Contributions to Zoology, 77 (1) – 2008Jelle S. Zijlstra; Lars W. van den Hoek Ostende; Rokus Awe Due: Verhoeven’s giant rat of Flores (Papagomys theodorverhoeveni, Muridae) extinct after all?

To refer to this article use this url: http://ctoz.nl/vol77/nr01/a04

Material and methods

The fossil material consists of isolated teeth as well as fragments of maxillaries and mandibles. Most of the material was obtained by dry sieving sediment from the Liang Bua Cave, although part was excavated directly. All molars were measured using a Leica Ortholux measuring microscope. Length and with were measured at right angles. Four characters employed by Musser (1981) in his diagnosis of P. theodorverhoeveni were scored (Fig. 1). These are: the presence of an anterocentral cusp on m1 (AC) (1 in Fig. 1), the presence of an anterolabial cusplet on m1 (Cv3) (2 in Fig. 1), presence of a posterolabial cusplet on m1 (Cv5) (3 in Fig. 1), and presence of an anterolabial cusp on m2 (AL) (4 in Fig. 1). These cusps are according to Musser present in P. theodorverhoeveni, but absent in P. armandvillei. Furthermore, the laminae are more upright positioned in P. theodorverhoeveni.

FIG2

Fig. 1. Holotypes of Papagomys armandvillei (RMNH 18301, below) and P. theodorverhoeveni (RGM 195620, above) indicating the elements mentioned in the text (anterocentral cusp, 1; anterolabial cusplet, 2; posterolabial cusplet, 3; anterolabial cusp, 4).

Because morphology is affected by wear, we defined three wear stages. In wear stage 1, the wear facets of all individual cusps are separated. Wear stage 2 is defined by merger within laminae, whereas molars in which mergers of wear facets between laminae occur were placed in wear stage 3.

FIG2

Table 1. Measurements of Papagomys molars from Liang Bua and from MZB 12716 (Mean ± SD, observed range in parentheses, number of individuals measured). For the lower molars of MZB 12716 the estimated length is given in square brackets.

FIG2

Fig. 2. Length/width diagram of the m1 of Papagomys species from Liang Bua. The estimated measurements of MZB 12716 are indicated by a rectangle.

FIG2

Fig. 3. Length/width diagram of the m2 of Papagomys species from Liang Bua. The estimated measurements of MZB 12716 are indicated by a rectangle.

FIG2

Fig. 4. Length/width diagram of the m3 of Papagomys species from Liang Bua. The estimated measurements of MZB 12716 are indicated by a rectangle.

FIG2

Fig. 5. Length/width diagram of the M1 of Papagomys species from Liang Bua. The width given by Sayunto and Watts (2002) is indicated by a line.

FIG2

Fig. 6. Length/width diagram of the M2 of Papagomys species from Liang Bua. The width given by Sayunto and Watts (2002) is indicated by a line.

FIG2

Fig. 7. Length/width diagram of the M3 of Papagomys species from Liang Bua. The width given by Sayunto and Watts (2002) is indicated by a line.

We estimated the lengths of the lower molars of MZB 12716 from Suyanto and Watts (2002, figure 1), using as a reference the values given in their table 1 for m1-m3 length and width of the various lower molars. The estimated lengths are given in Table 1. The measurements are indicated by a rectangle in Figs. 2, 3, 4, allowing a 5% margin of error.

FIG2

Table 2. Summary of morphological variation in Papagomys material from Liang Bua. For each character, the first column outlines the number of specimens with a certain state and the second the percentage of specimens with that state. Abbreviations: WS = wear stage, AC = anterocentral cusp, AL = anterolabial cusp, Cv3 = anterolabial cusplet, Cv5 = posterolabial cusplet.

FIG2

Fig. 8. Dendrogram showing a cluster analysis (Average linkage, squared Euclidean distance) of Liang Bua complete lower dentitions in combination with the holotypes of Papagomys armandvillei (including the holotype: d = dextral, s = sinistral), P. theodorverhoeveni and MZB 12716.

All multivariate and statistical analyses were performed using SPSS 15.0.

The material from Liang Bua described in this paper is currently kept in Naturalis, Leiden, but will be stored in the Pasat Arkeologi Nasional Indonesia, Jakarta.