Biology 3315 - Comparative Vertebrate Morphology Systematic Overview of Chordates and Vertebrates Part II: Tetrapods

As with the protochordates and fishes laboratory, the tetrapod laboratory period will be devoted to a overview of Vertebrate animals. This will serve to make the major systematic groups familiar to students when reference is made to them in lecture and subsequent lab exercises. The following outline lists some of the characteristic morphological features of each group; others will be presented as the course progresses. ______

Tetrapoda (tetra = four + podo = foot) (vertebrates with 4 dactylous appendages) Diagnostic features: instructive to think of these animals as the land dwelling vertebrates; many features associated with life on land, e.g. - lungs, eggs with shells and fetal membranes

Labyrinthodontia (labyrinth = a winding structure + dont = tooth) (basal group of land dwelling vertebrates) Diagnostic features: skin with dermal armor, teeth with complicated enamel patterns, limbs generally strong

Ichthyostegalia (ichthy = fish + stega = a cover) (earliest tetrapods)

Anthracosauria (anthraco = coal, charcoal + saur = a lizard; in reference to its discovery in coal beds) (terrestrial; sister group to )

Lepospondyli (lepo = a husk, a scale + spondyl = a vertebra) – chiefly small, extinct aquatic amphibians Common names: Nectridians (as well as several others)

Amphibia (amphi = around, on both sides, double + bio = life) Diagnostic features: adults semi-terrestrial, have four limbs with toes, larvae aquatic with metamorphosis, no amnion, fertilization external.

Temnospondyli (temno = cut + spondyl = a vertebra) – amphibious & semi-terrestrial labyrinthodonts Common names: Temnospondyls

Lissamphibia (liss = smooth + amphi = around, on both sides, double + bio = life) (modern amphibians) Common names: salamanders, frogs, toads, and caecilians Diagnostic features: skin typically naked and moist, simple pedicellate teeth

Urodela (Caudata) (uros = tail + del = visible/ cauda = tail) Common names: salamanders, newts Diagnostic features: front and hind limbs equally developed, tail long, tympanic membrane absent

Salientia (Anura) (salient = leaping/ a = without + uros = tail) Common names: frogs and toads Diagnostic features: hind limbs lengthened for jumping, tail short or absent, caudal vertebrae fused to form urostyle, tympanic membrane typically present

1 Gymnophiona (Apoda) (gymno = naked, bare + ophio = a snake/ a = without + podo = foot) Common names: caecilians – tropical limb-less burrowers Diagnostic features: limbs secondarily absent, body elongate, worm-like, eyes vestigial

Amniota (vertebrates with embryos having an amnion)

Reptilia (reptil= creep, crawl) Diagnostic features: no aquatic larvae or metamorphosis, adults terrestrial or secondarily aquatic, amnion and allantois, fertilization internal, epidermal scales usually present

Parareptilia (para = beside, beyond, near + reptil = creep, crawl) Diagnostic features: distinctive ear region wherein eardrum is supported by squamosal (rather than quadrate) and by retroarticular process, foot is unique in the way digits articulate with ankle bones

Pareiasauria (parei = the cheek + saur = lizard) Large herbivores

Testudinata (Chelonia) (testud = turtle; chelon = tortoise, turtle) Common names: turtle, tortoise, terrapin Diagnostic features: skull without temporal openings, trunk modified to form a rigid shell, shoulder girdles appear to be inside rib cage, teeth absent

Synapsida (syn = with, together + apsi = juncture) Diagnostic features: development of single arch and fenestration in the skull formed by squamosal and postorbital bones

Pelycosauria (pelyco = a basin, the pelvis + saur = lizard) Primitive mammal-like

Therapsida (ther = a wild beast + apsi = juncture) advanced mammal-like reptiles Diagnostic features: trend of increasing parasagittal limb posture, specialization of teeth, larger temporal fenestrae and jaw hinges more anterior than in pelycosaurs

Cynodontia (cyno = a dog + dont = tooth) (sister group to mammals)

Eureptilia (eu = good, well + = creep, crawl) Diagnostic features: supratemporal fenestration small, parietal and squamosal broadly in contact, caniniform maxillary tooth

Captorhinomorpha (capt = eat quickly + rhino = nose + morph = form) Stem reptiles; sister group to diapsids

Lepidosauromorpha (lepido = a scale + saur = lizard + morph = form) Diagnostic features: retroarticular process large, teeth absent on lateral pterygoid flanges, parasphenoid teeth absent, postfrontal borders upper fenestra, supratemporal absent, quadrate wide in posterior view, quadrate foramen absent, intercentra absent from trunk vertebrae, rigid pectoral girdle, large sternum, overlapping scales. 2

Lepidosauria (lepido = a scale + saur = lizard) Diagnostic features: Determinate growth with epiphyses on terminal ends of long bones, post-parietal and tabular bones absent, fused astragalus and calcaneum

Sphenodonta (spheno = a wedge + dont = tooth) Common names: Sphenodon, tuatara Diagnostic features: Broad mandibular symphysis, prominent coronoid process of dentary, frontals not fused, lacrimal absent, large upper temporal fenestration, complete lower temporal bar, quadratojugal retained, epiphyses present with determinate growth

Squamata (squama = a scale) Common names: snakes, lizard, iguanas Diagnostic features: loss of the lower temporal bar in the skull (more room for jaw muscles to develop), development of a special moveable hinge, the quadratojugal hinge, between the quadrate and squamosal bones in the skull (termed streptostyly), reduced left lung typical

Amphisbaenia (amphi = around, on both sides, double + baeno = walk or step) Common names: amphisbaenids, “worm-lizard” Diagnostic features: no distinct head, no limbs, no external ear openings, no functional eyes, rings of scales around body produce segmented appearance, skull heavily ossified, frontal bones surround brain, reduced right lung

Sauropterygia (saur = lizard + ptery = wing) Common names: Pachypleurosaurs, Nothosaurs, Pliosaurs

Plesiosauria (plesio = near, recent + saur = lizard) Common names: Plesiosaurs

Ichthyopterygia (ichthyo = fish + ptery = wing Common names: Ichthyosaurs

Archosauromorpha (archo = chief, principal; ruler + saur = lizard + morph = form) Diagnostic features: Cervical ribs with 2 heads, concave-convex articulation of astragalus & calcaneum, premaxilla extends dorsally behind nares and excludes maxilla, teeth in sockets, neck with 7-8 vertebrae, centra not deeply amphicoelous

Archosauria (archo = chief, principal; ruler + saur = lizard) Common names: crocodiles, alligators, , flying reptiles Diagnostic features: size moderate to gigantic, hind quarters and tail usually large, skull diapsid, teeth marginal

Crocodylia (crocodile = a lizard, a crocodile) Common names: crocodile, alligator, caiman, gavial Diagnostic features: hind quarters and tail usually large, diapsid skull, mandibular fenestration, thecodont, homodont teeth

3 Pterosauria (ptero = a wing, feather, fin + saur = lizard) Common names: pterodactyl, pteranodon Diagnostic features: flying reptiles with membranous wings with fibers for stiffening, large eyes, sizable brains; keeled sternum, long retroverted scapula (as in ), long hollow bones supported by struts

Saurischia (saur = lizard + ischia = the hip, hip joint) Common names: lizard-hipped dinosaurs

Ornithischia (ornitho = + ishcia = the hip, hip joint) Common names: bird-hipped dinosaurs

Aves (avi = bird) Diagnostic features: capable of flight unless secondarily lost, feathers present, homeothermic, air sacs present, diaphragm absent, incubation of eggs and care of young are characteristic

Sauriurae (saur = lizard + urea = the hindmost or tail) Diagnostic features: arms of the furcula broad and grooved caudodorsally rendering them laterally incompressible, outer condyle of the femur possesses a dorsal crest, dorsal ischial process, proximal to distal metatarsal fusion, scapula possesses a craniomedial process which articulates with the craniothoracic vertebrae

Archaeornithes (archae = ancient + ornitho = bird) (Ancesstral birds) Common names: Diagnostic features: Pigeon-sized extremely primitive bird, probably capable of flight. Skull moderately long and pointed; maxilla, premaxilla and dentary toothed; teeth sparse and small, antorbital fossa with 2 fenestrations (?), quadrate may be moveable, most other dermal skull components present but strongly reduced, tridactyl wings with short, sharp, curved claws

Enantiornithes (enanti = opposite + ornitho = bird) (Primitive birds) Common names: Alexornis, Sinornis Diagnostic features: proximo-distal fusion of the tarsometatarsus, the exact opposite of that seen in , triosseal canal completed by a broad scapular process (rather than coracoid), teeth primitively present, coracoid possesses a distinct triangular depression in dorsal aspect, no uncinate processes on ribs

Ornithurae (ornitho = bird + urea = the hindmost or tail) Common names: Apsaravis and others Diagnostic features: relatively modern birds with sharp orbital process, heterocoelous cervical vertebrae, ribs with uncinate processes, short pygostyle, triosseal canal formed largely from coracoid, high keel approaching full length of sternum

Neornithes (neo = new, recent + ornitho = bird) Common names: All modern birds Diagnostic features: horn beak, teeth absent, fused limb bones, fully-separated four-chambered heart

4 Palaeognathae (palaeo = ancient + gnatho = jaw Common names: ratites (ostrich, emu, rhea, kiwi, tinamous) and their ancestors Diagnostic features: "Paleognathous" palate, consisting of: large (pre-?) vomer attached to pterygoid and palatines, excluding both from parasphenoid joint between , no pterygoid and palatine; moveable joint between braincase and pterygoid, and large basipterygoid processes; primitively, splenial present on dentary; numerous "flight" characters of skeletal anatomy are generally preserved, if more or less vestigialized

Neognathae (neo = new, recent + gnatho = jaw) Common names: all birds minus the ratites (Paleognathae) Diagnostic features: Ornithurae with a “Neognathus” palate; birds with fully developed wings and sternum with a keel, caudal vertebrae fused into a pygostyle, and absence of teeth in both jaws, or modifications of these conditions in secondary flightless birds

Mammalia (mamma =a teat/ mammal = a mammal) Diagnostic features: endothermic animals with a four-chambered heart, hair and mammary glands, a well- developed brain, anucleate red blood cells, muscular diaphragm, limited tooth replacement, three middle ear bones (malleus, incus, stapes (the latter being a homolog to the columella in “lower”vertebrates)).

Prototheria (proto = first, original + theri = wild beast) (Egg laying mammals) Common names: morganucodonts (Morganucodon), docodonts, multituberculates and others

Monotremata (mono = one, single + tremato = hole) Common names: monotremes, egg-laying mammals, platypus, echidna, spiny anteaters Diagnostic features: oviparous, placenta absent, shoulder skeleton reptilian in character, no functional teeth in adult, cloaca present

Theria (theri =a wild beast) Diagnostic features: diagnostic tribosphenic teeth, viviparous

Metatheria (meta = a boundary, between, with, after, change + theri = a wild beast) (Marsupials)

Marsupialia (marsupi = a bag or pouch) Common names: marsupials; kangaroos, wallabies, koalas, tasmanian devils, and several others Diagnostic features: marsupium usually present, yolk sac placenta present; chorioallantoic placenta small or absent, viviparous with young born in premature condition, female reproductive tract doubled, epipubic bones present and effective monophyodont (most primary teeth are resorbed without erupting)

Eutheria (eu = good, well + theri = a wild beast) Diagnostic features: viviparous with well-developed young at birth, chorioallantoic placenta present, brain relatively large

Edentatata (Xenarthra) (e = without + dent = tooth/ xeno = stranger (or guest) + arthr = joint) Common names: anteaters, sloths, armadillos Diagnostic features: incisors and canines absent, premolars and molars (if present) lack enamel, tympanic bone is ring-shaped, forelimbs usually have 5 digits with the 2nd and 3rd digits bearing long, sharp, curved claws 5

Soricomorpha (sorica = shrew + morph = form) Common names: shrews, moles, hedgehogs, tenrecs, and others Diagnostic features: skull low and triangular, rostrum long and narrow, eye orbits are fairly small, many fossorial forms are effectively blind

Chiroptera (chiro = hand + ptery = wing) Common names: bats (microchiropterans (“small hand” bats, and megachiropterans (“large hand” bats)) Diagnostic features: first set of teeth with long, sharp, recurved cusps, echolocation in microchiropterans with complex adaptations of the brain, capable of flight with membranous wings stretched out over 5 digits in forelimb, hindlimb usually rotated 90-180 degrees from typical mammalian orientation, most are heterothermic (reduced metabolism in daily torpor cycle)

Lagomorpha (lago = a hare + morph = form) Common names: rabbits, hares, pikas Diagnostic features: two upper incisors with second directly behind first, no canine teeth with large diastema, upper and lower cheek teeth can only meet on one side at a time (lateral mastication required), auditory bulla from ectotympanic only, entotympanic absent, tail absent or reduced

Rodentia (rod or roden = gnaw) Common names: rodents, several types Diagnostic features: incisors with two layers of enamel on labial (lip) side and none on lingual (tongue) side (creates sharp, beveled edge on incisors), no canine teeth with large diastema, zygomatic arch begins anterior to cheek teeth, large paroccipital process

Primates (prima = first) Common names: [insert name here], monkeys, apes Diagnostic features: shortened rostrum, modified tribosphenic tooth pattern with bunodont cusps, loss of at least one incisor and one premolar in all but most basal forms; (eye) orbits face anteriorly, with stereoscopic, well-developed vision; enlarged brain, floor of auditory bulla from petrosal, clavicle retained as prominent element of pectoral girdle, shoulder joint with great mobility, opposable digits with tactile pads at ends, elongated hind limb, facultative bipedalism common (normal in humans), nail on hallux (big toe) and other digits; herbivorous or omnivorous; two mammaries, one to two young per pregnancy, long gestation and developmental time; frequently highly social, with flexible dominance hierarchies; strongly adapted to arboreal (and hopefully academic) life

Carnivora (carni = flesh + vor = eat, devour) Common names: cats, dogs, bears, weasels, raccoons, mongooses, hyenas, seals, walruses, etc… Diagnostic features: at least one, though typically two, teeth combine to form a scissor-like cutting tool (carnassial teeth – premolar 4 over molar 1), with the exception of bears, seals and raccoons, who have secondarily modified these teeth, usually possess a well-developed sagittal crest and auditory bullae

6 Artiodactyla (artio = even in number + dactyl = a finger or toe) Common names: deer, elk, moose, goats, sheep, pigs, bovids (cows), antelopes, pronghorn, camels, and many others Diagnostic features: the most distinguishing feature is the astragalus – an ankle bone modified into a double-shaped pulley; horns and antlers are common, paraxonic foot, with plane of symmetry between digits three and four, which are the primary weight-bearing elements; digits two and five usually reduced or absent, digit one generally absent; metapodials three and four frequently fused as cannon bone; with an even number of digits/hooves.

Perissodactyla (perisso = odd in number + dactyl = a finger or toe) Common names: horses, zebras, tapirs, rhinoceroses Diagnostic features: ungulates possessing an odd number of hooves, mesaxonic foot with plane of symmetry over digit three, “horns” found in rhinos

Proboscidea (proboscis = that which examines) Common names: mammoths, mastodons and elephants Diagnostic features: elongated and prehensile rostrum (nose), two top incisors modified to form tusks, graviportal limb structure,

Cetacea (cetus = a whale) Common names: whales, dolphins, porpoises Diagnostic features: specialized for aquatic life – forelimbs modified into flippers and hind limbs/pelvic girdle extremely reduced or absent, nares located on dorsal aspect of skull, secondary loss of hair, development of echolocation in odontocetes (toothed whales), but not present in mysticetes (baleen whales)

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