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Banjo catfish are a family (Aspredinidae) of tiny South American catfish which live in the major tropical river systems of the continent. Most species of banjo catfish have round flat heads and long skinny tails—hence their distinctive name. Although various sorts of banjo catfish live in many different river habitats (from quick flowing channels, to murky stagnant backwaters, to brackish tidal basins) they generally utilize the same strategy of keeping still and allowing their camouflage to protect them. Although like all catfish, they lack scales, the Aspredinidae make up for this absence with rows of horny keratin tubercles which break up their profile and leave them well disguised. Additionally they can shed their skins! As omnivores they hunt tiny invertebrates as well as feeding on whatever they can scavenge. Members of the Amaralia genera of Banjo catfish are especially fond of the eggs of other species of catfish, which they actively seek out and vacuum up.
Perhaps because they are so partial to eating the eggs of other catfish, some banjo catfish have evolved special strategies to protect their own eggs. Female catfish in the subfamily Aspredininae wait until their eggs are fertilized and then attach the developing eggs to their belly. Three species of Aspredininae develop specialized fleshy stalks called cotylephores specifically for the purpose of exchanging nutrients and oxygen between the mother and the eggs.
I wanted to add one final post to my armor posts of last week. Although I posted about chitons, Chinese helmets, glyptodons, gothic armor, and Athena, I left out a post about catfish. Ferrebeekeeper has already featured one post about the armored catfish of the Loricariidae family (an extremely large and diverse family of suckermouth catfish from South America), however there is a second different family of armored catfish, the Callichthyidae, which are characterized by two rows of bony plates (or scutes) running the length of their body. The Callichthyidae are comprised of 9 genera of catfish (and taxonomists will probably discover a few more in the future) including the Corydoras genus, which includes some of the most endearing and popular tropical aquarium fish.
Callichthyidae literally means “beautiful fish” in Greek and the endearing little fish are common in virtually every freshwater habitat throughout South America. Some species of the little armored catfish are able to flourish in stagnant or swampy water by a unique physiological mechanism. The fish gulp air into their intestines where the oxygen permeates into the blood vessels. Through this fake lung they are able to survive conditions which could kill other fish and even travel overland for brief distances (although they do look rather comic expelling the air dorsally in silvery bubbles).
A distinctive (and extremely eponymous!) example of the Callichthyidae is Callichthys callichthys an eight inch drab catfish which ranges from Trinidad to Patagonia—an extremely large range for a little fish. The male of this species is a bubble nester who builds a large nest out of plant parts and bubbles formed from air and mouth secretions. Until he is perfectly satisfied with his construction he chases the female away. Only when his nest is perfect does he let her enter: then both partners work together to defend their offspring within the little floating home.
We boldly continue armor week with an overview of the magnificent armadillo family. This order of armored mammals (Cingulata) is more diverse than any other sort of armored mammals–outshining even the scaled pangolins. Today the only living members of the Cingulata order are the armadillo family (a successful group consisting of more than 20 living species) but the armadillos’ extinct cousins were once far more widespread and bizarre. These relatives included the pampatheres–long plantigrade browsing creatures covered in banded armor who roamed the continent from one end to the other. Even more impressive were the glyptodonts, massive tank-like creatures bigger than a compact car.
The Cingulata order is part of the superorder Xenarthra. Separated from all other placental mammals for over 100 million years (due to South America’s unique isolation after the breakup of the southern supercontinent Gondwana), xenarthrans evolved in different directions from other mammals. The unique challenges and opportunities of their island continent resulted in bony domed giants like the pampatheres and glyptodonts, both of which are characterized by tortoise-like body armor composed of bone segments (osteoderms). The glyptodonts were unlike tortoises in that they could not draw their head beneath their shells: instead their heads were protected by bony caps atop their skulls. The largest glyptodonts could grow to 4 metres long, 1.5 metres high and have a mass of 3 tons (Ferrebeekeeper has already written about the smallest known Cingulata species—the pink fairy armadillo, which can still be found living in the central dry lands of Argentina).
Thanks to convergent evolution the herbivorous glyptodonts resembled other armored giants like cryptodire turtles and ankylosaurs. One species of glyptodont, Doedicurus clavicaudatus, even had a heavy spiked tail (although it is unclear whether this was used against predators or to compete for territory and mates).
When the first members of the Cingulata order emerged in the Myocene, the top predators of South America were giant running predatory birds–the Phorusrhacidae, which resembled giant dashing eagles up to 3.2 metres (10 ft) high. The glyptodonts, pampatheres, and armadillos outlasted these terror birds and they then outlasted the carnivorous metatherian mammals (with terrible saber teeth) which followed. When the Isthmus of Panama connected South America with North America (and therefore with an entirely new universe of ultra-competitive mammals), the armored cingulatans competed just fine with the newcomers. Some glyptodonts and pamphatheres wandered up through Central America and found new homes in North America. The armadillos are still there. However at the end of the last ice-age, a new African species arrived and brought a devastating and final end to the glyptodonts, the pampatheres, and most of the armadillos. But even this newly arrived predator seemed impressed by the greatest of armored mammals. An Argentine anthropologist even reports discovering a site twenty leagues from Buenos Aires where early human hunters had used glyptodont shells as dwelling places.