Tuesday, April 21, 2015

The Clawed Hoatzins: Descendants of the Jurassic World

The beloved Jurassic Park film franchise has played into our imaginations over the years, offering us a possibility of seeing dinosaurs in flesh as they are exhibited in Safaris and Zoos. While conventional science has not quite yet figured out the kinks behind the resurrection of the Dinosaurs, real life may in fact, not be so far off from fiction. Birds for instance are believed to be the direct descendants of dinosaur species, and did you know that they are commonly known and officially referred to among archeologists and paleontologists as the "modern dinos"? Indeed one only has to look at the mannerisms of many birds and imagine them many times bigger to, perhaps see a striking resemblance to how, we imagine, a dinosaur would behave.

Of all the birds that presently exist, however, there is none perhaps as remarkably reminiscent to animals of the prehistoric era than The Hoatzin (Opisthocomus hoazin). The Hoatzin, also known as the Stinkbird because of its remarkably foul stench, is a large tropical bird that is found in the swamps of the Amazon Rainforest in South America. They are a fairly large, prehistoric looking bird that feeds off of the leaves and fruit of mangrove trees. Because of their primarily herbivorous diet, the birds have a digestive system that is reminiscent to that of many ruminant mammals. Unlike other species of birds, the hoatzin is the only avian known to utilize bacterial fermentation to aid its digestive processes and possesses a large crop to aid in this process. The remarkable size of the hoatzin's crop however, has had a negative relationship with its capacity for flight as it displaces much of the space occupied by flight muscles and keel of the sternum in other birds. 

Adult Hoatzins. Photosource: wikimedia commons.

Most remarkably however, are the two sets of claws present on the wings of young birds. Although nesting in trees located over large expanses of water give the birds some protection, baby birds are still particularly susceptible to predation by avian predators such as the Great Black Hawk. In times of distress, however, the birds have devised a particularly unique survival strategy. While the adults fly about noisily in an attempt to distract predators, the young birds crawl to the edge of the nest and launch themselves over the edge and into the water. Once in the water, the birds swim under the surface so as to remain unseen and escape the sharp eyes of predatory birds. When the danger has passed, the birds are then able to use the claws on their wings to climb safely back into the nest. While this is largley reminiscent to the functional claw wings on the earliest known dino-bird Archaeopteryx, recent study has suggested that the Hoatzin wing-claw may in fact be of more recent origin as is probably caused by an atavism towards the dinosaurian finger that was pushed by the chicks' frequent need to leave the nest in order to survive. These claws are no longer present in adult birds.

Closeup of Hoatzin wing-claws, and Hoatzin chick swimming underwater.
Photosource: M. Williams Woodbridge (Natgeo Creative)
Comparison between the wings of Archaeornis (left), Hoatzin chick (center) and pigeon (right)
Photosource: http://geology.cwru.edu
Jurassic world will be in theaters world wide in June 2015

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