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Há 5 dias · Ascidians (Phylum: Chordata, Class: Ascidiacea), or sea squirts, are the largest and most diverse class of the sub-phylum Tunicata (also known as Urochordata). They comprise approximately 3000 described species found in all marine habitats from shallow water to the deep sea.
19 de jun. de 2024 · Chordate, any member of the phylum Chordata, which includes the vertebrates, the most highly evolved animals, as well as two other subphyla—the tunicates and cephalochordates. Some classifications also include the phylum Hemichordata with the chordates.
19 de jun. de 2024 · There is disagreement over whether older animals—such as Yunnanozoon lividum and Haikouella (both of which date to 530 million years ago and possess several chordate features)—should be considered chordates. An extensive vertebrate fossil record begins about 400 million years ago.
13 de jun. de 2024 · Hemichordates have been pivotal for understanding when chordate-like morphological and developmental features evolved. Recent results (Cannon et al. 2009) indicate that colonial pterobranchs evolved from a solitary acorn worm-like hemichordate ancestor and are sister group to the Harrimaniid enteropenusts, although phylogenomic ...
16 de jun. de 2024 · The vertebrates are the only chordate group with neural cephalization, and their neural functions are centralized towards a series of vesicular enlargements in the head, which give rise to a brain.
11 de jun. de 2024 · Here we reinterpret the morphology of Pikaia, providing evidence for a gut canal and, crucially, a dorsal nerve cord—a robust chordate synapomorphy. The identification of these structures underpins a new anatomical model of Pikaia that shows that this fossil was previously interpreted upside down.
19 de jun. de 2024 · The chordate notochord is a stiff rod with a turgid core and fibrous sheath. It keeps the animal from shortening when locomotory waves are produced through muscular contraction. The chordate body is supported by fluid in the body cavities. In tunicates, added support is provided by the tunic.
