sickles and toes, or, two digit II unguals way up

[Farlow@SMTPLINK.IPFW.INDIANA.EDU]

     On the recent discussion about how dromaeosaurs may have carried their 
     big digit II claws during walking, let me resurrect some observations 
     I posted last summer about a possible modern analogue.  The two 
     species of seriemas (_Chunga burmeisteri_ and _Cariama cristata_) both 
     have a large claw on digit II that is reminiscent of (but not 
     identical to) the configuration seen in dromaeosaurs.  I have looked 
     at study skins of these birds in museum collections, videotaped them 
     during walking, and collected casts of their footprints.  The digit II 
     claw seems to be held well off the ground, but its tip does leave a 
     mark if the bird's foot sinks deeply enough.  If you have access to a 
     zoo with live seriemas, or a museum with seriema study skins, by all 
     means have a look at these birds.  They're sort of the New World 
     ecological equivalents of secretarybirds, and of all the birds I've 
     worked with during my footprint studies, they're close to my 
     favorites.
     
     If I had to guess what a _Deinonychus_ footprint would look like, I'd 
     expect nice long impressions of digits III and IV, along with a short 
     but stout pad corresponding to the joint between phalanges 1 and 2 of 
     digit II.  There might be a pit made by the tip of the digit II claw 
     if the footprint were deep enough, but I would not expect to see a 
     continuous toemark running from the proximal pad to the tip of this 
     claw.  So I think that proximal part digit II did help support the 
     animal's weight, but not the distal part.
     
     With regard to _Irenichnites_, earlier this month I was looking at a 
     Cretaceous footprint identified as having been made by a small 
     theropod in the collection of the Tyrrell Museum.  It wasn't 
     identified to ichnogenus, but if it had been I'll bet it would have 
     been identified as _Irenichnites_.  To my eye it looked like a big 
     _Anomoepus_.  Whoa.  Had to sit down and think about that one for a 
     while..... I'm hoping to borrow a cast of this print and compare it 
     more closely with _Anomoepus_ footprint casts in my collection.  Stay 
     tuned.