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Home , Gnathostomata (echinoid), Rhipidistia

Biology 3315 - Comparative Morphology Systematic Overview of and Part I: Protochordates and

The first laboratory period will be devoted to an overview of . This will serve to make the major systematic groups familiar to students when reference is made to them throughout this lab. The following outline lists some of the characteristic morphological features of each group; others will be presented as the course progresses.

______Echinodermata (echino = hedgehog/ + dermato = skin, in reference to spiny skin) Common names: sea stars, sea urchins, sea cucumbers, sand dollars, brittle stars Diagnostic features: Larvae have bilateral symmetry, modern adults are pentameral in shape (five-fold symmetry with rays or arms in fives or multiples of fives). Some fossils have numerous variations in ray/arm number. They have a system of internal water-filled canals that may form suckered “tube-feet” that the may move or grip objects with. Endoskeleton is made of calcite plates.

Hemichordata (hemi = half + chordata = cord, in reference to notochord) Common names: Tongue or acorn worms Diagnostic features: Larvae are free swimming and similar to larvae. Adults have a proboscis, collar, and trunk. Stomochord (an anterior extension of the pharynx) is present within proboscis, possibly for support.

Chordata Diagnostic features: bilateral symmetry, segmented body structure, coelom, three germ layers, hollow dorsal nerve cord, notochord, pharyngeal respiratory mechanism, ventral heart, blood running posterior in a dorsal vessel

Cephalochordata (cephalo = head, in reference to notochord extending into head Common names: or Amphioxus Diagnostic features: small, lance-shaped, sand-burrowing plankton feeders, notochord extends entire length of body

Urochordata (uro = tail, in reference to notochord in tail region) Common names: or sea squirts Diagnostic features: pollywog-like larva has notochord in tail, sessile adults with sac-like tunic and siphons

Vertebrata (Craniata) (vertebra = backbone from vertere to turn) Diagnostic features: notochord extending only to infundibulum, skeleton with vertebrae and cranium, bone of apatite, thyroid and pituitary glands, muscular chambered heart, red blood cells, advanced central nervous system, paired organs of sight and hearing; semicircular canals

Agnatha (a = no, without + gnathos = jaw) Common names: cyclostomes (circle mouths) Diagnostic features: no jaws, no true paired appendages

Myxiniformes (myxinos = mucus) Common names: Diagnostic features: parasitic, specialized, degenerate survivors of the class, body elongate and eel-like, mouth terminal and open, no lateral appendages, mucus glands secrete onto skin

Petromyzontiformes (petro = rock + myzon = to suck) Common names: lamprey Diagnostic features: parasitic, specialized degenerate survivors, body elongate and eel-like, mouth terminal and open, no lateral appendages

Pteraspidomorpha (ptera = wing + aspidos = shield) Diagnostic features: two nostrils (diplorhina)

Heterostraci (heteros = different + ostraci = shell)

Cephalaspidomorpha (cephalos = head + aspidos = shield) Diagnostic features: single nostril (monorhina)

Osteostraci (osteo = bone + ostrachi = shell)

Anaspida (an = without + aspida = shield)

Gnathostomata (gnathos = jaw + stomato = mouth) Diagnostic features: jaws

Placodermi (placo = tablet, plate + derm = skin) Diagnostic features: bony armor to varying degrees, head and thoracic armor joined at a moveable hinge

Antiarchi (anti = opposite + arch = bow, in reference to appendages)

Arthrodira (arthos = joint + dira = neck)

Chondrichthyes (chondros = cartilage + ichthyes = ) Diagnostic features: cranium solid, endoskeleton cartilaginous (no bone), pelvic fins of males with clasping organs, no lung or gas bladder, medium to large size, chiefly marine

Elasmobranchii (elasmo = a plate + branch = a gill) Diagnostic features: separate gill openings (5-7 pairs), spiracle present, skin with placoid scales, teeth numerous, continuously replaced

Cladoselachimorpha (clado= branch or stem + selacho = shark + morph = form)

Xenacanthimorpha (xenus = stranger+ acanthi = spine or thorn + morph = form)

Selachimorpha (selacho = shark + morph = form) Common names: sharks Diagnostic features: mouth ventral, paired fins with narrow bases and no median axis, tail strongly heterocercal

Batidoidimorpha (bati = ray fish + id = condition of + oid = like/form + morph =form) Common names: rays and skates Diagnostic features: dorso-ventrally flattened, mouth ventral, paired fins with broad bases, weakly heterocercal tails

Holocephali (holo = whole or entire + cephalos = head) Common names: chimaeras, ratfish Diagnostic features: gill openings covered by fleshly operculum, spiracle absent, skin naked, open lateral line system, teeth few, permanent crushing plates, tail diphycercal

Acanthodii (acantho = spine or thorn) Diagnostic features: numerous paired fins supported by stout spines

Teleostomi (teleo = an end or complete + stoma = mouth) Diagnostic features: complete bony endoskeleton

Actinopterygii (actin = ray + ptery = wing or fin) Diagnostic features: fins have bony rays, no central axis, nostrils are dorsal and do not open into mouth

Palaeonisciformes (paleo = ancient + form = shape) Common names: extinct primitive ray-finned fishes Diagnostic features: heavy ganoid scales, strong heterocercal tail, endoskeleton poorly ossified, spiracle generally present

Paleoniscoids (paleo = ancient + oid = like/form)

Chondrostei (chondro = cartilage + osteo = bone) Common names: sturgeon, paddlefishes, reedfishes, birchirs Diagnostic features: endoskeleton mostly cartilagenous, spiracle present

Polypteriformes (poly = many + pteri = wing) Common names: bichirs, reedfishes Diagnostic features: fleshy pectoral fins, dorsal fin divided into numerous dorsal finlets

Acipenseriformes (aci = point, barb + pen =almost, nearly + seri = a series or row + form = shape) Common names: sturgeon, paddlefish Diagnostic features: heavy ganoid scales when developed, endoskeleton poorly ossified, dermatocranium heavily ossified

Neopterygii (neo = new or recent (also means swim) + ptery = wing) Common names: advanced ray-finned fishes Diagnostic features: increased jaw mobility, and in the most advanced neopterygians, reduced scales and a homocercal tail

Holostei (holos = complete, entire + osteo = bone) Common names: gars, bowfins Diagnostic features: ganoiod scales, skull bones fused and thick, teeth on all bones surrounding mouth

Lepisosteiformes (lepis = scale + osteo = bone + form = shape) Common names: gars Diagnostic features: ganoid scales, skull bones fused and thick, long jaw

Amiiformes (amia = ”a kind of fish”+ form = shape) Common names: bowfins Diagnostic features: ganoid scales, skull bones fused and thick

Teleostei (teleos = complete, perfect + oste = bone) Common names: (too numerous to mention – most living fishes) Diagnostic features: highly reduced scales, ossified vertebrae, circular scales when present without ganoine, swim bladder

Sarcopterygii (sarcos = flesh + ptery = wing or fin) Diagnostic features: internal nostrils, relatively strong jaws paired fins have fleshy (muscle) base and a bony central axis

Crossopterygii (cross = tassel or fringe + ptery = wing/fin) Fishes with distinct fin skeleton

Rhipidistia (rhipi = fan + ist = superlative ending, referring to fan, meaning large or great fan) sister group to Common names: “rhipidistians” (e.g., , Panderichthyes) Diagnostic features: highly modified skull bones for greater mobility and specialized feeding, labyrinthodont teeth

Coelacanthiformes (Actinistia) (coel = hollow + acantho = spine or thorn + form = shape) Common names: Latimeria, Diagnostic features: tiny vertebral centra, prominent notochord, swim bladder is filled with fat in non-extinct fishes

Dipnoi (di = twice, two + pnoi = breath, referencing two apertures) Common names: Diagnostic features: endoskeleton poorly ossified pectoral fin with radial elements on both sides of central axis (archipterygium) teeth few, forming large crushing plates