Welcome to the Curious Sengi!

What is that thing?!?

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Macroscelides proboscideus, the short-eared elephant shrew.  Image credit:  “Elephant shrew : )” by Black Zack is licensed under CC BY 2.0.

 

The sengi is known by many names:

  • elephant shrew
  • jumping shrew
  • Rüsselspringer (German)
  • Elefantenspitzmaus (German)
  • Slurfhondjes (Dutch)
  • rat à trompe (French)
  • hanejinezumi (Japanese) 

This strange little creature defied description for generations of naturalists and scientists.  Despite all the attention common names give to its wonderful wiggly snoot, these animals are scientifically termed “Macroscelidea,” which means “large thigh.”  While this is certainly true for these active runners, it does seem rather rude to point this out when there are more charming, distinctive features available.

Over the years, the sengi has been variously classified alongside lagomorphs (rabbits and their kin), ungulates (hoofed mammals), scandentia (tree shrews), primates, and, of course, insectivores such as shrews and moles.  In 1998, a study based on molecular data revealed an astonishing relationship:  sengis share the family tree with tenrecs, aardvarks, golden moles, sirenians, hyrax, and. . . . elephants.

In a weirdly prophetic way, we found that elephant shrews are more closely related to elephants than they are to shrews!

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An unlikely family reunion.  Clockwise from top left:  African elephant (Loxodonta africana), golden-rumped sengi (Rhynchocyon chrysopygus), streaked tenrec (Hemicentetes nigriceps), dugong (Dugong dugon), Eastern tree hyrax (Dendrohyrax validus), and aardvark (Orycteropus afer).  Image credit:  Jonathan Kingdon via Hedges 2001.

This oddball assortment of mammals — now known as the superorder Afrotheria — is tied together by shared descent from a common ancestor in Africa dating back to at least the mid-Cretaceous period, approximately 100 million years ago.

While the molecular evidence supporting this relationship is robust, a coherent morphological narrative showing the evolution of this group of animals is still unknown.  What explains the presence of long, flexible noses in elephants and elephant shrews?  How is it possible for a related group of animals to generate both a tiny, blind, desert digger like the golden mole and over a thousand pounds of purely aquatic manatee?  The evidence for this amazing history is out there, in undiscovered fossils still encased in African rocks and in the bodies of the living animals themselves.  Nature is filled with such wonders and enigmas, if we only have the patience to uncover these stories.

This is an invitation to dig around and look closer. . .

 

References

Hedges, S.B.  2001.  “Afrotheria:  Plate Tectonics Meets Genomics.”  Proceedings of the National Academy of Sciences 98 (1):  1 – 2.  doi: 10.1073/pnas.98.1.1

Rathbun, G.S.  “Sengis.”  The Princeton Encyclopedia of Mammals.  Ed. D.W. Macdonald.  Princeton University Press.  76 – 81.

Stanhope, M.J. et al.  1998.  “Molecular Evidence for Multiple Origins of Insectivora and for a New Order of Endemic African Insectivore Mammals.”  Proceedings of the National Academy of Sciences 95 (17):  9967 – 9972.  doi: 10.1073/pnas.95.17.9967

 

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