鱘魚體(ti)延長，一般呈(cheng)梭(suo)形(xing)。軀干(gan)部的橫(heng)斷面(mian)呈(cheng)近(jin)五角(jiao)形(xing)。吻(wen)長，體(ti)被5行骨(gu)(gu)(gu)板，或(huo)有(you)(you)時裸露。無眶(kuang)間(jian)隔、前鰓蓋骨(gu)(gu)(gu)和間(jian)鰓蓋骨(gu)(gu)(gu)。頭上(shang)(shang)骨(gu)(gu)(gu)板或(huo)有(you)(you)或(huo)無。尾鰭上(shang)(shang)緣有(you)(you)1行棘狀鱗(lin)。鰭條不骨(gu)(gu)(gu)化。背鰭和臀鰭后(hou)位。胸鰭低(di)位。腹鰭在背鰭前方。尾鰭歪形(xing)，或(huo)呈(cheng)鞭狀，上(shang)(shang)葉長于下葉。內頭顱為軟骨(gu)(gu)(gu)，僅(jin)部分(fen)骨(gu)(gu)(gu)化。左右腭方骨(gu)(gu)(gu)與(yu)篩骨(gu)(gu)(gu)區或(huo)蝶骨(gu)(gu)(gu)區不相(xiang)連(lian)，與(yu)頜(he)骨(gu)(gu)(gu)固連(lian)。有(you)(you)鎖骨(gu)(gu)(gu)，無椎體(ti)。鰾大，鏢管和食(shi)道(dao)背面(mian)相(xiang)連(lian)。食(shi)道(dao)短。胃部膨(peng)大，有(you)(you)幽門囊。腸(chang)短，有(you)(you)發達的螺旋瓣。