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A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə).All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa.
Initially, Deuterostomia included the phyla Brachiopoda, [6] Bryozoa, [7] Chaetognatha, [8] and Phoronida [6] based on morphological and embryological characteristics. However, Deuterostomia was redefined in 1995 based on DNA molecular sequence analyses, leading to the removal of the lophophorates which was later combined with other protostome animals to form the superphylum Lophotrochozoa. [9]
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 ]
Spotted gar, Lepisosteus oculatus This article contains a list of all of the classes and orders that are located in the phylum Chordata.. The subphyla Tunicata and Vertebrata are in the unranked Olfactores clade, while the subphylum Cephalochordata is not.
The dorsal nerve cord is an anatomical feature found in chordate animals, mainly in the subphyla Vertebrata and Cephalochordata, as well as in some hemichordates.It is one of the five embryonic features unique to all chordates, the other four being a notochord, a post-anal tail, an endostyle, and pharyngeal slits.
The body segments are anatomically blocks of skeletal muscles, called the myomeres, which are found in vertebrates only. No eyes can be observed. [24] The muscle orientation and flat shaped body indicate that Pikaia was an active and free swimmer. [8] It would have swum by throwing its body into a series of S-shaped, zigzag curves, as do living ...
The liver is a large and oily organ that comprises 25% of the total body weight of the shark. [11] The two purposes of this organ in the shark are to store energy and oil. The liver is a hydrostatic organ. This organ helps with buoyancy since the liver stores oils, decreasing the density of the shark's body. [11]
In other words, the cyclostome characteristics (e.g. horny teeth on a "tongue", gill pouches) are either instances of convergent evolution for feeding and gill ventilation in animals with an eel-like body shape, or represent primitive craniate characteristics subsequently lost or modified in gnathostomes.