Balearic Islands Cave Goat-Myotragus balearicus

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Balearic Islands Cave Goat-Myotragus balearicus


A restoration of M. balearicus.

Temporal range: Holocene

Scientific classification:

Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Superphylum: Deuterostomia
Phylum: Chordata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Order: Therapsida
Suborder: Cynodontia
Clade: Prozostrodontia
Clade: Mammaliaformes
Class: Mammalia
Legion: Cladotheria
Sublegion: Zatheria
Infralegion: Tribosphenida
Subclass: Theria
Clade: Eutheria
Infraclass: Placentalia
Subcohort: Exafroplacentalia
Magnorder: Boreoeutheria
Superorder: Laurasiatheria
Clade: Ungulata
(unranked): Cetartiodactyla
Clade: Ruminantiamorpha
Suborder: Ruminantia
Infraorder: Pecora
Family: Bovidae
Subfamily: Caprinae
Genus: †Myotragus
Species: †M. balearicus

The Balearic Islands cave goat (M. balearicus; "Balearian mouse-goat") was a species of caprine that lived on Majorca and Minorca until ~5k years ago.

Early history:
Myotragus (or at least its forebears) likely came from more eastern areas to the Balearic Islands during the Messinian Crisis. When the Zanclean flood occurred at the beginning of the Pliocene, the colonizing animals became trapped in the aforementioned region.[1] Subsequently, marine regression united the islands of Majorca and Minorca together (the latter of which was not colonized by Myotragus until this time). As such, Myotragus was able to immigrate to Minorca.[2] Minorca was inhabited by a particularly large rabbit taxon (Nuralagus rex) at the time.[3] The two animals likely competed, resulting in the giant rabbit being displaced by the mouse goat.[2]

Description:
Myotragus balearicus was quite an unorthodox animal. For one thing, unlike the majority of other herbivorous mammals, it possessed stereoscopic vision as indicated by the nearly forward-facing eyes. Furthermore, the limb elements were foreshortened significantly (the metapodials were more shortened more than in the dwarf hippos and deer). It was ~50 centimeters at the shoulder. There were only two incisors in the mandible and these incisors in particular were akin to those of rodents in that they were shaped like chisels, lacked roots, and continuously grew.[1][4] M. balearicus in particular had no lateral incisors and fourth premolars.[1] One normal feature (for a bovid) that it was in possession of were its (short) horns. There was lamellar-zonal tissue in the cortex of the bones, a feature of ectothermic reptiles. Judging from this fact, Myotragus actually grew less like other mammals and more like crocodilians. Moreover, it adapted to the varying quantity of resources in its environment by adjusting its metabolic requirements and being in some ectotherm-like state.[5]

Phylogeny:
Despite being called a "mouse-goat", Myotragus is "in a position basal to the Ovis group", ie. it was closer to sheep than it was to goats.[6]

Feeding habits:
Myotragus was a browser. Box (Buxus balearica) was one plant species that it consumed in large amounts. Coprolites of Myotragus had a fine texture, probably indicating an efficient digestive system.[7]

Extinction:
Human hunting and other anthropogenic changes in the ecosystem (eg. Baxus balearicus being replaced by Olea europaea at about the same time humans arrived in the Balearic Islands) likely contributed to the mouse-goat's disappearance.[8][9] The first human settlers of the Balearic Islands brought domesticated animals with them. It's very likely Myotragus would have competed with these domestic animals (likewise, humans would have cleared the forests Myotragus relied on for their livestock), further contributing to extinction. Domestic animals preying upon the mouse-goat could have included dogs and those competing with it would likely have included cattle, pigs, and ironically, sheep and goats.[9]


A mounted skeleton of M. balearicus.

References:

[1] Jordi Agusti & Mauricio Antón (2002). Mammoths, Sabertooths, and Hominids: 65 Million Years of Mammalian Evolution in Europe. pp. 262.
[2] "Three islands, three worlds: Paleogeography and evolution of the vertebrate fauna from the Balearic Islands" (Bover et al., 2008).
[3] "Nuralagus rex, gen. et. sp. nov., an endemic insular giant rabbit from the Neogene of Minorca (Balearic Islands, Spain)" (Quintana et al., 2011).
[4] Edited by Scott Elias & Cary Mock (2013). Encyclopedia of Quaternary Science.
[5] "Physiological and life history strategies of a fossil large mammal in a resource-limited environment" (Köhler & Moyà-Solà, 2009).
[6] "Molecular dating of caprines using ancient DNA sequences of Myotragus balearicus, an extinct endemic Balearic mammal" (Lalueza-Fox et al., 2005).
[7] "The diet of Myotragus balearicus Bate 1909 (Artiodactyla: Caprinae), an extinct bovid from the Balearic Islands: evidence from coprolites" (Alcover et al., 1999).
[8] Alexandra van der Geer, George Lyras, John de Vos, & Michael Dermitzakis (2011). Evolution of Island Mammals: Adaptation and Extinction of Placental Mammals on Islands. pp. 136.
[9] www.world-archaeology.com/features/myotragus-balearicus-extinction-of-mouse-goats.htm

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Extinct goat was cold-blooded

An extinct goat that lived on a barren Mediterranean island survived for millions of years by reducing in size and by becoming cold-blooded, which has never before been discovered in mammals. The goat, Myotragus balearicus, lived on what is now Majorca, a Spanish island. The island had scarce resources, and there was no way for the goats to leave, and so scientists wondered how they had thrived for so long. A recently published research paper reveals the extinct goat survived by adjusting its growth rate and metabolism to suit the available food, becoming cold-blooded like reptiles. Paleontologists studying fossilized Myotragus bones compared them to bones of reptiles living in the same region at the same time, and found surprising similarities. The bones of warm-blooded animals show uninterrupted fast growth, while the bones of cold-blooded animals have parallel growth lines showing interrupted growth corresponding to growth cycles, rather like the rings seen in tree trunks. Growth and metabolism rates are adjusted to suit the amount of food available, whereas warm-blooded animals require food to be available continuously. The Myotragus bones showed the same interrupted growth as reptiles. Myotragus are the first mammals ever known to have achieved the same flexibility, and hence survivability, as reptiles. They also saved energy by having a brain half the size of hoofed mammals its own size, and its eyes were only a third of the size. The adult goats stood around 18 inches (45 cm) high, and the kids were around the size of a large rat. Reaching adulthood would have taken many years. Paleobiologist Meike Kohler of the Autonomous University of Barcelona, said the goats would have moved slowly to conserve energy, and probably spent a lot of time lying around basking in the sun. The postcranial skeleton suggested the goat could not jump, run or move fast, which made it easy prey. Myotragus survived on the island as dwarf cold-blooded animals for millenia because they had no natural enemies, but they could not survive the predation of humans when they arrived on the island about 3,000 years ago. In total, the species inhabited the island for over five million years.

phys.org/news177755291.html

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Corroborating what was said about Myotragus and Nuralagus in the OP.

A faunal turnover occurred in Menorca during the Late Pliocene or Early Pleistocene. To date, the Menorca giant rabbit fauna have not been recorded in Pleistocene deposits, suggesting that this fauna disappeared from this island before then. In Menorcan Pleistocene and Holocene deposits only the Myotragus fauna is recorded. The arrival of this fauna to Menorca could be related to the beginning of the glaciations and the related melting of Mallorca and Menorca (e.g., Cuerda, 1975).

digital.csic.es/bitstream/10261/85878/4/Bover%20et%20al%202008%20Last%20version.pdf

Or it could be the sudden arrival of a non-native species that has the same specialism as you but does it a bit better. If that happens, you will lose some, if not all, of your habitat to the interloper. As we saw earlier in the book, this is what happened to Nuralagus rex, a giant lagomorph that was the only grazer and browser on Minorca when Myotragus balearicus, another grazing and browsing mammal, arrived via a temporary land bridge from neighboring Majorca and proceeded to out-graze and out-browse N. rex to extinction. Nuralagus rex might have survived if there had been a few areas on Minorca that Myotragus balearicus couldn't reach, or couldn't thrive on so well for whatever reason, but if there were any such areas, they weren't extensive enough to support a sustainable N. rex population.

www.google.com/books/edition/The_Way_of_the_Hare/VzAqDwAAQBAJ?hl=en&gbpv=1&dq=nuralagus+extinction&pg=PA189&printsec=frontcover