A satellite-tagged great white shark called Lydia is about to make history as the first of its species to be seen crossing from one side of the Atlantic to the other. Lydia was first tagged off Florida as part of the Ocearch scientific project. She is currently swimming above the mid-Atlantic ridge in the center of the Atlantic…
Fire in the Sea, published by Texas A&M University Press
This shark species, shown at right with a squid in its jaws, is rarely found outside of the benthic zone. “Neither squid nor shark desired outside help and interference,” Compton wrote in his narrative.
A close relative of Stethacanthus, which lived a few million years earlier, the tiny prehistoric shark Falcatus is known from numerous fossil remains from Missouri, dating from the Carboniferous period. Besides its small size, this early shark was distinguished by its large eyes (the better for hunting prey deep underwater) and symmetrical tail, which hints that it was an accomplished swimmer. Also, the abundant fossil evidence has revealed striking evidence of sexual dimorphism—Falcatus males had narrow, sickle-shaped spines jutting out of the tops of their heads, which presumably attracted females for mating purposes.
In North America, the Great White Shark is primarily found off the coasts of California and the northeast, but they live throughout temperate and tropical oceans and can occur along the length of both coasts. While they can reach 21 ft (6.5 m) long, they actually average a more modest 13-17 ft (4-5 m) when mature.
Great Whites are relatively intelligent and can be fairly social. In South Africa where most Great White research is done, they have been shown to organize into clans like wolf packs, where each individual has a clear rank under an alpha leader. They are typically not violent in their social interactions with other Great Whites - they rely on rituals and displays to establish dominance. Interestingly, females are dominant over males in such situations.
They are ambush predators whose diet is composed of large vertebrates such as seals, dolphins or big fish like tuna. Most prey is taken by surprise from behind or below, typically in the early morning hours when visibility is poorer. Great Whites generally focus on species with higher fat content - humans are too bony to be considered appealing, but since swimmers or surfers can resemble some of their preferred prey (seals) attacks occasionally happen.
Brochoadmones came from the Early Devonian of Canada, about 435-430 million years ago. Around 10cm long (4in), it was a type of “spiny shark" — an extinct group that shared features with both bony and cartilaginous fish.
And it had a lot of extra fins. Six paired “finlets” running from below the gills to the pelvic fins, each consisting of a spine with a web of scaled skin. They look very much like what would be expected for multiple fins evolving from a lateral fin-fold (essentially a single elongated fin subdividing).
February on this blog is going to be Daily Paleo Art Month! Because doing dinosaurs all last July was so much fun I want to do this thing again. Every weekday for the rest of the month I’ll be posting a new image of something strange, obscure, or just plain interesting from the fossil record — only this time we’re staying firmly outside of the Avemetatarsalia (pterosaurs and dinosaurs/birds) to give some less famous critters the spotlight.
A cartilaginous fish from off the southwest coast of the ancient supercontinent Gondwana (and later Pangaea), Helicoprion first appeared in the late Carboniferous (310 million years ago) and survived up until just past the massive Permian-Triassic extinction (250mya). Despite looking rather shark-like and possibly reaching sizes of around 6m (20ft) long, it was actually closer related to the chimaeras.
For a long time, the only parts of this animal known were bizarre buzzsaw-like spiral whorls of teeth, since cartilage skeletons very rarely fossilize. The ideas for just where in the body this structure was positioned were ridiculously varied.
The most recent reconstruction is based on CT scans of a well-preserved fossil with jaw and skull elements, which showed the whorl taking up the whole lower jaw. It also turns out Helicoprion had no upper teeth at all. It’s thought to have used this arrangement to shred and crush up squid and other soft-bodied marine prey, but there’s still very little known about how such a unique type of teeth evolved in the first place.
Large, well-established and isolated Marine Protected Areas boost shark numbers
The concept itself probably doesn’t come as a big surprise to a lot of us, but a recent comprehensive study has shown that large, established and well-enforced no take zones show 14 times more more sharks and other sea life than commercial fishing areas.
87 marine protected areas (MPAs) were examined over 40 countries, allowing researchers to determine factors contributing to a successful MPA. Successful MPAs typically had five features: no-take zone, well-enforced, over 10 years old, over 100km-sq, and isolated by sand or deep water.
Of course, most of us also know that the majority of MPAs are not successful, and are in fact only token protected areas - they’re paper parks, meaning they’re only MPAs on paper. And the sea life in these areas is about on the same level as the sea life in the nearby fishing areas. Which is to say, not great; the study shows a 90% decrease in sharks, and 83% decrease in large fish (with a 63% decrease in fish overall). And that’s pretty scary, because it means a lot of MPAs aren’t achieving their conservation goals, if they have them at all.
But it’s not all bad news. Hopefully, this means the study and ones similar to it could be used in the near future to improve current MPAs, increase the number of successful MPAs and reduce the number of paper parks and MPAs like them. Fingers crossed.
(Also, you can read the paper, published in Nature, here.)
Salmon sharks, Lamna ditropis (Hubbs and Follett, 1947), are closely related to porbeagle sharks, Lamna nasus. Salmon sharks measure up to 3.7 m in length and weigh a maximum of 454 kg. They have heavy spindle-shaped bodies with short, blunt, conical snouts and large gill slits relative to their body size. Their first dorsal fin is dark in color. Their dorsal (upper) sides and flanks are dark blue to gray or black in color. Their ventral (under) sides are white with darker blotches or spots.
Salmon sharks have been observed both singly and in schools, usually feeding. This species is a very fast swimmer.
In the eastern North Pacific, female salmon sharks live up to 20 years, males to at least 27 years.
In the western North Pacific, males mature at about 1.77-1.86 m in total length and 5 years of age, and females mature at about 2.00-2.23 m when they are 8-10 years old…
Like other sharks in Lamnidae family, salmon sharks are endothermic, meaning they are able to thermoregulate, or maintain a body temperature above the temperature of the surrounding water. Most other marine life is ectothermic, which means they maintain an internal temperature that matches the surrounding water. Fast swimmers, like sharks and tuna, are more commonly endothermic…
A prehistoric shark species is the earliest animal known to migrate, over 300 million years ago. The sharks lived in rivers but swam down to the sea to breed and care for their young.
Bandringa were primitive sharks that lived about 310 million years ago. They did not look much like typical modern sharks, having long spoon-shaped snouts.
Until recently scientists thought there had been two species of Bandringa, one that lived in fresh water and one that lived in the sea. But according to Lauren Sallan of the University of Michigan in Ann Arbor, there was only one species. The sharks migrated from their freshwater habitat to a saltwater nursery to reproduce.
Sallan and her team examined Bandringa remains from three sites in the Mazon Creek deposit in Illinois, including egg casings, bones, and soft tissue from juveniles and hatchlings. One site was originally on the coast but the others were inland. They found no evidence that fossils from the different sites belonged to different species…
(read more: New Scientist)
illustration byJohn Megahan, University of Michigan
Great white sharks are longer in the tooth than we thought. Traditionally, researchers age a great white (Carcharodon carcharias) by tallying the alternating light and dark bands that form on the animal’s vertebrae as it grows, similar to rings on a tree. Using this method, experts believed the species had a life expectancy of about 30 years.