Evolutionary Anatomy of the Vertebrate Study guide 3A – The vertebrate head There is some overlap with this study guide and the head section from midterm 2; you can expect to see any of the material on the portion of the class on the head on the final. Can you summarize the three components (dermal, endochondral, pharyngeal arch) that give rise to the skull in vertebrates and what they contribute? Chondrocranium- encases the brain and sensory organs; Evolutionarily become more posterior and ventral; brain and sensory encaser Developmentally endochondral bone; preformed in cartilage cartilage-replacement bone Nasal Otic Occipital Ethmoid Sphenoid (sphenethmoid)- fills in brain case anterior to occipital Dermocranium- covers chondocranium and splanchnocranium Evolutionarily dermal shield Developmentally comes from dermal layer of the skin Facial Premaxilla, maxilla Palatal palatine, pterygoid Cheek Jugal, postorbital, squamosal Roof nasal, frontal, parietal Jaw dentary Splanchnocranium Evolutionarily from visceral arches (cartilage that supports gills) Developmentally cartilage- somewhat ossified Upper Jaw palatoquadrate (quadrate and epipterygoid) quadrate =incus and epipterygoid = alisphenoid Lower Jaw mandibular cartilage (articular bone) malleus Hyomandibula jaw suspension stapes Could you identify whether a skull is from a shark, bony fish, amphibian, turtle, reptile, bird or mammal? Shark cartilaginous skeleton = only condrocranium Jaw palatoquadrate + Mandibular cartilage + hyomandibula Bony fish tones of many little, segmented dermal plates
Amphibian diapsids 2 huge fenestra + flat skull Turtle anapsid no fenestra dermal bone Reptile anterior choanae primitive = sphenedon = DIAPSID 2 fenestra with the jugal bone forming the lower bar upper bar= post-orbital + squamosal derived = modified DIAPSID
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