Hypnomys Temporal range: | |
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H. morpheus | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Rodentia |
Family: | Gliridae |
Subfamily: | Leithiinae |
Genus: | † Hypnomys Bate, 1918 |
Type species | |
†Hypnomys mahonensis Bate, 1918 | |
Species | |
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Hypnomys, otherwise known as Balearic giant dormice, is an extinct genus of dormouse (Gliridae) in the subfamily Leithiinae. [1] Its species are considered examples of insular gigantism. [2] They were endemic to the Balearic Islands in the western Mediterranean from the Early Pliocene until their extinction around the 3rd millennium BC. They first appeared in the fossil record on Mallorca during the Early Pliocene (around 5 million years ago), presumably as a result to the evaporation of the Mediterranean sea during the Messinian salinity crisis (5.96-5.33 million years ago) connecting the Balearic Islands with mainland Europe. They later spread to Menorca, and a possible molar is also known from Ibiza. [3] Hypnomys became extinct during the late Holocene (around 4500-4000 years ago) likely shortly after human arrival on the Balearics. They were one of only three native land mammals to the islands at the time of human arrival, alongside the shrew Nesiotites and goat-antelope Myotragus .
The first remains of Hypnomys were discovered in 1910 on the island of Mallorca in the Balearic Islands by British palaeontologist Dorothea Bate, with remains also found by Bate on Menorca a year later. [4] Upon first examination, Bate considered the fossils to represent those of Eliomys or Leithia , but in 1918 described the remains into the new genus Hypnomys, describing two species, H. morpheus on Mallorca, and H. mahonensis on Menorca. [5]
Mitochondrial DNA from H. morpheus indicates that Hypnomys is a member of the subfamily Leithiinae, and closely related to the genus Eliomys, which contains (among others) the European garden dormouse (Eliomys quercinus). The divergence estimated by molecular clock between modern species of Eliomys and Hypnomys in a 2019 study was 13.67 million years ago. [6]
Cladogram of dormice showing the placement of Hypnomys after Bover et al. 2020 [6] and Petrova et al. 2024. [7]
Gliridae (dormice) |
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The ancestor of Hypnomys is often assumed to be the prehistoric Eliomys species E. truci, known from the latest Miocene of the Iberian Peninsula. [3] However, the molar complexity of the earliest dormice remains on Mallorca (presumably ancestral to Hypnomys) and the deep divergence between modern Eliomys and Hypnomys has led to suggestions that Hypnomys descended from a now extinct dormouse genus, possibly Vasseuromys or a closely related form. [6]
Hypnomys likely arrived in Mallorca during the Messinian salinity crisis (5.96–5.3 million years ago), an event when the Strait of Gibraltar closed and the Mediterranean evaporated, with the resulting sea level drop causing the exposure of the continental shelf, allowing dispersal from the Iberian Peninsula to the Balearic Islands, before the islands again became isolated following the reopening of the Straits of Gibraltar and the resulting Zanclean flood which refilled the Mediterranean approximately 5.3 million years ago, at the beginning of the Pliocene. [8] Following this, the Balearic Islands were extremely remote, with no examples of terrestrial vertebrates arriving from the mainland in Mallorca and Menorca until human arrival during the late Holocene, allowing evolution to occur in long-term isolation. [9] Although during the Early Pliocene some other mammals like hamsters and murids were present, by the Late Pliocene, Hypnomys represented one of three mammals present in Mallorca, alongside the goat-antelope Myotragus and the shrew Nesiotites . Hypnomys, Myotragus and Nesiotites dispersed from Mallorca to Menorca during the Pliocene-Pleistocene transition as part of a faunal turnover event replacing the fauna of Menorca, which had previously differed from Mallorca (containing species such as the giant rabbit Nuralagus rex), likely due to the islands being connected during episodes of low sea level as a result of Pleistocene glaciation. [8] [3] A tooth possibly belonging to Hypnomys is known from the Cova de ca na Reia site on Ibiza (Eivissa), of an uncertain Plio-Pleistocene age; however the assignment to Hypnomys is not definitive. [3]
Hypnomys is divided into a number of species, spanning from the Pliocene to the Holocene. These are largely considered to be chronospecies (i.e. to have sequentially evolved from the previous species). As with many extinct mammal species, they are largely distinguished by dental anatomy. [3]
Indeterminate remains of Hypnomys not assigned to species extend back to the Early Pliocene on Mallorca. [8]
The species Hypnomys gollcheri de Bruijn, 1966 from the Pleistocene of Malta has been assigned to the separate genus Maltamys. [3]
Although Hypnomys was considered a subgenus of Eliomys by Zammit Maempel and de Bruijn, 1982 [10] it has generally been considered distinct by other authors. [3]
The Late Pleistocene-Holocene Menorcan H. mahonesis is distinguished from H. morpheus by its simpler teeth morphology and generally larger body size, although the body size of H. morpheus varied substantially over the course of the glacial cycles, at times reaching sizes typical for H. mahonesis. [3] [11]
The overall body size of Hypnomys is considerably larger than mainland dormice species, with the overall body size of the lineage gradually increasing over time. An articulated specimen of Hypnomys cf. onicensis measured in a 2010 study had a head and body length of around 15 centimetres (5.9 in) and a tail length of around 10 centimetres (3.9 in). A specimen of H. morpheus measured in the same study was found to have a head and body length of about 18 centimetres (7.1 in) and a tail length of about 11.5 centimetres (4.5 in). The tail lengths are proportionally shorter than in species of Eliomys. The specimen of H. morpheus was estimated to weigh between 173 and 284 grams (0.381 and 0.626 lb). [1] In comparison to species of Eliomys, the skull and mandibles of Hypnomys species are substantially more robust. The robustness of the mandibles and zygomatic arches of the skull indicate the presence of well developed masseter muscles. [12] The limbs are also robust, with elongated zygopodiums (part of the limbs between the foot and elbow/knee) on both hind and forelimbs. [1]
A 2016 bone histology study found that H. onicensis could live over 10 years, an exceptionally long lifespan in comparison to living Eliomys, which can only live up to 5 years. Young juveniles were found to be already substantially larger than equivalently aged Eliomys individuals. Sexual maturity was also likely delayed in comparison to living Eliomys. [13] In a dental microwear study of H. morpheus the high number of fine scratches on the teeth suggests that the species was more omnivorous than the garden dormouse (which is heavily carnivorous), with the presence of pits on the teeth indicating the intake of hard food such as nuts and seeds, or grit, [14] An analysis of the morphology of the lower jaw suggests that was probably efficient at gnawing and chewing. [15] The lifestyle of Hypnomys has been debated. A 2010 study concluded that H. morpheus was more terrestrial than living dormice, based on morphological comparison of the bone proportions. [1] However, a 2014 study disputed this, finding based on the proportions of the limb bones that H. morpheus was likely arboreal, and possibly also had fossorial (digging) capabilities. [16] While the Balearic Islands lacked large terrestrial predators, Hypnomys was hunted by birds of prey such as owls which are known to have inhabited the islands. [16]
Like the two other endemic mammal genera on the Balearic islands, the shrew Nesiotites and the goat-antelope Myotragus, Hypnomys likely rapidly became extinct after human arrival in the Balearic islands during the mid-late 3rd millennium BC. The youngest current radiocarbon dates for H. morpheus are a few thousand years prior to human arrival, but later dates much closer to human arrival for Nesiotites and Myotragus suggest that it was also present at the time of arrival. [9] Direct predation by humans is an unlikely cause of extinction for Hypnomys. Predators currently present on the Balearic Islands such as cats, weasels, martins and genets were introduced to the islands long after the extinction of the endemic mammals, and there is no compelling evidence for the early presence of dogs. The garden dormouse (Eliomys quercinus) and wood mouse (Apodemus sylvaticus) were early introductions to the islands and may have competed with Hypnomys, though there is no concrete evidence that their existences overlapped. Diseases spread by introduced species may have contributed to the extinction. [17]
A dormouse is a rodent of the family Gliridae. Dormice are nocturnal animals found in Africa, Asia, and Europe. They are named for their long, dormant hibernation period of six months or longer.
Glis is a genus of rodent that contains two extant species, both known as edible dormice or fat dormice: the European edible dormouse (Glis glis) and the Iranian edible dormouse. It also contains a number of fossil species.
Myotragus is an extinct genus of goat-antelope in the tribe Caprini which lived on the Balearic Islands of Mallorca and Menorca in the western Mediterranean until its extinction around 4,500 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 evaporation of the Mediterranean Sea during the Messinian Salinity Crisis.
The Ibiza rail is a recently discovered fossil species of rail, described from a late Pleistocene to Holocene cave deposit at Es Pouàs, on the island of Ibiza. Ibiza is in the Pityuses group of the Spanish Balearic Islands in the Mediterranean Sea. The Ibiza rail was a relative of the extant water rail and may be derived from it, but was a bit smaller and stouter, had shorter and more robust hind limbs and shorter wings, with probably reduced its flight capability. Consequently, it might have also occurred on neighbouring Formentera, where no possible locations have been surveyed.
Nuralagus is an extinct genus of leporid, with a single species, Nuralagus rex, described in 2011. It lived on Menorca, one of the Balearic Islands in the western Mediterranean during the Pliocene epoch. It is the largest known lagomorph to have ever existed, with an estimated weight of 8–12 kilograms (18–26 lb), nearly double the weight of the average Flemish Giant rabbit. It likely went extinct at the Pliocene-Pleistocene transition when Mallorca and Menorca were united as one island, letting the mammalian fauna of Mallorca, including the goat-like ungulate Myotragus, colonize Nuralagus's habitat.
Eliomys is a genus of Palaearctic rodents in the family Gliridae, commonly known as garden dormice.
Leithiinae is a subfamily of dormice. It is named after the Leithia, an extinct genus of giant dormouse from the Pleistocene of Sicily.
Nectogalini is a tribe of Old World water shrews within the family Soricidae. As of late 2007, it consisted of six extant genera and 25 species, with some of the latter being further divided into subspecies. Some, but not all members of the tribe are semiaquatic.
Asoriculus is an extinct genus of terrestrial shrews in the subfamily Soricinae and tribe Nectogalini, native to Europe and North Africa, from the Late Miocene until the late Holocene. The genus is closely related and possibly ancestral to the also recently-extinct Balearic shrews (Nesiotites), with their closest living relative being the Himalayan shrew.
The Balearic Islands are an archipelago in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula. The archipelago forms a province and autonomous community of Spain, with Palma de Mallorca being its capital and largest city.
Pterodromoides is an extinct genus of fulmarine petrel dating from the Late Miocene. It contains a single species, P. minoricensis. Its fossil remains were first discovered at the Punta Nati palaeontological site on the island of Menorca in the Balearic archipelago of the western Mediterranean. An additional specimen from North Carolina, USA has also been referred to this species, suggesting it lived across the North Atlantic. It was described in 2001, with the authors justifying the creation of a new genus by the large orbitonasal opening and characters of the postcranial skeleton, despite the similarity of the cranial osteology to that of Pagodroma.
Leithia is an extinct genus of giant dormice from the Pleistocene of the Mediterranean islands of Malta and Sicily. It is considered an example of island gigantism. Leithia melitensis is the largest known species of dormouse, living or extinct, being twice the size of any other known species.
Rhagamys is an extinct genus of rodents in the subfamily Murinae, the Old World mice and rats. The genus was established by the Swiss zoologist Charles Immanuel Forsyth Major to accommodate Rhagamys orthodon, which is the only species in the genus. It was endemic to the Mediterranean islands of Corsica and Sardinia, descending from Rhagapodemus, which had colonised the islands around 3.6 million years ago. Its closest living relatives are of the genus Apodemus, which includes the field and wood mice.
Nesiotites is an extinct genus of large red-toothed shrews belonging to the tribe Nectogalini that inhabited the Balearic Islands from the latest Miocene/Early Pliocene up until the arrival of humans on the islands during the late Holocene. It was present on Mallorca and Menorca. It represented one of only 3 native land mammals to the islands at the time of human arrival, alongside the goat-antelope Myotragus and the giant dormouse Hypnomys. The genus is closely related to the also recently extinct Corsican-Sardinian shrews belonging to the genus Asoriculus, with their closest living relative being the Himalayan shrew.
Talpa tyrrhenica, also known as the Tyrrhenian mole, is an extinct species of mole belonging to the genus Talpa. It was endemic to the Mediterranean islands of Corsica and Sardinia during the Pleistocene epoch.
Soriculus is a genus of shrew native to Asia. Along with several fossil species, the only extant member of the genus is the Himalayan shrew, as other extant species have now been transferred to other genera.
Enhydrictis is a genus of extinct mustelid, belonging to the subfamily Galictinae. The type species, and best known, is Enhydrictis galictoides from the Pleistocene of Sardinia and Corsica. Some authors attribute species from mainland Eurasia to the genus, but this is disputed, with others considering the genus endemic to Sardinia-Corsica.
Titanochelon is an extinct genus of giant tortoises known from the Early Miocene to the beginning of the Pleistocene in Europe, extending from the Iberian Peninsula to Anatolia. Some members of the genus were larger than extant giant tortoises, with a shell length of up to 2 m.