Re: Triceratops defence

[Betty Cunningham <bettyc@flyinggoat.com>]

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...

-Betty

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

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