What is the most basal class of living vertebrates?

What is the most basal class of living vertebrates?

While they have some important features of true vertebrates (e.g., a head with paired sensory organs such as eyes), they lack evidence of having a skull, which is a synapomorphy of crown group vertebrates (hagfish and lampreys, which are the most basal living vertebrates, have cartilaginous skulls; see next page).

What is the most basal chordate?

Lancelets
Phylogeny. The deep branching of chordate phylogeny has been clarified by chordate genomics. Chordate genomics demonstrates that the Lancelets are the most basal living clade within the chordates, while the Tunicates are the sister clade to the Craniata.

What are the most primitive living vertebrates?

Agnatha. Lampreys and hagfishes are the only jawless vertebrates to survive today. They both have a round mouth and for this reason are often referred to as cyclostomes. They are the most primitive of the vertebrates.

What are basal vertebrates?

A “basal” vertebrate means a vertebrate at the base of the vertebrate family tree, either one of the vertebrates from which all others evolved or a close cousin of the same. Some basal vertebrates are stem group vertebrates, meaning they are older than the earliest common ancestor of all living vertebrate species.

What is the endostyle of a basal chordate?

Endostyle: A mucus-covered structure in the pharyx that is used for filter feeding in basal chordates and develops into the thyroid gland in derived chordates. Pharyngeal slits: Openings into the pharynx (throat region) that are associated with filter feeding in basal chordates and respiration in fishes (in conjunction with gills).

What are the major subgroups of the Chordata?

So are most of the animals featured on nature programs on television. Major subgroups of chordates include “fishes” (a paraphyletic grouping; see below), amphibians (frogs, toads, and salmanders), “reptiles” (another paraphyletic group), birds, and mammals.

Is the cephalochordate a vertebrate or a chordate?

It has been interpreted as a cephalochordate, a stem chordate, a stem vertebrate, a vertebrate (see Sansom et al., 2010 and references therein), as well as possibly not part of the chordate clade at all.