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Idealised vertebrate body plan, showing key characteristics [6] Vertebrates (and other chordates) belong to the Bilateria , a group of animals with mirror symmetrical bodies. [ 7 ] They move, typically by swimming, using muscles along the back, supported by a strong but flexible skeletal structure, the spine or vertebral column . [ 6 ]
The lampreys are a very ancient lineage of vertebrates, though their exact relationship to hagfishes and jawed vertebrates is still a matter of dispute. [7] Molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, [8] and so also are vertebrates in a monophyletic sense. Others consider them a sister group ...
Each vertebra (pl.: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal segment and the particular species.
A majority of paleontologists use the term "tetrapod" to refer to all vertebrates with four limbs and distinct digits (fingers and toes), as well as legless vertebrates with limbed ancestors. [ 15 ] [ 16 ] Limbs and digits are major apomorphies (newly evolved traits) which define tetrapods, though they are far from the only skeletal or ...
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
Osteichthyes (/ ˌ ɒ s t iː ˈ ɪ k θ iː z / ost-ee-IK-theez), [2] also known as osteichthyans or commonly referred to as the bony fish, is a diverse superclass of vertebrate animals that have endoskeletons primarily composed of bone tissue.
The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than fish, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always ...
Limbs in vertebrates are occasionally organized into stylopod (relating to the humerus and femur), zeugopod (relating to the radius and tibia, along with associated structures) and autopod (relating to digits) categories, although anatomically, the evolutionary differences between these groups in early tetrapods tends to be vague. [2] [20]