2003), disarticulated cephalaspids, placoderms and acanthodians
, and both articulated and disarticulated eurypterids (Miller 2007a).
This result explains some of the longstanding confusion about the placement of acanthodians
in vertebrate history.
These substages correspond to the acanthodian
zones established by Valiukevicius .
, and shield fragments of heterostracan(s) (ibid.
Analysis revealed that the acanthodians
appeared in regurgitated material more often than the paleoniscoids, but the reverse was true for the coprolites.
However, these scales are evidence of the presence of small acanthodians
in the vertebrate community.
Don and Eldon collected skull roofs of haplolepidid fishes and a fin-spine of a small acanthodian
fish (Gyracanthus) that Don later described in detail (Baird 1962a, 1978a).
The ischnacanthid acanthodians
lived during the Early Devonian period, which lasted from 416 to 397 million years ago.
Valiukevicius mentioned that acanthodians
are very poorly represented in the terrigenous deposits of the Parnu RS.
These previously discovered eurypterids are from the western exposure of the Campbellton Formation and are believed to have inhabited a coastal deltaic setting, along with a rich vertebrate assemblage that included cephalaspids, placoderms, acanthodians
, and sharks.
Before this discovery, most scientists believed that the braincases of Acanthodians
resembled those of bony fish, and were thus related to this type of animal.
2011; Ivanov & Marss 2014) and acanthodians
(Valiukevicius 1998; Marss et al.