User:Hemiauchenia/sandboxMyotragus

Myotragus (Neo-Latin, derived from the Greek: μῦς, τράγος and Βαλεαρίδες "Balearian mouse-goat"), also known as the Balearic Islands cave goat, is an extinct genus of the subfamily Caprinae which lived on the Balearic Islands of Mallorca and Menorca in the western Mediterranean until its extinction around 5,000 years ago. The fossil record of Myotragus on the Balearic Islands extends over 5 million years back to the early Pliocene on Mallorca, where it presumably arrived after the major sea level drop during the Messinian Salinity Crisis. Myotragus is represented by a sequence of six chronospecies representing a gradual change in morphology''. M. balearicus'' is noted for a number of unusual morphological adaptions, including forward facing eyes suggestive of binocular vision. Early genetic research suggested that it was closely related to sheep of the genus Ovis, however more recent research has indicated that its closest living relative is the takin (Budorcas taxicolor). The final species Myotragus balearicus became extinct when humans arrived in the Balearic Islands around 3000 BC.

History of Discovery
The first remains of Myotragus were described by Dorothea Bate in 1909. Bate had been sent a letter by Robert Ashington Bullen, who informed her about a bone-bearing breccia deposit on the east of Mallorca, which prompted her to survey the island for Pleistocene aged cave deposits. Three such deposits were found, which yielded fragmentary remains of Myotragus, including a mostly complete skull, associated with a mandible and atlas vertebra, which was designated the type specimen of the new species and genus Myotragus balearicus. In 1915, Charles William Andrews described more material discovered in the intervening years, including material that had been discovered on Menorca.

Description
Its eyes were not directed towards the sides, as are those of nearly all the herbivorous mammals, but towards the front like nearly all primates and carnivorans, granting them stereoscopic vision. The lower jaw contained two perennial-growth incisors, like rodents and lagomorphs, but not other ungulates. The lower jaw usually lacked other incisors, though some jaws have been found with vestigial second incisors. The upper jaw lacked incisors. The rest of its teeth were molars and premolars adapted to the crushing of vegetal matter. The nose was short in comparison with the rest of the skull, similar to the noses of rabbits and hares. Finally, both sexes had at the top of the head two very short horns. It is possible these horns were longer, having short bone-bases and long horn-covers, but no complete horns have been found.

Myotragus balearicus was quite small in size (standing about 50 cm at the shoulder) and weighed between 50 and 70 kg. The legs were proportionately shorter than those of other related bovids, and less flexible, which did not make Myotragus balearicus exceptionally fast. This was not a serious problem because on the islands there were no predators except for some birds of prey, from which they probably hid in the vegetation. On the shoulders they had a pronounced hump, while the back was bent in the hindquarters. The legs, like many from the order Artiodactyla, had four fingers of which only two were used to walk. The tail was rather long in comparison to the rest of the body.

Chronology
The earliest species of Myotragus is Myotragus palomboi from Mallorca, dating to the Miocene-Pliocene boundary, around 5.3 million years ago. All species of Myotragus are believed to represent a single lineage that changed through time, and thus each of the recognised species is a chronospecies. The chronospecies of Myotragus show progressive changes, including size reduction (dwarfing), reduction in the length of the limb bones and reduction of the number of teeth. The teeth of the earliest species had three incisors and one canine, M. balearicus has only a single ever growing incisor in each jaw, alongside a single premolar (P4) in the lower jaw and two in the upper jaw (P3, P4).

Diet
Evidence from preserved coprolites of M. balearicus indicates that it was likely a browser, and heavily dependent on the native boxwood species Buxus balearica for a large part of its diet. The smooth texture of the coprolites indicates that the digestion was likely highly efficient.

Physiology and growth
The bone histology of Myotragus shows lamellar-zonal tissue throughout the cortex, a feature otherwise typical of ectothermic reptiles. The growth of bones in Myotragus is unlike any other mammal and similar to crocodilians in showing slow and adaptive rates, intermittently ceasing growth altogether, and reaching somatic maturity by about 12 years. This pattern of growth indicates that Myotragus, in the same way as extant reptiles, adapted its metabolism to changing food and water availability, and ambient temperatures.

Domestication
In 1969 it was suggested that Myotragus shows signs of domestication but this is now disputed.

Relationships
The unique characteristics of Myotragus balearicus are a consequence of a prolonged process of evolution on the islands (a clear example of island dwarfing). In this type of isolation, the ungulates tend to become smaller while rodents and lagomorphs increase their size, as happened to the Hypnomys, the giant dormouse that shared a habitat with Myotragus. Such species also tend to lose their fear reaction towards predators if none occur on the islands. A clear example of this is the loss of the capacity to run at high speed, the development of stereoscopic vision (which is useful to calculate distances, but not so to watch for predators) and the proportional reduction of the brain.

The analyses of DNA and the oldest fossils (Pliocene 5.7 million years ago) of the island of Majorca (Myotragus pepgonellae) indicate that Myotragus balearicus, in spite of being a browsing animal, descended originally from grazers. The closest related species to Myotragus are ovine, such as the extinct Nesogoral of the Plio-Pleistocene of Sardinia, the old Gallogoral of France (possible mainland ancestor of both Myotragus and Nesogoral), Ovis (present sheep and mouflon) and the mountain goats of Central Asia. The last ancestor common to Myotragus and Nesogoral arrived at Majorca and Sardinia around 6 million years ago, a time at which the Straits of Gibraltar were closed and the Mediterranean Sea was a small collection of salty lakes. Later on, the opening of the straits and the massive salt water inflow isolated the animal populations, which diversified in the new Mediterranean islands created by tectonic forces. At the same time, climatic change replaced the vegetation of subtropical type with the present one of Mediterranean type, forcing Myotragus to develop drastic changes in its feeding and set of teeth. An analysis of complete mitochondrial genomes found that its closest living relative is the takin (Budorcas taxicolor) with an estimated divergence around 7.1 Mya.

Strangely, Myotragus initially only colonized the island of Majorca. On Ibiza a strange ecosystem without terrestrial mammals developed in which birds and bats were the main vertebrates, while in Menorca a giant rabbit evolved that covered the same niche as Myotragus in Majorca. With the level of the sea falling in the glacial era, Majorca and Menorca were united and Myotragus replaced the great Menorcan lagomorphs. Both islands separated again at the beginning of the Holocene.

Extinction
Diverse datings indicate that the three native terrestrial mammals of Majorca (Myotragus, Hypnomys and the giant shrew Asoriculus) disappeared all in the same very short period of time, during the third millennium BC.

During years of continued discussion between scientists, some said the extinction was caused by climate change, while others maintained they were exterminated by the first human settlers of the Balearic Islands. Various evidence could support both opinions; as a result, this question is still not answered unequivocally.

The dominant theory is the one that postulates an extinction by human causes. Traditional methods had dated the first human colonization of the Balearic Islands towards 5000 BC or even before, but subsequent tests with modern methods of dating clearly indicate that there was no human presence before 3000 BC. This date agrees very closely with the fast decline of the three forms.

The first Balearic settlers had a Neolithic culture, although they continued living in caves, which are plentiful on the islands. In these have been found numerous animal bones, especially those of Myotragus, with evidence of carving and denting by humans. Most surprising is that not all Myotragus arrived dead at the caves, but seem to have been kept alive for some time there. Many had their horns trimmed, which healed later. This may mean that their captors were attempting to domesticate them. Domestication ultimately did not succeed, probably because Myotragus would not reproduce in captivity or not at a suitable speed, as only remains of adult individuals have been found.

Human hunting, the failure of domestication, the introduction of domestic animals like goats (that competed with Myotragus for the same food), cattle, horses, donkeys, pigs, and sheep (and consequently, the destruction of the forests to create places for them to pasture) and dogs (which could have preyed on Myotragus) were the probable causes for the extinction of this animal.