Tag Archives: dinosaurs

Drilling at the Chicxulub impact site has unveiled the crater’s shape

The new rock core drilled at the crater impact site that is thought to have help cause the extinction of the dinosaurs 65 million years ago has helped reveal the crater’s formation and shape, including the existence of an inner ring of mountains which scientists call a peak-ring.

After a decade of planning, the project penetrated 1,335 metres into the sea floor off the coast of Progreso, Mexico, in April and May. Drillers hit the first peak-ring rocks at a depth of 618 metres, and a pinkish granite at 748 metres. Geologists know that the granite must have come from relatively deep in the crust — perhaps 8–10 kilometres down — because it contains big crystals. The size of these crystals suggests that they formed by the slow cooling of deep, molten rock; in contrast, rapid cooling at shallow depth tends to form small crystals. Finding the granite relatively high in the drill core means that something must have lifted it up and then thrown down it on top of other rocks.

That rules out one idea of how craters form, in which the pulverized rock stays mostly in place like hot soup in a bowl. Instead, the core confirms the ‘dynamic collapse’ model of cosmic impacts, in which the asteroid punches a deep hole in the crust, causing the rock to flow like a liquid and spurt skyward. That rock then falls back to Earth, splattering around in a peak ring.

To put it another way, the impact moved the earth like a pebble dropped into a pond of water, causing at least two big circular ripples that flowed just like water but then quickly froze in place to form the two concentric peak-ring mountain ranges.

The asteroid didn’t do it all

The uncertainty of science: A new study adds weight to the theory that the dinosaurs were already in decline when the asteroid hit 65 million years ago.

While some have argued that dinosaurs began petering out some 5 million or 10 million years before their final doom, the new paper suggests it started happening much earlier, maybe 50 million years before the asteroid catastrophe. In terms of species, “they were going extinct faster than they could replace themselves,” said paleontologist Manabu Sakamoto of the University of Reading in England. He led a team of British scientists who analyzed three large dinosaur family trees, looking for evidence of when extinctions began to outnumber the appearances of new species.

They found that starting to happen about 50 million years before the asteroid for most groups of dinosaurs. Two other groups showed increases rather than declines; if their results are included, the overall time for the start of dinosaur decline shrinks to 24 million years before the final demise.

I wrote a science article on this subject back in 1999, and even then the science was far from settled, with most paleontologists strongly arguing that the asteroid was only the final blow and that many other factors, including the big volcano eruption in India about that time, also contributed to the dinosaur’s extinction. That journalists and the planetary science community have pushed the asteroid as the sole factor in that extinction has been a disservice to science. The science has never been that certain.

Did some dinosaur soft tissues survive fossilization?

The uncertainty of science: New research strongly suggests that within dinosaur fossils are found many preserved soft tissues from when the creature was still living.

As early as the 1970s, researchers captured images of what looked like cellular structures inside dinosaur fossils. But did the structures contain actual tissue? Proteins commonly decay hundreds to thousands of years after an organism dies, but in rare cases they have been known to survive up to 3 million years. In a series of studies beginning a decade ago, a team led by North Carolina State University paleontologist Mary Schweitzer reported that they had extracted what appeared to be collagen, the most abundant protein in bone, from a 68-million-year-old T. rex fossil. They sequenced fragments of the protein and concluded that it closely matched that of birds, dinosaurs’ living descendants (see here and here). But other teams haven’t been able to replicate the work, and others suggested that the collagen could be contamination.

The new study, led by materials scientist Sergio Bertazzo and paleontologist Susannah Maidment, both of Imperial College London, has a different strategy for hunting down ancient proteins. Bertazzo, an expert on how living bones incorporate minerals, uses a tool called a focused ion beam to slice through samples, leaving pristine surfaces that are ideal for high-resolution imaging studies. He teamed up with Maidment to apply the technique to eight chunks of dinosaur toe, rib, hip, leg, and claw.

What they found shocked them. Imaging the fresh-cut surfaces with scanning and transmission electron microscopes, “we didn’t see bone crystallites” as expected, Maidment says. “What we saw instead was soft tissue. It was completely unexpected. My initial response was these results are not real.” [emphasis mine]

It must be noted that the new research depends on many uncertainties that still need to be replicated or confirmed.

Brontosaurus returns!

The uncertainty of science: The popular but unofficial and rejected dinosaur name “Brontosaurus” has been resurrected by paleontologists.

A new study has found that the bones that had been assigned to Apatosaurus, the term that paleontologists in the 1970s chose over the more popular term Brontosaurus, actually appear to come from two distinct but different species, and they have chosen the more popular term for one of these species.

Brontosaurus was always easy to pronounce, which has probably contributed to its popularity as a general term for dinosaurs. When it was officially rejected in the 1970s there were a lot of unhappy fans of paleontology. I suspect the modern generation of scientists, children in the 1970s, had a warm spot in their heart for the term and have thus found a way to bring it back.

New data says volcanoes, not asteroids, killed dinosaurs

The uncertainty of science: A careful updating of the geological timeline has strengthened the link between the dinosaur extinction 66 million years ago and a major volcanic event at that time.

A primeval volcanic range in western India known as the Deccan Traps, which were once three times larger than France, began its main phase of eruptions roughly 250,000 years before the Cretaceous-Paleogene, or K-Pg, extinction event, the researchers report in the journal Science. For the next 750,000 years, the volcanoes unleashed more than 1.1 million cubic kilometers (264,000 cubic miles) of lava. The main phase of eruptions comprised about 80-90 percent of the total volume of the Deccan Traps’ lava flow and followed a substantially weaker first phase that began about 1 million years earlier.

The results support the idea that the Deccan Traps played a role in the K-Pg extinction, and challenge the dominant theory that a meteorite impact near present-day Chicxulub, Mexico, was the sole cause of the extinction. The researchers suggest that the Deccan Traps eruptions and the Chicxulub impact need to be considered together when studying and modeling the K-Pg extinction event.

The general public might not know it, but the only ones in the field of dinosaur research that have said the asteroid was the sole cause of the extinction have been planetary scientists.

Newly discovered dinosaur tracks

A cluster of dinosaur tracks discovered recently in Alaska has revealed to paleontologists a wealth of new information about their behavior.

The thousands of impressions, created on a 180-meter-long portion of near-coastal flood plain, today pepper a steep mountainside. Most of the tracks, made somewhere between 69 million and 72 million years ago, were left by hadrosaurs, commonly known as duck-billed dinosaurs (the crested creatures in this artist’s representation).

The consistent and excellent preservation of tracks suggests all the footprints were created within a short time period. Varying in width from 8 to 64 centimeters, the footprints cluster within four distinct size ranges, which researchers suggest represent specific age groups within a multigenerational herd. About 84% of the tracks were made by adult and near-adult hadrosaurs and 13% by young presumed to be less than 1 year old. A mere 3% of the tracks represent juvenile hadrosaurs, a rarity that strongly suggests the young of this species experienced a rapid growth spurt and therefore spent only a short time at this vulnerable size, the researchers report online this week in Geology.

Were the dinosaurs covered by feathers or scales? Scientists disagree.

Were the dinosaurs covered by feathers or scales? Two scientists find that most had scales.

Palaeontologists Paul Barrett of the Natural History Museum in London and David Evans of the Royal Ontario Museum in Toronto created a database of all known impressions of dinosaur skin tissues. They then identified those that had feathers or feather-like structures, and considered relationships in the dinosaurian family tree.

The results, which Barrett revealed at the Society of Vertebrate Palaeontology’s annual meeting in Los Angeles in late October, indicate that although some ornithischians, such as Psittacosaurus and Tianyulong, had quills or filaments in their skin, the overwhelming majority had scales or armour. Among sauropods, scales were also the norm.

The uncertainty of science: Don’t bet any money on this result. The number of dinosaur fossils actually known is relatively tiny — making the overall database tiny as well — and further discoveries could change everything.

More evidence dinosaurs were warm-blooded

A new study has found new evidence that dinosaurs were warm-blooded and active, unlike modern reptiles. Even more surprising,

“The dinosaurs appeared to be even more active than the mammals. We certainly didn’t expect to see that. These results provide additional weight to theories that dinosaurs were warm-blooded and highly active creatures, rather than cold-blooded and sluggish.”