Haldanodon

Haldanodon
Temporal range: 145 Ma
↓
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Order:Therapsida
Suborder:Cynodontia
Family:†Docodontidae
Genus:†Haldanodon
Kühne & Krusat, 1972
Species: †H. exspectatus
Binomial name
Haldanodon exspectatus
Kühne & Krusat, 1972

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 well-known fossil locality of Guimarota, which is in the Alcobaça Formation. It was an insectivore and may have been semi-aquatic.

Description

Haldanodon was about the size of Desman in length, and may have had a similar ecology. The skull of Haldanodon is well known, and there is a little of the limbones also preserved. The body was compact and the legs were short and robust. The articulation of the distal humerus was particularly expanded, indicating strong muscles for either digging or swimming. The first front paws were relatively short, and the bones were curved and laterally compressed. The roughness of the skull on the nasal bones has been suggested to indicate the presence of a shield of keratin on the head above the eyes. The 7.6 cm (3 in) jaws were robust; in particular, the mandible was equipped with a highly developed coronoid process, which is seen in close relatives of this group.

Classification

This animal belonged to a group called the docodonts: early mammaliaforms with specialised teeth[1] that lived in the Jurassic and Cretaceous. The docodonts were a widespread group in Laurasia, and show interesting ecological diversity. Haldanodon has been found as a sister group to Docodon in many analyses [1].

Phylogeny [2]

Mammaliaformes 

 

 Adelobasileus

 
 

 

 Sinoconodon

 
 

 

 

 Morganucodon

 
 

 Megazostrodon

 
 
 

 

 Haramiyida

 
 

 

 

 Haldanodon

 
 

 Castorocauda

 
 
 

 

 Hadrocodium

 
 

 Mammalia

 
 
 
 
 
 
 

Lifestyle

Haldanodon may have been a semi-aquatic insectivore similar to the modern desmans. This is indicated by some skeletal features, such as the strong forelimbs and specialized ends. However it way also have been a good digger, and the skull and possible keratin cephalic shield are all adaptations that could indicate both digging and swimming[3].

References

  1. 1 2 Luo Z-X and Martin T. 2007. Analysis of molar structure and phylogeny in docodont genera. Bulletin of the Carnegie Museum of Natural History.
  2. ↑ 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:10.1016/j.cub.2015.06.047. PMID 26190074.
  3. ↑ 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, P.300-302
  • 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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