FIRST PRELIMINARY PALEOHISTOLOGICAL AND HISTOTAPHONOMIC STUDY OF BONE REMAINS FROM RANCHO LA BREA (LATE PLEISTOCENE, USA)

GARRONE, MARIANA C.; MARIN-MONFORT, MARÍA DOLORES; TOMASSINI, RODRIGO L.; PESQUERO, MARÍA DOLORES; CERDA, IGNACIO A.; PRADO, JOSÉ L.; MONTALVO, CLAUDIA I.; FERNÁNDEZ-JALVO, YOLANDA; ALBERDI, MARÍA TERESA

Virtual

Congreso; 3er Paleontological Virtual Congress; 2021

The asphalt deposits of Rancho La Brea (California, USA) are well known for the quantity and variety of its Late Pleistocene fossil record. However, there is little information regarding the taphonomy of vertebrate, and particularly the histology of the bone remains. This work investigates for the first time pre and post-mortem changes based on the bone microstructure features (combining osteohistological and histotaphonomic evidences) of Equus occidentalis recovered from different tar pits. Thin sections of femora, humeri and metapodials were assessed using petrographic and scanning electron microscope. All the samples are mainly constituted by fibrolamellar tissue, which reflects a relatively fast rate of bone deposition during the early stages of the growth. Some samples display an external fundamental system evidencing a decrease in the growth rate. Secondary remodelling is present with different intensity and location in all skeletal elements. Although the samples exhibit some taphonomical alterations (i.e. enlargement of canaliculi, microtunelling, microcracks, fissures and cavities infilling), the histological preservation is nevertheless excellent. No evidence of microorganisms attack altering the original histology was identified; this absence is possibly linked to this type of extreme environmental context which require specialized adaptations and, therefore, limits the microbial development. From a paleohistology viewpoint, the distribution and characterization of bone tissues and remodelling in the different skeletal elements are, in general lines, similar to that other extant and extinct equids. From a histotaphonomic viewpoint, the variations recorded indicate evidence of different taphonomic histories and preservation conditions among pits, which may be related to seasonal periods.