Microbrachius dicki (Traquair 1888, Long et al 2014; Early Devonian, 385 mya, 2-4cm armored shield) is a tiny antiarch placoderm with small armored pectoral fins. Several specimens are known with distinct male and female fixed plate genitals for side-by-side mating.
Bothriolepis canadensis (Eichwald 1840; Late Devonian; typically 30cm, up to 100cm in length) is a jawless placoderm with a tall skull and armored pectoral fins. The postfrontal makes up most of the cheek region. The intertemporal, supratemporal and tabular are vertical.
At left a ventral view of the oral cavity of Bothriolepis (left) compare to the pre-gnathostome, Rhinpteraspis, which has a mobile set of mandible scales. By contrast, in Bothriolepis the mandible is immobile. The hinged mobile nasals rimmed by premaxillae move to scrape and sweep microbial mat, coral or sand into the mouth. Note the same shapes in the mandible elements in the two taxa. |
