CVA Lab 9-10/Lecture 10-11 (Axial & Appendicular Skeleton)

Axial skeleton

The skull and vertebral column, which play a major role in locomotion, protection, support, and display

Structure of vertebrae

Neural arch with intervertebral foramina, vertebral centra, and hemal arch extended around the caudal artery and vein. Provide attachment sites for muscles, protection for the spinal cord/blood vessels, and used in display.

Vertebral centra

Most vertebrates (neopterygians and terrestrial tetrapods) replace the notochord with this, which unites the arches. Collectively they form the vertebral column.

Amphicoelous vertebrae

Vertebrae shape where both ends are cupped. Fibrous intervertebral pads unite the centra

Procoelous vertebrae

Vertebrae shape similar to ball-and-socket, with cup facing forward. The knob on the opposing end often forms from the ossification of the intervertebral pad

Opistocoelous vertebrae

Vertebrae shape similar to ball-and-socket, with cup facing backward. The knob on the opposing end often forms from the ossification of the intervertebral pad

Biconvex first caudal

Crocodilians have mostly procoelous vertebrae, plus one acoelous sacral, and this additional vertebrae unique to them

Acoelous vertebrae

Vertebrae shape where both ends are flattened, trunk vertebrae

Heterocoelous vertebrae

Vertebrae shape found in cervical structure of birds that contains a saddle joint, allowing extreme movement. The cupping makes it so the spinal cord does not stretch as much compared to acoelous vertebrae

Zygapophyses

Vertebral processes between neural arches, are found in some teleosts and especially in terrestrial tetrapods. They increase the vertebral column rigidity, and limit movements to certain directions

Transverse Processes

Vertebral processes formed laterally on the vertebrae, serve as attachment points for muscles and ribs.

Ribs

These structures begin formation away from the vertebrae and thus are not transverse processes. They strengthen the mysepta and provide attachment points for muscles, they can protect the abdominal contents especially when laying prone or from impacts, and they aid ventilation in most amniotes. Snakes “walk” with them.

upper tuberculum and lower capitulum

The two “heads” on an individual rib that attach it to the transverse processes and the centrum of vertebrae

Sternum

Breastbone present in most terrestrial vertebrates, it is a muscle attachment site. In amniotes most trunk ribs attach to it and it aids in ventilation. It is cartilaginous but can ossify. Strongly keeled in birds for attachment of flight muscles.

Notochord

Early fish that do not swim powerfully or rapidly have no centra, and have this instead

Trunk vertebrae

Vertebrae in the torso section of a fish, with the first one modified to attach to the skull. In terrestrial tetrapods, they are all the same shape. In birds, they are separated into thoracic with ribs and lumbar without.

Caudal vertebrae

Vertebrae in a fish designed to protect the caudal artery and veins and the hemal arches.

Balanced homocercal tails

What actinopterygians evolved alongside swim bladders and lungs

Balanced diphycercal tails

What actinistians evolved alongside swim bladders and lungs

Fishlike undulations

Movement retained by the first tetrapods on land (as well as early amphibians and reptilomorphs)

single atlas

In terrestrial tetrapods a neck formed with this structure to allow head movements when foraging

single sacral vertebrae

In terrestrial tetrapods, this structure evolved to support the hind leg’s thrust and gravity

Pectoral girdle

In almost all vertebrates, the structure that is supported by a muscular sling with no bones involved

Reptilomorphs

In this species, the notochord remains as intervertebral disks and the nucleus pulposus, the axis evolved, more cervical vertebrae became present allowing more movement, ribs are used extensively for ventilation of the lungs, and two vertebrae composed the sacrum

Synsacrum

The two sacral vertebrae from reptilomorph ancestry are fused as well as several lumbars and caudals to form this structure in birds (10-23 vertebrae).

Pygostyle

United caudal vertebrae in birds that support the tail feathers

Uncinate process

Processes off the sternal portion of the ribs that allow the attachment of respiratory muscles

Mammalian vertebrae

In this species group, the vertebral column is differentiated into five groups (cervical, thoracic, lumbar, sacral, caudal). Almost all have seven cervical vertebrae even in giraffes. Whales fuse them up as do jumping rodents and kangaroos to prevent head bobbing. The atlas and particularly the axis are highly mobile. Ribs heavily involved in diaphragm breathing. Sacrum has at least three fused vertebrae like dinosaurs, humans have five.

dual-condyle system

A system evolved from the single condyle reptilomorph condition seen in therapsids

Dens

In mammals, portion of the axis that probably incorporates parts of the its own centrum (the pleurocentrum) and that of the Atlas (a remnant of the intercentrum)

Coccyx

The tailbone, formed from 3-5 fused caudal vertebrae in humans.

Cetacean & Whale Reversions

Cervical vertebrae (neck) fused, zygapophyses which resist dorso-ventral movements are lost except for anterior thoracic vertebrae, extra lumbar vertebrae with metapophyses on the bases of the neural spines to resist lateral bending

Appendicular skeleton

consists of the pectoral and pelvic appendages and their girdles

Pterygiophores

Endoskeletal bases of the fins, with which inward extensions probably formed the girdles

overlying dermal plates

This contributed to the dermal component in the pectoral region

clavicle and cleithrum

the precursors to the dermal elements found in later vertebrate girdles

endochondral scapulocoracoid cartilage

Structure that attaches the pectoral fin

Posttemporal bone

Structure that links the pectoral girdle to the skull

Scapulocoracoid girdle

Girdle in early chondrichthyans with no major dermal bones, just a single layer of radial pterygiophores (endochondral elements)

Many basal pterygiophores deep to the radials

Acanthodians developed a second layer of pterygiophores for the scapulocoracoid girdle, which became this structure important to tetrapod development

Three basal pterygiophores linking the fin to the now separate scapula and coracoid

Actinopterygians were the first to get rotatable, short-based fins using this structural setup

Single basal pterygiophore

Sarcopterygians have this structure setup to attach their fins to girdles

basal pterygiophores and more distal bones

Homologs of the Femur and Humerus, and homologs of the tibia and fibula, and radius and ulna, respectively

Pelvic girdle

will later form the pelvic bones of derived tetrapods (i.e. Pubis, Ischium, and Ilium)

Cheiropterygium

AKA chiridium, a limb with a hand/foot and distinctive digits (fingers/toes), originating in tetrapods

Stylopodium

Element in limb closest to the torso, containing a single humerus/femur

Zeugopodium

Dual-element in limb midway from torso, containing a radius/ulna or tibia/fibula

Autopodium

Multi-element in limb furthest from torso, first containing tarsals/carpals, then metatarsals/metacarpals, then digits (phalanges)

2-3-3-3-3

Most terrestrial tetrapods primitively have five metapodials and digits numbered 1-5 starting from the thumb/big toe. What is the human formula for phalanges in these digits?

Sprawling

Early terrestrial limbs, the humerus and femur, projected laterally in this way

Glenoid fossa

Bowl in the scapulocoracoid where the humerus is attached in early tetrapods

Necks

Dermal elements in tetrapod pectoral girdles were reduced to just the cleithrum, clavicle and interclavicle (a sarcopterygian feature). Without the posttemporal bone what was able to develop?

Ilium

Section of the pelvic girdle that attached to a single sacral vertebrae and a set of sacral ribs. The femur went into the acetabulum within this structure.

Ischium

Pubis