THEROPODA - the CARNIVOROUS DINOSAURS

SAURISCHIA

Characters

• distinctly asymmetrical manus with digit II the longest digit [D&R p. 179]
• elongate posterior cervical vertebrae giving a long neck
• large curved claw on thumb (twisted digit I)
• antorbital fenestra well-developed
• large quadratojugal
• temporal musculature extends onto frontal
• triradiate saurischian pelvis (primitive)

The Saurischian pelvis.  Note the open acetabulum and  the anterior (to the left) pubis.  Illustration from O. C. Marsh.  1896.  The dinosaurs of North America.  16th Annual Report, U.S. Geological Survey, pp. 133-244, 84 plates.

CLASSIFICATION OF THE THEROPODA

Superorder Dinosauria
    Suborder Ornithischia
    Suborder Saurischia
        Order Sauropodomorpha
        Order Theropoda
            Eoraptor
            Neotheropoda
                Infraorder CERATOSAURIA
                Infraorder TETANURAE
                    Megalosaurus
                    Spinosauroidea
                    Avetheropoda
                        Carnosauria
                             Allosauridae
                         Coelurosauria
                            Compsognathus,Ornitholestes,Scipionyx, etc.
                            Therizinosauria
                            Arctometatarsalia
                                Tyranosauridae
                                Ornithomimosauria
                            Maniraptora
                                Oviraptosauria
                                Troodontidae
                                Dromaeosauridae
                                Aviale

Ceratosaurus: Illustration from O. C. Marsh.  1896.  The dinosaurs of North America.

THEROPODA

Dinosaurs with a saurischian pelvis and sharp teeth and claws

Synapomorphies

1. kinetic, flexible lower jaw
2. large, ball-shaped occipital condyle provides extra mobility for the head [D&R p. 180]
3.  5 or more sacral vertebrae
4. distal part of tail is stiff
5. digits IV and V of manus (hand) reduced to absent
6. digits II and III of hand elongate
7. phalanges of digit V of foot lost
8. digit I of pes (foot) is reduced and breaks contact with ankle
9. thin-walled, hollow limb bones and vertebrae
10. Lachrymal bone is prominently exposed on dorsal surface of skull
11. Gautier (1986) lists 25 synapomorphies including; extra fenestra in the maxilla; narrow elongate metatarsus; elongated zygopophyses on the vertebrae near the end of the tail; etc.

References

• Padian, K., J. R. Hutchinson, and T. R. Holtz, Jr.  1999.  Phylogenetic definitions and nomenclature of the major taxonomic categories of the carnivorous Dinosauria (Theropoda).  Journal of Vertebrate Paleontology, 19: 69-80.
• Sereno, P. C.  1999.  A rational for dinosaurian taxonomy.  Journal of Vertebrate Paleontology, 19: 788-790.

NOTES ON THEROPOD PALEOBIOLOGY

Eoraptor

• The upper Triassic Eoraptor is one of  the earliest dinosaurs, close to the common dinosaur ancestor.  Sereno considers it a primitive theropod, although others consider it a primitive dinosaur or pre-dinosaur.  

Characters

• 1 m long
• bipedal
• nearly-tridactyl hands indicate that it is a theropod (Sereno et al., 1993).

References

• Sereno, P. C., C. A. Forster, R. R. Rogers, A. M. Monetta.  1993.  Primitive dinosaur  skeleton from Argentina and the early evolution of Dinosauria.  Nature 361:64-66.
• in prep.  Sereno, P. C., R. N. Martinez, and O. A. Alcober.  The primitive dinosaur Eoraptor lunensis and the early evolution of Theropoda.  Journal of Vertebrate Paleontology, Supplement., MS 125 pp., 102 figs

Herrerasuaridae

Sereno considers the two or three genera of this family to be basal theropods.  Other suggest that they are dinosauromorphs that lack the synapomorphies of the dinosauria.  They are briefly discussed on my ancestry of the dinosaurs page.

Neotheropoda

Included taxa

• Ceratosauria and Tetanurae

characters

• reduction in hands and feet to three functional digits
  • rotary wrist and a large grasping manus
  • manus with fifth digit absent, fourth digit and metacarpal very reduced to absent
  • functionally three-toed foot:  Digit V reduced to a splint of metatarsal and Digit I  drawn high up the metatarsals and not involved in weight support,
• light bones
• ?furcula (see below)

CERATOSAURIA 

Range

• late Triassic-late Cretaceous

Characters

• primitive theropods
• relatively small, lightly built forms (5-7 m long).
• loose attachment of premaxilla to maxilla
• narrow-boned pubis
• fusion of ilium, pubis, and ischium in adults
• neck vertebrae with two pairs of pleurocoels  (hollow spaces)

Coelophysoidea. 

• late Triassic - Early Jurassic
  • Coelophysis, Late Triassic, Chinle Group, Arizona, USA
  • Dilophosaurus Early Jurassic, Glen Canyon Group, Arizona, USA
  • Syntarsus: -  Syntarsus kayentakatae, described by Tim Rowe in 1989, had two small crests, similar to those of larger coelophysoids like Dilophosaurus.  Learn more about this dinosaur from the UT Digital Image Laboratory.

Neoceratosauria. 

• late Jurassic - late Cretaceous
  • Ceratosaurus , Late Jurassic, Morrison Formation, Western USA.  Described by O.C. Marsh
  • Abelisauridae

TETANURAE

Included taxa

• Megalosaurus, Spinosauroidea, Allosauroidea, and Coelurosauria

Characters

• includes all the theropods more advanced than the ceratosaurs.
• teeth lie entirely in front of orbit, beginning a trend of shortening of tooth row by reduction of posterior teeth [D&R p. 184]
• maxillary fenestra present
• fusion of clavicle to form a furcula [D&R p. 184; synapomorphy for tetanurines].
  • H. Bryant and A. Russell, 1993, JVP 13:171-184 considered the furcula is a possible neomorph in maniraptorans; Chure, D. and J. Madsen, 1996, JVP 16:573-577 demonstrate a furcula is present in allosaurids. Makovicky, P and P. Currie, 1998, JVP 18(1):143-149 provide evidence for furculae in tyrannosaurids and rerun Bryant and Russell's (1993) congruence tests and conclude furculae are primitively present in theropods.)
• tall ascending process of the astragalus extends upward on tibia [D&R p. 185]
• end of pubis is expanded into a "boot" [D&R p. 191]
• posterior half of tail stiffened, lacks haemal arches
• three-fingered hand (digit IV is absent in adults)

Megalosaurus

• Megalosaurus is an early tetanurine that is neither a carnosaur or coelurosaur.
• Officially discovered around 1815, this is the first non-avian dinosaur to be formally described (Buckland , 1824).   In 1676, Robert Plot described the distal end of a megalosaur femur was described as the remains of an elephant brought to Britain by the Romans.  Richard Brooks in 1763 reillustrated the bone which he labeled Scrotum humanum [as a descriptive appellation]. In 1768 Jean Baptiste Robinet described the specimen a real scrotum.
• The Ardley megalosaur trackway

Spinosauroidea  

Characters

• piscovorous, bipedal theropods 
• elongate crocodile-like snout and conical teeth
• elongate neural spines

Example

• Suchomimus tenerensis 

Reference

• Sereno, P. C., A. L. Beck,  D. B. Dutheil, B. Gado,  H. C. E. Larsson, G. H. Lyon,  J.. D. Marcot, O. W. M. Rauhut, R. W. Sadleir, C. A. Sidor, D. D. Varricchio, G. P. Wilson, and J. A.Wilson. 1998.  A Long-Snouted Predatory Dinosaur from Africa and the Evolution of Spinosaurids. Science 282:1298-1302

Avetheropoda (=Neotetanurae)

Included taxa

• Carnosauria plus Coelurosauria

Characters

• furcula (wishbone)
• sternum (breastbone)
• a  rotary wrist and a large grasping manus
• loss of fourth and fifth fingers
• Pubic foot: anterior expansion of pubis

CARNOSAURIA

• Large meat eating dinosaurs that reached their peak in the Jurassic.  Carnosaurs formerly included Allosauridae and Tyranosauridae - the often very large dinosaurs of the Jurassic and Cretaceous. Now it is recognized that tyrannosaurs and allosaurs are not sister taxa and that large size evolved independently in both groups.  The term is restricted to the allosaurs, which are basal tetanurines.

Allosauroidea

Characters

• femur is usually larger than the tibia
• long, narrow skull. with large orbits
• antorbital fenestra expanded upwardly
• maxillary fenestra is expanded upwards forming a large hole in lacrimal bone (this also occurs in tyrannosaurids)
• many allosauroids had crests on top of their heads

Example

• Allosaurus fragilis, Late Jurassic, Morrison Formation, Western USA 
• Acrocanthosaurus: an early Cretaceous Texas carnosaur
  • Fran the Acrocanthosaurus atokensis from Oklahoma
• Carcharodontosaurus; Cretaceous (Albian-Cenomian), Africa
  • A giant theropod, rivaling Tyrannosaurus in size, if not mass.  According to Paul Sereno (in 1995), it is the largest carnivore to have walked the earth.  It has an estimated head length of 153 cm, which is less than the 165 cm of Giganotosaurus.
• Giganotosaurus carolinenii named in 1995 is a carcharodontosaurine from the late Cretaceous (Cenomian), Patagonia, Argentina.
  • The largest terrestrial carnivore ever .  Almost two meters longer and two tons heavier than Tyrannosaurus. 
• pack hunting; more on pack hunting

COELUROSAURIA

Included taxa

• Compsognathidae, Theriznosauridae, Tyrannosauroidea and Maniraptora

Characters

• metatarsal lII is pinched between metatarsals II and IV, making a stronger foot [D&R p. 186]
• sternal plates fused (solid, bony sternum)
• elongate, slender forelimb and hand (forelimb is at least half the length of hindlimb)
• fenestra in roof of mouth.
• down-like feathers? (see Sinosauropterix).  A discussion of which dinosaurs had feathers by high-school student Grant Harding.
• Longisquama, a late Triassic gliding archosaur of uncertain relationships, has been purported to have feathers (Jones et al., Science, 288: 2202-2205).  This is controversial.

Primitive Coelurosaurians

• Compsognathus: a chicken-sized dinosaur  (0.7-1.4 m long), Late Jurassic, Solenhofen Limestone, Germany--the original specimen; 
  • also known from the Early Cretaceous, Liaoning lake beds, China.
• Ornitholestes, Late Jurassic, Morrison Formation, Western USA
• Scipionyx, known from an exceptionally well-preserved specimen of a juvenile shows traces of the intestines, windpipe, liver, and muscle fibers.
  • Skippy the Dinosaur, from Jeff Poling
• Sinosauropteryx
  • Sinosauropterix (Ji and Li, 1996), Early Cretaceous, Yixian Formation, Liaoning beds, China
• a chicken-sized dinosaur with a fringe of down-like structures along its neck and backbone 
• Chen, P., Z. Dong and S. Zhen 1997 "An exceptionally well preserved theropod dinosaur from the Yixian Formation of China." Nature 391:147-152

ARCTOMETATARSALIA

Included taxa

• Tyranosauridae and Ornithomimosauria

Characters

• metatarsal III tapers to a thin wedge proximally near the ankle joint
• metatarsals are slender, deep, and elongate

Tyrannosauridae

Characters

• giant predators of the Cretaceous
• reduced forelimbs
• phalanges of digit III of hand are lost
• A detailed look at Tyrannosaurid Systematics by Thomas R. Holtz, Jr.

Examples

• Albertosaurus, Late Cretaceous, Judith River beds, Alberta, Canada
  • Learn more about the 8-10 meter long Albertosaurus from the Field Museum.
• Tarbosaurus, Late Cretaceous, Mongolia
• Tyrannosaurus Late Cretaceous, Hell Creek Formation, Montana; Judith River beds, Alberta
  • contrast the 1915 and recent mounts at the AMNH
  • Tyrannosaurus, at the UCMP; 
  • The 12-14 meter long, 8 ton Tyrannosaurus is one of the largest terrestrial meat-eaters, ever, although it has been exceeded by some recent discoveries (such as Giganotosaurus).
  • Jack Horner suggests that T rex was a scavenger, not a predator.
  • More on scavenging
  • T rex as a plodder
  • Tyrannosaurus family life: a painting by John Lanzendorf
  • An astounding recent dinosaur discovery from southwestern Saskatchewan (Chin, K., T. T. Tokaryk, G. M. Erickson & L. C. Clark. 1998. A king-sized theropod coprolite. Nature 393: 680-682. ) is of a tyrannosaur coprolite 44 cm long (17 inches long, six inches wide and five inches tall, weighing nearly 16 pounds) containing shattered bones.
  • Bite marks attributable to Tyrannosaurus occur on Edmontosaurus and Triceratops bones [Bite marks attributable to Tyrannosaurus rex: Preliminary description and implications .  G. M. Erickson, and K. H. Olson, Journal of Vertebrate Paleontology, 1996, 16(1): 175-178.].  Erickson has also demonstrated that the jaws of Tyrannosaurus exerted a bite force of between 1,400 and 3,000 pounds, "greater than the crushing force of any known creature though close to the maximum force exerted by the American alligator."  [Erickson, G. M., S. D. Van Kirk, J. Su, M. E. Levenston, W. E. Caler, and D. R. Carter. 1996. Bite-force estimation for Tyrannosaurus rex from tooth-marked bones. Nature, 382:706-7]
  • Body mass, bone ''strength indicator'', and cursorial potential of Tyrannosaurus rex 
    J. O. Farlow, M. B. Smith, and J. M. Robinson, Journal of Vertebrate Paleontology, 1995, 15(4): 713-725 
  • Tyrannosaurus the cannibal from Jeff Polling
  • Brochu, C. A.  2003.  Osteology of Tyrannosaurus rex: Insights from a nearly complete skeleton and high-resolution Computed Tomographic Analysis of the skull.  Society of Vertebrate Paleontology, Memoir 7, Journal of Vertebrate Paleontology, 22, Supplement to Number 4: 1-138

Ornithomimosauria (Cretaceous)

Characters

• slightly built; medium to large-size ostrich-like dinosaurs
• cursorial
• toothless jaws in later forms
• beak-like snout
• elongate hindlimbs
• non-raptorial hand
• manus with nearly equal length metacarpals; etc.
• gastroliths from ornithomimids indicate an herbivorous diet (Kobayashi et al., 1999.  Nature 402: 480-481.)

Examples

• Pelecanimimus  had over 220 teeth, more than any other theropod.
• Struthiomimus
• Gallimimus, Early Cretaceous, Mongolia
• Ornithomimus, Late Cretaceous, Judith River beds, Alberta, Canada
• Deinocheirus, Late Cretaceous, Mongolia.  known only from a very large pair of arms

Maniraptora

Characters

• vaned feathers for food capture, display, and/or brooding
• long arms (forelimbs are >75% length of hindlimb) [D&R p. 190]
• bowed ulna and semilunate carpal [D&R p. 191]
• pubis is backturned [D&R p. 191]
• reduced or absent prefrontal
• reduced carpus 
• posterior 3/4 of tail stiffened
• pubis points down and back
• front half of pubic boot is absent

Included Taxa

• ?Theriznosauria
• Oviraptosauria
• Troodontidae
• Dromaeosauridae
• Aviale

Therizinosauria

• Strange looking dinosaurs with teeth lost in front of mouth and very large claws on manus.  
• The feet have four functional toes, unlike the other three-toed theropod feet.  
• Previously considered as possible relicts of the prosauropod-ornithischian transition  Sereno considers them the sister taxon of the Ornithomimidae.  Pisani et al. include them in the Oviraptosauria.

Examples

• Beipiaosaurus: from the early Cretaceous of China has 'feathers' similar to those of the primitive coelurosaur Sinosauropteryx.
  • Xu, X., Z. Tang and X. Wang 1999 "A therizinosauroid dinosaur with integumentary structures from China". Nature 399:350-354. 
• Therizinosaurus, Late Cretaceous, Mongolia
• Segnosaurus, Late Cretaceous, Mongolia

Oviraptorosauria

Previously considered ornithomimids, now included in maniraptors. Oviraptor was first discovered in Mongolia near what was thought to be the nest of a Protoceratops, presumably intent on stealing an egg.  In fact, inside the eggs are skeletons of fetuses of Oviraptor.  A recent discovery is of an Oviraptor on top of a nest of eggs which she may have been brooding like a bird.  To learn much more about oviraptosaurs, visit Jaime A. Headden's Qilong site.

Characters

• skull deep, highly fenestrate, with a large crest
• lacking teeth, having instead a toothless beak

Example

• Oviraptor, Late Cretaceous, Mongolia

Troodontidae

Characters

• bulbous, relatively large braincase
• many small teeth with large denticles
• Some consider this family to be the sister taxon of the Ornithomimidae

Examples

• Troodon, Late Cretaceous, Judith River beds, Alberta, Canada
• Sinornithoides, Early Cretaceous, Mongolia

Protarchaeopterix

Characters

• down-like feathers on body and tail for insulation
• vaned, symmetrical feathers forming a fan along the tail.  Flying birds have asymmetrical feathers.
• Kesey considers it to be a primitive maniraptoran
• Qiang, J., P. Currie, M. Norell, and J. Shu-An 1998 "Two feathered dinosaurs from northeastern China." Nature 393:753-761 

Dromaeosauridae see Currie; 1995; Journal of Vertebrate Paleontology 15:576-591

Characters

• giant, hook-like claw on digit II of foot
• posterior 80% of tail stiffened with very elongate haemal and neural arches

Examples

• Deinonychus antirrhopus , Early Cretaceous, Cloverly Formation, Wyoming, USA
  • 2.7 m long.
• Velociraptor mongoliensis, Late Cretaceous, Mongolia
• Dromaeosaurus, late Cretaceous, Alberta, Canada.
  • Learn more about Dromaeosaurus,   a fierce, dog-size predator, from the British Museum.
• Utahraptor
  • Utahraptor ostrommaysi, Cretaceous, Utah about 5 m long
• Megaraptor late Cretaceous; Argentina
  • a maniraptoran with a large claw, but may not be a dromaeosaur. Megaraptor has a page comparing it with Deinonychus and Utaraptor.  about 8 m long
• Microraptor
  • 39 cm long, but 24 cm's of that was a long straight tail. (Xu, X. 2000. Nature vol 408, p 705)
  • Feathers on the front and hind limb ("four-winged") for gliding.  (Xu et al. 2003, Nature, 421:335)

Eumaniraptora

Characters

• sideways-flexing wrist
• longer arms and hand
• feathers with shaft, vane and barbs
• primary feathers attached to digit II (longest finger)

Caudipterix Ji, Currie, Norell, & Ji, 1998

• not quite capable of powered flight
• feather impressions at tail, back, thigh, and neck
• short arms and  long legs
• specimen contains gastroliths
• National Geographic reconstruction
• Kesey interprets this genus as a more primitive maniraptoran.

Distribution

• Yixian Formation, Liaoning Province, China;  early Cretaceous

Reference

• Ji, Q., Currie, P.J., Norell, M.A., and Ji, S.-A. 1998. Two feathered dinosaurs from northeastern China. Nature 393: 753-761.
• National Geographic press release

Sinornithosaurus 

This deinonychosaur may be the sister taxon to the birds. It has filamentous feathers.  Its arms are proportionally very long -- 80% as long as the legs.  The shoulder girdle has features like those of flying birds; it could flap its arms..

Distribution

• Yixian Formation, Liaoning Province, China;  early Cretaceous

Reference

• Xing Xu, Xiao-Lin Wang, and Xiao-Chun Wu, Nature 401, September 16, 1999, pp. 262-266
• Xu, X., Zhou, Z.-h., and Prum, R. O. 2001. Branched integumental structures in Sinornithosaurus and the origin of feathers. Nature 410(6825):200-204.  "Here we describe our observations of the filamentous integumental appendages of the basal dromaeosaurid dinosaur Sinornithosaurus millenii, which indicate that they are compound structures composed of multiple filaments. Furthermore, these appendages exhibit two types of branching structure that are unique to avian feathers: filaments joined in a basal tuft, and filaments joined at their bases in series along a central filament."

  Avialae

Characters

• the first birds, powered flight
• long flight-feathers on forelimb
• hallux (digit I) is reversed [D&R p. 192]
• arms at least as long as legs
• greatly enlarged brain
• fewer than 25 caudal vertebrae

Archaeopterix (late Jurassic)

• Archaeopterix and the origin of flight
• Characteristics
1. flight feathers
2. furcula (fused clavicles) present, as in modern birds
3. expanded sternum absent
4. thecodont teeth
5. long tail without a pygostyle
6. metacarpals separate, not fused--claws on hands
7. hand reduced to 3 digits
8. pubis oriented intermediate between theropod and bird
9. capable of gliding or powered flight as evidenced from the structure of the feathers and the forearm.
10. The postcranial skeleton is predominantly reptilian, the skull shows a combination of primitive avian and archosaurian characters

Bambiraptor

Unenlagia Unenlagia

Alvarezsauria

• These small, strange looking dinosaurs have been difficult to place taxonomically.  They have odd-shaped single-digit forelimbs.
• Mononykus

Ornithothorraces: all other birds.  They are better adapted for powered flight

• Characteristics
  1. pygostyle present;
  2. strutlike coracoid
  3. sternum present

Order Enantiornithoformes (Cretaceous)

• the predominant land birds of the Cretaceous; teeth and gastralia are present
• examples
  • Sinornis  
  • Apsaravis ukhaana
    • Norell, M.A. and Clarke, J.A. 2001. Fossil that fills a critical gap in avian
      evolution. Nature 409(6817):181-184.

Order Hesperornithiformes

• loon-like sea birds of the Cretaceous
• teeth are present
• Hesperornis

Infraclass Neornithes ("New Birds")

Characteristics

loss of teeth

Superorder PALEOGNATHAE (Cenozoic)

• mostly flightless birds; which have a flat sternum with poorly developed pectoral muscles, that live primarily on Southern Continents
• ratites (kiwis, emus, cassowaries, rheas, ostriches, moas) and tinamous

Characters

1. usual absence of flight feathers
2. paleognathous palate (large vomers, small palatines, with pterygoid-vomer articulation
3. sternum reduced, usually without a keel
4. pygostyle poorly developed or absent.

Taxa

1. Aepyornis [fig. 17-21a], the elephantbird of Madagascar, stood around 3 m tall and weighed about 660 kg, 20 lb. egg, 1 ft. long, 2 gallons; herbivore
2. Dinornis, a moa from New Zealand stood 3.6 m tall and weighed up to 300 kg, herbivore.
3. Ostrich: largest living bird; 2.6 m tall; lives in Africa; eats plants and small animals; ostrich up to 150 kg
4. Emu: lives in Australia and reaches 6'
5. Cassowary: lives in Australia & New Guinea
6. Kiwi: 3 species that live in New Zealand
7. Rhea: South America
8. Tinamous: only group of ratites that fly, found in South America, Central America, and Mexico
   

Superorder NEOGNATHAE (Cenozoic)

Characters

1. all other living birds Table 18-1
2. carinates - the flying birds that have a keeled sternum on which the powerful flight muscles insert. Some carinates have become flightless
3. neognathous palate  (small vomers, large palatines, pterygoid not reaching vomer articulation)
4. About 22 orders, including the following:

1. Order Podicipediformes: grebes;
2. Order Anseriformes: waterfowl
   1. including ducks, geese, and swans:
   2. Trumpeter swan is the heaviest flying bird: trumpeter swan--17 kg;
3. Order Pelicaniformes: marine birds;
   1. including pelicans, cormorants, anhingas
4. Order Ciconiiformes: wading birds
   1. egrets, herons, ibises, spoon bills, and storks:
   2. new world vultures are probably closely related to storks
      1. The largest flying bird was the extinct giant condor, Argentavis, a Teratornithidae (related to New World vultures) from the late Miocene of Argentina, that weighed 75 kg, stood 2 m tall and had a wingspan of up to 8 m.
5. Order Falconiformes: birds of prey;
   1. including  hawks, eagles, falcons and Old World vultures
6. Order Galliformes: fowl; including the chicken, turkey, grouse, and pheasants:
7. Order Gruiformes:
   1. 12 families, including cranes, coots, rails
   2. terror cranes: extinct, flightless, giant (over 2 m tall), cursorial predators   evolved independently at least twice in the Gruiformes
      1. Diatryma: [Paleocene and Eocene of North America and Europe]
      2. Phorusrhacus [Miocene and Pliocene of South America] and Titanis [Pliocene and Pleistocene of North America]
8. Order Charadriiformes: shorebirds; including plovers, sandpipers, gulls, terns, and skimmers:
9. Order Gaviiformes: loons;
10. Order Columbiformes: including pigeons, doves, and the recently extinct dodo:
11. Order Psittaciformes: parrots and macaws;
12. Order Strigiformes: owls;
13. Order Apodiformes: hummingbirds and swifts;
14. Order Piciformes: woodpeckers and toucans;
15. Order Passeriformes: perching birds/songbirds;
    1. 64 families
    2. comprise about 1/2 of all species (4000 species) of birds,

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