Haploidoceros mediterraneus
Taxonomy
Haploidoceros mediterraneus is a new species described in 2008, belonging to the family Cervidae. The original material of the species was initially assigned to Euctenoceros mediterraneus, however upon further examination it did not share much affinity with other members of this genus and thus was designated with the unique genus ‘Haploidoceros’ of which so far only the species ‘mediterraneus’ has been described (1). The etymology of the binomial name is a conjugate of ‘Haploides’ – of simple shape and ‘ceros’ – horn; and ‘mediterraneus’ which signifies the geographic distribution of the species (1).
The phylogenetic placement of Haploidoceros is within the subfamily Cervinae (2) a group of cervids that includes the Red Deer (Cervus elaphus), Fallow Deer (Dama dama), Muntjacs (Muntiacus spp.), and others (4). Within Cervinae the relationships become much more tentative. Antler morphology would indicate that Haploidoceros is most closely related to the genera Rucervus and Arvernoceros, the former is a once widespread genus now limited to a single South-Asian species, the barasingha (Rucervus duvaucelli), and the latter is an extinct genus from the Pliocene-Early Pleistocene of Europe (2).
Distribution and Age
Remains of Haploidoceros mediterraneus are scarce, restricted to only five known sites. This could indicate that it was a relatively rare species, additionally, the scarcity may be attributable to the difficulty in distinguishing post-cranial remains from other members of Cervidae based (6). The type specimen originates from a site located near the French city of Montpellier (1). Additional sites are known from southern France (1), Spain (6, 7), and Portugal (3). The fossil locations indicate endemism to South-Western Europe, this can be explained by Haploidoceros being a part of the temperate fauna of Europe, which was largely restricted to the South of the continent during glacial periods (6). A question arises, why during warm periods the range of Haploidoceros didn’t expand further north-east? The climate at least would not hinder this. It’s possible Haploidoceros did expand during these periods and were wiped out again in subsequent glaciations, It is hard to evaluate with the limited fossil record available.
The earliest remains of Haploidoceros mediterraneus are from the middle Pleistocene, with the oldest dated to about 390-440kya (3). All but a single site dated to the middle Pleistocene, the notable exception was a Late Pleistocene site with an age of 90kya (6). Due to the low number of fossil localities, its difficult to determine the true temporal range of this species. A possible extinction date could be around 40,000-50,000 years ago when most of the European temperate megafauna went extinct, but until more remains are discovered this is pure conjecture. The origin of Haploidoceros is equally difficult to determine, though fragmented fossils from the Early Pleistocene could belong to an ancestor (6) suggesting a tentative Early or Middle Pleistocene beginning.
Fig 1. Known Fossil sites of Haploidoceros mediterraneus as well as the estimated modern natural range based on Phylacine Data (8) and habitat samples within range
Morphology and Ecology
Haploidoceros is a small-medium-sized deer weighing an estimated 70-80kg (Croitor et al 2018). The morphology of the species is similar to that of most members of cervinae, this is especially true of the post-cranial skeleton. Nevertheless, some features do distinguish it from other species. Most notably are the bizarre-looking antlers, each one was split into two beams adorned only with a single tip at the end. The posterior beam was up to a meter long and curved into a sickle shape, the front beam was comparatively shorter and straighter (2). The orbit of the animal protrudes sideways, similarly to in Reindeer (Rangifer tarandus), it’s not clear what this adaptation is for. One suggestion is that it is to prevent the eyes from getting covered with long hair present on the neck or head (2). Considering the orbit elongation doesn’t occur in juveniles this could be a sexual trait such as a mane, possibly exclusive to the males (2). The body is fairly typical of a cervid, though the hind limbs are well developed for jumping indicating it may have had a bounding run (1).
Haploidoceros mediterraneus was a strictly temperate species, judging by its distribution. The habitats in which it has been found ranged from montane forest to semi-open woodland (5). The species is found alongside a rich abundance of megafauna which includes several species of equids, caprines, rhinoceroses, and cervids, additionally, the wild boar (Sus scrofa), aurochs (Bos primigenius), and straight-tusked elephant (Palaeoloxodon antiquus) are also commonly found in association with Haploidoceros (1, 6). Potential predators of Haploidoceros found at the same site include the cave lion (Panthera (leo) spelaea), grey wolf (Canis lupus), cave hyena (Crocouta (crocuta) spelaea), Hyaena prisca, brown bear (Ursus arctos) (1), Homo heidelbergensis and Homo neanderthalensis (3).
The fallow deer (Dama dama) is conspicuously absent in sites containing Haploidoceros mediterraneus despite having overlapping ranges (5). Likely their niches were too similar and were competitive exclusive. The division appears to have been along habitat lines, Haploidoceros inhabiting the woody regions of South-Western Europe and fallow deer the open regions. Supporting this idea are the dietary adaptations of Haploidoceros. It possessed big cheek teeth which is indicative of a grazing diet, yet had pre-maxillary bones which were narrow and sharp suggesting browsing, the morphology tentatively supports a mixed feeder (2). A study on the wear of the teeth of Haploidoceros reaffirms the species as a mixed feeder but further concludes Haploidoceros had a preference for browsing on leaves with grazing playing a supplementary role. This diet appears to have been more similar to the fallow deer than any other cervid (5).
Fig 2. The cranium of Haploidoceros mediterraneus. The areas in white are preserved and scaled to lectotype, the areas in grey speculative. Skeletal by August Helmke, used with permission.
References
1. Croitor, R., Bonifay, M.-F., Brugal, J.-P.. (2008). Systematic revision of the endemic deer Haploidoceros n. gen. mediterraneus (Bonifay, 1967) (Mammalia, Cervidae) from the middle Pleistocene of Southern France. Paläontol. Z. 82 (3), 325–346.
2. Croitor, R., Sanz, M., Daura, J.. (2018). The endemic deer Haploidoceros mediterraneus (Bonifay) (Cervidae, Mammalia) from the Late Pleistocene of Cova del Rinoceront (Iberian Peninsula): origin, ecomorphology, and paleobiology. Hist. Biol. 19
3. Croitor, R., Sanz, M., Daura, J.. (2019). Deer remains from the Middle Pleistocene site of Gruta da Aroeira (Portugal): Iberian faunal endemism and implications for hominin paleobiogeography. Quarternary Science Reviews 225, 106022.
4. Gilbert, C., Ropiquet, A., Hassanin, A.. (2006). Mitochondrial and nuclear phylogenies of Cervidae (Mammalia, Ruminantia): Systematics, morphology, and biogeography. Molecular Phylogenies and Evolution 40, 101-117.
5. Rivals, F., Sanz, M., Daura, J.. (2016). First reconstruction of the dietary traits of the Mediterranean deer (Haploidoceros mediterraneus) from the Cova del Rinoceront (NE Iberian Peninsula). Palaeogeogr. Palaeoclimatol. Palaeoecol. 449, 101e107.
6. Sanz, M., Daura, J., Brugal, J-P.. (2014). First occurrence of the extinct deer Haploidoceros in the Iberian Peninsula in the Upper Pleistocene of the Cova del Rinoceront (Castelldefels, Barcelona). C. R. Palevol 13, 27-40.
7. Van der Made, J., Mazo, A.. (2014-2015). Los grandes mamíferos del yacimiento de PRERESA, Haploidoceros mediterraneus. Una nueva especie de ciervo en el Pleistoceno Ibérico. Museo Arqueológico Regional, Alcalá de Henares, pp. 39–53.
8. Faurby, S., Pedersen, R. Ø., Davis, M., Schowanek, S. D., Jarvie, S., Antonelli, A., & Svenning, J.C. (2020). PHYLACINE 1.2.1: An update to the Phylogenetic Atlas of Mammal Macroecology. doi:10.5281/zenodo.3690867