{{Short description|Extinct genus of giant dormice}} {{Automatic taxobox | fossil_range = {{fossilrange|Early Pliocene|Holocene}} | image = Hypnomys.png | image_caption = ''H. morpheus'' | taxon = Hypnomys | authority = Bate, 1918 | type_species = †'''''Hypnomys mahonensis''''' | type_species_authority = Bate, 1918 | subdivision_ranks = Species | subdivision = *†''H. eliomyoides'' *†''H. morpheus'' *†''H. onicensis'' *†''H. waldreni'' *†''H. mahonensis'' }} '''''Hypnomys''''', otherwise known as '''Balearic giant dormice''', is an extinct genus of dormouse (Gliridae) in the subfamily Leithiinae.<ref name=":3">{{Cite journal|last1=Bover|first1=Pere|last2=Alcover|first2=Josep A.|last3=Michaux|first3=Jacques J.|last4=Hautier|first4=Lionel|last5=Hutterer|first5=Rainer|date=2010-12-31|title=Body Shape and Life Style of the Extinct Balearic Dormouse Hypnomys (Rodentia, Gliridae): New Evidence from the Study of Associated Skeletons|journal=PLOS ONE|volume=5|issue=12|article-number=e15817|doi=10.1371/journal.pone.0015817|issn=1932-6203|pmc=3013122|pmid=21209820|bibcode=2010PLoSO...515817B|doi-access=free}}</ref> Its species are considered examples of insular gigantism.<ref>{{Cite journal|last1=Orlandi-Oliveras|first1=Guillem|last2=Jordana|first2=Xavier|last3=Moncunill-Solé|first3=Blanca|last4=Köhler|first4=Meike|date=2016-01-01|title=Bone histology of the giant fossil dormouse Hypnomys onicensis (Gliridae, Rodentia) from Balearic Islands|journal=Comptes Rendus Palevol|series=Current advances in paleohistology: A tribute to a generation of Frenchpaleohistologists|volume=15|issue=1–2|pages=238–244|doi=10.1016/j.crpv.2015.05.001|doi-access=free|bibcode=2016CRPal..15..238O }}</ref> 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.<ref name=":0">{{Cite journal|last1=Agustí|first1=Jordi|last2=Espresate|first2=Juli|last3=Piñero|first3=Pedro|date=14 December 2020|title=Dental Variation in the Endemic Dormouse Hypnomys Bate 1918 and its Implications for the Palaeogeographic Evolution of the Balearic Islands (Western Mediterranean) during the late Neogene-Quaternary|url=https://www.tandfonline.com/doi/full/10.1080/08912963.2020.1852557|journal=Historical Biology|language=en|volume=33|issue=12|pages=3152–3165|doi=10.1080/08912963.2020.1852557|s2cid=230583559|issn=0891-2963|url-access=subscription}}</ref> ''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''. Their closest living relatives are of the genus ''Eliomys'', including the European garden dormouse (''Eliomys quercinus'').
== History of discovery == 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.<ref name="Bate1914">{{cite journal |last1=Bate |first1=Dorothea |title=On the Pleistocene Ossiferous Deposits of the Balearic |journal=The Geological Magazine |date=1914 |volume=1 |issue=8 |pages=337–345 |doi=10.1017/S001675680013986X |s2cid=128692740 |url=https://www.biodiversitylibrary.org/item/96164#page/443/mode/1up}}</ref> 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.<ref name="Bate1918">{{cite journal|last1=Bate|first1=Dorothea|title=On a new genus of extinct muscardine rodent from the Balearic Islands|url=https://www.biodiversitylibrary.org/page/31566158#page/289/mode/1up|journal=Proceedings of the Zoological Society of London|year=1918 |volume=1918|issue=2|pages=209–222|doi=10.1111/j.1096-3642.1918.tb02091.x }}</ref>
== Taxonomy and evolutionary history == 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.<ref name=":1">{{Cite journal|last1=Bover|first1=Pere|last2=Mitchell|first2=Kieren J.|last3=Torres-Roig|first3=Enric|last4=Llamas|first4=Bastien|last5=Thomson|first5=Vicki A.|last6=Alcover|first6=Josep Antoni|last7=Agustí|first7=Jordi|last8=Cooper|first8=Alan|last9=Pons|first9=Joan|date=February 2020|title=Ancient DNA from an extinct Mediterranean micromammal— Hypnomys morpheus (Rodentia: Gliridae)—Provides insight into the biogeographic history of insular dormice|journal=Journal of Zoological Systematics and Evolutionary Research|language=en|volume=58|issue=1|pages=427–438|doi=10.1111/jzs.12343|issn=0947-5745|doi-access=free}}</ref>
Cladogram of dormice showing the placement of ''Hypnomys'' after Bover et al. 2020<ref name=":1" /> and Petrova et al. 2024.<ref>{{Cite journal |last1=Petrova |first1=Tatyana V. |last2=Panitsina |first2=Valentina A. |last3=Bodrov |first3=Semyon Yu. |last4=Abramson |first4=Natalia I. |date=2024-09-27 |title=The mitochondrial genome of the critically endangered enigmatic Kazakhstani endemic Selevinia betpakdalaensis (Rodentia: Gliridae) and its phylogenetic relationships with other dormouse species |journal=Scientific Reports |language=en |volume=14 |issue=1 |page=22259 |doi=10.1038/s41598-024-73703-2 |issn=2045-2322 |pmc=11436627 |pmid=39333293|bibcode=2024NatSR..1422259P }}</ref>
{{clade |label1=Gliridae (dormice) |1={{clade |1={{clade |label1=Graphiurinae |1=''Graphiurus'' (African dormice) |label2=Glirinae |2={{clade |1=''Glirulus'' (Japanese dormouse) |2=''Glis'' (edible dormice) }}}} |label2=Leithiinae |2={{clade |1=''Muscardinus'' (hazel dormouse) |2={{clade |1={{clade |1=''Myomimus'' (mouse-tailed dormice) |2=''Selevinia'' (desert dormouse) }} |2={{clade |1=''Dryomys'' (woolly and forest dormice) |2={{clade |1=''Eliomys'' (garden dormice) |2={{extinct}}'''''Hypnomys''''' (Balearic dormice) }}}}}}}}}}}}
The ancestor of ''Hypnomys'' is often assumed to be the prehistoric ''Eliomys'' species ''E. truci'', known from the latest Miocene of the Iberian Peninsula.<ref name=":0" /> 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.<ref name=":1" />
''Hypnomys'' likely arrived in Mallorca during the Messinian salinity crisis (5.96–5.3 million years ago),<ref>{{Cite journal |last1=Azzaroli |first1=A. |date=February 1990 |title=Palaeogeography of terrestrial vertebrates in the perityrrhenian area |url=https://www.sciencedirect.com/science/article/pii/003101829090100L |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=77 |issue=1 |pages=83–90 |doi=10.1016/0031-0182(90)90100-L |access-date=23 January 2026 |via=Elsevier Science Direct|url-access=subscription }}</ref> 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.<ref name=":2" /> 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.<ref name=":4" /> 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.<ref name=":2" /><ref name=":0" /> 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.<ref name=":0" />
=== Species === ''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.<ref name=":0" /> * ''Hypnomys waldreni'' Reumer 1979 (Middle-Late Pliocene, Mallorca) * ''Hypnomys onicensis'' Reumer 1994 (formerly ''H. intermedius'' Reumer, 1981, renamed due to a species of ''Eliomys'' with the same name) (Early Pleistocene, Mallorca) * ''Hypnomys eliomyoides'' Agustí 1980 (Early Pleistocene, Menorca) * ''Hypnomys morpheus'' Bate 1918 (Middle Pleistocene-Holocene, Mallorca) * ''Hypnomys mahonensis'' Bate, 1918 (type) (Late Pleistocene-Holocene, Menorca) Indeterminate remains of ''Hypnomys'' not assigned to species extend back to the Early Pliocene on Mallorca.<ref name=":2">{{Cite journal|last=PALOMBO|first=Maria Rita|date=January 2018|title=Insular mammalian fauna dynamics and paleogeography: A lesson from the Western Mediterranean islands|journal=Integrative Zoology|volume=13|issue=1|pages=2–20|doi=10.1111/1749-4877.12275|issn=1749-4877|pmc=5817236|pmid=28688123}}</ref>
The species ''Hypnomys gollcheri'' de Bruijn, 1966 from the Pleistocene of Malta has been assigned to the separate genus ''Maltamys.<ref name=":0" />''
Although ''Hypnomys'' was considered a subgenus of ''Eliomys'' by Zammit Maempel and de Bruijn, 1982<ref>Zammit Maempel G, de Bruijn H. 1982. The Plio/Pleistocene Gliridae from the Mediterranean Islands reconsidered. Proc K Ned Akad Wet B. 85:113–128</ref> it has generally been considered distinct by other authors.<ref name=":0" />
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.''<ref name=":0" /><ref>{{Cite journal |last1=Quintana Cardona |first1=Josep |last2=Agusti |first2=Jordi |date=18 April 2022 |title=Dental variation in Hypnomys mahonensis Bate, 1918 (Gliridae, Rodentia, Mammalia) from the newly rediscovered type-locality of Punta Esquitxador 17 (Menorca, Balearic Islands, Western Mediterranean) |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2022.2063054 |journal=Historical Biology |volume=35 |issue=5 |language=en |pages=721–733 |doi=10.1080/08912963.2022.2063054 |s2cid=248248694 |issn=0891-2963}}</ref>
== Description == [[File:Hypnomys morpheus&Eliomys quercinus skulls.png|left|thumb|320x320px|The skull and mandible of ''H. morpheus'' (left) compared with the garden dormouse (''Eliomys quercinus)'' including the giant population from Formentera (centre), and normal morphology (right)]] 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 {{Convert|15|cm|in}} and a tail length of around {{Convert|10|cm|in}}. A specimen of ''H. morpheus'' measured in the same study was found to have a head and body length of about {{Convert|18|cm|in}} and a tail length of about {{Convert|11.5|cm|in}}. The tail lengths are proportionally shorter than in species of ''Eliomys''. The specimen of ''H. morpheus'' was estimated to weigh between {{Convert|173 and 284|g|lb}}.<ref name=":3" /> 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.<ref>{{Cite journal|last1=Hennekam|first1=Jesse J.|last2=Benson|first2=Roger B. J.|last3=Herridge|first3=Victoria L.|last4=Jeffery|first4=Nathan|last5=Torres-Roig|first5=Enric|last6=Alcover|first6=Josep Antoni|last7=Cox|first7=Philip G.|date=2020-11-11|title=Morphological divergence in giant fossil dormice|journal=Proceedings of the Royal Society B: Biological Sciences|volume=287|issue=1938|article-number=20202085|doi=10.1098/rspb.2020.2085|pmc=7735280|pmid=33143584}}</ref> The limbs are also robust, with elongated zygopodiums (part of the limbs between the foot and elbow/knee) on both hind and forelimbs.<ref name=":3" />
== Paleobiology == thumb|Life restoration of ''H. morpheus''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''.<ref>{{Cite journal|last1=Orlandi-Oliveras|first1=Guillem|last2=Jordana|first2=Xavier|last3=Moncunill-Solé|first3=Blanca|last4=Köhler|first4=Meike|date=January 2016|title=Bone histology of the giant fossil dormouse Hypnomys onicensis (Gliridae, Rodentia) from Balearic Islands|journal=Comptes Rendus Palevol|language=en|volume=15|issue=1–2|pages=238–244|doi=10.1016/j.crpv.2015.05.001|doi-access=free|bibcode=2016CRPal..15..238O }}</ref> 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,<ref>{{Cite journal|last1=Hautier|first1=Lionel|last2=Bover|first2=Pere|last3=Alcover|first3=Josep Antoni|last4=Michaux|first4=Jacques|date=June 2009|title=Mandible Morphometrics, Dental Microwear Pattern, and Paleobiology of the Extinct Balearic Dormouse Hypnomys morpheus|url=http://www.app.pan.pl/article/item/app54-181.html|journal=Acta Palaeontologica Polonica|language=en|volume=54|issue=2|pages=181–194|doi=10.4202/app.2008.0001|s2cid=54199237|issn=0567-7920|doi-access=free|hdl=10261/85859|hdl-access=free}}</ref> An analysis of the morphology of the lower jaw suggests that was probably efficient at gnawing and chewing.<ref>{{Cite journal |last1=Hennekam |first1=Jesse J |last2=Herridge |first2=Victoria L |last3=Cox |first3=Philip G |date=1 June 2023 |title=Feeding biomechanics reveals niche differentiation related to insular gigantism |url=https://academic.oup.com/evolut/article/77/6/1303/7071587 |journal=Evolution |language=en |volume=77 |issue=6 |pages=1303–1314 |doi=10.1093/evolut/qpad041 |pmid=36881990 |issn=0014-3820|doi-access=free }}</ref> 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.<ref name=":3" /> 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.<ref name=":5">{{Cite journal|last1=Quintana Cardona|first1=Josep|last2=Moncunill-Solé|first2=Blanca|date=May 2014|title=Reconsidering locomotor habits and life style of the Balearic insular giant rodent Hypnomys Bate, 1918 from the allometry of the limb long bones|url=https://linkinghub.elsevier.com/retrieve/pii/S1631068313002108|journal=Comptes Rendus Palevol|language=en|volume=13|issue=4|pages=297–306|doi=10.1016/j.crpv.2013.11.003|bibcode=2014CRPal..13..297Q |url-access=subscription}}</ref> Analysis of the cribriform plate of a probable specimen of ''H. morpheus'' suggests that the species probably had a well developed senses of sight, hearing and smell, the last possibly better developed than the living garden dormice. The former two have been suggested to have been for detecting predators, while the last aided in finding food.<ref>{{Cite journal |last1=Cardona |first1=Josep Quintana |last2=Pons |first2=Miquel Riera |date=September 2025 |title=The cribriform plate of Hypnomys Bate, 1918 (Rodentia: Gliridae) |url=https://link.springer.com/10.1007/s10914-025-09769-0 |journal=Journal of Mammalian Evolution |language=en |volume=32 |issue=3 |doi=10.1007/s10914-025-09769-0 |issn=1064-7554|url-access=subscription |via=Springer Nature Link |access-date=22 January 2026}}</ref> 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.<ref name=":5" />
== Extinction == 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.<ref name=":4">{{Cite journal|last1=Valenzuela|first1=Alejandro|last2=Torres-Roig|first2=Enric|last3=Zoboli|first3=Daniel|last4=Pillola|first4=Gian Luigi|last5=Alcover|first5=Josep Antoni|date=29 November 2021|title=Asynchronous ecological upheavals on the Western Mediterranean islands: New insights on the extinction of their autochthonous small mammals|url=https://journals.sagepub.com/doi/abs/10.1177/09596836211060491|journal=The Holocene|volume=32 |issue=3 |pages=137–146|doi=10.1177/09596836211060491|s2cid=244763779|issn=0959-6836|url-access=subscription|hdl=11584/322952|hdl-access=free}}</ref> 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.<ref>{{Cite journal|last1=Bover|first1=Pere|last2=Alcover|first2=Josep Antoni|date=21 December 2007|title=Extinction of the autochthonous small mammals of Mallorca (Gymnesic Islands, Western Mediterranean) and its ecological consequences: Extinction of small mammals of Mallorca|url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2699.2007.01839.x|journal=Journal of Biogeography|language=en|volume=35|issue=6|pages=1112–1122|doi=10.1111/j.1365-2699.2007.01839.x|s2cid=83874320 |url-access=subscription}}</ref> The two other native pre-human terrestrial vertebrates of Mallorca and Menorca, the still living Lilford's wall lizard (''Podarcis lilfordi)'' and Majorcan midwife toad (''Alytes muletensis'') have been heavily impacted by human presence on the archipelago, and today are only confined to remote areas.<ref>{{Citation |last1=Silva-Rocha |first1=Iolanda |title=Herpetological History of the Balearic Islands: When Aliens Conquered These Islands and What to Do Next |date=2018 |work=Histories of Bioinvasions in the Mediterranean |volume=8 |pages=105–131 |editor-last=Queiroz |editor-first=Ana Isabel |url=http://link.springer.com/10.1007/978-3-319-74986-0_5 |access-date=2025-10-16 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-74986-0_5 |isbn=978-3-319-74985-3 |last2=Montes |first2=Elba |last3=Salvi |first3=Daniele |last4=Sillero |first4=Neftalí |last5=Mateo |first5=José A. |last6=Ayllón |first6=Enrique |last7=Pleguezuelos |first7=Juan M. |last8=Carretero |first8=Miguel A. |editor2-last=Pooley |editor2-first=Simon |url-access=subscription}}</ref>
== See also == * Holocene extinction * List of extinct animals of Europe * ''Leithia'' a rabbit sized giant dormouse known from the Pleistocene of Sicily and Malta, largest known dormouse
== References == {{Reflist}}
{{Sciuromorpha|state=collapsed}} {{Taxonbar|from=Q3787901}}
Category:Rodent genera Category:Prehistoric Europe Category:Pleistocene Europe Category:Holocene extinctions Category:Dormice