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By invertebrates are meant the non-vertebrate creatures of the kingdom Animalia (or Metazoa) in the biotic domain of Eukaryota. By phyletic definition, these many-celled, sub-vertebrate animals lack a vertebral column, spinal column, vertebrae, backbone, or long, full-length notochord—in contrast to the vertebrates in the one phylum of Chordata.
The trait that is common to all invertebrates is the absence of a vertebral column (backbone): this creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only; it is not based on any clear biologically homologous trait, any more than the common trait of having wings functionally unites insects, bats ...
Paleontologists at work at the dinosaur site of Lo Hueco (Cuenca, Spain). Vertebrate paleontology is the subfield of paleontology that seeks to discover, through the study of fossilized remains, the behavior, reproduction and appearance of extinct vertebrates (animals with vertebrae and their descendants).
It is traditionally considered as transitional fossil between invertebrates and vertebrates, [3] and considered as stem-group chordate in 2012. [4] [5] It was a primitive creature with no evidence of eyes, without a well defined head, and less than 2 inches (5 centimetres) long.
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]
Vertebrates (/ ˈ v ɜːr t ə b r ɪ t s,-ˌ b r eɪ t s /) [3] are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest ...
The vertebrates share one body plan, while invertebrates have many. This term, usually applied to animals, envisages a "blueprint" encompassing aspects such as symmetry, layers, segmentation, nerve, limb, and gut disposition. Evolutionary developmental biology seeks to explain the origins of diverse body plans.
Invertebrates are a vast and very diverse group of animals that includes sponges, echinoderms, tunicates, numerous different phyla of worms, molluscs, arthropods and many additional phyla. Single-celled organisms or protists are usually not included within the same group as invertebrates.