Description
Isurus hastalis;
Isurus (meaning “equal tail”) is a genus of mackerel sharks in the family Lamnidae, commonly known as the mako sharks. They are largely pelagic, fast predatory fish capable of swimming at speeds up to 50 km/h (31 mph).
Hastalis teeth can grow up to 3.5 inches in length, suggesting a very large shark. Its body was probably very similar to that of modern great whites. It is also believed to have a cosmopolitan distribution, with C. hastalis teeth being found worldwide.[13] The species is divided into two forms based on tooth morphology, each with a unique evolutionary line. The maximum adult length is estimated between 5 and 7 m (16 and 23 ft).[14][15] Smaller individuals were about 2.6–4.5 metres (8.5–14.8 ft) long
Fossil History and Evolution
Although fossil teeth of Isurus have been reported from as early as the Late Cretaceous, they are likely to be of a shark with a similar dentition, Cretoxyrhina; since at one point they were considered to be the same (now defunct) genus Oxyrhina, and modern referrals to Isurus in the Cretaceous are scant. The earliest appearance of Isurus proper seems to be during the Oligocene with Isurus desori.
There has been much debate and speculation about the evolutionary origin and relationships between Isurus and its closest relatives, including the extant great white shark (Carcharodon carcharias). Molecular clock analyses place the last common ancestor of Isurus and Carcharodon between 43-60 million years ago during the Late Paleocene-Early Eocene.[10] This insight should guide efforts to better resolve the fossil ancestry of both lineages, by providing a window of time in which to search for ancestor candidates.
Description
The two living species are the shortfin mako shark (I. oxyrinchus) and the longfin mako shark (I. paucus). They range in length from 2.5 to 4.5 m (8.2 to 14.8 ft)[citation needed], and have an approximate maximum weight of 680 kg (1,500 lb)[citation needed]. They both have a distinctive blue-gray color scheme common among mackerel sharks.
