In the skeletons of the phytosaurs and most of the pseudosuchians this joint bends around a peg on the astragalus which fits into a socket in the calcaneum ( the crocodile normal tarsus ); only in the skeletons of the ornithosuchid pseudosuchians a peg on the calcaneum fits into a socket in the astragalus ( the crocodile reversed tarsus ).
32.
The implication that the ancestors of snakes had hind legs is confirmed by fossil evidence : the Cretaceous snake " Pachyrhachis problematicus " had hind legs complete with hip bones ( pubis, ischium ), thigh bone ( femur ), leg bones ( tibia, fibula ) and foot bones ( calcaneum, astragalus ) as in tetrapods with legs today.
33.
Asides from the aforementioned characteristics, " Litorosuchus " can also be differentiated from other archosauriforms by a unique combination of other characters : only two teeth are present on the premaxilla, and are situated close to the front of the bone; the maxillary calcaneum is a simple butt joint ( the bones meet in flat surfaces, not ball-and-socket joints ).
34.
Allain ( 2005 pp . 75 76 ) diagnoses " Erectopus superbus " as follows : " Rounded anterior ramus of maxilla; slender neck of femur; posterior curvature of proximal half of femur; anterodorsal edge of calcaneum dorsally projected; calcaneum twice as long as deep vertically; posteromedial process for tibia on articular surface of astragalus; length of second metatarsal equal to half the length of femur; lateral margin of proximal end of second metatarsal regularly concave ."
35.
Allain ( 2005 pp . 75 76 ) diagnoses " Erectopus superbus " as follows : " Rounded anterior ramus of maxilla; slender neck of femur; posterior curvature of proximal half of femur; anterodorsal edge of calcaneum dorsally projected; calcaneum twice as long as deep vertically; posteromedial process for tibia on articular surface of astragalus; length of second metatarsal equal to half the length of femur; lateral margin of proximal end of second metatarsal regularly concave ."
36.
Parts of the appendicular skeleton ( limbs, hips, and shoulder bones ) are preserved in " Echinerpeton " specimens, including the interclavicle, scapula ( shoulder blade ), the lower portion of the humerus ( upper arm bone ), the illium ( a hip bone ), the upper portion of the femur ( upper leg bone ), the tibia and fibula ( lower leg bones ), astragalus and calcaneum ( ankle bones ), and metatarsals ( foot bones ).
37.
The skeletal elements recovered for this type specimen of " Murusraptor " include a partial skull consisting of a complete braincase with frontals and parietals, right lacrimal, prefrontal, postorbital, quadrate, pterygoid, epipterygoid and ectopterygoid, thirty-one teeth, the rear elements of the right lower jaw, twelve vertebrae from the back, sacrum and tail, eleven thoracic ribs, a single haemal arch or chevron bone, several gastralia, a third manual ungual, complete left ilium, part of a right ilium, proximal ends of both pubic bones, distal ends of the ischia, the right tibia, and a calcaneum.
38.
According to Brusatte et al . ( 2011 ), " Dryptosaurus " can be distinguished based on the following characteristics : the combination of a reduced humerus ( humerus : femur ratio = 0.375 ) and a large hand ( phalanx I-1 : femur ratio = 0.200 ), the strong mediolateral expansion of the ischial tubercle, which is approximately 1.7 times as wide as the shaft immediately distally, the presence of an ovoid fossa on the medial surface of the femoral shaft immediately proximal to the medial condyle, which is demarcated anteriorly by the mesiodistal crest and demarcated medially by a novel crest, the presence of a proximomedially trending ridge on the anterior surface of the fibula immediately proximal to the iliofibularis tubercle, the lip on the lateral surface of the lateral condyle of the astragalus is prominent and is overlapping the proximal surface of the calcaneum, metatarsal IV is observed with a flat shaft proximally, resulting in a semiovoid cross section that is much wider mediolaterally than it is long anteroposteriorly.
