Pituriaspis doylei was one of two known species of jawless fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 belonging to the Class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Pituriaspida

Pituriaspida

The Pituriaspida are a small group of extinct armored jawless fishes with tremendous nose-like rostrums, which lived in the marine, deltaic environments of Middle Devonian Australia...

, and is the better known of the two. The species lived in estuaries during the Middle Devonian

Devonian

The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

, in what is now the Georgina Basin

Georgina Basin

The Georgina Basin is a large intracratonic sedimentary basin in central and northern Australia, lying mostly within the Northern Territory and partly within Queensland. It is named after the Georgina River which drains part of the basin. Deposition of locally up to ca...

 of Western Queensland

Queensland

Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.

The first specimens of P. doylei were actually empty sandstone casts of the head shields, with none of the original bone remaining.

P. doylei vaguely resembled the Osteostraci

Osteostraci

The class Osteostraci was a group of bony-armored jawless fish, termed "ostracoderms", that lived in what is now North America, Europe and Russia from the Middle Silurian to Late Devonian....

, though neither are considered to be close relatives. The headshield extends posteriorly to form a long abdominal division which probably reached the anal region. The dorsal portion of its head armor differs from osteostracans in that the orbits of the eyes are set apart from each other, and that the shield has no pineal foramen (the "hole" between the eyes of Cephalaspis

Cephalaspis

Cephalaspis was a genus of armored goldfish-sized to trout-sized detritivorous fish that lived in freshwater streams and estuaries of early Devonian Western Europe...

and its relatives), and that an opening at the base of the rostrum gives very little hints about the nature of the nasal openings. The exoskeleton

Exoskeleton

An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...

 is ornamented with tiny rounded tubercle

Tubercle

A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....

s. A unique characteristic of the Pituriaspida is a peculiar pit, which may have held some sort of sensory organ in life, located ventrally to the orbits, known as the adorbital depression. Almost nothing is known of the rest of the body, save that it had a pair of well-developed pectoral fins, similar to gnathostome fish.