Lamnidae
The Lamniformes, derived from the Greek lamna meaning "fish of prey," form an order of sharks that are commonly referred to as mackerel sharks. This term may also specifically indicate the family Lamnidae. Within this order, one can find well-known shark species such as the great white, as well as more unique representatives like the goblin shark and megamouth shark.
Distinguishing features of Lamniformes members include two dorsal fins, an anal fin, five gill slits, eyes without nictitating membranes, and a mouth that extends beyond the eyes. Species belonging to the Lamnidae and Alopiidae families are remarkable for their ability to maintain a higher body temperature than the surrounding waters.
The group consists of medium to large-sized macropredators, including the largest macropredatory shark that ever existed, the extinct Otodus megalodon, as well as large planktivores.
An ancient shark resembling the carpet shark, called Palaeocarcharias, which measured approximately 1 meter (3.3 feet) in length, shares the unique tooth histology observed in most lamniform sharks. These sharks lack orthodentine and are thus considered the oldest known lamniform, or a closely related sister group. During the Cretaceous period, Lamniformes underwent a significant adaptive radiation and became prominent figures in oceanic ecosystems. Although they reached their highest diversity during the Late Cretaceous, their population severely declined during the K-Pg extinction event. However, they later experienced a resurgence and achieved a peak in diversity during the Paleogene epoch. Over the course of the last 20 million years, Lamniformes have experienced a sharp decline, with only 15 species currently in existence. This is in contrast to the more than 290 extant species found in the Carcharhiniformes, which also evolved into medium and large body sizes during this time period. The exact reasons for this decline are uncertain but likely involved both biotic factors such as competition and non-biotic factors such as temperature and sea level fluctuations.
