Microgale macpheei
Encyclopedia
Microgale macpheei is an extinct shrew tenrec from southeastern Madagascar
. It is known only from two partial skulls found in Andrahomana cave, which radiocarbon dating
of associated rodent remains suggests are about 2000 years old. It is the only known recently extinct tenrec. First described in 2007, it is most similar to the smaller Microgale brevicaudata of northern and western Madagascar. M. macpheei has a broad rostrum (front part of the skull) and, like M. brevicaudata, lacks a diastema
(gap) between the premolar
s. A number of details of tooth morphology are characteristic of M. macpheei.
, Natalie Vasey, and Burney. The species was named after Ross MacPhee in honor of his contributions to knowledge of the genus Microgale and the paleontology of Madagascar. Goodman and colleagues considered the living Microgale brevicaudata from northern and western Madagascar to be the closest relative of M. macpheei; some populations of this tenrec have since been separated into a different species, M. grandidieri
. The common name
"MacPhee's shrew tenrec" has been proposed for M. macpheei. The genus of M. macpheei, Microgale, includes more than 20 species and is the largest of the tenrec family, which includes a variety of other Madagascan mammals.
s, or lower jaws) lacking the back part (the parietal bone
s and further back) as well as the incisor
s, canines, and second premolar
s; and another damaged cranium lacking the same parts as well as the left toothrow. Both show no evidence of ongoing tooth replacement, indicating that the permanent dentition is complete. M. macpheei was larger in most measurements than M. brevicaudata, but because of small samples, some differences are not statistically significant. The length of the bony palate
in the two specimens of M. macpheei is 9.4 and 9.7 mm, compared to 7.1 to 9.0 mm in eight adult M. brevicaudata. In both specimens, the length of the molar row is 3.0 mm, compared to 2.4 to 2.8 mm in the sample of M. brevicaudata.
The rostrum (front part of the skull) is short and blunt in both M. macpheei and M. brevicaudata, contrasting with the condition in other Microgale, but the rostrum of M. brevicaudata is distinctly more tapered at the front, whereas that of M. macpheei is more blunt at the front. Unlike other Microgale, M. brevicaudata and M. macpheei lack gaps (diastemata
) between the premolars. M. macpheei had larger, more robust teeth than M. brevicaudata. In both species, the mesiostyle and distostyle, two crests, on the fourth premolar (P4) and the molars
are reduced relative to the condition in other Microgale. M. macpheei lacks an extension of the protocone
cusp on the lingual (inner) side of the third upper premolar (P3) and P4, present in M. brevicaudata, and has the paracone
cusp on P4 less well-developed. On the other hand, the front part of the ectostyle crest on P4 is larger. The relative lengths of some of the crests on the two last molars also differ between the two species.
, suggests formerly more mesic
(wet) conditions around the cave, which is currently in a dry area. In addition to M. macpheei, three other tenrecs have been described from subfossil
material, but none are currently recognized as valid species; thus, M. macpheei is at present the only known recently extinct tenrec species. However, there is a remnant patch of mesic forest near Andrahomana, where a population of M. macpheei may survive. Although no radiocarbon dating
has been carried out on M. macpheei remains, bones of the rodent Macrotarsomys petteri
from layers in the same cave deposit bracketing those where M. macpheei was found yield dates of around 2480 and 1760 Before Present
.
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. It is known only from two partial skulls found in Andrahomana cave, which radiocarbon dating
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
of associated rodent remains suggests are about 2000 years old. It is the only known recently extinct tenrec. First described in 2007, it is most similar to the smaller Microgale brevicaudata of northern and western Madagascar. M. macpheei has a broad rostrum (front part of the skull) and, like M. brevicaudata, lacks a diastema
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
(gap) between the premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s. A number of details of tooth morphology are characteristic of M. macpheei.
Taxonomy
Remains of shrew tenrecs (Microgale) were found during expeditions to the cave of Andrahomana in southeastern Madagascar, led by David Burney in 2000 and 2003. The Microgale material was described as a new species, M. macpheei, in 2007 by Steven GoodmanSteven Goodman
Steven Goodman is an American Conservation Biologist, and field biologist on staff in the Department of Zoology at the Field Museum of Natural History....
, Natalie Vasey, and Burney. The species was named after Ross MacPhee in honor of his contributions to knowledge of the genus Microgale and the paleontology of Madagascar. Goodman and colleagues considered the living Microgale brevicaudata from northern and western Madagascar to be the closest relative of M. macpheei; some populations of this tenrec have since been separated into a different species, M. grandidieri
Microgale grandidieri
Microgale grandidieri is a species of shrew tenrec occurring in the dry forests of western and southwestern Madagascar. Populations of this species were formerly included in Microgale brevicaudata; M...
. The common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
"MacPhee's shrew tenrec" has been proposed for M. macpheei. The genus of M. macpheei, Microgale, includes more than 20 species and is the largest of the tenrec family, which includes a variety of other Madagascan mammals.
Description
Microgale macpheei is known from two specimens: a damaged cranium (skull without mandibleMandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
s, or lower jaws) lacking the back part (the parietal bone
Parietal bone
The parietal bones are bones in the human skull which, when joined together, form the sides and roof of the cranium. Each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin pariet-, wall....
s and further back) as well as the incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s, canines, and second premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s; and another damaged cranium lacking the same parts as well as the left toothrow. Both show no evidence of ongoing tooth replacement, indicating that the permanent dentition is complete. M. macpheei was larger in most measurements than M. brevicaudata, but because of small samples, some differences are not statistically significant. The length of the bony palate
Palate
The palate is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but, in most other tetrapods, the oral and nasal cavities are not truly separate. The palate is divided into two parts, the anterior...
in the two specimens of M. macpheei is 9.4 and 9.7 mm, compared to 7.1 to 9.0 mm in eight adult M. brevicaudata. In both specimens, the length of the molar row is 3.0 mm, compared to 2.4 to 2.8 mm in the sample of M. brevicaudata.
The rostrum (front part of the skull) is short and blunt in both M. macpheei and M. brevicaudata, contrasting with the condition in other Microgale, but the rostrum of M. brevicaudata is distinctly more tapered at the front, whereas that of M. macpheei is more blunt at the front. Unlike other Microgale, M. brevicaudata and M. macpheei lack gaps (diastemata
Diastema (dentistry)
Diastema is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars.-In humans:...
) between the premolars. M. macpheei had larger, more robust teeth than M. brevicaudata. In both species, the mesiostyle and distostyle, two crests, on the fourth premolar (P4) and the molars
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
are reduced relative to the condition in other Microgale. M. macpheei lacks an extension of the protocone
Protocone
thumb|500px|right|Right upper molar showing the four main upper molars cusps.The protocone is a cusp of the molars of the upper dentition in Placental and Marsupial vertebrates .It is found at the mesiolingual area of the tooth...
cusp on the lingual (inner) side of the third upper premolar (P3) and P4, present in M. brevicaudata, and has the paracone
Paracone
An atmospheric reentry or spaceflight mission abort concept using an inflatable cone.A notable feature of the paracone concept is that it facilitates an abort throughout the entire flight profile....
cusp on P4 less well-developed. On the other hand, the front part of the ectostyle crest on P4 is larger. The relative lengths of some of the crests on the two last molars also differ between the two species.
Distribution and ecology
Microgale macpheei is known only from the cave of Andrahomana. Its past presence there, like that of the extinct rodent Hypogeomys australisHypogeomys australis
Hypogeomys australis is an extinct rodent from central and southeastern Madagascar. First described in 1903, it is larger than its close relative, the living Hypogeomys antimena, which occurs further west, but otherwise similar. Average length of the femur is 72.1 mm, compared to 63.8 mm...
, suggests formerly more mesic
Mesic habitat
In ecology, a mesic habitat is a type of habitat with a moderate or well-balanced supply of moisture, e.g., a mesic forest, a temperate hardwood forest, or dry-mesic prairie. Compared to a dry habitat, a mesic habitat is moister....
(wet) conditions around the cave, which is currently in a dry area. In addition to M. macpheei, three other tenrecs have been described from subfossil
Subfossil
Subfossil refers to remains whose fossilization process is not complete, either for lack of time or because the conditions in which they were buried were not optimal for fossilization....
material, but none are currently recognized as valid species; thus, M. macpheei is at present the only known recently extinct tenrec species. However, there is a remnant patch of mesic forest near Andrahomana, where a population of M. macpheei may survive. Although no radiocarbon dating
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
has been carried out on M. macpheei remains, bones of the rodent Macrotarsomys petteri
Macrotarsomys petteri
Macrotarsomys petteri, also known as Petter's Big-footed Mouse, is a Malagasy rodent in the genus Macrotarsomys. With a head and body length of 150 mm and body mass of 105 g , Macrotarsomys petteri is the largest species of its genus...
from layers in the same cave deposit bracketing those where M. macpheei was found yield dates of around 2480 and 1760 Before Present
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
.
Literature cited
- Goodman, S.M., Vasey, N. and Burney, D.A. 2007. Description of a new species of subfossil shrew tenrec (Afrosoricida: Tenrecidae: Microgale) from cave deposits in southeastern Madagascar (subscription required). Proceedings of the Biological Society of Washington 120:367–376.
- MacPhee, R.D.E. 1987. The shrew tenrecs of Madagascar: systematic revision and Holocene distribution of Microgale (Tenrecidae, Insectivora). American Museum Novitates 2889:1–45.
- Muldoon, K.M., de Blieux, D.D., Simons, E.L. and Chatrath, P.S. 2009. The subfossil occurrence and paleoecological significance of small mammals at Ankilitelo Cave, southwestern Madagascar (subscription required). Journal of Mammalogy 90(5):1111–1131.
- Olson, L.E., Rakotomalala, Z., Hildebrandt, K.B.P., Lanier, H.C., Raxworthy, C.J. and Goodman, S.M. 2009. Phylogeography of Microgale brevicaudata (Tenrecidae) and description of a new species from western Madagascar (subscription required). Journal of Mammalogy 90(5):1095–1110.