Hairy Museum of Natural History

A new study of the bone microstructure of the dinosaur Plateosaurus englehardti shows that this species grew up more slowly during times of environmental stress. This is a feature seen in modern reptiles but is unusual for dinosaurs, which typically show fast, steady growth rates, at least early in life.

Plateosaurus lived about 200,000,000 years ago, and its fossils are found in southwest Germany. It is one of the best-known prosauropods, a group of early herbivorous dinosaurs that branched off from the base of the family tree that led to the giant long-necked sauropod dinosaurs.

Paleontologists at the University of Bonn studied the ‘growth rings’ in the bones of Plateosaurus. From their press release:

“When growth is fast, the distance between the rings is greater. The bone tissue is then permeated with numerous longish cavities. ‘However, in many animals, at least at times, the annual rings were markedly closer together,’ Dr. Sander continues. ‘In these phases the dinosaurs seem to have only grown slowly.’ From the bone structure experts can also detect when the animals reached their full size: ‘Some had reached their maximum size at 12 years old, others were still growing at 27 – we did not investigate finds of older animals.’ The smallest plateosaur was only 4.8 metres when fully grown – a veritable dwarf. Others were more than twice as long.

“What is above all astonishing is that all the other dinosaurs seemed to show very steady growth. This is not only true of the plateosaur’s closest relations, but also of dinosaurs which came onto the evolutionary stage well before plateosaurs and which therefore could perhaps be assumed to have shown a more ‘reptilian’ type of growth. ‘These findings are puzzling,’ Martin Sander admits. ‘Of course the plateosaur may simply be an exception. However, we do not see this hypothesis as being very likely. Perhaps the extant finds have not been correctly interpreted. Or the dinosaurs’ family tree as we imagine it is simply not accurate.’ ”

Developmental Plasticity in the Life History of a Prosauropod Dinosaur. P. Martin Sander and Nicole Klein. 2005. Science 310: 1800 – 1802.

Update 12/17: BBC News has picked up the story with a small image of the Plateosaurus growth rings.

—Matt Celeskey.

File under: Dinosaurs, Triassic.

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This stocky fellow is Diadectes (Die-uh-DECK-tees), a solid, six-foot-long sprawler known from 300,000,000+ year-old remains found in North America and Europe. From our modern perspective as highly-refined terrestrial tetrapods, he might look to be little more than a lizard with a weight-control problem. For his time, however, Diadectes was a trailblazer. His distinctive teeth mark him as a plant-eater, and he is in fact the earliest vertebrate known to be a dedicated herbivore. While all of our ancient ancestors were evolving better ways to eat each other, Diadectes discovered the pastoral pleasures of Permo-carboniferous vegetarianism.

Diadectes and its relatives (collectively known as diadectomorphs) have been classed as amphibians, reptiles, or some transitional form between the two. Current studies find the Diadectomorpha to be the sister group of the Amniotes—more closely related to us than to any amphibians, yet falling just outside the group that led to modern reptiles and mammals.

As usual, all manner of animals are on parade at this week’s Friday Ark over at The Modulator.

—Matt Celeskey.

File under: Carboniferous, Tetrapods.

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Dr. Don Hall has relayed news of the discovery of a giant Cretaceous crocodile skeleton in Giles County, Virginia. The colossal fossil, nicknamed “Big Milkie,” appears to be a new specimen of Deinosuchus, a 37-foot long ‘gator that prowled the swamps of eastern North America towards the end of the Age of Dinosaurs. According the Dr. Hall, the skeleton is “extremely well-preserved, and over 72% of it has been uncovered so far.” In addition to the giant croc, researchers have discovered fossil plants, invertebrate body fossils and trackways, reptile tracks, and eggs from what might be a crocodile nesting site.

There aren’t many resources online regarding this discovery, but hopefully that will change as more work is completed. Until then, folks looking for a Deinosuchus fix can look for a copy of King of the Crocodylians: the Paleobiology of Deinosuchus. Or, for significantly less cost, download this PDF article from the North Carolina Museum of Natural Sciences, which compares North American megacroc Deinosuchus with the African “Supercroc” Sarcosuchus.

—Matt Celeskey.

File under: Cretaceous, Recent Discoveries, Reptiles.

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Another specimen of the early bird Archaeopteryx has been described. The Wyoming Dinosaur Center has a press release, and stories at National Geographic, New Scientist, and afarensis do a good job covering the details of skull and foot anatomy that make this specimen important.

But I think this fossil is most noteworthy because it shows the earliest record of a relatively advanced avian behavior—this specimen is clearly preserved doing the “funky chicken”:

In my opinion, this loosening up of Archie’s image is a welcome change from earlier Archaeopteryx fossils, which have been found in a more dramatic, “forsaken” pose:

A more scientific skeletal reconstruction of the new specimen has been made by Scott Hartman.

—Matt Celeskey.

File under: Birds, Jurassic, Recent Discoveries.

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…according to an impressive fossil trackway reported from the Carboniferous of Scotland.

The ichnofossil, described in the latest issue of Nature, shows the trail left by a 5-foot long eurypterid (your-IP-ter-id) as it hauled its body over a 330,000,000 year-old beach. Eurypterids were aquatic relatives of scorpions that thrived during the Paleozoic Era. Eurypterids were some of the top predators of their time, growing to a length of 6 feet and sporting nightmarish claws, which were the likely end of many of our fishy ancestors. Fossils of eurypterid exoskeletons are known from marine and freshwater deposits, but it has long been uncertain whether they were able to leave the water and crawl ashore.

A menacing eurypterid provides the impetus for lobe-finned fish to crawl onto the nearest beach in this detail of a mural by Margie O’Brien at the New Mexico Museum of Natural History and Science. A trackway reported from Scotland shows that these large aquatic invertebrates were coming ashore around the same time.

Unlike the menacing predator shown here, the trackway was likely made by Hibbertopterus, one of a group of eurypterids that had comb-like paddles instead of pincers. These paddles would have been used as filters to trap small invertebrates and other tiny prey items, so it is doubtful that this particular trackmaker was chasing any early tetrapods ashore.

The 20-foot long trackway preserves traces of six of the animal’s limbs digging into the muck and pulling its heavy tail behind it. The Nature article presents a photo and diagram of the trackway along with a reconstruction of the trackmaker, and a larger photo of the tracksite can be seen at BBC News.

—Matt Celeskey.

File under: Carboniferous, Recent Discoveries.

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