Lava mouse

{{Short description|Extinct species of rodent}}

{{speciesbox

| name = Lava mouse

| fossil_range = Late Pleistocene-Holocene

| image = Malpaisomys restoration.jpg

| image_upright = 1.1

| image_caption = A life restoration of a lava mouse

| status = EX

| genus = Malpaisomys

| parent_authority = Hutterer, Lopez-Martinez & Michaux, 1988

| display_parents = 2

| species = insularis

| authority = Hutterer, Lopez-Martinez & Michaux, 1988

}}

The lava mouse (Malpaisomys insularis) is an extinct endemic rodent from the Canary Islands, Spain.{{cite journal|last1=Hutterer|first1=Rainer|last2=Lopez-Martinez|first2=Nieves|last3=Michaux|first3=Jacques|date=1988|title=A new rodent from Quaternary deposits of the Canary Islands and its relationships with Neogène and recent murids of Europe and Africa|journal=Palaeovertebrata| url=https://palaeovertebrata.com/articles/view/339|volume=18|issue=4|pages=241–262}} It is the only species in the genus Malpaisomys.

The lava mouse is known from Holocene and Pleistocene deposits in the eastern Canary Islands, including Fuerteventura, Lanzarote, and nearby islets. Radiocarbon dates indicate that it became extinct after the European arrival in the archipelago sometime after 1270 AD, probably due to the introduction of rats.{{Cite journal|last1=Rando|first1=Juan Carlos|last2=Alcover|first2=Josep Antoni|last3=Navarro|first3=Juan Francisco|last4=García-Talavera|first4=Francisco|last5=Hutterer|first5=Rainer|last6=Michaux|first6=Jacques|date=September 2008|title=Chronology and causes of the extinction of the Lava Mouse, Malpaisomys insularis (Rodentia: Muridae) from the Canary Islands|url=https://www.cambridge.org/core/journals/quaternary-research/article/abs/chronology-and-causes-of-the-extinction-of-the-lava-mouse-malpaisomys-insularis-rodentia-muridae-from-the-canary-islands/A9FFF596A9950971D0FE3DD5286C26E8|journal=Quaternary Research|language=en|volume=70|issue=2|pages=141–148|doi=10.1016/j.yqres.2008.04.012|bibcode=2008QuRes..70..141R |s2cid=86519083 |issn=0033-5894|url-access=subscription}}

The species is estimated to have a live body mass of around {{Convert|90|g|oz}}.{{Cite journal |last1=Renom |first1=Pere |last2=de-Dios |first2=Toni |last3=Civit |first3=Sergi |last4=Llovera |first4=Laia |last5=Sánchez-Gracia |first5=Alejandro |last6=Lizano |first6=Esther |last7=Rando |first7=Juan Carlos |last8=Marquès-Bonet |first8=Tomàs |last9=Kergoat |first9=Gael J. |last10=Casanovas-Vilar |first10=Isaac |last11=Lalueza-Fox |first11=Carles |date=December 2021 |title=Genetic data from the extinct giant rat from Tenerife (Canary Islands) points to a recent divergence from mainland relatives |journal=Biology Letters |language=en |volume=17 |issue=12 |doi=10.1098/rsbl.2021.0533 |issn=1744-957X |pmc=8692034 |pmid=34932923}} A study of its skeletal characteristics suggested that the lava mouse lived in fissures opened in the lava fields. The morphology of its teeth indicates that it was an herbivore.{{cite journal |last1=Boye |first1=Peter |last2=Hutterer |first2=Rainer |last3=López-Martínez |first3=Nieves |last4=Michaux |first4=Jacques |title=A reconstruction of the Lava mouse (Malpaisomys insularis), an extinct rodent of the Canary Islands |journal=Zeitschrift für Säugetierkunde |date=1992 |volume=57 |pages=29–38 |url=https://www.biodiversitylibrary.org/part/192037}}

Its evolutionary relationships were unresolved due to its fairly generic morphology. Rodents on islands generally increase in size during the course of their evolution; the lava mouse was fairly small for an insular rodent (some 20 cm in overall length). Thus, it is more likely than not that it evolved from small Pliocene mainland genera Paraethomys, Occitanomys, or relatives thereof, than being a later derivative of the Deomyinae.{{cite journal |last1=Renaud |first1=Sabrina |last2=Michaux |first2=Jacques |title=Parallel evolution in molar outline of murine rodents: the case of the extinct Malpaisomys insularis (Eastern Canary Islands) |journal=Zoological Journal of the Linnean Society |date=December 2004 |volume=142 |issue=4 |pages=555–572 |doi=10.1111/j.1096-3642.2004.00140.x |doi-access=free}}

A 2012 genomic study recovered it as a highly divergent lineage within the genus Mus sensu lato most closely related to Coelomys.{{Cite journal|last1=Pagès|first1=Marie|last2=Chevret|first2=Pascale|last3=Gros-Balthazard|first3=Muriel|last4=Hughes|first4=Sandrine|last5=Alcover|first5=Josep Antoni|last6=Hutterer|first6=Rainer|last7=Rando|first7=Juan Carlos|last8=Michaux|first8=Jacques|last9=Hänni|first9=Catherine|date=2012-02-21|title=Paleogenetic Analyses Reveal Unsuspected Phylogenetic Affinities between Mice and the Extinct Malpaisomys insularis, an Endemic Rodent of the Canaries|journal=PLOS ONE|language=en|volume=7|issue=2|pages=e31123|doi=10.1371/journal.pone.0031123|issn=1932-6203|pmc=3283599|pmid=22363563|bibcode=2012PLoSO...731123P|doi-access=free}}

This rodent owes its name Malpaisomys to the Spanish word malpaís ("badlands"), denoting the lava fields where its fossil remains are sometimes found in cavities.