[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Microraptor hanqingi, new species from China.

Tim has suggested that the differing leg proportions of modern birds and basal 
paravians make them poor analogs for one another.

I investigated this possibility. In Bipedalism, Flight, and the Evolution of 
Theropod Locomotor Diversity. Stephen M. Gatesy, Kevin M. Middleton. Journal of 
Vertebrate Paleontology, Vol. 17, No. 2 (Jun. 19, 1997), pp. 308-329 the leg 
proportions of various theropods are measured and plotted out.

First finding, Archaeopteryx does not group with cursors. It groups with 
Confuciusornis, Sinornis and Cathayornis. This cluster overlaps with Galliform 
birds (Fig 5 B). The nearest non avian - theropods are troodontids like 
Saurornithoides, Sinornithoides and oviraptorids like Avimimus.

So, the empirical evidence indicates that galliform birds are definitely good 
analogs for basal avialans as far as leg proportions go.
From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] on behalf of Tim Williams 
Sent: Friday, May 25, 2012 2:13 AM
To: dinosaur@usc.edu
Subject: Re: Microraptor hanqingi, new species from China.

Anthony Docimo <keenir@hotmail.com> wrote:

>  Then what is a great analog for basal paravians?

There may not be a "great analog".  Not in the modern world, anyway.
Why is it so important to have a modern analog in the first place?

With birds we have a group that evolved from within a lineage of
erect, terrestrial obligate bipeds.  This might only have happened
once in the history of the Earth (dunno about pterosaurs).  It may not
be appropriate to use behaviors documented in modern birds (which
collectively represent a highly derived subset of Avialae) to try and
reconstruct incipient arboreal or flight behaviors in basal paravians
or basal avialans.  WAIR has been criticized for this reason.

This issue is not unique to avian evolution, BTW.  There is a
hypothetical scenario for the origin of flight in insects that uses
surface-skimming behavior in stoneflies (Plecoptera) as a model for
how pterygote insects evolved fli
criticized on several fronts, especially given that Plecoptera are
fairly derived within the Pterygota, and surface-skimming in modern
stoneflies is clearly derived from flapping flight.  Also, it is not
clear whether the first pterygotes were even aquatic; for example,
basal pterygotes such as the Palaeodictyoptera (which includes the
so-called 'six-winged' insects) were terrestrial as both nymphs and

To answer Jason's query, it is quite possible that small basal
paravians moved around in trees, without needing a long or reversed
hallux.  But this is not the same as saying that they were arboreal.
To approach this issue scientifically, I think we have to identify
morphological correlates of arboreality in fossil theropods, rather
than invoke behaviors in modern birds as "easy" for any small theropod
to do.