Drymoreomys
Encyclopedia
Drymoreomys is a genus
of rodent
s in the tribe Oryzomyini
, from the Atlantic Forest of Brazil. The single species, D. albimaculatus, is known only from the states of São Paulo
and Santa Catarina
and was not named until 2011. It lives in the humid forest on the eastern slopes of the Serra do Mar
and perhaps reproduces year-round. Although its range is relatively large and includes some protected area
s, it is patchy and threatened, and the discoverers recommend that the animal be considered "Near Threatened
" on the IUCN Red List
. Within Oryzomyini, Drymoreomys appears to be most closely related to Eremoryzomys from the Andes
of Peru, a biogeographically
unusual relationship.
With a body mass of 44–64 g (1.6–2.3 oz), Drymoreomys is a medium-sized rodent with long fur that is orange to reddish-buff
above and grayish with several white patches below. The pads on the hindfeet are very well developed and there is brown fur on the upper sides of the feet. The tail is brown above and below. The front part of the skull is relatively long and the ridges on the braincase are weak. The palate
is short, with its back margin between the third molars
. Several traits of the genitals are not seen in any other oryzomyine.
. The animal was not, however, formally described until 2011, when Alexandre Percequillo and colleagues named it as a new genus and species within the tribe Oryzomyini
: Drymoreomys albimaculatus. The generic name, Drymoreomys, combines the Greek δρυμός (drymus), meaning "forest", Latin oreo, meaning "mountain", and Greek μῦς (mys), meaning "mouse". The name refers to the animal's occurrence in mountain forest. The specific name, albimaculatus, derives from the Latin albus, meaning "white", and maculatus, meaning "spotted", a reference to the spots of white in the animal's fur. Percequillo and colleagues found little geographic variation among samples of Drymoreomys, although a few traits differ in frequency between populations from the states of São Paulo and Santa Catarina
.
According to a phylogenetic
analysis of evidence from morphology, the nuclear
gene IRBP
, and the mitochondrial
gene cytochrome b
, Drymoreomys is most closely related to Eremoryzomys polius, an oryzomyine from northern Peru and the only species in the genus Eremoryzomys. Together, Drymoreomys and Eremoryzomys are part of clade D, one of four main clade
s within Oryzomyini. Oryzomyini includes well over a hundred species distributed mainly in South America, including nearby islands such as the Galápagos Islands
and some of the Antilles
. It is one of several tribes recognized within the subfamily Sigmodontinae
, which encompasses hundreds of species found across South America and into southern North America. Sigmodontinae is the largest subfamily of the family Cricetidae
, other members of which include vole
s, lemming
s, hamster
s, and deermice
, all mainly from Eurasia and North America.
. In the closely related Eremoryzomys, the upperparts are grayish. The hairs of the underfur, which are 12 to 14 mm (0.5 to 0.6 in) long, are grayish for most of their length and orange or brown at the tip. In the overfur, the cover hairs (which form the main body of the fur), are 14 to 17 mm (0.6 to 0.7 in) long and brown at the tip, with an orange band below the tip, and the longer, sparse guard hair
s are red to dark brown in the half closest to the tip and are 17 to 21 mm (0.7 to 0.8 in) long. The sides are reddish brown. On the underparts, the hairs are grayish at the base and white at the tip, except on the throat, chest, and (in some specimens) groin, where the hairs are entirely white—a trait unique among the oryzomyines. In overall appearance, the underparts are grayish, with white spots where the hairs are completely white.
The small, rounded ears are covered with dense golden hairs on the outer and with reddish brown hairs on the inner surface. The mystacial vibrissae (whiskers on the upper lip) are long, usually extending a little beyond the ears when laid back against the head, but the superciliary vibrissae (whiskers above the eyes) are short and do not extend beyond the ears. The upper surface on the forefeet is covered with brown fur, and there is white or silvery fur on the digits
. Ungual tuft
s (fur around the bases of the claws) are present on the second through fourth digits. On the short, fairly broad hindfeet, the upper side is covered densely with silvery to white hairs near the tips of the feet and toes, and with brown fur otherwise. No other oryzomyine has such brown fur on its hindfeet. The second through fourth digits have long silvery-white ungual tufts, but those on the first digit are short. On the sole, the pads are very large. Among oryzomyines, only Oecomys
and the extinct Megalomys
have similarly large pads between their digits. There is a dense cover of short brown hairs on both the upper and lower sides of the tail. Unlike in Eremoryzomys, the tail is the same color above and below.
and premaxilla
ry bones extend in front of the incisor
s, forming a rostral tube, which is shared among oryzomyines only with Handleyomys
. The zygomatic notch (a notch formed by a projection at the front of the zygomatic plate
, a bony plate at the side of the skull) is shallow. The interorbital region
(between the eyes) is narrow and long, with the narrowest part towards the front. The crests on the braincase and interorbital region are weakly developed. Eremoryzomys has larger crests on its interorbital region.
The incisive foramina (openings in the front part of the palate
) are long, sometimes extending to between the first molars
(M1). The bony palate is broad and short, with the posterior margin between the third molars (M3). Nephelomys levipes is the only other oryzomyine with such a short palate, although that of Eremoryzomys polius is only slightly longer. The posterolateral palatal pits
(openings in the back part of the palate near the M3) vary from small to fairly large and are located in slight fossas
(depressions). In Eremoryzomys, these fossas are deeper. The roof of the mesopterygoid fossa, the opening behind the palate, is completely closed or contains small sphenopalatine vacuities
. The vacuities are much larger in Eremoryzomys. The alisphenoid strut
, a piece of bone that separates two foramina (openings), is present in all Drymoreomys specimens examined, except in one juvenile specimen.
The mandible
(lower jaw) is long and low. The coronoid process
, the frontmost of the three main processes
(projections) at the back of the jawbone, is large and about as high as the condyloid process
behind it. The angular process, below the condyloid, is fairly short and does not extend further backwards than the condyloid. There is no noticeable capsular process
(a raising at the back of the jaw that houses the root of the lower incisor).
. The upper molar rows are either almost parallel or slightly convergent with each other toward the front. Holochilus
and Lundomys are the only other oryzomyines with non-parallel molar rows. The valleys between the cusps
of the upper molars extending from the inner and outer sides overlap slightly across the midlines of the teeth. The molars are high-cusped, almost hypsodont
. On M1, the anterocone (the front cusp) is divided into two cuspules on the lingual (inner, towards the tongue) and labial (outer, towards the lips) sides of the teeth. The mesoloph, a crest near the middle of the labial side of the tooth, is long and well developed on each of the three upper molars. On the lower molars (m1 to m3), the cusps on the labial side are located slightly in front of their lingual counterparts. The anteroconid, the front cusp on the m1, is divided in two. The m1, m2, and usually m3 have a mesolophid, a crest corresponding to the mesoloph but located on the lingual side. Each of the lower molars has two roots.
(penis bone). There is only one spine on the papilla (nipple-like projection) on the upper side of the penis. On the urethral process, located in the crater at the end of the penis, a fleshy process at the side, the lateral lobule, is present. The preputial gland
s (glands in front of the genitals) are large. The lack of lateral bacular mounds, presence of a lateral lobule, and size of the preputial glands are all unique traits among the oryzomyines.
in the Brazilian states of São Paulo and Santa Catarina, at 650 to 1200 m (2100 to 3900 ft) above sea level. It has not been found in the intervening state of Paraná
, but is likely to occur there. The biogeographical
pattern indicated by the relationship between Drymoreomys and the Andean Eremoryzomys is unusual. While there are some similar cases of relationships between Andean and Atlantic Forest animals, these involve inhabitants of humid forests in the Andes; Eremoryzomys, by contrast, lives in an arid area.
Drymoreomys appears to be a specialist of dense, moist, montane and premontane forest. It has been found in disturbed and secondary forest
s as well as in pristine forest, but probably needs contiguous forest to survive. Reproductive activity has been observed in females in June, November, and December and in males in December, suggesting that the species breeds year-round. Although some of its morphological traits, such as the very large pads, are suggestive of arboreal (tree-dwelling) habits, most specimens were collected in pitfall trap
s on the ground.
s, but it has only been found in seven localities and its habitat is threatened by deforestation and fragmentation. Therefore, Percequillo and colleagues suggest that the species be assessed as "Near Threatened
" under the IUCN Red List
criteria.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s in the tribe Oryzomyini
Oryzomyini
Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of family Cricetidae. It includes about 120 species in about thirty genera, distributed from the eastern United States to the southernmost parts of South America, including many offshore islands...
, from the Atlantic Forest of Brazil. The single species, D. albimaculatus, is known only from the states of São Paulo
São Paulo (state)
São Paulo is a state in Brazil. It is the major industrial and economic powerhouse of the Brazilian economy. Named after Saint Paul, São Paulo has the largest population, industrial complex, and economic production in the country. It is the richest state in Brazil...
and Santa Catarina
Santa Catarina (state)
Santa Catarina is a state in southern Brazil with one of the highest standards of living in Latin America. Its capital is Florianópolis, which mostly lies on the Santa Catarina Island. Neighbouring states are Rio Grande do Sul to the south and Paraná to the north. It is bounded on the east by...
and was not named until 2011. It lives in the humid forest on the eastern slopes of the Serra do Mar
Serra do Mar
Serra do Mar is a 1,500 km long system of mountain ranges and escarpments in Southeastern Brazil, which runs in parallel to the Atlantic Ocean coast from the state of Espírito Santo to southern Santa Catarina, although some include Serra Geral in the Serra do Mar, in which case this range...
and perhaps reproduces year-round. Although its range is relatively large and includes some protected area
Protected area
Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...
s, it is patchy and threatened, and the discoverers recommend that the animal be considered "Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
" on the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
. Within Oryzomyini, Drymoreomys appears to be most closely related to Eremoryzomys from the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
of Peru, a biogeographically
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
unusual relationship.
With a body mass of 44–64 g (1.6–2.3 oz), Drymoreomys is a medium-sized rodent with long fur that is orange to reddish-buff
Buff (colour)
Buff is a pale yellow-brown colour that got its name from the colour of buff leather.Displayed on the right is the colour buff.EtymologyAccording to the Oxford English Dictionary, buff as a descriptor of a colour was first used in the London Gazette of 1686, describing a uniform to be "A Red Coat...
above and grayish with several white patches below. The pads on the hindfeet are very well developed and there is brown fur on the upper sides of the feet. The tail is brown above and below. The front part of the skull is relatively long and the ridges on the braincase are weak. The 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...
is short, with its back margin between the third 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"....
. Several traits of the genitals are not seen in any other oryzomyine.
Taxonomy
Drymoreomys was first recorded in 1992 by Meika Mustrangi in the state of São PauloSão Paulo (state)
São Paulo is a state in Brazil. It is the major industrial and economic powerhouse of the Brazilian economy. Named after Saint Paul, São Paulo has the largest population, industrial complex, and economic production in the country. It is the richest state in Brazil...
. The animal was not, however, formally described until 2011, when Alexandre Percequillo and colleagues named it as a new genus and species within the tribe Oryzomyini
Oryzomyini
Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of family Cricetidae. It includes about 120 species in about thirty genera, distributed from the eastern United States to the southernmost parts of South America, including many offshore islands...
: Drymoreomys albimaculatus. The generic name, Drymoreomys, combines the Greek δρυμός (drymus), meaning "forest", Latin oreo, meaning "mountain", and Greek μῦς (mys), meaning "mouse". The name refers to the animal's occurrence in mountain forest. The specific name, albimaculatus, derives from the Latin albus, meaning "white", and maculatus, meaning "spotted", a reference to the spots of white in the animal's fur. Percequillo and colleagues found little geographic variation among samples of Drymoreomys, although a few traits differ in frequency between populations from the states of São Paulo and Santa Catarina
Santa Catarina (state)
Santa Catarina is a state in southern Brazil with one of the highest standards of living in Latin America. Its capital is Florianópolis, which mostly lies on the Santa Catarina Island. Neighbouring states are Rio Grande do Sul to the south and Paraná to the north. It is bounded on the east by...
.
According to a phylogenetic
Phylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
analysis of evidence from morphology, the nuclear
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...
gene IRBP
RBP3
Retinol-binding protein 3, interstitial , also known as IRBP is a protein that in humans is encoded by the RBP3 gene. RBP3 orthologs have been identified in most eutherians except tenrecs and armadillos.- Function :...
, and the mitochondrial
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
gene cytochrome b
Cytochrome b
Cytochrome b/b6 is the main subunit of transmembrane cytochrome bc1 and b6f complexes. In addition, it commonly refers to a region of mtDNA used for population genetics and phylogenetics.- Function :...
, Drymoreomys is most closely related to Eremoryzomys polius, an oryzomyine from northern Peru and the only species in the genus Eremoryzomys. Together, Drymoreomys and Eremoryzomys are part of clade D, one of four main clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s within Oryzomyini. Oryzomyini includes well over a hundred species distributed mainly in South America, including nearby islands such as the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
and some of the Antilles
Antilles
The Antilles islands form the greater part of the West Indies in the Caribbean Sea. The Antilles are divided into two major groups: the "Greater Antilles" to the north and west, including the larger islands of Cuba, Jamaica, Hispaniola , and Puerto Rico; and the smaller "Lesser Antilles" on the...
. It is one of several tribes recognized within the subfamily Sigmodontinae
Sigmodontinae
The subfamily Sigmodontinae is one of the most diverse groups of mammals. It includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species count...
, which encompasses hundreds of species found across South America and into southern North America. Sigmodontinae is the largest subfamily of the family Cricetidae
Cricetidae
The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...
, other members of which include vole
Vole
A vole is a small rodent resembling a mouse but with a stouter body, a shorter hairy tail, a slightly rounder head, smaller ears and eyes, and differently formed molars . There are approximately 155 species of voles. They are sometimes known as meadow mice or field mice in North America...
s, lemming
Lemming
Lemmings are small rodents, usually found in or near the Arctic, in tundra biomes. They are subniveal animals, and together with voles and muskrats, they make up the subfamily Arvicolinae , which forms part of the largest mammal radiation by far, the superfamily Muroidea, which also includes rats,...
s, hamster
Hamster
Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera....
s, and deermice
Peromyscus
The genus Peromyscus contains the animal species commonly referred to as deer mice. This is a genus of New World mouse only distantly related to the common house mouse and laboratory mouse, Mus musculus...
, all mainly from Eurasia and North America.
External morphology
Drymoreomys albimaculatus is a medium-sized, long-tailed, short-eared, short-footed rodent. It is quite distinct from other oryzomyines and has a number of unique traits. In 11 adults from Parque Natural Municipal Nascentes do Garcia in Santa Catarina, head and body length was 122 to 139 mm (4.8 to 5.5 in), tail length was 140 to 175 mm (5.5 to 6.9 in), hindfoot length was 25.8 to 30.5 mm (1 to 1.2 in), ear length was 16 to 22 mm (0.6 to 0.9 in), and body mass was 44 to 64 g (1.6 to 2.3 oz). The fur is long and dense and consists of thin, short, woolly underfur and long, thick overfur. Overall, the fur of the upperparts is orange to reddish-buffBuff (colour)
Buff is a pale yellow-brown colour that got its name from the colour of buff leather.Displayed on the right is the colour buff.EtymologyAccording to the Oxford English Dictionary, buff as a descriptor of a colour was first used in the London Gazette of 1686, describing a uniform to be "A Red Coat...
. In the closely related Eremoryzomys, the upperparts are grayish. The hairs of the underfur, which are 12 to 14 mm (0.5 to 0.6 in) long, are grayish for most of their length and orange or brown at the tip. In the overfur, the cover hairs (which form the main body of the fur), are 14 to 17 mm (0.6 to 0.7 in) long and brown at the tip, with an orange band below the tip, and the longer, sparse guard hair
Guard hair
Guard hairs are the longest, coarsest hairs in a mammal's coat, forming the topcoat . They taper to a point and protect the undercoat from the elements. They are often water repellent and stick out above the rest of the coat...
s are red to dark brown in the half closest to the tip and are 17 to 21 mm (0.7 to 0.8 in) long. The sides are reddish brown. On the underparts, the hairs are grayish at the base and white at the tip, except on the throat, chest, and (in some specimens) groin, where the hairs are entirely white—a trait unique among the oryzomyines. In overall appearance, the underparts are grayish, with white spots where the hairs are completely white.
The small, rounded ears are covered with dense golden hairs on the outer and with reddish brown hairs on the inner surface. The mystacial vibrissae (whiskers on the upper lip) are long, usually extending a little beyond the ears when laid back against the head, but the superciliary vibrissae (whiskers above the eyes) are short and do not extend beyond the ears. The upper surface on the forefeet is covered with brown fur, and there is white or silvery fur on the digits
Digit (anatomy)
A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates.- Names:Some languages have different names for hand and foot digits ....
. Ungual tuft
Ungual tuft
In mammals, ungual tufts are tufts of hairs at the base of claws of the fore- and hindfeet. Their presence has been used as a character in cladistic studies of Cricetidae....
s (fur around the bases of the claws) are present on the second through fourth digits. On the short, fairly broad hindfeet, the upper side is covered densely with silvery to white hairs near the tips of the feet and toes, and with brown fur otherwise. No other oryzomyine has such brown fur on its hindfeet. The second through fourth digits have long silvery-white ungual tufts, but those on the first digit are short. On the sole, the pads are very large. Among oryzomyines, only Oecomys
Oecomys
Oecomys is a genus of rodent within the tribe Oryzomyini of family Cricetidae. It contains about 17 species, which live in trees and are distributed across forested parts of South America, extending into Panama and Trinidad.-Literature cited:...
and the extinct Megalomys
Megalomys
Megalomys is a genus of rodent in the family Cricetidae, part of the tribe Oryzomyini. The genus contains four large rodents from various Caribbean islands, all of which are now extinct. The last species to survive was M...
have similarly large pads between their digits. There is a dense cover of short brown hairs on both the upper and lower sides of the tail. Unlike in Eremoryzomys, the tail is the same color above and below.
Skull
In the skull, the rostrum (front part) is relatively long. The nasalNasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
and premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
ry bones extend in front of 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, forming a rostral tube, which is shared among oryzomyines only with Handleyomys
Handleyomys
Handleyomys is a genus of Central and South American rodents in the tribe Oryzomyini of family Cricetidae. It was first described in 2002 to include two species from the Colombian Andes which were previously included in distinct and unrelated genera, Aepeomys and Oryzomys, but which turned out to...
. The zygomatic notch (a notch formed by a projection at the front of the zygomatic plate
Zygomatic plate
In rodent anatomy, the zygomatic plate is a bony plate derived from the flattened front part of the zygomatic arch . At the back, it connects to the front root of the zygomatic arch, and at the top it is connected to the rest of the skull via the antorbital bridge. It is part of the maxillary...
, a bony plate at the side of the skull) is shallow. The interorbital region
Interorbital region
The interorbital region of the skull is located between the eyes, anterior to the braincase. The form of the interorbital region may exhibit significant variation between taxonomic groups....
(between the eyes) is narrow and long, with the narrowest part towards the front. The crests on the braincase and interorbital region are weakly developed. Eremoryzomys has larger crests on its interorbital region.
The incisive foramina (openings in the front part of the 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...
) are long, sometimes extending to between the first 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"....
(M1). The bony palate is broad and short, with the posterior margin between the third molars (M3). Nephelomys levipes is the only other oryzomyine with such a short palate, although that of Eremoryzomys polius is only slightly longer. The posterolateral palatal pits
Posterolateral palatal pits
In anatomy, posterolateral palatal pits are gaps at the sides of the back of the bony palate, near the last molars. Posterolateral palatal pits are present, in various degrees of development, in several members of the rodent family Cricetidae...
(openings in the back part of the palate near the M3) vary from small to fairly large and are located in slight fossas
Fossa (anatomy)
In anatomical terminology, fossa has come to mean a depression or hollow, in general, in a bone. Other parts of the body may be involved, for example, the antecubital fossa...
(depressions). In Eremoryzomys, these fossas are deeper. The roof of the mesopterygoid fossa, the opening behind the palate, is completely closed or contains small sphenopalatine vacuities
Sphenopalatine vacuities
In rodents, sphenopalatine vacuities are perforations of the roof of the mesopterygoid fossa, the open space behind the palate, in between the parapterygoid fossae. They may perforate the presphenoid or basisphenoid bone...
. The vacuities are much larger in Eremoryzomys. The alisphenoid strut
Alisphenoid strut
In some rodents, the alisphenoid strut is an extension of the alisphenoid bone that separates two foramina in the skull, the masticatory–buccinator foramen and the foramen ovale accessorius...
, a piece of bone that separates two foramina (openings), is present in all Drymoreomys specimens examined, except in one juvenile specimen.
The mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
(lower jaw) is long and low. The coronoid process
Coronoid process of the mandible
The mandible's coronoid process is a thin, triangular eminence, which is flattened from side to side and varies in shape and size....
, the frontmost of the three main processes
Process (anatomy)
In anatomy, a process is a projection or outgrowth of tissue from a larger body. The vertebra has several kinds of processes,such as: transverse process, prezygapophysis, postzygapophysis.-Examples:Examples of processes include:...
(projections) at the back of the jawbone, is large and about as high as the condyloid process
Condyloid process
The condyloid process is part of the mandible and is thicker than the coronoid, and consists of two portions: the condyle, and the constricted portion which supports it, the neck.-Condyle :...
behind it. The angular process, below the condyloid, is fairly short and does not extend further backwards than the condyloid. There is no noticeable capsular process
Capsular process
In rodents, the capsular process or projection is a bony capsule that contains the root of the lower incisor. It is visible on the labial side of the mandible as a raising in the bone...
(a raising at the back of the jaw that houses the root of the lower incisor).
Dentition
The upper incisors are opisthodont (with the cutting surface oriented backwards) and have orange to yellow enamelTooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
. The upper molar rows are either almost parallel or slightly convergent with each other toward the front. Holochilus
Holochilus
Holochilus is a genus of semiaquatic rodents in the tribe Oryzomyini of family Cricetidae, sometimes called marsh rats. It contains three living species, Holochilus brasiliensis, Holochilus chacarius, and Holochilus sciureus, which are widely distributed in South America east of the Andes, and a...
and Lundomys are the only other oryzomyines with non-parallel molar rows. The valleys between the cusps
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...
of the upper molars extending from the inner and outer sides overlap slightly across the midlines of the teeth. The molars are high-cusped, almost hypsodont
Hypsodont
Hypsodont dentition is characterized by high-crowned teeth and enamel which extends past the gum line. This provides extra material for wear and tear. Some examples of animals with hypsodont dentition are cows, horses and deer; all animals that feed on gritty, fibrous material. The opposite...
. On M1, the anterocone (the front cusp) is divided into two cuspules on the lingual (inner, towards the tongue) and labial (outer, towards the lips) sides of the teeth. The mesoloph, a crest near the middle of the labial side of the tooth, is long and well developed on each of the three upper molars. On the lower molars (m1 to m3), the cusps on the labial side are located slightly in front of their lingual counterparts. The anteroconid, the front cusp on the m1, is divided in two. The m1, m2, and usually m3 have a mesolophid, a crest corresponding to the mesoloph but located on the lingual side. Each of the lower molars has two roots.
Other anatomy
There are 12 ribs and 19 thoracicolumbar (chest and abdomen), four sacral, and 36 to 38 caudal (tail) vertebrae. There are three digits at the tip of the penis, of which the central one is the largest. The two lateral digits are not supported by mounds of the baculumBaculum
The baculum is a bone found in the penis of most mammals. It is absent in humans, but present in other primates, such as the gorilla and chimpanzee.The bone aids in sexual intercourse.-Purpose:...
(penis bone). There is only one spine on the papilla (nipple-like projection) on the upper side of the penis. On the urethral process, located in the crater at the end of the penis, a fleshy process at the side, the lateral lobule, is present. The preputial gland
Preputial gland
Preputial glands are exocrine glands that are located in front of the genitals of some mammals and produce pheromones. The preputial glands of female animals are sometimes called clitoral glands....
s (glands in front of the genitals) are large. The lack of lateral bacular mounds, presence of a lateral lobule, and size of the preputial glands are all unique traits among the oryzomyines.
Distribution and ecology
Drymoreomys albimaculatus occurs in the Atlantic Forest on the eastern slopes of the Serra do MarSerra do Mar
Serra do Mar is a 1,500 km long system of mountain ranges and escarpments in Southeastern Brazil, which runs in parallel to the Atlantic Ocean coast from the state of Espírito Santo to southern Santa Catarina, although some include Serra Geral in the Serra do Mar, in which case this range...
in the Brazilian states of São Paulo and Santa Catarina, at 650 to 1200 m (2100 to 3900 ft) above sea level. It has not been found in the intervening state of Paraná
Paraná (state)
Paraná is one of the states of Brazil, located in the South of the country, bordered on the north by São Paulo state, on the east by the Atlantic Ocean, on the south by Santa Catarina state and the Misiones Province of Argentina, and on the west by Mato Grosso do Sul and the republic of Paraguay,...
, but is likely to occur there. The biogeographical
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
pattern indicated by the relationship between Drymoreomys and the Andean Eremoryzomys is unusual. While there are some similar cases of relationships between Andean and Atlantic Forest animals, these involve inhabitants of humid forests in the Andes; Eremoryzomys, by contrast, lives in an arid area.
Drymoreomys appears to be a specialist of dense, moist, montane and premontane forest. It has been found in disturbed and secondary forest
Secondary forest
A secondary forest is a forest or woodland area which has re-grown after a major disturbance such as fire, insect infestation, timber harvest or windthrow, until a long enough period has passed so that the effects of the disturbance are no longer evident...
s as well as in pristine forest, but probably needs contiguous forest to survive. Reproductive activity has been observed in females in June, November, and December and in males in December, suggesting that the species breeds year-round. Although some of its morphological traits, such as the very large pads, are suggestive of arboreal (tree-dwelling) habits, most specimens were collected in pitfall trap
Pitfall trap
A pitfall trap is a trapping pit for small animals, such as insects, amphibians and reptiles. Pitfall traps are mainly used for ecology studies and ecologic pest control. Animals that enter a pitfall trap are unable to escape, and may either be killed by the trap or remain unharmed...
s on the ground.
Conservation status
The range of Drymoreomys albimaculatus is relatively large and it occurs in several protected areaProtected area
Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...
s, but it has only been found in seven localities and its habitat is threatened by deforestation and fragmentation. Therefore, Percequillo and colleagues suggest that the species be assessed as "Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
" under the IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
criteria.