Arandaspis

Arandaspis is an extinct genus of jawless fish known from Ordovician rocks in Australia. Its heavily armoured head and trunk plates make it one of the earliest well-known vertebrates.

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Jawless fish: Jawless fish are vertebrates that lack hinged jaws, including living lampreys and hagfish and many extinct groups. Arandaspis belongs to this broad early vertebrate grade.
Cephalothoracic shield: A cephalothoracic shield is an external armour covering the head and forward trunk of an animal. Arandaspis had a broad shield made from paired and median plates.
Georgina Basin: The Georgina Basin is a large sedimentary basin spanning parts of central and northern Australia. Fossils attributed to Arandaspis were recovered from Ordovician rocks of this basin.
Sacabambaspis: Sacabambaspis is an extinct genus of Ordovician jawless fish known from South America. It is a close, similarly armoured comparison from another Gondwanan region.
Ostracoderm: Ostracoderms are extinct, armoured jawless fishes known chiefly from Paleozoic rocks. Arandaspis is commonly grouped among these armoured early fishes.
Sensory canal: A sensory canal is a channel in the skin or skeleton that houses receptors for detecting movement or pressure. Canals in Arandaspis's armour record sensory systems along its body.
Alice Springs: Alice Springs is a town in Australia's Northern Territory near the continent's geographic centre. The region's fossil localities helped establish the Australian setting of Arandaspis.
Astraspis: Astraspis is an extinct genus of Ordovician jawless fish known from North America. Its armour and sensory structures provide a comparison with Arandaspis.
Vertebrate: Vertebrates are animals with a backbone or a related internal axial skeleton. Arandaspis preserves evidence of an early vertebrate body plan.
Lateral line: The lateral line is a sensory system that detects water movement and pressure in aquatic vertebrates. Its fossil canal pattern is associated with this system in early fishes.