Systematics of Megachiropteran Bats in the Solomon Islands Part 2

Family PTEROPODIDAE

Subfamily Pteropodinae

Rousettus Gray

1821. _Rousettus_ Gray, London Medical Repository, 15:299, April 1.

1843. _Xantharpyia_ Gray, List of species ... British Museum, p. 37.

1852. _Cynonycteris_ Peters, Reise nach Mossambique, p. 25.

The genus _Rousettus_ occurs throughout the tropical regions of the Old World, and in the Solomons is readily distinguished from all other megachiropteran genera by having both a small claw on the second digit and free caudal vertebrae. The oriental species have been divided into two groups on the basis of size (Tate, 1942:344). The subspecies _Rousettus amplexicaudatus hedigeri_ appears to be the sole representative of this genus in the Solomon Islands. Prior to 1953, several workers (Thomas, 1887b:323, 1888b:475; Matschie, 1899:68; Sanborn, 1931:11) used the name _Rousettus amplexicaudatus brachyotis_ for it, but Pohle (1953) suggested that the specimens from the Solomons recorded by earlier workers were _R. a. hedigeri_ named by him on the basis of the specimen that he saw from Bougainville.

=Rousettus amplexicaudatus=

_Rousettus amplexicaudatus_ has at least three subspecies, one of which is endemic to the Solomon Islands. The species is wide-ranging, being known from as far west as Thailand (Ellerman and Morrison-Scott, 1966:93) and as far east as the Solomons.

[Ill.u.s.tration: FIG. 3. Distribution of _Rousettus amplexicaudatus hedigeri_. For names of islands see Fig. 2.]

=Rousettus amplexicaudatus hedigeri= Pohle

1953. _Rousettus amplexicaudatus hedigeri_ Pohle, Z. Saugetierk., 17:127, October 27, type from Bougainville.

1887. _Cynonycteris brachyotis_, Thomas, Proc. Zool. Soc. London, p. 323, March 15; 1888, Thomas, Proc. Zool. Soc. London, p. 475, December 4, from Fauro.

1889. _Xantharpyia brachyotis_, Matschie, Die Megachiroptera ...

naturkunde, p. 68, from Guadalca.n.a.l.

1912. _Rousettus brachyotis_, Andersen, Catalogue of the Chiroptera ... British Museum, 1:809; 1931, Sanborn, Publ. Field Mus. Nat.

Hist., Zool. Ser., 18:11, February 12, from Santa Ysabel.

_Specimens examined_ (20 males and 21 females; all in alcohol; ten crania extracted and cleaned).--Guadalca.n.a.l in May, 23863, 23915; Fauro in April, 23804-5; Malaita in June, 24079; Choiseul in March, 23563-4, 23616, 23627, 23630, 23632-3, 23642, 23658, 23663-4, 23680, 23692-3, 23713, 23722; Kolombangara in January and February, 23343, 23366, 23382-4, 23389-90, 23408-9, 23424, 23455, 23471-4, 23501.

_Measurements._--Average and extreme external measurements of 13 males and 18 females are, respectively, as follows: Length of head and body, 104.4 (99-118), 108.6 (104-117); tail vertebrae, 16.8 (13-19), 17.6 (15-24); hind foot, 18.0 (16-19), 16.2 (12-18); ear, 15.9 (15-17), 15.0 (14-16); length of forearm, 70.1 (66.0-74.1), 68.1 (65.0-69.1). Average and extreme measurements of skulls of five males and five females are, respectively, as follows: Greatest length of skull, 33.2 (33.0-33.7), 31.5 (30.9-32.1); condylobasal length, 31.3 (30.9-31.9), 30.1 (29.3-30.8); palatal length, 14.0 (13.3-14.8), 13.3 (13.0-13.7); zygomatic breadth, 20.8 (19.8-21.8), 19.4 (18.7-20.8); length of maxillary tooth-row, 11.0 (10.9-11.3), 10.3 (10.1-10.6); length of mandibular tooth-row, 12.6 (12.4-12.9), 11.8 (11.7-12.2).

_Remarks._--The specimens from Choiseul, Kolombangara, and Malaita islands provide new records of distribution for _Rousettus amplexicaudatus hedigeri_ (Fig. 3). It was described as smaller than _R.

a. brachyotis_ Dobson, which is known from New Guinea, Amboina, and the Bismarck Archipelago (Pohle, 1953:127-128). Andersen (1912:809) gave the range of length of forearm in _R. a. brachyotis_ as 73-81, whereas Pohle (1953:127) gave the length of forearm of the type specimen of _R. a.

hedigeri_ (adult male) as 67. Measurements of specimens examined by me indicate that _hedigeri_ occurs throughout the Solomon Islands. Cranial measurements of my specimens and Pohle's type are less than those of _R.

a. brachyotis_ (see Andersen, 1912:48).

Sanborn (1931:11) noted that the forearms of three males examined by him were longer than that of a female. Mean and range for length of forearm of males and females listed herein, respectively, are 70.1 (66.0-74.1) and 68.1 (65.0-69.1). Also, each of seven cranial measurements taken by me averaged more in males than in females. Sagittal and lambdoidal crests are more prominent in males than in females.

TABLE 1. A Summary of Breeding Data for Females of _Rousettus amplexicaudatus hedigeri_ Collected December to June.

===========+===========+==============+===========+============= Total Number Number of MONTH number adult [F][F] Number immature collected collected lactating individuals -----------+-----------+--------------+-----------+------------- December 3 3 3 0 January 11 11 8 0 February 6 0 -- 1 March 16 1 0 9 April 2 2 0 0 June 1 1 0 0 -----------+-----------+--------------+-----------+-------------

As shown in Table 1, adult females obtained in December and January were lactating when captured whereas those obtained in March, April, and June were not. More than half of the individuals collected in March were immature (judging from small size, unfused epiphyses, and lack of wear on teeth). The immature individuals probably had been nursing in December and January.

=Pteralopex= Thomas

1888. _Pteralopex_ Thomas, Ann. Mag. Nat. Hist., ser. 6, 1:155, February 1.

1762. _Pteropus_ Brisson, Regnum animale ..., ed. 2, p. 153.

_Pteralopex_, with one species and two subspecies, is the only megachiropteran genus endemic to the Solomons. Thomas (1888b:475) considered this unusual bat a relic, isolated from the time when pteropodids had cuspidate cheek-teeth. Although two workers (Matschie, 1899:11; Simpson, 1945:54) have synonymized _Pteralopex_ with _Pteropus_, I regard _Pteralopex_ as a morphologically distinct genus.

Individuals of _Pteralopex_ can be distinguished from all species of _Pteropus_ in the Solomon Islands by the following features: wing membranes originate along dorsal midline; braincase diminutive relative to rest of skull; sagittal crest p.r.o.nounced; cheek-teeth cuspidate, broad and ma.s.sive; i2 about 10 times larger than i1; upper canines with well-developed secondary cusp; pos...o...b..tal process fused with zygomatic arch, forming complete bony ring around orbit.

Andersen (1909a:216; 1912:436) considered the relationships of _Pteralopex_ and _Pteropus_ and concluded that _Pteropus pselaphon_ Lay, 1829, from the Sulphur Islands east of Taiwan, and _Pteropus samoensis_ Peale, 1848, from the Samoan Islands, were the "closest" living relatives of _Pteralopex_. He stated further that _Pteralopex_ "presents in fact scarcely a single character which is not either developed to a certain extent or at least distinctly foreshadowed in _Pteropus pselaphon_, _pilosus_, _tuberculatus_, or _leucopterus_." In summary, Andersen thought several species of _Pteropus_ had undergone evolutionary development resembling that in _Pteralopex_, and that the latter, with its ma.s.sive, cuspidate cheek-teeth, could be considered a highly modified _Pteropus_. For this hypothesis to be plausible, one must a.s.sume that the originally complex cheek-teeth of pteropodids became simple and, at least in the case of _Pteralopex_, secondarily became complex once again. According to present-day theory of evolutionary development, his hypothesis is improbable. Thomas (1888b:475) probably was correct when he considered _Pteralopex_ an isolated relic.

Although _Pteralopex_ usually is listed after _Pteropus_ in phylogenetic arrangements (see, for example, Sanborn, 1931:21; Pohle, 1953:129; Laurie and Hill, 1954:40), I have placed _Pteralopex_ before _Pteropus_.

=Pteralopex atrata=

Two subspecies of _Pteralopex atrata_ (_P. a. atrata_ and _P. a.

anceps_) have been named; specimens of both are rare in museum collections. Thomas (1888_a_:155) described adults of _atrata_. Sanborn (1931:21) examined the one additional specimen known to me and reported that it agreed with Thomas' description.

Andersen (1909_b_:266) used a subadult female ("nearly fully grown") as the holotype of _anceps_. At least five additional specimens, all adults, of _anceps_ now are housed in various collections. Judging from these individuals, the holotype of _anceps_ was only four-fifths grown and because he used an immature individual, Andersen's (1912:437) criteria for distinguishing the two subspecies mostly are invalid.

[Ill.u.s.tration: FIG. 4. Distribution of _Pteralopex atrata_; _P. atrata atrata_ ([RW]) and _P. atrata anceps_ ([BC]).

For names of islands see Fig. 2.]

Key to Subspecies of _Pteralopex atrata_

1. Length of forearm 139-144 mm.; dorsal surface of distal one-fourth of tibia and entire metatarsus naked; known only from Guadalca.n.a.l and Santa Ysabel islands _Pteralopex atrata atrata_

1'. Length of forearm 162-166 mm.; dorsal surface of distal one-fourth of tibia and entire metatarsus furred; known only from Bougainville and Choiseul islands _Pteralopex atrata anceps_

=Pteralopex atrata atrata= Thomas

1888. _Pteralopex atrata_ Thomas, Ann. Mag. Nat. Hist., ser. 6, 1:155, February, type from Guadalca.n.a.l; 1888, Thomas, Proc. Zool.

Soc. London, p. 475, December 4; 1896, Heude, Mem. Hist. Nat.

Emp. China, 3:179; 1897, Trouessart, Catalogus Mammalium ..., 1:83; 1907, Miller, Bull. U. S. Nat. Mus., 57:60, June 29; 1912, Andersen, Catalogue of the Chiroptera ... British Museum, 1:439; 1931, Sanborn, Publ. Field Mus. Nat. Hist., Zool. Ser., 18:21, February 12, from Santa Ysabel.

1954. _Pteralopex atrata atrata_, Laurie and Hill, List of land mammals of New Guinea, Celebes and adjacent islands, p. 40, June 30.

1899. _Pteropus (Pteralopex) atrata_, Matschie, Die Megachiroptera ... naturkunde, p. 11; 1904, Trouessart, Catalogus Mammalium ..., Suppl., p. 49.

_Specimens examined._--None.