Pan Tetrapoda Flashcards
Crown Tetrapoda (352) is defined by the split between
Amniota and Amphibia
Stem Tetrapods
Rhizodontids, ‘Osteolepiforms’, Panderichthyes, Tiktaalik, Acanthostega, Ichthyostega, Whatcheeridae
Rhizodontids
Stem Tetrapods
- shallow marine and freshwater
- largest freshwater “fish”
- shoulder girdle and brain case well preserved
- reduced dorsal, anal, and pelvic fins
“Osteolepiforms”
Paraphyletic Stem Tetrapods
- ventral cranial fissure, large choanae, tetrapod skull patterning
- 1t evidence of bone marrow
Tiktaalik
Found on Ellesmere Island
-flat skull, no dorsal, anal fin, retains lepidotrichia, pectoral fin expanded, enlarged pelvis
- more tetrapod like shoulder girdle
- operculum lost
–pectoral girdle not attached to head = neck mobility
-enlarged ribs
-elongated snout
Acanthostega
Stem Tetrapod found in Greenland
- digits! At least 8
- lacked ossified wrists
- shoulder girdle
- retains well-developed gill arch and skeleton
- pectoral girdle detached from skull
Icthyostega
Stem tetrapods found in Greenland
- very similar to Acanthostega
- limbs, vertebrae, ribs
- pelvic appendage “catching up”
- more capable to terrestrial locomotion, but is primarily aquatic
Whatcheeridae
Stem Tetrapods found in Scotland
- foot has 5 digits
- 5 robust digits +1 extra, so 6 is primitive
What are the Fin/Limb Character Transformations of Vertebrates?
Fins to Limb - separation of the pectoral girdle from head, basically a neck!
Fin/Limb positioning along AP axis
Fins to Limb - separation of pectoral girdle from head
Neck!
Spinal Cord
- dual innervation of pectoral fins by cranial and spinal nerves in non-tetrapod gnathostomes
- hypothesized caudal shift of Hox expression shifted innervationpattern of “forelimbs” in tetrapods
—response of part displacement of the pectoral girdle along tetrapod stem
Fin/Limb positioning along AP axis- Hox genes
Forelimb, interlimb, hindlimb: Hox expression in LP
- anterior limit for expression - key features
General Limb Development
1) Hox expression field determines AP positioning of limb buds (somatopluere, core of LP,, etc)
2) Limb Buds - outgrowth of LP mesenchyme + surface ectoderm
3) Fibroblast growth factor (Fgf) 10 expression in LP mesenchyme establishes Apical Ectodermal Region (AER) in adjacent ectoderm
4) AER expression for fgf4 and 8, which maintains 10 expression in LP
A) appositional growth of limb bud
B) co-optation of Hox exp filled patterns proximal-distal axis
—girdle-style pod-zeugopod-autopod
5) AER exp 4 and 8 which establishes and maintains zone of polarizing activity (ZPA)
6) ZPA establishes Shh gradient = patterns AP axis
- morph. Identities of digits - Shh gradient
7) DV axis = WNT (dorsal)Engrailed/En (ventral) gradient
Appendicular Skeleton - Gnathostome
“Internal” Fin structure = girdles w/o radials
What are the components of the Pectoral Girdle of Vertebrates
Cleithrum, scapula, coracoid, clavicle, etc
Cleithrum
Part of pectoral girdle in vertebrates
Large, dorsal; serves as attachment to upper cucullaris muscles
Scapula and coracoid does what
Start sepration
Scapula
Part of pectoral girdle
Glenoid fossa
Coracoid
Part of pectoral girdle
Will brace shoulder girdle against sternum
Clavicle
Part of pec. Girdle
Braces shoulder girdle to sternum; attached
In Gnathostomes, there are paired fins, what are its structures?
From dorsal to ventral:
Lepidotrichia
Radials
Left to right:
Propterygium, mesopterygium, metapterygium
In Chondrichthyes and Osteichthyes, what are the structures of limbs?
Along the stem, there is a reduction of the basal elements, radials are restricted to metapterygium
Along Stem Actinopterygia: there is a relative enlargement of petapterygium
Pan Actinisia + Pan-Dipnoa: established metapterygium axis
Pan TetrapodaL reduction of lepidotrichia, meta= stylopod and zeugopod +carpals/tarsals
- Radials = digits
- Digit 4 = meta, Digits 1-3 pre axial digits, Digit 5 = postaxial
What is the spiracle?
A hole near the eye and is a respiratory structure
IN Stem Tetrapods Acanthostega and Icthyostega, it is a spiracular notch = otic/tympanic note
Spiracle = fenestra vestibuli
Hyomandibular = stapes
Ears: Organ of Balance
Evolved from lateral line system
Turning Head
Lag in endolymph, movement displaces hair cells
Via C VIII/vestibulocochlear nerve
Christa, macula
Crista
Sensory organ inside ampulla of semicircular canals
Macula
Modified neuromast organ
- calcium carbonate concretions
What is the Octaval System
Vestibular and Auditory System
What are the components of the Acoustic Ear
Middle ear: typanum, middle ear cavity & one or more ossicles
Transforms sound waves in air into waves in fluid
Tympanum
Collects and amplifies sound waves
- otic notch
-1st pharyngeal septum
Stapes
Hyoid arch
Hyomandibular
Propagates sound waves from typanum to fenestra vestibuli
Across 1st pharyngeal pouch
Crown Tetrapoda (352) is defined by the split between
Amniota and Amphibia
Crown Amphibia
> 7000 species
3 major classes: frogs, salamanders and caecilians
Lay eggs
Skin is a significant respiratory organ, cutaneous respiration
Impudence - matching ear
Opercular - amphibian papilla system
Pedicellate teeth
Crown Apoda- Caecilians/Gymnophonia
Reduced eyes, but not all blind
No tail
Tentacle near nostril or eye and protrusible
Crown Caudata
Salamanders!
Retain train (hence name)
Lack tympanum and 1st pharyngeal pouch
Rely on olfactory cues
Crown Anura: Frogs
90% amphibians
Rely on visual and auditory
Large mouths & eyes
No teeth on dentary
Fused zeugopod
3 main groups of frogs: archaeobatrachidae (para), mesobatrachia, neobatrachia (mono)
What are the three main groups of frogs
Archaeobatrachidae, mesobatrachia and neobatrachia
What are the different theories of Amphibian and Amniota Origins
Ruta Hypothesis
Temnospondyls are stem amphibians and Lepospondyls are stem Amniotes
Lauren Hypothesis
Lepospondyls are stem amphibians’Temnospondys are outside of the crown f tetrapod
(A note stem is severely reduced)
Crown Amniota is defined by the split between
Mammalia and Reptilia
The Amniotic Egg is characterized by
Chorion (gas exchange)
Allantois (stores waste)
Yolk sac (stores nutrients)
Amnion (water source)
Stem Amniotes
Anthracosauridae, Seymouriamorphs, Diasdectomorphc
Joggins Formation
306 MA, Nova cottage
Early stem reptile hot spot
Hylonomus, Archaeothyris forensis, Petrolacosaurus Kansasensis
Hylonomus
Stem Reptile and is anapsid
Archaeothyris florensis
Synapsid conditon
Petrolacosaurus Kansasensis
Diapsid condition
