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Re: Triceratops defence

this is great!
My knee comment was only to place the tendon location on the leg, that
is, the musle attachment behind the knee that flexes the lower leg. 

I didn't know if this was a deep muscle (under another muscle) or a
surface msucle or not on ceratopians and such.  

I don't yet follow the leg muscles from the tail/upper thigh flexor
muscle through to the knees so I didn't know if that muscle continued
down into the lower leg...


Matthew BONNAN wrote:
> Betty:
> You said: "Could a ceratopian or hadrosaur or other herbivourous
> dinsoaur be
> ham-strung?  That is, do they also have the large tendon of the leg
> exposed near the knee as do large mammals?"
> Well, all tetrapods have "hamstrings," which are the muscles on the
> posterior side of the thigh (femur) that help flex the leg and
> partially extend the femur.  I think you might mean the gastrocnemius
> muscle, which is the large "calf" muscle on the posterior surface of
> your leg.  It originates on the proximal end of the tibia (in some
> tetrapods, portions of the muscle bellies of the gastrocnemius are
> seen in anterior view) and combines with the soleus and plantaris
> muscles to form the calcaneal or "Achilles" tendon.  In mammals, the
> "Achilles" tendon inserts on the calcaneal tuberosity and when these
> muscles contract, the foot (pes) plantarflexes (the toes point down,
> the heel moves up) and helps to push the leg off the ground during
> locomotion.
> In dinosaurs, a calcaneal tuberosity is not developed and the ankle
> is hinge-like.  Instead, in reptiles (and in birds with some
> differences), the "Achilles" tendon inserts onto a tough tissue on the
> sole and "heal" of the foot (pes) called the plantar apneurosis.  The
> plantar apneurosis acts like the calcaneal tuber in mammals and helps
> give the gastrocnemius muscle a better angle of insertion on the foot.
>  Something like this was probably present in Triceratops, though to
> what degree is difficult to tell because the plantar apneurosis does
> not leave muscle scars.
> In addition, the knee of all known dinosaurs (at least that I've seen
> and am aware of) did not have a patella to assist the quadruceps
> muscles inserting onto the tibia.  To compensate for this "loss of
> leverage," dinosaurs and other reptiles have developed a larger
> cnemial crest to keep a decent lever advantage for these leg-extending
> muscles.  The cnemial crest is sometimes called the tibial tuberosity,
> and it is located just under the proximal portion of the tibia.
> In birds, we many times find at least cartilaginous patellae in the
> knee, but in 'gators and crocs we usually don't find any sort of
> sesamoids.  There is "roughened" tissue (sometimes called
> fibrovessicular) in the knee and elbow regions of 'gators and crocs
> that may act like patellae or sesamoids, but we don't find ossified
> kneecaps.
> Hope this helps?
> Matt Bonnan
> Dept. Biological Sciences
> Northern Illinois University

Flying Goat Graphics
(Society of Vertebrate Paleontology member)