While doing my work on the TWG matrix, I noticed something interesting. A brief intro to the structures described here is helpful. Theropods have an anterior trochanter (also called lesser trochanter) on the front of their proximal femur. In birds and various maniraptoriforms it partially or completely fuses to the greater trochanter to form a trochanteric crest. First recognized in Microvenator, a lot of taxa also have another trochanter right below the anterior trochanter, called the accessory trochanter. Supposedly, therizinosauroids have a low, separate anterior trochanter but no accessory trochanter. I think people have just been confusing their accessory trochanter for an anterior trochanter, while the real anterior trochanter is fused in a trochanteric crest. Note the figure below...
References- Currie and Russell, 1988. Osteology and relationships of Chirostenotes pergracilis (Saurischia, Theropoda) from the Judith River (Oldman) Formation of Alberta, Canada. Canadian Journal of Earth Sciences. 25, 972-986.
Hutchinson, 2001. The evolution of femoral osteology and soft tissues on the line to extant birds (Neornithes). Zoological Journal of the Linnean Society. 131, 169-197.
Russell and Dong, 1994. The affinities of a new theropod from the Alxa Desert, Inner Mongolia, People’s Republic of China. Canadian Journal of Earth Sciences. 30, 2107-2127.
Zanno, 2010a. Osteology of Falcarius utahensis: Characterizing the anatomy of basal therizinosaurs. Zoological Journal of the Linnaean Society. 158, 196-230.
Zanno, 2010b. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology. 8(4), 503-543.
Graphically, I feel a circle around the area, or a highlighter-type markation (yellow or such) would read better. Your lines are not so readily legible.
Be sure to click on the figure to enlarge. :) The circle would have been a good option though.ReplyDelete