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

Re: Deltopectoral Crests and Condyles on the Humeri



MariusRomanus@aol.com wrote-
 
A friend has been doing some investigation into the osteology and he's noticed that in birds it is at a sort of 45 degree angle to the humerus. As far as I can tell, it is about the same in dromaeosaurs. Now, my question is do we know when it went from pointing forwards to bent to the side in that manner??? What animals show the change? On a side note, when you take a look at _Bambiraptor's_ you really have to sit and say to yourself that boy oh boy is there one heck of an angle, just like a bird's. (Go figure.)
 
I wouldn't say deinonychosaurs have anything as large 45 degree angle, but I see what you mean.  Sinornithoides seems to be similar, as does Mononykus.  Unfortunately, the former also looks damaged in that area, and the latter is so transformed it's hard to tell.  I don't see it in Harpymimus, Gallimimus or Ingenia, and I'm pretty sure it's absent in Therizinosaurus.  Alxasaurus and Erlikosaurus have such laterally projected deltopectoral crests, it's hard to tell.  So it _might_ be characteristic of paravians.  However, look at Elaphrosaurus and Torvosaurus, which also seem to have angled crests.

I ask only because, and this is the interesting part, basal theropods have their condyles on the distal surface. Dromaeosaurs do not. Now, much to the delight of many (and me I might add), it appears with _Microraptor_ and NGCM 91, and even _Archaeopteryx_ for that matter, that we have a highly suggestive situation here that says that your basal dromaeosaurs were arboreal.
 
This has actually been used in phylogenetic analyses for some time (apparently being noticed first by Perle et al., 1993), though I'm not sure about the functional meaning of it.  Exactly which taxa have it is controversial, as ornithomimids and oviraptorosaurs (oviraptorids, Microvenator, Caudipteryx) are always coded as lacking it and alvarezsaurids and pygostylians are always coded as having it, but other taxa are coded differently by different people-
Tyrannosauridae (0- Holtz 2002, Maryanska et al. 2002; 1- Forster et al. 1998)
Segnosauria (0- Holtz 2000; 1- Xu et al. 1999; p- Maryanska et al. 2002)
Avimimus (0- Holtz 2000; 1- Maryanska et al. 2002)
Troodontidae (0- Holtz 2000, Maryanska et al. 2002; 1- Forster et al. 1998, Xu et al. 1999)
Dromaeosauridae (0- Holtz 2000, Maryanska et al. 2002; 1- Forster et al. 1998, Xu et al. 1999)
Archaeopteryx (0- Holtz 2000, Maryanska et al. 2002; 1- Forster et al. 1998)
In addition, Holtz codes many other coelurosaurs as lacking it (Dryptosaurus, Ornitholestes, Coelurus, Scipionyx, compsognathids), as well as every other codable theropod except Piatnitzkysaurus.  The condition in Microraptor remains unknown until the Novitates paper describing the new specimens is out, as the holotype lacks a humerus.
 
Mickey Mortimer