Ebook The skull of quadruped and bipedal vertebrates, variations, abnormalities and joint pathologies (Vol 1): Part 2

Part 2 book "The skull of quadruped and bipedal vertebrates, variations, abnormalities and joint pathologies (Vol 1)" includes content: From hominoids to hominids, australopithecus, the genus homo, migration and paleogeographic distribution of the homininae, the craniofacial puzzle in motion, the basics of structural analysis, identification of malformation, ignored pathologies.
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Ebook The skull of quadruped and bipedal vertebrates, variations, abnormalities and joint pathologies (Vol 1): Part 2 10 From Hominoids to Hominids The Upper Miocene period (between 11 My and 5.5 My) is interesting in two ways because environmental changes were conducive to the radiation of Pongidae in southern Eurasia on the one hand, and on the other hand the end of the Miocene- Pliocene transition saw the development of Australopithecus in Africa. The representatives of this period are the genera Samburupithecus, Ardipithecus, Orrorin and Sahelanthropus. The jawbone fragment recovered by Ishida and her team in 1982 in Kenya (Ishida et al. 1984; Sawada et al. 1997) enabled her to describe a new genus and species of primate called Samburupithecus kiptalami (Ishida and Pickford 1998; Pickford and Ishida 1998). The most significant morphological features of this gorilla-like species were: low location of the root of the zygomatic arch above M2, a deep arched palate, thickening of the tooth enamel and swelling of the molar cusps and decrease in molar size from M3 to M1 (Thomas and Senut 1999; Senut 2005). 10.1. Ardipithecus ramidus kadabba This is a subspecies that originated in Ethiopia in 2001 following the discovery of a few fossil remains (Hailé-Sélassié 2001; WoldeGabriel et al. 2001). The few isolated teeth and post-cranial fragments suggest clear differences with the current Great Apes, particularly in the morphology of the canines in the form of incisors. On the other hand, the characteristics of the skeleton of the limbs are reminiscent of those of Great Apes, suggesting a locomotion that was still arboreal. The Skull of Quadruped and Bipedal Vertebrates: Variations, Abnormalities and Joint Pathologies, First Edition. Djillali Hadjouis. © ISTE Ltd 2021. Published by ISTE Ltd and John Wiley & Sons, Inc. 116 The Skull of Quadruped and Bipedal Vertebrates 10.2. Praeanthropus tugenensis (= Orrorin tugenensis) This is the species name given to the genus Orrorin whose remains, dated between 5.7 My and 6.1 My, were found in the Lukeino formation sites (Lake Baringo Basin, Kenya) in 2001 (Pickford and Senut 2001; Senut et al. 2001; Sawada et al. 2002). The remains that constitute this taxon, hominoid for some and hominid for others, consist of portions of mandibulars, isolated teeth and fragmentary remains of the skeletal remains of the limbs (proximal fragments of the femur, distal diaphysis of the humerus, proximal phalanx and distal phalanx of the first ray). Dental characters bring them closer to chimpanzees and modern humans (smallness of the teeth), others of the current Great Apes and fossils (Kenyapithecus, Proconsul) like the morphology of canines and premolars. The teeth were also distinguished by a right mandibular symphysis, a thickening of the dental enamel of the molars and the absence of diastema (Senut 2005). The latter characterizing a clear reduction in the height of the canines. The characters of the appendicular skeleton, obviously derivative, were found in Australopithecus and humans, denoting bipedal locomotion (long femoral neck, antero-posterior flattening of the femoral neck, anterior torsion of the femoral head, position of the lesser trochanter, etc.). However, the morphology of the humerus and phalanxes rather suggesting an arboreal adaptation (Gommery and Senut 2002). 10.3. Sahelanthropus tchadensis While for a very long time paleontological research was concentrated in East Africa, then in South Africa, nobody suspected the presence of Hominoid and Hominid fossils in sub-Saharan Africa, in the middle of the Sahelian territory. For more than 20 years, Brunet and his Franco-Chadian team criss-crossed Chad, first in search of Miocene Large Mammals. It was in 2002 that his first Hominoid discovery was made around the world. The new taxa of the genus and species Sahelanthropus tchadensis, about 7 My, are essentially based on the presence of a partially crushed skull (Vignaud et al. 2002). The inventors placed the specimen, not in the lineage of the Great Apes, but in the origin of the Hominids, making this taxon the oldest of the lineage. Their arguments were based on the small canine tooth, flattening of the face, anterior position of the foramen magnum, robust morphology probably related to dimorphism and crowns of the lower jugular teeth (Brunet et al. 2002). However, the paleontologist community is divided: first on the reconstitution of the calvarium, and then on the arguments put forward defending the hypothesis of a Hominid rather than a Great Ape. The flattened face of the specimen, identified as male, was in contradiction with the smallness of the canine (crown and root). The root development in males considerably increased the superior and anterior-apical region, From Hominoids to Hominids 117 giving the face a bulging morphology, which was not the case here. As for the virtual reconstitution of the fossil, the parameters of analysis seemed erroneous, for example the points of the FM (fronto-mastoid) line passing through the top of the mastoid apophysis when it should pass through the basion. Here the line appears much less verticalized and passed being close to modern man, whose flexion is more advanced than in Australopithecus. Moreover, the structural dynamics of the Chadian fossil is in a perspective belonging to the extensive craniofacial dynamics of quadrupeds. In other words, the flattening of the nuchal floor, the absence of basi-occipital flexion, the great anterior-posterior extension of the neurocranium, even greater than that of the Australopithecus, and the great height of the crown of the canine (despite its smallness) exceeding the occlusal plane, thus inscribing ...