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Haldanodon

haldanodon
Haldanodon exspectatus is an extinct mammaliaform, specifically a docodont It lived in the Upper Jurassic Kimmeridgian, about 145 million years ago Its fossil remains have been found in Portugal, in the famous field Guimarota Judging by its physical features, it seems to have been an aquatic insectivore, resembling the modern desman

Contents

  • 1 Description
  • 2 Classification
  • 3 Lifestyle
  • 4 References

Description

The appearance of this animal, a little more than 38 cm 15 in in length, must have been quite similar to that of the current desman genera Desmana and Galemys, small insectivores related to the moles The body was compact, while the legs were short and robust; the articulation of the distal humerus was particularly expanded, indicating strong muscles The first forepaw phalanges were short, while those terminals were curved and laterally compressed The skull was equipped with roughness on the nasal bones, which suggest the presence of a shield of keratin The 76 cm 3 in jaws were robust; in particular, the mandible was equipped with a highly developed coronoid process, which indicated the presence of very powerful jaw muscles

Classification

The shape and arrangement of its indicate that this animal was a representative of docodonts, a group of primitive mammaliforms, but specialized with regard to the teeth, who lived in the first part of the Mesozoic Era The skeleton of Haldanodon is well known and has allowed a comparative study with that of other primitive mammaliaforms, such as the monotremes, Morganucodon and Hadrocodium According to the results of these analyses, Haldanodon would be in a position evolutionary intermediate between Morganucodon and Hadrocodium

Phylogeny [1]

Mammaliaformes 


 Adelobasileus




 Sinoconodon





 Morganucodon



 Megazostrodon





 Haramiyida





 Haldanodon



 Castorocauda





 Hadrocodium



 Mammalia








Lifestyle

Haldanodon was probably an aquatic insectivore akin to the modern platypus and desmans This is indicated by numerous skeletal features, such as the strong forelimbs and specialized ends, the skull and the cephalic shield with eyes small and tight, all adaptations for digging and swimming It occurred in a wetland environment, so aquatic foraging was very likely[2]

The wide disparity in size in the long bones of the feet such as the humerus and femur may indicate that Haldanodon never ceased to grow in size throughout the life span, such as reptiles today

References

  1. ^ Close, Roger A; Friedman, Matt; Lloyd, Graeme T; Benson, Roger BJ 2015 "Evidence for a mid-Jurassic adaptive radiation in mammals" Current Biology 25 16: 2137–2142 doi:101016/jcub201506047 PMID 26190074 
  2. ^ Thomas Martin, Postcranial anatomy of Haldanodon exspectatus Mammalia, Docodonta from the Late Jurassic Kimmeridgian of Portugal and its bearing for mammalian evolution, Forschungsinstitut Senckenberg, Senckenberganlage 25, 60325 Frankfurt am Main, Germany Received October 2004; accepted for publication March 2005
  • Kühne & Krusat 1972, Legalisierung des taxon Haldonodon Mammalia, Docodonta
  • Neues Jahrbuch für Geologie, Paläontologie and Mineralogie, Monatshefte 5, P300-302
  • Martin T 2005, postcranial anatomy of Haldanodon exspectatus Mammalia, Docodonta from the Late Jurassic Kimmeridgian of Portugal and Its bearing for mammalian evolution, Zoological Journal of the Linnean Society, 145, p 219-248
  • Martin T & M Nowotny 2000, The docodont Haldanodon Guimarota from the mines, p 91-96
  • Martin T & Krebs B eds, Guimarota - A Jurassic Ecosystem, Verlag Dr Friedrich Pfeil, München

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Haldanodon


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    Haldanodon beatiful post thanks!

    29.10.2014


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