Ateleopoda

Ateleopoda is a subphylum of marine animals within the phylum Chordata. It is characterized by the absence of a notochord in the adult stage, which is a defining feature of the subphylum. The term "Ateleopoda" is derived from the Greek words "ateleos," meaning "incomplete," and "podos," meaning "foot," reflecting the lack of a notochord in these animals. This subphylum includes several classes of marine invertebrates, such as the Tunicata (sea squirts and salps), Cephalochordata (lancelets), and Vertebrata (vertebrates).

The Ateleopoda subphylum is further divided into two main groups: the Tunicata and the Cephalochordata. The Tunicata are sessile or planktonic filter feeders that secrete a tunic, a protective outer layer, which is a characteristic feature of this group. The Cephalochordata, on the other hand, are small, free-swimming animals that possess a notochord in their larval stage but lose it in the adult stage. The Vertebrata, which includes all jawed and jawless vertebrates, are also part of the Ateleopoda subphylum.

The Ateleopoda subphylum is an important group in evolutionary biology, as it provides insights into the early evolution of chordates. The lack of a notochord in the adult stage is a unique feature that sets this subphylum apart from other chordates. Despite this, the Ateleopoda share many common features with other chordates, such as a dorsal hollow nerve cord and pharyngeal slits, which are thought to be homologous structures.

In summary, the Ateleopoda subphylum is a diverse group of marine animals characterized by the absence of a notochord in the adult stage. It includes several classes of marine invertebrates and provides valuable insights into the early evolution of chordates. The subphylum is further divided into two main groups: the Tunicata and the Cephalochordata, each with its unique features and adaptations.