January 25, 2006

Triassic archosaur was an Ostrich-mimic Mimic

11:02 pm

Researchers have just described a 210 million year old reptile which approximated 80 million year old dinosaurs, which in turn were approximating ostriches of today.

To try to clear that up: 80 million years ago, there lived a group of dinosaurs called ornithomimids, colloquially referred to as Ostrich-mimics. They got this name because they had independently evolved many ostrich-like features, including long, fast-running legs, and a long slender neck atop which perched a small, birdlike head complete with a toothless beak. Although they were not particularly closely related to ostriches, they found enough benefit in living an ostrich-like lifestyle to take on some of the trappings of ostrichdom.

Or ostriches took on some of the trappings of ornithomimids, depending on your perspective.

Now, if that wasn’t enough to make you want to stick your head in the sand, Sterling Nesbitt and Mark Norell have described a reptile that was doing the same thing 210 million years ago, and this one isn’t a bird or a dinosaur but an ancient relative of crocodiles.

This ancient suchian was discovered in blocks that had been excavated in the 1940s from Ghost Ranch in Northern New Mexico, a site famous for hundreds of skeletons of the early dinosaur Coelophysis. Nesbitt and Norell have named the reptile Effigia okeefeae after Ghost Ranch’s other famous resident, Georgia O’Keefe.

An early restoration of the Ostrich-mimic Struthiomimus
(and not a bad approximation of Effigia.)
From Osborn, 1917. “Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus.”Bulletin of the AMNH ; v. 35, article 43.

Like ornithomimids, Effigia walked on two long hind-legs, had a long tail, large eyes, and a toothless beak. But the distinctive arrangement of Effigia’s anklebones reveal its true non-dinosaurian nature. According to the description’s abstract, Effigia has “several derived features of the skull and postcranial skeleton [that] are identical to conditions in ornithomimids. Such cases of extreme convergence in multiple regions of the skeleton in two distantly related vertebrate taxa are rare.”

So it looks like Effigia is an Ostrich-mimic Mimic, and a darn good one at that. The completeness of this specimen helps clear up another Late Triassic mystery fossil, the toothless skull of Shuvosaurus inexpectatus. Once thought to be an extremely ancient ornithomimid, now it seems to be part of a radiation of suchian reptiles that experimented with aspects of an ostrich-type lifestyle long before dinosaurs (or ostriches, for that matter) caught on.

Tip of the toupee to Palaeoblog, who picked it up first and has a nice reproduction of Effigia’s skull.

Reuters UK has another popular article about this find.

Carl Zimmer has a story in the NY Times (registration required).

Nesbitt, Sterling J. and Norell, Mark A. “Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda).” Proceedings of the Royal Society B.

—Matt Celeskey.

File under: Recent Discoveries, Reptiles, Triassic.

Comments on record: (3)

January 23, 2006

In One Era And Out The Other

6:15 pm

A post from the HMNH curator of Ich-theology, Ray Troll:

You know that snarky feeling you get when you blow your nose too damn hard and you blow your eardrums out? Well it just might be that we have our fishy ancestors to thank for that lovely sensation. We all know that the knee bone’s connected to the thigh bone but only vaguely suspect that our lungs are connected to our ears. But once upon a time, way, way back in the Devonian days, our fishy ancestors may have been able to breathe through their ears! How cool is that? Just imagine the possibilities if we could still perform such a feat: you could fake your own drowning death in the family bathtub, win all those driving-by-the-graveyard-and-holding-your-breath contests, and snorkels would be obsolete.

“One Small Step for a Fish”
Panderichthys (bottom) and Acanthostega (top)
© Ray Troll

But seriously, Drs. Martin Brazeau and Per Ahlberg closely reexamined the inner ear chambers of the Devonian lobefin fish Panderichthys and came to the conclusion that the fish used it’s ear to gulp air. Their findings are published in the January 18, 2006 issue of Nature . Read all about it at Nature online.

I’ve long been curious about the positioning of the nostrils on the lower part of the head in this group of fish and this theory helps answer that puzzle.

—Ray Troll.

File under: Bony Fish, Devonian, Ich-Theology.

Comments on record: (3)

January 17, 2006

Sculptor Jim Gary dies

11:43 pm

Jim Gary, a sculptor who was best known for creating life-sized dinosaurs built from car parts, died this past weekend after suffering a cerebral hemorrhage last month. Gary’s brightly-colored sculptures have been displayed in museums and galleries around the world, and his work was featured in numerous magazines, books, and documentaries.

I can remember poring over photographs of his work in National Geographic World as a child, amazed that someone could make something so animated out of pieces of old “junk.” It is still a joy to look at his sculptures and let my brain slide back and forth between perceiving automobile parts and skeletal anatomy. Jim Gary’s dinosaurs show a rarely-seen combination of technical skill and unfettered whimsy, and the world is a little bit richer because of his work.

A summary of his work is online at Kafi Benz Productions, along with a collection of news and links and information about a Memorial Fund.

Photographs of his work can be seen at Lost in Jersey and this excellent collection of pictures from an exhibition at UNC-Charlotte.

—Matt Celeskey.

File under: Paleo-Pop.

Comments on record: (1)

January 11, 2006

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.

—Matt Celeskey.

File under: Cretaceous, Mammals, Recent Discoveries.

Comments on record: (2)

January 10, 2006

AMNH Brand Instant Library

8:14 pm

The mission of the American Museum of Natural History:

To discover, interpret, and disseminate – through scientific research and education – knowledge about human cultures, the natural world, and the universe.

has just been fulfilled a little further.

PDFs of more than a century of the AMNH’s scientific publications—all the Bulletins, Novitates, Anthropological Papers, and Memoirs—are available, searchable, and downloadable here.

I’ve no doubt that a lot of noble sentiments and hard work went into making this happen, and I appreciate all of it. This is the sort of thing that makes me thrilled to be living in the 21st century.

—Matt Celeskey.

File under: Recent Discoveries.

Comments on record: (2)

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