The genus Carcharocles may be invalid, and the shark may actually belong in the genus Otodus , making it Otodus megalodon .  A 1974 study on Paleogene sharks by Henri Cappetta erected the subgenus Megaselachus , classifying the shark as Otodus ( Megaselachus ) megalodon , along with O. (M.) chubutensis . A 2006 review of Chondrichthyes elevated Megaselachus to genus, and classified the sharks as Megaselachus megalodon and M. chubutensis .  The discovery of fossils assigned to the genus Megalolamna in 2016 led to a re-evaluation of Otodus , which concluded that it is paraphyletic , that is, it consists of a last common ancestor but it does not include all of its descendants. The inclusion of the Carcharocles sharks in Otodus would make it monophyletic , with the sister clade being Megalolamna .  There was one apparent description of the shark in 1881 classifying it as Selache manzonii . 
But what would it look like to extend some of the special status of adolescents to young people in their 20s? Our uncertainty about this question is reflected in our scattershot approach to markers of adulthood. People can vote at 18, but in some states they don’t age out of foster care until 21. They can join the military at 18, but they can’t drink until 21. They can drive at 16, but they can’t rent a car until 25 without some hefty surcharges. If they are full-time students, the Internal Revenue Service considers them dependents until 24; those without health insurance will soon be able to stay on their parents’ plans even if they’re not in school until age 26, or up to 30 in some states. Parents have no access to their child’s college records if the child is over 18, but parents’ income is taken into account when the child applies for financial aid up to age 24. We seem unable to agree when someone is old enough to take on adult responsibilities. But we’re pretty sure it’s not simply a matter of age.