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Deinonychus and Albertosaurus packs

To: dinosaur@usc.edu
From: Ben Creisler (bh480@scn.org)
Subject: Deinonychus and Albertosaurus packs

I realize the "pack hunting" thread may be getting a bit stale, but
I thought I would contribute a couple of items. My apologies if
these discoveries have been cited before since I can't remember the entire
series of exchanges. (I did check with the restored search tool, though,
and think I'm not being redundant!).

1. Healed Deinonychus
Matt Bonnan's mailing from 5-3-99 raised the issue of healed
injuries in theropods as evidence of social behavior in which an injured member
of a pack or group was provided for. This argument has been used
to support social grouping in Smilodon, since individuals crippled by
injury appear to have survived.

The following item is posted on the web page of the British
Palaeontological Association, Meeting Abstracts (Portsmouth 1998) at

Fracture and osteomyelitis in PII of the second pedal digit of Deinonychus
antirrhopus (Ostrom) an Early Cretaceous 'raptor' dinosaur
Cynthia Marshall (1), Daniel Brinkman (1), Richard Lau (2) and Karl Bowman
(1) Yale University, New Haven, CT, USA
(2) Cheshire Veterinay Clinic, Cheshire, CT, USA
(3) North Carolina State University, Raleigh, NC, USA
e-mail: cynthia.marshall@yale.edu
We report here on a healing transverse, displaced, midshaft fracture of PII
of the second pedal digit of Yale Peabody Museum 5205, the type specimen of
Deinonychus antirrhopus (Ostrom). The affected phalanx bore the
sickle-shaped talon for which the animal is named.
Radiographic examination of the fossil shows a caudal and ventral
displacement of the distal fragment. The presence of osteomyelitis is
supported by lytic areas at the fracture site with evidence of a sequestrum.
Oblique views provide no evidence of longitudinal fracturing. Radiographs
support the diagnosis of a fracture due to bending, which is compatible with
damage during a slashing motion of the talon. However, pathologic fracture
subsequent to primary osteomyelitis cannot be ruled out at this time.
Sufficient stability/immobility allowed partial healing to occur prior to
the animal's death, as evidenced by lack of callous, remodelling and
smoothing of dorsal and medial sides. That this animal survived for an
unknown length of time with an injury to one of its purported major defence
and food-gathering mechanisms may support Ostrom's analysis of
gregarious/pack-hunting behavior for Deinonychus.

2. Albertosaur pack
At his 5-24-99 lecture in Seattle, Phil Currie mentioned a pack of
Albertosaurus found by Barnum Brown back in 1910 and forgotten
in the American Museum collection. There were nine individuals
collected together at the same site, about half being half-grown
juveniles with hindlimb and body proportions similar to ornithomimids.
Phil suggested these tyrannosaurids could have functioned as a pack,
and if I understand his proposed scenario correctly, the
the agile and fleet-footed juveniles would have chased and harassed
--but not directly attacked--the prey (say, a herd of duckbills or 
eventually distracting or separating out individuals that would stray
into ambush range of the larger, more powerful adults, who would
make the kill.

Don't know if this scenario requires tremendous intelligence on
the part of the dinosaurs, but Phil seems to warm to the
notion that such pack behavior was common in large theropods--the new
group of giant theropods recently found in South America apparently fits
a similar team arrangement of very large powerful adults, and faster,
more agile juveniles.