Zenaspidida is an extinct order of osteostracans, a group of jawless stem-gnathostomes. They possessed a distinct headshield, which varied in width to length ratio by species.
Zenaspidida is an extinct order of osteostracans, a group of jawless stem-gnathostomes. They possessed a distinct headshield, which varied in width to length ratio by species. (en)
Zenaspidida is an extinct order of osteostracans, a group of jawless stem-gnathostomes. They possessed a distinct headshield, which varied in width to length ratio by species. (en)