Middle-sized murids from Liang Bua (Flores, Indonesia): insular endemics, human introductions and palaeoenvironment

Abstract

The Liang Bua Cave (Flores, Indonesia) has yielded numerous fossils of murids from the Late Pleistocene and Holocene, including giant rats. In this study, we describe the middle-sized forms, that is, murids of about the same size as Rattus rattus. Two endemic species were found at Liang Bua, Komodomys rintjanus and Paulamys naso, which were present since the oldest phases of the occupation of the cave. Both have survived until the present day and currently occupy contrasting habitats. Two commensal species, presumably R. rattus and R. argentiventer, reached the island only in the youngest phases. Based on the ecological preferences of recent Komodomys and Paulamys, it appears that the arrival of Neolithic Man and commensal rats coincides with a period of relative drought.

Quaternary vertebrate faunas from Sumba, Indonesia: implications for Wallacean biogeography and evolution

“…Vertebrate material was collected by dry sieving. Exploration of 19 other caves across Sumba (electronic supplementary material, table S1) only found unfossilized bones of native bats and invasive murids that reached the eastern Lesser Sundas in the Late Holocene [ 20 , 24 ].…”

“…One of the new murids differs from these genera in having a posterior cingulum on M3 (absent in Hooijeromys, Komodomys, Papagomys and Paulamys); cusp t3 present on M2 and M3 (typically absent in Papagomys and Paulamys) and reduced on M1 (relatively large in Hooijeromys and Komodomys, absent in Paulamys); chevronate upper molar laminae (transverse in Hooijeromys and Paulamys); M2 longer than wide (unlike Hooijeromys); posterior margin of incisive foramina opposite anterior M1 (more anterior in Hooijeromys, Papagomys and Paulamys); anterolabial cuspid not disrupting transverse anterior margin of m2 (versus Komodomys and Papagomys) and posterior cingulid absent on m3 (versus Komodomys) [12,[23][24][25][26]. Its mandible has reduced coronoid and angular processes that do not extend dorsally or posteriorly beyond the level of the articular condyle; this mandible morphology is only similar to Komodomys among the endemic Flores murid genera, but is otherwise similar to some southeast Asian Rattini (e.g.…”

“…H. floresiensis coexisted with a distinctive, impoverished Quaternary insular vertebrate fauna. Late Pleistocene deposits on Flores contain the pygmy proboscidean Stegodon florensis insularis, the Komodo dragon Varanus komodoensis and a smaller extinct varanid with distinctive bunodont teeth, Varanus hooijeri, giant murid rodents (Papagomys armandvillei, Papagomys theodorverhoeveni, Spelaeomys florensis and an undescribed giant shrew rat), smaller murids (Komodomys rintjanus, Paulamys naso, Rattus hainaldi) and a giant stork [12,[18][19][20][21][22][23][24]. Older Pleistocene deposits on Flores also contain a giant tortoise, another giant murid (Hooijeromys nusatenggara) and other Stegodon species [12,20,22].…”

“…Older Pleistocene deposits on Flores also contain a giant tortoise, another giant murid (Hooijeromys nusatenggara) and other Stegodon species [12,20,22]. All three smaller murids, one giant rat (P. armandvillei) and Komodo dragons still occur on Flores and/or nearby small islands [12,[24][25][26][27]; P. theodorverhoeveni, Sp. florensis and V. hooijeri survived into the Holocene but are now extinct [20,22,23,28].…”

Cladistics and insular evolution, an unfortunate marriage? Another tangle in the Deinogalerix analysis of Borrani et al. (2017)

“…Indeed, H. floresiensis shows typical insular features such as a small body size and a diminished brain capacity (Brown et al., ). More detailed biogeographical studies suggest that the accompanying fauna had its origins in Sulawesi (Van den Bergh, ; Van den Bergh et al., ; Locatelli et al., ; Locatelli et al., ; Dennell et al., ), so it is plausible that Homo also arrived via that route. The first finds were dated to the late Pleistocene, but recently middle Pleistocene fossils of H. floresiensis were reported from the island by Van den Bergh et al.…”