Comparative Anatomy Study Guide, Exam II
Synarthroses - immovable joints: skull sutures
Amphiarthrosis - slightly movable joints: intervertebral joints
Diarthrodial - freely movable joints = synovial joints.
Synovial joint - joint capsule, fibrous capsule and synovial membrane, synovial fluid, hyaline
cartilage, reinforcing ligaments.
The Skeleton: Cranium.
Three primary moieties:
1. Dermatocranium - skull roofing bones (dermal portions)
2. Chondrocranium - braincase (endochondral portions)
3. Splanchnocranium - visceral arches
Skull development - know chondrocrianium developmental pattern.
Know which bones are derived from the chondrocranium, which from dermatocranium,
which from splanchnocranium.
Evolution of the Cranium.
Primitive agnathans: Ostracoderms - heavy, external, armor plates covered head and anterior body.
Extant agnathans - skeleton degenerate, cartilaginous elements only. Splanchnocranium external
to branchial basket.
Chondrichthyes - skeleton also degenerate. Cartilaginous elements only. Chondrocranium well
developed, roofed over dorsally. Splanchnocranial elements deep to gill chambers.
Jaws present: palatoquadrate & meckel's cartilages apparently derived from first gill arch.
Osteichthyes - well developed dermatocrania. Homology of individual elements not always clear in
Gill chamber covered by a single, bony operculum in osteichthyes.
Rhipidistia - Braincase divided into two separate portions that are movably articulated (cranial
Posterior end of braincase penetrated by notochord.
Pineal foramen present between parietals.
Palatal bones invested with labyrinthodont teeth.
Postorbital portion of skull elongate, preorbital portion short.
Dipnoi (lungfishes) – braincase remains largely cartilaginous, dermal roofing bones reduced. Maxillae
and premaxillae lost in modern forms.
Crushing palatal tooth plates.
No intracranial hinge joint.
Tetrapods – Skulls of earliest amphibians similar to those of advanced rhipidistians:
1) Homologous roofing bones present, 2) Pineal foramen present, 3) labyrinthodont teeth present, 4) Intracranial joint present, 5) posterior portion of cranium penetrated by notochord, 6) Clear homologies between bones of palate.
Differences from rhipidisians: Preorbital skull elongate, postorbital skull shortened.
Lissamphibia – extensive loss of skull bones and fenestration of skull.
Much of chondrocranium persistently cartilaginous in frogs and salamanders.
Occipital condyles paired.
Amniota – Primitive skull similar to that of labyrinthodont amphibians except: less flattened, eyes laterally directed (dorsally directed in labyrinthodonts), snout region reduced in length.
Intertemporal, supratemporal, tabular and postparietal. bones lost from posterior skull table.
Amniote skulls classified on basis of temporal openings:
Anapsida – temporal fenestrae absent: Turtles.
Diapsida – two temporal fenestrae, one dorsal, one ventral: Archosaurs and Lepidosaurs.
Synapsida – only the lower temporal fenestra is present: Pelycosaurs, Therapsids, Mammals.
“Euryapsida” – probably modified diapsids, only upper temporal fenestra present: Plesiosaurs
Pelycosaurs have single occipital condyle, expanded epipterygoid.
Therapsids have double occipital condyle, secondary palate develops, dentary bone increases in size until
other bones are all displaced.
Mammals – complete secondary palate: premaxillae, maxillae and palatines contribute.
Epipterygoid becomes alisphenoid
Temporal bone formed from squamosal, Petrous portion (prootic + opisthotic), and tympanic
Supraoccipital, exoccipitals, and basioccipital fuse to form occipital bone
Squamosal-dentary articulation completed
Angular becomes tympanic bone, columella becomes stapes, articular becomes malleus, and
quadrate becomes incus.
Parietals and frontals grow downward and inward below old skull roof to complete sides of
Diapsida – single
Lepidosaurs primitively have full complement of temporal arches and fenestrae
Lizards lose lower temporal arch and fenestra.
Snakes have lost both temporal arches and fenestrae, braincase enclosed by downgrowth of frontals and parietals. Skull becomes highly kinetic.
Archosauria – skull heavily
crocodilia, no kinesis.
Skull pneumatized with a series of interconnecting channels.
Snout fenestrated in many forms, e.g. dinosaurs.
postorbital bar lost
Braincase closed by a dermal laterosphenoid
Teeth lost entirely, functionally replaced by beak (as in turtles)
Single occipital condyle
Enlarge orbit: sclerotic ossicles present (as in some other reptiles)
Skull kinetic w/ hinge joint at nasofrontal suture and independently mobile quadrates and bony
Vertebral column: Development. Understand resegmentation.
Evolution of vertebral column.
groups have only notochord w/ a few cartilaginous arch
Sarcopterygia – arches develop neural spines and hemal spines. Rudimentary centrum elements develop.
advanced fishes (including chondrichthyans and osteichthyans)
develop amphicoelous centra.
Arch bases present.
Neural arches well developed, but lack zygapophyses.
Sharks develop intercalary cartilages between neural arches.
Ribs – know
In fishes: two types: dorsal and ventral ribs. Tetrapod rib homologous to dorsal.
between rib and vertebrae (articulation points)
Uncinate processes – what are they? (see birds)
– composed of sternebrae in some vertebrates, fused in others
Paired appendages absent in earliest vertebrates.
Median fins effective in preventing roll and yaw
Appendicular fins effective in preventing roll and pitch
Appendicular fins with narrow, moveable basal joint also useful for
steering and braking
as well as for slow locomotion in some groups.
Origins of appendages:
Know two theories:
Gill arch theory of Gegenbaur
Fin fold theory of Balfour and Thacher
Parts of fin
Parts of tetrapod
Basal pterygiophores stylopodium
Radial pterygiophores zeugopodium
Cleithrum, clavicle and interclavicle
Endochondral elements: scapulocoracoid – scapula, procoracoid and coracoid
Know which taxa have these parts.
Know phylogenetic progression of anatomy.
What is the furculum?
Know digital formulae,
Understand adaptive changes in foot morphology that have occurred, for example, in frogs, which
have a saltatorial style of locomotion.
Know plantigrade, digitigrade and unguligrade foot postures in
Which types of mammals have which types of posture?
are the primary effectors in the vertebrate body.
All forms of movement in vertebrates are produced by muscles
Three types of
muscle tissue: striated, cardiac, and smooth.
This section is primarily concerned with striated muscle tissue.
Muscle cells are generally referred to as fibers.
Know terminology of fiber parts: sarcolemma, sarcoplasm, myofibrils, myofilaments, myosin and actin.
Know the muscle subunits and their connective tissue coverings:
epimysium, fascicles and perimysium,
fibers and endomysium.
Connective tissue attachments are tendons and aponeuroses.
Muscle morphology: strap-like, spindle-shaped and pennate.
Three types of pennate muscle
include: unipennate, bipennate and multipennate. Muscles may also be segmented.
Know the relationships among the following:
Paraxial mesoderm Myotome
Extrinsic ocular muscles: 4 rectus, 2 obliques, retractor bulbi and levator palpebrae (the latter
2 are only in tetrapods).
Appendicular musc. (derived from hypax.)
Patterns of the major
muscle groups, including the ocular muscles, epaxial,
hypaxial, branchiomeric, appendicular and branchial musculature in various groups, especially the
Organs: be able to
explain and diagram an electroplaque. Give
examples of fish that have
these. What are their uses?
anatomical structure of a typical mammalian tooth.
dental formulae. Know the primitive
metatherian and eutherian formulae and some
other examples, such as cat and human.
Heterodonty Bunodonty Thecodont
Polyphyodonty Selenodonty Acrodont
Diphyodonty Lophodonty Pleurodont
Deciduous dentition Carnassial dentition
See also: handout
Exam date changes: Lecture Exam II
will be held on Wednesday, October 29. It will cover everything
the lecture on joints to the lecture on dentition, inclusive.
Lab Practical II will be postponed until Thursday, November 6, and will cover the entire
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