teeth in sockets in the jaw (Pough et al. 2009). Two different groups, the pterosaurs and the birds, independently evolved the ability of true powered flight.

A.	FIGURE 1.A. A cladogram illustrating the relative position of the Archosauromorpha within the tetrapod clades according to Benton (2005).
B.	CLADES OF THE ARCHOSAUROMORPHA 1. RHYNCHOSAURIA, THE BASAL ARCHOSAURS 2. CROCODILIANS 3. PTEROSAURS 4. DINOSAURS 5. ORNITHISCHIANS 6. SAURISCHIANS 7. SAUROPODS 8. THEROPODS 9. THE BIRDS
FIGURE 1.B. A cladogram showing relationships between Archosaurian groups with Lepidosauromorpha as the outgroup. The polytomies in this figure illustrate our limited knowledge at this point regarding major groups of non-avian dinosaurs. The cladogram was constructed using Pough et al. (2009), Benton (2005), Rauhut (2003), Clark et al. (2002), Yates (2003), Wilson (2002), Sereno (1986; 1999), Cracraft (1988), Cracraft et al. (2004), and Chiappe (2002).

Rhynchosauria, the basal Archosauromorphs (Figure 1 Clade 1) The Rhynchosauria (from two Greek roots that mean beaked lizards) include a collection of basal taxa that first appeared in the upper Permian and died out in the Triassic. The earliest rhynchosaurs were carnivores which appeared in the Permian and resembled long-necked lizards. Protorosaurus (Figure 2) is typical of those early rhynchosaurs and may have been semiaquatic, adapted to catching fish. The other groups of rhynchosaurs appeared in the Triassic and were somewhat derived terrestrial herbivores with horny beaks, adapted to feeding on tough plant material. Hyperodapedon (Figure 3) had specialized shearing teeth in the cheek region (two rows), a beak with a large overbite, and hind feet with specialized claws that seem to have functioned in digging. Almost certainly, these basal taxa, called here Rhynchosauria, are paraphyletic.

FIGURE 2. Protorosaurus, a long-necked rhynchosaur from the upper Permian. ©Arthur Weasley Wikipedia	FIGURE 3. Hyperodapedon, a strange basal Archosauromorph that was a herbivore. Notable adaptations included a distinctive narrow beak, specialized cheek teeth, and hind claws adapted to digging. ©Arthur Weasley Wikipedia

Euparkeria and the The Crocodilian Clade (Figure 1 Clade 2) By the middle of the Triassic (199-251), animals appeared that had all of the Archosaur characters. These synapomorphies included: a skull with a large fenestra between the orbit and the nostril, a fenestra at the posterior of the lower jaw, and laterally flattened teeth, usually with serrations (Benton, 2005). Euparkeria (Figure 4), a Triassic carnivore, embodied the synapomorphies. Furthermore, its hind legs were longer than the front in such a way that suggested it could function as a quadriped and as a biped. The crocodilian line, also called the Crurotarsi, is defined by having an ankle that rotates whereas most of the other archosaurs evolved a simpler hinge-like ankle joint. The early crocodilians radiated to semi-aquatic dorsoventrally flattened forms as well as fully terrestrial forms that were bipedal and looked like theropod dinosaurs. Within the crocodilians, some taxa became herbivores, but these were in the minority. By the middle Jurassic (145-199), the neosuchian line, the line that had the familiar crocodilian body form, had become established. The neosuchian crocodilians returned to a semi-aquatic existence (Figures 5 and 6). Thus, they returned to the familiar sprawling, lizard-like stance with a deep, flattened tail for propulsion in the water. The once diverse group has been reduced to 23 species, which tend to be the top predators of tropical and subtropical wetlands.

FIGURE 4. Euparkeria, a stem Archosaur from the middle Triassic. Image from: http://www.ucmp.berkeley.edu/diapsids/images/euparkeria.jpg	FIGURE 5. Photo of a crocodile in Costa Rica. Systematic Biology Diversity Archive.	FIGURE 6. Photo of an American Alligator in Florida. Systematic Biology Diversity Archive.

The Pterosaur Clade (Figure 1 Clade 3) Pterosaurs (Figures 7 and 8; the name is from two Greek roots meaning “winged lizard”) evolved true powered flight on outstretched bat-like wings during the Triassic Period. The skin was stretched tight and supported by an elongated fourth finger. Although thin, the skin of the wings, was strengthened by bands of collagen fibers. Traces of hair on the bodies of some pterosaur fossils suggests that they were endothermic. Thus, their presumed physiology and wing structure support the view that they were strong and agile fliers. The earliest pterosaurs (upper Triassic to lower Cretaceous) like Rhamphorhynchus (Figure 7) had long tails, which likely functioned in balance and steering during flight. The mouth was filled with many sharp needle-like teeth, suggesting that they were fish-eaters. The pterodactyloideans evolved through the Cretaceous and were distinguished by having no tail and highly modified dentition, sometimes with no teeth at all. These later pterosaurs seem to have occupied many more ecological niches and may have fed on more than fish. Although Pteranodon (Figure 8) grew to be very large (a wingspan of 2 meters and a body mass of about 15kg) and fed on fish, its relative, Quetzacoatlus, a true giant with a wingspan of 13-15 meters and a mass of around 90kg, seems to have been a hunter (or scavenger) of large terrestrial animals. The pterosaur line persisted until the end of the Cretaceous and disappeared during the end Cretaceous mass extinction. Benton (2005) summarizes the prevailing view that the Pterosaurs are the major sister group to the Dinosauria. That view grew from a supposition of similarities between the two groups, particularly the bipedal stance which is common to the two groups. Bennett (1996a), however, applied a cladistic analysis to the Pterosaurs and other Archosauromorphs and concluded that while the pterosaurs are embedded within the Archosauromorpha, they appear to have been the sister group to Euparkeria and the Crocodilian line.

FIGURE 7. An illustration of Rhamphorhynchus in a dive. © John Conway Wikipedia.	FIGURE 8. A Pteranodon in flight. Image taken from: http://www.nmnh.si.edu/paleo/PaleoArt/Historical/Highlights/pterosaur.html

The Dinosaur Clade (Figure 1 Clade 4) Dinosaurs (from two Greek roots meaning “terrible or awe-inspiring lizard”), or, more appropriately, the non-avian dinosaurs, appeared during the Triassic Period as small bipedal carnivores, and they formed two large groups defined by the structure of the pelvic girdle: the Saurischia (“lizard-hipped dinosaurs”) and the Ornithischia (“bird-hipped dinosaurs) that flourished in the Jurassic (144-208 mya) and Cretaceous (66-144 mya) Periods. Soreno (1999) suggests that although the ornithischia may be monophyletic, the saurischia is paraphyletic and the lines of the sauropods and theropods are independent of each other. Much ink has been spilled on determining the synapomorphies of the Dinosauria. Weishampel et al. (1990), Soreno (1999), and Benton (2005) all emphasize a few characters that include: – longer hind legs than front legs – the skeleton and musculature of the hind legs that causes them to be underneath the body rather than splayed, including the distinct offset head and ball of the femur – a reduction of the digits in the manus and pes (usually to 3 or 4) – an acetabulum, hip joint, that has a hole in the center – a sacrum of at least 3 fused vertebrae – a reduced fibula – a crest that runs much of the way down the humerus for the attachment of the deltoid and pectoral muscles

The Ornithischian Dinosaur Clade (Figure 1 Clade 5) The Ornithischia, the bird-hipped dinosaurs, were entirely herbivorous and included the armored ornithischians (thyreophores – “shield-bearers”), the ornithopods (bird-footed dinosaurs; Figure 9), and the horned ornithischians (ceratopsians- “horn-faced dinosaurs”). The thyreophores were quadrupedal animals with small heads, short necks, and large bodies on pillar-like legs. Their bodies were covered by nodules of bony armor or plates and most had defensive spikes or clubs on the ends of their tails. Some of the principle taxa included Stegasaurus and Ankylosaurus. The ornithopods remained bipedal or facultatively bipedal. The principle distinguishing feature of the head was the evolution of batteries of cheek teeth that were inset, suggesting that they had a cheek and could masticate plant material much like a cow does. Most evolved a beak in the front of the jaw, which gave them the name, duck-billed dinosaurs. Complex crests that may have served as resonating chambers on many taxa point to the likelihood of communication by sound, a characteristic of highly social vertebrates. Indeed, evidence suggests that all of the dinosaurs lived in social groups. The ceratopsians appeared as bipedal animals in the lower Cretaceous, but most evolved to become large quadrupeds by the middle of the Cretaceous. They were characterized by having an anterior shearing beak, the back of the skull expanded into a frill, and one or more horns on the face and/or frill. Common taxa included Protoceratops and Triceratops (Figure 10).

FIGURE 9. Painting of an ornithopod hadrosaur, a member of the ornithischian dinosaurs. The animal has a bipedal stance, but it can also move about as a quadruped. Image taken from: http://www.copyrightexpired.com/earlyimage/prehistoriclifebeforekt/hadrosaurus01.html	FIGURE 10. An image of Triceratops, which was an obligate quadruped. © Arthur Weasley Wikipedia

The Saurischian Dinosaur Clade: Sauropods and Theropods (6-8) The Saurischia include the theropods and sauropods, the most popular of the dinosaurians. The sauropods (“lizard-footed dinosaurs”; Sauropodomorpha) included herbivorous taxa that returned to a quadrupedal stance and included the largest terrestrial vertebrates that have ever lived (e.g. Apatosaurus, Camarasaurus, Brachiosaurus, and Diplodocus; Figure 11). Typically, they had long necks, small heads, immense bodies on pillar-like legs, and long tails. In overall structure, they resembled bridges that walked. Sauropods had weak teeth that could do little more than tear away plant stems, leaves, twigs, etc., but did allow them to consume large masses of food that they ground up in a stone-filled gizzard and further processed in large fermentation chambers. The Theropoda (“beast-footed dinosaurs”), retained many of the characters of the oldest dinosaurs. Specifically, they remained bipedal and carnivorous. Taxa included Tyrannosaurus, Coelophysis, Velociraptor, and Troodon. Tyrannosaurus some of its relatives in the upper Cretaceous were the largest terrestrial carnivores ever to walk the earth. Through the long evolution and diversification of the theropods, one of the principle variable structures was the forelimbs, including the manus. The variation can be seen in a number of Cretaceous taxa which have highly reduced forelimbs (e.g. Tyrannosaurus), a regular forelimb but a manus reduced to a single digit (e.g. Mononychus), and a manus with long fingers (e.g. Velociraptor). Some of these taxa likely had feathers. Indeed, the reconstruction of Deinonychus (Figure 12) shows a very bird-like animal covered with feathers. The resemblance to birds is more than superficial. In fact, from a cladistic perspective, all birds are embedded within the theropods (Weishampel et al. 1990, Soreno 1999, Benton 2006, and Brochu and Norell 2001).

FIGURE 11. Diplodocus, one of the giant sauropods had pillar-like legs, an enormous body, and long neck and tail. As illustrated here, the animals likely walked with their tails elevated, which served as a counterbalance. © Arthur Weasley Wikipedia	FIGURE 12. Deinonichus was a theropod dinosaur, which likely had many bird-like characters, including a feathered body. © Arthur Weasley Wikipedia

MAJOR CLADES OF AVES THE BIRDS 9. PYGOSTYLIA 10. NEORNITHES 11. PALEOGNATHAE 12. NEOGNATHAE 13. GALLOANSERES 14. NEOAVES 15. COLUMBEA 16. PASSEREA 17. AEQUORNITHIA 18. TELLURAVES 19. AFROAVES 20. AUSTRALAVES 21. AUSTRALAVES

FIGURE 13. MAJOR CLADES OF AVES (BIRDS). This is a continuation of Figure 1.B. and expands the relationships between the major groups of birds, particularly the extant groups. Note that Theropods form the outgroup and these clades are all nested within clade 4 (Figure 1.B.), the Dinosaur clade. This cladogram is an interpretation of Jarvis et al. (2014) and Zhang et al. (2014) with modifications according to Pough et al. (2009), Benton (2005), Rauhut (2003), Clark et al. (2002), Yates (2003), Wilson (2002), Sereno (1986; 1999), Cracraft (1988), Cracraft et al. (2004), and Chiappe (2002).

Birds (Figure 1 Clade 9) and Figure 13 Birds are the most successful of all living tetrapods with more than 9,500 living species. They are characterized by having a body covered with feathers, a light skull with no teeth, a highly reduced tail, and thoracic/lumbar vertebrae that are fused. They retain the bipedal stance and foot structure characteristic of their theropod ancestors with the forelegs modified into wings that form airfoils made of relatively long flight feathers. Within this basic body plan, living birds show remarkable diversity in which they have exploited aerial environments as well as terrestrial, arboreal, and aquatic environments.

Extinct Bird Groups (Figure 13): Archaeopterygidae and Ornithothoraces Animals that clearly were birds appeared in the fossil record in the upper Jurassic. Archaeopteryx (Figure 14; old or first wing) was one of the first to be discovered and remains one of the oldest birds. In almost all details, Archaeopteryx was a small theropod with a long, bony tail, a mouth with small sharp teeth (rather than a beak), a manus with long narrow fingers, and a hind foot (ped) in which toe 1 is reflexed. Indeed, compare it with the reconstruction of Deinonychus (Figure 12). The primary distinction is that Archaeopteryx and its relatives had flight feathers. Ostrom’s (1976) proposal that there was a connection between birds and dinosaurs was met with enthusiasm. However, the enthusiasm began to be tempered by apparent paradox that most of the theropods from which the birds could have arisen came after Archaeopteryx. This problem of the temporal paradox lent support to an early thecodont precursor to the birds (e.g. Feduccia and Wild 1993, Burke and Feduccia 1997, and Feduccia and Martin 1996). Brochu and Norell (2001) convincingly laid this argument to rest by investigating most of the published cladistic analyses and arguing that the temporal paradox is an artifact of looking at sister groups and assuming that one was an ancestor, a common problem for those unused to interpreting cladistic analyses. In fact, relatives of Archaeopteryx, primitive birds, persisted well into the Cretaceous. Now, there are no other serious objections to the thecodont-bird connection. By the lower Cretaceous (65-145), birds began to appear with beaks, a reduced tail, and a fused synsacrum, all characters of modern birds. The tail became reduced in most to a fused structure called a pygostyle, a character of all modern birds. The pygostyle is such an important synapomorphy that a presumed dinosaur called Ovoraptor, which had a toothless skull and a pygostyle, has been reclassified with the birds. This clade, including Ovoraptor, is called Pygostylia. Other birds, mostly in the Superorder Ornithothoraces, were otherwise in form but retained teeth. These Cretaceous birds diversified into animals that appeared to be tern-like, and other aquatic toothed birds like Hesperornis (Figure 15) were flightless with strong legs placed well back on the body; presumably, they were strong swimmers. Another Cretaceous-era flightless bird, Patagonopteryx, was a land animal with adaptations for running, an ecological equivalent to the ratites (but not directly related to them). Modern birds (clade 11) are the Neornithes. They are nested within the Pygostylia

Neornithes (Figure 13 Clade 11) All birds alive today are in this clade. The most obvious character that they have in common is the absence of teeth. They appeared more than 100 MYA in the Cretaceous (Jarvis et al. 2014).

Paleognathae (Figure 13 Clade 12) Members of the Paleognathae are defined by having a palate that is robust and theropod-like. In addition, those that are alive today, a group called the Ratites, are almost entirely flightless. The largest living ratites are the Ostriches (Figure 16), flightless birds that are up to 3 meters tall and nearly 200kg. These animals have almost completely lost their wings. They have long legs, well adapted to running (>50-70km/hr), and feet with only two toes, one of which has a large claw. They also produce the largest eggs of any birds. All ratites (including Kiwis, Cassowaries, Emus, and Rheas, and Tinnamous) have a southern continental distribution, which suggests that they evolved on Gondwanaland before it broke apart.

FIGURE 14. A feathered life-sized model of Archaeopteryx from the Natural History Museum in St. Petersburg, Russia. The Systematic Biology Diversity Archive.	FIGURE 15. A restoration of Hesperornis regalis, a flightless aquatic bird from the Cretaceous. This bird had teeth and could not walk. Image by Nobu Tamura	FIGURE 16. Ostriches, male (left) and female (right). © Andrew Massyn Wikipedia

The Neognathae (Figure 1 Clade 13) The Neognathae include almost all of the extant birds. The neognath palate is gracile and highly modified from the paleognath condition. They have a keeled sternum and a characteristic ankle in which the calcaneum, not the astragulus (as in the ratites and theropods) forms the ascending process on the tibia.

Galloanseres (Figure 13 Clade 14) The Galloanserae is a sister clade to all other neognaths (Neoaves) and is made of two large, and economically important orders: Anseriformes and Galliformes. The Anseriformes are aquatic birds that include ducks, geese, and swans. In general, they are relatively large birds with long necks, short tails, and webbed feet. The diets range from aquatic and terrestrial plants to aquatic invertebrates and fish. The Wood Duck (Figure 17) is a small omnivorous perching duck that nests in tree holes. Its food includes aquatic plants, acorns, and invertebrates. The Galliformes are fowl like Pheasants, Quail, Grouse, Turkey, and Megapodes. Most of them are ground-dwelling and good fliers but only in short bursts. Thus, they usually are not migratory. Megapodes are birds of forests and woodlands in tropical and subtropical Australia, New Guinea, and Philippines. They are unusual in that they construct remarkable incubation mounds in which the eggs are incubated by the heat from rotting vegetation. The origin of the domestic chicken (Gallus gallus or Gallus domesticus) is disputed as to the time and place of the domestication. Blench and MacDonald (2000) indicate that the chicken may have been a result of the domestication of the Red Junglefowl (Figure 18; G. gallus) somewhere in India or South-East Asia. The domestication event likely was earlier than 6,000 BCE.

FIGURE 17. A Wood Duck in summer plumage. Systematic Biology Diversity Archive.	FIGURE 18. Red Junglefowl (Gallus gallus) in Thailand. This is the animal that gave rise to the domestic chicken. Image by: Jason Thompson; Creative Commons License.

Neoaves (Figure 13 Clade 15) The separation of the Neoaves and Galloanseres occurred in the upper Cretaceous (Jarvis et al. 2014). Neoaves includes two large but unequal clades (Columbea and Passerea) that diverged near the KT boundary.

Columbea (Figure 13 Clade 16) This grouping of unlikely cousins was discovered by the full genome analysis of Jarvis et al. (2014). It includes two superorders: Phoenicopterimorphae and Columbimorphae. Phoenicopterimorphae The Flamingo-Grebe Clade is made of two orders that have birds that look very different from each other. Flamingos (Figure 19) are tall, long-legged wading birds with a beak specially adapted to sift through bottom mud for algae and invertebrates of tropical and subtropical lakes and ponds, many of which are hypersaline. Grebes, on the other hand are small to medium-sized compact birds of temperate waters and resemble loons. Columbimorphae The Columbiform Clade also is made of three orders, but only Columbiformes (pigeons and doves) is globally abundant. The Rock Dove (Figure 20) has become an almost constant companion of human habitations; they are especially common in cities. The Dodos and Solitaires, extinct island pigeons that grew to be very large and flightless were brought to extinction about 500 years ago by European seafarers.

FIGURE 19. Flamingos (Flamingo jamesi) feeding. Image by Valdiney Pimenta.	FIGURE 20. Photo of a common Rock Dove (Columba livia), native to the Eastern Hemisphere and an exotic in the Americas, is a common resident of cities throughout the world. Image by Alan Wilson; Creative Commons License.

Passerea (Figure 13 Clade 17) This is a large clade that contains two nested basal clades Caprimulgimorphae + Otidimorphae and Cursorimorphae + Opisthocomiformes and two large groupings: Aquiornithia (the core waterbird assemblage) and Telluraves (the core land bird assemblage). The basal groups are enclosed in brackets in Figure 13. Otidimorphae The Cuckoo Clade (order Cuculiformes) is global. These birds have long, curved beaks, zygodactyl feet, and long tails. The roadrunner, a ground-dwelling cuckoo, eats snakes and lizards. The arboreal species tend to feed on caterpillars. The Old World cuckoos (Figure 21) are nest parasites and lay eggs in the nests of smaller birds. The Turaco Clade is made of a single family called Musopagiformes, which means banana-eaters. These birds have crests, long tails, zygodactyl feet, and are brightly-colored. They are birds of southern Africa and usually allied with the cuckoos. Caprimulgimorphae The Apodiform-Goatsucker Clade includes the Swifts, Hummingbirds, and Goatsuckers. Members of this group are found globally, but primarily in the tropics. Those of the temperate zone s tend to be migratory. The swifts and hummingbirds are small birds. Indeed, hummingbirds are the smallest birds and can be no longer that 7 cm and weigh less than 2-5 g. They feed on nectar and can hover in front of the flower while they feed (Figure 22). Swifts, too, are aerial acrobats and catch insects on the wing. The name apoda means without feet. When they fly or land, their feet are hidden and make them appear to be without feet. Swifts have accommodated well to cities and human dwellings, which serve as a suitable substitute for their native cliffs. Goatsuckers are so-called because they have a very wide mouth, which European farmers of more than a century ago, thought was just suited to suck out all of a goat’s milk over night. They do not feed on milk, but rather are nocturnal and feed on insects. Usually they are heard but rarely seen. Cursorimorphae The Gruiform-Ralliform Clade contains the limpkins, cranes, rails and coots. This is a relatively old group with a fossil history that dates to the Eocene. Cranes are majestic wading birds and among the largest of the birds that can fly. They stand up to 1.75 m and have wingspans up to 2.2 m in flight. They occur on all continents except Antarctica and South America. The majestic Whooping Crane of North America (Figure 23), though still endangered, was saved from the brink of extinction by the U.S. Endangered Species Act. Limpkins are wading birds that are about half the size of cranes and occupy South America, Central America, and the southern US. Rails are small to medium-sized wading birds, usually secretive in their habits. Coots, on the other hand, are mainly aquatic and look like small ducks from a distance. The Shorebird Clade (e.g. plovers, gulls, auks, and snipes) mainly is made up of wading birds, but some have become adapted to an open ocean environment. The Shorebirds have a fossil record that dates back to the upper Cretaceous. Most members of this clade are small to medium-sized wading birds of all continents. In general, the wading birds are small with medium to long legs and beaks that range from being relatively stubby to long and thin. These are the birds that are often seen on the shore running in and out with the advance and retreat of the surf. Most eat insects, crustaceans, or small fish. The oystercatcher is notable in that it has a beak that is long and laterally-compressed which it uses to pry open pelecypods (clams). All are not aquatic. For example, the Stone Curlews (also called Thick Knees) are mainly nocturnal birds of arid, open areas on most continents. Gulls (Figure 24) and Skimmers occur worldwide. Gulls have been very successful at adapting to what humans provide and are frequently seen in agricultural fields and trash dumps. Gulls and Skimmers range from small to moderately-large (0.20-0.78m) birds with wingspans that range from 0.50 to 1.65 m, and they have webbed feet. Gulls, Skuas, and Jaegers are omnivores while terns and skimmers typically catch small fish. Most are migratory. Auks (Murres and Puffins) are birds of the temperate and Arctic seas of the Northern Hemisphere. Auks are small to medium-sized birds (0.15-0.45m) with short necks, tails, and wings. They have webbed feet that are far back on the body. They vary in the forms of their beaks. The Murres have long thin beaks while the Puffins (Figure 25) have a deep beak, both of which are adapted to catching fish. Auklets have short beaks with which they feed on plankton. All of them catch prey by diving and “flying” underwater, much like a penguin. Opisthocomiformes The Hoatzins (Figure 26) are very unusual birds in several respects. Most notably, their young retain claws on the hand of the wing while they are young and flightless. Adult birds are about the size of a turkey and are brightly colored. They are herbivores feeding primarily on leaves; however, they are unusual in that they digest the leaves by microbial fermentation, using the crop like a cow’s rumen. Indeed, an alternate name is stinkbird, a reference to the odor of manure that they emanate. The relationships with other bird orders has been contentious. Jarvis et al. (2014) show an equivocal relationship between Caprimulgimorphae and Cursorimorphae.

FIGURE 21. Photo of a Common Cuckoo (Cuculus canorus), native to the Europe, is a nest parasite of smaller passerine birds. Image by Chris Romeiks; Creative Commons License.	FIGURE 22. Photo of a Ruby-Throated Hummingbird (Archilochus colubris), the common hummingbird of the central and eastern US is a nectar-feeder and important pollinator. Image by US Fish and Wildlife Service and in the public Domain.	FIGURE 23. A Whooping Crane in flight. Image taken from: http://www.fws.gov/northflorida/WhoopingCrane/Crane-Images/flying-wc.jpg
FIGURE 24. A Ring-Billed Gull (Larus delawarensis) flying at Sandy Hook, New Jersey. Image by: Vlad Lazarenko; Creative Commons License	FIGURE 25. Atlantic Puffin (Fratercula arctica) in breeding plumage, Iceland. Image by: Richard Bartz; Creative Commons License	FIGURE 26. Hoatzin adult in Peru. Image taken from: WikiMedia Commons, uploaded by FunkMonk.

Aequornithia (Figure 13 Clade 19) Aequornithia is the Core Waterbird Assemblage with Phaethontomorphae as its sister group. This clade is a collection of taxa, most of which are associated primarily with water. Many are piscivores. Some sift mud or are herbivores. Most of them are opportunistic and take what they can get. Phaethontimorphae Tropicbirds are oceanic birds, usually pelagic, in tropical and subtropical oceans where they feed mainly on squid and flying fish. They are medium-sized (0.38-0.50m) seabirds with wingspans of 0.88 – 1.12 m. Tropicbirds have a pair of long slender tail feathers (up to 0.55 m). Gaviimorphae Loons (also called Divers; Figure 27) are waterbirds of inland or coastal marine waters of the northern Holarctic. They have narrow wings and a body streamlined for swimming underwater with legs that are placed far back on the body, an attribute which makes them clumsy on land. Procellariimorphae The Albatross-Penguin Clade includes some of the most distinctive birds in the world. They, too have a fossil record that goes back to the upper Cretaceous. Albatrosses (Figure 28) and Petrels have distinctive tube-like nostrils. They are birds of the open ocean, and come to land only to nest. Albatrosses are circumpolar in the Southern Hemisphere and also in the northern Pacific. They are very large sea birds (0.71-1.35m) with large wingspans (up to 3.5m) that allow for long sustained gliding flights. They catch their prey, mainly squid, fish, or crustaceans, at the surface or in shallow dives. Petrels and Shearwaters, birds of all of the oceans, are smaller than Albatrosses with wingspans of 0.7 to 1.12 m. Penguins are among the most distinctive of birds. They have lost the ability to fly, but the wings have been modified into flippers that allow them to “fly” through the water up to 14 km/hr (Figure 29). The body is stout and cylindrical with a uniform covering of feathers. They occur in waters of the Antarctic and sub-Antarctic with some occurring as far north as the Galapagos. Pellicanimorphae The Pelicaniform-Ciconiiform Clade includes pelicans, boobies, cormorants, storks, herons, and egrets, all of which are associated with water. This clade, too, has members that date back to the Eocene. Pelicans (Figure 30) are birds of marine, brackish, and freshwater environments. They are large birds (1.05-1.83m) with wingspans of 2-2.7m. Their most distinctive feature is the gular pouch, an expandable pouch on the lower jaw. Pelicans eat fish caught in their pouch while swimming or plunge diving. Frigate birds or Man o’ War Birds (Figure 31) are commonly found in the open oceans over the earth’s tropical oceans. Birds moderately large (0.70-1.14 m) and a wingspan of 1.7-2.4 m. The bill of the Frigate bird is slightly hooked at the tip, the wings are crooked, and long tail is forked. Females have a white breast, and males are all dark with a distinctive bright red expandable throat patch. They feed over the open ocean on flying fish, squid, jellyfish, and crustaceans. Gannets and Boobies also are oceanic birds that occur from tropical to sub arctic seas. They are moderately large (0.68-1.00m) with wingspans of 1.4 to 1.8m and have a characteristic heavy pointed bill. They can remain at sea for months while feeding on schooling fish and squid. Cormorants and Darters (also called Anhingas or Snake Birds) resemble each other and look like large ducks or geese while swimming in the water. However, they do not oil their feathers like ducks and geese do; so, they become waterlogged after a time and begin to sit low in the water. Cormorants are most visible when, after a bout of fishing, they are seen drying their feathers with outstretched wings (Figure 32). Both Cormorants and Darters eat fish which they catch by a spearing action under water. Cormorants are global in their distribution while Darters occur only in freshwater environments of the tropics and subtropics. Storks (Figure 33) are wading birds of shallow aquatic environments on all continents except Antarctica. They are moderately large (0.75-1.52m) birds with wingspans of about 1.5 m. They fly with their legs and necks extended (as do cranes). Typically, storks have long legs, stout beaks with a curve near the tip, and a naked head. Most are colonial nesters and migratory. Ibises and Spoonbills are wading birds of freshwater, brackish, and coastal marine wetland environments on all continents except Antarctica. They are moderately large (0.45-1.12 m) and have a wingspan of 0.91-1.27 m. They are adapted to wading with long stilt-like legs and distinctive beaks. Ibises have long curved beaks while spoonbills have flattened bills that function to catch prey as it sweeps side to side. Herons, Egrets (Figure 34), and Bitterns are common wading birds of all continents but Antarctica. They are small to large birds (0.28-1.37m) with long legs and long necks. The wingspan ranges from 0.43 to 1.82m. Their heads are relatively small, but the beaks are long and slender, which they use to catch fish and invertebrates with a darting motion.

FIGURE 27. Great Northern Loon (Gavia immer) on a lake in Wisconsin. Image taken by: John Picken; Creative Commons License.	FIGURE 28. Wandering Albatross (Diomedea exulans) in flight over the South Pacific east of Tasmania. Image taken by: J. J. Harrison; Creative Commons License.	FIGURE 29. Gentoo Penguin (Pygoscelis papua) ‘flying’ through the water at the Nagasaki Penguin Aquarium. Image taken by: Ken Funakoshi; Creative Commons License.	FIGURE 30. Brown Pelican (Pelicanus occidentalis). Image taken by: Ianare Sevi; Creative Commons License.
FIGURE 31. Male Magnificent Frigatebird (Fregata magnificens) in flight. Image taken by: Benjamin44; GNU Free Documentation License.	FIGURE 32. Double-Crested Cormorant (Phalacrocorax auritus) drying its wings. Image taken by: WDF; Creative Commons License.	FIGURE 33. White Stork (Ciconia ciconia) in flight near Madrid. Image taken by: Carlos Delgado; Creative Commons License.	FIGURE 34. Snowy Egret (Egretta thula) in flight near Huntington Beach, CA. Image taken by: Regular Daddy; Creative Commons License.

Telluraves (Figure 13 Clade 19) These are the Core Land Birds and they occur in two unequal clades: Afroaves and Australaves. Australaves includes Passerformes, which contains most of the living bird species.

Afroaves (Figure 13 Clade 20) This clade contains two very different superorders: Accipitrimorphae (hawks, eagles, vultures) and Coraciomorphae (e.g. woodpeckers, hornbills, kingfishers), which are bridged by Strigiformes (owls) in an equivocal position between them (Jarvis et al. 2014). Strigiformes The Owl Clade is a monophyletic group of nocturnal birds in a single order, the Strigiformes. In general, there are two types of owls: barn owls, and all other owls. Barn owls (Figure 35) are global in their distribution. They have a heart-shaped, flattened face that helps to gather sound. The other owls are also global as a group with flat faces and distinctive ear tufts. Accipitrimorphae This group includes diurnal raptors exclusive of the falcons, which now appear to be unrelated to hawks, eagles, and vultures. Most systems consider this to contain a single order (Accipitriformes), but some separate the New World Vultures into their own order (Cathartiformes). Hawks and eagles (Figure 36) are raptors that occur on all continents except Antarctica. These are small to large birds (0.20-1.50m) with wingspans of 0.58 to 2m. They have hooked, meat-tearing beaks, and some can capture prey with their talons in flight, usually after diving on the animal. Prey items include all types of vertebrates and some invertebrates. They will also take carrion. They are territorial and usually solitary. Many are migratory. Ospreys are fish-eating birds of shallow waters, freshwater and marine environments on all continents except Antarctica. Ospreys are medium-sized diurnal raptors (0.55-0.58m) that specialize in eating fish. They have a reversible outer toe and spiny foot pads to help grasp fish, which they usually take in an aerial dive. Secretarybirds are raptors of open woodlands and savannahs of Sub-Saharan Africa and are 1.25-1.50m long. They are distinguished by an unmistakable spray of long feather on their heads, long stork-like legs, and long tails giving them the appearance of an eagle with the legs of a crane. They hunt many different types small terrestrial animals (vertebrates and invertebrates) in pairs through their territories. Vultures are carrion-eaters (Figure 37), most of which have featherless heads, presumably this avoids feathers being matted with gore while they are feeding. There is some evidence that the featherless head can serve a thermoregulatory function, too. Old World Vultures (in the Accipitridae with hawks and eagles) and New World Vultures (Cathartidae) are not very closely related despite the amazing similarities. Indeed, this is a remarkable example of convergence. A major difference is that the Old World Vultures locate food by sight and the New World Vultures locate food by sense of smell. The New World Vultures include the condors, which can have wingspans up to 2.8m. Some of the vultures are migratory. The position of the New World Vultures and Condors has been questioned for some years. Sibley and Ahlquist (1990) and Avise et al. (1994) suggest that they are related to storks, but the comprehensive analysis of Jarvis et al. (2014) shows them firmly within the Accipitrimorphae. Coraciimorphae This is a collection of six nested orders of small to medium-sized birds, most of which are arboreal in their habits. Piciformes includes Woodpeckers, Honeyguides, and Toucans. Most members of this taxon are woodpeckers (Figure 38), which have zygodactylous feet, a very long tongue, and a stiff tail that braced the bird while chiseling into a tree. The beaks are used to drill into wood for insects and to hollow out a nest cavity. They are global in their distribution. Mousebirds (Coliiformes) are limited to Africa and resemble very long-tailed cardinals. Trogons (Trogoniformes) are more global, have long tails and a zygodactyl foot in which the inner toe rather than the outer toe rotates. Hornbills (Bucerotiformes) are large birds of tropical Asia and Africa with a beak like a cow’s horn, typically with a crest. The Kingfishers (Coraciiformes) are global in distribution. They have a syndactylous foot (outer and middle toes are fused at the base). They have large heads with a long, stout beaks usually together with distinctive color patterns that include a white band on the neck. Kingfishers inhabit aquatic and forest habitats, but all hunt by diving from a perch to catch fish (by diving) or other vertebrates. The Laughing Kookaburra (Figure 39), a native of Australia, is the largest of the Kingfishers and can be up to 45 cm long.

FIGURE 35. A Barn Owl, a bird with one of the broadest distributions on Earth. Image taken from: http://wdfw.wa.gov/wlm/living/graphics/owl3.jpg	FIGURE 36. Bald Eagle (Haliaeetus leucocephalus) in flight with a fish in its talons on the island of Kodiak. Image taken by: Yathin S. Krishnappa; Creative Commons License.	FIGURE 37. Comparison of vultures from the eastern and western hemispheres. TOP: Turkey Vulture (Cathartes aura), a common New World Vulture. BOTTOM: White-Backed Vulture (Gyps africanus), an Old World Vulture. Top image taken by: Kevin Cole; Creative Commons License. Bottom image taken by: Yathin sk, Creative CommonsLicense.	FIGURE 38. A Pileated Wookpecker. Image from: http://fishandgame.idaho.gov/ifwis/ibt/userfiles/image/photos/800/pileated-woodpecker–tom-munson.jpg	FIGURE 39. The Laughing Kookaburra, the largest of the Kingfishers. ©Fir0002/Flagstaffotos

Australaves (Figure 13 Clade 21) Australaves is a clade that includes Seriemas and Falcons as basal orders together with Passerimorphae. Cariamiformes Seriemas (Figure 40) are terrestrial birds of open woodlands and grasslands of tropical South America. They feed on small terrestrial vertebrates and invertebrates as South American ecological equivalents of secretarybirds. They are considered to be living descendants of the large flightless terror birds, the phorusrhacids (Figure 41), which were the apex predators in South America during most of the Cenozoic Period (Degrange et al. 2010), especially during the 10 million year period following the end Cretaceous extinction event. Falconiformes (sensu stricto) The Falconiform Clade is made up of birds from a single order that dates back to the Eocene. These are the Falcons, which are diurnal raptors that can be found on all continents except Antarctica. They have hooked, meat-tearing beaks, and they capture prey with their talons in flight, usually after diving on the animal. Falcons (Figure 42) prey on other birds in flight.

Passerimorphae: Psitaciformes + Passeriformes Psitaciformes The Parrot Clade is made up of birds of the Psittaciformes. They range in size from small to relatively large birds with a distinctive set of characters: zygodactyl feet, powder down, a large head, and a hooked beak (Figure 43). They are found in all tropics and in temperate regions of South America. Large parrots can live to be very old (>50 years) and can be quite intelligent.

FIGURE 40. Seriema (Cariama cristata) in Brazil. Image by Whaldener Endo; Creative Commons License.	FIGURE 41. A terror bird (Phorusrhacos longissimus), an early Cenozoic top predator in South America. Illustration by Charles R. Knight (1901).	FIGURE 42. A Peregrine Falcon (Falco peregrinus). Image taken from: http://www.in.gov/dnr/public/julaug06/images/jpegs/falcon_2.jpg

Passeriformes (Figure 13 Clade 18) The songbirds or Passerine birds are extraordinarily diverse set of 74 families within a single order, the Passeriformes. This is one of the most speciose orders of vertebrates with around 5,739 species (Barker et al. 2004). Barker et al. (2001) recognized the passerines as having 3 clades: Tyrannida, Corvida, and Passerida. Their cladogram, however, shows only the Tyrannida and Passerida being monophyletic. Barker et al. (2004) returned to the question and identified two large clades: the Suboscines and the Oscines, with the Acanthisittidae (New Zealand Wrens) as the sister group to all other passerines. Still, some like Johansson et al. (2008) have split up the Passerida into at least 5 clades. Barker et al. (2001) and Ericson et al. (2001) present evidence that the passerines evolved in Australia/New Guinea and dispersed first through the Southern Hemispheric Continents (Gondwanaland) in the late Cretaceous. The suboscines have a set of characters including a relatively simple syrinx, a distinctive columella (the small bone in the middle ear), and innate songs (songs that do not have a learned component). The clades within the suboscines are the Funari, Tyranni, and Eurylaimi (Chesser 2003). – The Funari Clade includes Gnateaters, Woodcreepers, Ovenbirds, and Antbirds, all Old World taxa. Cavity nesting seems to be the ancestral state of these families. Furthermore, the ovenbirds and antbirds as conventionally defined, seem to be paraphyletic and polyphyletic, respectively (Chesser 2004). – The Tyranni Clade is represented in the New World by the Tyrant or New World Flycatchers, many of which are cryptic species. They eat insects which they often catch on the wing, in addition to fruit. A distinctive member of this group is the Scissor-Tailed Flycatcher (Figure 44). – The Eurylaimi Clade, although called the Old World Suboscine assemblage, is distributed globally throughout the tropics and is the sister group to the Tyranni + Funari (Barker et al. 2004). Moyle et al. (2006) present molecular and morphological evidence support the monophyly of the group with two monophyletic clades within the Eurylaime: the Broadbills and the Pittas. Morphological characters that define this group are not well understood. The oscines make up the largest assemblage of songbirds. The syrinx, the sound box that is located at the junction of the bronchi (base of the trachea) has a very complex musculature. Some birds in this group can make different sounds from each branch of the syrinx. The songs of these birds have an innate scaffold to which the learned components of the song are added. The assemblages within the oscines are in flux, but they do include several established groupings of families: Corvoidea, Melphagoidea, and Passerida (according to Barker et al. 2004 and Spicer and Dunipace 2004). Earlier systems (e.g. Sibley and Ahlquist (1990) split the Passerida into Passeroidea and Sylvoidea, but most molecular studies have shown that the Sylvoids are polyphyletic. – The Corvoidea Clade is a large collection of families that includes the Corvids (Crows, Jays, Ravens) and Vireos. Crows are among the largest of the passerines birds with Ravens having a wingspan up to 135 cm. Corvids are omnivores, some like the Rook (Figure 45) have specialized somewhat on carrion. Birds of Paradise (Figure 46) are crow-sized with a strong sexual dimorphism in which the males have long, showy feathers and elaborate displays. In part, it was the search for Birds of Paradise that prompted Alfred Russel Wallace to go to the Mollucas. – The Melaphagoidea Clade mostly is a collection of small families, dominated by the Honeyeaters. As the name implies, Honeyeaters feed on nectar and are similar to Hummingbirds. However, they are poor at hovering flight, and most are unable to do it. They occur mainly in Australia and New Guinea. The last clade, the Passerida contains most of the Passerines. Also, it has birds with some of the most elaborate songs. Mockingbirds (Figure 47) can produce two songs at once. Starlings (Figure 48), members of the same family as Mynas, can have elaborate learned vocalizations. Together with the English Sparrow (an Old World Sparrow, Figure 49), Starlings are invasive species that have led to the reduction of many species in North America. The so-called American Sparrows (Figure 50) actually have a global distribution. These birds have stout beaks and typically feed on the ground. The Finches are a large family of small birds, generally evolved to eat seeds. A small population of South American Finches ended up on the Galapagos Islands (Figure 51) where they diversified into large seed-eaters, small seed-eaters, insect eaters, etc., a situation that was not lost on Darwin in The Origin. Swallows (Figure 52) are small birds that usually nest in colonies and occupy open habitats which allow them to dive and turn to catch insects on the wing. The last representative of this order is the Chickadee (Figure 53), a nonmigratory woodland cavity nester, which usually is quite noisy.

FIGURE 43. Photo of a cockatiel, Nymphicus. Image from the Systematic Biology Biodiversity Archive.	FIGURE 44. A Scissor-Tailed Flycatcher. Image taken from: http://www.msstate.edu/org/mos/Images/Scissor-tailed%20Flycatcher.jpg	FIGURE 45. A Rook (Corvus frugilegus) in Central Russia. Systematic Biology Diversity Archive.	FIGURE 46. Raggiana Bird of Paradise (Paradisaea raggiana). Image taken from: http://nationalzoo.si.edu/Animals/Birds/Images/Bigpic/rbop1.jpg © Jessie Cohen
FIGURE 47. Mockingbird (Mimus polyglottos). Image from: http://www.fws.gov/northdakotafieldoffice/images/Northern%20mockingbird.jpg © Ryan Haggerty	FIGURE 48. Starling (Sturnus vulgaris) in breeding plumage. Image from: http://www.nps.gov/archive/whsa/bird%20list/house%20sparrow.jpg	FIGURE 49. In the English-speaking world, this bird is known as House Sparrow or English Sparrow (Passer domesticus). This is an image of a male. Though native to Eurasia, this animal has been successfully transplanted through much of the world becoming an invasive which displaces many native hole nesting birds. Image by Fir0002 and made available through a GNU Free Documentation License.
FIGURE 50. Song Sparrow (Melospiza melodia). Image from: http://www.nps.gov/prsf/naturescience/images/song_sparrow.jpg	FIGURE 51. Small Ground-Finch (Geospiza fulginosa), a Galapagos finch from Espanola Island. Image by: Putneymark; Creative Commons License	FIGURE 52. Barn Swallow (Hirundo rustica) at rest. This is a global species with several subspecies. Image by Malene Thyssen; GNU Free Documentation License	FIGURE 53. Black-Capped Chickadee. Image from: http://dwrcdc.nr.utah.gov/rsgis2/images/Photos/poecatri.jpg

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By Jack R. Holt and Carlos A. Iudica. Last revised: 08/26/2020