MAVet's entire collection of skeletons and anatomical differences between classes.
The vertebrate skeleton is distinguished in an axial portion, consisting of skull, vertebral column and ribs and sternum (where present), and an appendicular portion, made up of even and uneven appendages (fins and articulated limbs) and girdles (pectoral and pelvic). The skull specializes in relation to the development of the brain (neurocranium) and the sense organs (splancnocranium), which receives and protects, but also in relation to the buccal opening and branchial region. It also represents the skeletal scaffolding of the mouth, as well as the organ for capturing and crushing the food. It also contains the first part of the respiratory system. Observing the skull of the 5 classes of Vertebrates (Pisces, Amphibians, Reptiles, Mammals and Birds) it is possible to notice how during evolution it has undergone modifications. The first modification led to the formation of the maxilla and the mandible, determining in the Pisces the distinction in Agnati (without jaw and mandible) and Gnatostomi (with jaw and mandible).
The successive classes to Pisces are all characterized by jaw and jaw with a specialization of the joint determined by the type of feeding. The vertebral column, so called due to its constitution of metamerically repeating bones, called vertebrae, represents the axial skeleton that stands out in different regions depending on the class of Vertebrates. In the Pisces we can distinguish only two regions: trunk and caudal, while with the passage to terrestrial life, to support the body weight, in the vertebral column, the sacral region appears, where most of the weight itself is discharged, through the insertion of the limbs rear. In addition, further differentiation occurs in the cervical region to allow movement of the neck and head.
The vertebrates that live on land are further identified as Tetrapods, due to the presence of 4 limbs (thoracic and pelvic). Therefore in the vertebral column of a tetrapod we can recognize different regions: cervical, thoracic, lumbar, sacral and caudal. The vertebral column of the Gnathostomy Fishes in the trunk region is characterized by ribbed vertebrae, which are missing in those of the caudal region. The cervical region of the Amphibians specializes and presents only one cervical vertebra, called the atlas, thus determining the rotation of the skull on the vertebral column. Follows a thoracic region in which the vertebrae are articulated with short ribs only in the Urodeles, Amphibians with tail, mentren he Anuris, Amphibians without tail, the ribs are rudimentary and fused with the thoracic vertebrae. The sacral region has only one vertebra on which the pelvic girdle is inserted, which serves as an insertion for the pelvic limb. The caudal region in the Urodelis is formed by several vertebrae, which in the Urodelas merge to form a single bone, called the urostyle.
In the Reptiles the neck region is even more specialized and therefore the number of vertebrae increases. In addition to the atlas another cervical vertebra appears, an epistrophe, which will articulate with the atlas which has a ring shape on which the anterior process of the axis, called the tooth of the axis, is inserted. This type of organization and specialization of the first two cervical vertebrae also determines a rotation of the skull on the vertebral column. This specialization of the first two cervical vertebrae is also present in mammals and birds. In addition to the two cervical vertebrae thus organized, they follow other cervical vertebrae, whose number is species-specific. The thoracic and lumbar region does not present major differences and in some species of Reptiles they present joints with the ribs.
The sacral region is formed by two vertebrae, while the caudal region has a variable number of vertebrae depending on the species. In all the Mammals, with the exception of the Mammals belonging to the Sdentati family (armadillos, anteaters, pangolins and sloths) and Sirenids (dugong), the cervical vertebrae are 7 in number. The thoracic region consists of vertebrae that articulate with the ribs , whose number varies from species to species, but which is always the same as that of the coasts itself. The lumbar and sacral region follows, the latter characterized by the fusion of the sacral vertebrae (at least three) to form a unique structure, the sacrum, on which the pelvic girdle arises. In the caudal region the number of vertebrae is variable and generally acts as a support for the tail. In birds the cervical region of the vertebral column reaches the maximum of the specialization determined by the particular articulation that is established between the cervical vertebrae that make the neck extremely flexible. Furthermore, the number of cervical vertebrae is variable and high depending on the species. The skeleton in this class is extremely specialized for adaptation to flight and bipedal posture.
The vertebrae of the thoracic region are joined together, sometimes no one is fused to form the notarium, and they articulate with the ribs. The sacral region consists of two sacral vertebrae that often merge with the lumbar vertebrae and part of those in the caudal region to form the sinsacro, which is articulated with the pelvic girdle. The vertebrae of the caudal region are free in the first tract, while they merge in the last tract to form the pyostyle, which gives the feathers to the tail. The ribs are flat, bony structures with cartilage in their distal portion, which articulate odorsally with the thoracic vertebrae and eventually, in the Tetrapods, with the sternum. All tetrapods are equipped with a sternum except for snakes (Reptiles, Ophids). They are missing in Cyclostome Fish (Agnati) and in Holocephaly (cartilaginous fish). Bony fish (Teleostei) have two pairs of ribs: dorsal and ventral. Many fish have only ventral coasts, while others such as sharks (cartilaginous fish) have only dorsal ones. The ribs of the Tetrapods correspond to the ventral ones of the Pisces and are equipped with facet joints for the thoracic vertebrae.
- Mestolone skeleton Mestolone skeleton
- Dog skeleton Dog skeleton
- Cat skeleton Cat skeleton
- Hare skeleton Hare skeleton
- Monkey skeleton Monkey skeleton
- Sitatunga skeleton Sitatunga skeleton