Subchondral Bone Apparent Density and Locomotor Behavior in Extant Primates and Subfossil Lemurs Hadropithecus and Pachylemur

Abstract

We analyze patterns of subchondral bone apparent density in the distal femur of extant primates to reconstruct differences in knee posture, discriminate among extant species with different locomotor preferences, and investigate the knee postures used by subfossil lemur species Hadropithecus stenognathus and Pachylemur insignis. We obtained computed tomographic scans for 164 femora belonging to 39 primate species. We grouped species by locomotor preference into knuckle-walking, arboreal quadruped, terrestrial quadruped, quadrupedal leaper, suspensory and vertical clinging, and leaping categories. We reconstructed knee posture using an experimentally validated procedure of determining the anterior extent of the region of maximal subchondral bone apparent density on a median slice through the medial femoral condyle. We compared subchondral apparent density magnitudes between subfossil and extant specimens to ensure that fossils did not display substantial mineralization or degradation. Subfossil and extant specimens were found to have similar magnitudes of subchondral apparent density, thereby permitting comparisons of the density patterns. We observed significant differences in the position of maximum subchondral apparent density between leaping and nonleaping extant primates, with leaping primates appearing to use much more flexed knee postures than nonleaping species. The anterior placement of the regions of maximum subchondral bone apparent density in the subfossil specimens of Hadropithecus and Pachylemur suggests that both species differed from leaping primates and included in their broad range of knee Int

Trabecular and cortical bone structure of the talus and distal tibia in Pan and Homo

“…As these individual trabeculae appear able to adapt to accommodate regional strains, it is likely that regional architectural parameters can provide information about how different areas of a joint are loaded. For example, trabecular and cortical bone distribution close to the articular surface, radiodensity patterns, and indicators of bone remodeling, correspond with predicted locations of peak loading associated with specific joint positions (Carlson, Jashashvili, Houghton, Westaway, & Patel, ; Mazurier, Nakatsukasa, & Macchiarelli, ; Patel & Carlson, ; Polk, Blumenfeld, & Ahluwalia, ; Polk, Williams, Peterson, Roseman, & Godfrey, ; Skinner et al, ; Tsegai et al, ; Zeininger, Richmond, & Hartman, ).…”

What did Hadropithecus eat, and why should paleoanthropologists care?

“…This animal was neither a leaper nor suspensory; it was also not cursorial. Polk et al [] measured the density of subchrondral bone in the distal femur to reconstruct knee postures. They found a broad range, from highly flexed to highly extended.…”

Leg Muscle Architecture in Primates and Its Correlation with Locomotion Patterns

“…Average for species if sex was unknown (annotated "*"). c Data compiled from: Napier and Walker, 1967;Thorington, 1967;Jones and Sabater Pi, 1968;Kinzey et al, 1975;Mittermeier and Fleagle, 1976;Morbeck, 1977;Rose, 1979;Ward and Sussman, 1979;Fleagle and Mittermeier, 1980;Garber, 1980;Fleagle et al, 1981;Gebo, 1987;Ford, 1988;Gautier-Hion, 1988;Snowdon and Soini, 1988;Stevenson and Rylands, 1988;Wright, 1989;Oxnard et al, 1990;Ansorge et al, 1992;Dodson et al, 1992;Garber 1992;Janson and Boinski, 1992;Gebo and Sargis, 1994;Hammerschmidt et al, 1994;Taylor, 1995;Remis, 1995;Digby and Barreto, 1996;Nakatsukasa, 1996;Rogers et al, 1996;Doran, 1997;Meldrum, 1998;Dagosto and Yamashita, 1998;McGraw, 1998;Youlatos, 1999;McGrew, 2000;Arms et al, 2002;Fleagle and McGraw, 2002;McGraw and Bshary, 2002;Schmitt, 2003b;Shapiro, 2007;Wright, 2007;Veracini, 2009;Polk et al, 2010;<...>…”