Dromiceiomimus was distinguished from Ornithomimus edmontonicus on the basis of the following characters: humerus shorter than scapula; ulna ~70% of femoral length; preacetabular process, tibia, metatarsus and pedal digit III longer compared to femur.Russell, D. (1972). "Ostrich dinosaurs from the Late Cretaceous of western Canada." Canadian Journal of Earth Sciences, 9: 375-402.
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Twenty one autapomorphic characters have been identified in L. chanarensis, these include: the anterior inclination of the posterior dorsal neural spines, the hook-shaped femoral head and the length of digit IV and metatarsal IV being greater than digit III and metatarsal III. L. chanarensis lacks many dinosaurian characters, such as the anterior trochanter, placing it basal within Dinosauromorpha.
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Palaeogeography, Palaeoclimatology, Palaeoecology 165(3): 357–373. (HTML abstract) Confuciusornis-like features include the finger bones proportionately shorter than the metacarpals, unlike in Archaeopteryx (Lee et al. 2001). Also, the first phalanx of digit III is much shorter than the remaining phalanges, and the claw of digit II is smaller than that of digit III.Li, Quanguo, Gao, Ke- qin (2007).
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Fossil tracks can be informative about theropod pathologies but apparently pathological traits may be due to unusual behaviors. Sandstone stratum dating to the Norian in southern Wales preserves tracks of an individual with a deformed digit III attribute to the ichnogenus Anchisauripus. The distal end of the digit was consistently flexed. However, this apparent pathology could be caused by the animal rotating the tip of that digit when lifting the foot.
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Alnashetri is known only from the holotype MPCA-477, articulated hind limbs of a single individual. The holotype consists of a partial left femur, distal portions of left and right tibiae, right fibula, proximal tarsals of both ankles, a nearly complete right metatarsus, proximal and distal parts of the left metapodials and left pedal digit III. The specimen was collected at the "Hoyada de los esfenodontes" sublocality, part of the main fossiliferous locality of La Buitrera, about 30 km south of the village of El Chocόn. It was recovered from massive red sandstones that form the upper part of the Candeleros Formation of the Rio Limay Subgroup (Cenomanian to Turonian stage), close to its border with the Huincul Formation.
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During the same year and also from Hermiin Tsav, the specimen IGM 100/45 was discovered by the Joint Soviet- Mongolian Paleontological Expedition. Unlike the previous findings, this specimen is represented by a hindlimb composed of a very fragmented femur with tibia, astragalus, calcaneum, a lower tarsal, a tetradacyl pes compromising four partial metatarsals, nearly complete digits I, II and IV (although II and IV are missing the unguals) and the presumed second phalanx from the digit III. These newer remains were described by the also Mongolian paleontologist Altangerel Perle in 1982. He referred the specimen to Therizinosaurus based on the striking resemblance to Segnosaurus, another therizinosaurid genus also known from limb elements.
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The shaft of the femur is straighter and the fourth trochanter is more distally placed. The repositioning of the fourth trochanter to a more distal position causes the M. caudofemoralis longus muscle, the main femoral retractor muscle, to have greater leverage (more mechanical advantage) but conversely a decrease in the velocity of femoral retraction; consequently, Aardonyx was a powerful but slower walker than typical prosauropods. Another characteristic that suggests a slower gait in Aardonyx is the robustness of metatarsal I in comparison with those of other basal sauropodomorphs. This is evidence of a more medial, or entaxonic, position of the weight bearing axis of the foot, as opposed to a more mesaxonic position where the weight bearing axis runs through digit III.
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Barefoot hoof, lateral view. (1) Coronet band, (2) walls, (3) toe, (4) quarter, (5) heel, (6) bulb, (7) P2 (small pastern) A horse hoof is a structure surrounding the distal phalanx of the 3rd digit (digit III of the basic pentadactyl limb of vertebrates, evolved into a single weight-bearing digit in equids) of each of the four limbs of Equus species, which is covered by complex soft tissue and keratinised (cornified) structures. Since a single digit must bear the full proportion of the animal's weight that is borne by that limb, the hoof is of vital importance to the horse. The phrase "no hoof, no horse" underlines how much the health and the strength of the hoof is crucial for horse soundness.
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Following the original description of Alectrosaurus, it can be distinguished by the following traits: long slender-limbed type of tyrannosauroid; humerus long and slender; ungual and phalanx of digit I robust, laterally compressed and strongly curved; femur and tibia subequal in length; length of astragalus onefourth the combined length of astragalus and tibia. According to Carr 2005, Alectrosaurus can be distinguished based on unique traits present in the hindlimbs, such as the spike-like process extending from the caudodorsal surface of the medial condyle of the femur, the presence of an abrupt expansion in length of the anterior margin of the joint surface for the tibia on the fibula, tendon pit adjacent to the ventrolateral buttress of the astragalus undercutting the medial surface of the buttress, the dorsal margin of the proximal surface of pedal phalanx II-2 is pointed, reduced pedal digit III, the lateral condyle of pedal phalanx III-1 is significantly deeper than the medial condyle, when in distal view, stocky pedal phalanx IV-2, when examined in proximal view, the dorsal half of the joint surface for metatarsal IV on metatarsal III is dilated anteriorly, and many others.
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