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190 Million Year Old Dinosaur Embyro
leprasmurf writes "Sci Tech Today is reporting that scientists have cracked open a 190-million-year-old egg to reveal the oldest known dinosaur embryo. Examination of the fetal skeleton suggests the hatchling would have required parental care to survive. This would be the earliest evidence of nurturant behavior, more than 100 million years earlier than previous examples." The University of Toronto has a release about this as well. From the article: "According to Reisz, what makes this discovery particularly significant is the ability to put the embryos into a growth series and work out for the first time how these animals grew from a tiny, 15 centimetre embryo into a five metre adult. 'This has never been done for a dinosaur. Only Massospondylus is represented by embryos as well as by numerous articulated skeletons of juveniles and adults. The results have major implications for our understanding of how these animals grew and evolved,' he says."
Prosauropoda or prosauropods were a group of early herbivorous dinosaurs that lived during the Late Triassic and early Jurassic periods. They were frequently the predominant herbivore in their environment, and quickly reached large size (6 to 10 meters long). All prosauropods had a long neck and small head, forelimbs shorter than the hindlimbs, and a very large thumb claw (inherited from the thecodontosaurs) for defense. Most were semi-bipedal, although at least one large form (Riojasaurus) was fully quadrupedal. They were originally thought to be the ancestors of the sauropods, but are now considered a parallel lineage.
The Prosauropoda were originally defined as the early, bipedal, Triassic ancestors of the great sauropod dinosaurs. More recently, cladistic analysis suggests that rather than being ancestral to sauropods, prosauropods were a sister clade. Recent studies of the genus Massospondylus reveal that the Prosauropoda is indeed monophyletic. This group is a sister group to the Sauropoda, not an ancestral group.
The problem however lies in what genera are considered prosauropods. More recently, on the basis of studies of early sauropodomorphs Adam Yates proposed a cladogram in which the primitive genera Saturnalia, Thecodontosaurus, and Efraasia (basically, a paraphyletic Thecodontosauridae) represent basal outgroups prior to the Prosauropod-Sauropod split. Anchisaurus (despite its classic "prosauropod" build) is now recognised as the most primitive sauropod. The melanorosaurs and blikanasaurs are very early members of the sauropod line.
How about that.
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Even if scientists cannot extract the entire genetic code of dinosaurs from the blood samples, the scientists could make educated guesses. They then complete what, in their opinion, is the genetic code of a particular dinosaur. They then inject this code into a de-nuclearized egg of, say, a Komodo lizard to create a cloned embryo. Scientists can then use the embryonic fossilized bones to verify whether their guess is accurate. The scientists simply compare the fossilized bones with the bones of the developing embryo. If they are an exact match, then the scientists have likely cloned the genetic code of a particular dinosaur specimen.
Just a nitpick. While birds may be direct descendants from one lineage of dinosaurs, dinosaurs trace ancestry from reptiles.
Also, nurturing had a part in the evolution of bird species in so much as any other adaption helped. Evolution proceeds by natural selection based on random variation. That is, if nurturing conferred a selective advantage, then the organisms that expressed nurturing traits would tend to reproduce and propagate the genes.
I'm not sure if it is thought that mammals descended from dinosaurs or from reptiles. However, note that many mammals also display nurturing, so it is conceivable that mammals and birds trace this trait back to a common dinosaur ancestor.
I forgot to respond to this:
> Don't church-supported universities also engage in this kind of research?
I think most of them stick to real science. Even at Baylor U (affiliated with the Southern Baptists, IIRC) the science faculty threw a fit when the university president tried to set up one of the leading ID "researchers" with a position lending a false sense of scientific respectability to his views.
(FWIW, he finally landed in the Theology department at another university.)
Sheesh, evil *and* a jerk. -- Jade
I don't think you can say absolutely that a trait that exists must confer a selective advantage. There may be traits that accompany other advantageous traits but that do not confer any advantage in and of themselves. So if nurturing was somehow genetically programmed into these dinosaurs, there may have been other traits such as feathered limbs that simply came along for a ride.
Mutations on the microscale are hardly what you could call advantageous to any specific creature. It isn't until these mutations progress through lineage that they begin to take on aspect of being advantageous. We can look at our current state and say, yes, these traits definitely have provide some selective advantage (having 2 arms instead of 1, for example), but these things don't just appear fully formed.
What I'm trying to say is that for much of a trait's evolution-span, it is functionally useless, providing no selective advantage. However, through whatever means, they eventually become what we've got. As these are genetically programmed, they may bring along other vestigial traits with them that confer no selective advantage either.
But you keep breeding these mutants and eventually you get to the point where those vestigial traits start to become useful.
Part of the problem is that there are really very few points of similarity. Dinosaurs were warm-blooded, had medullary bone and laid eggs individually. None of this is true for reptiles.
The other part of the problem is that the term "Dinosaur" originated with Victorian scientists and translates loosely to "Terrible Lizard". The idea stuck, even though the fossil record simply doesn't support the theory any more.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
DNA sequencing and analysis, as well as good old-fashioned taxonomy shows that man belongs to the primates.
That and the fossil record lacking humanoid fossils older than a few million years, and having clear primates before that for a few million years, suggests humans are primates who weren't around at the creation of the first primates, but are genetically related to existing primates. *That* suggests common descent.
Darwin's theory explains (or attempts to) how even though we are related by common descent to other primates, we are clearly different species now. I.e. it is a general mechanism, not a specific claim about primate taxonomy.
Now, on the other hand, opponents of Darwin are primarily motivated by opposition to the idea that man was not an instance of special creation. Given the genetic and paleontological evidence, one would think they would carefully describe how God created, by hand, each primitive hominid, and the other primates, and then carefully destroyed each, replacing it with a more modern form, until, one day *shazam* Man was created, and all God's hand tuning could stop, except for sending Christ. Of course, they don't have such a theory. And their theory would ignore all sorts of issues about how human races developed, and how different continents got populated, and how the millions of other species existing and extinct did or did not get modified by the hand of God.
In any case, Darwin does not provide the key to hominid origins. Field and lab work provides lots of facts that need to be explained. Darwininan theory certainly favors a classical taxonomy, that postulates common descent of primates. But it is neither sufficient or necessary. But any biologist who treats humans in the same was as horses or birds or insects would be left with the same conclusion.
It just so happens that Darwin proposed his theory (and wrote Descent of Man) at a time when things like the age of the earth and the fossil record were still being understood, and all the DNA analysis and substantial field work happened afterward. The creationists simply ignore all the biology of the last 150 years, and attack what they perceive as the root of the "problem" but was really just historically early. You could imagine an alternative world, where DNA and modern taxonomy had determined the family tree of primates, and then a 21st century Darwin finally figured out how speciation worked.
The early appearance of Darwinism with only a little bit of the current evidence in some sense demonstrates how natural his ideas are.