Cayetana Martinez-Maza

Paleobiology and comparative morphology of a late Neandertal sample from El Sidrón, Asturias, Spain

Fossil evidence from the Iberian Peninsula is essential for understanding Neandertal evolution and history. Since 2000, a new sample ≈43,000 years old has been systematically recovered at the El Sidrón cave site (Asturias, Spain). Human remains almost exclusively compose the bone assemblage. All of the skeletal parts are preserved, and there is a moderate occurrence of Middle Paleolithic stone tools. A minimum number of eight individuals are represented, and ancient mtDNA has been extracted from dental and osteological remains. Paleobiology of the El Sidrón archaic humans fits the pattern found in other Neandertal samples: a high incidence of dental hypoplasia and interproximal grooves, yet no traumatic lesions are present. Moreover, unambiguous evidence of human-induced modifications has been found on the human remains. Morphologically, the El Sidrón humans show a large number of Neandertal lineage-derived features even though certain traits place the sample at the limits of Neandertal variation. Integrating the El Sidrón human mandibles into the larger Neandertal sample reveals a north–south geographic patterning, with southern Neandertals showing broader faces with increased lower facial heights. The large El Sidrón sample therefore augments the European evolutionary lineage fossil record and supports ecogeographical variability across Neandertal populations.

Mitochondrial DNA of an Iberian Neandertal suggests a population affinity with other European Neandertals

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Postnatal changes in the growth dynamics of the human face revealed from bone modelling patterns

Human skull morphology results from complex processes that involve the coordinated growth and interaction of its skeletal components to keep a functional and structural balance. Previous histological works have studied the growth of different craniofacial regions and their relationship to functional spaces in humans up to 14 years old. Nevertheless, how the growth dynamics of the facial skeleton and the mandible are related and how this relationship changes through the late ontogeny remain poorly understood. To approach these two questions, we have compared the bone modelling activities of the craniofacial skeleton from a sample of subadult and adult humans. In this study, we have established for the first time the bone modelling pattern of the face and the mandible from adult humans. Our analyses reveal a patchy distribution of the bone modelling fields (overemphasized by the presence of surface islands with no histological information) reflecting the complex growth dynamics associated to the individual morphology. Subadult and adult specimens show important differences in the bone modelling patterns of the anterior region of the facial skeleton and the posterior region of the mandible. These differences indicate developmental changes in the growth directions of the whole craniofacial complex, from a predominantly downward growth in subadults that turns to a forward growth observed in the adult craniofacial skeleton. We hypothesize that these ontogenetic changes would respond to the physiological and physical requirements to enlarge the oral and nasal cavities once maturation of the brain and the closure of the cranial sutures have taken place during craniofacial development.

Phylogenetic signal in bone histology of amniotes revisited

Legendre, L, Le Roy, N, Martinez‐Maza, C, Montes, L, Laurin, M & Cubo, J. (2012). Phylogenetic signal in bone histology of amniotes revisited. —Zoologica Scripta, 42, 44–53.

Bone remodelling in Neanderthal mandibles from the El Sidron site (Asturias, Spain)

Skull morphology results from the bone remodelling mechanism that underlies the specific bone growth dynamics. Histological study of the bone surface from Neanderthal mandible specimens of El Sidrón (Spain) provides information about the distribution of the remodelling fields (bone remodelling patterns or BRP) indicative of the bone growth directions. In comparison with other primate species, BRP shows that Neanderthal mandibles from the El Sidrón (Spain) sample present a specific BRP. The interpretation of this map allows inferences concerning the growth directions that explain specific morphological traits of the Neanderthal mandible, such as its quadrangular shape and the posterior location of the mental foramen.

Brief Communication: Identification of Bone Formation and Resorption Surfaces by Reflected Light Microscopy

Developmental and evolutionary changes in craniofacial morphology are a central issue in paleoanthropology, but the underlying bone growth processes have been scarcely studied. Relevant knowledge on bone growth dynamics can be obtained from the spatial distribution of bone formation and resorption activities. Determining these patterns from the valuable samples typically used in anthropology and palaeoanthropology necessarily implies nondestructive procedures. In this work, we present a methodology based on the analysis of high-resolution replicas by reflected light microscopy, describing how microfeatures related to bone formation and resorption activities are recognized on both recent and fossil bone surfaces. The proposed method yields highly similar images to those obtained with scanning electron microscope and has proven its utility in an analysis of a large sample of extant and extinct hominoids.

Historical Determinants of Mammal Diversity in Africa: Evolution of Mammalian Body Mass Distribution in Africa and South America During Neogene and Quarternary Times

Local mammalian communities in Africa present the highest species richness in the world, only paralleled by some communities in the Oriental biogeographic region. Differences in mammalian species richness are especially outstanding when compared with South American communities, despite their similar latitudinal position and regional species richness. Recent study has shown that these differences are not only related to contemporary determinants but also to biogeographic-historic factors, which acted on the composition of the regional pool of species. One of the main differences in composition between the two regions relates to the high diversification of large mammals in Africa, which greatly contributes to the high values of local community richness in this region. The absence of extant large mammals in the South American region has been proposed to result from Pleistocene-Holocene extinctions, which affected large mammals all over the world. However, a gradual pattern of decrease in the abundance of large mammal species can be appreciated in almost all regions except Africa since the late Miocene and through the Pliocene. To test these hypotheses we compare the patterns of macromammal body mass distribution — at regional and local scales — in the two regions over the past 20 million years and relate the observed changes to major geological events.

Life-history traits of the Miocene Hipparion concudense (Spain) inferred from bone histological structure.

Histological analyses of fossil bones have provided clues on the growth patterns and life history traits of several extinct vertebrates that would be unavailable for classical morphological studies. We analyzed the bone histology of Hipparion to infer features of its life history traits and growth pattern. Microscope analysis of thin sections of a large sample of humeri, femora, tibiae and metapodials of Hipparion concudense from the upper Miocene site of Los Valles de Fuentidueña (Segovia, Spain) has shown that the number of growth marks is similar among the different limb bones, suggesting that equivalent skeletochronological inferences for this Hipparion population might be achieved by means of any of the elements studied. Considering their abundance, we conducted a skeletechronological study based on the large sample of third metapodials from Los Valles de Fuentidueña together with another large sample from the Upper Miocene locality of Concud (Teruel, Spain). The data obtained enabled us to distinguish four age groups in both samples and to determine that Hipparion concudense tended to reach skeletal maturity during its third year of life. Integration of bone microstructure and skeletochronological data allowed us to identify ontogenetic changes in bone structure and growth rate and to distinguish three histologic ontogenetic stages corresponding to immature, subadult and adult individuals. Data on secondary osteon density revealed an increase in bone remodeling throughout the ontogenetic stages and a lesser degree thereof in the Concud population, which indicates different biomechanical stresses in the two populations, likely due to environmental differences. Several individuals showed atypical growth patterns in the Concud sample, which may also reflect environmental differences between the two localities. Finally, classification of the specimens’ age within groups enabled us to characterize the age structure of both samples, which is typical of attritional assemblages.

Deer antler innervation and regeneration.

Nervous system injuries are a major cause of impairment in the human society. Up to now, clinical approaches have failed to adequately restore function following nervous system damage. The regenerative cycle of deer antlers may provide basic information on mechanisms underlying nervous system regeneration. The present contribution reviews the actual knowledge on the antler innervation and the factors responsible for its regeneration and fast growth. Growing antlers are profusely innervated by sensory fibers from the trigeminal nerve, which regenerate every year reaching elongation rates up to 2 cm a day. Antler nerves grow through the velvet in close association to blood vessels. This environment is rich in growth promoting molecules capable of inducing and guiding neurite outgrowth of rat sensory neurons in vitro. Conversely, endocrine regulation failed to show effects on neurite outgrowth in vitro, in spite of including hormones of known promoting effects on axon growth. Additional studies are needed to analyze unexplored factors promoting on growth in antlers such as electric potentials or mechanical stretch, as well as on the survival of antler innervating neurons.

Bone growth dynamics of the facial skeleton and mandible in Gorilla gorilla and Pan troglodytes

Adult craniofacial morphology results from complex processes that involve growth by bone modelling and interactions of skeletal components to keep a functional and structural balance. Previous analyses of growth dynamics in humans revealed critical changes during late ontogeny explaining particular morphological features in our species. Data on bone modelling patterns from other primate species could help us to determine whether postnatal changes in the growth dynamics of the craniofacial complex are human specific or are shared with other primates. However, characterizations of bone modelling patterns through ontogeny in non-human hominids are scarce and restricted to isolated data on facial and mandibular regions. In the present study, we analyse the bone modelling patterns in an ontogenetic series of Pan and Gorilla to infer the growth dynamics of their craniofacial complex during postnatal development. Our results show that both Pan troglodytes and Gorilla gorilla are characterized by species-specific bone modelling patterns indicative of a mainly forward growth direction during postnatal development. Both species show minor but consistent ontogenetic changes in the distribution of bone modelling fields in specific regions of the face and mandible, in contrast to other regions which show more constant bone modelling patterns. In addition, we carry out a preliminary integrative study merging histological and geometric morphometric data. Both approaches yield highly complementary data, each analysis providing details on specific growth dynamics unavailable to the other. Moreover, geometric morphometric data show that ontogenetic variation in the modelling pattern of the mandibular ramus may be linked to sexual dimorphism.