Thursday, May 24, 2018

[PaleoMammalogy • 2018] Cifelliodon wahkarmoosuch • Late-surviving Stem Mammal Links the Lowermost Cretaceous of North America and Gondwana


 Cifelliodon wahkarmoosuch 
Huttenlocker, Grossnickle, Kirkland, Schultz  & Luo, 2018

 Illustration: Jorge A. Gonzalez  nature.com

Abstract
Haramiyida was a successful clade of mammaliaforms, spanning the Late Triassic period to at least the Late Jurassic period, but their fossils are scant outside Eurasia and Cretaceous records are controversial. Here we report, to our knowledge, the first cranium of a large haramiyidan from the basal Cretaceous of North America. This cranium possesses an amalgam of stem mammaliaform plesiomorphies and crown mammalian apomorphies. Moreover, it shows dental traits that are diagnostic of isolated teeth of supposed multituberculate affinities from the Cretaceous of Morocco, which have been assigned to the enigmatic ‘Hahnodontidae’. Exceptional preservation of this specimen also provides insights into the evolution of the ancestral mammalian brain. We demonstrate the haramiyidan affinities of Gondwanan hahnodontid teeth, removing them from multituberculates, and suggest that hahnodontid mammaliaforms had a much wider, possibly Pangaean distribution during the Jurassic–Cretaceous transition.




The new species Cifelliodon wahkarmoosuch is estimated to have weighed 2.5 pounds and probably grew to be about the size of a small hare.
 Illustration: Jorge A. Gonzalez

Mammaliaformes sensu Rowe (1986) 
Haramiyida Hahn, Sigogneau-Russell and Wouters (1989) 

Hahnodontidae Sigogneau-Russell (1991) 

Cifelliodon gen. nov.

Cifelliodon wahkarmoosuch sp. nov.  


Etymology. Cifelli’s tooth (Latin: -odon) of the Yellow Cat (Ute language: yellow, wahkar; cat, moosuch). Genus name honours Richard Cifelli for his contributions to Cretaceous mammal research in the American West.

Holotype. An exceptionally preserved skull, UMNH VP 16771 (Natural History Museum of Utah, Vertebrate Paleontology Collection).

Locality and horizon. The holotype is from the ‘Andrew’s Site’ quarry in the Lower Cretaceous Yellow Cat Member, Cedar Mountain Formation, Grand County, Utah, USA15. Radiometric dating places the age between approximately 139 and 124 million years old.

Diagnosis. Medium-to-large Mesozoic mammaliaform with broad, shallow skull and rostrum and a reduced marginal tooth count; dental formula: I2:C1:PC4; ultimate upper molars with high anterobuccal cusp and low, broad posterolingual cusp connected by a low ridge; septomaxilla absent; incisive foramina enlarged and positioned posteriorly on palate behind the level of the last (posterior) incisor pair; massive pterygoid transverse process that extends far ventral to the palatal surface; attenuated lacrimal anterior process with limited nasolacrimal contact; prominent sagittal crest; extensive occipital exposure of parietal and postparietal; plesiomorphic retention of a tabular bone; differs from Hahnodon in its larger size and higher aspect ratio of the rear molar in occlusal view (slightly more triangular than oval, with posterior apex).



The new species Cifelliodon wahkarmoosuch is estimated to have weighed 2.5 pounds and probably grew to be about the size of a small hare.
 Illustration: Jorge A. Gonzalez 


Adam K. Huttenlocker, David M. Grossnickle, James I. Kirkland, Julia A. Schultz and Zhe-Xi Luo. 2018. Late-surviving Stem Mammal Links the Lowermost Cretaceous of North America and Gondwana. Nature.  DOI:  10.1038/s41586-018-0126-y
A 3D view of early mammals   nature.com/articles/d41586-018-05134-9

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