First osteohistological and histotaphonomic approach of Equus occidentalis Leidy, 1865 (Mammalia, Equidae) from the late Pleistocene of Rancho La Brea (California, USA).

Rancho La Brea (California, USA) is the most emblematic Quaternary fossiliferous locality in the world, since both the high number and diversity of the specimens recovered and their excellent preservational quality. In the last decades, paleobiological and paleoecological knowledge of the different groups of mammals from this site has increased notably; however, some aspects have not yet been inquired or there is little information. In this work we provide information on one of the most abundant mammals of this site, the equid Equus occidentalis, based on the study, from osteohistological and histotaphonomic perspectives, of thin sections of different limb bones. On the one hand, from an osteohistological viewpoint, we observe that the distribution and characterization of bone tissues in the different skeletal elements are, in general lines, similar to that mentioned for other extant and extinct equids. Cyclical growth marks allowed us to propose preliminary skeletochronological interpretations. On the other hand, from a taphonomic viewpoint, we note that all the samples reflect an excellent preservation of the bone microstructure, slightly altered by different pre- and post-burial processes. The variations recorded evidence different taphonomic history and preservation conditions among pits. This is the first study including fossil material from Rancho La Brea exclusively based on the analysis of the bone microstructure features.

Síndrome do osso navicular acessório / Accessory navicular bone syndrome

O osso navicular acessório, do qual foram descritas três variantes, é frequentemente considerado uma variação anatômica normal.É uma anomalia congênita em que a tuberosidade do navicular se desenvolve a partir de um centro de ossificação secundário e tem uma incidência estimada entre 2% e 14% com maior incidência em mulheres sendo bilateral em 50-90% dos casos. Nosso objetivo foi relatar um caso e revisar a literatura acerca desta lesão incomum, utilizando-se da revisão do prontuário, registro fotográfico do método diagnóstico e revisão da literatura. Mulher de 59 anos com dor no lado medial do pé esquerdo há dois anos, com piora ao andar. Exame físico com testes específicos do tornozelo negativos, sem hematoma ou edema. Nega torção, trauma e cirurgias. A ressonância magnética demonstra osso navicular acessório tipo II e osso navicular, ambos com edema. Estes achados com quadro clínico são compatíveis com síndrome do osso navicular acessório. Este relato demonstra a dificuldade de diagnosticar essa lesão, pois seu o exame físico é inespecífico, podendo simular patologias mais complexas, necessitando de exames complementares para seu correto diagnóstico (AU)

The accessory navicular bone, of which three variants have been described, is often considered as a normal anatomic and roentgenographic variant. Is a congenital anomaly in which the tuberosity of the navicular bone develops from a secondary ossification center and it has an incidence estimated between 2% and 14% with higher incidence in women being bilateral in 50-90% of the cases. Our aim was to report a case and review the literature about this uncommon lesion. We carried out a review of medical records, photographic record of diagnostic method, and review from the literature. A 59 years old woman with pain in the medial side of the left foot for two years. Refers worsening with walking. Physical examination with specific ankle negative tests, without bruise or edema. Denies torsion, trauma and surgeries. Magnetic resonance imaging demonstrates type II accessory navicular bone with edema and navicular bone edema. These findings with clinical complaint are compatible with accessory navicular bone syndrome. This report demonstrates the difficulty of diagnosing this lesion, since its physical examination is non-specific, and it can simulate more complex pathologies, requiring complementary tests for its correct diagnosis (AU)

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.

Ligation bias in illumina next-generation DNA libraries: implications for sequencing ancient genomes.

Ancient DNA extracts consist of a mixture of endogenous molecules and contaminant DNA templates, often originating from environmental microbes. These two populations of templates exhibit different chemical characteristics, with the former showing depurination and cytosine deamination by-products, resulting from post-mortem DNA damage. Such chemical modifications can interfere with the molecular tools used for building second-generation DNA libraries, and limit our ability to fully characterize the true complexity of ancient DNA extracts. In this study, we first use fresh DNA extracts to demonstrate that library preparation based on adapter ligation at AT-overhangs are biased against DNA templates starting with thymine residues, contrarily to blunt-end adapter ligation. We observe the same bias on fresh DNA extracts sheared on Bioruptor, Covaris and nebulizers. This contradicts previous reports suggesting that this bias could originate from the methods used for shearing DNA. This also suggests that AT-overhang adapter ligation efficiency is affected in a sequence-dependent manner and results in an uneven representation of different genomic contexts. We then show how this bias could affect the base composition of ancient DNA libraries prepared following AT-overhang ligation, mainly by limiting the ability to ligate DNA templates starting with thymines and therefore deaminated cytosines. This results in particular nucleotide misincorporation damage patterns, deviating from the signature generally expected for authenticating ancient sequence data. Consequently, we show that models adequate for estimating post-mortem DNA damage levels must be robust to the molecular tools used for building ancient DNA libraries.

Ancient DNA clarifies the evolutionary history of American Late Pleistocene equids.

Hippidions are past members of the equid lineage which appeared in the South American fossil record around 2.5 Ma but then became extinct during the great late Pleistocene megafaunal extinction. According to fossil records and numerous dental, cranial, and postcranial characters, Hippidion and Equus lineages were expected to cluster in two distinct phylogenetic groups that diverged at least 10 MY, long before the emergence of the first Equus. However, the first DNA sequence information retrieved from Hippidion fossils supported a striking different phylogeny, with hippidions nesting inside a paraphyletic group of Equus. This result indicated either that the currently accepted phylogenetic tree of equids was incorrect regarding the timing of the evolutionary split between Hippidion and Equus or that the taxonomic identification of the hippidion fossils used for DNA analysis needed to be reexamined (and attributed to another extinct South American member of the equid lineage). The most likely candidate for the latter explanation is Equus (Amerhippus) neogeus. Here, we show by retrieving new ancient mtDNA sequences that hippidions and Equus (Amerhippus) neogeus were members of two distinct lineages. Furthermore, using a rigorous phylogenetic approach, we demonstrate that while formerly the largest equid from Southern America, Equus (Amerhippus) was just a member of the species Equus caballus. This new data increases the known phenotypic plasticity of horses and consequently casts doubt on the taxonomic validity of the subgenus Equus (Amerhippus).