Errivaspis
Encyclopedia
Errivaspis is an extinct genus of pteraspid heterostracan that lived in the Early Devonian period.
plate around the eye. A rostral plate formed a pointed ‘snout’, several small plates around the mouth, and a dorsal spine pointing backwards. The rest of the body was covered with small scales that look more like modern fish scales than the bony plates of early forms. The tail was fan-shaped.
consisted of head covered in dermal armor consisted of plates of dentine and aspidine, generally with a honeycomb-like structure, covering the branchiocephalic region and body with large scales covering the trunk and tail. The eyes were lateral, extremely small without sclerotic ring. Also the two movable paired fins were absent; anal fin absent; tail internally hypocercal, externally often symmetrical; perhaps two olfactory capsules (diplorhinal condition) with only an internal opening into the mouth area.
Species with interlocking tesserae in the dermal armor are known as the tessellated pteraspidiforms or heterostracans. Maximum length is 1.5 m, usually much smaller. Pteraspidiforms are well known from the Lower Silurian
to the Late Devonian. Taxa of uncertain affinities, of which some are not definitely known to be heterostracans.
Description
Errivaspis had large dorsal plates and ventral plates, the linking branchial plate, as well as a cornual plate at the side, an orbitalOrbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
plate around the eye. A rostral plate formed a pointed ‘snout’, several small plates around the mouth, and a dorsal spine pointing backwards. The rest of the body was covered with small scales that look more like modern fish scales than the bony plates of early forms. The tail was fan-shaped.
Characteristics
More analytically, Errivaspis had a pair of external lateral gill openings, emptying from several gill pouches. The exoskeletonExoskeleton
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...
consisted of head covered in dermal armor consisted of plates of dentine and aspidine, generally with a honeycomb-like structure, covering the branchiocephalic region and body with large scales covering the trunk and tail. The eyes were lateral, extremely small without sclerotic ring. Also the two movable paired fins were absent; anal fin absent; tail internally hypocercal, externally often symmetrical; perhaps two olfactory capsules (diplorhinal condition) with only an internal opening into the mouth area.
Species with interlocking tesserae in the dermal armor are known as the tessellated pteraspidiforms or heterostracans. Maximum length is 1.5 m, usually much smaller. Pteraspidiforms are well known from the Lower Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
to the Late Devonian. Taxa of uncertain affinities, of which some are not definitely known to be heterostracans.