Bird-like Dinosaur Sat On Eggs

[Guest Nicholas]

After analyzing a 77-million-year-old fossilized nest, scientists determined it was likely made by a member of a group of emu-like dinosaurs, or a dromaeosaurid, which zipped around on two legs.

Find it HERE!

[Guest Nicholas]

Dinosaur Whodunit: Solving A 77-million-year-old Mystery

ScienceDaily (Nov. 14, 2008) — It has all the hallmarks of a Cretaceous melodrama. A dinosaur sits on her nest of a dozen eggs on a sandy river beach. Water levels rise, and the mother is faced with a dilemma: Stay or abandon her unhatched offspring to the flood and scramble to safety?

Find it HERE!

[mommabetts]

Good article but I think it just left me with more questions that answers. How do they KNOW that they layed 2 at a time?

[Guest Nicholas]

Good article but I think it just left me with more questions that answers. How do they KNOW that they layed 2 at a time?

I'm hoping the bird man can clarify it, it left me puzzled as well. He'll know. He better...

[Metopocetus]

So the egg DID come before the chicken.

[Boesse]

I can answer that question mommabetts, since my undergraduate advisor (David J. Varricchio) was the one who first proposed the double oviduct hypothesis for nonavian dinosaurs.

Theropod nests, some of which can be attributed to troodon, from Egg Mountain (and possibly Landslide Butte) were found in MT in the 70's and 80's. These nests showed the eggs in paired association; the majority of eggs were more or less in pairs, and the pairs oriented radially around the center of the nest. So, Dave Varricchio and Frankie Jackson (perhaps the most experienced pair of scientists with regards to reproductive physiology of dinosaurs - other researchers that come close are Darla Zelenitsky in the article, and Horner) hypothesized that this was the result of theropod dinosaurs retaining two functional oviducts - in birds, one of the oviducts is atrophied, so to speak.

The hypothesis by Varricchio and Jackson was later 'confirmed' (I dislike the terms 'confirm', 'prove', 'verify' etc. in scientific discourse) by a find from China. A partial articulated oviraptorid skeleton turned up from the Early Cretaceous of China, and included the middle of the skeleton (i.e. the vertebral column, sacrum, pelvic girdle, hindlimbs, posterior ribcage). However, this skeleton also included a pair of eggs preserved in situ at about the position of the oviduct. I can't remember the citation, but the (albeit short) paper is either in Science or Nature (whichever has the section titled Brevia) and was published in 2005.

Bobby

[Auspex]

researchers...hypothesized that...theropod dinosaurs retain(ed) two functional oviducts - in birds, one of the oviducts is atrophied, so to speak.

I believe that this is a correct interpretation of the evidence, as it makes sense physiologically. Birds "retired" one oviduct to save weight (for flight). Why flightless birds (all of which are descended from flying ancestors) should retain this restriction was a puzzle until a researcher disabled the developing oviduct in an embryo to see whether the other would develop in its place. What happened was startling, but shed light on the puzzle: the embryo developed as a male! Seems that the genetic mechanics for dual oviducts are too far gone to re-activate.

[mommabetts]

I can answer that question mommabetts, since my undergraduate advisor (David J. Varricchio) was the one who first proposed the double oviduct hypothesis for nonavian dinosaurs.

Theropod nests, some of which can be attributed to troodon, from Egg Mountain (and possibly Landslide Butte) were found in MT in the 70's and 80's. These nests showed the eggs in paired association; the majority of eggs were more or less in pairs, and the pairs oriented radially around the center of the nest. So, Dave Varricchio and Frankie Jackson (perhaps the most experienced pair of scientists with regards to reproductive physiology of dinosaurs - other researchers that come close are Darla Zelenitsky in the article, and Horner) hypothesized that this was the result of theropod dinosaurs retaining two functional oviducts - in birds, one of the oviducts is atrophied, so to speak.

The hypothesis by Varricchio and Jackson was later 'confirmed' (I dislike the terms 'confirm', 'prove', 'verify' etc. in scientific discourse) by a find from China. A partial articulated oviraptorid skeleton turned up from the Early Cretaceous of China, and included the middle of the skeleton (i.e. the vertebral column, sacrum, pelvic girdle, hindlimbs, posterior ribcage). However, this skeleton also included a pair of eggs preserved in situ at about the position of the oviduct. I can't remember the citation, but the (albeit short) paper is either in Science or Nature (whichever has the section titled Brevia) and was published in 2005.

Bobby

Thanks for explaining that for me!

[Boesse]

the embryo developed as a male! Seems that the genetic mechanics for dual oviducts are too far gone to re-activate.

Fascinating! That is really neat. Although I'm surprised that even in ratites that couldn't be teased out. Someday someone bright will be able to make that happen.

Bobby

[Auspex]

...I'm surprised that even in ratites that couldn't be teased out....

Ratites are highly derived birds; the most basal extant family is Anseriformes (ducks and geese), and it hasn't worked on them. This may be a case of a "linked gene", where the gene to develop two oviducts is paired with one that is fatal to the embryo. To me, molecular biology borders on witchcraft (not that there's anything wrong with witchcraft)!

[Guest Nicholas]

Ratites are highly derived birds; the most basal extant family is Anseriformes (ducks and geese), and it hasn't worked on them. This may be a case of a "linked gene", where the gene to develop two oviducts is paired with one that is fatal to the embryo. To me, molecular biology borders on witchcraft

Ironically there is a television show on bird molecular biology and retro engineering to make birds into dinos.. interesting concepts.

(not that there's anything wrong with witchcraft)!

Good thing with the disclaimer, my wife would have got after you for sure!

[Auspex]

...there is a television show on bird molecular biology and retro engineering to make birds into dinos...

Why they gone messin' with that? Birds are perfectly good dinosaurs as they are!

[Guest Nicholas]

Why they gone messin' with that? Birds are perfectly good dinosaurs as they are!

I've seen it a number of times they mess around with the DNA to allow dormant traits come out, they gave an embryonic chicken a long tail, teeth, and scales.