On the basis of a completely different shape of the scales, which is somewhat similar to heterostracan
ribs, and the ultrasculpture pattern of the crown resembling both the furcacaudid and pteraspidid heterostracan
ultrasculpture, the family Longodidae was established in an unknown (unnamed) order in the subclass Thelodonti.
It occurs together with the thelodont Phlebolepis elegans Pander, a heterostracan
Archegonaspis sp., birkeniid anaspids, acanthodians Nostolepis striata Pander, Gomphonchus sandelensis (Pander), and Gomphonchus hoppei (Gross), and a taxon that has similarities with Thelodus parvidens Agassiz.
A similar model of skeletal development is also seen in a heterostracan
Lepidaspis serrata Dineley & Loeffler, 1976: it possesses dentine ridges on the aspidin ridges, filled with aspidin trabeculae (Keating et al.
Pander in 1856, who described shields of the heterostracan
Tolypelepis undulata, plates of the osteichthyan Lophosteus superbus and a number of jaw bones of acanthodians (Pander 1856).
Archegonaspis sp.; osteostracan Osteostraci gen.
A complete, articulated heterostracan
from Wenlockian (Silurian) beds of the Delorme Group, Mackenzie Mountains, Northwest Territories, Canada.
Agnathan zones include mainly these of the psammosteid heterostracans
. In the incomplete Lower Devonian sequence the Phialaspis (previous Traquairaspis) heterostracan
Zone and the Skamolepis fragilis thelodont Zone have been recognized.
Using modern techniques, Tiiu Marss (Tallinn) and Valentina Karatajute-Talimaa (Vilnius) redescribe the late Silurian.early Devonian tessellated heterostracan
Oniscolepis Pander, 1856 from the East Baltic and North Timan.
The orthodentine of tubercles and ridges resembles the dentine in the crown of katoporid thelodonts, and some other heterostracan
In the coarse-grained (diameter 0.5-2 mm) detrital material, heterostracan
, placoderm, and sarcopterygian plate fragments are fairly worn.
(Pteraspidomorpha) predominate in number among species-level taxa, but the specimens of antiarch placoderm remains are most numerous.
The first record was of fin spines and heterostracans
from Pennsylvania by Claypole (1884, 1885); he assigned the fin spines ("small spines apparently of Selachian fish": Claypole 1885, p.