Abstract
The abundance of skeletal remains of cave bears in Pleistocene deposits can offer crucial information on the biology and life history of this megafaunal element. The histological study of 62 femora from 23 different European localities and comparisons with specimens of five extant ursid species revealed novel data on tissue types and growth patterns. Cave bear’s femoral bone microstructure is characterized by a fibrolamellar complex with increasing amounts of parallel-fibered and lamellar bone towards the outer cortex. Remodelling of the primary bone tissue initially occurs close to the perimedullary margin of the bone cortex around the linea aspera. Although similar histological traits can be observed in many extant bear species, the composition of the fibrolamellar complex can vary greatly. Cave bears reached skeletal maturity between the ages of 10 and 14, which is late compared to other bear species. There is a significant correlation between altitude and growth, which reflects the different body sizes of cave bears from different altitudes.
Highlights
During the Pleistocene, Eurasia was home to many large sized mammals, commonly referred to as megafauna [1, 2]
The hypothesized ancestral species of cave bears, U. deningeri is according to some authors, directly on the evolutionary line of U. spelaeus and, the anagenetic ancestor of the latter [3, 7]
We aim to study several aspects of the bone histology of cave bears: (1) we describe the general histology of the femora of cave bears compared to extant relatives, (2) we aim to reconstruct growth of cave bears by using average inter-LAG distance (AILD) as a proxy and compare it to extant relatives, (3) we present a hypothesis on some life history variables for cave bears based on the investigated growth, and (4) we examine the intraspecific variation in growth in the context of the altitude of the excavation site in order to elucidate if the investigated growth is different in the smaller cave bear populations from high altitudes
Summary
During the Pleistocene, Eurasia was home to many large sized mammals, commonly referred to as megafauna [1, 2]. Among them are cave bears, Ursus spelaeus, one of the most commonly found species, recovered in numerous Eurasian localities ranging from Spain to Russia [3, 4]. Some authors suggest giving species and subspecies status to some of those [8, 13] but it remains unclear if species status can be assigned to those cave bear haplotypes [4]. As this discussion is not completely resolved yet, we use U. spelaeus sensu lato, including U. ingressus, U. s.
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