osteostraci मीनिंग इन हिंदी

"P . doylei " vaguely resembled the Osteostraci, though neither are considered to be close relatives.
*" A New Osteostracan Fauna from the Devonian of the Welsh Borderlands and Observations on the Taxonomy and Growth of Osteostraci"
According to Philippe Janvier, anatomical similarities of " B . stensioi "'s brain and braincase with those of jawless fish, such as the Osteostraci and the Galeaspida, strongly suggest that " B . stensioi " is a basal placoderm closest to the ancestral placoderm.
The better studied species-" Pituriaspis doylei ", which had a superficial resemblance to the Osteostraci, had an elongate headshield, that, coupled with its spear-like rostrum, gave it a throwing-dart-like appearance . " Neeyambaspis enigmatica " had a much smaller and shorter rostrum, and a more triangular headshield, making it look as though it were a guitar pick with a tail.
It is characterised by a number of features of its armoured headshield, including the presence of raised rims around its eyes, the shape of its lateral and median fields ( depressed areas of the headshield covered by small loose plates, which are common to most Osteostraci ), its prominent dorsal spine, fairly long cornual processes ( backwards pointing spines on each side of the headshield ) and ornamentation . " Janaspis " was fairly small compared with other osteostracans, with a headshield measuring less than 60mm.