Pterosaurs were prehistoric winged reptiles distantly related to the dinosaurs – they were NOT actually flying dinosaurs, despite what some people might tell you. Pterosaurs are broadly categorized into two biological groups called “sub-orders”: the pterodactyloids (this is where the word “pterodactyl” comes from) and the rhamphorhynchoids. They came in all shapes and sizes, from sparrow-sized ones to creatures as large as fighter jets.

The Mesozoic Era, the geologic time frame when dinosaurs lived, is divided up into three “periods”: the Triassic Period, the Jurassic Period, and the Cretaceous Period. Pterosaurs first appeared during the middle of the Triassic Period, about 225 or so million years ago, and likely evolved from small tree-dwelling gliding reptiles.

The pterosaur depicted in this blog post comes from the late Jurassic Period. One of the best places to find fossils dated to this time is in western North America, and it is referred to as “the Morrison Formation”. This is a geological formation composed of rock layers stretching throughout much of Utah, Wyoming, and Colorado where fossils of dinosaurs and other prehistoric creatures have been found dated to the late Jurassic, spanning from 155-145 MYA.

One of the fossils which was found within the Morrison Formation was one piece of a single finger bone which was found in 1878 at Como Bluff, Wyoming. The rock layer that the bone was found in belonged to the “Brushy Basin Member” of the Morrison Formation. This would place the bone’s date during the Kimmeridgian Stage of the Jurassic Period, which lasted from about 157-152 million years ago, give or take. This fragmentary finger bone was identified as belonging to a pterosaur, one of the flying reptiles which soared over the heads of the dinosaurs during the Mesozoic Era. This discovery was noteworthy because no pterosaur fossils had been found within the Morrison Formation before. Later that year, Professor Othniel Charles Marsh of Yale University wrote an article describing this bone, and he named it Pterodactylus montanus, believing it to be from the same genus as Pterodactylus, which was known only from Europe. However, a few years later, Marsh had his doubts about this, so in 1881, he wrote a follow-up article in which he re-named the animal as Dermodactylus montanus, “the skin-finger of the mountain”.

Marsh, Othniel Charles (1878). “New pterodactyl from the Jurassic of the Rocky Mountains”. The American Journal of Science, volume 16. Pages 233-234.

Marsh, Othniel Charles (1881). “Note on American pterodactyls”. The American Journal of Science, volume 31. Pages 342-343.

Static Image

The finger bone of Dermodactylus montanus. Photograph ID number: USNM-V16797. Smithsonian National Portrait Gallery.

Based upon the size of the finger bone, and comparing it with the remains of other pterosaurs which were more complete, Dermodactylus appears to have been  a small pterodactyloid pterosaur with a 3-foot wingspan, about the size of a hawk. So far, the only fossil collected of this species is that single finger bone found in 1878, which is currently housed within the collections of the Yale Peabody Museum (collections ID: YPM 2020). No other pterosaur fossils found within the Morrison Formation have been ascribed to this genus since then. Because of this, many paleontologists today classify Dermodactylus as a nomen dubium – a classification used when scientists aren’t sure if a certain species or genus actually existed. The finger bone in question might have come from another pterosaur, and was misidentified.

This drawing was made with No. 2 pencil and Crayola and Prismacolor colored pencils.

Dermodactylus. © Jason R. Abdale. April 24, 2012.

If you want to know more about pterosaurs, I highly suggest you check out the WordPress blog “Archosaur Musings”, run by British paleontologist Dave Hone:

Also, check out Mark Witton’s (another British pterosaur expert) blog:


Categories: Paleontology, Uncategorized

Tags: , , , , , , , , , , , ,

1 reply


  1. New pterosaur species discovery by four-year-old girl | Dear Kitty. Some blog

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: