Zadocfish2 wrote:... I was talking about this:
https://en.wikipedia.org/wiki/Yi_(dinosaur) It's a dinosaur that seemed to be following a similar trajectory to bats and, to a lesser extent, pterosaurs.
I meant that dinosaurs were "experimenting" with membranous flight even while pterosaurs were still around, meaning membranous flight evolved independently in earlier archosaurs, in dinosaurs, AND in mammals, and I find that fascinating.
Your link directs one to an empty Wiki page.
HERE is the correct Wiki reference. It seems you left off a closing parentheses.
From the Wiki entry..
...make it more likely that Yi qi was an exclusive glider. At best, the researchers who conducted the initial study of the only known Yi specimen concluded that its mode of flight should be considered uncertain.
It's hard to tie convergence to this maniraptoran theropod with pterosaurs when there isn't enough known to definitively ascribe a mode of flight. As far as I understand the subject pterosaurs all were powered fliers. If
Yi qi was an exclusive glider the convergence argument falls down.
Let's look at an informed examination of this dinosaur.
Scientific American review by Darren Nash, which I dare say knows a thing or two about the subject. Pay particular attention to the fact that some extant birds also have this sort of "skin flap".
Darren Nash wrote:So, Yi qi is a small theropod with patagia. Radical, right? Well, not so fast. What’s been mostly overlooked in discussions of Yi qi is that
pennaraptoran maniraptorans already have patagia. Look at the (perhaps familiar) pictures of nightjar wings below and observe all the ‘webbing’ that surrounds the fingers and arm. A membrane called the propatagium spans the space between the wrist and shoulder, and membranes run along the trailing (or posterior, or postaxial) edges of the hand and ulna too.
Then let's read the actual peer reviewed
publication (full PDF) found in the journal Nature Letters.
(doi:10.1038/nature14423).
"A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings"
Xing Xu, Xiaoting Zheng, Corwin Sullivan, Xiaoli Wang, Lida Xing, Yan Wang, Xiaomei Zhang, Jingmai K. O’Connor, Fucheng Zhang & Yanhong Pan
Note the closing statement from the authors quoted below, with bold emphasis added by me.
There are some indications that Yi may have relied more on gliding than on flapping, including the lack of strongly expanded muscle attachment surfaces on the forelimb bones and the possibility that the unwieldy styliform element would have interfered with the rapid oscillations and rotations of the distal part of the forelimb needed for efficient flapping flight, but the mode of aerial locomotion that is most likely for Yi remains uncertain. Regardless, the evident occurrence in this taxon of a membranous wing supported by a styliform element represents an unexpected aerodynamic innovation close to the origin of birds, and highlights the breadth of flight-related morphological experimentation that took place in the early stages of paravian history.
No part of this dinosaur adaptation followed the pterosaur model. Merely having a "wing flap" of skin does not indicate an "experiment" along the same evolutionary pathway as pterosaurs, as extant birds, as noted by Nash, also have this morphological feature. Powered flapping flight, as is found in pterosaurs, and gliding, as is suggested by the actual researchers, is not a case of convergence. My issue revolves around the notion that convergent evolution follows any other example by temporally extant organisms. It is this sort of conjecture which confuses the lay person into thinking that pterosaurs were dinosaurs. I actually addressed this on this very forum (
Science Writing Competition), and expressed my deep concerns with the confusion such comparisons instill. Lay people often conflate these distinctively differing families already, and attempting to tie convergence between pterosaurs and dinosaurs only further deepens such misunderstandings. Yes, evolution was allowing for the approach to the problem of flight in a somewhat convergent manner, but not by following any other example. If we go down that road we are forced to accept that insect flight, which predates all other forms of flight, as an example of a pattern to which all other examples follow.
Yi qi developed this morphological adaptation from the maniraptoran base from which it arose, which was experiencing a wide array of divergent experiments completely apart from those taken by pterosaurs, and was proceeded by other maniraptorans already well on their way to flight.
Sorry if my knee jerk reaction is pedantic, but to a student of dinosaur paleontology such issues matter. To me true convergence would be something like the horns on Triceratops, and those found in bovines, as both served the same function, and are expressed in the same manner.
Yi qi does not follow this pattern as petrosaurs developed powered flight and
Yi qi was most likely a glider. Only the ability to get off the ground is similar, and the similarities ends there.
RS
Sleeping in the hen house doesn't make you a chicken.
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