#elasmobranchii

Pink whipray Pateobatis fai

Lives in the Indian and Pacific Oceans from Africa to Polynesia. Generally inhabits shallow water under 70 m (230 ft) deep, in sandy areas associated with coral reefs. When resting, up to ten individuals may pile atop one another, sometimes mixing with other species. On Ningaloo Reef, it has been seen "riding" on larger species of rays.

Sharks evolved around 450 million years ago, which means they’ve hitched a lift on planet Earth around the galaxy twice. If that’s not yet given you a fact-induced headache, it may tip you over to hear that it also means sharks were on Earth before trees, at a time when Saturn didn’t have rings yet. Part of their success comes down to their flexibility when it comes to environmental conditions, able to survive in a wide range of oceans and at different depths. "I think it is safe to say that it is partly because sharks are able to exploit different parts of the water column - from deep, dark oceans to shallow seas, and even river systems," Emma Bernard, a curator of fossil fish at the Natural History Museum said in a piece for the museum. "They eat a wide variety of food, such as plankton, fish, crabs, seals and whales. This diversity means that sharks as a group are more likely to survive if things in the oceans change." One of the longest-living sharks, the Greenland shark, certainly looks prehistoric. We actually only found out that they were capable of living to around 400 years old thanks to the atomic bomb, but the earliest sleeper sharks didn’t emerge until around 100 million years ago, by which time this group of fish had already been splashing around on Earth for well over a galactic year.

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Scanning the seafloor like a metal detector, the bull shark’s electrosensory organs are strong enough to pick up signatures measured in microvolts, even under the sand. She’s on the hunt. Suddenly, a jolt draws her attention—an injured fish, writhing in the shallows. She swoops in for the kill. It’s a trap. A steel hook punctures her thick cheek, jerking with incredible force. It’s pulling her toward the surface. She tries to fight back, but the hook digs further. She thrashes as her fins emerge in the open air. Then come the gunshots: four in a row, point-blank. She’s gone. Scenes like this are commonplace in the United States, which oversees one of the world’s largest recreational shark fishing industries. According to annual reports, the country typically kills more sharks for sport than for commerce. Controversially, regulators at the National Oceanic and Atmospheric Administration’s Fisheries division (NOAA Fisheries) formally license anglers to target species classified as threatened and endangered by the United Nations—a “red list” that now encompasses more than a third of all sharks and rays. Despite deep concern among ecologists and overwhelming public opposition, NOAA regulatory mechanisms remain captured by the fishing industry, and, in fact, the agency is considering proposals to strip shark protections even further. Meanwhile, journalists and investigators on the docks report widespread patterns of poaching and other crimes against wildlife at NOAA-sanctioned shark-killing contests.

“This shark is supposed to be a longfin mako (original photos by Rodrigo Friscione) but it looks nothing like it, maybe a new undescribed species of Isurus? Made this rough infographic to explain my point.” - Ichthyosore on Reddit

I will update this as the conversation develops. Very interesting stuff, here!

“Fascinating! Very perceptive. Are there images of different, individual Isurus spp., or is it just one individual? Is there a picture that shows the pectoral fins unobstructed?

Okay, after looking at it for a while and consulting this paper, I think this Isurus sp. is  Isurus paucus. The pectoral fins are quite long, and the rostrum is shorter that I. oxyrhincus. I think the camera angle obscures the upward curve of the bottom face of the rostrum that can be seen on I. paucus.

If this is a single Isurus sp., then individual variation maybe responsible for some of the quirks I'm seeing around the orbital. It may also be genetic variation of a different population of I. paucus. Hard to know without more research and location data on the reference images.Just some suggestions.

 My expertise lies with Hexanchidae. In the paper that redescribed Hexanchus vitulus, DNA testing ultimately determined the existence of a new species of Hexanchus sp. separate from the species H. vitulus was mistaken for: H. nakamurai.

In short, Isurus sp. may be a new species, but DNA testing is necessary to compare to both I. oxyrhincus and I. paucus.