BIS216 Vertebrates Flashcards
Largest group of vertebrates
-Osteichthyes
-More than 30,000 sp
-95% of all fish
Radiation of osteichthyes
-Radiated in Devonian into two groups
-Actinopterygii
-Sarcopterygii
Oldest osteichthyes fossil
Approx. 400 MYA
Actinopterygii
-Ray-finned
-Most fish
-Radials made of endochondral bone (cartilaginous precursor that is replaced with bone)
-Long, delicate rays of dermal origin
-Flexible, can be pushed against body and relaxed
Sarcopterygii
-Lobe-finned
-Have basal, mesomeres and radials
-Fleshy, thicker structures
Non-teleost fish
-Secondarily lack endochondral bone, bone never comes and is always cartilaginous
-Most show loss of scales
-Upper jaw is not fused to cranium (same as teleosts)
-Have non-respiratory gas bladder (‘’)
-Teleost similarities not homologous
-Includes sturgeons and paddlefish
Sturgeon
-1-6+ m
-Benthic
-Can be marine water (but breed in freshwater) or can be freshwater
-Scales reduced to scutes
-Protrusible jaw
-Long lived/late maturing
-Late maturity plus exploitation of eggs for caviar threatens them
Paddlefish
-Paddle structure or rostrum on cranium at anterior end
-Paddle detects electrical impulses for prey catching
-Two species, American and Chinese
-American paddlefish are filter-feeders
-Chinese paddlefish feed on crustaceans etc with protrusible jaw, not seen since 2002 and declared extinct
Teleost diversification
-Rapid diversification in early history
-Thought to be due to 7 hox gene clusters (due to 3 hox gene duplication events)
-Now thought to be due to the development of the jaw
Parts of fish jaw
-Lower jaw is mandible
-Upper jaw consists of maxilla and premaxilla
Protrusion of fish jaw
-Upper jaw not fused to cranium, giving a degree of flexibility and mobility
-This allows for specialisation of feeding mechanisms and ability to exploit a wide range of prey
-protrusion has increased during course of evolution
A specialised feeding mechanism allowed by jaw protrusion in fish
-As mouth extends, buccal cavity increases in volume and sucks in water
-This allows fish to suck up prey with the water
Most diverse fish groups in anterior skull end
-Chichlidae and Labridae show huge variations due to feeding adaptations
-These include for digging, piercing, crushing etc
How are different modes of feeding enabled?
-By pharyngeal jaws, modified from other branchial arches
-Used for prey grinding, tearing or filter-feeding
-Development of these allowed for oral jaws to be free, possibly accounting for diet diversity
Moray eel pharyngeal jaws
-Raptorial
-Can actually move into back of throat and help pull prey down throat
-This is because moray eels are found in coral reefs, where suction feeding isn’t helpful
Features of gnathostomes
-Jawed vertebrates
-Show duplication of hox gene complex
-Have muscular neck region
-Have centrum
4 groups of jawed fish
-Placoderms
-Acanthodians
-Chondrichthyans
-Osteichthyans
Placoderms
-Early jawed fish
-Body covered in bony plates
-Plates on trunk and head
-Went extinct during Devonian period
-Different forms and sizes
-Show viviparity
Clasper
-Intromittent organ to transfer sperm to females from males
-In placoderms, clasper present in pelvic region
-Now jawed vertebrates have modified pelvic fin to join the two, not homologous
Acanthodians
-‘Spiny sharks’
-Stem/basal chondrichthyans
-20cm - 2m
-Toothless
What makes an amniote an amniote?
Amniotic egg
Components of amniotic egg
-Three extraembryonic membranes
-Leathery shell as barrier to outside (more specialised in birds with calcium salts) with pores (some need to be buried to stay moist)
-Albumen made of proteins and water (for protection and moisture) and yolk
Adaptations related to amniote egg
-Internal fertilisation needed
-Intromittent organs homologous (not really in birds), female equivalent is clitoris
-Environmental sex determination after conception (common in reptiles), thought to be ancestral
-No larval stage, so has to be laid on land, with egg laying seen in reptiles, birds and monotremes
Amniote extraembryonic membranes
-Allantois is for expelling waste products and is also vascularised for gaseous exchange (left behind after development)
-Amnion surrounds embryo
-Chorion surrounds everything including yolk and albumen
Tuatura
-Aboriginal for “spines on back”
-Restricted to NZ
-Nocturnal (unusual for reptiles)
-Very diapsid skull with reformed lower bar
-Associated with ground-nesting and burrowing birds
Largest turtle
-Leatherback at 2m long
-Can dive down to 1000m
-Tends to feed on jellyfish
Longest turtle migratory route
-Green turtles feed off coast of Brazil but lay eggs on Ascension island 2,200 km away
-Also herbivorous (unlike most turtles)
Why do hatchling turtles go straight to sea?
-Attracted to light
-Sky above sea looks brighter than sea above land due to reflection
Differences between ancestral and modern turtles
-Ancestors had teeth, modern forms just have horny plates for chewing
-Flexible neck can be drawn in, sometimes to the side, in modern forms but not ancestral
-Ancestral forms had longer tails
Chordate features
-Notochord, positioned between gut and nerve cord
-Dorsal, hollow nerve cord
-Pharyngeal gill slits, with pharynx at start of gut, used for filter feeding or respiration, also found in deuterostomes
-Post-anal tail
-Endostyle secrets mucus in larval lampreys for filter feeding and is homologous to thyroid, shown by transformation of endostyle to thyroid during lamprey metamorphosis
Vertebrae
-Usually replaces notochord in vertebrates as main form of support
-May be of cartilage or bone
-However, not all chordates possess fully formed vertebrate
Gnathostome vertebrate structure
-Centrum in middle
-Wraps around nerve cord
Chordates without vertebrae
-Hagfish and lampreys have rudimentary vertebral precursors (arcualia)
-Lamprey arcualia along body and dorsal (above notochord)
-Hagfish arcualia at tail region and ventral (below notochord)
-Ancestrally, it was dorsal and ventral
Cranium
-Sometimes vertebrates named Craniata
-Can be bony, cartilaginous or fibrous
-Protects brain
-Can be highly specialised
-Cranium and vertebrae make endoskeleton
Embryological features of vertebrates
-Duplication of Hox gene (involved in anterior-posterior directioning) complex (homeobox genes)
-Development of neural crest
-Placodes
Hox gene duplication in vertebrates
-Invertebrate chordates have 1 hox gene cluster, ancestral jawless vertebrates have 2
-Further duplications associated with evolution of other features e.g., jaw
-Duplication occurred during evolution of teleosts, from 4 to 7
-Another duplication for the salmonoids, 7 to 13
Development of neural crest in vertebrates
-Migratory and multipotent
-Specified at boundary of neural plate, which folds to form hollow neural tube, with crests on outside
-Responsible for new structures, especially in head, such as adrenal glands and pigment cells
-Another germ layer, so quadroblastic
-Precursors in invertebrate chordates, similar genes expressed during neural plate development and migratory cells found in Urochordates
Placodes and brain division
-Complex sense organs
-Brain of vertebrates larger and has 3 parts (forebrain, midbrain and hindbrain)
-Brain of amphioxus (cephalochordate) not divided but genes similar except development of forebrain (as it has none)
Vertebrate size
-Vertebrates have increased body size and activity, cephalochordates up to 10cm long, while jawless vertebrates 10-100cm long
-Can’t rely on ciliary action or diffusion
-Higher metabolic rate due to being active
-Can sustain periods of anaerobic respiration, allowing for rapid movement before aerobic respiration can occur
-Transition from filter feeding to active, predaceous mode of life
Vertebrate changes to transition to active, predaceous mode of life
-Prescence of tail
-Three-chambered heart
-Muscle blocks (myomeres)
-Development of new organs
Mineralised tissues
-Arose in vertebrate evolution but absent at start
-Maximises strength but also provides flexibility
-Unique mineral hydroxyapatite (calcium and phosphorous)
-More resistant to lactic acid after anaerobic respiration
-Six types of tissues can be mineralised
What are mineralised tissues made of
-Collagen fibres, proteinaceous tissue matrix and hydroxyapatite
-Gives it a mix of hard and flexible materials
Mineralised tissue types
-Mineralised cartilage forms main mineralised internal skeleton of sharks/cartilaginous fishes
-Bone forms internal skeleton of bony fish and tetrapods, highly vascularised and endochondral bone replaces cartilage
-Enamel, enameloid and dentine are associated with teeth, exoskeletons and dermal scales of cartilaginous fishes etc (90-96% mineralised)
-Cementum fastens teeth in sockets (45% mineralised), found in mammals
Origin of bone and other mineralised tissues
-No mineralised tissues at start of vertebrate evolution
-Basic units in early vertebrates (odontodes (dermal)), e.g., dermal armour of ostracoderms
-Initially, there was an unmineralised condition, such as in lampreys, but exoskeleton evolved, followed by mineralised endoskeleton
-Bony fish still have exoskeleton-like mineralised tissues (scales and fins), while tetrapods have a reduction of exoskeleton in trunk region, retaining it in the skull
Why did mineralised tissues evolve?
-Defensive structure
-Protected electroreceptors
-Storage/regulation of phosphorous and calcium in hydroxyapatite
Extinct agnatha
-Ostracoderms
-Approx 500 MYA
-Jawless
-Dermal skeleton of odontodes that could aggrevate to form spine plates
-10-50cm
-Notochord
-Fed on soft bodied prey
-No mineralised internal skeleton
-Dorsal fin, some pectoral fins
-Lived along jawed fish for a time
-Extinct in late Devonian
Extinct cyclostome?
-Fossil of Tully monster found (Tullimonstrum)
-Been classed as many things
-Has arcualia and a notochord
-Also has keratin, found in tooth structures of extant cyclostomes
Present day cyclostome features
-Jawless
-No mineralised tissue
-No paired fins
-Very ancient group, split from other vertebrates very early
-Lampreys and hagfish
How do we know cyclostomes diverged from other vertebrates very early?
-Haemoglobin made of alpha and beta globins
-500 MYA ancestral globin gene duplicated to form these alpha and beta gene clusters
-All vertebrates except jawless vertebrates show this alpha/beta split
-This means that the common ancestor of lampreys and hagfish predates this split and diverged before this
Lamprey feeding
-Most predacious
-Latch onto prey but don’t usually cause death, but may weaken animal
-Have oral hood with tooth like structures and a tongue with same structures on
-Latches on with jaw hood and grinds at animal, eating blood and tissues
-Has glands that produce anticoagulants
Lamprey anadromity
-Males and females build nests with collected stones, releasing egg and sperm within
-Adults find streams by detecting pheremones released by larvae
-Females detect mature males, and adults also avoid some areas, possibly due to alarm cues released
-Adults die after spawning
Lamprey alarm cues
-Made up of bile acids (petromyzonol sulphate, petromyzonamine disulphate, petromyzosterl disulphate)
-Detected at low concentrations and produced in large quantities (each larva activates 400L/water/hour)
Lamprey features
-Notochord supports body, vertebrae minute (arcualia) and on dorsal surface
-Pineal eye
-Nasohypophyseal opening
-Simple gut
-Tidal ventilation
Nasohypophyseal opening of lampreys
-Similar to nostril
-Leads to an olfactory sac
-Several external gill openings
-Shares duct with adenohypopysis, an alternative to anterior pituitary gland
Tidal ventilation in lampreys
-Method of breathing
-Can’t operate gills while latched on
-Water goes in and out of branchial ducts
Larval lampreys
-Ammocoete, as originally thought to be seperate species
-Have endostyle to secret mucus for filter feeding
-Draw water into gills, mucus traps particles
-Endostyle becomes thyroid gland during metamorphosis
-Larval stage can last 5 years in freshwater
UK lamprey species
-Brook lamprey, around 20cm and doesn’t feed as adult
-River lampreys live in estuaries and coastal regions, sometimes Scottish Lochs
-Sea lampreys about 120cm long and found in coastal areas and the open ocean
Hagfish
-Marine and deep sea
-Notochord present
-Arcualia found ventrally in tail region
-Only vertebrates with blood isosmotic to sea
-No larval stage, direct development
-Not a lot known about them
-Exploited in eel skin trade and bycatch
-100:1 biased sex ratio to females, some known to be hermaphrodites
Hagfish senses
-Have barbels, sensory devices
-Eyes covered by skin so rely on sensory and olfactory information
Hagfish feeding
-Scavengers, feed on dead animals
-Have slime glands that produce copious amounts of slime for protection, but can also clog fish gills, so maybe predaceous
-Can acquire nutrients through skin and gills, unusual for animals
-Can tie themselves in a knot to get rid of slime for feeding, allowing to grip onto prey and pull bits off
Advantage of jaw
Ability to feed on a wider variety of prey
Vertebrates with jaws are called…
…gnathostomes
How did jaws evolve?
-Pharynx became muscular and gill slits now used for respiration instead of feeding, both supported by gill arches
-Jaws evolved from anterior branchial arches (mandibular arches)
-Arch immediately behind mandibular arch is hyoid arch, forming part of jaw but also allowing for suspension of jaw
-Gill reduced to spiracle
-Also involved duplication of Hox gene
Why evolve jaw?
-Arch enlargement aided ventilation, not feeding
-Monorhiny vs diplorhiny
Arch enlargement aided ventilation
-Functioned in closing and opening entrance to pharynx
-Allows for more activity
-However, mandibular ach doesn’t form a functional gill arch in any living vertebrate or fossil, no transition seen from jawless to jawed
-In lampreys, mandibular arch supports velum
-Lamprey and hagfish gill arches found on outside and gills inside, the reverse to gnathostomes, so not good example of transition either
-Mandibular arch has different developmental origin and innervation to rest of arches (the way that nerves control it)
-If hypothesis true, gnathostomes able to suck in prey and grasp it, making jaws selected to be large, leading to feeding
Monorhiny vs diplorhiny
-Single or two nostrils
-Hagfish and lampreys have single nostril and single olfactory sac that shares nostril with anterior pituitary gland
-Single nostril could have prevented evolution of upper jaw
-Some transitional forms found with two sacs but only one nostril, shared with AP gland
Paired and midline fins in jawed vertebrates
-Midline fins e.g., dorsal fin, anal fin (single) and caudal fin (tail)
-Paired fins not seen on jawless vertebrates, except some ostracoderms had pectoral fins
-Pelvic fins only seen in gnathostomes
-Fins allowed for more manoeuvrability
-Genes responsible for lamprey and dorsal fin are also responsible for midline and paired fins in bony fishes, meaning same genetic mechanism in different location
-Same gene controls limb development
Manoeuvrability of fins
-Pitch controlled by pelvic and pectoral (up and down)
-Yaw controlled by dorsal and anal (rolling)
Buoyancy in chondrichthyans
-Lipid-filled liver for neutral buoyancy (different method in bony fish (swim bladder))
-Amount of lipid and liver size vary (can be 25% of shark’s weight)
-Benthic fish have smaller livers
-High blood urea concentration also aids buoyancy
Hyostylic jaw suspension
-Upper jaw suspended from cranium by modified hyoid arch (hyomandibular) at back end
-Front end of upper jaw has ligaments
-Jaw can be flexible
-Seen in most chondrichthyans
Groups of chondrichthyans
-Holocephalans
-Elasmobranchs
Holocephalans
-Include rat fish Chimaera
-Show holostylic jaw suspension, cranium fused to upper jaw
-Deep sea, feed on crustaceans
-Have tooth plates to crush prey
-Large pectoral fins and whip-like tail
-Oviparous
-Proboscis rich in mechanoreceptors and electroreceptors
-Lateral line system for mechanoreceptors
-Spine on dorsal fin, can be venomous
Elasmobranchs
-Sharks, skates and rays
Sharks
-Can be split into 2 groups, galeomorphs and squalomorphs
-Range in sizes
-Gut is short
-Heterocercal tail, asymmetrical to maybe help with lifting animal while swimming
-Embedded in skin are teeth-like structures, called denticles, or placoid scales
Galeomorphs
-With anal fin
-Tend to be warmer water
-Includes great white shark and whale shark (biggest fish)
-Also includes thresher sharks with asymmetrical tail used as a whip that can stun with pressure or directly hit
Squalomoprhs
-No anal fin
-Tend to be in cold water
-Includes spiny dogfish
Shark unique species
-Cookie cutter shark uses teeth to eat chunks of prey
-Hammerhead shark thought to have head shape to improve binocular vision, as most sharks have 10% overlap in view, while hammerheads show 48%
Shark denticles/placoid scales
-Enameloid on outside, then dentine
-Can be arranged in different ways
-Minimise turbulence, allowing flow of water along body
-All face same way
-Maybe used to help feeding
-Denticles reduced in rays to a barb, and along the dorsal line in skates
Skates and rays (Blatoidea)
-Dorso-ventrally flattened
-Ventral side is where gill chambers and mouth located
-Dorsal side is where spiracle located, where water enters
-More diverse than sharks
-Enlarged pectoral fins
-Many benthic, some not such as eagle and manta ray (also can be up to 6m)
-Some produce electric currents, like the electric ray forms in muscle tissue of gills and uses to stun prey, other species produce in tail for communication
-Skates lay eggs, rays give birth live
Batoidea feeding
-Many benthic, jaw suspension allows to drop jaw and eat sand animals
-Teeth have flat plates to grind up crustacean and mollusc prey
-May be sexual dimorphism in some species for teeth, as males require sharp teeth for latching on to females during reproductive season, but flat for feeding
-Manta ray filter feeders, using extensions of pectoral fins (cephalic fins) that guide food into mouth, where it is trapped in gills
Chondrichthyan teeth whorl
-Not embedded into jaw, but into skin
-Teeth behind replace front ones
-Can kill mammals by exsanguination (bleeding to death)
Megaladon
-14-18m long
-Extinct 2.6 MYA
-Thought to be a major pressure on the sizes of baleen whales as were only predator
How do chondrichthyans hunt
-With sun behind them
-So that prey do not see them
Sensory systems in chondrichthyans
-Mechanoreceptors
-Chemoreceptors
-Electrical impulses
-Vision
-Brain
Mechanoreceptors chondrichthyans
-Detect vibrations
-Neuromast organs
-In lateral line
Chemoreceptors chondrichthyans
-Acute sense of smell
-Can detect 1 part in 10 billion
-Will turn to side first stimulated
-Sense of smell depends on size of olfactory bulbs, smaller in coral reef sharks
Electrical impulses chondrichthyans
-Ampullae of Lorenzini
-Found on head of sharks, pectoral fins of rays and skates, and rostrum of holocephalans
-Impulses produced by prey
Vision in chondrichthyans
-Well developed for low light intensities
-Rod rich retina
-Cells with crystals of guanine make up the tapetum luccidium behind retina
-Light reflects off tapetum luccidum back into the retina, maximising light
Brains of chondrichthyans
-Brains of sharks are proportionately heavier than brains of other fishes
-Similar brain-to-body mass ratios as some tetrapods
Sequence of systems in chondrichthyans
-Olfactory first, particularly if prey wounded
-OR mechanoreception
-Then vision to detect and recognise, may even butt head or gnaw to generate olfactory cues to help recognise
-Nictitating membrane protects eye
-An eyelid over eyes for electroreception
Reproduction in chondrichthyans
-May account for their success
-Sexual maturity reached later on in life
-Relied on a lot
-Internal fertilisation
-Male clasper inserted into female cloaca
-Clasper may have hooks and barbs to stay in place
-Sperm released from siphon sac, flowing down a groove and into female reproductive tract
-In smaller sharks, male wraps around female and may bite dorsal fin or flanks to hang on
-Some side by side, and bite pectoral fin
Oviparous sharks
-Lay eggs
-Mermaids purse tendrils wrap around vegetation to avoid washing up on shore
-Corckscrew eggs get stuck in rock crevices to ensure survival
-Have connections with outside via pores to ensure freshwater circulates for respiration
Ovoviviparous sharks
-Retain eggs in oviduct until hatching
-Nutrition from yolk (lecithotrophy)
Viviparous sharks
-Get nutrition from both yolk and female (matrotrophy)
-Some secrete substances such as uterine fluid
-Some continue to ovulate to feed young
-Some larvae eat each other
-Some have yolk sac placenta, yolk sac becomes heavily vascularised (placentotrophic viviparity)
-Once born/lain no parental care, investment is all in eggs or developing embryos
-Lifestyle involving lots of investment
Shark maturity
-Reproduce at old age
-White shark matures at 9-10 or 12-14 and produce 2-10 pups, every other year
-Greenland shark lives to 400 years, reproducing at 150
-Hammerhead produce 12-40 pups
What percentage of sharks are Critically Endangered
30
Actinopterygii features
-Homocercal tail
-Small scales
-Fusiform, torpedo shape effective for swimming
Actinopterygii fins
-Dorsal fins split in two
-Have pelvic and and anal fin
-Fins more for steering than movement with alternating contractions of muscles on each side, causing the animal to undulate side by side
-Most fish use back end of body, the caudal peduncle
-Lots of variation in fins
Actinopterygii fin variation
-Eels use most of body
-Some use specific fins
-Leafy sea dragons have tiny fins, making it a slow mover
-Guppies have brightly coloured fins for attracting mates and can have a sword that protrudes from fin, also have modified anal fin to form a gonopodium, an intromittent organ
-Flying fish can use fins to glide along surface of water rapidly to evade predation etc
Actinopterygii lateral line system
-Neuromast organs
-Detect water displacement
-For vibrations and flow etc
-Many fish that swim in shoals lack neuromast organs or are on head instead to avoid interference from other fish
How do actinopterygii achieve neutral buoyancy?
-Through swim bladder
-Thought to have originally been a lung structure
-Homologous with lungs of sarcopterygians
-Primitive fish lungs were ventral but flipped during course of evolution
-5-7% of body volume
-Pressure increases with depth, meaning swim bladder will shrink, causing animal to sink
-Pressure reduces nearer surface, increasing swim bladder and causing animal to rise
-However, for animal to swim wherever it wants, maintaining neutral buoyancy, the animal adjusts volume of gas in swim bladder
-To increase volume of swim bladder, it can gulp air, and to reduce volume, it can burp air out
-However, this is when it is connected to gut, other fish use blood to add or remove air
Actinopterygii respiration
-Most solely rely on gills
-Water flows in through mouth and out through gills, passing the operculum (gill covering)
-Gills are made of two columns of lamellae attached to gill arch
-Counter current exchange as blood moves in one direction, and water flows in opposite direction, maximising amount of oxygen taken up
-Some fast-moving fishes show ram ventilation, swimming around with mouth open (includes tunas and other pelagic fish)
-Some can do both ram and buccopharyngeal
Regional heterothermy
-Vessels from gills (cold) and vessels from muscles (10C higher than water due to movement) meet and exchange heat, heating gill levels
-Usually done around eye or brain region
-Helps fast-moving fish maintain muscle tissue at higher temperatures due to a countercurrent heat exchange system
Fish respiration in low oxygen areas
-May have vascularised anus to breathe oxygen, or thicker lips for gas exchange
-Anabantid fish are obligate air breathers and have gills but also have to breathe atmospheric oxygen by gulping air at surface
-Air enters labyrinth organ, where gaseous exchange takes place to provide supplementary oxygen
Eel features
-Studied for 1000s of years
-Lost pelvic fins, only have pectoral
-Typically live in crevices or reedy, grassy places
-Common to see this streamlined body in certain environments
-Also lost svales
-American and North European are distinguishable by number of vertebrae and mtDNA
-Catadromous, return to sea to breed
Eel breeding summary
-Discovered by Schmidt
-American and European eels bread in Sargasso sea, producing marine larva (leptocephalus) that metamorphose into glass eels *transition stage) and then again into freshwater eels
-Die after breeding
-Leptocephalus to elver takes 3 years in European, 1 in American due to proximity to Sargasso sea
-Thought that Sargasso sea used to be equidistant, but has changed due to continental drift
Sarcopterygian examples
-Lungfish
-Coelacanth
-Those that gave rise to tetrapods
Lungfish
-3 genera
-Closer related to tetrapods than coelacanths
-Includes Australian, African, and South American
-Australian have well developed lobe fins and thick scales, not seen in others
-All have lungs (and gills) and in the case of African and S American, use lungs for breathing
-Australian mainly breathe with gills as live in permanent water bodies
-African and S American move in a particular way, using reduced pelvic fins
-S American are not well studied, males have gill-like structures that help gaseous exchange as males look after offspring and can exchange gas with developing embryos
African lungfish
-Most well-studied
-Live in areas prone to flooding and drying out
-When area dries up, they burrow into bottom mud to form a cocoon
-Cover themselves in mucus and leave a hole to breathe at top of chamber
-Known as aestivation and is seen in other animals when conditions are unfavourable
-Can stay like this for a while
Coelacanths
-Thought to have gone extinct 80 MYA
-However, an extant coelacanth discovered in 1938 by Marjorie Courtenay-Latimer, a curator in a South African museum
-Fished from Comoros islands, Latimeria
-Tried to preserve as best as could
-Another found in Indonesia 1998 in fish market
-Large (2m) deep water nocturnal fish
-Don’t use fins as props, swim in undulatory way
-Vestigial fat-filled lung and retain urea in tissues and blood as buoyancy aid
-Electroreceptor organ on top of nose for detection of prey etc
-Viviparous, internal fertilisation
-Suction feeders
Tetrapodomorph fishes
-Fishes with tetrapod features
-Osteolepiforms
-Elpistostegalians
-Tiktaalik
-Spiracular region (remains of gill chamber after jaw formation) is different to other fish, the beginnings of tetrapod middle year
Osteolepiforms
-Large-bodied fish
-Eusthenopteron is a well-known example with well-developed fins
-Small ribs that point dorsally