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Imantodes chocoensis: New species of skinny, bug-eyed snake

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Imantodes chocoensis

Imantodes chocoensis, a new species of blunt-headed vine snake. Credit: Omar Torres-Carvajal et al.

A new, weirdly proportioned species of snake called Imantodes chocoensis has been discovered in the tropical region of Chocó, which lies on the Pacific coast of northern Ecuador, Colombia and Panama.

It belongs to the Imantodes genera of snakes, of which there are only six other known species. Otherwise known as blunt-headed vine snakes, Imantodes have a very distinct look, with blunt-ended heads; big, sometimes almost googly, eyes; long, slender bodies and rather disproportionately thin necks. Some species, such as the blunt-headed tree snake (Imantodes lentiferus) from Brazil, look downright cartoony due to their very odd proportions.

Imantodes are delicate, nimble and nocturnal, and live in the trees of Mexico, Central and South America, using the weight of their lower bodies to fling their heads and upper bodies effortlessly from branch to branch. To hunt, they press the lower third of their bodies, which is where the internal organs are kept, against a branch for support to free their heads and the rest of their bodies for snatching up prey such as lizards and frogs. Only mildly venomous, these non-aggressive snakes inject their toxins using enlarged rear fangs positioned much further down the upper jaw than the more common frontal fangs of viper and cobra snakes.

Discovered by a group of zoologists led by Omar Torres-Carvajal from the Museo de Zoología QCAZ in Ecuador on 24 April 2007, I. chocoensis was described based on several live individuals and preserved specimens that have been sitting in a number of Ecuadorian and American natural history museums, unidentified since 1994. Also known as the the Chocoan blunt-headed vine snake, it was distinguished from its relatives through an analysis of its DNA, morphological features, and colour patterns.

Imantodes chocoensis

Imantodes chocoensis' head, showing the absence of a loreal scale. Credit: Omar Torres-Carvajal et al.

What makes this new species truly unique is the absence of what’s known as the loreal scale. The lore is the region in birds, reptiles and amphibians between the eyes and nostrils, so this is where the large loreal scale sits, flanked by the preocular scale closest to the eye, and the prenasal scale next to the nostril. Every snake in Colubridae family, which contains around 65% of all living snake species, has a loreal scale, but I. chocoensis just has one big preocular scale and two postoculars (the extra one is tiny).

Stretching no more than 107 cm long,  I. lentiferus is patterned with whitish cream, copper, dark brown and black hues. Its huge, bulging eyes take up 27% of the total length of its head. Sex is determined by the presence of hemipenes, which are the snake and lizard equivalent of the penis. This elusive organ is kept inverted inside the tail until required, and in I. lentiferus’ case, is relatively long (11.2mm) and covered in large, prominent spines and several rows of smaller ones to assist the males in anchoring themselves inside the females.

hemipenis of Imantodes chocoensis

The spiny hemipenis of Imantodes chocoensis. Credit: Omar Torres-Carvajal et al.

Torres-Carvajal and his team’s analysis of I. chocoensis, published in the current issue of ZooKeys yesterday, revealed that it is so closely related to the blunt-headed tree snake (Imantodes lentiferus), they have been declared sister species. Torres-Carvajal suggests that the two could share an ancestor species whose population was split in two and forever divided with the rising of the Andes.

Here’s a video of Andrew Gray, Curator of Herpetology at Manchester Museum, handling a yellow blunt-headed snake, Imantodes inornatus, in Costa Rica:

 

Order my new book, Zombie Tits, Astronaut Fish and Other Weird Animals, here.

Bec Crew About the Author: Bec Crew is a Sydney-based science writer and award-winning blogger. She is the author of 'Zombie Tits, Astronaut Fish and Other Weird Animals' (NewSouth Press). Follow on Twitter @BecCrew.

The views expressed are those of the author and are not necessarily those of Scientific American.





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