Morphological structure of head and comparison between agraulos longicephalus hicks, 1872 and a. ceticephalus barrande, 1846, from the drumian of spain and czech republic

Order Ptychopariida has always been a problematic group concerning the taxonomic classification of Cambrian trilobites, and even though the temporality of this group is well known, the relation between this order with others, and, the difficulty for classifying ptychopariids have let to diverse prob...