image source Name Meaning: Bird Reptile
buy cheap lasix online Geologic Era: Late Cretaceous
Location Discovered: Hell Creek Formation, Montana
Size: Small (under a foot in length)
Estimated Range: Modern Montana/North Dakota
Extinction Date: 65 million years ago (K-Pg extinction)
Avisaurus is represented in the museum by a potential tooth. I say potential because no conclusively identified Avisaurus teeth have been recovered to date, but the tooth does compare favorably to similar, better known relatives. If seen today, Avisaurus and its relatives probably would not attract much notice, until they opened their mouths and revealed a respectable complement of teeth. I would say a fair analogy would be a robin that could bite, instead of peck you.
Avisaurus belonged to a group of animals called the enantiornitheans. Superficially, these animals closely resembled modern birds, with a few notable exceptions. First, enantiornitheans had teeth, which modern birds do not. Second, they also retained clawed fingers on the forelimb. This lineage became extinct when the non-avian dinosaurs did, and are not thought to have left any living descendants. They are found worldwide, though Avisaurus is the only representative of the group from the Hell Creek Formation thus far. Given the extremely fragmentary nature of Avisaurus (only the tarsometatarsus is known), it is difficult to predict exactly what this animal looked like, though it was probably similar in appearance to other enantiornitheans.
Given how widespread these animals were, both in the temporal and geographic sense, they must have had some diversity in terms of diet. There was also likely diversity in terms of habits and habitats. The only continent where enantiornitheans have not yet been found is Antarctica, though with the current expeditions to that continent, it is possible that will change. I would like to add a word of caution to fellow fossil enthusiasts, however. I am seeing an absolutely alarming number of this type of animal specimen showing up on the internet for sale, many listed as being of Chinese origin. In fact, many bear a close resemblance to skeleton pictured above. There are two glaring problems with this. The first is that China has had an export ban on fossils since 2011. The second is, these specimens are often sold as authentic fossils. So, if they are real, they are illegal to own, but if they are legal, they are fakes. Several that I have noted command high price tags. Many are listed as being from “Confuciousoris,” which is a valid genus. Be careful what you buy, and certainly do your research first.
Full skeleton: By Jingmai K. O’Connor, Luis M. Chiappe, Chunling Gao, and Bo Zhao – http://www.app.pan.pl/article/item/app20100047.html, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=25498016
Life Restoration: By Tomozsaurus – http://tomozaurus.deviantart.com/art/Hell-Creek-Harmony-335062757, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=37145041