11Vertebral Development Sclerotome = forms vertebral elementsMyotome = forms muscleBoth separated into segments when the somites form.Vertical myosepta exist between segments of myotome (derived from the somite) .The myotome is also divided by a horizontal septum.Neural & hemal arches are centered on the vertical myosepta.
20Comparative Vertebra Structure Hagfishes lack vertebral structures.Neural arches dorsal to notochord surrounds dorsal nerve cord.Neural spines project above neural archHemal arches ventral to notochord around blood vessels in “tail”Hemal spines project below hemal archnotochord
21Vertebral CentraCentrum = solid bone or cartilage vertebral “segment;” “replaces” part of notochordIntervertebral pads = separate centra; derived, in part, from the notochordCentra evolved at least three times in vertebrates (Chondrichthys, Tetrapoda, & Amia + Teleosts)
22Vertebral Regionalization Non-tetrapod vertebratesTrunk (Thoracic, Abdominal) vertebrae = anterior; often bear ribs, lack hemal archesCaudal vertebrae = posterior; rarely bear ribs, have hemal archesTetrapodsHave Ant. & Post. Articulatory ProcessesCervical vertebrae = neck vertebraeThoracic vertebrae = have ribs(Lumbar vertebrae = lack ribs)Sacral vertebrae = attached to pelvic girdle
24Bird Vertebral Regionalization Synsacral vertebrae = vertebrae attached to pelvic girdle (homologs of sacral, lumbar, some thoracic and some caudal vertebrae)
25Cervical: Atlas & Axis Atlas = first cervical vertebra in tetrapods; reduced centrum, large neural canalAxis = second cervical vertebra in amniotes (Lissamphibians have only 1 cervical vertebra, an atlas.);odontoid process (dens) for rotation of atlas, large neural canalAtlas/Occipital Condyle joint = tiltingAtlas/Axis joint = rotation
26Vertebral Regionalization GroupTrunk Vertebrae“fish”: hagfishes, lampreys, chondrichthyans, lungfish, actinopterygiians,many trunk (number greatly variable)amphibians1 cervical, few to many trunk, 1 sacralmammals7 cervical, trunk (9-20 thoracic & 4-7 lumbar), 3-5 sacral,turtles, lizards & snakes, & crocodilians7-9 cervical, few to many trunk (especially many in snakes), 2 sacral (0 in snakes)birds11-25 cervical, trunk, synsacralCaudal (“Tail”) Vertebrae vary greatly in number, even within groups.
27Subphylum Vertebrata Actinopterygii Chondrichthys coelacanths amphibianshagfisheslungfisheslampreysMammaliaReptiliaR S G ATcentracentraaxis,>1 sacralvertebrae(Amniota)centra;atlas; sacralvertebrae; articulatory processes
28Ribs Form within myosepta from cartilage. Dorsal ribs form where the myoseptum intersects the horizontal septumVentral ribs form where the myoseptum intersects the coelom somatic mesoderm.HOMOLOGY CONTROVERSY
32SternumSternum (midventral endochondral element) where ribs often articulateEvolved independently in most groups.Mammalian sternum composed of multiple ossified elements (stern - ebrae); manubrium = 1st; xiphisternum/xiphoid process = last
57Amniote Pectoral Girdles Clavicles & interclavicle in turtle ventral shell.furcula = fused clavicles & interclavicle in birds.postcoracoid = endochondral ossification unique to mammals; fuses to scapula in therians (= coracoid process of scapula)Therian mammals lack interclavicle and coracoid.
60Endochondral Pectoral Girdle GroupscapulacoracoidpostcoracoidChondrichthyspresent, fused to →present, fused to ←absentreedfishespresentsturgeons & paddlefish, gars, & Amiateleostslungfishesamphibianssometimes fused to →sometimes fused to ←monotremesTheriapresent, fused to scapula (= coracoid process)Reptilia
61Subphylum Vertebrata Actinopterygii Chondrichthys coelacanths **loss of interclavicle*loss of claviclesActinopterygiiChondrichthyscoelacanthsamphibianshagfisheslungfisheslampreysMammaliaReptiliaR S G AT***loss ofcleithrum,supracleithrum,& posttemporal(have “neck”)(Tetrapoda)dermalpec. girdle(Osteichthys)pectoral &pelvic appendages (Gnathostomata)
66Amniote Pelvic Girdles In Archosaurs the acetabulum is “perforated.”In birds the 3 pelvic bones fuse (innominate bone); form a synsacrum.In mammals the 3 pelvic bones often fuse (innominate bone).ilpuisanteriorbird
69Tetrapod Digit Terminology Manus = “hand”Pes = “foot”Digits numbered anterior to posterior. Ancestrally 5 digits per limb in amniotes .Pollux = “thumb;” digit I of manusHallux = “big toe;” digit I of pesPhalangeal formula = number of phalanges in each digit starting with digit I.(e.g., )
73Bird Manus & Pes Birds: much fusion of elements Only 2 free carpals Carpometacarpus = distal carpals + metacarpals of digits III & IVTibiotarsus = tibia + proximal tarsalsTarsometatarsus = distal tarsals + metatarsals
74Amniote Manus & PesTalus = tibiale + intermedium (called Astragalus in non-mammals)Mammals - Maximum of only 1 free centrale (humans = 0 in manus, 1 in pes)Pisiform = sesamoid ossification on manusCalcaneus = fibulare with posterior process; forms heel
75Genetralized Amniote Pes phalangesVIVdistal tarsalsmeta-tarsalsCalcaneus(fibulare)fibula54312III4312tibiaIIcentralesAstragalus(tibiale +intermedium)I