shrew tenrec
''Microgale'' is a genus of mammal in the family Tenrecidae. There are 21 living species on the island of Madagascar and one extinct species known from a fossil. Some species have been discovered in the last twenty years.
On the basis of molec ...
from southeastern
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
. It is known only from two partial skulls found in Andrahomana cave, which
radiocarbon dating
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.
The method was de ...
of associated rodent remains suggests are about 3000 years old. It is the only known recently extinct
tenrec
A tenrec is any species of mammal within the afrotherian family Tenrecidae endemic to Madagascar. Tenrecs are wildly diverse; as a result of convergent evolution some resemble hedgehogs, shrews, opossums, rats, and mice. They occupy aquatic, a ...
. First described in 2007, it is most similar to the smaller ''
Microgale brevicaudata
The short-tailed shrew tenrec (''Microgale brevicaudata'') is a species of mammal in the family Tenrecidae. It is endemic to Madagascar. Its natural habitats are subtropical and tropical dry
Dry or dryness most often refers to:
* Lack of r ...
'' of northern and western Madagascar. ''M. macpheei'' has a broad rostrum (front part of the skull) and, like ''M. brevicaudata'', lacks a
diastema
A diastema (plural diastemata, from Greek διάστημα, space) 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. More colloquially, the condition ...
(gap) between the
premolar
The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...
s. A number of details of tooth morphology are characteristic of ''M. macpheei''.
Taxonomy
Remains of
shrew tenrec
''Microgale'' is a genus of mammal in the family Tenrecidae. There are 21 living species on the island of Madagascar and one extinct species known from a fossil. Some species have been discovered in the last twenty years.
On the basis of molec ...
s (''Microgale'') were found during expeditions to the cave of Andrahomana in southeastern Madagascar, led by David Burney in 2000 and 2003.Goodman et al., 2007, p. 368 The ''Microgale'' material was described as a new species, ''M. macpheei'', in 2007 by Steven Goodman, Natalie Vasey, and Burney.Goodman et al., 2007, p. 370 The species was named after Ross MacPhee in honor of his contributions to knowledge of the genus ''Microgale'' and the paleontology of Madagascar.Goodman et al., 2007, p. 371 Goodman and colleagues considered the living ''
Microgale brevicaudata
The short-tailed shrew tenrec (''Microgale brevicaudata'') is a species of mammal in the family Tenrecidae. It is endemic to Madagascar. Its natural habitats are subtropical and tropical dry
Dry or dryness most often refers to:
* Lack of r ...
'' from northern and western Madagascar to be the closest relative of ''M. macpheei'';Goodman et al., 2007, p. 373 some populations of this tenrec have since been separated into a different species, '' M. grandidieri''.Olson et al., 2009, p. 1095 The
common name
In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contra ...
"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
A tenrec is any species of mammal within the afrotherian family Tenrecidae endemic to Madagascar. Tenrecs are wildly diverse; as a result of convergent evolution some resemble hedgehogs, shrews, opossums, rats, and mice. They occupy aquatic, a ...
family, which includes a variety of other Malagasy mammals.
Description
''Microgale macpheei'' is known from two specimens: a damaged
cranium
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, ...
(skull without
mandible
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...
s, or lower jaws) lacking the back part (the
parietal bone
The parietal bones () are two bones in the skull which, when joined at a fibrous joint, form the sides and roof of the cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named ...
s and further back) as well as the
incisor
Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, w ...
s,
canines
Canine may refer to:
Zoology and anatomy
* a dog-like Canid animal in the subfamily Caninae
** ''Canis'', a genus including dogs, wolves, coyotes, and jackals
** Dog, the domestic dog
* Canine tooth, in mammalian oral anatomy
People with the surn ...
, and second
premolar
The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...
s; and another damaged cranium lacking the same parts as well as the left toothrow. Both show no evidence of ongoing
tooth replacement Tooth loss is a process in which one or more teeth come loose and fall out. Tooth loss is normal for deciduous teeth (baby teeth), when they are replaced by a person's adult teeth. Otherwise, losing teeth is undesirable and is the result of injur ...
, indicating that the
permanent dentition
Permanent teeth or adult teeth are the second set of teeth formed in diphyodont mammals. In humans and old world simians, there are thirty-two permanent teeth, consisting of six maxillary and six mandibular molars, four maxillary and four mandibul ...
is complete.Goodman et al., 2007, pp. 370–371 ''M. macpheei'' was larger in most measurements than ''M. brevicaudata'', but because of small samples, some differences are not
statistically significant
In statistical hypothesis testing, a result has statistical significance when it is very unlikely to have occurred given the null hypothesis (simply by chance alone). More precisely, a study's defined significance level, denoted by \alpha, is the p ...
. The length of the bony
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 s ...
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''.Goodman et al., 2007, table 1
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
A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two tooth, teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molar (tooth), molars. More colloq ...
) 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
The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...
are reduced relative to the condition in other ''Microgale''. ''M. macpheei'' lacks an extension of the
protocone
A cusp is a pointed, projecting, or elevated feature. In animals, it is usually used to refer to raised points on the crowns of teeth.
The concept is also used with regard to the leaflets of the four heart valves. The mitral valve, which has two ...
cusp on the lingual (inner) side of the third upper premolar (P3) and P4, present in ''M. brevicaudata'', and has the
paracone
A paracone is a 1960s atmospheric reentry or spaceflight mission abort concept using an inflatable ballistic cone.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 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 ...
'', suggests formerly more
mesic
Mesic may refer to:
* Mesic, North Carolina, a town in the United States
* Mesic habitat, a type of habitat
See also
*Mesić (disambiguation)
*Mešić Mešić is a Bosnian surname, a patronymic derived from the masculine given name '' Meša'', it ...
(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
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
material, but none are currently recognized as valid species; thus, ''M. macpheei'' is at present the only known
recent
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...
ly 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 (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.
The method was de ...
has been carried out on ''M. macpheei'' remains, bones of the rodent ''
Macrotarsomys petteri
Petter's big-footed mouse (''Macrotarsomys petteri''), is a Madagascan rodent in the genus '' Macrotarsomys''. With a head and body length of 150 mm (5.9 in) and body mass of 105 g (3.7 oz), it is the largest species of its ge ...
'' 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 (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becaus ...