Mesozoic Mammal–Akidolestes
10:33 pm
Tip of the toupee to new ScienceBlogger afarensis for alerting me to this news from the Carnegie Museum of Natural History:
A team of scientists from Carnegie Museum of Natural History and the Nanjing Institute of Geology and Palaeontology of China report the discovery of a new species of Cretaceous mammal from the Yixian Formation in northeastern China. The mammal, named Akidolestes cifellii, was about four inches long. It likely resembled a modern shrew in general appearance, as you can see in the restoration to the left by Carnegie illustrator Mark A. Klinger.
Akidolestes is interesting because its front half shares many traits with therian mammals (the relatively advanced group made up of marsupial and placental mammals). But its spine, pelvis, and hindlimb are similar to the egg-laying monotremes, which have a more sprawling gait. Scientists think that Akidolestes is more closely related to therians than monotremes, but that it re-evolved a backside similar to those of its distant ancestors.
The CMNH press release has the following quote from curator Dr. Zhe-Xi Luo:
“Metaphorically, this newly discovered fossil mammal has a forelimb posture and gaits like those of a squirrel, with elbows tucked under its body, but its hind-limb would be sprawling with a posture that is similar to a lizard…It is quite unusual that this mammal re-acquired some primitive hind-limb feature.”
National Geographic News is carrying the story.
More images, including a stunning shot of the fossil, are available from the Carnegie Museum of Natural History.
And the scientific paper describing Akidolestes is in the current issue of Nature. The full article is available to subscribers only, but a good deal of information can be gleaned from the available figures and tables, particularly the hindlimb comparison.
Thanks for forwarding the url, Matt. I’ve added a link from my /Akidolestes/ enclosure. This ‘point thief’ critter has stolen the honour of being the first Meso mammal of 2006, as far as I know. The prize last year also went to Liaoning; /Repenomamus giganticus/. She comes from the lower Yisian fana, and is thus a bit older than this mammal. She’s also about seven times bigger. Another specimen of her sister species was also described, /R. robustus/. Remains of a crushed up /Psittacosaurus/ were in her stomach.
[...] Newly described “symmetrodont” Akidolestes is mentioned—the holotype preserves traces of the keratin that covered its spur in life. (See if you can find the spurs in this diagram.) [...]