Osteoderms are bony plates found in the skin of vertebrates, mostly commonly in reptiles where they have evolved independently multiple times, suggesting the presence of a gene regulatory network that is readily activated and inactivated. They are absent in birds and mammals except for the armadillo. However, researchers at the University of Florida have discovered that in four genera (Acomys, Lophuromys, Uranomys, and Deomys) of the rodent subfamily Deomyinae, there are osteoderms in the skin of their tails.
“Osteoderms are present in this sub-family of rodents and nowhere else in living mammals except armadillos,” said lead author Dr. Malcolm Maden, a researcher at the University of Florida.
“They are absent in birds, frequent in reptiles — think of dinosaurs and crocodiles — and infrequent in frogs.”
“This means that they can be lost and re-evolved time and time again in animals, and this has happened at least 19 times.”
“What distinguishes osteoderms from other appendages of the skin is that they’re made of bone. They’re also found deep in the lower dermis layer of the skin, not on the surface.”
“That’s in contrast to scales on the epidermis of many animals, including pangolins and birds, whose feet are made of keratin.”
The researchers first spotted Acomys osteoderms in CT scans of museum specimens made for the openVertebrate program.
The effort involved CT scanning 20,000 museum specimens from all around the United States to gather high-resolution anatomical data for more than 80% of vertebrate genera.
“I was scanning a mouse specimen from the Yale Peabody Museum, and the tails looked abnormally dark,” said senior author Dr. Edward Stanley, director of the Florida Museum of Natural History’s digital imaging laboratory.
“I initially assumed the discoloration was caused by an imperfection introduced during the specimen’s preservation.”
“But when I analyzed the X-rays several days later, I observed an…
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