What are the components of the appendicular skeleton?
The appendicular skeleton consists of the pectoral girdle plus limbs/fins and the pelvic girdle plus limbs/fins.
The anterior limbs of tetrapods are organized:
* Brachium – humerus
* Antebrachium – radius and ulna
* Carpus – carpals
* Metacarpus – palm
* Digits – phalanges
The posterior limbs of tetrapods are organized:
* Femur – femur
* Crus – tibia and fibula
* Tarus – tarsals
* Metatarsus – instep
* Digits – phalanges
Which groups lack an appendicular skeleton?
Apodans, snakes and some snake-like lizards do not have appendicular skeletal systems.
In tetrapods it is formed by three endochondral bones:
The illium is attached to the vertebral column via the sacral region. There is evidence in the fossil record regarding the evolution of the pelvic girdle.
Dinosaurs pelvic regions can be divided into two main types:
* Saurischians – pelvic girdle with three radiating bones
* Ornithischians – hip with pubis and ischium lying parallel and next to each other
What structural modification(s) have taken place in the appendicular skeleton to accommodate the transition from the aquatic to the terrestrial environment?
To transition from water to land required some modifications. The attachment of the pectoral girdle to the skull was lost. This allowed for an increase in movement of the head. The limbs and girdles became larger and reinforced to permit a more terrestrial lifestyle. They were able to hold the weight of the organisms as they moved. The fins were replaced by digits.
Explain how the axial and appendicular skeletal structures participate in locomotion. What limb
modifications are associated with cursorality?
The early modes of transportation is to establishing points of pivot. This generally remains constant today. The femurn and the humerus rotate the digits in line with the direction of travel. Cursorial refers to tetrapods that are specialized for running. The modifications include a lengthening of the limb elements, lightening the distal end of the limb to reduce mass, and reducing the number of digits.
Are there structural differences between the pelvises of males and females?
There are very noticable structural changes between the pelvic of a male and that of a female. The birth
canal of the female must accomadate the descending head of the fetus, therefore the pelvic region of
females are much more wider than males.
What is the main function of fins? What is their general structure? In sharks, what do pectoral fins do?
Fins are used primarily to give the fish increased stability as it glides through the water. In sharks this remains constant. Pectoral fins...