Origination of antlerogenesis

Abstract

Antlers are unique appendages. They are shed and rebuilt at intervals, and are synapomorphic for all living Cervidae (except for the Chinese water deer, Hydropotes inermis, in which they have presumably been lost). The antlerogenic process is controlled by a complex interaction of fluctuating levels of several hormones, most importantly testosterone. The oldest antler remains are recorded from the early Miocene; these have been interpreted as non-deciduous appendages because of supposed permanent skin coverage and the lack of a burr (a well-developed osseous protuberance around the base of the antler, which is always present in extant cervids). The aim of this study is to test the hypothesis that antler shedding was possible in these early Miocene cervids. Antlers of all extant and eight Miocene cervid genera, including burr-less antler fragments of the earliest cervids Procervulus, Ligeromeryx, and Lagomeryx were studied. An extensive comparative morphological analysis of external features of the antler, and of the abscission area and the base of the antler in particular, was undertaken. The results indicate that a regular, porous, and rugose abscission surface at the proximal end of the antler indicates antler shedding in both living and fossil cervids. The antler shedding mechanism must therefore have already been present in all early/mid Miocene cervid genera included in this study. On this basis, it is suggested that the presence of a burr is not prerequisite in order to shed antlers, that the presence of perpetual antlers has not yet been verified, and that the process of shedding and regeneration developed with the first appearance of these organs. This insight is particularly important for the systematic classification of early Miocene species as Cervidae, because the absence of the antler shedding and rebuilding mechanism would exclude them from the taxon Cervidae and from any relationship with extant cervids. J. Morphol. 278:182-202, 2017. © 2016 Wiley Periodicals,Inc.

The systematics of the Cervidae: a total evidence approach

“…Based on evidence from comparative anatomy (Heckeberg, 2017b), the cranial appendages of early Miocene cervids, including lagomerycines, were shed and followed the same principles of the antler cycle as extant cervids and are therefore to be considered as antlers. Even though antlers are species-specific, they have a high variability, intraspecifically and ontogenetically.…”

“…There is broad consensus that antlers originated only once (Loomis, 1928;Azanza & Morales, 1989;Azanza, 1993aAzanza, , 1993bAzanza, DeMiguel & Andrés, 2011;Heckeberg, 2017b). The antlers of most Miocene cervids have a simple bifurcating pattern, sometimes with an additional tine, or are coronate (Azanza, DeMiguel & Andrés, 2011).…”

“…In extant cervids, short and simple antlers and long and more complex or palmated antlers are present. Many extant cervids develop exactly three tines (Heckeberg, 2017b). The three antler morphotypes have previously been associated with ecological habitats: simple antlers for the tropics, a three-tined antler plan for woodland areas typical in East Eurasia or India, and the large and complex display organs in temperate regions (Pitra et al, 2004).…”

“…There is a lot of inter-and intraspecific variation in antlers (Goss, 1983;Heckeberg, 2017b). The high variability of antlers is a problem particularly in fossil taxa, where the entire intraspecific variation cannot always be observed due to the lack of a sufficient number of specimens or the incompleteness of ontogenetic stages.…”

“…Diagnostic characters of cervids include, most importantly, the presence of antlers (Heckeberg, 2017b) and for example the presence of two lacrimal foramina, a lacrimal fossa, a preorbital vacuity and brachyodont dentition ( Fig. 1; , 1988, Bouvrain, Geraads & Jehenne (1989) and Mickoleit (2004)).…”