Abstract
The fossil bacula, or os penis, constitutes a rare subject of study due to its scarcity in the fossil record. In the present paper we describe five bacula attributed to the bear Indarctos arctoides Depéret, 1895 from the Batallones-3 site (Madrid Basin, Spain). Both the length and morphology of this fossil bacula enabled us to make interpretative approaches to a series of ecological and ethological characters of this bear. Thus, we suggest that I. arctoides could have had prolonged periods of intromission and/or maintenance of intromission during the post-ejaculatory intervals, a multi-male mating system and large home range sizes and/or lower population density. Its size might also have helped females to choose from among the available males.
Highlights
Batallones-3 is one of the nine Late Miocene (Late Vallesian) fossil vertebrate localities of the fossiliferous area of Cerro de los Batallones (Madrid Basin, Spain) [1,2,3,4,5]
Almost 98% of the fossil mammal remains identified from Batallones-3 belong to carnivorans
The baculum or os penis is a non-appendicular bone found in the glans tissue, dorsal to the urethra, with its proximal end abutting the distal end of the corpus cavernosum [10,11,12] of members of five orders of mammals [13,14,15]
Summary
Batallones-3 is one of the nine Late Miocene (Late Vallesian) fossil vertebrate localities of the fossiliferous area of Cerro de los Batallones (Madrid Basin, Spain) [1,2,3,4,5]. Among the fossil species we found remains of the primitive bear Indarctos arctoides Deperet, 1895 with a total of 1690 bone elements, belonging to a minimum number of 16 individuals [6]. The bacula of most extant species of Ursidae species are relatively long for their body size.
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