Twineye Skate Raja miraletus
Found in the Mediterranean and Atlantic coast of Africa. Raja are bottom-dwellers that are active during both day and night, and typically feed on molluscs, crustaceans and fish.
image by danijel1
seen from China
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seen from Malaysia
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Twineye Skate Raja miraletus
Found in the Mediterranean and Atlantic coast of Africa. Raja are bottom-dwellers that are active during both day and night, and typically feed on molluscs, crustaceans and fish.
image by danijel1
Strange Symmetries #15: Serrated Saw-Snoots
Long flattened snouts lined with pointy tooth-like denticles have convergently evolved at least three separate times in cartilaginous fish: in modern sawsharks and sawfish, and in the extinct sawskates.
This repeated "pristification" suggests that saws are just incredibly useful and relatively "easy to evolve" structures for these types of fish, being both highly sensitive to bioelectric fields and able to physically slash and stab to kill prey.
Onchopristis numida was a sawskate known from what is now Northern and Western Africa during the mid-Cretaceous, about 95 million years ago. Up to about 3m long (~10'), it lived in both saltwater and freshwater, and was probably a bottom-dwelling ambush predator similar to modern angelsharks.
Whenever a denticle was lost from its saw, a larger one would grow to replace it, and over the life of an Onchopristis this resulted in an increasingly extreme amount of saw asymmetry.
Modern pristified fish also have rather asymmetrical saws. Sawfish are commonly born with a different number of denticles on each side, while sawsharks add extra denticles of varying sizes as they age, with the ongoing replacement of lost denticles resulting in more uneven arrangements over their course of their lives.
It's not clear if the asymmetry gives any sort of advantage to these fish – but if nothing else it probably doesn't cause them any disadvantage, so there's no evolutionary pressure to stay more symmetrical.
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Taxonomy Tournament: Cartilaginous Fish
Myliobatiformes. This order of batoids includes stingrays and manta rays.
Rajiformes. This order is made up of skates
Which clade of animals is better?
Myliobatiformes
Rajiformes
Show results
A new deep-sea softnose skate, the Western Blue Skate Notoraja hesperindica, is described based on six specimens caught in deep water at 1600 m depths off southern Mozambique and northwestern Madagascar in the western Indian Ocean.
This blue skate is a medium-sized species, reaching a total length of at least 55 cm, and is the only Notoraja species known from the western Indian Ocean and differs with other skate in the area by its intense dark blue-grayish coloration.
Reference: Weigmann et al., 2021 Notoraja hesperindica sp. nov., a new colorful deep-sea softnose skate (Elasmobranchii, Rajiformes, Arhynchobatidae) and first generic record from the western Indian Ocean. Marine Biodiversity.
Photo: a male Western Blue Skate, with a remarkable cyanine blue color.
*ART BY SILVIA PALMERONI
Mermay 2021, Day 3: Sweet
3 May 2021
Watercolours on paper
Big Skate Beringraja binoculata
Watching this big male California Sea Lion dismember a Skate at the surface was mildly terrifying, but luckily it was a safe distance from me