Vertebrates 1

Anatolepis

Bone-like scrap from the Cambrian of Queensland Australia

The Burgess Shale

Preservation of soft tissues, revealing anatomical structures and soft bodies taxa that would ordinarily be excluded from fossil record

Conodonts

Possessed mineralised skeletal elements in mouth and pharynx

Derived characters of chordates

Notochord, dorsal, pharyngeal and muscular

Notochord

Provides skeletal support. In most living vertebrates, this is a complex, joined structure, and adults only retain remnants of the embryonic notochord.

Dorsal - hollow nerve cord

Develops into the central nervous system: the brain and spinal cord.

Pharyngeal slits or clefts

In most taxa, grooves in the pharynx develop that open to the outside of the body.

Post-anal tail

A muscular tail that extends posterior to the anus, although in many species this is greatly reduced during development.

Cephalochordata (lancelets)

Named for bladelike shapes - live burrowed into sediment in shallow water environments

Urochrordata (tunicates)

Resemble chordates during their larval stage

Hox genes

same genes that organise the regionalisation of the vertebrate brain are expressed in lancelets simple nerve cord tip

Derived characteristics of vertebrates

Vertebrate enclosing spinal cord, an elaborate skull, lateral line system in aquatic forms, a closed circulatory system

Cyclostomata - Agnathans

Jawless vertebrates - Hagfishes and lampreys

Gnathostomata

Hinged skeletal structure at the anterior opening of the gut tube

Other characteristics

Genome duplications, enlarged forebrain and aquatic

Gnathostomata clades

1. Osteichthyes 2. Chrondrichthyes